A quantitative comparative surgical analysis of the endoscopic transorbital approach and frontotemporal-orbitozygomatic approach for extradural exposure of the cavernous sinus.

OBJECTIVE: Recently, the endoscopic superior eyelid transorbital approach (SETA) has emerged as a potential alternative to access the cavernous sinus (CS). Several previous studies have attempted to quantitatively compare the traditional open anterolateral skull base approaches with transorbital exposure; however, these comparisons have been limited to the area of exposure provided by the bone opening and trajectory, and fail to account for the main avenues of exposure provided by subsequent requisite surgical maneuvers. The authors quantitatively compare the surgical access provided by the frontotemporal-orbitozygomatic (FTOZ) approach and the SETA following applicable periclinoid surgical maneuvers, evaluate the surgical exposure of key structures in each, and discuss optimal approach selection. METHODS: SETA and FTOZ approaches were performed with subsequent applicable surgical maneuvers on 8 cadaveric heads. The lengths of exposure of cranial nerves (CNs) II-VI and the cavernous internal carotid artery; the areas of the space accessed within the supratrochlear, infratrochlear, and supramaxillary (anteromedial) triangles; the total area of exposure; and the angles of attack were measured and compared. RESULTS: Exposure of the extradural CS was comparable between approaches, whereas access was significantly greater in the FTOZ approach compared with the SETA. The lengths of extradural exposure of CN III, V1, V2, and V3 were comparable between approaches. The FTOZ approach provided marginally increased exposure of CNs IV (20.9 ± 2.36 mm vs 13.4 ± 3.97 mm, p = 0.023) and VI (14.1 ± 2.44 mm vs 9.22 ± 3.45 mm, p = 0.066). The FTOZ also provided significantly larger vertical (44.5° ± 6.15° vs 18.4° ± 1.65°, p = 0.002) and horizontal (41.5° ± 5.40° vs 15.3° ± 5.06°, p < 0.001) angles of attack, and thus significantly greater surgical freedom, and provided significantly greater access to the supratrochlear (p = 0.021) and infratrochlear (p = 0.007) triangles, and significantly greater exposure of the cavernous internal carotid artery (17.2 ± 1.70 mm vs 8.05 ± 2.37 mm, p = 0.001). Total area of exposure was also significantly larger in the FTOZ, which provided wide access to the lateral wall of the CS as well as the possibility for intradural access. CONCLUSIONS: This is the first study to quantitatively identify the relative advantages of the FTOZ and transorbital approaches at the target region following requisite surgical maneuvers. Understanding these data will aid in selecting an optimal approach and maneuver set based on target lesion size and location.

Migratory schwannoma of the cauda equina with a change in radicular pattern: illustrative case.

BACKGROUND: Intradural spinal tumors are an uncommon entity with a variety of pathologies and symptom patterns. Few cases reports in the literature have described tumor migration within the spinal canal. OBSERVATIONS: A 38-year-old male presented with bilateral upper lumbar radicular symptoms of anterior thigh pain, with an enhancing tumor of the cauda equina initially located at L1-2. He declined surgery initially, and at a follow-up 3 years later, his symptoms were unchanged but the tumor was now located at T12-L1. He again declined surgery, but 3 months later, he had a significant change in his pain distribution, which was now along his posterolateral right leg to his foot with associated dorsiflexion and extensor hallicus longus weakness. At this time, the tumor had migrated to L2-3. He underwent laminectomy and tumor resection with resolution of his radicular symptoms and improvement in his strength back to baseline by the 1-month follow-up. Pathology was consistent with a World Health Organization grade I schwannoma. LESSONS: Migratory schwannoma is a rare entity but should be considered when radicular symptoms acutely change in the setting of a known intradural tumor. Repeat imaging should be performed to avoid wrong-level surgery. Intraoperative imaging can also be used for tumor localization.

Validity of the flap risk score in predicting nasoseptal flap use after endoscopic transsphenoidal pituitary mass resection.

Introduction: There remains a paucity of literature examining the decision algorithm for use of nasoseptal flap (NSF) after endoscopic endonasal approaches (EEA) to pituitary adenoma resection. In 2018, we published the first ever flap risk score (FRS) to predict the use of NSF. We present here a validity study examining the FRS as applied to our center. Methods: A retrospective review was completed of consecutive patients undergoing EEA from January 2015 to March 2021. The sensitivity, specificity, and predictive value of the FRS were calculated. A multivariate logistic model was used to determine the relative weight imaging characteristics in predicting need for NSF. The relative weighting of the FRS was then re-optimized. Results: A total of 376 patients underwent EEA for pituitary adenoma resection, with 113 (30.1%) requiring NSF. The FRS had a sensitivity and specificity of 43.4% and 94.7%, respectively. Sphenoid sinus extension increased the odds of needing a NSF equivalent to 19 mm of tumor height, as opposed to 6 mm in the original 2018 cohort. The re-optimized model had sensitivity and specificity of 79.6% and 76.4%, respectively. Conclusion: We present a validity study examining the utility of FRS in predicting the use of NSF after EEA for pituitary adenoma resection. Our results show that while FRS is still predictive of the need for NSF after EEA, it is not as predictive now as it was for its original cohort. Therefore, a more comprehensive model is necessary to more accurately stratify patients' preoperative risk for NSF.

The genetic basis of hydrocephalus: genes, pathways, mechanisms, and global impact.

Hydrocephalus (HC) is a heterogenous disease characterized by alterations in cerebrospinal fluid (CSF) dynamics that may cause increased intracranial pressure. HC is a component of a wide array of genetic syndromes as well as a secondary consequence of brain injury (intraventricular hemorrhage (IVH), infection, etc.) that can present across the age spectrum, highlighting the phenotypic heterogeneity of the disease. Surgical treatments include ventricular shunting and endoscopic third ventriculostomy with or without choroid plexus cauterization, both of which are prone to failure, and no effective pharmacologic treatments for HC have been developed. Thus, there is an urgent need to understand the genetic architecture and molecular pathogenesis of HC. Without this knowledge, the development of preventive, diagnostic, and therapeutic measures is impeded. However, the genetics of HC is extraordinarily complex, based on studies of varying size, scope, and rigor. This review serves to provide a comprehensive overview of genes, pathways, mechanisms, and global impact of genetics contributing to all etiologies of HC in humans.

The effect of limited healthcare access on poor outcomes among hospitalized COVID-19 patients in Honduras: A single center cohort study.

Background: The COVID-19 pandemic has had a severe impact on the Latin American subcontinent, particularly in areas with limited hospital resources and a restricted Intensive Care Unit (ICU) capacity. This study aimed to provide a comprehensive description of the clinical characteristics, outcomes, and factors associated with survival of COVID-19 hospitalized patients in Honduras. Research question: What were the characteristics and outcomes of COVID-19 patients in a large referral center in Honduras? Study design and methods: This study employed a retrospective cohort design conducted in a single center in San Pedro Sula, Honduras, between October 2020 to March 2021. All hospitalized cases of confirmed COVID-19 during this timeframe were included in the analysis. Univariable and multivariable survival analysis were performed using Kaplan-Meier curves and Cox proportional hazards model aiming to identify factors associated with decreased 30 day in-hospital survival, using a priori-selected factors. Results: A total of 929 confirmed cases were identified in this cohort, with males accounting for 55.4 % of cases. The case fatality rate among the hospitalized patients was found to be 50.1 % corresponding to 466 deaths. Patients with comorbidities such as hypertension, diabetes, obesity, chronic kidney disease, chronic obstructive pulmonary disease and cardiovascular disease had a higher likelihood of mortality. Additionally, non-survivors had a significantly longer time from illness onset to hospital admission compared to survivors (8.2 days vs 4.7 days). Among the cohort, 306 patients (32.9 %) met criteria for ICU admission. However, due to limited capacity, only 60 patients (19·6 %) were admitted to the ICU. Importantly, patients that were unable to receive level-appropriate care had lower likelihood of survival compared to those who received level-appropriate care (hazard ratio: 1.84). Interpretation: This study represents, the largest investigation of in-hospital COVID-19 cases in Honduras and Central America. The findings highlight a substantial case fatality rate among hospitalized patients. In this study, patients who couldn't receive level-appropriate care (ICU admission) had a significantly lower likelihood of survival when compared to those who did. These results underscore the significant impact of healthcare access during the pandemic, particularly in low- and middle-income countries.

The complete anterior petrosectomy: an expanded extended-middle fossa approach with removal of the infratrigeminal petrous apex and drilling of the lateral clivus.

Intradural exposure in the extended middle fossa anterior transpetrosal approach is traditionally limited to the inferior petrosal sinus inferomedially. Expanding bone removal of the petrous apex around the petrous internal carotid artery (ICA), underneath the trigeminal ganglion/mandibular nerve, and into the lateral component of the clivus can significantly expand the limits of this approach beyond the inferior petrosal sinus and allows for exposure of the midline structures, aspects of the contralateral inferior clival region, and, when high riding, the vertebrobasilar junction. To date, no descriptive techniques for drilling into the lateral clivus in this approach have been published. The authors provide a detailed stepwise description of their complete anterior petrosectomy, in use at their institution, that involves skeletonization of the posteromedial petrous ICA, gentle elevation of the trigeminal ganglion/mandibular nerve, removal of the infratrigeminal petrous apex, and two techniques for drilling into the lateral clivus along the petroclival fissure. These techniques provide a direct and unobstructed corridor to the midpetroclival region and ventral brainstem with greater maneuverability and enhanced control of the midline structures, which is especially useful for resection of petroclival meningiomas, chondrosarcomas, and giant vascular lesions of the mid- and upper basilar artery and its proximal branches.

Applicant Perceptions of Postinterview Communication During the 2022 to 2023 Neurosurgery Recruitment Cycle: A Cross-Sectional Survey Study.

OBJECTIVES: To evaluate and describe neurosurgery applicant perceptions of the postinterview communication (PIC) process during the US residency match. METHODS: A voluntary and anonymous postmatch web-based survey was developed and sent to 209 candidates who applied to 1 academic neurosurgery practice during the 2022-2023 recruitment cycle, approximately 1 week following match day. Survey questions focused on their perceptions of and participation behaviors with PIC and how this impacted their final rank list. RESULTS: Seventy-eight (37.3%) of the 209 candidates responded to the survey. Sixty-four (84.2%) respondents reported submitting a letter of intent (LOI) to their number 1 ranked program. Sixty-one (82%) felt pressured to send a LOI to improve their rank status, fearing that it may harm them if they did not. Fifty-four (73.0%) respondents felt pressured to send an early LOI despite not seeing the program in person to communicate interest before programs certified their rank lists. Fourteen (18.9%) respondents agreed that a second look experience impacted their rank list enough to where they regretted an early LOI. Fifty-five (76.4%) respondents disagreed that second-look attendance had no impact on their rank status with a program. Fifty (71.4%) respondents agreed that PIC causes undue stress during the match process. Sixty-one (84.7%) respondents agreed that aspects of PIC require universal guidelines. CONCLUSIONS: This is the first study to describe the perceptions of PIC and behaviors of neurosurgery applicants during the US residency match process. Standardized PIC practices may help to ensure transparency and relieve stress for applicants during the match process.

Endovascular Thrombectomy for the Treatment of Large Ischemic Stroke: A Systematic Review and Meta-Analysis of Randomized Control Trials.

BACKGROUND AND OBJECTIVES: Endovascular thrombectomy has previously been reserved for patients with small to medium acute ischemic strokes. Three recent randomized control trials have demonstrated functional benefit and risk profiles for thrombectomy in large-volume ischemic strokes. The primary objective of the meta-analysis was to determine the combined benefit of endovascular thrombectomy in patients with large-volume ischemic strokes and to determine the risk of adverse events after treatment. METHODS: We systematically searched Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, Scopus, the Cochrane Central Register, and Google Scholar for randomized trials published between January 1, 2010, and February 19, 2023. We included trials specifically comparing endovascular thrombectomy with medical therapy in adults with acute ischemic stroke with large-volume infarctions (defined by Alberta Stroke Program Early Computed Tomography Score 3-5 or a calculated infarct volume of >50 mL). Data were extracted based on prespecified variables on study methods and design, participant characteristics, analysis approach, and efficacy/safety outcomes. Results were combined using a restricted maximum-likelihood estimation random-effects model. Studies were assessed for potential bias and quality of evidence. The primary outcome was an overall ordinal shift across modified Rankin scale scores toward a better outcome at 90 days after either treatment arm. RESULTS: Three thousand forty-four studies were screened, and 29 underwent full-text review. Three randomized trials (N = 1011) were included in the analysis. The pooled random-effects model for the primary outcome favored endovascular thrombectomy over medical management, with a generalized odds ratio of 1.55 (95% CI 1.25-1.91, I 2 = 42.84%). There was a trend toward increased risk of symptomatic intracranial hemorrhage in the thrombectomy group, with a relative risk of 1.85 (95% CI 0.94-3.63, I 2 = 0.00%). CONCLUSION: In patients with large-volume ischemic strokes, endovascular thrombectomy has a clear functional benefit and does not confer increased risk of significant complications compared with medical management alone.

Postoperative Cerebrospinal Fluid-Related Complications After Posterior Fossa and Posterolateral Skull Base Surgeries: Development of a Predictive Model and Clinical Risk Score.

BACKGROUND: Postoperative pseudomeningocele (PMC) and cerebrospinal fluid (CSF) leak are common complications following posterior fossa and posterolateral skull base surgeries. We sought to 1) determine the rate of CSF-related complications and 2) develop a perioperative model and risk score to identify the highest risk patients for these events. METHODS: We performed a retrospective cohort of 450 patients undergoing posterior fossa and posterolateral skull base procedures from 2016 to 2020. Logistic regressions were performed for predictor selection for 3 prespecified models: 1) a priori variables, 2) predictors selected by large effect sizes, and 3) predictors with P ≤ 0.100 on univariable analysis. A final model was created by elimination of nonsignificant predictors, and the integer-based postoperative CSF-related complications (POCC) clinical risk score was derived. Internal validation was done using 10-fold cross-validation and bootstrapping with uniform shrinkage. RESULTS: A total of 115 patients (25.6%) developed PMC and/or CSF leakage. Age >55 years (odds ratio [OR], 0.560; 95% confidence interval [CI], 0.328-0.954), body mass index >30 kg/m2 (OR, 1.88; 95% CI, 1.14-3.10), and postoperative CSF diversion (OR, 2.85; 95% CI, 1.64-5.00) were associated with CSF leak and PMC. Model 2 was the most predictive (cross-validated area under the receiver operating characteristic curve, 0.690). The final risk score was devised using age, body mass index class, dural repair technique, use of bone substitute, and duration of postoperative CSF diversion. The POCC score performed well (cross-validated area under the receiver operating characteristic curve, 0.761) and was highly specific (96.1%). CONCLUSIONS: We created the first generalizable and predictive risk score to identify patients at risk of CSF-related complications. The POCC score could improve surveillance, inform doctor-patient discussions regarding the risks of surgery, and assist in perioperative management.

Oncolytic virotherapies for pediatric tumors.

INTRODUCTION: Many pediatric patients with malignant tumors continue to suffer poor outcomes. The current standard of care includes maximum safe surgical resection followed by chemotherapy and radiation which may be associated with considerable long-term morbidity. The emergence of oncolytic virotherapy (OVT) may provide an alternative or adjuvant treatment for pediatric oncology patients. AREAS COVERED: We reviewed seven virus types that have been investigated in past or ongoing pediatric tumor clinical trials: adenovirus (AdV-tk, Celyvir, DNX-2401, VCN-01, Ad-TD-nsIL-12), herpes simplex virus (G207, HSV-1716), vaccinia (JX-594), reovirus (pelareorep), poliovirus (PVSRIPO), measles virus (MV-NIS), and Senecavirus A (SVV-001). For each virus, we discuss the mechanism of tumor-specific replication and cytotoxicity as well as key findings of preclinical and clinical studies. EXPERT OPINION: Substantial progress has been made in the past 10 years regarding the clinical use of OVT. From our review, OVT has favorable safety profiles compared to chemotherapy and radiation treatment. However, the antitumor effects of OVT remain variable depending on tumor type and viral agent used. Although the widespread adoption of OVT faces many challenges, we are optimistic that OVT will play an important role alongside standard chemotherapy and radiotherapy for the treatment of malignant pediatric solid tumors in the future.

Racial and socioeconomic disparities in glioblastoma outcomes: A single-center, retrospective cohort study.

BACKGROUND: Glioblastoma (GBM) is the most common malignant primary brain tumor. Emerging reports have suggested that racial and socioeconomic disparities influence the outcomes of patients with GBM. No studies to date have investigated these disparities controlling for isocitrate dehydrogenase (IDH) mutation and O-6-methylguanine-DNA methyltransferase (MGMT) status. METHODS: Adult patients with GBM were retrospectively reviewed at a single institution from 2008 to 2019. Univariable and multivariable complete survival analyses were performed. A Cox proportional hazards model was used to assess the effect of race and socioeconomic status controlling for a priori selected variables with known relevance to survival. RESULTS: In total, 995 patients met inclusion criteria. Of these, 117 patients (11.7%) were African American (AA). The median overall survival for the entire cohort was 14.23 months. In the multivariable model, AA patients had better survival compared with White patients (hazard ratio [HR], 0.37; 95% confidence interval [CI], 0.2-0.69). The observed survival difference was significant in both a complete case analysis model and a multiple imputations model accounting for missing molecular data and controlling for treatment and socioeconomic status. AA patients with low income (HR, 2.17; 95% CI, 1.04-4.50), public insurance (HR, 2.25; 95% CI, 1.04-4.87), or no insurance (HR, 15.63; 95% CI, 2.72-89.67) had worse survival compared with White patients with low income, public insurance, or no insurance, respectively. CONCLUSIONS: Significant racial and socioeconomic disparities were identified after controlling for treatment, GBM genetic profile, and other variables associated with survival. Overall, AA patients demonstrated better survival. These findings may suggest the possibility of a protective genetic advantage in AA patients. PLAIN LANGUAGE SUMMARY: To best personalize treatment for and understand the causes of glioblastoma, racial and socioeconomic influences must be examined. The authors report their experience at the O'Neal Comprehensive Cancer Center in the deep south. In this report, contemporary molecular diagnostic data are included. The authors conclude that there are significant racial and socioeconomic disparities that influence glioblastoma outcome and that African American patients do better.

Endovascular thrombectomy for the treatment of large ischemic stroke: a systematic review and meta-analysis of randomized control trials.

Importance: Endovascular thrombectomy (ET) has previously been reserved for patients with small to medium acute ischemic strokes. Three recent randomized control trials (RCTs) have demonstrated functional benefit and risk profiles for ET in large volume ischemic strokes. Objective: The primary objective of the meta-analysis was to determine the combined benefit of ET in adult patients with large volume acute ischemic strokes and to better determine the risk of adverse events following ET. Data Sources: We systematically searched MEDLINE, EMBASE, SCOPUS, the Cochrane Central Register of Controlled, and Google Scholar for all RCTs published in English language between January 1, 2010, to February 19, 2023. Study Selection: We included only RCTs specifically comparing ET to medical therapy in patients with acute ischemic stroke with large volume infarctions as defined by Alberta Stroke Program Early Computed Tomography Score (ASPECTS) 3-5 or calculated infarct volume of > 50-70mL. Two independent reviewers screened potential studies for full text review and metaanalysis inclusion with conflicts being resolved by consensus or third reviewer. Data Extraction and Synthesis: Data was extracted based on pre-specified variables on study methods and design, participant characteristics, analysis approach, as well as efficacy and safety outcomes. Results were combined using a restricted maximum-likelihood estimation random-effects model. Studies were assessed for potential bias and quality of evidence. Main Outcomes and Measures: The prespecified primary outcome was an overall ordinal shift across the range of modified Rankin scale scores toward a better outcome at 90 days following either ET or medical management for patients with large volume ischemic strokes. Results: A total of 3044 studies were screened, and 29 underwent full text review. 3 RCTs (1011 patients) were included in the analysis. The pooled random effects model for the primary outcome of mRS improvement favored ET over medical management, generalized odds ratio 1.55 [95% CI 1.25 - 1.91, T 2 = 0.01, I 2 = 42.84%]. There was a trend toward increased risk of symptomatic ICH in the ET group, relative risk 1.85 [95% CI 0.94 - 3.63, T 2 = 0.00, I 2 = 0.00%]. Conclusions and Relevance: In patients with large volume ischemic strokes, ET has a clear functional benefit and does not confer increased risk of significant complications compared to medical management alone.

Morbid Obesity Increases Length of Surgery in Elective Anterior Cervical Discectomy and Fusion Procedures but Not Readmission or Reoperation Rates: A Cohort Study.

BACKGROUND: As the obesity epidemic grows, the number of morbidly obese patients undergoing anterior cervical discectomy and fusion (ACDF) continues to increase. Despite the association of obesity with perioperative complications in anterior cervical surgery, the impact of morbid obesity on ACDF complications remains controversial, and studies examining morbidly obese cohorts are limited. METHODS: A single-institution, retrospective analysis of patients undergoing ACDF from September 2010 to February 2022 was performed. Demographic, intraoperative, and postoperative data were collected via review of the electronic medical record. Patients were categorized as nonobese (body mass index [BMI] <30), obese (BMI 30-39.9), or morbidly obese (BMI ≥40). Associations of BMI class with discharge disposition, length of surgery, and length of stay were assessed using multivariable logistic regression, multivariable linear regression, and negative binomial regression, respectively. RESULTS: The study included 670 patients undergoing single-level or multilevel ACDF: 413 (61.6%) nonobese, 226 (33.7%) obese, and 31 (4.6%) morbidly obese patients. BMI class was associated with prior history of deep venous thrombosis (P < 0.01), pulmonary thromboembolism (P < 0.05), and diabetes mellitus (P < 0.001). In bivariate analysis, there was no significant association between BMI class and reoperation or readmission rates at 30, 60, or 365 days postoperatively. In multivariable analysis, greater BMI class was associated with increased length of surgery (P = 0.03), but not length of stay or discharge disposition. CONCLUSIONS: For patients undergoing ACDF, greater BMI class was associated with increased length of surgery, but not reoperation rate, readmission rate, length of stay, or discharge disposition.

Incidence and management of postoperative pseudomeningocele and cerebrospinal fluid leak after Chiari malformation type I decompression.

OBJECTIVE: The optimal surgical management of Chiari malformation type I (CM-I) remains controversial and heterogeneous. The authors sought to investigate patient-specific, technical, and perioperative features that may affect the incidence of CSF-related complications including pseudomeningocele and CSF leak at their institution. METHODS: The authors performed a single-center, retrospective review of all adult patients with CM-I who underwent posterior fossa decompression. Patient demographics, operative details, and perioperative factors were collected via electronic medical record review. The authors performed Fisher's exact test and independent Student t-tests for categorical and continuous variables, respectively. Univariate regression analysis was performed to determine odds ratios. A multivariable regression analysis was performed for those factors with p < 0.10 or large effect sizes (OR ≥ 2.0 or ≤ 0.50) by univariate analysis. The STROBE guidelines for observational studies were followed. RESULTS: A total of 59 adult patients were included. Most patients were female (78.0%), and the mean body mass index was 32.2 (± 9.0). Almost one-third (30.5%) of patients had a syrinx on preoperative imaging. All patients underwent expansile duraplasty, of which 47 (79.7%) were from autologous pericranium. Arachnoid opening for fourth ventricular inspection was performed in 26 (44.1%) cases. CSF-related complications were identified in 18 (30.5%) of cases. Thirteen (22.0%) patients required readmission and 11 (18.6%) required intervention such as wound revision (n = 5), wound revision with CSF diversion (n = 4), CSF diversion alone (n = 1), or blood patch (n = 1). Three (5.1%) patients required permanent CSF diversion. Male sex (OR 3.495), diabetes mellitus (OR 0.249), tobacco use (OR 2.53), body mass index more than 30 (OR 2.45), preoperative syrinx (OR 1.733), autologous duraplasty (OR 0.331), and postoperative steroids (OR 2.825) were included in the multivariable analysis. No factors achieved significance by univariate or multivariable analysis (all p > 0.05). CONCLUSIONS: The authors report a single-center, retrospective experience of posterior fossa decompression for 59 adults with CM-I. No perioperative or technical features were found to affect the CSF-related complication rate. More standardized practices within centers are necessary to better delineate the true risk factors and potential protective factors against CSF-related complications.

Immunotherapy for Pediatric Brain and Spine Tumors: Current State and Future Directions.

BACKGROUND: Brain tumors are the most common solid tumors and the leading cause of cancer-related deaths in children. Incidence in the USA has been on the rise for the last 2 decades. While therapeutic advances in diagnosis and treatment have improved survival and quality of life in many children, prognosis remains poor and current treatments have significant long-term sequelae. SUMMARY: There is a substantial need for the development of new therapeutic approaches, and since the introduction of immunotherapy by immune checkpoint inhibitors, there has been an exponential increase in clinical trials to adopt these and other immunotherapy approaches in children with brain tumors. In this review, we summarize the current immunotherapy landscape for various pediatric brain tumor types including choroid plexus tumors, embryonal tumors (medulloblastoma, AT/RT, PNETs), ependymoma, germ cell tumors, gliomas, glioneuronal and neuronal tumors, and mesenchymal tumors. We discuss the latest clinical trials and noteworthy preclinical studies to treat these pediatric brain tumors using checkpoint inhibitors, cellular therapies (CAR-T, NK, T cell), oncolytic virotherapy, radioimmunotherapy, tumor vaccines, immunomodulators, and other targeted therapies. KEY MESSAGES: The current landscape for immunotherapy in pediatric brain tumors is still emerging, but results in certain tumors have been promising. In the age of targeted therapy, genetic tumor profiling, and many ongoing clinical trials, immunotherapy will likely become an increasingly effective tool in the neuro-oncologist armamentarium.

Assessing the Impact of Changes to USMLE Step 1 Grading on Evaluation of Neurosurgery Residency Applicants in the United States: A Program Director Survey.

BACKGROUND: Neurosurgery (NS) is among the most selective specialties in the United States. As the United States Medical Licensing Examination (USMLE) Step 1 transitions to a binary pass/fail score, residency programs face unclear challenges in screening and evaluating applicants. The aim of this study is to provide insights into the perceived impact of changes to the USMLE Step 1 grading in the applicant selection process. METHODS: We created a survey using questions regarding NS program demographics, the perceived predictive abilities of Step 1 and Step 2 clinical knowledge (CK), and several factors that programs consider when assessing applicants. We queried program directors (PDs), program coordinators (PCs), and assistant PDs at 117 NS residency programs. Respondents were asked to rank these factors in order of importance for selection at their respective training program. We used descriptive statistics and a Wilcoxon matched-pairs signed-rank test to evaluate the effects of these changes using STATA 17. RESULTS: A total of 35 (30%) residency programs responded with 26 (74%) completing the factor ranking questions. 86% (95% confidence interval, 71.5%-94.3%) disagreed that the changes will better prepare students clinically. USMLE Step 2 CK scores, class rank, and away rotations saw significant increases in priority in the absence of a graded Step 1, whereas letters of recommendation and surrogates for research productivity saw notable, but not significant, changes after adjusting for multiple testing. CONCLUSIONS: Reporting binary Step 1 grades marks a significant shift in assessing applicants for NS residency by emphasizing Step 2 CK, class rank, and research productivity.

Review of Cerebrospinal Fluid Physiology and Dynamics: A Call for Medical Education Reform.

BACKGROUND: The flow of cerebrospinal fluid (CSF) has been described as a unidirectional system with the choroid plexus serving as the primary secretor of CSF and the arachnoid granulations as primary reabsorption site. This theory of neurosurgical forefathers has been universally adopted and taught as dogma. Many neuroscientists have found difficulty reconciling this theory with common pathologies, and recent studies have found that this "classic" hypothesis may not represent the full picture. OBJECTIVE: To review modern CSF dynamic theories and to call for medical education reform. METHODS: We reviewed the literature from January 1990 to December 2020. We searched the PubMed database using key terms "cerebrospinal fluid circulation," "cerebrospinal fluid dynamics," "cerebrospinal fluid physiology," "glymphatic system," and "glymphatic pathway." We selected articles with a primary aim to discuss either CSF dynamics and/or the glymphatic system. RESULTS: The Bulat-Klarica-Oreskovic hypothesis purports that CSF is secreted and reabsorbed throughout the craniospinal axis. CSF demonstrates similar physiology to that of water elsewhere in the body. CSF "circulates" throughout the subarachnoid space in a pulsatile to-and-fro fashion. Osmolarity plays a critical role in CSF dynamics. Aquaporin-4 and the glymphatic system contribute to CSF volume and flow by establishing osmolarity gradients and facilitating CSF movement. Multiple studies demonstrate that the choroid plexus does not play any significant role in CSF circulation. CONCLUSION: We have highlighted major studies to illustrate modern principles of CSF dynamics. Despite these, the medical education system has been slow to reform curricula and update learning resources.