Bauman, Megan M. J.

BACKGROUND AND OBJECTIVES: The intraosseous subarcuate loop (SL) is a unique variant of the anterior inferior cerebellar artery (AICA), where a loop of the artery is trapped in the petrous bone's subarcuate fossa (SF). Recognizing this variant is crucial for planning cerebellopontine angle (CPA) surgeries; however, data regarding its frequency and management vary in the published literature. A cohort from a single center was studied using MRI to assess its prevalence, and the findings were compared with the existing literature. In addition, an intraoperative guide for mobilizing the intraosseous AICA's SL was provided through a detailed step-by-step cadaveric dissection. METHODS: Two hundred fifty-eight patients who had undergone MRI scans of the CPA (516 sides) were retrospectively reviewed. MRIs displaying vascular loops visible in the axial view were analyzed using multiplanar reconstruction, and the intraosseous loop frequency was evaluated. A scoping review was undertaken to provide an overview of previously published data on its prevalence. One embalmed and latex-injected specimen with intraosseous AICA's SL was dissected through a retrosigmoid approach, and 1 surgical case was detailed, describing the procedure to release it. RESULTS: Intraosseous AICA's SL mobilization involves the identification of its entry and exit points within the petrous bone, dural incision to expose the SF, SF drilling, subarcuate artery division, and detaching the vascular loop. Preservation of a dural cuff is crucial to prevent vascular injury. We analyzed 258 brain MRIs (mean age 55 years, 42% male). The intraosseous AICA's SL was present in 4 of 516 evaluated CPAs (0.8%). The prevalence of the vascular anomaly in the reviewed literature using different radiological modalities ranged from 0.2% to 1.6%. CONCLUSION: The intraosseous AICA's SL is an uncommon anatomic variation detectable by MRI, posing an added risk in CPA surgery. Identifying and properly mobilizing it is crucial for safe vascular preservation.

OBJECTIVE Imaging surveillance with serial MRI, or a "wait-and-scan" approach, is a management option for patients with small or medium-sized vestibular schwannomas (VSs). Prior publications have indicated no distinct quality of life advantage to upfront treatment compared with initial wait-and-scan management. However, imaging surveillance is dependent on patient adherence to follow-up. In this study, the authors aimed to identify rates and predictors of patient loss to follow-up during wait-and-scan management of sporadic VS. METHODS A single-center study was conducted including all patients from 2013 to 2018 who had undergone upfront imaging surveillance of sporadic VS. Patient data were retrospectively obtained from the electronic medical record. Outcomes of interest included loss to follow-up unrelated to death and inconsistent adherence to imaging surveillance recommendations. Logistic regression analyses were conducted to evaluate factors associated with loss to follow-up. RESULTS Over a 6-year study period, 270 patients underwent initial imaging surveillance of a sporadic VS. The median tumor diameter was 8.6 mm (range 1–28.9 mm). At the time of censoring, 106 patients (39.3%) had received treatment, 157 (58.1%) had been advised to continue follow-up, and 7 (2.6%) had died of non–VS-related causes. In total, 73 patients (27.0%) were completely lost to follow-up prior to the first treatment or death. Additionally, 60 patients (22.2%) missed at least 1 MRI follow-up or imaging follow-up was delayed by more than 1 year. Multivariable logistic regression identified an out-of-state residence (OR 3.05, 95% CI 1.58–5.89, p = 0.0009) and a smaller tumor size (unit OR per 1-mm increase in size, OR 0.88, 95% CI 0.83–0.95, p = 0.0006) to be associated with loss to follow-up. Patients living ≥ 350 miles from the hospital or with tumors ≤ 3 mm at the time of initial clinic evaluation were most likely to be lost to follow-up. Only a smaller tumor size was associated with an increased risk of inconsistent imaging follow-up (unit OR per 1-mm increase in size, OR 0.92, 95% CI 0.87–0.98, p = 0.007). CONCLUSIONS Patients undergoing imaging surveillance of VS are at risk for loss to follow-up and inconsistent imaging surveillance. Patients with smaller tumors or those living farther away from the treating institution are at highest risk for being lost to follow-up.

OBJECTIVE Advances in surgical technology and microneurosurgery have led to increased utilization of so-called minimally invasive approaches, including the supraorbital eyebrow (SE) and minipterional (MPT) approaches for lesions involving the interpeduncular region. This study aimed to describe and compare anatomical landmarks, along with highlighting the advantages and disadvantages of the SE and MPT approaches to the interpeduncular region. METHODS Ten formalin-fixed, latex-injected cadaveric specimens were used to perform bilateral SE and MPT approaches to the interpeduncular region. The operative depth of each approach to key anatomical landmarks was measured. Forty-five axial thin-slice computed tomography studies were reviewed to calculate the operative angles, with consideration of the midline as a reference. A 3D interactive anatomical model generated through the photogrammetry scanning technique was described. RESULTS The depths of the operative corridors of the SE and MPT approaches to the interpeduncular fossa were 83.4 ± 1.8 mm and 67.7 ± 3.2 mm, respectively (p < 0.001). The mean angle of the MPT approach to the interpeduncular fossa was significantly wider than the one provided by the SE approach (39.9° ± 5.1° vs 28.4° ± 3.6°, p < 0.001). The interpeduncular region can consistently be accessed through the carotid-oculomotor triangle with the SE approach, as well as with the MPT approach. Furthermore, the SE route offered adequate access to the interpeduncular fossa through the opticocarotid triangle. The MPT route provided direct access to the upper prepontine cistern and anterior mesencephalic zone (AMZ). CONCLUSIONS The MPT approach provides a wider and shorter operative corridor and can be employed for lesions in the interpeduncular region with extension to the prepontine cistern and ventrolateral midbrain lesions requiring access through the AMZ. The SE approach is better suited for ventromedial midbrain lesions requiring access via the interpeduncular fossa safe entry zone. Additional studies analyzing these approaches in a clinical setting will help to delineate their reliability and efficacy.

OBJECTIVE Following resection of posterior superior frontal gyrus (PSFG) tumors, patients can experience supplementary motor area (SMA) syndrome consisting of contralateral hemiapraxia and/or speech apraxia. Given the heterogeneity of PSFG tumors, the authors sought to determine the risk of postoperative deficits and assess predictors of outcomes for all intraparenchymal PSFG tumors undergoing surgery (biopsy or resection), regardless of histology. METHODS This was a retrospective single-center cohort study of adult PSFG-region tumors undergoing biopsy or resection by a single surgeon. RESULTS A total of 106 consecutive patients undergoing 123 procedures (21 biopsies, 102 resections) fulfilled inclusion and exclusion criteria. Anaplastic astrocytomas were the most frequent among resected tumors (39% vs 29%), while glioblastomas were most common among biopsies (38% vs 27%) (p < 0.0001). The biopsy cohort was more likely to have tumor involvement outside the PSFG (90% vs 62%) (p = 0.011), most commonly in the motor cortex (67% vs 31%) (p = 0.005). Seizures were the most common presenting symptom in the resection cohort (p = 0.017), while motor deficits were more common in the biopsy cohort (58% vs 29%) (p < 0.001). Immediate postoperative neurological deficits occurred in 71 cases (58%), but only 3 of the deficits were permanent at 6 months of follow-up (2%). Postoperative SMA syndrome occurred in 48 cases (47%) and was significantly associated with involvement of the motor cortex (p = 0.018) or cingulate gyrus (p = 0.023), which were also significant in multivariate analysis as risk factors for SMA syndrome. However, postoperative SMA syndrome was not significantly associated with overall survival (p = 0.51). There were no perioperative deaths, but corpus callosum involvement (p < 0.001), contrast enhancement (p = 0.003), and glioblastoma pathology (p = 0.038) predicted worse overall survival in patients undergoing resection. CONCLUSIONS Nearly half of all patients undergoing resection of PSFG-region tumors experience a postoperative SMA syndrome. Individuals with corpus callosum and/or motor cortex involvement may be at an increased risk of experiencing SMA syndrome. However, these deficits are usually transient, and the risk of permanent new deficits is very low (3%). Preoperative characteristics including corpus callosum involvement and tumor enhancement—in addition to pathology—might serve as predictors of overall survival within this patient population.

BACKGROUND AND OBJECTIVES: Access to the amygdala and hippocampus (A/H) is complex. To address the limitations and invasiveness of traditional approaches, including the Transsylvian, Subtemporal, and Supracerebellar infratentorial approaches, we developed the suprapetrous infratemporal (SPIT) approach. This study describes the nuances of this approach in both cadaveric studies and clinical cases. METHODS: Three unilateral exposures were performed using microscopic and endoscopic methodologies in the SPIT approach. After cadaveric investigation, this approach was successfully implemented in representative clinical cases. RESULTS: The SPIT approach enabled direct access to the inferior A/H, circumventing the requirement for temporal lobe retraction and detachment of the temporal lobe from the dura through a subtemporal route by drilling the upper part of the mastoid, consequently mitigating tension on the vein of Labbé. This enabled a bottom-up view because one would gain with a zygomatic osteotomy and forward projection like a mini-posterior petrosal view by using a transmastoid view, without cutting down the zygomatic arch and opening the dura subtemporally, limiting patient pain and preventing case comorbidity. The SPIT approach was performed in 2 cases of mesial temporal cavernoma presenting with seizures. The lesion was visualized intraoperatively and was successfully removed in these cases. The postoperative course was excellent with no complications, and gross total resection was radiographically confirmed with Engel Class 1a seizure freedom. CONCLUSION: The SPIT approach is a complementary approach for inferior A/H disease, combining the combined middle fossa approach modified for intradural pathology. Limited drilling of the upper aspect of the mastoid with a medial dural opening at the level of the arcuate eminence provides a direct trajectory with minimal brain retraction. Additional research encompassing a larger patient cohort and extended follow-up periods is required to substantiate the advantages of SPIT in the management of inferior A/H lesions.

Abstract Background Cadaveric dissection remains a preferred and irreplaceable learning modality among neurosurgery residents. We aimed to develop and describe a tiered, quantifiable, and practical curriculum for cranial neurosurgical anatomy education. We report the structure and evaluation of our 2-year pilot study to serve as a suggested guide for other neurosurgery programs. Methods Our Complex Cranial Dissection Program is tailored to the needs of junior-level neurosurgery residents based on their postgraduation years 1 to 4. Dissections are performed in a sequential manner, each of which emphasize a particular set of manual skills and neuroanatomical knowledge. Dissections are scored on a scale of 10 points. The grading was based on specific landmarks and anatomical structures, which need to be exposed, explored, and preserved. Results Out of 16 residents, 14 individuals (87.5%) attended the dissections in the first iteration of the program and 16 individuals (100%) attended the dissections in the second iteration. A total of 17 dissections were performed across all years. In survey feedback about the program, 100% (Year 1) and 94% (Year 2) of residents considered the assigned dissections to be appropriate for their respective training levels. Further, 100% (Year 1) and 94% (Year 2) of residents endorsed that the dissections were important and helpful for their practice prior to similar operating room experiences. Conclusion The development and implementation of structured dissection programs within residency training, along with dedicated staff, and objective feedback serve a crucial role in neurosurgical education to further develop and enhance surgical skills in the operative setting.

OBJECTIVE Despite 51.2% of medical school graduates being female, only 29.8% of neurosurgery residency applicants are female. Furthermore, only 12.6% of neurosurgery applicants identify as underrepresented in medicine (URM). Evaluating the entry barriers for female and URM students is crucial in promoting the equity and diversity of the neurosurgical workforce. The objective of this study was to evaluate barriers to neurosurgery for medical students while considering the interaction between gender and race. METHODS A Qualtrics survey was distributed widely to US medical students, assessing 14 factors of hesitancy toward neurosurgery. Likert scale responses, representing statement agreeability, converted to numeric values on a 7-point scale were analyzed by Mann-Whitney U-test and ANOVA comparisons with Bonferroni correction. RESULTS Of 540 respondents, 68.7% were female and 22.6% were URM. There were 22.6% male non-URM, 7.4% male URM, 53.5% female non-URM, and 15.2% female URM respondents. The predominant reasons for hesitancy toward neurosurgery included work/life integration, length of training, competitiveness of residency position, and perceived malignancy of the field. Females were more hesitant toward neurosurgery due to maternity/paternity needs (p = 0.005), the absence of seeing people like them in the field (p < 0.001), and opportunities to pursue health equity work (p < 0.001). Females were more likely to have difficulties finding a mentor in neurosurgery who represented their identities (p = 0.017). URM students were more hesitant toward neurosurgery due to not seeing people like them in the field (p < 0.001). Subanalysis revealed that when students were stratified by both gender and URM status, there were more reasons for hesitancy toward neurosurgery that had significant differences between groups (male URM, male non-URM, female URM, and female non-URM students), suggesting the importance of intersectionality in this analysis. CONCLUSIONS The authors highlight the implications of gender and racial diversity in the neurosurgical workforce on medical student interest and recruitment. Their findings suggest the importance of actively working to address these barriers, including 1) maternity/paternity policy reevaluation, standardization, and dissemination; and 2) actively providing resources for the creation of mentorship relationships for both women and URM students in an effort to create a workforce that aligns with the changing demographics of medical graduates to continue to improve diversity in neurosurgery.

OBJECTIVE Several pathologies either invade or arise within the orbit. These include meningiomas, schwannomas, and cavernous hemangiomas among others. Although several studies describing various approaches to the orbit are available, no study describes all cranio-orbital and orbitocranial approaches with clear, surgically oriented anatomical descriptions. As such, this study aimed to provide a comprehensive guide to the microsurgical and endoscopic approaches to and through the orbit. METHODS Six formalin-fixed, latex-injected cadaveric head specimens were dissected in the surgical anatomy laboratory at the authors’ institution. In each specimen, the following approaches were modularly performed: endoscopic transorbital approaches (ETOAs), including a lateral transorbital approach and a superior eyelid crease approach; endoscopic endonasal approaches (EEAs), including those to the medial orbit and optic canal; and transcranial approaches, including a supraorbital approach, a fronto-orbital approach, and a 3-piece orbito-zygomatic approach. Each pertinent step was 3D photograph–documented with macroscopic and endoscopic techniques as previously described. RESULTS Endoscopic endonasal approaches to the orbit afforded excellent access to the medial orbit and medial optic canal. Regarding ETOAs, the lateral transorbital approach afforded excellent access to the floor of the middle fossa and, once the lateral orbital rim was removed, the cavernous sinus could be dissected and the petrous apex drilled. The superior eyelid approach provides excellent access to the anterior cranial fossa just superior to the orbit, as well as the dura of the lesser wing of the sphenoid. Craniotomy-based approaches provided excellent access to the anterior and middle cranial fossa and the cavernous sinus, except the supraorbital approach had limited access to the middle fossa. CONCLUSIONS This study outlines the essential surgical steps for major cranio-orbital and orbitocranial approaches. Endoscopic endonasal approaches offer direct medial access, potentially providing bilateral exposure to optic canals. ETOAs serve as both orbital access and as a corridor to surrounding regions. Cranio-orbital approaches follow a lateral-to-medial, superior-to-inferior trajectory, progressively allowing removal of protective bony structures for proportional orbit access.