Background: Myeloid sarcoma (MS) is a rare solid tumour made of myeloblasts or immature myeloid cells in an extramedullary site or in bone, associated with systemic hematologic neoplasms. When they occur in the brain parenchyma, they can often be misdiagnosed. Methods: The authors report a case of a 4-year old boy 6 months out of remission from AML, presenting with a short history of headaches and vomiting, and found to have a heterogenous contrast-enhancing lesion in the right cerebellar hemisphere, with differential diagnosis of myeloid sarcoma, astrocytoma, medulloblastoma and ATRT. Preliminary diagnosis was made flow cytometry from an intraoperative biopsy. The patient had a long course of chemotherapy and radiation, but eventually died from the systemic burden of his AML. Results: The authors present a literature review on 178 published cases of CNS myeloid sarcomas, and their radiological presentation and the basis of immunohistochemical and pathological diagnosis is discussed. Conclusions: Diagnosis rests on a combination of immunohistochemistry and histopathology of biopsied tissue. Surgical resection is controversial, especially given the efficacy of chemotherapy and radiation, and prognosis remains unclear. As with all uncommon and rare clinical entities, further investigation is warranted to determine prognosis and optimal management of CNS myeloid sarcomas.

Background: While pediatric high-grade glioma (HGG) has a poor prognosis, the relationship between extent of resection (EOR), tumor location, and survival remains unclear. Our aim is to determine whether gross-total resection (GTR) is associated with prolonged survival relative to subtotal resection (STR) and biopsy. Methods: PubMed, Ovid EBM Reviews, Embase, and MEDLINE were systematically reviewed. Eligible articles were included for study-level and individual-patient data (IPD) meta-analysis. Difference by study-level and IPD characteristics were estimated using subgroup meta-analysis and meta-regression. PRISMA guidelines were followed. Results: In total, 33 studies were included. Study-level meta-analysis found GTR conferred decreased mortality relative to STR at 1 year (RR=0.73, 95%CI=0.59-0.89) and 2 years (RR=0.74, 95%CI=0.64-0.84). STR did not demonstrate survival advantages compared to biopsy at 1 year (RR=0.81, 95%CI=0.64-1.03), but showed decreased mortality at 2 years (RR=0.90, 95%CI=0.82-0.99). IPD meta-analysis comprised 186 patients, and indicated that STR (HR=2.61, 95%CI=1.56-4.38) and biopsy (HR=2.83, 95%CI=1.54-5.19) had shortened survival relative to GTR, with no differences between STR and biopsy (HR=0.93, 95%CI=0.55-1.56). In subgroup analysis, GTR was associated with prolonged survival for hemispheric tumors (HR=0.16, 95%CI=0.07-0.36) Conclusions: Among pediatric patients with HGGs, GTR was independently associated with better overall survival compared to STR and biopsy, especially in patients with hemispheric tumors.

Background: Tumor treatment fields (TTFields) are an approved adjuvant therapy for glioblastoma. The magnitude of applied electrical field is related to the anti-tumoral response. However, peritumoral edema (ptE) may result in shunting of electrical current around the tumor, thereby reducing the intra-tumoral electric field. In this study, we address this issue with computational simulations. Methods: Finite element models were created with varying amounts of ptE surrounding a virtual tumor. The electric field distribution was simulated using the standard TTFields electrode montage. Electric field magnitude was extracted from the tumor and related to edema thickness. Two patient specific models were created to confirm these results. Results: The inclusion of ptE decreased the magnitude of the electric field within the tumor. In the model considering a frontal tumor and an anterior-posterior electrode configuration, ≥ 6 mm of ptE decreased the electric field by 52%. In the patient specific models, ptE decreased the electric field within the tumor by an average of 26%. The effect of ptE on the electric field distribution was spatially heterogenous. Conclusions: Given the importance of electric field magnitude for the anti-tumoral effects of TTFields, the presence of edema should be considered both in future modelling studies and as a predictor of non-response.

Background: A significant proportion of glioblastoma multiforme (GBM) patients are considered for repeat resection, but evidence regarding best management remains elusive. Methods: An electronic portfolio of MR images of 37 cases of pathologically confirmed recurrent GBM with an accompanying clinical vignette was constructed. Surgical responders from various countries, training backgrounds, and years’ experience were asked for each case to select: their chosen management (repeat surgery, chemotherapy, radiation, or conservative), confidence in recommended management, and whether they would include the patient in a randomized trial that gave a 50% chance of re-operation. Responses were evaluated with kappa statistics and values interpreted according to Landis and Koch (0–0.2, slight; 0.21–0.4, fair; 0.41–0.6, moderate; 0.61–0.8, substantial; 0.81-1.0 perfect agreement). Results: 26 surgeons responded to the survey. Agreement regarding best management of recurrent GBM was slight, even when management options were dichotomized (repeat surgery vs. all others) (k=0.198 (95%CI 0.133-0.276). Country of practice, years’ experience, and training background did not improve agreement. Responders were willing to include more than 70% of patients in a randomized trial. Conclusions: Only slight agreement exists regarding the question of re-operation for patients with recurrent GBM. This supports the need for a randomized controlled trial.

Background: Pseudotumoral hemicerebellitis is an acute, unilateral inflammation of the cerebellum that typically affects the pediatric population. The etiology remains to be elucidated, however frequently is attributed to post-infectious inflammation. Though it tends to be self-resolving, treatment may reduce the time to symptomatic recovery. Systemic corticosteroid therapy has been proposed as a mechanism for improving outcomes and time to symptomatic recovery. Methods: We present a case report of a 12-year-old male with pseudotumoral hemicerebellitis and unilateral cerebellar dysfunction. Additionally, we briefly review the additional 35 reported cases of pseudotumoural hemicerebellitis with respect to length of time to symptomatic recovery with or without systemic corticosteroid treatment. Results: 30 cases reported length of time to symptomatic recovery. Including our case, the mean time to recovery for those treated with systemic corticosteroids (n=20) was 48.05 days(SE=16.3). The mean time to recovery for those treated without (n=10) was 86.7 days(SE=29.3). Conclusions: Treatment with systemic corticosteroids was associated with a faster time to symptomatic recovery compared to without. Regardless of etiology, reducing inflammation and mass effect involved in pseudotumoral hemicerebellitis may be integral to a more rapid return to neurological baseline.

Background: An increasing number of elderly patients are being diagnosed with GBM and undergoing surgery. These patients often present with multiple medical comorbidities and have significantly worse outcomes compared to adult patients. The goal of this study was to determine clinical predictors of survival in elderly patients undergoing surgery for GBM. Methods: A retrospective chart review of all consecutive patients 65 years of age and older that underwent surgery for newly diagnosed GBM from 2005-2018 was performed. A total of 150 patients were included, and subdivided into two age categories; 65-74 and 75 or older. Results: Advanced age and medical comorbidities were not associated with decreased survival (p = 0.07 and p = 0.09, respectively). Postoperative complication was associated with worse survival for all patients (HR = 2.34, p = 0.01) and occurred in patients with longer lengths of stay (p < 0.0001) and discharge destination other than home (p = 0.001). Conclusions: The presence of medical comorbidities and advanced age are not reasons to exclude patients with GBM from surgical consideration. Postoperative complication is the most significant predictor of survival in elderly patients and can be avoided by a short length of stay and discharge home.

Background: Primary malignant brain tumours account for over one third of all brain tumours and are associated with high morbidity and mortality. The purpose of this paper is to estimate the rate and trends of incidence and prevalence for primary malignant CNS tumours in Canada from 1992 to 2017. Methods: An epidemiological study using publicly available data from Statistics Canada: Canadian Cancer Registry (CCR) from 1992 to 2017 for all of Canada was conducted. Incidence and prevalence per 100,000, age-standardized incidence, and age-standardized prevalence per 100,000 person-years of primary malignant CNS tumours were calculated and stratified by sex and age: pediatric (0-19), adult (20-64), and elderly (>64) populations. Results: During the study period, incidence and prevalence increased by 27.3% and 28.8%, respectively. Males accounted for 56% of all diagnoses and experienced decreased survival compared to females one year after diagnosis (p-value = 0.04). Age-standardized rates of incidence and prevalence were highest in elderly populations. Conclusions: Overall, the incidence of primary malignant CNS tumours has increased from 1992 to 2017 with males and the elderly disproportionately affected. Increased healthcare resources and awareness are needed to better identify and deliver evidence-based care for these patients.

Background: Previous studies have found conflicting results regarding the role of repeat surgery on overall survival (OS) in patients with GBM. We used a novel approach that includes time to tumour recurrence as an additional prognostic factor in order to determine which patients benefit most from repeat surgery. Methods: A retrospective chart review from 1992-2018 was performed on all adult (≥ 18 years old) patients with primary GBM that received surgery for recurrent disease and compared to publicly available data from The Cancer Genome Atlas (TCGA) of adult patients with primary GBM that did not undergo surgery for recurrent disease. Results: A total of 672 adult patients with GBM were included in the study, including 87 that received surgery at tumour recurrence (surgery cohort). The surgery cohort had longer OS and similar complication rates to those that did not receive surgery at recurrence, independent of time to tumour recurrence (p < 0.0001 and p = 0.4, respectively). Within the surgery cohort, patients with tumour recurrence >6 months demonstrated additional survival benefit (p < 0.0001). Conclusions: Surgery for recurrent GBM leads to improved survival without increased complications. Patients with tumour recurrence >6 months benefit most from repeat surgery.

Background: External ventricular drains are a lifesaving intervention in the management of acute hydrocephalus. EVD associated infections vary significantly, and expert panels recommend reviewing institutional policies if infection rates exceed 10%. The audit aims to identify the infection rate at our institution, whereas the literature review aims to synthesize a new institutional EVD best practice guideline. Methods: An audit of EVD catheters inserted in the time period between 07/01/2019 and 10/25/2020 was conducted. Statistical analysis to calculate absolute incidence, infections per 1000 days of catheter use. A literature review to identify best practices for the insertion and management of EVDs was conducted. Results: 75 patients required a total of 105 EVD catheters. There were 16 (15.3%) EVD related infections, equating to 14.3 infections per 1000 days. Fifty percent of patients developed an EVD related infection within 9 days of insertion. Most infections were induced by skin flora (87.5%). A comprehensive step-by-step EVD insertion and management protocol was developed aiming to reduce the risk of infection. Conclusions: The incidence of EVD associated infections at the Ottawa Hospital is significantly higher than acceptable rates as suggested by expert panels. A new evidence-based best practice guidelines should be implemented. A follow-up audit is necessary.

Background: Establishing spatial correspondence between subject and template images is necessary in neuroimaging research and clinical applications. A point-based set of anatomical fiducials (AFIDs) was recently developed and validated to provide quantitative measures of image registration. We applied the AFIDs protocol to magnetic resonance images (MRIs) obtained from patients with Parkinson’s Disease (PD). Methods: Two expert and three novice raters placed AFIDs on MRIs of 39 PD patients. Localization and registration errors were calculated. To investigate for unique morphometric features, pairwise distances between AFIDs were calculated and compared to 30 controls who previously had AFIDs placed. Wilcoxon rank-sum tests with Bonferroni corrections were used. Results: 6240 AFIDs were placed with a mean localization error (±SD) of 1.57mm±1.16mm and mean registration error of 3.34mm±1.94mm. Out of the 496 pairwise distances, 40 were statistically significant (p<0.05/496). PD patients had a decreased pairwise distance between the left temporal horn, brainstem and pineal gland. Conclusions: AFIDs can be successfully applied with millimetric accuracy in a clinical setting and utilized to provide localized and quantitative measures of registration error. AFIDs provide clinicians and researchers with a common, open framework for quality control and validation of spatial correspondence, facilitating accurate aggregation of imaging datasets and comparisons between various neurological conditions.

Background: Pituitary tumor recurrence following endoscopic endonasal transsphenoidal surgery (EETS) has been reported widely. We evaluated a modified score using the SIPAP classification system, combining the suprasellar and paraseller extension scores of the pituitary tumor, to determine its impact on adenoma recurrence. Methods: A retrospective cohort study design with patient characteristics, tumor type, endocrine, operation, imaging data collected. Preoperative MRI images were reviewed and SIPAP classification applied. Postoperative data were extracted for the follow-up period available for each patient.The suprasellar score and the highest parasellar scoring from both sides were numerically summed in a bilateral suprasellar and parasellar (SaP) score and combined to make 4 grades. Results: 276 patients were identified, 56.5% of the cohort was male. The mean cohort age was 54 years old.The mean follow up period was 32 months. Patient perioperative tumor grade according to SaP classification and recurrence rate was: Grade 1: 11%: Grade 2: 10%; Grade 3: 15%; Grade 4: 22%. The results followed a pattern of logarithmic curve. Conclusions: The SaP classification was useful in determining the pituitary tumor expected recurrence following EETS. The advanced tumors had the highest recurrence rates. Use of the SaP score may allow for more accurate preoperative counselling of patients with pituitary adenoma.

Background: There is growing evidence for the use of augmented reality (AR) in pedicle screw placement in spinal surgery to increase surgical accuracy, improve clinical outcomes and reduce the radiation exposure required for intraoperative navigation. Auto-segmentation is the cornerstone of AR applications because it correlates patient-specific anatomy to structures segmented from preoperative computed tomography (pCT) images. These AR techniques allow for a reduction in the radiation dose required to acquire CT images while maintaining accurate segmentation. Methods: In this study, we methodically increase the noise that is introduced into CT images to determine the image quality threshold that is required for auto-segmentation on pCT. We then enhance the images with denoising algorithms to evaluate the effect on the segmentation. Results: The pCT radiation dose is decreased to below the current lowest clinical threshold and the resulting images still produce segmentations that are appropriate for input into AR applications. The application of denoising algorithms to the images resulted in increased artifacts and decreased bone density. Conclusions: The CT image quality that is required for successful AR auto-segmentation is lower than that which is currently employed in spine surgery. Future research is required to identify the specific, clinically relevant radiation dose thresholds.

Background: Spinal cord compression from degenerative cervical myelopathy is characterized by progressive loss of hand dexterity, alongside changes in the metabolite profiles in the brain and spinal cord. Correlating the changing metabolite profile with measures of dexterity following decompression surgery may assist in identifying which patients may benefit most from surgery. Methods: Thirty operative myelopathy patients consented to receive spectroscopy and GRASSP-M dexterity assessments both preoperatively and 6-weeks postoperatively. Magnetic resonance spectroscopy (TE=135) was performed in the motor cortex using a 3 Tesla Siemens MRI scanner at Robarts Research Institute. Spearman correlations were used to evaluate associations between metabolite levels and dexterity (p<0.05 was considered significant). Paired two-tailed Student t-tests were used to assess for postoperative changes in metabolite levels. Results: Postoperatively, we observed a statistically significant (p<0.05) negative correlation (r=-0.44) between the N-acetylaspartate-to-creatine ratio (NAA/Cr) and GRASSP-M dexterity scores. There was no significant difference in NAA, Cr, or NAA/Cr postoperatively. Conclusions: These findings demonstrate that patients with lower postoperative NAA/Cr usually have better recovery of dexterity. This link between the myelopathic metabolite profile and clinically meaningful dexterity values requires further investigation to understand the role of both NAA and Cr in mechanisms of postoperative recovery from myelopathy.

Background: Degenerative cervical myelopathy is characterized by progressive compression of the spinal cord resulting in debilitating loss of dexterity, independent ambulation, and sphincter control. Diffusion tensor imaging (DTI) has shown that, compared to healthy controls, myelopathy patients have decreased integrity of the corticospinal tracts and corpus callosum (Bernabeu-Sanz et al, 2020). Methods: Twenty-six myelopathy patients consented to cerebral diffusion tensor imaging (3 Tesla, 32 directions, b=1000) preoperatively, as well as 6-weeks, 12-weeks, and 6-months postoperatively. Average mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were measured in the corticospinal tracts, forceps major, and forceps minor. Results: Both MD and RD decreased from 6-12 weeks postoperatively in the right corticospinal tract. The forceps major of the corpus callosum showed an initial postoperative increase in MD followed by a subsequent increase in FA and decrease in RD 3-6 months postoperatively. The AD of the forceps major increased both immediately and 3-6 months postoperatively. Conclusions: Changes in microstructural integrity of the corticospinal tract and forceps major over the postoperative recovery period suggest a pattern of recovery in myelopathy patients. This study is the first to report postoperative DTI changes in myelopathy-relevant white matter tracts in the brain.

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: Image-guided navigation is routinely used in spine surgery to improve placement of pedicle screws. However, most reports have relied on two-dimensional X-ray evaluation to determine accuracy of screw positioning. In this study, computed tomography (CT) and O-arm imaging enabled a detailed three-dimensional comparison of screw placement. The objective was to compare the accuracy of pedicle screw placement with intraoperative X-ray versus O-arm image-guided navigation. Methods: This was a retrospective analysis of image-guided pedicle screw placement in patients who underwent spinal instrumentation. Post-operative CT and O-arm imaging allowed grading of screw accuracy based on pedicle breaches. Clinical outcomes included patient and operative factors. Results: Pedicle screws were placed in 208 patients (1116 screws). Three-dimensional O-arm guidance was utilized for 126 patients, while the remainder underwent two-dimensional X-ray imaging and post-operative CT assessment. O-arm navigation was associated with improved pedicle screw accuracy: pedicle breaches were more likely to be low grade (odds ratio 2.84, p=0.001) and less likely to be medium grade (odds ratio 0.35, p=0.007) or high grade (odds ratio 0.31, p=0.025). Conclusions: This study provided a detailed comparison of surgical accuracy with X-ray versus O-arm guidance. Navigation with O-arm imaging is associated with benefits in spinal instrumentation, without impacting operative risks for patients.

Background: Most individual thalamic nuclei cannot be directly visualized on routine clinical MRI. Stereotactic targeting techniques are indirect, relying on histological atlases and electrophysiological recording. We investigate whether high-field MRI can directly visualize the thalamic nuclei in vivo and allow for analysis of disease-related changes. Methods: Thirty-two healthy individuals were imaged with 7T MRI at a resolution of 0.7mm3. To obtain a high-resolution composite image, these were registered across subjects and averaged together. Three thalamic structures closely integrated in seizure propagation, the anterior thalamic nucleus (ATN), mammillothalamic tract (MTT), and centromedian nucleus (CM) were manually segmented in a subset of healthy subjects and patients with temporal lobe epilepsy (TLE). Results: There is sufficient resolution within the thalamus at 7T for visualization of the ATN, CM, and MTT. In the small subset of 5 controls and 5 TLE patients examined, there was no significant difference (p>0.05) in volume or mean T1map for the three thalamic sturctures of interest. Conclusions: MRI at 7T provides a method of direct visualization of thalamic nuclei, uncovering substructures not previously identifiable in vivo. These advances will enable quantitative analysis of disease-related changes to these structures and improved clinical targeting as demonstrated in this initial ‘proof-of-concept’ subset analysis.

Background: Neurology Residency training in Canada is transitioning to competence based medical education (CBME) in July 2020 and the Royal College Neurology Specialty Committee has identified “providing consultation for and managing patients at outlying centers,” to be an entrustable professional activity (EPA). At Western, neurology telephone consultations, from outlying centres, are attended by both the resident and the staff Neurologist. This scenario provides the ideal situation for direct observation and immediate formative feedback. The resident’s performance is assessed using the ’TeleTool’ which utilizes an entrustment scale and has a short narrative portion. Methods: This mixed methods study aims to determine the reliability and validity of the ’TeleTool’ in assessing the performance of the telephone consultation by senior neurology residents. Informed consent was obtained from residents (9) and staff (7) involved. Scores on the entrustment scale and narrative comments were analysed. Results: Information on 30 encounters (involving 9 residents) was collected. TeleTool results demonstrated higher entrustment scores in PGY4 and PGY5 levels. Overall, ratings were consistent across the 7 consultants assessors. Conclusions: The TeleTool was reliable and valid in assessing competence in the telephone consultation and will be a useful tool for assessment of this EPA.

Background: The coronavirus 2019 pandemic has led to restructuring of health care systems and has subsequently had secondary effects on medical education. This study examines the impact on training of surgical residents in Canada. Methods: The study consisted of a 25-question survey for residents and a 22-question survey for program directors, which were distributed electronically through program administrators on July 3rd- July 11th, 2020. Questions sought to elicit residents’ current experiences and gain insight into methods by which to enhance future training. Results: 108 residents and 21 program directors, from various surgical specialties across Canada, completed the survey. Operative exposures were reported to be reduced by 25-100% and 39% of residents were redeployed. However, 89% of residents reported accessing academic half days virtually and 57% had additional online modules. Despite lost time, 100% of program directors confirmed that residents did not require training extensions. Concerns regarding training, personal health, employability and fellowships were raised. 55-70% of residents and program directors advocated for alternative educational courses, increasing elective time, utilizing simulation for assessment and flexibility in crediting different training experiences. Conclusions: Canadian surgical residents had a significant reduction in operative experiences during the pandemic. Moving forward, it will be important to find alternative educational experiences.

Background: Competence by Design (CBD), a new outcomes-based approach to medical education, has been recently introduced into neurosurgical programs across Canada. A cornerstone of this educational paradigm shift requires evaluation of residents’ performances of entrustable professional activities (EPAs). This study aimed to define Faculty expectations and markers of competence for resident EPA performances. Methods: Canada-wide survey of neurosurgical Faculty (NSF) with a 55-item online questionnaire referencing 15/45 available core neurosurgery EPAs. Results: Of the 52 respondents, majority believed that being able to perform safely (98%), effectively (92%) and independently (90%) and being able to adapt to contextual complexities of the case (88%) and unexpected events (88%) represented necessary qualities for demonstrating competence achievement of an EPA. Performing efficiently, without supervision and responding to rare events were all considered less important. On average, NSF believed that at least five separate assessments involving two or more different assessors were necessary for documenting competence achievement of each EPA. Proportion believing EPAs were representative of general neurosurgery competences varied significantly across all EPAs (p<0.00001) with >25% believing 5/15 EPAs required fellowship training. Conclusions: This study defined expectations and indicators of competent surgical performance and revealed a significant debate regarding perceived appropriateness of current EPAs for general neurosurgical training.