Comprehensive Profiling of Secreted Factors in the Cerebrospinal Fluid of Moyamoya Disease Patients.

Moyamoya disease (MMD) is characterized by progressive occlusion of the intracranial internal carotid arteries, leading to ischemic and hemorrhagic events. Significant clinical differences exist between ischemic and hemorrhagic MMD. To understand the molecular profiles in the cerebrospinal fluid (CSF) of MMD patients, we investigated 62 secreted factors in both MMD subtypes (ischemic and hemorrhagic) and examined their relationship with preoperative perfusion status, the extent of postoperative angiographic revascularization, and functional outcomes. Intraoperative CSF was collected from 32 control and 71 MMD patients (37 ischemic and 34 hemorrhagic). Multiplex Luminex assay analysis showed that 41 molecules were significantly elevated in both MMD subtypes when compared to controls, including platelet-derived growth factor-BB (PDGF-BB), plasminogen activator inhibitor 1 (PAI-1), and intercellular adhesion molecule 1 (ICAM1) (p < 0.001). Many of these secreted proteins have not been previously reported in MMD, including interleukins (IL-2, IL-4, IL-5, IL-7, IL-8, IL-9, IL-17, IL-18, IL-22, and IL-23) and C-X-C motif chemokines (CXCL1 and CXCL9). Pathway analysis indicated that both MMD subtypes exhibited similar cellular/molecular functions and pathways, including cellular activation, migration, and inflammatory response. While neuroinflammation and dendritic cell pathways were activated in MMD patients, lipid signaling pathways involving nuclear receptors, peroxisome proliferator-activated receptor (PPAR), and liver X receptors (LXR)/retinoid X receptors (RXR) signaling were inhibited. IL-13 and IL-2 were negatively correlated with preoperative cerebral perfusion status, while 7 factors were positively correlated with the extent of postoperative revascularization. These elevated cytokines, chemokines, and growth factors in CSF may contribute to the pathogenesis of MMD and represent potential future therapeutic targets.

Radiosurgery as a microsurgical adjunct: outcomes after microsurgical resection of intracranial arteriovenous malformations previously treated with stereotactic radiosurgery.

OBJECTIVE: Microsurgical resection of arteriovenous malformations (AVMs) can be aided by staged treatment consisting of stereotactic radiosurgery followed by resection in a delayed fashion. This approach is particularly useful for high Spetzler-Martin (SM) grade lesions because radiosurgery can reduce flow through the AVM, downgrade the SM rating, and induce histopathological changes that additively render the AVM more manageable for resection. The authors present their 28-year experience in managing AVMs with adjunctive radiosurgery followed by resection. METHODS: The authors retrospectively reviewed records of patients treated for cerebral AVMs at their institution between January 1990 and August 2019. All patients who underwent stereotactic radiosurgery (with or without embolization), followed by resection, were included in the study. Of 1245 patients, 95 met the eligibility criteria. Univariate and multivariate regression analyses were performed to assess relationships between key variables and clinical outcomes. RESULTS: The majority of lesions treated (53.9%) were high grade (SM grade IV-V), 31.5% were intermediate (SM grade III), and 16.6% were low grade (SM grade I-II). Hemorrhage was the initial presenting sign in half of all patients (49.5%). Complete resection was achieved among 84% of patients, whereas 16% had partial resection, the majority of whom received additional radiosurgery. Modified Rankin Scale (mRS) scores of 0-2 were achieved in 79.8% of patients, and 20.2% had poor (mRS scores 3-6) outcomes. Improved (44.8%) or stable (19%) mRS scores were observed among 63.8% of patients, whereas 36.2% had a decline in mRS scores. This includes 22 patients (23.4%) with AVM hemorrhage and 6 deaths (6.7%) outside the perioperative period but prior to AVM obliteration. CONCLUSIONS: Stereotactic radiosurgery is a useful adjunct in the presurgical management of cerebral AVMs. Multimodal therapy allowed for high rates of AVM obliteration and acceptable morbidity rates, despite the predominance of high-grade lesions in this series of patients.

Treatment of posterior circulation fusiform aneurysms.

OBJECTIVE: Perforator arteries, the absence of an aneurysm discrete neck, and the often-extensive nature of posterior circulation fusiform aneurysms present treatment challenges. There have been advances in microsurgical and endovascular approaches, including flow diversion, and the authors sought to review these treatments in a long-term series at their neurovascular referral center. METHODS: The authors performed a retrospective chart review from 1990 to 2018. Primary outcomes were modified Rankin Scale (mRS) scores and Glasgow Outcome Scale (GOS) scores at follow-up. The authors also examined neurological complication rates. Using regression techniques, they reviewed independent and dependent variables, including presenting features, aneurysm location and size, surgical approach, and pretreatment and posttreatment thrombosis. RESULTS: Eighty-four patients met the inclusion criteria. Their mean age was 53 years, and 49 (58%) were female. Forty-one (49%) patients presented with subarachnoid hemorrhage. Aneurysms were located on the vertebral artery (VA) or posterior inferior cerebellar artery (PICA) in 50 (60%) patients, basilar artery (BA) or vertebrobasilar junction (VBJ) in 22 (26%), and posterior cerebral artery (PCA) in 12 (14%). Thirty-one (37%) patients were treated with microsurgical and 53 (63%) with endovascular approaches. Six aneurysms were treated with endovascular flow diversion. The authors found moderate disability or better (mRS score ≤ 3) in 85% of the patients at a mean 14-month follow-up. The GOS score was ≥ 4 in 82% of the patients. The overall neurological complication rate was 12%. In the regression analysis, patients with VA or PICA aneurysms had better functional outcomes than the other groups (p < 0.001). Endovascular strategies were associated with better outcomes for BA-VBJ aneurysms (p < 0.01), but microsurgery was associated with better outcomes for VA-PICA and PCA aneurysms (p < 0.05). There were no other significant associations between patient, aneurysm characteristics, or treatment features and neurological complications (p > 0.05). Patients treated with flow diversion had more complications than those who underwent other endovascular and microsurgical strategies, but the difference was not significant in regression models. CONCLUSIONS: Posterior circulation fusiform aneurysms remain a challenging aneurysm subtype, but an interdisciplinary treatment approach can result in good outcomes. While flow diversion is a useful addition to the armamentarium, traditional endovascular and microsurgical techniques continue to offer effective options.

Incidental De Novo Cerebral Microhemorrhages are Predictive of Future Symptomatic Macrohemorrhages After Surgical Revascularization in Moyamoya Disease.

BACKGROUND: Patients with moyamoya disease who develop incidental cerebral microhemorrhages (CMHs) on magnetic resonance imaging (MRI) have higher risk of developing subsequent symptomatic repeat macro hemorrhages. OBJECTIVE: To evaluate the effect of surgical revascularization on development of de novo CMHs and assess its correlation with repeat hemorrhage rates and functional outcome in hemorrhagic onset moyamoya disease (HOMMD). METHODS: We retrospectively reviewed a prospectively managed departmental database of all patients presenting with HOMMD treated between 1987 and 2019. The search yielded 121 patients with adequate MRI follow-up for inclusion into the study. RESULTS: In total, 42 preoperative CMHs were identified in 18 patients (15%). Patients presenting with preoperative CMH were more likely to develop de novo CMH after surgical revascularization. 7 de novo CHMs were identified in 6 patients (5%) on routine postoperative MRI at distinct locations from previous sites of hemorrhage or CMH. Symptomatic repeat macro hemorrhage was confirmed radiographically in 15 patients (12%). A total 5 (83%) of 6 patients with de novo CMHs later suffered symptomatic repeat macro hemorrhage with 4 of 5 (80%) hemorrhages occurring at sites of previous CMH. On univariate and multivariate analysis, de novo CMHs was the only significant variable predictive for developing repeat symptomatic hemorrhage. Development of delayed repeat symptomatic hemorrhage was prognostic for higher modified Rankin Score and therefore poorer functional status, whereas preoperative functional status was predictive of final outcome. CONCLUSION: De novo CMHs after surgical revascularization might serve as a radiographic biomarker for refractory disease and suggest patients are at risk for future symptomatic macro hemorrhage.

Clinical Course of Unilateral Moyamoya Disease.

BACKGROUND: The natural history of unilateral moyamoya disease (MMD) progressing to bilateral MMD remains an enigma in modern vascular neurosurgery. Few, small series with limited follow-up have reported relatively high rates of contralateral stenosis progression. OBJECTIVE: To review our large series of unilateral MMD patients and evaluate radiographic and surgical progression rates, and identify any factors associated with progression. METHODS: We included all unilateral MMD cases treated from 1991 to 2017 in an observational study. We examined time to contralateral radiographic progression and contralateral progression requiring surgery. Using Cox regression analysis, we evaluated factors potentially associated with contralateral progression. RESULTS: There were 217 patients treated for unilateral MMD. About 71% were female, and the average age at first surgery was 33.8 yr. Average follow-up was 5.8 yr (range 1-22 yr). A total of 18 patients (8.3%) developed contralateral progression. And 8 of these (3.7%) developed progression requiring bypass surgery. Baseline stenosis and hyperlipidemia (HLD) were significantly associated with radiographic progression (hazard ratio [HR] = 9.7, P = .006; HR = 4.0, P = .024). Baseline stenosis was associated with surgical progression (HR = 44.2, P = .002). Results were similar when controlling for possible confounders using multivariate regression. CONCLUSION: Previous series showed relatively high rates of progression in unilateral MMD (15%-30%), but these studies were small and long-term follow-up was rarely available. Our large series indicates that the rate of progression is lower than previously reported but still warrants yearly noninvasive screening. These data may provide indirect support for statin therapy in MMD.

Translamina Terminalis Approach to Laser-Assisted Resection of Thalamomesencephalic Cavernous Malformation.

Cavernous malformations of the midbrain require careful consideration of the risks and benefits of intervention as well as the optimal surgical approach for these challenging lesions. Excellent results can be achieved with careful surgical planning and technique. We demonstrate a contralateral left pterional craniotomy for a translamina terminalis approach to carbon dioxide laser-assisted microsurgical resection of a thalamomesencephalic cavernoma in a 59-year-old woman with progressive debilitating diplopia secondary to partial third nerve palsy (Video 1). We performed a contralateral left modified pterional craniotomy in which we limited dissection of the temporalis muscle to approximately one third rather than extending the muscle split down to the zygoma. The cavernous malformation was resected with no complications, and the patient was discharged from the hospital on postoperative day 3. She noted immediate improvement and nearly complete resolution of symptoms over ensuing weeks. This approach offers a direct route to the lesion with minimal brain transgression, while avoiding the critical structures within the interpeduncular cistern, including the basilar artery and thalamomesencephalic perforating arteries, as well as bordering neural structures, including cerebral peduncles, oculomotor nerves, and mamillary bodies. Use of the carbon dioxide laser with its 0.55-mm tip offers a low surgical profile and allows for precise cutting, thus minimizing thermal damage to surrounding tissues. The translamina terminalis approach through a pterional craniotomy offers a safe and potentially less morbid alternative to select thalamomesencephalic lesions compared with exposure through the mesencephalic surface, which in our experience often necessitates an orbitozygomatic craniotomy.

Contralateral Vasospasm in an Uncomplicated Elective Anterior Communicating Artery Aneurysm Clipping.

BACKGROUND: Cerebral vasospasm following clipping of an unruptured aneurysm is a rare phenomenon. When it does occur, cerebral vasospasm usually occurs on the side ipsilateral to the surgical intervention. CASE DESCRIPTION: A 68-year-old man underwent right-sided pterional craniotomy for clipping of an unruptured anterior communicating artery aneurysm and experienced contralateral vasospasm 5 days later. CONCLUSIONS: We further discuss the pathophysiology underlying vasospasm after uncomplicated craniotomy and nonhemorrhagic aneurysm clipping.

Pregnancy after direct cerebral bypass for moyamoya disease.

OBJECTIVE: Moyamoya disease (MMD) disproportionately affects young to middle-aged women. The main treatment for this challenging disease is cerebral bypass surgery. Vascular neurosurgeons often need to counsel women regarding pregnancy following bypass for MMD, but there is a paucity of data. The authors set out to examine neurological and obstetric outcomes in an extensive cohort of MMD patients who had pregnancies following cerebral revascularization at the Stanford Medical Center. METHODS: The authors identified all patients at their institution who underwent cerebral bypass for MMD from 1990 through 2018 and who later became pregnant. Some of these patients also had pregnancies prior to undergoing bypass surgery, and the authors examined these pregnancies as well. They performed a chart review and brief telephone survey to identify obstetric complications, transient ischemic attacks (TIAs), and strokes. Neurological and obstetric outcomes were compared to published rates. They also compared pre- and post-bypass pregnancy complication rates using logistic regression techniques. RESULTS: There were 71 pregnancies among 56 women whose mean age was 30.5 years. Among 59 post-bypass pregnancies, there were 5 (8%) perinatal TIAs. There were no MRI-confirmed strokes or strokes with residual deficits. Among 12 pre-bypass pregnancies, there were 3 (25%) TIAs and 2 (17%) MRI-confirmed strokes. There were no hemorrhagic complications in either group. In the generalized estimating equations analysis, performing cerebral revascularization prior to pregnancy versus after pregnancy was associated with lower odds of perinatal stroke or TIA (OR 0.15, p = 0.0061). Nine pregnancies (13%) were complicated by preeclampsia, and there was one (1%) instance of eclampsia. The overall rate of cesarean delivery was 39%. There were 2 miscarriages, both occurring in the first trimester. There were no maternal deaths. CONCLUSIONS: The authors present neurological and obstetric outcomes data in a large cohort of MMD patients. These data indicate that post-bypass pregnancy is accompanied by low complication rates. There were no ischemic or hemorrhagic strokes among post-bypass pregnant MMD patients. The rate of obstetric complications was low overall. The authors recommend close collaboration between the vascular neurosurgeon and the obstetrician regarding medical management, including blood pressure goals and continuation of low-dose aspirin.

Mobile Applications in Neurosurgery: A Systematic Review, Quality Audit, and Survey of Canadian Neurosurgery Residents.

BACKGROUND: In the past decade, smartphone applications (Apps) have experienced remarkable development across all fields of medicine, including neurosurgery. However, owing to a lack of regulatory oversight and peer review, a clear need exists for a comprehensive review and audit of the existing available Apps. In the present study, we systematically reviewed the existing mobile Apps in neurosurgery, evaluated their clinical use by neurosurgery residents in Canada, and performed a quality audit of the most popular Apps. METHODS: Indexed Apps were identified from either the Google Play Store or the iOS App Store using a comprehensive list of keywords related to neurosurgery. A subsequent cross-sectional survey of 76 Canadian neurosurgery residents was conducted, including a section on smartphone App use. We next evaluated the most popular Apps among the residents using the Healthcare Smartphone App Evaluation Tool and performed a quality audit of their content using established medical references. RESULTS: The survey identified 118 mobile Apps related to neurosurgery. The 3 most used Apps used by the current cohort of Canadian neurosurgery residents were Neurosurgery Survival Guide, Neuromind, and the Journal of Neurosurgery App. Each of these 3 Apps received an excellent score on the Healthcare Smartphone App Evaluation Tool. A quality audit of 30 pages of the Neurosurgery Survival Guide and 40 clinical scores of the Neuromind App, performed by 10 neurosurgery residents, failed to reveal inaccurate or false statements. CONCLUSION: The present study has highlighted the current landscape of neurosurgery mobile Apps and their use among neurosurgery residents.

Microsurgical rhizotomy for trigeminal neuralgia in MS patients: technique, patient satisfaction, and clinical outcomes.

OBJECTIVEPatients with multiple sclerosis (MS)-associated trigeminal neuralgia (TN) have higher recurrence and retreatment rates than non-MS patients. The optimal management strategy and role for microsurgical rhizotomy (MSR) for MS-TN remains to be determined. The aim of this study was to report time to treatment failure (TTF) and pain scores following MSR compared to percutaneous and Gamma Knife procedures.METHODSTime to treatment failure was analyzed after MSR (n = 14) versus prior procedures (n = 53) among MS-TN patients. Kaplan-Meier curves and log-rank test were utilized to compare TTF after MSR versus prior procedures using the same cohort of patients as their own control group. Subsequent analysis compared TTF after MSR to TTF after 93 other procedures among a second cohort of 18 MS-TN patients not undergoing MSR. BNI pain scores were compared between MSR and other procedures among the MS-TN cohort using a chi-square test.RESULTSTTF was significantly longer after MSR than after other procedures in the MSR cohort (median TTF 79 vs 10 months, respectively, p < 0.0001). Similarly, TTF was longer after MSR than after prior procedures in the non-MSR cohort (median TTF 79 vs 13 months, respectively, p < 0.001). MSR resulted in a higher proportion of excellent pain scores when compared to other procedures in the non-MSR cohort (77% vs 29%, p < 0.001). Probability of treatment survival was higher after MSR than after other procedures at all time points (3, 6, 12, 24, 36, and 48 months). There were no deaths or major complications after MSR.CONCLUSIONSTTF was significantly longer following MSR compared to prior procedures in MS-TN patients. Additionally, a higher proportion of patients achieved excellent BNI pain scores after MSR.

Smartphone Usage Patterns by Canadian Neurosurgery Residents: A National Cross-Sectional Survey.

BACKGROUND: Smartphones and their apps are used ubiquitously in medical practice. However, in some cases their use can be at odds with current patient data safety regulations such as Canada's Personal Health Information Protection Act of 2004. To assess current practices and inform mobile application development, we sought to better understand mobile device usage patterns among Canadian neurosurgery residents. METHODS: Through the Canadian Neurosurgery Research Collaborative, an online survey characterizing smartphone ownership and usage patterns was developed and sent to all Canadian neurosurgery resident in April of 2016. Questionnaires were collected and completed surveys analyzed. RESULTS: Of 146 eligible residents, 76 returned completed surveys (52% response rate). Of these 99% of respondents owned a smartphone, with 79% running on Apple's iOS. Four general mobile uses were identified: 1) communication between members of the medical team, 2) decision support, 3) medical reference, and 4) documentation through medical photography. Communication and photography were areas where the most obvious breaches in the Canadian Personal Health Information Protection Act were noted, with 89% of respondents taking pictures of patients' radiologic studies and 75% exchanging them with Short Message System. Hospital policies had no impact on user behaviors. CONCLUSIONS: Smartphones are used daily by most neurosurgery residents. Identified usage patterns are associated with perceived gains in efficacy and challenges in privacy and data reliability. We believe creating and improving workflows that address these usage patterns has a greater potential to improve privacy than changing policies and enforcing regulations.

Long-term follow-up of multimodality treatment for multiple sclerosis-related trigeminal neuralgia.

BACKGROUND: The treatment for multiple sclerosis-related trigeminal neuralgia (MS-TN) is less efficacious and associated with higher recurrence rates than classical TN. No consensus has been reached in the literature on the choice procedure for MS-TN patients. The aim of this study was to assess the incidence and surgical outcomes of medically refractory MS-TN. METHODS: Patient records were retrospectively reviewed for all Manitobans undergoing first procedure for medically refractory MS-TN between 2000 and 2014. Subsequent procedures were then recorded and analyzed in this subgroup of patients. The primary outcome measure was time to treatment failure. RESULTS: The incidence of medically refractory MS-TN was 1.2/million/year. Twenty-one patients with 26 surgically treated sides underwent first rhizotomy including 13 GammaKnife and 13 percutaneous rhizotomies comprised of ten glycerol injections and three balloon compressions. Subsequent procedures were required on 23 sides (88%), including 24 GammaKnife, 19 glycerol injections, 25 balloon compressions, two microvascular decompressions, and four open partial surgical rhizotomies with a total of 99 surgeries on 26 sides (range, 1-12 each). CONCLUSIONS: The majority of MS-TN patients become medically refractory and require multiple repeat surgical procedures. MS-TN procedures were associated with high rates of pain recurrence and our data suggests reoperation within 1 year is often necessary. Optimal management strategy in this patient population remains to be determined. Patients need to be counseled on managing expectations as treatments commonly afford only temporary relief.

Demographics, Interests, and Quality of Life of Canadian Neurosurgery Residents.

BACKGROUND: Neurosurgical residents face a unique combination of challenges, including long duty hours, technically challenging cases, and uncertain employment prospects. We sought to assess the demographics, interests, career goals, self-rated happiness, and overall well-being of Canadian neurosurgery residents. METHODS: A cross-sectional survey was developed and sent through the Canadian Neurosurgery Research Collaborative to every resident enrolled in a Canadian neurosurgery program as of April 1, 2016. RESULTS: We analyzed 76 completed surveys of 146 eligible residents (52% response rate). The median age was 29 years, with 76% of respondents being males. The most popular subspecialties of interest for fellowship were spine, oncology, and open vascular neurosurgery. The most frequent self-reported number of worked hours per week was the 80- to 89-hour range. The majority of respondents reported a high level of happiness as well as stress. Sense of accomplishment and fatigue were reported as average to high and overall quality of life was low for 19%, average for 49%, and high for 32%. Satisfaction with work-life balance was average for 44% of respondents and was the only tested domain in which significant dissatisfaction was identified (18%). Overall, respondents were highly satisfied with their choice of specialty, choice of program, surgical exposure, and work environment; however, intimidation was reported in 36% of respondents and depression by 17%. CONCLUSIONS: Despite a challenging residency and high workload, the majority of Canadian neurosurgery residents are happy and satisfied with their choice of specialty and program. However, work-life balance, employability, resident intimidation, and depression were identified as areas of active concern.

Extensive Mirror-Image Neurofibromas of Entire Spine Resulting in Spastic Tetraplegia.

Neurofibromatosis 1 (NF1) is associated with increased incidence of spinal tumors including neurofibromas. The majority of NF1-associated spine neurofibromas are asymptomatic; however, a minority of patients will experience neurologic symptoms that can range from mild paresthesia, radiculopathy, myelopathy, and focal weakness to quadriplegia in extreme cases. We present a 21-year-old male diagnosed with NF1 in infancy and followed for multiple mirror-image neurofibromas involving the entire spine. He was asymptomatic until age 14 when he developed neck pain and progressive tetraplegia with magnetic resonance imaging showing severe cord compression secondary to bilateral C2 neurofibromas. Emergent cervical decompression was performed at C1-C3 along with debulking of bilateral neurofibromas. Postoperatively he regained full strength with no signs of myelopathy several years postoperatively. This case demonstrates a dramatic neuroimaging finding and emphasizes the potential for significant neurologic deterioration in previously asymptomatic NF1 patients, highlighting the need for long-term follow-up.

Trigeminal neuropathy associated with an enlarging arachnoid cyst in Meckel's cave: case report, management strategy and review of the literature.

We describe a rare case and novel management strategy of painful trigeminal neuropathy caused by an arachnoid cyst confined to Meckel's cave. A 57-year-old female presented with several years of progressive trigeminal pain and signs of trigeminal deafferentation, including sensory loss, corneal anesthesia and mastication muscle atrophy. Medical treatment with carbamazepine provided partial and temporary pain control. Surgical treatment was eventually performed by aspiration of the arachnoid cyst through the foramen ovale using a percutaneous approach. The patient experienced relief of pain and improvement of numbness and muscle strength. To our knowledge, this is the first case description of a percutaneous drainage of a Meckel's cave arachnoid cyst.

Does preoperative depression predict post-operative surgical pain: A systematic review.

BACKGROUND: As surgical procedures have been developed and refined, determining which factors predict rapid and successful surgical outcomes has become a priority. Significant psychosocial influences on surgical outcomes have been found with numerous procedures. The objective of this study is to perform a systematic review of randomized-control trials and observational studies to examine the relationships between pre-operative depression and post-operative (<6 weeks) pain outcomes. MATERIALS AND METHODS: Pubmed/MEDLINE, EMBASE, CINAHL and Web of Science were searched for studies published from January 1, 2006 and August 31, 2016. Two independent reviewers assessed the eligibility of each report based on predefined inclusion criteria (study design, measure of pre-operative depression, and post-operative pain). Participants included adult patients undergoing surgical procedures diagnosed with depression pre-operatively. Patients were assessed for post-operative pain via pain scales and use of post-operative pain medications. Data was summarized qualitatively due to limitations of comparability and transformation. Significant clinical and statistical heterogeneity of the included studies was identified. RESULTS: Of 1091 abstracts reviewed, 18 studies met the inclusion criteria. Due to the significant clinical and statistical heterogeneity, a meta-analysis was not performed. 8 studies (comprising a total of 1314 patients) reported a statistically significant effect of pre-operative depression on post-operative pain. 10 studies encompassing a total 1226 patients failed to demonstrate a statistically significant effect of depression on postoperative pain. CONCLUSION: The analysis of results was limited to a systematic review and qualitative analysis of the eligible studies. Based on this systematic review we identified 8 studies reporting a statistically significant effect of pre-operative depression on post-operative pain and 10 studies reporting no statistically significant effect of pre-operative depression on post-operative pain. Therefore, the quality of presented data is poor and makes it challenging to answer further questions. Large epidemiologic studies in this field are needed to provide further evidence.

Operative Landscape at Canadian Neurosurgery Residency Programs.

Background Currently, the literature lacks reliable data regarding operative case volumes at Canadian neurosurgery residency programs. Our objective was to provide a snapshot of the operative landscape in Canadian neurosurgical training using the trainee-led Canadian Neurosurgery Research Collaborative. METHODS: Anonymized administrative operative data were gathered from each neurosurgery residency program from January 1, 2014, to December 31, 2014. Procedures were broadly classified into cranial, spine, peripheral nerve, and miscellaneous procedures. A number of prespecified subspecialty procedures were recorded. We defined the resident case index as the ratio of the total number of operations to the total number of neurosurgery residents in that program. Resident number included both Canadian medical and international medical graduates, and included residents on the neurosurgery service, off-service, or on leave for research or other personal reasons. RESULTS: Overall, there was an average of 1845 operative cases per neurosurgery residency program. The mean numbers of cranial, spine, peripheral nerve, and miscellaneous procedures were 725, 466, 48, and 193, respectively. The nationwide mean resident case indices for cranial, spine, peripheral nerve, and total procedures were 90, 58, 5, and 196, respectively. There was some variation in the resident case indices for specific subspecialty procedures, with some training programs not performing carotid endarterectomy or endoscopic transsphenoidal procedures. CONCLUSIONS: This study presents the breadth of neurosurgical training within Canadian neurosurgery residency programs. These results may help inform the implementation of neurosurgery training as the Royal College of Physicians and Surgeons residency training transitions to a competence-by-design curriculum.