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Critically reading machine learning literature in neurosurgery: a reader’s guide and checklist for appraising prediction models

Sivaram Emani, Akshay Swaminathan, Ben Grobman, Julia B. Duvall, Ivan Lopez, Omar Arnaout, and Kevin T. Huang

OBJECTIVE

Machine learning (ML) has become an increasingly popular tool for use in neurosurgical research. The number of publications and interest in the field have recently seen significant expansion in both quantity and complexity. However, this also places a commensurate burden on the general neurosurgical readership to appraise this literature and decide if these algorithms can be effectively translated into practice. To this end, the authors sought to review the burgeoning neurosurgical ML literature and to develop a checklist to help readers critically review and digest this work.

METHODS

The authors performed a literature search of recent ML papers in the PubMed database with the terms "neurosurgery" AND "machine learning," with additional modifiers "trauma," "cancer," "pediatric," and "spine" also used to ensure a diverse selection of relevant papers within the field. Papers were reviewed for their ML methodology, including the formulation of the clinical problem, data acquisition, data preprocessing, model development, model validation, model performance, and model deployment.

RESULTS

The resulting checklist consists of 14 key questions for critically appraising ML models and development techniques; these are organized according to their timing along the standard ML workflow. In addition, the authors provide an overview of the ML development process, as well as a review of key terms, models, and concepts referenced in the literature.

CONCLUSIONS

ML is poised to become an increasingly important part of neurosurgical research and clinical care. The authors hope that dissemination of education on ML techniques will help neurosurgeons to critically review new research better and more effectively integrate this technology into their practices.

Free access

Letter to the Editor. On the right side of history: expanding diversity within neurosurgery

Marianne I. J. Tissot, Andre E. Boyke, Alvin Onyewuenyi, Gregory Glauser, Evalyn S. Mackenzie, Bethany J. Thach, and Donald K. E. Detchou

Open access

Evaluating frailty, mortality, and complications associated with metastatic spine tumor surgery using machine learning–derived body composition analysis

Elie Massaad, Christopher P. Bridge, Ali Kiapour, Mitchell S. Fourman, Julia B. Duvall, Ian D. Connolly, Muhamed Hadzipasic, Ganesh M. Shankar, Katherine P. Andriole, Michael Rosenthal, Andrew J. Schoenfeld, Mark H. Bilsky, and John H. Shin

OBJECTIVE

Cancer patients with spinal metastases may undergo surgery without clear assessments of prognosis, thereby impacting the optimal palliative strategy. Because the morbidity of surgery may adversely impact recovery and initiation of adjuvant therapies, evaluation of risk factors associated with mortality risk and complications is critical. Evaluation of body composition of cancer patients as a surrogate for frailty is an emerging area of study for improving preoperative risk stratification.

METHODS

To examine the associations of muscle characteristics and adiposity with postoperative complications, length of stay, and mortality in patients with spinal metastases, the authors designed an observational study of 484 cancer patients who received surgical treatment for spinal metastases between 2010 and 2019. Sarcopenia, muscle radiodensity, visceral adiposity, and subcutaneous adiposity were assessed on routinely available 3-month preoperative CT images by using a validated deep learning methodology. The authors used k-means clustering analysis to identify patients with similar body composition characteristics. Regression models were used to examine the associations of sarcopenia, frailty, and clusters with the outcomes of interest.

RESULTS

Of 484 patients enrolled, 303 had evaluable CT data on muscle and adiposity (mean age 62.00 ± 11.91 years; 57.8% male). The authors identified 2 clusters with significantly different body composition characteristics and mortality risks after spine metastases surgery. Patients in cluster 2 (high-risk cluster) had lower muscle mass index (mean ± SD 41.16 ± 7.99 vs 50.13 ± 10.45 cm2/m2), lower subcutaneous fat area (147.62 ± 57.80 vs 289.83 ± 109.31 cm2), lower visceral fat area (82.28 ± 48.96 vs 239.26 ± 98.40 cm2), higher muscle radiodensity (35.67 ± 9.94 vs 31.13 ± 9.07 Hounsfield units [HU]), and significantly higher risk of 1-year mortality (adjusted HR 1.45, 95% CI 1.05–2.01, p = 0.02) than individuals in cluster 1 (low-risk cluster). Decreased muscle mass, muscle radiodensity, and adiposity were not associated with a higher rate of complications after surgery. Prolonged length of stay (> 7 days) was associated with low muscle radiodensity (mean 30.87 vs 35.23 HU, 95% CI 1.98–6.73, p < 0.001).

CONCLUSIONS

Body composition analysis shows promise for better risk stratification of patients with spinal metastases under consideration for surgery. Those with lower muscle mass and subcutaneous and visceral adiposity are at greater risk for inferior outcomes.

Restricted access

Implication of nutritional status for adverse outcomes after surgery for metastatic spine tumors

Grant H. Rigney, Elie Massaad, Ali Kiapour, Shahaan S. Razak, Julia B. Duvall, Akeive Burrows, Syed I. Khalid, Rafael De La Garza Ramos, Daniel G. Tobert, Theresa Williamson, Ganesh M. Shankar, Andrew J. Schoenfeld, and John H. Shin

OBJECTIVE

Surgery for metastatic spinal tumors can have a substantial impact on patients’ quality of life by alleviating pain, improving function, and correcting spinal instability when indicated. The decision to operate is difficult because many patients with cancer are frail. Studies have highlighted the importance of preoperative nutritional status assessments; however, little is known about which aspects of nutrition accurately inform clinical outcomes. This study investigates the interaction and prognostic importance of various nutritional and frailty measures in patients with spinal metastases.

METHODS

A retrospective analysis of consecutive patients who underwent surgery for spinal metastases between 2014 and 2020 at the Massachusetts General Hospital was performed. Patients were stratified according to the New England Spinal Metastasis Score (NESMS). Frailty was assessed using the metastatic spinal tumor frailty index. Nutrition was assessed using the prognostic nutritional index (PNI), preoperative body mass index, albumin, albumin-to-globulin ratio, and platelet-to-lymphocyte ratio. Outcomes included postoperative survival and complication rates, with focus on wound-related complications.

RESULTS

This study included 154 individuals (39% female; mean [SD] age 63.23 [13.14] years). NESMS 0 and NESMS 3 demonstrated the highest proportions of severely frail patients (56.2%) and nonfrail patients (16.1%), respectively. Patients with normal nutritional status (albumin-to-globulin ratio and PNI) had a better prognosis than those with poor nutritional status when stratified by NESMS. Multivariable regression adjusted for NESMS and frailty showed that a PNI > 40.4 was significantly associated with decreased odds of 90-day complications (OR 0.93, 95% CI 0.85–0.98). After accounting for age, sex, primary tumor pathology, physical function, nutritional status, and frailty, a preoperative nutrition consultation was associated with a decrease in postoperative wound-related complications (average marginal effect −5.00%; 95% CI −1.50% to −8.9%).

CONCLUSIONS

The PNI was most predictive of complications and may be a key biomarker for risk stratification in the 90 days following surgery. Nutrition consultation was associated with a reduced risk of wound-related complications, attesting to the importance of this preoperative intervention. These findings suggest that nutrition plays an important role in the postsurgical course and should be considered when developing a treatment plan for spinal metastases.

Free access

Scoping review on the state of racial disparities literature in the treatment of neurosurgical disease: a call for action

Edwin Owolo, Andreas Seas, Brandon Bishop, Jacob Sperber, Zoey Petitt, Alissa Arango, Seeley Yoo, Sharrieff Shah, Julia B. Duvall, Eli Johnson, Nancy Abu-Bonsrah, Samantha Kaplan, Sonia Eden, William W. Ashley Jr., Theresa Williamson, and C. Rory Goodwin

OBJECTIVE

Racial disparities are ubiquitous across medicine in the US. This study aims to assess the evidence of racial disparities within neurosurgery and across its subspecialties, with a specific goal of quantifying the distribution of articles devoted to either identifying, understanding, or reducing disparities.

METHODS

The authors searched the MEDLINE, EMBASE, and Scopus databases by using keywords to represent the concepts of neurosurgery, patients, racial disparities, and specific study types. Two independent reviewers screened the article titles and abstracts for relevance. A third reviewer resolved conflicts. Data were then extracted from the included articles and each article was categorized into one of three phases: identifying, understanding, or reducing disparities. This review was conducted in accordance with the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines.

RESULTS

Three hundred seventy-one studies published between 1985 and 2023 were included. The distribution of racial disparities literature was not equally spread among specialties, with spine representing approximately 48.3% of the literature, followed by tumor (22.1%) and general neurosurgery (12.9%). Most studies were dedicated to identifying racial disparities (83.6%). The proportion of literature devoted to understanding and reducing disparities was much lower (15.1% and 1.3%, respectively). Black patients were the most negatively impacted racial/ethnic group in the review (63.3%). The Hispanic or Latino ethnic group was the second most negatively impacted (25.1%). The following categories—other outcomes (28.0%), the offering of treatment (21.6%), complications (18.6%), and survival (16.7%)—represented the most frequently measured outcomes.

CONCLUSIONS

Although strides have been taken to identify racial disparities within neurosurgery, fewer studies have focused on understanding and reducing these disparities. The tremendous rise of literature within this domain but the relative paucity of solutions necessitates the study of targeted interventions to provide equitable care for all patients undergoing neurosurgical treatment.

Restricted access

Promoting diversity in neurosurgery through a virtual symposium

Antoinette J. Charles, Andreas Seas, Jacquelyn Corley, Julia B. Duvall, Edwin Owolo, Nancy Abu-Bonsrah, Aladine A. Elsamadicy, Venita Simpson, Olabisi Sanusi, Langston T. Holly, Analiz Rodriguez, Edjah K. Nduom, Allan D. Levi, Linda M. Liau, Alfredo Quiñones-Hinojosa, Isaac Karikari, Gerald Grant, Anthony T. Fuller, and C. Rory Goodwin

OBJECTIVE

The rates of women and underrepresented racial and ethnic minority (UREM) students successfully matching into neurosurgical residency are extremely low and do not reflect the makeup of the general population. As of 2019, only 17.5% of neurosurgical residents in the United States were women, 4.95% were Black or African American, and 7.2% were Hispanic or Latinx. Earlier recruitment of UREM students will help to diversify the neurosurgical workforce. Therefore, the authors developed a virtual educational event for undergraduate students entitled "Future Leaders in Neurosurgery Symposium for Underrepresented Students’’ (FLNSUS). The primary objectives of the FLNSUS were to expose attendees to 1) neurosurgeons from diverse gender, racial, and ethnic backgrounds; 2) neurosurgical research; 3) opportunities for neurosurgical mentorship; and 4) information about life as a neurosurgeon. The authors hypothesized that the FLNSUS would increase student self-confidence, provide exposure to the specialty, and reduce perceived barriers to a neurosurgical career.

METHODS

To measure the change in participant perceptions of neurosurgery, pre- and postsymposium surveys were administered to attendees. Of the 269 participants who completed the presymposium survey, 250 participated in the virtual event and 124 completed the postsymposium survey. Paired pre- and postsurvey responses were used for analysis, yielding a response rate of 46%. To assess the impact of participant perceptions of neurosurgery as a field, pre- and postsurvey responses to questions were compared. The change in response was analyzed, and a nonparametric sign test was performed to check for significant differences.

RESULTS

According to the sign test, applicants showed increased familiarity with the field (p < 0.001), increased confidence in their abilities to become neurosurgeons (p = 0.014), and increased exposure to neurosurgeons from diverse gender, racial, and ethnic backgrounds (p < 0.001 for all categories).

CONCLUSIONS

These results reflect a significant improvement in student perceptions of neurosurgery and suggest that symposiums like the FLNSUS may promote further diversification of the field. The authors anticipate that events promoting diversity in neurosurgery will lead to a more equitable workforce that will ultimately translate to enhanced research productivity, cultural humility, and patient-centered care in neurosurgery.