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• Roberta Heale 1 ,
• Alison Twycross 2
• 1 School of Nursing , Laurentian University , Sudbury , Ontario , Canada
• 2 School of Health and Social Care , London South Bank University , London , UK
• Correspondence to Dr Roberta Heale, School of Nursing, Laurentian University, Sudbury, ON P3E2C6, Canada; rheale{at}laurentian.ca

http://dx.doi.org/10.1136/eb-2017-102845

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What is it?

Case study is a research methodology, typically seen in social and life sciences. There is no one definition of case study research. 1 However, very simply… ‘a case study can be defined as an intensive study about a person, a group of people or a unit, which is aimed to generalize over several units’. 1 A case study has also been described as an intensive, systematic investigation of a single individual, group, community or some other unit in which the researcher examines in-depth data relating to several variables. 2

Often there are several similar cases to consider such as educational or social service programmes that are delivered from a number of locations. Although similar, they are complex and have unique features. In these circumstances, the evaluation of several, similar cases will provide a better answer to a research question than if only one case is examined, hence the multiple-case study. Stake asserts that the cases are grouped and viewed as one entity, called the quintain . 6  ‘We study what is similar and different about the cases to understand the quintain better’. 6

The steps when using case study methodology are the same as for other types of research. 6 The first step is defining the single case or identifying a group of similar cases that can then be incorporated into a multiple-case study. A search to determine what is known about the case(s) is typically conducted. This may include a review of the literature, grey literature, media, reports and more, which serves to establish a basic understanding of the cases and informs the development of research questions. Data in case studies are often, but not exclusively, qualitative in nature. In multiple-case studies, analysis within cases and across cases is conducted. Themes arise from the analyses and assertions about the cases as a whole, or the quintain, emerge. 6

Benefits and limitations of case studies

If a researcher wants to study a specific phenomenon arising from a particular entity, then a single-case study is warranted and will allow for a in-depth understanding of the single phenomenon and, as discussed above, would involve collecting several different types of data. This is illustrated in example 1 below.

Using a multiple-case research study allows for a more in-depth understanding of the cases as a unit, through comparison of similarities and differences of the individual cases embedded within the quintain. Evidence arising from multiple-case studies is often stronger and more reliable than from single-case research. Multiple-case studies allow for more comprehensive exploration of research questions and theory development. 6

Despite the advantages of case studies, there are limitations. The sheer volume of data is difficult to organise and data analysis and integration strategies need to be carefully thought through. There is also sometimes a temptation to veer away from the research focus. 2 Reporting of findings from multiple-case research studies is also challenging at times, 1 particularly in relation to the word limits for some journal papers.

Examples of case studies

Example 1: nurses’ paediatric pain management practices.

One of the authors of this paper (AT) has used a case study approach to explore nurses’ paediatric pain management practices. This involved collecting several datasets:

Observational data to gain a picture about actual pain management practices.

Questionnaire data about nurses’ knowledge about paediatric pain management practices and how well they felt they managed pain in children.

Questionnaire data about how critical nurses perceived pain management tasks to be.

These datasets were analysed separately and then compared 7–9 and demonstrated that nurses’ level of theoretical did not impact on the quality of their pain management practices. 7 Nor did individual nurse’s perceptions of how critical a task was effect the likelihood of them carrying out this task in practice. 8 There was also a difference in self-reported and observed practices 9 ; actual (observed) practices did not confirm to best practice guidelines, whereas self-reported practices tended to.

Example 2: quality of care for complex patients at Nurse Practitioner-Led Clinics (NPLCs)

The other author of this paper (RH) has conducted a multiple-case study to determine the quality of care for patients with complex clinical presentations in NPLCs in Ontario, Canada. 10 Five NPLCs served as individual cases that, together, represented the quatrain. Three types of data were collected including:

Review of documentation related to the NPLC model (media, annual reports, research articles, grey literature and regulatory legislation).

Interviews with nurse practitioners (NPs) practising at the five NPLCs to determine their perceptions of the impact of the NPLC model on the quality of care provided to patients with multimorbidity.

Chart audits conducted at the five NPLCs to determine the extent to which evidence-based guidelines were followed for patients with diabetes and at least one other chronic condition.

The three sources of data collected from the five NPLCs were analysed and themes arose related to the quality of care for complex patients at NPLCs. The multiple-case study confirmed that nurse practitioners are the primary care providers at the NPLCs, and this positively impacts the quality of care for patients with multimorbidity. Healthcare policy, such as lack of an increase in salary for NPs for 10 years, has resulted in issues in recruitment and retention of NPs at NPLCs. This, along with insufficient resources in the communities where NPLCs are located and high patient vulnerability at NPLCs, have a negative impact on the quality of care. 10

These examples illustrate how collecting data about a single case or multiple cases helps us to better understand the phenomenon in question. Case study methodology serves to provide a framework for evaluation and analysis of complex issues. It shines a light on the holistic nature of nursing practice and offers a perspective that informs improved patient care.

• Gustafsson J
• Calanzaro M
• Sandelowski M

Competing interests None declared.

Provenance and peer review Commissioned; internally peer reviewed.

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A young researcher's guide to writing a clinical case report

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Key takeaways:

• A clinical case report or case study is a type of academic publication where medical practitioners share patient cases that are unusual or haven’t been described before.
• Acquiring patient consent and maintaining patient anonymity are essential aspects of writing a clinical case report.
• Case reports follow a standard structure and format different from that of original research articles.
• Only certain journals publish clinical case reports.

What is a clinical case report?

Clinical case reports have been the earliest form of medical communication. A clinical case report or case study is a means of disseminating new knowledge gained from clinical practice. Medical practitioners often come across patient cases that are different or unusual such as a previously unknown condition, a complication of a known disease, an unusual side effect or adverse response to a mode of treatment, or a new approach to a common medical condition. Thus, a clinical case report is expected to discuss the signs, symptoms, diagnosis, and treatment of a disease.

Clinical case reports are the first-line evidence in medical literature as they present original observations and can be an excellent way for medical students and practitioners to get started with academic writing. Additionally, a published case report is definitely a contribution to medical science and a great addition to a CV.

How to find a suitable case?

As a medical student or practitioner, you must keep an eye out for interesting or unusual cases. However, it might be difficult to identify which case would be worth writing about. According to Charles Young, Editor-in-chief of the journal Clinical Case Reports , a good case report is considered to be one that has a clear message, can be generalized, and is relevant to many other clinicians .

According to the University of Texas Health Science Center , most journals publish case reports that deal with one or more of the following:

1. Unusual observations

2. Adverse response to therapies

3. Unusual combination of conditions leading to confusion

4. Illustration of a new theory

5. Question regarding a current theory

6. Personal impact

Patient consent: an ethical requirement for case studies

Informed consent in an ethical requirement for most studies involving humans. It is important to take written consent from the patient before you start writing your case report as all journals will require you to provide patient consent at the time of manuscript submission. In case the patient is a minor, parental consent is required.  For adults who are unable to consent to investigation or treatment, consent of closest family members is required.

Patient anonymity is also an important requirement. Remember not to disclose any information that might reveal the identity of the patient. You need to be particularly careful with pictures, and ensure that pictures of the affected area do not reveal the identity of the patient .

How is a clinical case report structured?

Different journals may have slightly different formats for case reports, and it is advisable to select a few target journals and read some of their case reports to get a general idea of the sequence and format.

However, in general, all case reports include the following components: an abstract, an introduction, a case, and a discussion. Some journals might also require you to include a literature review.

Abstract: The abstract should summarize the case, the problem it addresses, and the message it conveys. Abstracts of case studies are usually very short, preferably not more than 150 words.

Introduction: The introduction gives a brief overview of the problem that the case addresses, citing relevant literature where necessary. The introduction generally ends with a single sentence describing the patient and the basic condition that he or she is suffering from.

Case: This section provides the details of the case in the following order:

• Patient description
• Case history
• Physical examination results
• Results of pathological tests and other investigations
• Treatment plan
• Expected outcome of the treatment plan
• Actual outcome

The author should ensure that all the relevant details are included and unnecessary ones excluded.

Discussion: This is the most important part of the case report; the part that will convince the journal that the case is publication worthy. This section should start by expanding on what has been said in the introduction, focussing on why the case is noteworthy and the problem that it addresses.

This is followed by a summary of the existing literature on the topic. (If the journal specifies a separate section on literature review, it should be added before the Discussion).  This part describes the existing theories and research findings on the key issue in the patient’s condition. The review should narrow down to the source of confusion or the main challenge in the case.

Finally, the case report should be connected to the existing literature, mentioning the message that the case conveys. The author should explain whether this corroborates with or detracts from current beliefs about the problem and how this evidence can add value to future clinical practice.

Conclusion: A case report ends with a conclusion or with summary points, depending on the journal’s specified format. This section should briefly give readers the key points covered in the case report. Here, the author can give suggestions and recommendations to clinicians, teachers, or researchers. Some journals do not want a separate section for the conclusion: it can then be the concluding paragraph of the Discussion section.

Where to publish a case study?

Publishing a case report is not easy, as some journals are reluctant to publish them. However, there are several new online journals that are dedicated to publishing case studies.  BMJ Case Reports ,   Cases Journal , the  Journal of Medical Case Reports ,  and Radiology Case Reports are some notable journals publishing case studies.

Case studies are a vehicle for doctors around the world to share their experiences with handling challenging patient cases. These can be valuable sources of information and guidance for clinical practitioners when faced with puzzling or challenging conditions in patients they attend to.

If you have any doubts or questions, you can post them in the comments section below. Alternatively, you can also post a question on our Q&A forum , if you are facing a problem and need expert publication advice. 

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• What Is a Case Study? | Definition, Examples & Methods

What Is a Case Study? | Definition, Examples & Methods

Published on May 8, 2019 by Shona McCombes . Revised on June 22, 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organization, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyze the case, other interesting articles.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

TipIf your research is more practical in nature and aims to simultaneously investigate an issue as you solve it, consider conducting action research instead.

Unlike quantitative or experimental research , a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

Example of an outlying case studyIn the 1960s the town of Roseto, Pennsylvania was discovered to have extremely low rates of heart disease compared to the US average. It became an important case study for understanding previously neglected causes of heart disease.

However, you can also choose a more common or representative case to exemplify a particular category, experience or phenomenon.

Example of a representative case studyIn the 1920s, two sociologists used Muncie, Indiana as a case study of a typical American city that supposedly exemplified the changing culture of the US at the time.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews , observations , and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data.

Example of a mixed methods case studyFor a case study of a wind farm development in a rural area, you could collect quantitative data on employment rates and business revenue, collect qualitative data on local people’s perceptions and experiences, and analyze local and national media coverage of the development.

The aim is to gain as thorough an understanding as possible of the case and its context.

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In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis , with separate sections or chapters for the methods , results and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyze its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

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• Case Study | Definition, Examples & Methods

Case Study | Definition, Examples & Methods

Published on 5 May 2022 by Shona McCombes . Revised on 30 January 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organisation, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating, and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyse the case.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

Prevent plagiarism, run a free check.

Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

Unlike quantitative or experimental research, a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

If you find yourself aiming to simultaneously investigate and solve an issue, consider conducting action research . As its name suggests, action research conducts research and takes action at the same time, and is highly iterative and flexible. 

However, you can also choose a more common or representative case to exemplify a particular category, experience, or phenomenon.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews, observations, and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data .

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis, with separate sections or chapters for the methods , results , and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyse its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

McCombes, S. (2023, January 30). Case Study | Definition, Examples & Methods. Scribbr. Retrieved 30 October 2023, from https://www.scribbr.co.uk/research-methods/case-studies/

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Other students also liked, correlational research | guide, design & examples, a quick guide to experimental design | 5 steps & examples, descriptive research design | definition, methods & examples.

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Since NIH does not require IRB approval of a protocol and informed consent documents at the time an application is submitted, applicants should consult their institution’s IRB before writing and applying to help answer whether your imaging research proposal is a clinical trial involving non-exempt human subjects. Most requirements for protecting human subjects are codified in the law, 45 CFR Part 46.

Mechanistic Clinical Trials: A clinical trial designed to understand a biological or behavioral process, the pathophysiology of a disease, or the mechanism of action of an intervention (e.g., trials that study the mechanisms or pathways by which the treatment produces its effect). The NIH gave examples of mechanistic studies that likely qualify as clinical trials in the October 25, 2017 Guide notice . Below are imaging-specific examples that experimentally manipulates the biological environment to understand relationships and characterize the pathophysiology of a disease:

(1) NCT01562223: Studying Repeated Magnetic Resonance Imaging (MRI) using Dynamic-Contrast Enhanced (DCE-MRI) and Diffusion-Weighted Imaging (DW-MRI) in Patients Diagnosed with Prostate Cancer

This mechanistic imaging study is designed to assess the use of novel MRI contrast methods for prostate cancer diagnosis. Participants with a recent diagnosis of adenocarcinoma of the prostate will undergo successive DCE-MRI and DWI-MRI examinations. The purpose is to establish the relationship between tumor aggressiveness and novel biomarkers for angiogenesis identified on DCE-MRI and changes in cellular density identified on DWI-MRI. The establishment of these noninvasive imaging tools for characterization of tumor presence, growth, and aggressiveness may help improve the clinicians’ ability to stage and treat the disease.

(2) NCT03412630: Computed Tomography Perfusion Imaging in Predicting Outcomes in Patients with Ovarian, Fallopian Tube, or Primary Peritoneal Cancer Receiving Bevacizumab

This mechanistic study will evaluate changes in tumor blood flow and its relationship to progression free survival in the primary and recurrent ovarian cancer setting. This study seeks to establish perfusion CT as a non-invasive biomarker for early response to bevacizumab combination chemotherapy for ovarian, fallopian tube and peritoneal carcinoma. Perfusion CT is being evaluated for its ability to accurately assess changes in tumor angiogenesis. This will allow the identification of candidates unlikely to incur benefit from bevacizumab early during initial therapy thus predicting long-term efficacy.

(3) NCT02796729: CEST- Glucose Enhanced MRI for Metastatic Brain Tumors

This mechanistic study compares the ability of two advance MR methods to detect metastatic brain tumors. Participants on study will undergo the Chemical Exchange Saturation Transfer MRI procedure first and then receive an injection of Gd-DTPA for gadolinium-enhanced MRI. Project aims at exploring the relationship MRI relaxation caused by CESTAUC maps will be generated over time and maximum instantaneous tumor contrast calculated using before and after contrast injection MR images to determine detectability of small tumor masses.

Note, NCI does not participate in the NIH R01 and R21 Research Project Grants FOAs. Trials of safety, efficacy, and mechanistic exploratory can be supported via NCI’s PAR-18-560 or PAR-18-020 FOAs.

Basic Experimental Studies with Humans (BESH) FOA — Basic science experimental studies involving humans, referred to in NOT-OD-18-212 as “prospective basic science studies involving human participants” include studies that meet the NIH definition of a clinical trial and meet the definition of basic research. Basic research is defined as a “systematic study directed toward greater knowledge or understanding of the fundamental aspects of phenomena and of observable facts without specific applications towards processes or products in mind.” NCI does not participate in the BESH FOAs currently.

Investigator-initiated Interventional Clinical Trials: A study where the intervention(s) being tested is allocated to a group of study subjects to evaluate its effect on a biomedical or health-related outcome and the subjects are followed prospectively. NIH defined interventions include both therapeutic and diagnostic strategies. Below are two imaging-based interventional studies that seek to guide treatment decisions:

(1) NCT01333033: Randomized Phase II Trial of PET Scan-Directed Combined Modality Therapy in Esophageal Cancer

This randomized phase II trial with a cross-over study design investigates the role of FDG PET/CT in assessing response and directing therapy in patients with esophageal cancer receiving different combinations of chemotherapy: a modified FOLFOX-6 therapy or a carboplatin/paclitaxel treatment. PET/CT imaging is repeated during treatment cycles to identify patients that do not respond for crossing over. The results will determine whether changing chemotherapy during pre-operative chemoradiation improves pathologic complete response.

(2) NCT00983697: FDG-PET/CT in Assessing the Tumor and Planning Neck Surgery in Patients with Newly Diagnosed Head & Neck Cancer

The study involves the recruitment of patients with newly diagnosed head and neck squamous cell carcinoma being considered for surgical resection. The participants will undergo a FDG-PET/CT scan prior to surgical resection and the results will be used by surgeons for surgical planning. The study will collect data on how the inclusion of the PET/CT results impact the determination of extent of disease, disease characterization and prognosis, and compares with the surgical plan originally devised from clinical nodal assessment and CT and/or MRI results.

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• Published: November 2006

Case Studies: why are they important?

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Nature Clinical Practice Cardiovascular Medicine is a journal designed to lighten the reading load for busy doctors; why, then, does it include Case Studies? Isn't the case study just a bit of light reading? It depends on what it is designed to do. So, what is the role of the Case Study?

Case Studies should act as instructive examples to people who might encounter similar problems. Ideally, in medicine, Case Studies should detail a particular medical case, describing the background of the patient and any clues the physician picked up (or should have, with hindsight). They should discuss investigations undertaken in order to determine a diagnosis or differentiate between possible diagnoses, and should indicate the course of treatment the patient underwent as a result. As a whole, then, Case Studies should be an informative and useful part of every physician's medical education, both during training and on a continuing basis.

It's debatable whether they always achieve this aim. Many journals publish what are often close to anecdotal reports (if they publish articles on individual cases at all), rather than detailed descriptions of a case; furthermore, the cases described are often esoteric or the conditions present on such an infrequent basis that a physician working outside a teaching-hospital environment would be hard-pressed to apply their new knowledge. It would be difficult, therefore, to say whether any conclusions could confidently be drawn by readers as a result of these reports. Most physicians would probably want to do some extra research—either in the literature or by canvassing opinions of colleagues.

By proposing, peer-reviewing and reading the Case Studies, you and your fellow physicians could gain a broader understanding of clinical diagnoses, treatments and outcomes.

In this light, then, Nature Clinical Practice Cardiovascular Medicine Case Studies have a specific aim: to help established physicians as well as trainees to improve patient care, without adding to their workload. Rather than being merely anecdotal, they include the etiology, diagnosis and management of a case. Importantly, they give an indication of the decision-making process, so that other physicians can apply lateral thinking to their own cases. Decisions on which of a range of treatment options to follow might involve input from the patient, or might be purely objective, but ideally a Case Study should outline why a particular course was followed. Readers should not have to resort to the Internet or to out-of-date textbooks to find basic background information explaining the reasons for approaching the case in that way; the reasons should be fully explained in the article itself.

Nature Clinical Practice Cardiovascular Medicine Case Studies represent an opportunity to spread the benefit of knowledge across the physical boundaries imposed by looking at one case, in one place, at one time. It's not so that fingers can be pointed at 'incorrect' treatment but instead so that geographical differences in practice can be highlighted, for example, or clearer descriptions be reached to explain a case more completely and accurately.

By proposing, peer-reviewing and reading the Case Studies, you and your fellow physicians could gain a broader understanding of clinical diagnoses, treatments and outcomes. So, we're inviting you to contribute to the further education of your colleagues. Will you meet the challenge?

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Solomon, J. Case Studies: why are they important?. Nat Rev Cardiol 3 , 579 (2006). https://doi.org/10.1038/ncpcardio0704

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Issue Date : November 2006

DOI : https://doi.org/10.1038/ncpcardio0704

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What Are Clinical Trials and Studies?

On this page:

What is clinical research?

Why participate in a clinical trial, what happens in a clinical trial or study, what happens when a clinical trial or study ends, what are the different phases of clinical trials, questions to ask before participating in clinical research, how do researchers decide who will participate, clinical research needs participants with diverse backgrounds.

By participating in clinical research, you can help scientists develop new medications and other strategies to treat and prevent disease. Many effective treatments that are used today, such as chemotherapy, cholesterol-lowering drugs, vaccines, and cognitive-behavioral therapy, would not exist without research participants. Whether you’re healthy or have a medical condition, people of all ages and backgrounds can participate in clinical trials. This article can help you learn more about clinical research, why people choose to participate, and how to get involved in a study.

Mr. Jackson's story

Mr. Jackson is 73 years old and was just diagnosed with Alzheimer’s disease . He is worried about how it will affect his daily life. Will he forget to take his medicine? Will he forget his favorite memories, like the births of his children or hiking the Appalachian Trail? When Mr. Jackson talked to his doctor about his concerns, she told him about a clinical trial that is testing a possible new Alzheimer’s treatment. But Mr. Jackson has concerns about clinical trials. He does not want to feel like a lab rat or take the chance of getting a treatment that may not work or could make him feel worse. The doctor explained that there are both risks and benefits to being part of a clinical trial, and she talked with Mr. Jackson about research studies — what they are, how they work, and why they need volunteers. This information helped Mr. Jackson feel better about clinical trials. He plans to learn more about how to participate.

Clinical research is the study of health and illness in people. There are two main types of clinical research: observational studies and clinical trials.

Observational studies monitor people in normal settings. Researchers gather information from people and compare changes over time. For example, researchers may ask a group of older adults about their exercise habits and provide monthly memory tests for a year to learn how physical activity is associated with cognitive health . Observational studies do not test a medical intervention, such as a drug or device, but may help identify new treatments or prevention strategies to test in clinical trials.

Clinical trials are research studies that test a medical, surgical, or behavioral intervention in people. These trials are the primary way that researchers determine if a new form of treatment or prevention, such as a new drug, diet, or medical device (for example, a pacemaker), is safe and effective in people. Often, a clinical trial is designed to learn if a new treatment is more effective or has less harmful side effects than existing treatments.

Other aims of clinical research include:

• Testing ways to diagnose a disease early, sometimes before there are symptoms
• Finding approaches to prevent a health problem, including in people who are healthy but at increased risk of developing a disease
• Improving quality of life for people living with a life-threatening disease or chronic health problem
• Studying the role of caregivers or support groups

Learn more about clinical research from MedlinePlus and ClinicalTrials.gov .

People volunteer for clinical trials and studies for a variety of reasons, including:

• They want to contribute to discovering health information that may help others in the future.
• Participating in research helps them feel like they are playing a more active role in their health.
• The treatments they have tried for their health problem did not work or there is no treatment for their health problem.

Whatever the motivation, when you choose to participate in a clinical trial, you become a partner in scientific discovery. Participating in research can help future generations lead healthier lives. Major medical breakthroughs could not happen without the generosity of clinical trial participants — young and old, healthy, or diagnosed with a disease.

Where can I find a clinical trial?

Looking for clinical trials related to aging and age-related health conditions? Talk to your health care provider and use online resources to:

• Search for a clinical trial
• Look for clinical trials on Alzheimer's, other dementias, and caregiving
• Find a registry for a particular diagnosis or condition
• Explore clinical trials and studies supported by NIA

After you find one or more studies that you are interested in, the next step is for you or your doctor to contact the study research staff and ask questions. You can usually find contact information in the description of the study.

Let your health care provider know if you are thinking about joining a clinical trial. Your provider may want to talk to the research team to make sure the study is safe for you and to help coordinate your care.

Joining a clinical trial is a personal decision with potential benefits and some risks. Learn what happens in a clinical trial and how participant safety is protected . Read and listen to testimonials from people who decided to participate in research.

Here’s what typically happens in a clinical trial or study:

• Research staff explain the trial or study in detail, answer your questions, and gather more information about you.
• Once you agree to participate, you sign an informed consent form indicating your understanding about what to expect as a participant and the various outcomes that could occur.
• You are screened to make sure you qualify for the trial or study.
• If accepted into the trial, you schedule a first visit, which is called the “baseline” visit. The researchers conduct cognitive and/or physical tests during this visit.
• For some trials testing an intervention, you are assigned by chance (randomly) to a treatment group or a control group . The treatment group will get the intervention being tested, and the control group will not.
• You follow the trial procedures and report any issues or concerns to researchers.
• You may visit the research site at regularly scheduled times for new cognitive, physical, or other evaluations and discussions with staff. During these visits, the research team collects data and monitors your safety and well-being.
• You continue to see your regular physician(s) for usual health care throughout the study.

How do researchers decide which interventions are safe to test in people?

Before a clinical trial is designed and launched, scientists perform laboratory tests and often conduct studies in animals to test a potential intervention’s safety and effectiveness. If these studies show favorable results, the U.S. Food and Drug Administration (FDA) approves the intervention to be tested in humans. Learn more about how the safety of clinical trial participants is protected.

Once a clinical trial or study ends, the researchers analyze the data to determine what the findings mean and to plan the next steps. As a participant, you should be provided information before the study starts about how long it will last, whether you will continue receiving the treatment after the trial ends (if applicable), and how the results of the research will be shared. If you have specific questions about what will happen when the trial or study ends, ask the research coordinator or staff.

Clinical trials of drugs and medical devices advance through several phases to test safety, determine effectiveness, and identify any side effects. The FDA typically requires Phase 1, 2, and 3 trials to be conducted to determine if the drug or device can be approved for further use. If researchers find the intervention to be safe and effective after the first three phases, the FDA approves it for clinical use and continues to monitor its effects.

Each phase has a different purpose:

• A Phase 1 trial tests an experimental drug or device on a small group of people (around 20 to 80) to judge its safety, including any side effects, and to test the amount (dosage).
• A Phase 2 trial includes more people (around 100 to 300) to help determine whether a drug is effective. This phase aims to obtain preliminary data on whether the drug or device works in people who have a certain disease or condition. These trials also continue to examine safety, including short-term side effects.
• A Phase 3 trial gathers additional information from several hundred to a few thousand people about safety and effectiveness, studying different populations and different dosages, and comparing the intervention with other drugs or treatment approaches. If the FDA agrees that the trial results support the intervention’s use for a particular health condition, it will approve the experimental drug or device.
• A Phase 4 trial takes place after the FDA approves the drug or device. The treatment’s effectiveness and safety are monitored in large, diverse populations. Sometimes, side effects may not become clear until more people have used the drug or device over a longer period of time.

Clinical trials that test a behavior change, rather than a drug or medical device, advance through similar steps, but behavioral interventions are not regulated by the FDA. Learn more about clinical trials , including the types of trials and the four phases.

Choosing to participate in research is an important personal decision. If you are considering joining a trial or study, get answers to your questions and know your options before you decide. Here are questions you might ask the research team when thinking about participating.

• What is this study trying to find out?
• What treatment or tests will I have? Will they hurt? Will you provide me with the test or lab results?
• What are the chances I will be in the experimental group or the control group?
• If the study tests a treatment, what are the possible risks, side effects, and benefits compared with my current treatment?
• How long will the clinical trial last?
• Where will the study take place? Will I need to stay in the hospital?
• Will you provide a way for me to get to the study site if I need it, such as through a ride-share service?
• Will I need a trial or study partner (for example, a family member or friend who knows me well) to come with me to the research site visits? If so, how long will he or she need to participate?
• Can I participate in any part of the trial with my regular doctor or at a clinic closer to my home?
• How will the study affect my everyday life?
• What steps are being taken to ensure my privacy?
• How will you protect my health while I participate?
• What happens if my health problem gets worse during the trial or study?
• Can I take my regular medicines while participating?
• Who will be in charge of my care while I am in the trial or study? Will I be able to see my own doctors?
• How will you keep my doctor informed about my participation?
• If I withdraw from the trial or study, will this affect my normal care?
• Will it cost me anything to be in the trial or study? If so, will I be reimbursed for expenses, such as travel, parking, lodging, or meals?
• Will my insurance pay for costs not covered by the research, or must I pay out of pocket? If I don’t have insurance, am I still eligible to participate?
• Will my trial or study partner be compensated for his or her time?
• Will you follow up on my health after the end of the trial or study?
• Will I continue receiving the treatment after the trial or study ends?
• Will you tell me the results of the research?
• Whom do I contact if I have questions after the trial or study ends?

To be eligible to participate, you may need to have certain characteristics, called inclusion criteria. For example, a clinical trial may need participants to have a certain stage of disease, version of a gene, or family history. Some trials require that participants have a study partner who can accompany them to clinic visits.

Participants with certain characteristics may not be allowed to participate in some trials. These characteristics are called exclusion criteria. They include factors such as specific health conditions or medications that could interfere with the treatment being tested.

Many volunteers must be screened to find enough people who are eligible for a trial or study. Generally, you can participate in only one clinical trial at a time, although this is not necessarily the case for observational studies. Different trials have different criteria, so being excluded from one trial does not necessarily mean you will be excluded from another.

Researchers need older adults to participate in clinical research so that scientists can learn more about how new drugs, tests, and other interventions will work for them. Many older adults have health needs that are different from those of younger people. For example, as people age, their bodies may react differently to certain drugs. Older adults may need different dosages of a drug to have the intended result. Also, some drugs may have different side effects in older people than in younger individuals. Having older adults enrolled in clinical trials and studies helps researchers get the information they need to develop the right treatments for this age group.

Researchers know that it may be challenging for some older adults to join a clinical trial or study. For example, if you have multiple health problems, can you participate in research that is looking at only one condition? If you are frail or have a disability, will you be strong enough to participate? If you no longer drive, how can you get to the research site? Talk to the research coordinator or staff about your concerns. The research team may have already thought about some of the potential obstacles and have a plan to make it easier for you to participate.

Read more about diversity in clinical trials .

Sign up for email updates on healthy aging

For more information about clinical trials.

Alzheimers.gov www.alzheimers.gov Explore the Alzheimers.gov website for information and resources on Alzheimer’s and related dementias from across the federal government.

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Content reviewed: March 22, 2023

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The Levels of Evidence and their role in Evidence-Based Medicine

Patricia b. burns.

1 Research Associate, Section of Plastic Surgery, Department of Surgery, The University of Michigan Health System

Rod J. Rohrich

2 Professor of Surgery, Department of Plastic Surgery, University of Texas Southwestern Medical Center

Kevin C. Chung

3 Professor of Surgery, Section of Plastic Surgery, Department of Surgery, The University of Michigan Health System

As the name suggests, evidence-based medicine (EBM), is about finding evidence and using that evidence to make clinical decisions. A cornerstone of EBM is the hierarchical system of classifying evidence. This hierarchy is known as the levels of evidence. Physicians are encouraged to find the highest level of evidence to answer clinical questions. Several papers published in Plastic Surgery journals concerning EBM topics have touched on this subject. 1 – 6 Specifically, previous papers have discussed the lack of higher level evidence in PRS and need to improve the evidence published in the journal. Before that can be accomplished, it is important to understand the history behind the levels and how they should be interpreted. This paper will focus on the origin of levels of evidence, their relevance to the EBM movement and the implications for the field of plastic surgery as well as the everyday practice of plastic surgery.

History of Levels of Evidence

The levels of evidence were originally described in a report by the Canadian Task Force on the Periodic Health Examination in 1979. 7 The report’s purpose was to develop recommendations on the periodic health exam and base those recommendations on evidence in the medical literature. The authors developed a system of rating evidence ( Table 1 ) when determining the effectiveness of a particular intervention. The evidence was taken into account when grading recommendations. For example, a Grade A recommendation was given if there was good evidence to support a recommendation that a condition be included in the periodic health exam. The levels of evidence were further described and expanded by Sackett 8 in an article on levels of evidence for antithrombotic agents in 1989 ( Table 2 ). Both systems place randomized controlled trials (RCT) at the highest level and case series or expert opinions at the lowest level. The hierarchies rank studies according to the probability of bias. RCTs are given the highest level because they are designed to be unbiased and have less risk of systematic errors. For example, by randomly allocating subjects to two or more treatment groups, these types of studies also randomize confounding factors that may bias results. A case series or expert opinion is often biased by the author’s experience or opinions and there is no control of confounding factors.

Canadian Task Force on the Periodic Health Examination’s Levels of Evidence *

Levels of Evidence from Sackett *

Modification of levels

Since the introduction of levels of evidence, several other organizations and journals have adopted variation of the classification system. Diverse specialties are often asking different questions and it was recognized that the type and level of evidence needed to be modified accordingly. Research questions are divided into the categories: treatment, prognosis, diagnosis, and economic/decision analysis. For example, Table 3 shows the levels of evidence developed by the American Society of Plastic Surgeons (ASPS) for prognosis 9 and Table 4 shows the levels developed by the Centre for Evidence Based Medicine (CEBM) for treatment. 10 The two tables highlight the types of studies that are appropriate for the question (prognosis versus treatment) and how quality of data is taken into account when assigning a level. For example, RCTs are not appropriate when looking at the prognosis of a disease. The question in this instance is: “What will happen if we do nothing at all”? Because a prognosis question does not involve comparing treatments, the highest evidence would come from a cohort study or a systematic review of cohort studies. The levels of evidence also take into account the quality of the data. For example, in the chart from CEBM, poorly designed RCTs have the same level of evidence as a cohort study.

Levels of Evidence for Prognostic Studies *

Levels of Evidence for Therapeutic Studies *

A grading system that provides strength of recommendations based on evidence has also changed over time. Table 5 shows the Grade Practice Recommendations developed by ASPS. The grading system provides an important component in evidence-based medicine and assists in clinical decision making. For example, a strong recommendation is given when there is level I evidence and consistent evidence from Level II, III and IV studies available. The grading system does not degrade lower level evidence when deciding recommendations if the results are consistent.

Grade Practice Recommendations *

Interpretation of levels

Many journals assign a level to the papers they publish and authors often assign a level when submitting an abstract to conference proceedings. This allows the reader to know the level of evidence of the research but the designated level of evidence does always guarantee the quality of the research. It is important that readers not assume that level 1 evidence is always the best choice or appropriate for the research question. This concept will be very important for all of us to understand as we evolve into the field of EBM in Plastic Surgery. By design, our designated surgical specialty will always have important articles that may have a lower level of evidence due to the level of innovation and technique articles which are needed to move our surgical specialty forward.

Although RCTs are the often assigned the highest level of evidence, not all RCTs are conducted properly and the results should be carefully scrutinized. Sackett 8 stressed the importance of estimating types of errors and the power of studies when interpreting results from RCTs. For example, a poorly conducted RCT may report a negative result due to low power when in fact a real difference exists between treatment groups. Scales such as the Jadad scale have been developed to judge the quality of RCTs. 11 Although physicians may not have the time or inclination to use a scale to assess quality, there are some basic items that should be taken into account. Items used for assessing RCTs include: randomization, blinding, a description of the randomization and blinding process, description of the number of subjects who withdrew or drop out of the study; the confidence intervals around study estimates; and a description of the power analysis. For example, Bhandari et al. 12 published a paper assessing the quality of surgical RCTs. The authors evaluated the quality of RCTs reported in the Journal of Bone and Joint Surgery (JBJS) from 1988–2000. Papers with a score of > 75% were deemed high quality and 60% of the papers had a score < 75%. The authors identified 72 RCTs during this time period and the mean score was 68%. The main reason for the low quality score was lack of appropriate randomization, blinding, and a description of patient exclusion criteria. Another paper found the same quality score of papers in JBJS with a level 1 rating compared to level 2. 13 Therefore, one should not assume that level 1 studies have higher quality than level 2.

A resource for surgeons when appraising levels of evidence are the users’ guides published in the Canadian Journal of Surgery 14 , 15 and the Journal of Bone and Joint Surgery. 16 Similar papers that are not specific to surgery have been published in the Journal of the American Medical Association (JAMA). 17 , 18

Plastic surgery and EBM

The field of plastic surgery has been slow to adopt evidence-based medicine. This was demonstrated in a paper examining the level of evidence of papers published in PRS. 19 The authors assigned levels of evidence to papers published in PRS over a 20 year period. The majority of studies (93% in 1983) were level 4 or 5, which denotes case series and case reports. Although the results are disappointing, there was some improvement over time. By 2003 there were more level 1studies (1.5%) and fewer level 4 and 5 studies (87%). A recent analysis looked at the number of level 1 studies in 5 different plastic surgery journals from 1978–2009. The authors defined level 1 studies as RCTs and meta-analysis and restricted their search to these studies. The number of level 1 studies increased from 1 in 1978 to 32 by 2009. 20 From these results, we see that the field of plastic surgery is improving the level of evidence but still has a way to go, especially in improving the quality of studies published. For example, approximately a third of the studies involved double blinding, but the majority did not randomize subjects, describe the randomization process, or perform a power analysis. Power analysis is another area of concern in plastic surgery. A review of the plastic surgery literature found that the majority of published studies have inadequate power to detect moderate to large differences between treatment groups. 21 No matter what the level of evidence for a study, if it is under powered, the interpretation of results is questionable.

Although the goal is to improve the overall level of evidence in plastic surgery, this does not mean that all lower level evidence should be discarded. Case series and case reports are important for hypothesis generation and can lead to more controlled studies. Additionally, in the face of overwhelming evidence to support a treatment, such as the use of antibiotics for wound infections, there is no need for an RCT.

Clinical examples using levels of evidence

In order to understand how the levels of evidence work and aid the reader in interpreting levels, we provide some examples from the plastic surgery literature. The examples also show the peril of medical decisions based on results from case reports.

An association was hypothesized between lymphoma and silicone breast implants based on case reports. 22 – 27 The level of evidence for case reports, depending on the scale used, is 4 or 5. These case reports were used to generate the hypothesis that a possible association existed. Because of these results, several large retrospective cohort studies from the United States, Canada, Denmark, Sweden and Finland were conducted. 28 – 32 The level of evidence for a retrospective cohort is 2. All of these studies had many years of follow-up for a large number of patients. Some of the studies found an elevated risk and others no risk for lymphoma. None of the studies reached statistical significance. Therefore, higher level evidence from cohort studies does not provide evidence of any risk of lymphoma. Finally, a systematic review was performed that combined the evidence from the retrospective cohorts. 27 The results found an overall standardized incidence ratio of 0.89 (95% CI 0.67–1.18). Because the confidence intervals include 1, the results indicate there is no increased incidence. The level of evidence for the systematic review is 1. Based on the best available evidence, there is no association between lymphoma and silicone implants. This example shows how low level evidence studies were used to generate a hypothesis, which then led to higher level evidence that disproved the hypothesis. This example also demonstrates that RCTs are not feasible for rare events such as cancer and the importance of observational studies for a specific study question. A case-control study is a better option and provides higher evidence for testing the prognosis of the long-term effect of silicone breast implants.

Another example is the injection of epinephrine in fingers. Based on case reports prior to 1950, physicians were advised that epinephrine injection can result in finger ischemia. 33 We see in this example in which level 4 or 5 evidence was accepted as fact and incorporated into medical textbooks and teaching. However, not all physicians accepted this evidence and are performing injections of epinephrine into the fingers with no adverse effects on the hand. Obviously, it was time for higher level evidence to resolve this issue. An in-depth review of the literature from 1880 to 2000 by Denkler, 33 identified 48 cases of digital infarction of which 21 were injected with epinephrine. Further analysis found that the addition of procaine to the epinephrine injection was the cause of the ischemia. 34 The procaine used in these injections included toxic acidic batches that were recalled in 1948. In addition, several cohort studies found no complications from the use of epinephrine in the fingers and hand. 35 , 36 , 37 The results from these cohort studies increased the level of evidence. Based on the best available evidence from these studies, the hypothesis that epinephrine injection will harm fingers was rejected. This example highlights the biases inherent in case reports. It also shows the risk when spurious evidence is handed down and integrated into medical teaching.

Obtaining the best evidence

We have established the need for RCTs to improve evidence in plastic surgery but have also acknowledged the difficulties, particularly with randomization and blinding. Although RCTs may not be appropriate for many surgical questions, well designed and conducted cohort or case-control studies could boost the level of evidence. Many of the current studies tend to be descriptive and lack a control group. The way forward seems clear. Plastic surgery researchers need to consider utilizing a cohort or case-control design whenever an RCT is not possible. If designed properly, the level of evidence for observational studies can approach or surpass those from an RCT. In some instances, observation studies and RCTs have found similar results. 38 If enough cohort or case-control studies become available, this increases the prospect of systematic reviews of these studies that will increase overall evidence levels in plastic surgery.

The levels of evidence are an important component of EBM. Understanding the levels and why they are assigned to publications and abstracts helps the reader to prioritize information. This is not to say that all level 4 evidence should be ignored and all level 1 evidence accepted as fact. The levels of evidence provide a guide and the reader needs to be cautious when interpreting these results.

Acknowledgments

Supported in part by a Midcareer Investigator Award in Patient-Oriented Research (K24 AR053120) from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (to Dr. Kevin C. Chung).

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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NIH's Definition of a Clinical Trial

This page provides information, tools, and resources about the definition of a clinical trial. Correctly identifying whether a study is considered by NIH to be a clinical trial is crucial to how you will:

• Select the right NIH funding opportunity for your research study
• Write the research strategy and human subjects sections of your grant application and contract proposal
• Comply with appropriate policies and regulations, including registration and reporting in ClinicalTrials.gov

Misclassified clinical trial applications may be withdrawn.

In 2016, NIH launched a multi-faceted effort to enhance its stewardship over clinical trials. The goal of this effort is to encourage advances in the design, conduct, and oversight of clinical trials while elevating the entire biomedical research enterprise to a new level of transparency and accountability. The NIH definition of a clinical trial was revised in 2014 in anticipation of these stewardship reforms to ensure a clear and responsive definition of a clinical trial. Learn more about why NIH has made changes to improve clinical trial stewardship.

NIH Definition of a Clinical Trial

A research study in which one or more human subjects are prospectively assigned prospectively assigned The term "prospectively assigned" refers to a pre-defined process (e.g., randomization) specified in an approved protocol that stipulates the assignment of research subjects (individually or in clusters) to one or more arms (e.g., intervention, placebo, or other control) of a clinical trial. to one or more interventions interventions An "intervention" is defined as a manipulation of the subject or subject’s environment for the purpose of modifying one or more health-related biomedical or behavioral processes and/or endpoints. Examples include: drugs/small molecules/compounds; biologics; devices; procedures (e.g., surgical techniques); delivery systems (e.g., telemedicine, face-to-face interviews); strategies to change health-related behavior (e.g., diet, cognitive therapy, exercise, development of new habits); treatment strategies; prevention strategies; and, diagnostic strategies. (which may include placebo or other control) to evaluate the effects of those interventions on health-related biomedical or behavioral outcomes. health-related biomedical or behavioral outcomes. A "health-related biomedical or behavioral outcome" is defined as the pre-specified goal(s) or condition(s) that reflect the effect of one or more interventions on human subjects’ biomedical or behavioral status or quality of life. Examples include: positive or negative changes to physiological or biological parameters (e.g., improvement of lung capacity, gene expression); positive or negative changes to psychological or neurodevelopmental parameters (e.g., mood management intervention for smokers; reading comprehension and /or information retention); positive or negative changes to disease processes; positive or negative changes to health-related behaviors; and, positive or negative changes to quality of life.   

DECISION TOOL

Your human subjects study may meet the NIH definition of a clinical trial.

FIND OUT HERE

Use the following four questions to determine the difference between a clinical study and a clinical trial:

• Does the study involve human participants?
• Are the participants prospectively assigned to an intervention?
• Is the study designed to evaluate the effect of the intervention on the participants?
• Is the effect being evaluated a health-related biomedical or behavioral outcome?

Note that if the answers to the 4 questions are yes, your study meets the NIH definition of a clinical trial, even if…

• You are studying healthy participants
• Your study does not have a comparison group (e.g., placebo or control)
• Your study is only designed to assess the pharmacokinetics, safety, and/or maximum tolerated dose of an investigational drug
• Your study is utilizing a behavioral intervention
• Only one aim or sub-aim of your study meets the clinical trial definition

Studies intended solely to refine measures are not considered clinical trials. Studies that involve secondary research with biological specimens or health information are not clinical trials.

Resources to Clarify the Definition

Case studies.

These simplified case studies illustrate the differences between clinical trials and clinical studies.

These FAQs further clarify the application of the clinical trial definition.

Decision Tree

Print this decision tree for an easy reference for the four questions that identify a clinical trial.

Related Guide Notice

NOT-OD-15-015   Notice of Revised NIH Definition of “Clinical Trial”

This page last updated on: August 8, 2017

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What Is a Case Study?

An in-depth study of one person, group, or event

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Cara Lustik is a fact-checker and copywriter.

Verywell / Colleen Tighe

Benefits and Limitations

Types of case studies, how to write a case study.

A case study is an in-depth study of one person, group, or event. In a case study, nearly every aspect of the subject's life and history is analyzed to seek patterns and causes of behavior. Case studies can be used in various fields, including psychology, medicine, education, anthropology, political science, and social work.

The purpose of a case study is to learn as much as possible about an individual or group so that the information can be generalized to many others. Unfortunately, case studies tend to be highly subjective, and it is sometimes difficult to generalize results to a larger population.

While case studies focus on a single individual or group, they follow a format similar to other types of psychology writing. If you are writing a case study, it is important to follow the rules of APA format .  

A case study can have both strengths and weaknesses. Researchers must consider these pros and cons before deciding if this type of study is appropriate for their needs.

One of the greatest advantages of a case study is that it allows researchers to investigate things that are often difficult to impossible to replicate in a lab. Some other benefits of a case study:

• Allows researchers to collect a great deal of information
• Give researchers the chance to collect information on rare or unusual cases
• Permits researchers to develop hypotheses that can be explored in experimental research

On the negative side, a case study:

• Cannot necessarily be generalized to the larger population
• Cannot demonstrate cause and effect
• May not be scientifically rigorous
• Can lead to bias

Researchers may choose to perform a case study if they are interested in exploring a unique or recently discovered phenomenon. The insights gained from such research can help the researchers develop additional ideas and study questions that might be explored in future studies.

However, it is important to remember that the insights gained from case studies cannot be used to determine cause and effect relationships between variables. However, case studies may be used to develop hypotheses that can then be addressed in experimental research.

Case Study Examples

There have been a number of notable case studies in the history of psychology. Much of  Freud's work and theories were developed through the use of individual case studies. Some great examples of case studies in psychology include:

• Anna O : Anna O. was a pseudonym of a woman named Bertha Pappenheim, a patient of a physician named Josef Breuer. While she was never a patient of Freud's, Freud and Breuer discussed her case extensively. The woman was experiencing symptoms of a condition that was then known as hysteria and found that talking about her problems helped relieve her symptoms. Her case played an important part in the development of talk therapy as an approach to mental health treatment.
• Phineas Gage : Phineas Gage was a railroad employee who experienced a terrible accident in which an explosion sent a metal rod through his skull, damaging important portions of his brain. Gage recovered from his accident but was left with serious changes in both personality and behavior.
• Genie : Genie was a young girl subjected to horrific abuse and isolation. The case study of Genie allowed researchers to study whether language could be taught even after critical periods for language development had been missed. Her case also served as an example of how scientific research may interfere with treatment and lead to further abuse of vulnerable individuals.

Such cases demonstrate how case research can be used to study things that researchers could not replicate in experimental settings. In Genie's case, her horrific abuse had denied her the opportunity to learn language at critical points in her development.

This is clearly not something that researchers could ethically replicate, but conducting a case study on Genie allowed researchers the chance to study phenomena that are otherwise impossible to reproduce.

There are a few different types of case studies that psychologists and other researchers might utilize:

• Collective case studies : These involve studying a group of individuals. Researchers might study a group of people in a certain setting or look at an entire community. For example, psychologists might explore how access to resources in a community has affected the collective mental well-being of those living there.
• Descriptive case studies : These involve starting with a descriptive theory. The subjects are then observed, and the information gathered is compared to the pre-existing theory.
• Explanatory case studies : These   are often used to do causal investigations. In other words, researchers are interested in looking at factors that may have caused certain things to occur.
• Exploratory case studies : These are sometimes used as a prelude to further, more in-depth research. This allows researchers to gather more information before developing their research questions and hypotheses .
• Instrumental case studies : These occur when the individual or group allows researchers to understand more than what is initially obvious to observers.
• Intrinsic case studies : This type of case study is when the researcher has a personal interest in the case. Jean Piaget's observations of his own children are good examples of how an intrinsic cast study can contribute to the development of a psychological theory.

The three main case study types often used are intrinsic, instrumental, and collective. Intrinsic case studies are useful for learning about unique cases. Instrumental case studies help look at an individual to learn more about a broader issue. A collective case study can be useful for looking at several cases simultaneously.

The type of case study that psychology researchers utilize depends on the unique characteristics of the situation as well as the case itself.

There are also different methods that can be used to conduct a case study, including prospective and retrospective case study methods.

Prospective case study methods are those in which an individual or group of people is observed in order to determine outcomes. For example, a group of individuals might be watched over an extended period of time to observe the progression of a particular disease.

Retrospective case study methods involve looking at historical information. For example, researchers might start with an outcome, such as a disease, and then work their way backward to look at information about the individual's life to determine risk factors that may have contributed to the onset of the illness.

Where to Find Data

There are a number of different sources and methods that researchers can use to gather information about an individual or group. Six major sources that have been identified by researchers are:

• Archival records : Census records, survey records, and name lists are examples of archival records.
• Direct observation : This strategy involves observing the subject, often in a natural setting . While an individual observer is sometimes used, it is more common to utilize a group of observers.
• Documents : Letters, newspaper articles, administrative records, etc., are the types of documents often used as sources.
• Interviews : Interviews are one of the most important methods for gathering information in case studies. An interview can involve structured survey questions or more open-ended questions.
• Participant observation : When the researcher serves as a participant in events and observes the actions and outcomes, it is called participant observation.
• Physical artifacts : Tools, objects, instruments, and other artifacts are often observed during a direct observation of the subject.

Section 1: A Case History

This section will have the following structure and content:

Background information : The first section of your paper will present your client's background. Include factors such as age, gender, work, health status, family mental health history, family and social relationships, drug and alcohol history, life difficulties, goals, and coping skills and weaknesses.

Description of the presenting problem : In the next section of your case study, you will describe the problem or symptoms that the client presented with.

Describe any physical, emotional, or sensory symptoms reported by the client. Thoughts, feelings, and perceptions related to the symptoms should also be noted. Any screening or diagnostic assessments that are used should also be described in detail and all scores reported.

Your diagnosis : Provide your diagnosis and give the appropriate Diagnostic and Statistical Manual code. Explain how you reached your diagnosis, how the client's symptoms fit the diagnostic criteria for the disorder(s), or any possible difficulties in reaching a diagnosis.

Section 2: Treatment Plan

This portion of the paper will address the chosen treatment for the condition. This might also include the theoretical basis for the chosen treatment or any other evidence that might exist to support why this approach was chosen.

• Cognitive behavioral approach : Explain how a cognitive behavioral therapist would approach treatment. Offer background information on cognitive behavioral therapy and describe the treatment sessions, client response, and outcome of this type of treatment. Make note of any difficulties or successes encountered by your client during treatment.
• Humanistic approach : Describe a humanistic approach that could be used to treat your client, such as client-centered therapy . Provide information on the type of treatment you chose, the client's reaction to the treatment, and the end result of this approach. Explain why the treatment was successful or unsuccessful.
• Psychoanalytic approach : Describe how a psychoanalytic therapist would view the client's problem. Provide some background on the psychoanalytic approach and cite relevant references. Explain how psychoanalytic therapy would be used to treat the client, how the client would respond to therapy, and the effectiveness of this treatment approach.
• Pharmacological approach : If treatment primarily involves the use of medications, explain which medications were used and why. Provide background on the effectiveness of these medications and how monotherapy may compare with an approach that combines medications with therapy or other treatments.

This section of a case study should also include information about the treatment goals, process, and outcomes.

When you are writing a case study, you should also include a section where you discuss the case study itself, including the strengths and limitiations of the study. You should note how the findings of your case study might support previous research. 

In your discussion section, you should also describe some of the implications of your case study. What ideas or findings might require further exploration? How might researchers go about exploring some of these questions in additional studies?

Here are a few additional pointers to keep in mind when formatting your case study:

• Never refer to the subject of your case study as "the client." Instead, their name or a pseudonym.
• Read examples of case studies to gain an idea about the style and format.
• Remember to use APA format when citing references .

A Word From Verywell

Case studies can be a useful research tool, but they need to be used wisely. In many cases, they are best utilized in situations where conducting an experiment would be difficult or impossible. They are helpful for looking at unique situations and allow researchers to gather a great deal of information about a specific individual or group of people.

If you have been directed to write a case study for a psychology course, be sure to check with your instructor for any specific guidelines that you are required to follow. If you are writing your case study for professional publication, be sure to check with the publisher for their specific guidelines for submitting a case study.

Simply Psychology. Case Study Method .

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach . BMC Med Res Methodol . 2011 Jun 27;11:100. doi:10.1186/1471-2288-11-100

Gagnon, Yves-Chantal.  The Case Study as Research Method: A Practical Handbook . Canada, Chicago Review Press Incorporated DBA Independent Pub Group, 2010.

Yin, Robert K. Case Study Research and Applications: Design and Methods . United States, SAGE Publications, 2017.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

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• Open access
• Published: 27 October 2023

Fully endoscopic microvascular decompression for the treatment of hemifacial spasm, trigeminal neuralgia, and glossopharyngeal neuralgia: a retrospective study

• Weicheng Peng 1 ,
• Rui Zhao 1 ,
• Feng Guan 1 ,
• Xin Liang 1 ,
• Bei Jing 2 ,
• Guangtong Zhu 1 ,
• Beibei Mao 1 &
• Zhiqiang Hu 1 , 2  

BMC Surgery volume  23 , Article number:  331 ( 2023 ) Cite this article

Metrics details

Microvascular decompression (MVD) is already the preferred surgical treatment for medically refractory neurovascular compression syndromes (NVC) such as hemifacial spasm (HFS), trigeminal neuralgia (TN), and glossopharyngeal neuralgia (GPN). Endoscopy has significantly advanced surgery and provides enhanced visualization of MVD. The aim of this study is to analyze the efficacy and safety of fully endoscopic microvascular decompression (E-MVD) for the treatment of HFS, TN, and GPN, as well as to present our initial experience.

Materials and methods

This retrospective case series investigated fully E-MVD performed in 248 patients (123 patients with HFS, 115 patients with TN, and 10 patients with GPN ) from December 2008 to October 2021 at a single institution. The operation duration, clinical outcomes, responsible vessels, intra- and postoperative complications, and recurrences were recorded. Preoperative and immediate postoperative magnetic resonance imaging (MRI) and computerized tomography (CT) were performed for imageological evaluation. The Shorr grading and Barrow Neurological Institute (BNI) pain score were used to evaluate clinical outcomes. The efficacy, safety, and risk factors related to the recurrence of the operation were retrospectively analysed, and the surgical techniques of fully E-MVD were summarised.

A total of 248 patients (103 males) met the inclusion criteria and underwent fully E-MVD were retrospectively studied. The effective rate of 123 patients with HFS was 99.1%, of which 113 cases were completely relieved and 9 cases were significantly relieved. The effective rate of 115 patients with TN was 98.9%, of which 105 cases had completely pain relieved after surgery, 5 cases had significant pain relieved, 4 cases had partial pain relieved but still needed to be controlled by medication. The effective rate of 10 patients with GPN was 100%, 10 cases of GPN were completely relieved after surgery. As for complications, temporary facial numbness occurred in 4 cases, temporary hearing loss in 5 cases, dizziness with frequent nausea and vomiting in 8 cases, headache in 12 cases, and no cerebral hemorrhage, intracranial infection, and other complications occurred. Follow-up ranged from 3 to 42 months, with a mean of 18.6 ± 3.3 months. There were 4 cases of recurrence of HFS and 11 cases of recurrence of TN. The other effective patients had no recurrence or worsening of postoperative symptoms. The cerebellopontine angle (CPA) area ratio (healthy/affected side), the length of disease duration, and the type of responsible vessels are the risk factors related to the recurrence of HFS, TN, and GPN treated by fully E-MVD.

Conclusions

In this retrospective study, our results suggest that the fully E-MVD for the treatment of NVC such as HFS, TN, and GPN, is a safe and effective surgical method. Fully E-MVD for the treatment of NVC has advantages and techniques not available with microscopic MVD, which may reduce the incidence of surgical complications while improving the curative effect and reducing the recurrence rate.

Peer Review reports

Hemifacial spasm (HFS), trigeminal neuralgia (TN), and glossopharyngeal neuralgia (GPN) are the most common neurovascular compression syndromes (NVC) in clinical practice. The symptoms are closely related to patients’ quality of life and often cause pain and discomfort [ 1 , 2 , 3 ].

HFS is one of NVC characterised by intermittent involuntary twitching of muscles innervated by the facial nerve (FN) with an incidence of 1/100,000 [ 4 ]. Typical symptoms of HFS begin with involuntary eyelid blinking and gradually progress to buccal muscle twitching, mouth twitching [ 5 ]. TN is one of NVC manifesting as neuropathic facial pain, defined by the International Pain Society as “sudden, severe and transient periodic tingling of the skin in the area innervated by one or more branches of the trigeminal nerve (TGN)”. Typical clinical features of TN include paroxysmal pain, remission, precipitating factors and trigger points, etc. The annual incidence of TN is 4.5–28.9/100,000, which is more common in middle-aged women, with the right side more common than the left [ 6 ]. GPN is characterised by intermittent, transient, intense and sharp pain in the back of the throat, the base of the tongue, the fossa of the tonsil and the inner ear canal. Sometimes, these episodes of pain can be associated with cardiovascular symptoms, leading to life-threatening episodes of syncope. The annual incidence of GPN is 0.2–0.7/100,000 [ 7 ].

The pathogenesis of the above diseases is still unclear, but it is generally believed that the FN, TGN and glossopharyngeal nerves are compressed by peripheral blood vessels (neurovascular compression), leading to nerve demyelination. At present, microvascular decompression (MVD) is already the preferred surgical treatment for NVC such as HFS, TN, and GPN [ 8 ]. In recent years, with the increasingly mature application of neuroendoscopic surgical techniques in neurosurgery, more and more studies have been reported on the treatment of HFS, TN, and GPN by endoscopy-assisted MVD, but there are few reports on MVD with the full endoscope [ 9 ]. From December 2008 to October 2021, 248 patients with NVC (123 patients with HFS, 115 patients with TN, and 10 patients with GPN) were treated with fully E-MVD in the Department of Neurosurgery, Beijing Shijitan Hospital Affiliated to Capital Medical University, and the clinical therapeutic effect was satisfactory. This study reports on the efficacy and safety of fully E-MVD for the treatment of HFS, TN, and GPN, as well as our surgical experience and skills.

Patient recruitment

This single-centre, retrospective study was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2000. This study was approved by the medical ethics committee of Beijing Shijitan Hospital, Capital Medical University, China. All patients or their legal guardians in this study authorised the release of their medical records and information.

This study included the clinical data of 248 patients with NVC (such as HFS, TN, and GPN) who underwent E-MVD at the Department of Neurosurgery, Beijing Shijitan Hospital, affiliated with Capital Medical University, from December 2008 to October 2021. All eligible patients enrolled in this study met the following criteria: (1) The patient was consistent with the clinical diagnosis of HFS, TN, and GPN; (2) Patients were excluded from secondary HFS, TN, and GPN (such as tumours, arteriovenous malformations compressing nerves, etc.); (3) Patients with multiple sclerosis HFS, TN, and GPN were excluded; (4) The patient had no serious systemic disease and could tolerate anaesthesia and surgery.

The Shorr grading was used to assess clinical outcomes in patients with HFS, while the BNI pain score was used in patients with TN or GPN. According to Shorr grading, grade 0: no spasm; grade I: increased blinking on external stimulation; grade II: mild, facial muscle slight tremor, no dysfunction; grade III: moderate, facial muscle spasm obvious, mild dysfunction; grade IV: severe, severe spasm with small eye cracks and severe dysfunction (inability to walk, read, etc.) [ 10 ]. The criteria used to assess postoperative efficacy for TN and GPN patients is the Barrow Neurological Institute (BNI) pain score, where grade I is complete pain relief, grade II is most pain relief and no need for low-dose medication control, grade III is partial pain relief that can be controlled with medication, grade IV is partial pain relief that cannot be controlled with medication, and grade V is no pain relief [ 11 ].

Imaging data

CT and MRI were performed in all cases prior to E-MVD to exclude patients with HFS, TN and GPN caused by multiple sclerosis and neoplastic lesions. According to the results, the surgeon further clarified the relationship between the patient’s responsible vessels and the corresponding cranial nerves, developed a more reasonable surgical programme and improved the identification rate of the responsible vessels. MRI identified the diagnose of HFS, TN and GPN [Fig.  1 . A, B, E and F]. Immediate postoperative CT and MRI were performed to rule out complications such as cerebral haemorrhage and cerebral contusion.

Surgical procedure

After satisfactory general anaesthesia, all patients were placed in the lateral decubitus position. The post-sigmoid keyhole approach was adopted, and a straight incision of approximately 4 cm was made at the post-mastoid hairline, starting 1 cm above the transverse sinus, and a microbone window craniotomy was performed to create an elliptical bone window with a diameter of 2.0 ~ 3.0 cm [Fig.  1 . I]. TGN decompression was required to expose the junction of the transverse sinus and sigmoid sinus, while facial, glossopharyngeal and vagus nerve decompression was required to expose inferiorly. The dura was cut in a “K” shape and the free edge was suspended and fixed. Sufficient cerebrospinal fluid (CSF) was released during surgery to allow natural collapse of the cerebellar hemispheres. The 30° endoscope was slowly inserted along the side of the cerebellum after covering the cerebellum with brain cotton.

The operator introduced the endoscopic lens into the CPA region along the petrous bone or the junction between the petrous bone and the canopy to first understand the relationship of each nerves and vessels in the visual field and to judge the surgical path. The root entry/exit zone (REZ) of the FN, TGN, glossopharyngeal nerve and vagus nerve were clearly observed and the responsible vessels were explored. The REZ of the FN should be comprehensively observed during FN decompression, while the whole process from the REZ to the Meckel’s sac should be observed during TGN decompression [ 12 ]. The endoscopic view allows the operator to dissect the arachnoid, expose the nerve and vessels, and after dissecting the responsible vessels, completely release the arachnoid around the nerve and blood vessels.

The operator can use the “pre-placed” technique, i.e. using the “lever principle”, pre-place 1–2 small pieces of Teflon cotton at the proximal end of the responsible vessel (the responsible vessel is above) or the nerve (the responsible vessel is below) to lift it appropriately to relieve the pressure at the neurovascular compression point, then place the Teflon cotton at the compression point to release the compression and withdraw the pre-pad after the position is satisfactorily adjusted. In cases where the vertebrobasilar artery is collaterally compressed or is pushing other vessels to compress the nerve, the operator can use the “set up bridge” technique, in which two small cotton pads are placed on either side of the vertebrobasilar collaterals to properly elevate them away from the brainstem, and then Teflon cotton is sequentially placed at the point of contact between the responsible vessel and the nerve to relieve the compression. In the case of a developed petrous bone, the endoscopic lens is inserted from above and the surgical instrument from below, without grinding the petrous bone. Finally, the operator uses the “diving” technique to mimic brain pulsation in the physiological state to check the decompression effect and ensure that the Teflon cotton pad does not move, while keeping the surgical field clean and replacing bloody CSF and air to avoid postoperative adhesions. Before the end of the operation, the operator should observe the operative field in several directions and comprehensively to avoid missing the responsible vessels. Parts of the surgical process are shown in Fig.  1 .

As for responsible veins, We should never consider coagulation or sacrifice of the involved veins, even in sophisticate situations of neurovascular compression. For large veins, like the trunk of the PV, which are frequently seen in parallel, riding, or even twisting compression, the interpose method can occasionally be added to the transpose method, which uses a Teflon cotton sling attached to the petrosal dura and requires the use of medical adhesive. For medium size veins, like the pontotrigeminal veins, which usually manifest as moderate compression, direct interposition of Teflon cotton may be sufficient. Small perforator veins were also not sacrificed, but a small Teflon cotton was inserted. Last but not least, in the extreme situation where sufficient decompression of the responsible veins was not possible, nerve combing of the sensory root of the TGN was performed.

A-D, A case of TN.   (A-B) : Images A and B show the patient’s preoperative 3D FIESTA MRI and 3D-TOF MRA imaging, respectively, with the green arrow pointing to the trigeminal REZ and the red arrow pointing to the responsible vessel, which forms a compression in the REZ of the TGN; (C-D) : Pictures C and D show that the responsible artery (indicated by the red arrow) forms a neurovascular compression from the trigeminal nerve (indicated by the green arrow) REZ to Meckel’s bursa throughout, and that the neurovascular decompression is adequate and definitive with the aid of the endoscope with a Teflon cotton placed under direct vision. E-H, A case of HFS.   (E-F) : Images E and F show the patient’s preoperative 3D FIESTA MRI and 3D-TOF MRA imaging, respectively. The dilated displaced basilar artery (indicated by the red arrow) squeezes the ipsilateral nerve (indicated by the green arrow); (G-H) : Thick basilar artery (indicated by the red arrow) squeezing the REZ of the FN (indicated by the red arrow), with high tension between them and the brainstem. Intraoperatively, the basilar artery is cushioned away from the FN using “pre-placed” technique and “set up bridge” technique to achieve adequate decompression. I, Surgical incision and bone window. The surgical design creates an elliptical microbone window of approximately 2.5 cm in diameter, revealing the junction of the transverse and sigmoid sinuses (indicated by the blue arrow). J-L, A case of TN with venous-type compression. Intraoperatively, the responsible vein (indicated by the blue arrow) was seen to form a compression beneath the TGN (indicated by the green arrow), which was adequately decompressed by the operator using “pre-placed” technique, and the decompression was checked by “diving” technique at the end of the procedure

Discharge and follow-up assessment

This study used outpatient visits, inpatient observation and telephone follow-up for follow-up. Follow-up included short-term and long-term postoperative symptom improvement, medication use, relapse, and other neurological complications.

In this study, the surgical efficacy of HFS patients was evaluated according to preoperative and postoperative Shorr grading. A postoperative Shorr grading of 0 was considered cured, a postoperative Shorr grading decrease of ≥ 1 compared to preoperative was considered effective, and no significant postoperative change was considered ineffective. The criteria used to assess postoperative efficacy for TN and GPN patients is the Barrow Neurological Institute (BNI) pain score. In this study, BNI grade I was considered cured, BNI grade II was considered excellently effective, BNI grade III was considered effective, and BNI grades IV-V were considered ineffective.

Data analysis

All data were analyzed using statistical software (SPSS version 19.0; IBM Corp, Armonk, NY, USA). Continuous variables are presented as mean ± standard deviation. Counts or ranked variables are presented as mean (range, minimum-maximum). Statistical analysis was performed using generalised linear models. The Chi-square test or Fisher’s exact test were used for dichotomous variables.

Demographic and baseline characteristics

A total of 248 patients (103 males) met the inclusion criteria were retrospectively studied. This study included the clinical data of 248 patients with NVC (such as HFS, TN, and GPN) who underwent E-MVD at the Department of Neurosurgery, Beijing Shijitan Hospital, affiliated with Capital Medical University, from December 2008 to October 2021.

There were 123 patients with HFS, including 49 males and 74 females; age ranged from 24 to 78 years, with a mean of 49.5 ± 11.1 years. The disease duration ranged from 0.5 to 7.3 years, with a mean of 3.2 ± 0.1 years. All symptoms were unilateral, including 81 cases on the right side (65.9%) and 42 cases on the left side (34.1%). According to Shorr grading, 12 cases were grade II, 108 cases were grade III, and 3 cases were grade IV.

There were 115 patients with TN, 46 males and 69 females; age ranged from 20 to 82 years, with a mean of 60.0 ± 11.8 years. The disease duration ranged from 1.1 to 8.0 years, with a mean of 3.5 ± 0.5 years. The pain was located on the left side in 52 cases (45.2%) and on the right side in 63 cases (54.8%). The pain involved the V1 branch of the trigeminal nerve in 12 cases (10.4%), the V2 branch in 23 cases (20.0%), the V3 branch in 18 cases (15.7%), both V1 and V2 branches in 19 cases (16.5%), both V2 and V3 branches in 34 cases (29.6%) and both V1, V2 and V3 branches in 9 cases (7.8%).

There were 10 patients with GPN, including 8 males and 2 females, age ranged from 37 to 64 years, with a mean of 54.5 ± 13.0 years. The disease duration ranged from 1.1 to 4.0 years, with a mean of 2.6 ± 0.3 years. All patients had varying degrees of pharyngeal pain, including 2 cases radiating deep into the external auditory canal and 4 cases radiating to the base of the tongue. The demographics and baseline characteristics were showed in Table  1 .

Evaluation of clinical outcomes

All surgeries were successfully performed. The effective rate of 123 patients with HFS was 99.1%, of which 113 cases were completely relieved (including 5 cases of delayed healing) and 9 cases were significantly relieved. 113 patients recovered from preoperative grade II and III to grade 0, 7 patients recovered from grade III to grade I, 2 patients recovered from grade IV to grade II, and 1 patient had no significant relief from grade IV. The effective rate of 115 patients with TN was 98.9%, of which 105 cases had complete postoperative pain relief and reached BNI grade I.5 cases had significant pain relieved, and did not need medication for pain control and reached BNI grade II. 4 cases had partial pain relieved but still needed to be controlled by medication, but the dose was significantly reduced compared with the preoperative dose, reaching BNI grade III. 1 case had no pain relief and was classified as BNI grade IV-V. The effective rate of 10 patients with GPN was 100%, 10 cases of GPN were completely relieved after surgery. The mean operative duration was 111.2土54.3 min and the mean hospital stay was 14.4土4.7 days. The evaluation of clinical outcomes were showed in Table  2 .

Responsible vessel

In 248 patients, responsible vessels were found in 246 patients and local arachnoid thickening was considered in 2 patients.

Responsible vessels were found in 123 patients with HFS. There were 103 cases of simple arterial compression, including 11 cases of superior cerebellar artery, 58 cases of anterior inferior cerebellar artery, 24 cases of posterior inferior cerebellar artery, 4 cases of vertebral artery, and 6 cases of more than two arteries involved.There were 11 cases of arteriovenous compression, of which the superior cerebellar arteries and veins were involved in 6 cases and the anterior inferior and posterior inferior cerebellar arteries and veins were involved in 5 cases. There were 9 cases of simple venous compression, all of which were petrosal vein (PV) and their branches.

In 115 patients with TN, responsible vessels were found in 113 patients and local arachnoid thickening was considered in 2 patients. There were 88 cases of simple arterial compression, including 59 cases of superior cerebellar artery, 10 cases of anterior inferior cerebellar artery, 8 cases of posterior inferior cerebellar artery, 2 cases of basilar artery, 3 cases of vertebral artery, and 6 cases of more than two arteries involved. There were 19 cases of arteriovenous compression, including 12 cases of superior cerebellar arteries and veins, and 7 cases of anterior inferior and posterior inferior cerebellar arteries and veins. There were 6 cases of simple venous compression, all of which were PV and their branches. Arachnoid thickening was found in 2 case without obvious vascular compression.

Responsible vessels were found in 10 patients with GPN, including anterior inferior cerebellar artery in 1 case, posterior inferior cerebellar artery in 6 cases, vertebral artery combined with posterior inferior cerebellar artery in 2 cases, and vein in 1 case.

Petrosal vein (PV) classification

Through the fully E-MVD procedure in 248 patients, we found that the anatomy of the PV in the endoscopic view has its unique characteristics, and we summarized the preliminary clinical practical staging of the PV in the endoscopic view according to the length and tension.

PV in the endoscopic view could be roughly divided into types I ~ III and there were 3 types in total. Type I: length < 5 mm and the tension is high [Fig.  2 . A]; Type II: length between 5 ~ 10 mm and the tension is moderate [Fig.  2 . B]; Type III : length > 10 mm and the tension is low [Fig.  2 . C]. Of the 248 patients in our group, there were 21 patients whose PV was classified as type I, 67 patients as type II and 160 patients as type III.

Complications

Patients experienced temporary facial numbness in 4 cases and temporary hearing loss in 5 cases after surgery, which resolved after nerve nutrition and other treatments. Patients developed dizziness with frequent nausea and vomiting in 8 cases and headache in 12 cases after surgery, which improved after symptomatic treatment during hospitalisation. No patients had complications such as death, stroke, cardiac event, hearing loss, facial paralysis, hemiparesis, CSF leakage, etc. The incidence of surgical and postsurgical complications were showed in Table  3 .

Follow-up information and risk factors for recurrence

Of the 248 patients, the follow-up period ranged from 3 to 42 months, with a mean of 18.6 ± 3.3 months. There were 15 cases of recurrence among the 246 patients who responded to surgery. Of 122 patients with HFS who responded to surgery, 116 patients had complete remission to grade 0, 2 patients were in grade II (grade IV before surgery), and 4 patients had recurrence (grades II and III before surgery, grade 0 after surgery, and grade III during follow-up), with an overall cure rate of 94.3%. For 114 patients with TN who responded to surgery, 98 patients had complete pain relief, 5 patients had most of the pain relief, and 11 patients had recurrence during follow-up, with an overall cure rate of 86.0%. Of 10 patients with GPN who responded to surgery, all patients had complete pain relief, and none had a recurrence or worsening during follow-up, with an overall cure rate of 100%. These variables were statistically significant in patients with different endpoints, including disease duration, type of responsible vessel, and CPA area ratios (healthy/affected side) showed statistically significant differences between different groups (P < 0.05, Table  4 ).

History of MVD for the treatment of HFS, TN, and GPN

In 1932, Dandy first described the relationship between the superior cerebellar artery and the TGN root and speculated that pain might be related, but he did not make any surgical attempts to separate the vessels from the nerves [ 13 ]. In 1959, Gardner performed the first true MVD on a patient with TN and then extended MVD to HFS [ 14 ]. Graf-radford et al. pointed out that by establishing the theory of MVD, MVD has become one of the main treatment methods for TN [ 15 ]. Since 1967, Jannetta has performed a large number of MVDs and achieved good clinical effects [ 16 ]. At the same time, he proposed the concept of MVD and popularised it worldwide. In 1977, Jannetta improved the surgical method based on the original theory, performed microsurgical techniques, and performed MVD with good results [ 17 ]. However, a major drawback of MVD surgery is that about 15% of patients cannot accurately find the responsible vessels compressing the TGN during surgery. At this point, amputation of the TGN root is required. This not only exposes the patient to the various risks of craniotomy, but also suffer complete anesthesia after surgery [ 18 ].

Theoretical basis of fully E-MVD

In recent years, MVD has gradually developed and matured in terms of theoretical basis and surgical techniques, but the detection rate of responsible vessels in microscopic MVD is about 89.0% − 95.0%, the surgical efficiency is 81.0% − 86.0%, and the recurrence rate is 5.0% − 14.0%. The reasons for poor surgical efficacy and high postoperative recurrence rate are mainly intraoperative failure to identify responsible vessels, omission of responsible vessels or inadequate decompression [ 19 , 20 , 21 ]. Most of these missing responsible vessels are located in the REZ or Makler capsule area, or are blocked by the petrosal bone and become the anatomical blind area in microscopic surgery. It is often necessary to grind away the petrosal tubercle and overstretching the cerebellar hemispheres to barely expose the responsible vessels, which increases the incidence of complications [ 22 ].

Gradually, some neurosurgeons have found that endoscopic-assisted microscopic MVD surgery has more advantages in identifying the responsible vessels, so they are performing endoscopic-assisted microscopic MVD surgery for TN. In 2002, Jarrahy first reported the treatment of TN by fully E-MVD [ 23 ]. Subsequently, Kabil, in his retrospective study of 255 patients, reported an intraoperative detection rate of 100.0% of responsible vessels for fully E-MVD for TN, with postoperative and 3-year facial pain relief rates as high as 95.0% and 93.0%, respectively, with more similar reports in recent years [ 19 , 20 , 24 , 25 ]. In the 248 patients treated with fully E-MVD in this study, the responsible vessel detection rate was 99.2% (246/248), the surgical efficiency was 99.2% (246/248), and the recurrence rate was 6.1% (15/246).

The advantage of fully E-MVD for treatment of HFS,TN, and GPN

(1) The endoscope provides excellent visualization and comprehensive evaluation of the neurovascular compressions in HFS, TN, and GPN patients [ 26 ]. The fully E-MVD procedure allows the operator to have a panoramic view of the CPA area, and by adjusting the depth and angle of the lens, the operative field is revealed completely and clearly, avoiding the blind spots of traditional microscopy. The majority of patients in this group had a single responsible vessel compression, with approximately 17.7% (44/248) having more than two responsible vessels, which further suggests that avoiding missing responsible vessels is necessary to reduce the recurrence rate. In 22.6% (56/248) of our group, the responsible vessel compression was found to be ventral to the corresponding cranial nerve, a location that is often difficult to detect in microscopic MVD. In contrast, endoscopy provides a better view to detect vascular compressions hidden ventral to the corresponding cranial nerve without pulling the brain tissue and nerves. (2) During the fully E-MVD procedure, after the neurovascular compression has been clarified, the operator can pad the Teflon cotton into the ideal position under direct vision, and check whether the ideal position of the Teflon cotton can be achieved, so as to achieve sufficient decompression, consolidate the surgical effect and reduce the recurrence rate. (3) E-MVD utilises the space between the vessels, nerves and surrounding tissues in the CPA without grinding away the petrosal tubercle and overstretching the cerebellar hemispheres, results in less injury and bleeding, reducing the incidence of complications. (4) The “pre-placed” technique used during surgery can effectively prevent accidental injury during sharp neurovascular separation, and it is convenient to adjust the position of the Teflon cotton pad when the operator holds the endoscope in one hand and operates with the other. (5) The “set up bridge” technique can effectively expose the blocked portion of the vertebrobasilar artery and fully decompress the nerve, ensuring that the vertebral or basilar artery does not rebound after decompression, ensuring adequate nerve decompression and reducing the recurrence rate. (6) The “diving” technique, which mimics brain pulsations in a physiological state, checks the decompression effect, ensures that the padded cotton does not move and reduces post-operative recurrence. It also allows intracranial haemorrhage and air to be exchanged, keeping the area clean, reducing complications such as headaches and avoiding post-operative adhesions that lead to recurrence.

Clinical classification of PV

The PV is anatomically closely related to cranial nerves such as the facial, trigeminal, glossopharyngeal and vagus nerves, and is also an important drainage vein of the posterior fossa [ 27 ]. In MVD surgery, the PV often becomes an obstructing vein that prevents exposure of the surgical field and interferes with the surgical procedure [ 28 ]. Therefore, the anatomical location of the PV in the endoscopic view directly interferes with the surgical procedure, thus affecting the surgical effect and even leading to complications due to accidental injury. The PV drains blood to most areas of the brainstem and cerebellum, and accidental dissection of this vein during surgery may result in stroke with serious complications such as cerebellar or brainstem oedema and infarction. In 248 patients who underwent fully E-MVD, we found that the anatomy of the PV in the endoscopic view has its own unique characteristics, and we summarized the preliminary clinical practical staging of the PV in the endoscopic view based on its length and tension. There were a total of 21 patients with type I PV in this group, including 3 patients with PV injury and bleeding. Combined with literature reports and clinical experience, PV burning should be avoided during surgery as much as possible to reduce the incidence of complications. According to the practical clinical staging of PV, if the PV is type I, the operator needs to be more careful during the operation to avoid significant lateral adjustment of the scope to prevent damage to the PV and complications of haemorrhage and bruising stroke.The practicality and scientific validity of the clinical classification of PV we have summarized may need to be supported by more case numbers and further studies.

Recurrence-related factors

With regard to the efficacy of MVD and the risk of long-term recurrence, the literature reports that age, gender and the degree of compression of the responsible vessel are factors that cannot be ignored when assessing the risk of long-term recurrence after surgery [ 29 ]. Some scholars believe that patients over 60 years of age have better long-term efficacy, which may be related to brain atrophy and the relatively large posterior fossa space in older patients [ 30 ]. It has been reported that female patients have a higher postoperative recurrence rate due to the small volume of the posterior fossa and the higher probability of vaso-nerve contact in CPA [ 31 , 32 ]. The size of the CPA is a diagnostic aid for HFS, TN and GPN, and is an important factor in the outcome of MVD after surgery, as well as an influential factor in surgical intervention [ 33 , 34 ]. In our present analysis of clinical data, we found that patients with a smaller ratio of CPA area on the affected side to CPA area on the healthy side were more likely to have recurrence after surgery. We speculated that the main reason for this was that the reduced CPA area resulted in more opportunities for neurovascular contact in this area, increasing the difficulty of performing fully E-MVD [Fig.  2 . D-I]. Patients with a short disease duration may have relatively good results after fully E-MVD. Long-term nerve compression is prone to irreversible nerve damage. Even if the neurovascular compression is relieved by surgery, the clinical symptoms are often not easy to recover. The recurrence rate was lower when the artery was the responsible vessel. The recurrence rate is higher when the venous or arteriovenous compression is the responsible vessel. Simple arterial compression is often easier to identify intraoperatively, allowing for more adequate decompression. Venous compression is easily ignored and omitted, affecting the effect of intraoperative decompression and leading to postoperative recurrence. Similar to our previous studies, it is believed that the CPA area ratio (healthy/affected side), the length of disease duration, and the type of responsible vessels are the risk factors related to the recurrence of HFS, TN, and GPN treated by fully E-MVD. [ 35 ] Therefore, it is of great importance to fully understand the medical history and review the imaging before surgery to assess the patient’s condition and make surgical plans.

A-C, Clinical classification of PV (indicated by the blue arrow).   (A) Type I: length < 5 mm and the tension is high; (B) Type II: length between 5 ~ 10 mm and the tension is moderate; (C) Type III : length > 10 mm and the tension is low. D-F , Preoperative 3D FIESTA MRI of patients with recurrent TN. (D) Area values of the CPA area bilaterally, the area of the CPA on the left side is larger than that on the right side, the area ratio of the CPA (healthy/afflicted side) = 1.67/0.91 = 1.84 > 1; (E) Length values of the TGN bilaterally, it can be seen that the length of the TGN on the left side is longer than that on the right side, the length ratio of the TGN (healthy/afflicted side) = 0.82/0.45 = 1.82 < 1; (F) TGN angle values, it can be seen that the angle of the left side is larger than that of the right side, the angle ratio of TGN (healthy/afflicted side) = 51.8/42.4 = 1.22 < 1. G-I , Intraoperative endoscopic images of the patient with recurrence. (G) The overall area of the CPA is narrower in the endoscopic field of view, which makes endoscopic manipulation difficult; (H) The responsible vessels are visible, forming obvious compression on the TGN, and the green arrow indicates severe deformation of the TGN due to long-term vascular compression; (I) The red arrow indicates simultaneous arterial and venous compression of the TGN

Study Limitations

The design of the present study was retrospective and nonblinded, which has some limitations. The retrospective study in a single center with limited sample size restricts the strength of the data or conclusion. Selection bias largely deviates this study’s generalizability. The patient sample represented the practice of a single neurosurgeon at a tertiary referral center and therefore may lack generalizability to other practice settings. Follow-up intervals were not standardized. A better study design would have required telephone calls at serial time points after surgery, for example at yearly intervals. Further studies are needed to investigate the efficacy and safety of fully EVD for the treatment of HFS, TN and GPN.

Data Availability

The data analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

• Microvascular decompression

Endoscopic microvascular decompression

Neurovascular compression syndromes

• Hemifacial spasm

Facial nerve

• Trigeminal neuralgia

Trigeminal nerve

• Glossopharyngeal neuralgia

Magnetic resonance imaging

Computerized tomography

Cerebellopontine angle

Root entry/exit zone

Barrow Neurological Institute

Petrosal vein

Cerebrospinal fluid

Szmyd B, Sołek J, Błaszczyk M, Jankowski J, Liberski PP, Jaskólski DJ, Wysiadecki G, Karuga FF, Gabryelska A, Sochal M, Tubbs RS, Radek M. The underlying pathogenesis of Neurovascular Compression Syndromes: a systematic review. Front Mol Neurosci. 2022;15:923089. https://doi.org/10.3389/fnmol.2022.923089 . PMID: 35860499; PMCID: PMC9289473.

Article   CAS   PubMed   PubMed Central   Google Scholar  

Shi X, Zhang X, Xu L, Xu Z. Neurovascular compression syndrome:trigeminal neuralgia, hemifacial spasm, vestibular paroxysmia, glossopharyngeal neuralgia, four case reports and review of literature. Clin Neurol Neurosurg. 2022;221:107401. https://doi.org/10.1016/j.clineuro.2022.107401 . Epub 2022 Jul 28. PMID: 35932589.

Article   PubMed   Google Scholar  

Bejjani GK, Sekhar LN. Repositioning of the vertebral artery as treatment for neurovascular compression syndromes. Technical note. J Neurosurg. 1997;86(4):728 – 32. https://doi.org/10.3171/jns.1997.86.4.0728 . PMID: 9120641.

Haller S, Etienne L, Kövari E, Varoquaux AD, Urbach H, Becker M. Imaging of Neurovascular Compression Syndromes: trigeminal neuralgia, Hemifacial Spasm, vestibular paroxysmia, and Glossopharyngeal Neuralgia. AJNR Am J Neuroradiol. 2016;37(8):1384–92. https://doi.org/10.3174/ajnr.A4683 .

Yaltho TC, Jankovic J. The many faces of hemifacial spasm: differential diagnosis of unilateral facial spasms[J]. Mov Disord. 2011;26(9):1582–92. https://doi.org/10.1002/mds.23692 .

Spina A, Mortini P, Alemanno F, Houdayer E, Iannaccone S. Trigeminal neuralgia: toward a Multimodal Approach. World Neurosurg. 2017;103:220–30. https://doi.org/10.1016/j.wneu.2017.03.126 .

Lu VM, Goyal A, Graffeo CS, Perry A, Jonker BP, Link MJ. Glossopharyngeal Neuralgia treatment outcomes after nerve section, microvascular decompression, or stereotactic radiosurgery: a systematic review and Meta-analysis. World Neurosurg. 2018;120:572–82. https://doi.org/10.1016/j.wneu.2018.09.042 .

Szmyd B, Solek J, Blaszczyk M, Jankowski J, Liberski PP, Jaskolski DJ, Wysiadecki G, Karuga FF, Gabryelska A, Sochal M, Tubbs RS, Radek M. The underlying pathogenesis of Neurovascular Compression Syndromes: a systematic review. Front Mol Neurosci. 2022;15:923089. https://doi.org/10.3389/fnmol.2022.923089 .

Yadav YR, Parihar V, Ratre S. World Neurosurg. 2018;114:436–7. https://doi.org/10.1016/j.wneu.2018.03.154 . Endoscopic Microvascular Decompression for Trigeminal Neuralgia: Is It What We Should Aim for?.

Shorr N, Seiff SR, Kopelman J. The use of botulinum toxin in blepharospasm[J]. Am J Ophthalmol. 1985;99(5):542–6. https://doi.org/10.1016/s0002-9394(14)77954-1 .

Article   CAS   PubMed   Google Scholar  

Rogers CL, Shetter AG, Fiedler JA, Smith KA, Han PP, Speiser BL. Gamma knife radiosurgery for trigeminal neuralgia: the initial experience of the Barrow Neurological Institute. Int J Radiat Oncol Biol Phys. 2000;47(4):1013–9. https://doi.org/10.1016/s0360-3016(00)00513-7 .

Hitotsumatsu T, Matsushima T, Inoue T. Microvascular decompression for treatment of trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia: three surgical approach variations: technical note. Neurosurgery. 2003;53(6):1436–41. https://doi.org/10.1227/01.neu.0000093431.43456.3b . discussion 1442-3.

Dandy WE, THE TREATMENT OF TRIGEMINAL NEURALGIA BY, THE CEREBELLAR ROUTE. Ann Surg. 1932;96(4):787–95. https://doi.org/10.1097/00000658-193210000-00026 .

GARDNER W J, MIKLOS MV. Response of trigeminal neuralgia to decompression of sensory root; discussion of cause of trigeminal neuralgia. J Am Med Assoc. 1959;170(15):1773–6. https://doi.org/10.1001/jama.1959.03010150017004 .

Graff-Radford S, Gordon R, Ganal J, Tetradis S. Trigeminal neuralgia and facial pain imaging. Curr Pain Headache Rep. 2015;19(6):19. https://doi.org/10.1007/s11916-015-0495-y .

Jannetta PJ. Arterial compression of the trigeminal nerve at the pons in patients with trigeminal neuralgia. J Neurosurg. 1967;26(1):159–62. https://doi.org/10.3171/jns.1967.26.1part2.0159 .

Article   Google Scholar  

Jannetta PJ. Observations on the etiology of trigeminal neuralgia, hemifacial spasm, acoustic nerve dysfunction and glossopharyngeal neuralgia. Definitive microsurgical treatment and results in 117 patients. Neurochirurgia (Stuttg). 1977;20(5):145–54. https://doi.org/10.1055/s-0028-1090369 .

Tatli M, Satici O, Kanpolat Y, Sindou M. Various surgical modalities for trigeminal neuralgia: literature study of respective long-term outcomes. Acta Neurochir (Wien). 2008;150(3):243–55. https://doi.org/10.1007/s00701-007-1488-3 . Epub 2008 Jan 14.

Li Y, Mao F, Cheng F, Peng C, Guo D, Wang B. A Meta-analysis of endoscopic microvascular decompression versus microscopic microvascular decompression for the treatment for cranial nerve syndrome caused by Vascular Compression. World Neurosurg. 2019;126:647–55. Epub 2019 Feb 15.

Zagzoog N, Attar A, Takroni R, Alotaibi MB, Reddy K. Endoscopic versus open microvascular decompression for trigeminal neuralgia: a systematic review and comparative meta-analysis. J Neurosurg. 2018;1–9. https://doi.org/10.3171/2018.6.JNS172690 .

Lee J, Pierce JT, Sandhu SK, Petrov D, Yang AI. Endoscopic versus microscopic microvascular decompression for trigeminal neuralgia: equivalent pain outcomes with possibly decreased postoperative headache after endoscopic surgery. J Neurosurg. 2017;126(5):1676–84. Epub 2016 Jul 29.

Peng WC, Guan F, Hu ZQ, Huang H, Dai B, Zhu GT, Mao BB, Xiao ZY, Zhang BL, Liang X. [Efficacy analysis of fully endoscopic microvascular decompression in primary trigeminal neuralgia via keyhole approach]. Zhonghua Yi XueZaZhi 2021,101(12):856–60 https://doi.org/10.3760/cma.j.cn112137-20200630-02002 .

Jarrahy R, Cha ST, Eby JB, Berci G, Shahinian HK. Fully endoscopic vascular decompression of the glossopharyngeal nerve. J Craniofac Surg. 2002;13(1):90–5. https://doi.org/10.1097/00001665-200201000-00021 .

Dubey A, Yadav N, Ratre S, Parihar VS, Yadav YR. Full endoscopic vascular decompression in trigeminal neuralgia: experience of 230 patients. World Neurosurg. 2018;113:e612–7. https://doi.org/10.1016/j.wneu.2018.02.108 .

Bohman LE, Pierce J, Stephen JH, Sandhu S, Lee JY. Fully endoscopic microvascular decompression for trigeminal neuralgia: technique review and early outcomes. Neurosurg Focus. 2014;37(4):E18doi. https://doi.org/10.3171/2014.7.FOCUS14318 .

Flanders TM, Blue R, Roberts S, McShane BJ, Wilent B, Tambi V, Petrov D, Lee JYK. Fully endoscopic microvascular decompression for hemifacial spasm. J Neurosurg. 2018;131(3):813–9. https://doi.org/10.3171/2018.4.JNS172631 .

Matsushima K, Matsushima T, Kuga Y, Kodama Y, Inoue K, Ohnishi H, Rhoton AL Jr. Classification of the superior petrosal veins and sinus based on drainage pattern. Neurosurgery. 2014;10 Suppl 2:357–67. https://doi.org/10.1227/NEU.0000000000000323 . discussion 367. PMID: 24561869.

Sattari SA, Shahbandi A, Xu R, Hung A, Feghali J, Yang W, Lee RP, Bettegowda C, Huang J. Sacrifice or preserve the superior petrosal vein in microvascular decompression surgery: a systematic review and meta-analysis. J Neurosurg. 2022;1–9. https://doi.org/10.3171/2022.5.JNS22143 .

Cheng J, Meng J, Liu W, Zhang H, Hui X, Lei D. Nerve atrophy in trigeminal neuralgia due to neurovascular compression and its association with surgical outcomes after microvascular decompression. Acta Neurochir (Wien). 2017;159(9):1699–705. https://doi.org/10.1007/s00701-017-3250-9 .

Bick SK, Huie D, Sneh G, Eskandar EN. Older patients have Better Pain Outcomes following microvascular decompression for trigeminal Neuralgia. Neurosurgery. 2019;84(1):116–22. https://doi.org/10.1093/neuros/nyy011 .

Hardaway FA, Holste K, Ozturk G, Pettersson D, Pollock JM, Burchiel KJ, Raslan AM. Sex-dependent posterior fossa anatomical differences in trigeminal neuralgia patients with and without neurovascular compression: a volumetric MRI age- and sex-matched case-control study. J Neurosurg. 2019;132(2):631–8. https://doi.org/10.3171/2018.9.JNS181768 .

Andersen ASS, Heinskou TB, Rochat P, Springborg JB, Noory N, Smilkov EA, Bendtsen L, Maarbjerg S. Microvascular decompression in trigeminal neuralgia - a prospective study of 115 patients. J Headache Pain. 2022;23(1):145. https://doi.org/10.1186/s10194-022-01520-x . PMID: 36402970; PMCID: PMC9675260.

Kawano Y, Maehara T, Ohno K. Validation and evaluation of the volumetric measurement of cerebellopontine angle cistern as a prognostic factor of microvascular decompression for primary trigeminal neuralgia. Acta Neurochir (Wien). 2014;156(6):1173–9. https://doi.org/10.1007/s00701-014-2064-2 .

Parise M, Acioly MA, Ribeiro CT, Vincent M, Gasparetto EL. The role of the cerebellopontine angle cistern area and trigeminal nerve length in the pathogenesis of trigeminal neuralgia: a prospective case-control study. Acta Neurochir (Wien). 2013;155(5):863–8. https://doi.org/10.1007/s00701-012-1573-0 .

Liang X, Guan F, Hu ZQ, Li B, Li YK, Jing B, Huang H, Zhu GT, Mao BB. [The related factors of postoperative recurrence in trigeminalneuralgia patients undergoing fully neuroendoscopic microvascular decompression]. Zhonghua Yi Xue ZaZhi 2022,102(31):2465–9 https://doi.org/10.3760/cma.j.cn112137-20211218-02820 .

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This work was supported by the National Natural Science Foundation of China (NSFC), No. 82171858 (to ZQH), Capital Characteristic Clinical Application Research of China, No. Z131107002213044 (to ZQH). The funders had no role in study design; data collection, analysis, and interpretation; writing of the paper; or decision to submit the paper for publication.

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ZQ.H and F.G designed this study, performed all the surgeries as the senior surgeon. WC.P wrote and revised the manuscript. GT.Z and BB.M participated in the study design and proof. R.Z, X.L and B.J participated in the statics and artworks. All authors read and approved the final manuscript.

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Peng, W., Zhao, R., Guan, F. et al. Fully endoscopic microvascular decompression for the treatment of hemifacial spasm, trigeminal neuralgia, and glossopharyngeal neuralgia: a retrospective study. BMC Surg 23 , 331 (2023). https://doi.org/10.1186/s12893-023-02214-0

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Educational value of mixed reality combined with a three-dimensional printed model of aortic disease for vascular surgery in the standardized residency training of surgical residents in China: a case control study

• Weihao Li 1   na1 ,
• Yuanfeng Liu 2   na1 ,
• Yonghui Wang 3   na1 ,
• Xuemin Zhang 1 ,
• Kun Liu 1 ,
• Yang Jiao 4 ,
• Xiaoming Zhang 1 ,
• Jie Chen 5 &
• Tao Zhang 1  

BMC Medical Education volume  23 , Article number:  812 ( 2023 ) Cite this article

28 Accesses

Metrics details

The simulated three-dimensional (3D) printed anatomical model of the aorta, which has become the norm in medical education, has poor authenticity, tactility, feasibility, and interactivity. Therefore, this study explored the educational value and effect of mixed reality (MR) combined with a 3D printed model of aortic disease in training surgical residents.

Fifty-one resident physicians who rotated in vascular surgery were selected and divided into traditional (27) and experimental (24) teaching groups using the random number table method. After undergoing the experimental and traditional training routines on aortic disease, both the groups took a theoretical test on aortic disease and an assessment of the simulation based on the Michigan Standard Simulation Experience Scale (MiSSES) template. Their scores and assessment results were compared. The study was conducted at the Department of Vascular Surgery of Peking University People’s Hospital, Beijing, China.

In the theoretical test on aortic disease, the experimental teaching group obtained higher mean total scores (79.0 ± 9.1 vs. 72.6 ± 7.5, P = 0.013) and higher scores in anatomy/ pathophysiology (30.8 ± 5.4 vs. 24.8 ± 5.8; P  < 0.001) than the traditional teaching group. The differences in their scores in the differential diagnosis (25.8 ± 3.0 vs. 23.3 ± 4.9; P = 0.078) and treatment (22.5 ± 11.8 vs. 24.5 ± 8.2; P = 0.603) sessions were insignificant. The MR-assisted teaching stratified the vascular residents through the MiSSES survey. Overall, 95.8% residents (23/24) strongly or somewhat agreed that the MR was adequately realistic and the curriculum helped improve the ability to understanding aortic diseases. Further, 91.7% residents (22/24) strongly or somewhat agreed that the MR-assisted teaching was a good training tool for knowledge on aortic diseases. All residents responded with “Good” or “Outstanding” on the overall rating of the MR experience.

Conclusions

MR combined with the 3D printed model helped residents understand and master aortic disease, particularly regarding anatomy and pathophysiology. Additionally, the realistic 3D printing and MR models improved the self-efficacy of residents in studying aortic diseases, thus greatly stimulating their enthusiasm and initiative to study.

Peer Review reports

Aortic diseases include conditions such as chronic aortic aneurysms, acute aortic syndrome (AAS), and congenital aortic abnormalities [ 1 ]. Most thoracic and abdominal aortic aneurysms are caused by degenerative diseases or atherosclerotic lesions, resulting in the dilatation of the aorta. AAS consists of aortic dissection, intramural hematoma, and penetrating atherosclerotic ulcer with similar clinical characteristics. Common congenital abnormalities include the coarctation of the aorta and many arch variants [ 2 ]. Acute events of aortic diseases, such as the rupture of aneurysms, AAS, or massive hemorrhage, are generally fatal, requiring rapid diagnosis and decision-making by vascular surgeons to reduce the extremely poor prognosis [ 3 ]. This renders the teaching of aortic diseases one of the most crucial sections of residency training in vascular surgery.

According to the standardized residency training system in mainland China, as established in 2014, surgical residents are required to complete 33 months of training in different departments of surgical medicine in an accredited program regardless of their surgical specialties. Vascular surgery, generally as a part of general surgery, is assigned one month. Vascular surgery education is aimed at equipping residents with mastery of the diagnoses and treatments of common diseases, such as dissection and aneurysm, arteriosclerosis obliterans, acute arterial ischemia, varicosity, and venous thrombus embolism. Of these, teaching about aortic disease is the focus of our department. Anatomical atlases and universal models, computed tomography (CT) angiography images, bedside physical examination of typical patients, and simple schematic diagrams are mainly employed in the traditional teaching approach. Three-dimensional (3D) desktop-based systems can display the shape of the cardiovascular systems of real patients. Thus, physicians and trainees can better elucidate anatomical abnormalities via 3D desktop-based systems, which compensate for the shortcomings of universal models. However, 3D desktop-based systems has its limitations, including limited visualization and absence of interaction opportunities [ 4 ].

Mixed reality (MR) refers to new visual environments that combine the real and virtual worlds, where physical and digital objects coexist and interact in real time [ 5 ]. Dissimilar to traditional user interfaces, the users of MR are immersed and can interact with 3D models rather than only viewing a screen. A few studies have evaluated the validity of virtual reality, an analogous computer modeling and simulation technology with MR, in medical education. Vuthea Chheang et al. introduced a collaborative virtual reality environment to assist liver surgeons in tumor surgery planning, which allows surgeons to define and adjust virtual resections on patient-specific organ 3D surfaces and 2D image slices, and enables collaborative planning [ 4 ]. Katerina Bogomolova et al. developed a virtual 3D assessment scenario for anatomical education. Students and teachers with HoloLens shared the same stereoscopic 3D augmented reality model for anatomical knowledge assessment with real-time interaction between assessor and examinee [ 6 ]. However, a systematic review drew no conclusive findings on comparing virtual reality to other available study materials regarding communication skills or clinical decision making [ 7 ].

In the era of COVID-19, bedside teaching was greatly hampered. Given the limited bedside teaching opportunities, the vivid explanation of vascular surgical diseases became a particularly difficult problem in clinical teaching. In this context, MR can create an effective virtual teaching scene with the assistance of a headset. However, few experiences about the use of MR technology in vascular surgery teaching have been published. Therefore, we conducted a study to compare the theoretical performance of surgical residents who used MR technology with that of residents exposed to traditional teaching in the context of aortic diseases. The study was conducted in a teaching hospital in China to examine the outcome of MR application.

Participants

The study design was approved by the ethical committee of Peking University People’s Hospital (approval number: 2017PHB155). We obtained written informed consent from the patients involved in the teaching process. The Department of Vascular Surgery, Peking University People’s Hospital undertakes the task of standardized residency training of surgical residents of vascular surgery, as a part of general surgery, for one month. Due to the COVID-19 pandemic, we developed a 3D printed model combined with a MR session for aortic disease training. A total of 24 general surgery residents with limited experience in vascular surgery—which comprised the experimental teaching group—were recruited between July and December 2020 to receive the MR lecture. After their rotation, all the residents took an academic test, as well as an assessment, which was adapted from the Michigan Standard Simulation Experience Scale (MiSSES) template for evaluating simulations [ 8 ]. For comparison, a similar cohort comprising 27 general surgery residents rotating in our department between July and December 2019 was recruited as the traditional teaching group. This teaching group underwent traditional training on aortic diseases employing anatomical atlases and CT angiography images. The selected residents for the study were elective and not offered any incentives; moreover, they were not awarded any grades because of their performances during the rotating session. This case-control study was developed using guidance and explanations from the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

Teaching methods

Cases involving aortic aneurysm or dissection were selected for the lessons, and the teaching duration was four weeks (8 h/week). The traditional teaching group employed anatomical atlases and CT imaging data, as well as auxiliary simple schematics, to acquire anatomical knowledge and understand the characteristics of the great vessels of the chest and abdomen, the morphological characteristics and classification of the aorta, the principle of endovascular interventional surgery, and the crucial parameters that must be measured (the artery tumor size, tumor neck length and diameter, tumor neck angle, iliac artery branch diameter, and length). Based on traditional anatomical atlases, the experimental teaching group combined CT image data and 3D printed models to specifically learn the anatomical characteristics of large blood vessels, the morphological characteristics, and classification of aortic diseases, as well as actually measure the endovascular treatment design on the 3D printed model and a variety of relevant parameters in the implementation process. Additionally, the residents in this group wore a MR all-in-one machine to watch the surgical process (Supplementary Video 1).

MR hologram

All the patients underwent conventional aortic CT angiography, and the scan data were exported in the Digital Imaging and Communications in Medicine (DICOM) format. The first step was to use the 3D reconstruction software (3D Slicer, www.slicer.org ) to annotate the CT images of the human body and generate a 3D model of each organ component in STL format. Then, we imported the 3D model in STL format into the 3D rendering software (Rhino, Robert McNeel & Associates), named the organ components, colored the organ components, and set the material characteristics, to export the FBX format files. Thereafter, we imported the 3D model in FBX format into a cross-platform game engine (Unity3D, Unity Technologies), for interactive programming of the 3D model and published the software installation package for Microsoft HoloLens2. Finally, we used software installation package for HoloLens2 to show the holographic model, and interact with the 3D printing models. The facilitating doctor analyzed and taught using the reconstructed images on the holographic image fusion surgery platform based on the patients’ medical records and 3D printing models, emphasizing the areas and structures of interest (Fig.  1 , Supplementary Figure S1 , and Supplementary Video 2).

Three-dimensionally reconstructed model of a patient with abdominal aortic aneurysm. The 75-year-old male patient underwent surgery to repair an endovascular aortic aneurysm six months ago, and the review examination revealed an endoleak. This model was employed for learning and evaluation. (A) Abdominal aorta and its primary branches (red), inferior vena cava and the iliac vein (navy blue), bones (white). (B) Endoleak was displayed outside the stent graft. (C) Inferior mesenteric artery revealed patency with the Riolan arch, where blood actively flowed into the aneurysm sac outside the stent graft

3D printing

The aortic model in the STL format was acquired, as described above. We employed an open-source 3D printer slicing tool (Cura version_15.04.6, Ultimaker B.V., Netherlands) to transfer the 3D model from an STL format into a printable file (g-code), which was available for the 3D printer. The 3D printed model was created using an Anycubic 4Max Pro printer (Anycubic, Shenzhen, China). The fused deposition modeling (FDM) technique was adopted and polylactic acid (PLA) was utilized as the printing material.

Test and survey design

The residents were subjected to a specialized theory test on aortic diseases after their rotation, which quantified their understanding of aortic surgery. The test was presented as a case analysis, including several questions on anatomy, pathophysiology, differential diagnosis, and treatment. The full score was 100 points, and the proportions of anatomy and pathophysiology, differential diagnosis, and treatment were ~ 40%, 30%, and 30%, respectively. The test scores were not disclosed to the residents and were not affected by the completeness of the training.

MiSSES is a free online template of a unified assessment instrument that was designed to avail a framework for assessment, offering the option of assessing an entire range of domains that are identified through a review of the simulation literature [ 8 ]. We modified the standardized questionnaire of MiSSES for the MR-based teaching method. The adapted scale has been included in the supplemental material (Supplementary file 1). All the residents were required to anonymously complete the adapted MiSSES after their rotations. The collected paper scales were only employed to teach simulation assessment and improve the investigation by the education office of Peking University People’s Hospital.

Statistical analysis

The data were processed employing PASW Statistics for Windows, Version 18 (SPSS Inc., Chicago, IL, USA). The continuous variables (age, test score, etc.) were presented as mean ± standard deviation and compared with the Student t-test or Mann–Whitney U test, which were determined first by the Shapiro–Wilk test for normality. Furthermore, the MiSSES responses were converted from categorical responses into numerical data for statistical analysis. The residents’ responses, that is, “Strongly disagree,” “Somewhat disagree,” “Neutral/Don’t know,” “Somewhat agree,” and “Strongly agree,” were identified as Scores 1–5 in sequence, respectively. The Cronbach’s alpha value was calculated in aspects to evaluate the reliability of the survey. The categorical variables (gender, answers to closed questions, etc.) were presented as numbers (percentages) and compared with the chi-square test or Fisher exact test, as appropriate. A two-tailed test wherein the level of statistical significance was set at a p-value of < 0.05 was employed for all the statistical analyses.

A total of 24 residents (14 men and 10 women) aged 23.8 ± 1.0 years completed the 3D printed model combined with the MR all-in-one teaching process. They comprised 10 freshmen in standardized surgical training, 6 residents in the second-year of training, and 8 residents in the final-year of training. All the residents completed MiSSES with a minimum of one answer other than “Don’t know.” A similar demographic characteristic was applied to the traditional teaching group comprising 27 residents who were subjected to traditional teaching (Table  1 ).

The mean test scores of the experimental and traditional teaching groups were 79.0 ± 9.1 and 72.6 ± 7.5, respectively. The experimental teaching group outperformed the traditional one in the specialized theory test on aortic diseases after their rotations ( P  = 0.013). The experimental teaching group also scored higher in the anatomy and pathophysiology sessions compared to their traditional counterpart (30.8 ± 5.4 vs. 24.8 ± 5.8; P  < 0.001), while the differences in their scores in the differential diagnosis (25.8 ± 3.0 vs. 23.3 ± 4.9; P  = 0.078) and treatment (22.5 ± 11.8 vs. 24.5 ± 8.2; P  = 0.603) sessions were insignificant (Table  1 ).

The Cronbach’s alpha value for Self-Efficacy, Fidelity, Educational value, and Teaching quality in MiSSES survey was 0.815, 0.760, 0.702, and 0.698, respectively. The experimental teaching group returned “Neutral” to “Strongly Agree” responses in all the components of the MiSSES survey (Fig.  2 , Supplementary Table S1 ). However, 95.8% residents (23/24) strongly or somewhat agreed that the MR was adequately realistic and it helped improve the ability to understanding aortic diseases. Further, 91.7% residents (22/24) strongly or somewhat agreed that the MR-assisted teaching was a good training tool for knowledge in aortic diseases. All residents satisfied the MR experience with 11 and 13 residents rating it as “Outstanding” and “Good” in the overall rating, respectively (Fig.  3 , Supplementary Table S1 ). No resident rated the experience as “Borderline,” “Poor,” or “Neutral/Don’t Know.”

Responses for all the components in the MiSSES survey by the experimental teaching group. All the residents in the experimental teaching group submitted “Neutral” to “Strongly Agree” responses for all the components in the MiSSES survey. More than half of the residents strongly or somewhat agreed that the MR-based lesson with adequately realistic characteristics improves their self-efficacy in learning about aortic diseases. MiSSES, Michigan Standard Simulation Experience Scale; MR, mixed reality

Overall rating from the residents in the experimental teaching group. All the residents responded with “Good” to “Outstanding” on the overall rating of the MR experience, and none rated the experience as “Borderline,” “Poor,” or “Neutral/Don’t Know.” MR, mixed reality

In this study, surgical residents with limited vascular surgery experience demonstrated significantly high satisfaction in all aspects of the MR and 3D printed model-based lessons, achieving outstanding performances in the concluding test. This finding indicated that the MR-based course positively impacted the vascular surgery residency training of the surgical residents. Beyond the satisfaction reflected by the MiSSES survey, a few (6/24) residents acknowledged that the amazing MR-based course inspired them to pursue a specialty in vascular surgery in the future.

The training of residents with surgical career intentions, certainly including vascular surgery, relies heavily on the interpretation of anatomical structures. However, considering the limited anatomical cadaver resources in China, the surgical residents have only had a very limited exposure to anatomy during their clinical training [ 9 ]. Therefore, developing effective modalities for teaching anatomy would be essential for standardized residency training of surgical residents, and the emergence of MR proved as an opportunity for improving students’ knowledge acquisition in clinical medical training by incorporating technology into teaching in the form of computer-generated simulations [ 10 ].

The visualized display of the cardiovascular system in the MR-based courses improved the residents’ recognition of anatomical structures, and this improved their understanding of the pathological and pathophysiological mechanisms of aortic diseases. Furthermore, with the transformation of the orientation of current medical education from framed knowledge structure to problem-based teaching, modern medical education concepts emphasize individualized and patient-centered teaching models. Following this concept, MR technology can effectively record and significantly replicate classic cases to rare clinical situations, expose students to different case studies, and enable them to treat many cases more efficiently and rapidly [ 11 ].

Interactivity is another notable advantage of the MR technology compared with the 3D printed models or pure CT images. The MR technology offers an anatomically correct and immersive visual–spatial environment, which allows a learner to interact three-dimensionally with the aortic anatomy [ 12 ]. The surgical residents controlled the MR system on human body images of the same scales by zooming, focusing, and measuring, as desired, and the teachers also demonstrated aortic diseases in a very intuitive, vivid, and specific manner, which made it easy for the surgical residents to understand and learn the anatomical structure, pathogenesis, diagnosis, and treatment principles of aortic diseases vis a problem-based teaching course. Huettl et al. conducted a study to compare the impact of 3D PDF, 3D printed models, and virtual reality 3D models on anatomical orientation and personal preferences for liver surgeons [ 13 ]. Surgeons named significantly more correct segments in virtual reality or 3D printed models compared to PDF. Remarkably, although tumor assignment was significantly shorter with 3D printed models compared to virtual reality application, virtual reality was the most popular method in liver surgeons for its multiple functions such as scaling and transparency adjustment.

In our study, we found a significant improvement: residents in the experimental teaching group had significantly higher test scores than those in the traditional teaching group in the theoretical knowledge test on aortic disease, and their scores in the anatomy and pathophysiology sessions were significantly higher than those of the traditional teaching group. This indicates that MR-based visualization better enabled residents to understand and master aortic disease, particularly regarding anatomy and pathophysiology. Additionally, the realistic MR-based experience improved the self-efficacy of the residents in mastering aortic diseases, thereby significantly stimulating their enthusiasm and initiative for learning. Concurrently, MR can simulate the process of vascular surgery, and this could greatly stimulate students’ enthusiasm and participation in learning. The application space is not limited to the exchange of basic knowledge and skills; it can also be extended to advanced training and exploration of surgical technology.

Our study also has some limitations. First, currently, MR technology cannot provide real tactile feedback, nor can it achieve medical history communication between medical residents and patients, which are irreplaceable advantages of clinical teaching. Secondly, while the presentation of anatomical structures are more pronounced through MR technology, theoretical knowledge requires the dissemination of traditional knowledge point explanation. Thus, we believe that the experimental teaching group performed better in the anatomical/pathophysiological part of the theoretical test, but there was no significant difference in differential diagnosis and treatment principles. In addition, it must be acknowledged that the application of MR technology not only improves students’ ability to understand and accept, but may also impact the teaching ability of clinical teaching doctors. However, in this study, feedback from clinical instructors on the use of MR technology for teaching was not collected. We could examine this in our next work. Further, our study did not have a randomized controlled design; thus, to further confirm the feasibility of MR technology, additional studies with a randomized design in conjunction with more centers need to be conducted.

We conducted a retrospective controlled study to investigate the value and effect of MR technology combined with the 3D printed model of aortic diseases in residency training education for surgical residents in a teaching hospital in China. Residents who were subjected to MR-based teaching performed well in terms of understanding and mastering aortic diseases, particularly in their understanding of anatomy and pathophysiology. The MR-assisted teaching stratified the vascular residents through the adapted MiSSES survey. We suggest that in the teaching of clinical surgery, especially vascular surgery, more attempts should be made to use techniques such as MR and 3D printing to help students/residents better understand and master complicated surgical diseases.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

three-dimensional

acute aortic syndrome

aortic dissection

Digital Imaging and Communications in Medicine

fused deposition modeling

Michigan Standard Simulation Experience Scale

polylactic acid

stereolithography

mixed reality

Tan GJS, Khoo PLZ, Sailesh MK, Chan KMJ. A review of aortic disease research in Malaysia. Med J Malaysia. 2019;74(1):67–78.

Google Scholar  

Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DE, et al. ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with thoracic aortic disease. A report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for thoracic surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of thoracic Surgeons, and Society for Vascular Medicine. J Am Coll Cardiol. 2010;55:e27–e129.

Article   Google Scholar  

Erbel R, Aboyans V, Boileau C, Bossone E, Bartolomeo RD, Eggebrecht H, et al. ESC Guidelines on the diagnosis and treatment of aortic diseases: document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The task force for the diagnosis and treatment of aortic diseases of the European Society of Cardiology (ESC). Eur Heart J. 2014;35(41):2873–926.

Chheang V, Saalfeld P, Joeres F, Boedecker C, Huber T, Huettl F, et al. A collaborative virtual reality environment for liver surgery planning. Computers & Graphics. 2021;99:234–46.

Milgram P, Kishino F. A taxonomy of mixed reality visual displays. JIToI Syst. 1994;77:1321–9.

Bogomolova K, Sam AH, Misky AT, Gupte CM, Strutton PH, Hurkxkens TJ, et al. Development of a virtual three-dimensional assessment scenario for anatomical education. Anat Sci Educ. 2021;14(3):385–93.

Turso-Finnich T, Jensen RO, Jensen LX, Konge L, Thinggaard E. Virtual reality head-mounted displays in medical education: a systematic review. Simul Healthc. 2023;18(1):42–50.

Seagull FJ, Rooney DM. Filling a void: developing a standard subjective assessment tool for surgical simulation through focused review of current practices. Surgery. 2014;156(3):718–22.

Estai M, Bunt S. Best teaching practices in anatomy education: a critical review. Ann Anat. 2016;208:151–7.

Alharbi Y, Al-Mansour M, Al-Saffar R, Garman A, Alraddadi A. Three-dimensional virtual reality as an innovative teaching and learning tool for human anatomy courses in medical education: a mixed methods study. Cureus. 2020;12(2):e7085.

Alverson DC, Saiki SM Jr, Kalishman S, Lindberg M, Mennin S, Mines J, et al. Medical students learn over distance using virtual reality simulation. Simul Healthc. 2008;3(1):10–5.

Maresky HS, Oikonomou A, Ali I, Ditkofsky N, Pakkal M, Ballyk B. Virtual reality and cardiac anatomy: exploring immersive three-dimensional cardiac imaging, a pilot study in undergraduate medical anatomy education. Clin Anat. 2019;32(2):238–43.

Huettl F, Saalfeld P, Hansen C, Preim B, Poplawski A, Kneist W, et al. Virtual reality and 3D printing improve preoperative visualization of 3D liver reconstructions-results from a preclinical comparison of presentation modalities and user’s preference. Ann Transl Med. 2021;9(13):1074.

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Acknowledgements

We thank the participating residents from the Peking University People’s Hospital for providing their feedback about our teaching work, and wish them a successful career. We would like to thank Editage ( www.editage.com ) for English language editing and revision services.

This work was supported by the Peking University Health Science Center Medical Education Research Funding Project (2020YB02 to TZ), Beijing Natural Science Foundation (7202214 to TZ, 7224347 to WL), and a grant from the National Natural Science Foundation of China (81970409 to TZ). The funders had no role in the design of the study or collection, analysis, or interpretation of data and in writing the manuscript.

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Weihao Li, Yuanfeng Liu, and Yonghui Wang contributed equally to the article.

Authors and Affiliations

Department of Vascular Surgery, Peking University People’s Hospital, Beijing, 100044, PR China

Weihao Li, Xuemin Zhang, Kun Liu, Xiaoming Zhang & Tao Zhang

Department of Vascular and Endovascular Surgery, First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, PR China

Yuanfeng Liu

Department of Critical Care Medicine, Peking University People’s Hospital, Beijing, 100044, PR China

Yonghui Wang

Beijing Renxin Medical Technology Co., Ltd, Beijing, 100041, PR China

Department of Medical Quality Management, Peking University People’s Hospital, Beijing, 100044, China

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Contributions

WL and TZ made a substantial contribution to the concept and design of the study and prepared the first draft of the manuscript. XuZ, YJ, XiZ, and JC supervised the study and participated in analysis, interpretation of data, and proofreading of the manuscript. WL, YL, YW, KL, and JC collected and analyzed the data. WL, YL, and YW contributed to the writing of the manuscript. JC and TZ substantially revised the manuscript. TZ contributed to the funding of the study. All authors have read and approved the final manuscript.

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Correspondence to Jie Chen or Tao Zhang .

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The study design was approved by the ethical committee of Peking University People’s Hospital (approval number: 2017PHB155) and all the procedures followed in the study were performed in accordance with the Declaration of Helsinki. We obtained written informed consent from the patients involved in the teaching.

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Li, W., Liu, Y., Wang, Y. et al. Educational value of mixed reality combined with a three-dimensional printed model of aortic disease for vascular surgery in the standardized residency training of surgical residents in China: a case control study. BMC Med Educ 23 , 812 (2023). https://doi.org/10.1186/s12909-023-04610-9

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Received : 21 September 2022

Accepted : 24 August 2023

Published : 27 October 2023

DOI : https://doi.org/10.1186/s12909-023-04610-9

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