Background Although previously thought to be asymptomatic, recent studies have suggested that magnetic resonance imaging–visible perivascular spaces (PVS) in the basal ganglia (BG‐PVS) of patients with Parkinson's disease (PD) may be markers of motor disability and cognitive decline. In addition, a pathogenic and risk profile difference between small (≤3‐mm diameter) and large (>3‐mm diameter) PVS has been suggested. Objective The aim of this study was to examine associations between quantitative measures of large and small BG‐PVS, global cognition, and motor/nonmotor features in a multicenter cohort of patients with PD. Methods We performed a cross‐sectional study examining the association between large and small BG‐PVS with Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS‐UPDRS) Parts I–IV and cognition (Montreal Cognitive Assessment) in 133 patients with PD enrolled in the Ontario Neurodegenerative Disease Research Initiative study. Results Patients with PD with small BG‐PVS demonstrated an association with MDS‐UPDRS Parts I (P = 0.008) and II (both P = 0.02), whereas patients with large BG‐PVS demonstrated an association with MDS‐UPDRS Parts III (P < 0.0001) and IV (P < 0.001). BG‐PVS were not correlated with cognition. Conclusions Small BG‐PVS are associated with motor and nonmotor aspects of experiences in daily living, while large BG‐PVS are associated with the motor symptoms and motor complications. © 2022 International Parkinson and Movement Disorder Society

Introduction We examine whether distinct brain atrophy patterns (using brain parenchymal fraction [BPF]) differentially predict functional performance and decline in Alzheimer's disease (AD), and are independently moderated by (1) a key AD genetic risk marker (apolipoprotein E [ APOE ]), (2) sex, and (3) high‐risk group (women APOE ɛ4 carriers). Methods We used a 2‐year longitudinal sample of AD patients (baseline N = 170; mean age = 71.3 [9.1] years) from the Sunnybrook Dementia Study. We applied latent class analysis, latent growth modeling, and path analysis. We aimed to replicate our findings ( N = 184) in the Alzheimer's Disease Neuroimaging Initiative. Results We observed that high brain atrophy class predicted lower functional performance and steeper decline. This association was moderated by APOE , sex, and high‐risk group. Baseline findings as moderated by APOE and high‐risk group were replicated. Discussion Women APOE ɛ4 carriers may selectively be at a greater risk of functional impairment with higher brain atrophy.