Background: Surgeons’ bimanual dexterity may correlate with the surgical outcome. Continuous assessment of psychomotor performance enables action-oriented feedback and error avoidance guidance. We outline an artificial intelligence (AI) application to continuously assess surgical bimanual skills and its predictive validation on surgical trainee performance throughout a neurosurgery residency program. Methods: Participants (n=50, 14 experts/neurosurgeons, 14 senior residents, 10 junior residents, 12 novices/medical students) performed two simulated subpial tumour resections a total of 300 times. A deep neural network was developed using expert/neurosurgeon and novice/medical student data to score bimanual performance at 0.2-second intervals between a score of 1.00 and -1.00. An average score was calculated for each task. Results: The average performance score differentiated among four expertise levels, p<.001. Neurosurgeons scored significantly higher than senior residents (p=.045) and junior residents scored significantly higher than medical students (p=.04). The intelligent system also differentiated between senior and junior trainee levels (p=.004). The performance score linearly correlated with resident year of neurosurgical training (adjusted R2=27.7%). Conclusions: The AI-powered intelligent system outlined is the first expert surgeon-data-based technical skills continuous assessment system, with predictive validity throughout a neurosurgical residency program. Intelligent systems may aid in the competency-based approach in surgery by accurately assessing trainee skills.

Background: Melanocytic tumors of the central nervous system (CNS) such as meningeal melanoma are exceedingly rare tumours derived from leptomeningeal melanocytes. Primary meningeal melanomas account for 0.1% of intracranial neoplasms with an incidence of approximately 0.5 per 10 million. Methods: We report the case of a previously healthy 47 year old male who presented with bilateral tonic-clonic seizure. Magnetic resonance imaging (MRI) demonstrated a homogenously-enhancing right temporal extra-axial lesion. The patient was stabilized on anti-epileptic medications and dexamethasone prior to proceeding with complete surgical resection of the lesion. Review of the current literature was conducted. Results: Macroscopically, the extra-axial lesion was heavily pigmented with invasion of the surrounding dura and skull. Histopathology revealed a poorly differentiated neoplasm with nuclear atypia and melanin-containing cells with strong SOX10 positivity and variable S100 positivity. Systemic workup was negative including absent ocular or cutaneous melanomas. Oncopanel was negative including absent BRAF mutation. He began checkpoint inhibitor therapy and subsequently developed cerebral venous sinus thrombosis (CVST) managed with anticoagulation. At 6 month follow-up, he was neurologically intact, working full-time, and had resumed immunotherapy. Conclusions: Primary intracranial melanoma is a rare tumour that can appear radiographically similar to meningioma. Surgical resection remains the mainstay of therapy for best long-term prognosis.

Background: A 19-month-old boy with recent Wilms tumor resection presented with ASIA B spinal cord injury secondary to rapid progression of a T12 epidural lesion suspicious for metastatic disease. Methods: The case is presented and the literature was reviewed for prior cases of Wilms tumor with spinal metastasis. Results: Emergent tumor debulking for spinal cord decompression via T11-L1 laminectomies with right T11-L1 facetectomies was performed. Allograft bone was placed to facilitate fusion. No direct connection to the renal tumor was appreciated on imaging or intra-operatively. There was no evidence of additional metastases. Pathology demonstrated similar histomorphology and immunohistochemical profile as the original left kidney tumor resection (Wilms tumor, favorable histology). Notably, no focal or diffuse anaplasia, or aggressive non-Wilms component such as clear cell sarcoma or rhabdoid tumor of the kidney, were identified. Treatment plan consisted of 25 Gy of radiation and 29 weeks of chemotherapy. At 6-weeks the patient had regained baseline lower extremity function with no bowel or bladder dysfunction. Conclusions: Spinal cord compression secondary to spinal metastasis of Wilms tumor in the absence of global metastatic disease is rare. Prompt identification, surgical decompression, and multimodality therapy is essential to prevent persistent neurological deficits.

Background: Gangliocytomas are rare neuronal tumors with an incidence of less than 1% of all CNS neoplasms. They are mostly seen in the pediatric age group, localizing within the cerebral cortex, most often the temporal lobe. Methods: We report a case of an intracranial gangliocytoma arising within the lateral ventricle in an adult patient. Our 66-year-old female patient started experiencing progressive generalized weakness, headaches, and confusion prior to presentation. Her neurological examination did not reveal any focal neurological deficits. MRI of the brain showed a diffusely enhancing lobulated mass situated within the frontal horn of the right lateral ventricle with extension into the foramen of Monro and obstructive hydrocephalus. Results: The patient underwent an interhemispheric trans-callosal approach with gross total resection and relief of her hydrocephalous. Pathological examination showed clusters of highly pleomorphic neuron-like cells without evidence of neoplastic glial cells. Histopathological and immunohistochemistry findings were consistent with the diagnosis of gangliocytoma (World Health Organization grade 1). Conclusions: Gangliocytomas are rare low-grade CNS neoplasms that can present in an older population within unusual locations and should be included within the differential whenever a suspicious lesion is encountered.

Background: Intracranial dural arteriovenous fistulas (DAVF) are relatively rare vascular malformations. While the pathophysiology of their formation is unknown, they are believed to be acquired lesions related to intracranial venous hypertension and dura sinus thrombosis. There have been rare reports of intracranial tumors associated with DAVF. Here we complete a systematic search of the literature. Methods: A systematic PRISMA search of the literature was conducted to identify papers in which an intracranial tumor was associated with sinus thrombosis and DAVF. 24 relevant studies were identified and analyzed, along with a case illustration. Results: A total of 38 cases of DAVF formation with concomitant intracranial tumor were identified. The median age was 60, the majority of tumors being meningiomas (71%), and involved primarily the transverse sigmoid sinus (52%) and superior sagittal sinus (16%). The most cases involved an occlusion (39%) or partial occlusion (24%) of the related sinus. The DAVF were classified as Borden Types I (35%), II (32%) or III (24%). Endovascular treatment was the most common intervention (56%), followed by a combined approach (28%) vs surgery alone (16%), all reporting resolution. Conclusions: This highlights that DAVFs can be rarely associated with intracranial tumors, and highlights the patterns of these lesions and their treatments.

Background: Brain metastases are frequently seen in neurosurgical practice. Standardised criteria are created to better classify these common pathologies in research studies. This study’s goal was to evaluate RANO-BM criteria’s current thresholds in a cohort of patients with brain metastases managed by SRS. Methods: We performed a retrospective metastasis-level analysis of patients treated with SRS for brain metastases. The data collected included cohort demographics, metastases characteristics, outcomes, and the rate of true positives, false negatives, true negatives and false positives as defined by RANO-BM criteria at last follow-up before second SRS. Results: 251 metastases in 50 patients were included in the analysis. RANO-BM criteria using current thresholds yielded a sensitivity of 38%, a specificity of 95%, a positive predictive value of 71% and a negative predictive value of 84%. Modified RANO-BM criteria using absolute diameter differences of 2.5 mm yielded a sensitivity of 83%, a specificity of 87%, a positive predictive value of 67% and a negative predictive value of 94%. Pseudoprogression occurred significantly earlier than tumor progression, with a median time of onset of 6.9 months and 12.1 months respectively. Conclusions: Current RANO-BM criteria unreliably identifies clinically relevant tumor progression, but are useful in assessing diameter increases caused by tumor progression and pseudoprogression.

Background: Delayed Cerebral Ischemia (DCI) is a complication of aneurysmal subarachnoid hemorrhage (aSAH) and is associated with significant morbidity and mortality. A paucity of high-quality evidence is available to guide the management of DCI. As such, our objective was to evaluate practice patterns of Canadian physicians regarding the management of aSAH and DCI. Methods: The Canadian Neurosurgery Research Collaborative (CNRC) performed a cross-sectional survey of Canadian neurosurgeons, intensivists, and neurologists who manage aSAH. The survey was distributed to members of the Canadian Neurosurgical and Neurocritical Care Societies, respectively. Responses were analyzed using quantitative and qualitative methods. Results: The response rate was 129/340 (38%). Agreement among respondents included the need for intensive care unit admission, use of clinical and radiographic monitoring, and prophylaxis for prevention of DCI. Indications for starting hyperdynamic therapy varied. There was discrepancy in the proportion of patients felt to require intravenous milrinone, intra-arterial vasodilators, or physical angioplasty for treatment of DCI. Most respondents reported their facility does not utilize a standardized definition for DCI. Conclusions: DCI is an important clinical entity for which no consensus exists in management among Canadian practitioners. The CNRC calls for the development of national standards in the diagnosis and management of DCI.

Background: Poorly-defined cases (PDCs) of focal epilepsy are cases with no/subtle MRI abnormalities or have abnormalities extending beyond the lesion visible on MRI. Here, we evaluated the utility of Arterial Spin Labeling (ASL) MRI perfusion in PDCs of pediatric focal epilepsy. Methods: ASL MRI was obtained in 25 consecutive children presenting with poorly-defined focal epilepsy (20 MRI- positive, 5 MRI-negative). Qualitative visual inspection and quantitative analysis with asymmetry and Z-score maps were used to detect perfusion abnormalities. ASL results were compared to the hypothesized epileptogenic zone (EZ) derived from other clinical/imaging data and the resection zone in patients with Engel I/II outcome and >18 month follow-up. Results: Qualitative analysis revealed perfusion abnormalities in 17/25 total cases (68%), 17/20 MRI-positive cases (85%) and none of the MRI-negative cases. Quantitative analysis confirmed all cases with abnormalities on qualitative analysis, but found 1 additional true-positive and 4 false-positives. Concordance with the surgically-proven EZ was found in 10/11 cases qualitatively (sensitivity=91%, specificity=50%), and 11/11 cases quantitatively (sensitivity=100%, specificity=23%). Conclusions: ASL perfusion may support the hypothesized EZ, but has limited localization benefit in MRI-negative cases. Nevertheless, owing to its non-invasiveness and ease of acquisition, ASL could be a useful addition to the pre-surgical MRI evaluation of pediatric focal epilepsy.

Background: Gaze behavior differences between expert and novice surgeons have been established in general surgery literature. Limited information is available about surgeon’s visual attention during microsurgery procedures where surgical microscope is used. Methods: 4 experts and 3 novices performed 37 independent sutures under the surgical microscope. Eye movements of surgeons and scene video of the surgical performance were recorded. Total suturing time and subtask times were compared between level of expertise. We defined three discrete surgical actions and examined eye gaze (fixation) directly related to each of these actions. Fixation duration (total, pre-action,and post-action duration) were compared between expert and novice, over 3 subtasks (piercing, exiting and cutting) and between pre- and post-action phases. Results: Expert surgeons completed the suture with shorter total time and displayed longer fixation time than novices. Experts also maintained their visual engagement constantly over the 3 level of subtask in comparison to novices who required a longer fixation time for the challenging subtask (piercing). Experts use longer pre- than post-action fixation, and this pattern is distributed over all three subtasks. This gaze engagement strategy was not shown in novices. Conclusions: The action-related fixation can be used to evaluate microsurgeons’ level of expertise and in surgical education for gaze training.

Background: Mastery of microsurgical skills requires regular hands-on practice. Simulation is increasingly recognized as an important supplement to operative training experience. The live rat femoral artery model is the gold standard model for microneurosurgical skills simulation. We present an 11-year experience incorporating simulation-based microsurgical training into an established Canadian neurosurgery program. Methods: Postgraduate year 2 (PGY-2) neurosurgery residents completed a one-year curriculum spanning 17 training sessions divided into 5 modules of increasing fidelity. Both perfused duck wing and live rat vessel training modules were used. Three modules comprised live microvascular anastomosis. Trainee performance was video recorded and blindly graded using the Objective Structured Assessment of Technical Skills Global Rating Scale. Results: Eighteen participants completed 107 microvascular anastomoses. There was significant improvement in six measurable skills during the curriculum. Mean overall score was significantly higher on the fifth attempt compared to the first attempt for all 3 live anastomotic modules (p<0.001). Each module had a different improvement profile across the skills assessed. The greatest improvement was observed during artery-to-artery anastomosis. Conclusions: This high-fidelity microsurgical simulation curriculum demonstrated a significant improvement in the six microneurosurgical skills assessed, supporting its use as an effective teaching model. Transferability to the operative environment is actively being investigated.

Background: The Canadian Medical Student Interest Group in Neurosurgery (CaMSIGN) is the first neurosurgery platform of its kind in Canada. Methods: In this retrospective study, data from CaMSIGN’s online platforms have been collated from February 2021 to the present and analyzed to show trends in user engagement. Results: CaMSIGN events generated 1,575 views on YouTube (384 from Canada). The total watch time was 170.3 hours, of which 43.9 hours were Canadian (28.5%). The total views normalized by the total number of students interested in neurosurgery was 17.12 hours. The normalized Canadian view was 4.17. 717 people follow the CaMSIGN Facebook account (normalized= 7.79). 152 people follow our Instagram (normalized= 1.65). 338 people follow our Twitter (normalized= 3.67). This number is comparable to that of estimated practicing neurosurgeons in Canada (333). A total of 32,974 people visited the Twitter page, with a monthly average of 2747.8. Lastly, the campaign website has had 5,811 visitors since its launch in June 2021 with a monthly average of 695.57 visitors. The number of website visitors has increased at a rate of 3.1327 visitors/month. Conclusions: Through this initiative, our aim has been to model a pan-Canadian approach to neurosurgery.

Background: Despite a higher prevalence of traumatic spinal cord injury (TSCI) amongst Canadian Indigenous peoples, there is a paucity of studies focused on Indigenous TSCI. We present the first Canada-wide study comparing TSCI amongst Canadian Indigenous and non-Indigenous peoples. Methods: This study is a retrospective analysis of prospectively-collected TSCI data from the Rick Hansen Spinal Cord Injury Registry (RHSCIR) from 2004-2019. We divided participants into Indigenous and non-Indigenous cohorts and compared them with respect to demographics, injury mechanism, level, severity, and outcomes. Results: Compared with non-Indigenous patients, Indigenous patients were younger, more female, less likely to have higher education, and less likely to be employed. The mechanism of injury was more likely due to assault or transportation-related trauma in the Indigenous group. The length of stay for Indigenous patients was longer. Indigenous patients were more likely to be discharged to a rural setting, less likely to be discharged home, and more likely to be unemployed following injury. Conclusions: Our results suggest that more resources need to be dedicated for transitioning Indigenous patients sustaining a TSCI to community living and for supporting these patients in their home communities. A focus on resources and infrastructure for Indigenous patients by engagement with Indigenous communities is needed.

Background: Tubular retractors are FDA approved and in the Neurosurgical marketplace, but adaptation has been hampered by lack of evidence showing superiority over traditional retractors when performing subcortical surgery. This study examines brain injury associated with traditional brain retractors versus tubular retractors. Methods: Nine porcine models underwent a simulated neurosurgical operation. Retractors were inserted for four hours after which the porcine model was euthanized. The en-bloc extracted porcine brain was fixed in 10% formalin, paraffin embedded, sectioned at 4 um and stained with hematoxylin and eosin (H&E) using standard laboratory protocols. Computer algorithms were generated to calculate areas of cerebral edema and hemorrhage adjacent to retractor surfaces. Results: Using a two-tailed t-test with a significance level of 0.05, traditional brain retractors were associated with statistically significantly greater cerebral edema when compared to tubular retractors (17.36 um2 vs. 12.42 um2; p = 0.0038). There was no statistically significant difference in mean areas of hemorrhage between traditional brain retractors and tubular retractors noted (3.43 um2 vs 3.60 um2; p = 0.8297). Conclusions: Tubular retractors are associated with significantly less edema in surrounding brain than traditional retractors. On histopathological merits, this study supports the application of tubular retractors over traditional retractors.

Background: A 3-year-old girl presented with a 6-day history of severe headaches. On examination, upper motor neuron signs were noted in the left upper and lower extremities with increased tone, reflexes, and a positive Babinski sign. MRI of the brain revealed a giant right middle cerebral artery (MCA) aneurysm with significant mass effect, associated with cerebral edema and ventricular effacement. CT and CT angiogram showed evidence of aneurysmal wall calcification and lamellar thrombosis within the aneurysmal sac. In addition, there was a smaller right MCA aneurysm in close proximity to the giant aneurysm. Methods: After a balloon occlusion test to assess collateral blood flow to the MCA territory, it was decided to treat both aneurysms with a flow diverting stent. Dual antiplatelet loading was done with aspirin and clopidogrel. The smallest available diameter of Pipeline Shield stent was deployed. Results: The patient remained neurologically unchanged. Early follow-up imaging demonstrated stent patency, reduced size and mass effect of the large aneurysm, reduced cerebral edema, and no flow into the smaller aneurysm. Conclusions: Flow diversion stenting may be employed successfully in pediatric patients, though has unique technical considerations including small size vessels and limited evidence for antiplatelet agent choice and dosing.

Background: Type 1 spinal arteriovenous malformations (AVM) are dural fistulas which classically present due to progressive congestive myelopathy. Acute hemorrhage resulting in a spinal subdural hematoma is exceedingly rare with only three reported cases. Methods: This 46-year-old female experienced rapidly progressive paraplegia over several hours. There was no history of anti-coagulant use, trauma, fever, or infection. On examination, she had 0/5 in the lower extremities bilaterally and decreased sensation to pinprick below the T6 level on both sides. She also had loss of bowel and bladder control. MRI demonstrated evidence of an intra-dural extramedullary lesion located anteriorly causing significant compression on the spinal cord from T4 down to T7 level. Results: She underwent thoracic laminectomy from T4 – T7. After dural opening, a well organized sub-dural hematoma with significant mass effect on a distorted spinal cord was evacuated. Subsequently, a large abnormal artery leading into a dilated serpiginous vein on the dorsal aspect of spinal cord at the T7 level was visualized. Indocyanine green angiography confirmed our suspicion of a dural arteriovenous fistula which was disconnected. Conclusions: Type I spinal AVM in rare cases can present acutely as subdural hematoma and should be kept in the differential diagnosis for acute paraplegia.

Background: Embolization of middle meningeal artery (EMMA) is an emerging treatment for CSDH and a method to decrease CSDH recurrence. We report a single Canadian center experience of EMMA for the management of CSDH. Methods: Consecutive EMMA patients during the period July 2020 to September 2021 were retrospectively included in this series. EMMA procedures were performed using polyvinyl alcohol particles or liquid embolic agent. All patients were followed clinically and radiographically as per standard of care. Results: A total of 20 patients CSDH (mean 65.6 years; range 14-85 yrs; male 16) underwent 20 EMMA procedures. CSDH occured on the left in 13 patients, right in 4 patients and bilateral in 3 patients. No patients had periprocedural complications. There was no recurrence of CSDH on the EMMA treated side. The mean SDH size decreased from 18.4 +/- 6.34 mm at the time of presentation to 5.31 +/ 3.84 mm at last follow up. The proportion of patients with an mRS of 2 or less increased from 65% to 76%. Conclusions: EMMA was found to be effective and safe in the management of CSDH with no evidence of recurrence on the treated side. Left sided hematomas appear to be more common that right sided hematomas.

Background: Chronic subdural hematoma (CSDH), although common in the adult and geriatric populations, is a relatively rare condition in pediatric patients. Middle meningeal artery (MMA) embolization is a novel adjuvant endovascular procedure used to minimize the risk of recurrence of CSDH, and its use in pediatric populations is exceptionally rare. Methods: This is a case-report and review of the available literature. Results: A 14 year old male presented to the children hospital after an episode of dysarthria, word-finding aphasia and subtle right sided weakness. MRI revealed a CSDH left cerebral hemisphere with evidence of septations and an arachnoid cyst in the left middle cranial fossa. The patient underwent surgical drainage of the CSDH and subsequent MMA embolization. The patient made an excellent functional recovery with complete resolution of CSDH. Conclusions: Here we report our experience with MMA embolization as an adjuvant therapy for the treatment of a pediatric CSDH. We have found that MMA embolization provides a safe adjuvant therapy in the treatment of CSDH in the pediatric population, lending support to the limited literature of the utility of MMA in this age group. We propose that MMA embolization is safe and potentially efficatious in reducing risk of recurrence in pediatric complex, multi-loculated CSDHs

Background: While mechanical thrombectomy (MT) has become broadly used, many nuances around its performance are still contentious. In particular, the optimal sedation strategy for MT is not clear in the literature. Methods: This study was a single-center retrospective cohort study of a prospectively collected database. Age, gender, pre-treatment NIH stroke score (NIHSS), Alberta stroke program early score CT (ASPECTS), quality of collateralization, whether the patient underwent thrombectomy, tandem carotid occlusion, and thrombolysis in cerebral infarction (TICI) score were recorded in the database. Results: We identified 228 patients having anterior circulation mechanical thrombectomy (MT). 91 were right-sided, 108 were left-sided. Collaterals were graded as good in 135 (71.4), moderate in 44 (23.2%), and poor in 10 (5.3%). The average pre-MT ASPECTS was 8.1 (range). We found significant differences between all patients, patients with good outcome (mRS 0-2) and death in age, baseline NIHSS, collateralization, and TICI revascularization score. Multivariate analysis was performed with showed significant associations of sidedness, collateralization, TICI score and hemorrhage with neurological outcome. Right-sided stroke, better collaterals, higher TICI score and absence of hemorrhage were associated with better outcomes. Conclusions: We found comparable outcomes to those reported in the literature with use of general anesthetic. We identify several factors that influence outcomes.

Background: Idiopathic Normal Pressure Hydrocephalus (iNPH) is a disorder of the elderly with progressive worsening of gait and balance, cognition, and urinary control which requires assessment using criteria recommended by International iNPH guidelines. Methods: Adult Hydrocephalus Clinical Research Network (AHCRN) prospective registry data from 5-centers over a 50-month interval included entry criteria; demographics; comorbidities; examination findings using standard AHCRN gait and neuropsychology assessments; shunt procedures, complications of CSF drainage, complications within 30 days of surgery, and 1-year postoperative follow-up. Results: 547 patients were referred for assessment of suspected-iNPH. 123 patients(21.6%) did not meet clinical criteria to proceed with further testing. 424 patients(74.4%;mean age 76.7 ± 6.0 years;males=269) underwent an LP or lumbar drain, and 193(45.6%) underwent insertion of a ventriculoperitoneal shunt. By 8-12 months after shunt surgery, gait velocity was 0.96±0.35m/s (54% faster than pre-CSF-drainage). Mean MoCA scores increased from 21.0 ± 5.0(median=22.0) at baseline to 22.6±5.5(median=24) 12-months post-surgery. Gait and cognitive improvements were clinically significant. No deaths occurred. 8% of shunt-surgery patients experienced minor complications. The 30-day reoperation rate was 4.1%. Conclusions: This AHCRN study demonstrated that CSF-drainage testing of patients with suspected-iNPH successfully identified those who could undergo CSF-shunt surgery with a high rate of improvement and a low rate of complications.

Background: Brain-machine-interface research has utilized multichannel single neuron recordings to decode movement intention. However, the prefrontal cortex (PFC) contains mental representations of more abstract task and goal elements which may be utilized as important signals in a brain-machine-interface. We therefore utilized virtual reality to simulate a real-world task while recording from ensembles of primate PFC neurons. Methods: Two male rhesus macaques (macaca mulatta) were trained to navigate a virtual reality environment using a joystick and learn a context-object association rule. We implanted each monkey with two 96-channel Utah arrays (Blackrock Microsystems) in the lateral PFC (areas 9/46 and 8a) and simultaneously recorded from multiple single neurons. Results: A linear support-vector-machine decoded task elements (context, target location and chosen direction of movement) with significantly greater than chance accuracy. This information was decoded in a sequential manner as the primates made a rule-based decision, with context information appearing first, followed by target location, and chosen side. Conclusions: We found that different neuronal ensembles encode the elements needed for implementing the context rule, and that such ensembles are activated sequentially. Brain-machine-interface systems may benefit by integrating neural data from the PFC, providing salient goal-related information such as the content of the goal and its spatial location.