Background: Near-infrared spectroscopy regional cerebral oxygen saturation (rSO2) has gained interest as a raw parameter and as a basis for measuring cerebrovascular reactivity (CVR). This study aimed to identify threshold values of rSO2 and rSO2 based CVR at which outcomes worsened following traumatic brain injury (TBI). Methods: A retrospective multi-institutional cohort study was performed. The cerebral oxygen indices, COx (using rSO2 and cerebral perfusion pressure) as well as COx_a (using rSO2 and arterial blood pressure) were calculated for each patient. 2x2 tables were created grouping patients by alive/dead and favorable/unfavorable outcomes at various thresholds of COx and COx_a as well as rSO2 itself. Chi-square values were calculated to identify the most discriminative significant threshold. Results: In the cohort of 129 patients rSO2 did not have any statistically significant threshold value. For COx and COx_a, an optimal threshold value of 0.2 was identified for both survival and favorable outcomes with values above this associated with worse outcomes. Conclusions: In this study, raw rSO2was found to contain no significant prognostic information. However, rSO2 based indices of CVR, were found to have a uniform threshold of 0.2, above which clinical outcomes worsened. This study lays the groundwork to transition to less invasive means of continuously measuring CVR.

Background: Infantile hydrocephalus is characterized by an atypical accumulation of cerebrospinal fluid in the brain, diagnosed and treated before the age of 2 years. Hydrocephalus development is linked to thinning of the corpus callosum (CC), mainly due to the expansion of lateral ventricles, causing upward elevation and compression of periventricular and subcortical white matter. Methods: This study investigates structural alterations in the CC in children diagnosed with infantile hydrocephalus. We examined both macrostructural and microstructural facets of the CC, providing insights into the nature and extent of alterations associated with this condition. 18 patients with infantile hydrocephalus (mean age = 9 years), and 18 age and sex matched typically-developing healthy children, participated in the study. Structural magnetic resonance imaging and diffusion tensor imaging were utilized to assess CC volume and microstructure, respectively. Results: Our findings reveal reductions in CC volume, particularly in posterior area, and distinct microstructural disparities, notably pronounced in these same segments. Conclusions: Investigating these structural alterations provides an understanding into the mechanisms underlying the effects of infantile hydrocephalus on CC integrity, given its role as a neural bridge. This knowledge offers a more nuanced perspective on neurological disorders and underscores the significance of investigating the CC’s health in such contexts.

Background: Pineal region tumors are a heterogenous group of pathologies often symptomatic due to occlusive hydrocephalus leading to elevated intracranial pressure (ICP). High ICP may not always be associated with clinical signs. A non-invasive technique for assessment of ICP is measuring the optic nerve sheath diameter (ONSD). The goal of this study was to determine the utility of preoperative and postoperative ONSD measurements for assessment of elevated ICP in children with pineal region tumors. Methods: Retrospective data analysis was performed in patients operated for pineal region tumors at our tertiary care center between 2003 and 2022. Preoperative and postoperative MRI scans were reviewed. Clinical data and ONSD at multiple time points were analyzed and correlated. Results: Thirty-four patients with forty operative cases met the inclusion criteria. Hydrocephalus was seen in 80% of patients preoperatively (n=32/40). Presence of hydrocephalus was associated with significantly elevated ONSD preoperatively (p=0.006) and postoperatively (p=0.017). There was significant decrease in ONSD immediately postoperatively (p<0.001), at 3 months (p<0.001) and 12 months (p<0.001). In patients without hydrocephalus, no significant changes in ONSD were observed (p=0.369). Conclusions: ONSD is a useful adjunct for the identification of high ICP preoperatively and evaluation of treatment response postoperatively in patients presenting with pineal region tumors.

Background: Subarachnoid hemorrhages (SAH) are emergencies that require expedient workup. While Aneurysms and vascular malformations are a common cause, a subset of cases may lack detectable structural causes. If a CT angiogram (CTA) is negative, the more invasive Digital Subtraction Angiogram (DSA) is used for diagnosis. It is unclear how often DSA alters treatment for CTA negative SAHs. Methods: A retrospective review of SAH patients from our institution (Vancouver General Hospital) with a negative CTA with subsequent DSA in the past 25 years. Results: Our preliminary analysis included 233 patients. The median age was 55. 105 (45%) were female, and 128 (55%) were male. The average length of hospitalization was 9.6 days, and 226 (97%) were discharged alive. The median number of CTAs and DSAs administered were 2 and 1 respectively. In 12 (5%) cases, DSA detected an abnormality not seen on CTA, which led to endovascular or open surgery treatment in 5 (2%) cases. 5 DSA procedures led to complications including transient neurologic changes and ischemia. Conclusions: In SAH patients with CTA negative scans, additional DSA testing identified actionable pathology in only a small minority of cases. Clinicians must weigh the benefit of DSAs in these cases.

Background: Postoperative cranial neurosurgical imaging practices are highly variable. We evaluated the rate and utility of early postoperative computed tomography (EPCT, defined as a CT head scan within 24h of surgery) in consecutive adult craniotomies. Methods: We retrospectively reviewed consecutive adult craniotomies at the University of Alberta Hospital over a 45-day period (17/09/2022 to 01/11/2022). Electronic medical records were reviewed to extract data on the rate, timing, and utility of EPCT as well as the rate of neurologic deterioration and repeat surgical intervention. Results: A total of 56 patients (27 female; 55.5 ± 2.1 yrs, range: 19-84 years) were identified. All patients underwent EPCT, including 10/56 (17.9%) on POD0 and 46/56 (82.1%) on POD1. Surgical complications (bleeding, extensive pneumocephalus, edema, ischemia) were identified in 8/56 (14.3%) of the EPCT, of which 6 (10.7%) were reported to have neurologic deterioration and 2 (3.6%) underwent further surgical intervention (hematoma evacuation). Clinical and radiological postoperative changes were highly related (p=5.16e-06), and the rate of EPCT being adverse without neurologic deficit, managed surgically, was 1/56 (1.8%). Conclusions: EPCT is routine practice. Given the low rate (1.8%) of repeat surgical intervention in the absence of neurologic deficit despite abnormal EPCT, omitting EPCT in neurologically intact patients may be warranted.

Background: Degenerative cervical myelopathy (DCM) is the most common form of atraumatic spinal cord injury globally, yet clinical guidelines remain unclear on surgical recommendations for patients with mild forms of DCM. This is in part due to limitations in current MR imaging interpretation and complex mechanisms of neurological deterioration. Supervised machine learning (ML) models can help to identify clinical and imaging indicators of deterioration within mild DCM patients. Methods: 127 MRI scans (T2w, Diffusion Tensor Imaging, and Magnetization transfer scans) accompanied by a series of clinical tests underwent a semi-automated analysis to derive quantitative metrics. Random forest classifier, Support Vector Machine, and Logistic Regression models were trained and tested to predict 6-month neurological deterioration within patients. Results: The ML models performed, on average, better than previous studies with a balanced accuracy ranging between 70-75%. “Advanced” imaging metrics such as diffusion tensor imaging and magnetization transfer scans played an important role in improving model accuracy but only when used near the maximally compressed disc level, suggesting that limited yet targetted imaging metrics support ML model performance. Conclusions: The inclusion of specific, targeted imaging and clinical metrics support ML model performance in predicting neurological deterioration within mild DCM patients.

Background: The integration of Artificial Intelligence (AI) in medical education is an area of growing importance. While AI models have been evaluated extensively in multiple-choice question formats, their proficiency in written exams remains to be explored. Methods: Four AI models—GPT-4 (OpenAI), Claude-2.1 (Anthropic), Gemini Pro (Google), and Perplexity 70B (Perplexity)—were tested using the Canadian Royal College Sample Neurosurgery Exam. The written exam covered diagnostic reasoning, knowledge of neurosurgical conditions, and understanding of radiographic imaging techniques. Results: GPT-4 and Perplexity 70B both achieved a score of 68.42%, followed by Claude-2.1 with 60.53%, and Gemini Pro with 57.89%. The models showed proficiency in answering questions that required factual knowledge, such as identifying pathogens in spinal epidural abscess. However, they struggled with more complex diagnostic reasoning tasks, particularly in explaining the pathophysiology behind a sudden rise in blood pressure during surgery and interpreting radiographic characteristics of intracranial abscesses on MRI. Conclusions: The findings indicate that while AI models like GPT-4 and Perplexity 70B are adept at handling factual neurosurgical questions, their performance in complex diagnostic reasoning in a written format is less consistent. This underscores the need for more advanced and specialized AI training, particularly in the nuances of medical diagnostics and decision-making.

Background: Cognitive flow has been linked with enhanced performance, career satisfaction, and decreased burnout. However, while elite sport has long trained athletes to enter flow states, the concept has not been adopted strongly in healthcare. Flow has primarily been explored from a unidimensional (cognitive) perspective. The present study sought to understand the experience of flow among surgeons through a multidimensional lens. Methods: Using a constructivist grounded theory methodology, semi-structured interviews were conducted with 19 staff surgeons at the University of Toronto, purposively sampled. Data were coded and analyzed iteratively by three researchers until theoretical saturation was achieved. Results: Although many surgeons had not previously heard of cognitive flow, the phenomenon deeply resonated with most. Participants described different physical, cognitive, emotional, sociocultural, and environmental components that interacted to shape the subjective experience of flow: “I think that there are many different facets of [flow] that don’t always come together all at the same time, you may feel different parts of it… depending on what the kind of case is, who your help is, if you recently had a complication.” (P4) Conclusions: Understanding flow in clinical practice may lead to new avenues for enhancing career satisfaction and promoting physician wellness.

Background: Gender disparities persist in neurosurgery, unfortunately impacting career progression for women. Understanding these challenges is vital for fostering inclusivity. Methods: An international survey designed using a physician wellness framework was sent to neurosurgeons between June 2021 and November 2021. Univariate analysis (Kruskal-Wallis Test) was performed to assess various aspects of perceived career progression as a function of gender. Results: Of the total 537 respondents (64% neurosurgeons, 6% fellows, and 30% residents), 69% identified as male, 29% as female, and 2% as other. Compared to their male colleagues, female neurosurgeons expressed greater desire to advance in their career (p<0.05) and to leave their home country in the interest of job prospects (p<0.05). Despite these aspirations, female neurosurgeons reported that they did not have available career advancement opportunities (p<0.05), that the culture in their country inhibited their career advancement (p<0.05), and that they felt subject to harassment at their workplace (p<0.05). Conclusions: Our survey highlights significant gender-related obstacles in neurosurgical career advancement. Female neurosurgeons express strong career aspirations but face barriers such as limited opportunities, cultural impediments, and harassment. Addressing these challenges is crucial for achieving gender equity in neurosurgery.

Background: Gender disparities endure in neurosurgery, impacting the experiences of female practitioners. Unveiling these challenges is crucial for promoting inclusivity and addressing the unique obstacles faced by women in the field. Methods: An international survey designed using a physician wellness framework was sent to neurosurgeons between June 2021 and November 2021. Univariate analysis (Kruskal-Wallis Test) was performed to assess feelings of inclusion and diversity as a function of gender. Results: Of the total 384 respondents (65% neurosurgeons, 6% fellows, and 29% residents), 71% identified as male, 27% as female, and 2% as other. Compared to their male colleagues, female neurosurgeons more strongly endorsed feeling that their career progression has been limited by their gender (p<0.05) and were less likely to feel entrusted in their surgical ability (p<0.05) or to have equal access to surgical resources (p<0.05). Furthermore, they were less likely to endorse feelings that leaders in their department were committed to creating an inclusive environment (p<0.05). Conclusions: Our survey sheds light on significant gender-related disparities in neurosurgery. Female neurosurgeons express heightened concerns about gender-limiting career progression, reduced trust in their surgical abilities, and disparities in resource access. These findings underscore the imperative to foster a more inclusive and supportive environment within the field.

Background: An estimated 27-69 million individuals worldwide sustain a mild Traumatic Brain Injury (mTBI) each year, making it an important public health concern. Many victims experience post-injury neuropsychological issues such as anxiety and depression, which are associated with more post-concussive symptoms and worse functional outcomes. We sought to determine a systematic process to document the presence of anxiety and depression symptoms in mTBI patients to prevent negative impacts on their recovery. Methods: We administered the Generalized Anxiety Disorder-7 (GAD-7) and Center for Epidemiologic Studies Depression Scale Revised (CESDR-10) questionnaires, no more than three months after injury, to screen for these symptoms. A retrospective chart review was performed for 328 patients from the Montreal General Hospital mTBI Clinic who either received these questionnaires (N=143, Mage=40.36, SDage=15.557, Nfemale=90, Nmale=53) or did not (N=185, Mage=41.17, SDage=16.449, Nfemale=114, Nmale=71). The number of interventions received between groups were compared using ANOVA. Results: Patients who received the questionnaires (M=1.34, SD=0.978) were referred to significantly more interventions than those who did not (M=0.90, SD=0.876, p<0.001) and the rate of referral positively correlated with GAD-7 and CESDR-10 scores. Conclusions: Screening for symptoms of anxiety and depression post mTBI helps clinicians refer patients to the appropriate resources, which in turn should improve outcome.

Background: Employment and personal income loss after traumatic brain injury (TBI) is a major source of post-injury stress and barrier to societal reintegration for affected patients. We sought to quantify the labor market implications for tax-filing adult TBI survivors. Methods: We performed a matched difference-in-difference analysis using a national retrospective cohort of working adult TBI survivors injured between 2007-2017. Linear and logistic mixed effects regressions were used to estimate the magnitude of personal income loss and proportion of patients displaced from the workforce in the three post-injury years (Y+1 to Y+3). Results: Among 18,050 patients identified with TBI, the adjusted average loss of personal annual income was $-7,635 dollars in Y+1 and $-5,000 in Y+3. An additional -7.8% individuals were newly unemployed compared to the pre-injury baseline. For mild, moderate, and severe TBI subgroups, income loss was $-3354, $-6750, and $-17375 respectively in Y+3; the proportion of newly unemployed individuals in Y+3 was 5.8%, 9.2%, and 20% lower than baseline. We estimated 500 million dollars of incurred labor markets losses related to TBI in Canada. Conclusions: This work represents the first national cohort data quantifying the labor market implications of TBI. These results may be used to inform post-injury care pathways and vocational rehabilitation.

Background: Despite the utility of administrative health data, there remains a lack of patient-centered outcome measures to meaningfully capture morbidity after traumatic brain injury (TBI). We sought to characterize and validate days at home (DAH) as a feasible measure to assess population-level moderate to severe TBI (msTBI) outcomes and health resource utilization. Methods: We utilized linked health administrative data sources to identify adults with msTBI patients presenting to trauma centers in Ontario injured between 2009-2021. DAH at 180 days reflects the total number of days spent alive and at home excluding the days spent institutionalized in acute care, rehabilitation, inpatient mental health settings or post-acute readmissions. Construct and predictive validity were determined; we additionally estimated minimally important difference (MID) in DAH180days. Results: There were 6340 patients that met inclusion criteria. Median DAH180days were 70 days (interquartile range 0-144). Increased health resource utilization at baseline, older age, increasing cranial injury severity and major extracranial injuries were significantly associated with fewer DAH180days. DAH180days was correlated to DAH counts at 1-3 years. The average MID estimate from anchor-based and distribution-based methods was 18 days. Conclusions: We introduce DAH180days as a feasible and sufficiently responsive patient-centered outcome measure with construct, predictive and face validity in an msTBI population.

Background: Chronic subdural hematoma (CSDH) is a common neurosurgical condition which can be treated with surgical evacuation. A significant percentage of CSDH patients are on antiplatelet or anticoagulation therapy at baseline which may influence risk of recurrence and postoperative thromboembolic events Methods: A search was conducted in MEDLINE (1946 to April 6, 2023), Embase (1974 to April 6, 2023), and PubMed (up to April 6, 2023) on preoperative use of antiplatelet or anticoagulation therapy and outcomes following surgical evacuation of CSDH. Results: Our literature includes 14,410 patients ifrom 42 studies, with 3218 (22%) in the antiplatelet (AP) group, 1731(12%) in the anticoagulation (AC) group, and 9537 (66%) in the no antithrombotics (NA) group. The AP group had significantly higher recurrence compared to NA (OR = 1.21, 95% CI = 1.04 to 1.40, p = 0.01). The AC group also had significantly high recurrence compared to NA (OR = 1.39. 95% CI = 1.15 to 1.68, p = 0.0007). However, being on any antithrombotic therapy is also associated with significantly higher thromboembolic events (OR 5.41, 95% CI 3.16 to 9.26, p < 0.00001). Conclusions: Patients on antithrombotic therapy have both higher recurrence and higher thromboembolic risk compared to patients not on antithrombotic therapy.

Background: Near-infrared spectroscopy (NIRS) regional cerebral oxygen saturation (rSO2) based cerebrovascular reactivity (CVR) indicies have enable the entirely non-invasive continuous monitoring. This study aims to compare CVR in those recovering from moderate/severe TBI to a health control group. Methods: In this prospective cohort study the cerebral oxygen CVR index, COx_a (using rSO2 and arterial blood pressure), was measured in subjects with moderate/severe TBI at follow-up. COx_a was also measured in a group of healthy controls. CVR was compared within and between these groups using conventional statistics. Results: A total of 101 heathy subject were recruited for this study along with 29 TBI patients. In the health cohort COx_a was not statistically different between males and females or in the dominate and non-dominate hemisphere. The TBI cohort, COx_a was not statistically different between first and last available follow up. Surprisingly, CVR as measured by COx_a was statistically better in those recovering from TBI than in the healthy cohort. Conclusions: In the prospective cohort study, CVR as measured by NIRS based methods, was found to be more active in those recovering from TBI than in a healthy cohort. This study may indicate that, in those that survive TBI, CVR may be enhanced as a neuroprotective measure.

Background: Subdural and subgaleal drains are equally effective after burrhole craniostomy for chronic subdural haematoma, however the optimal location of drains after minicraniotomy is not clear. As such we present the first study to assess this. Methods: Consecutive patients undergoing minicraniotomy for cSDH between 2019 and 2023 at a single institution were included. Subgaleal drains were placed exclusively by a single surgeon with the rest of the department utilising standard subdural drains. Cases were stratified by drain location. Primary outcomes included changes in functional status (Modified Rankin Score, mRS) at 3 months from preoperative baseline. Results: A total of 137 patients were included, of which 24.6% received subgaleal drains. Discharge home was higher in the subgaleal group compared to subdural group (79.4% vs 57.3%, p=0.02). Subgaleal drain location (p<0.0001) and better preoperative GCS (p=0.01) were predictors of improved 3 month mRS. Worse premorbid mRS (p=0.002), subdural drain (p=0.004), and decreased consciousness at presentation (p<0.002) were predictors of not being discharged home. Surgical recurrence was lower in the subgaleal group than the subdural group (2.9% vs 13.6%, p=0.12), but not statistically significant. Conclusions: Subgaleal drains are associated with shorter hospitalisation, greater chance of discharge home, and better functional outcomes than subdural drains.

Background: The formation of pial-pial collateral network aneurysms due to carotid occlusion is a rare neurological phenomenon. This case details a 69-year-old male who developed a pial-pial collateral network aneurysm secondary to left internal carotid artery occlusion, leading to intracranial hemorrhage. Methods: The patient presented with altered consciousness due to left temporal intracerebral hemorrhage, subdural hematoma, and intraventricular hemorrhage. Cerebral angiography revealed an occluded left internal carotid artery, with superficial temporal artery (STA) and superior orbital artery anastomosis, and extensive pial-pial collaterals from the posterior temporal artery. A 4 mm aneurysm arising from this collateral network was identified. Surgical intervention involved a left temporal craniectomy and excision of the aneurysm, prioritizing the preservation of the STA. N.B., Informed patient consent was obtained in this study. Results: Successful aneurysm removal and preservation of collateral pathways were confirmed by postoperative imaging. The patient exhibited rapid neurological improvement; by postoperative day (POD) one, the patient showed limited response to stimuli. He was extubated by POD4 and discharged on POD27, where he conversed well, was independently ambulatory, and needed minimal to no assistance in activities of daily living. Conclusions: This case highlights the need for careful preoperative planning and intraoperative precision, especially in preserving vital collateral vascular pathways.

Background: Managing unruptured cerebral aneurysms involves monitoring or repair, with complex factors influencing decision-making. Geographical distance from treatment centers is an understudied factor. This study explores a potential relationship in Nova Scotia between proximity to the sole neurosurgical center in Halifax and aneurysm management. Methods: A prospectively collected neurosurgery database was used to identify all adults seen for unruptured cerebral aneurysm between Jan 1, 2015 - Dec 31, 2020. Demographic data, aneurysm characteristics, follow-up and treatment information were collected. Univariate and multivariate analyses assessed management differences based on geography, controlling for relevant factors including aneurysm size and location. Results: Among 390 patients, 40% were in Halifax, and 60% were outside. No significant difference existed in elective repair (34% vs. 26%, p=0.143) and imaging follow-up frequency (2.26 vs. 2.22, p=0.858). In-person follow-up was higher within Halifax (1.83 vs. 1.43, p=0.008), while virtual follow-up was significant outside Halifax (1.44 vs. 1.01, p=0.003). Overall, in-person and elective repair frequencies declined with the COVID-19 peak, whereas virtual follow-up increased. Conclusions: No significant association was found between patient location and repair decisions. Patients in closer proximity had more in-person follow-ups, while those farther away had more virtual follow-ups. The COVID-19 pandemic affected follow-up frequencies universally.

Background: The fragility index (FI) is the minimum number of patients whose status would have to change from a nonevent to an event to turn a statistically significant result to a non-significant result. We used this to measure the robustness of trials comparing carotid endarterectomy (CEA) to carotid artery stenting (CAS). Methods: A search was conducted in MEDLINE, Embase, and PubMed on RCTs comparing CEA to CAS. The trials need to have statistically significant results and dichotomous primary endpoints to be included. Results: Our literature search identified 10 RCTs which included 9382 patients (4734 CEA, 4648 CAS). The primary end points of all included trials favoured CEA over CAS. The median FI was 9.5 (interquartile range 2.25 - 21.25). All of the studies that reported lost-to-follow-up (LTFU) had LTFU greater than its fragility index, which raises concern that the missing data could change the results of the trial from statistically significant to statistically insignificant. Conclusions: A small number of events (FI, median 9.5) were required to render the results of carotid artery stenosis RCTs comparing CEA to CAS statistically insignificant. All of the studies that reported LTFU had LTFU greater than its fragility index.

Background: Pediatric arteriovenous malformations (AVMs) are rare, but represent the leading cause of intracranial hemorrhage in children. These are traditionally understood to be congenital lesions, however AVMs recurrence within previously unaffected tissue challenges this understanding. Recurrence after microsurgery and endovascular treatment have been studied in greater detail, but little literature exists surrounding recurrence after Gamma Knife Radiosurgery (GKRS). Methods: We performed a retrospective chart review of all pediatric AVMs treated with GKRS at our centre. Charts were assessed by two reviewers to identify cases of AVM recurrence after angiographically confirmed obliteration. To contextualize our institutional patterns, we also performed a structured literature review of published data reporting pediatric AVM recurrence after GKRS. Results: Our institutional review revealed two cases of AVM recurrence after angiographically proven cure, and our review of literature identified nine retrospective reviews and three case reports, which in total reported 22 individual cases of recurrence. The recurrence rate in the retrospective reviews ranged from 0 to 18%. Conclusions: The current work illustrates that while AVM recurrence is rare, it is a possible complication of GKRS. There was also a qualitative suggestion that embolization prior to CT increased risk of recurrence. Both these facts should be included in decision-making and patient counselling.