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Background: Genetic polymorphisms like apolipoprotein E (APOE) and microtubule-associated protein tau (MAPT) genes increase the risk of neurodegeneration., Methods: 38 former players (age 52.63±14.02) of contact sports underwent neuroimaging, biofluid collection, and comprehensive neuropsychological assessment. The [F-18]AV-1451 tracer signal was compared in the cortical grey matter between APOE4 allele carriers and non-carriers as well as carriers of MAPT H1H1 vs non-H1H1. Participants were then divided into the high (N = 13) and low (N = 13) groups based on cortical PET tau standard uptake value ratios (SUVRs) for comparison., Findings: Cortical grey matter PET tau SUVR values were significantly higher in APOE4 carriers compared to non-carriers (p = 0.020). In contrast, there was no significant difference in SUVR between MAPT H1H1 vs non-H1H1 carrier genes (p = 1.00). There was a significantly higher APOE4 allele frequency in the high cortical grey matter PET tau group, comparing to low cortical grey matter PET tau group (p = 0.048). No significant difference in neuropsychological function was found between APOE4 allele carriers and non-carriers., Interpretation: There is an association between higher cortical grey matter tau burden as seen with [F-18]AV-1451 PET tracer SUVR, and the APOE4 allele in former professional and semi-professional players at high risk of concussions. APOE4 allele may be a risk factor for tau accumulation in former contact sports athletes at high risk of neurodegeneration., Funding: Toronto General and Western Hospital Foundations; Weston Brain Institute; Canadian Consortium on Neurodegeneration in ageing; Krembil Research Institute. There was no role of the funders in this study., Competing Interests: Declaration of Competing Interest Authors report no conflicts of interest., (Crown Copyright © 2020. Published by Elsevier Inc. All rights reserved.)

Multiple concussions, particularly in contact sports, have been associated with cognitive deficits, psychiatric impairment and neurodegenerative diseases like chronic traumatic encephalopathy. We used volumetric and deformation-based morphometric analyses to test the hypothesis that repeated concussions may be associated with smaller regional brain volumes, poorer cognitive performance and behavioural symptoms among former professional football players compared to healthy controls. This study included fifty-three retired Canadian Football League players, 25 age- and education-matched healthy controls, and controls from the Cambridge Centre for Aging and Neuroscience database for validation. Volumetric analyses revealed greater hippocampal atrophy than expected for age in former athletes with multiple concussions than controls and smaller left hippocampal volume was associated with poorer verbal memory performance in the former athletes. Deformation-based morphometry confirmed smaller bilateral hippocampal volume that was associated with poorer verbal memory performance in athletes. Repeated concussions may lead to greater regional atrophy than expected for age.

Objectives: To examine structural integrity loss in the fornix from 5-30 months after moderate and severe traumatic brain injury (TBI) using diffusion tensor imaging., Methods: MRIs were prospectively undertaken in 29 adults with moderate and severe TBI at two time points. Fractional anisotropy (FA) was calculated for the fornix (column/body, right crux and left crux) at 5 and 30 months post-injury., Results: Paired t-tests revealed significant FA reductions with large effect sizes across time in the column/body, p < 0.001, right crux, p < 0.001 and left crux, p < 0.001., Conclusions: These data contribute to the growing body of evidence that loss of white matter continues in moderate and severe TBI even after the acute neurological effects of TBI have resolved. As the fornix plays a critical role in memory, this may be a contributing factor to the poor clinical outcomes observed in these patients.

Background: Over the past four years, West Nile virus (WNV) has become a significant health issue in North America. In 2002, WNV infection made its first appearance in the human population in Canada., Methods: Patients who presented to the University Health Network and Mount Sinai Hospital in Toronto with neurological disease attributed to WNV infection were identified and followed by the neurology service. Clinical features and results of laboratory, electrodiagnostic, radiological and pathological studies are presented., Results: In August and September 2002, 26 patients were admitted with WNV infection; 14 presented with neurological illness. Encephalitis was the most common presentation (11 patients). Eleven patients developed neuromuscular disease; two at presentation and nine after encephalitis. While the majority had a motor process that localized to the anterior horn cell and/or motor neuron, two patients had evidence of a demyelinating neuropathy and one a sensorimotor axonal neuropathy. Less common manifestations included rhombencephalitis, ataxia, myelopathy and parkinsonism. Death occurred in four patients; two > 75 years of age, and two who were immunocompromised., Conclusions: The most common neurological manifestation of WNV infection was encephalitis with subsequent neuromuscular involvement. The diversity of clinical and pathological findings, however, suggests widespread involvement of the central and peripheral nervous system. A poorer prognosis for neurological recovery and overall survival was seen in older and immunocompromised patients.