Tracking the changes in longitudinal MRI-detected perivascular spaces following ischaemic stroke.

INTRODUCTION: Stroke is a leading cause of mortality and morbidity worldwide. Magnetic resonance imaging-visible perivascular spaces (PVS) are an emerging marker of cerebral small vessel disease and may have prognostic value in stroke. We aimed to characterise longitudinal changes in PVS volume and cluster count following ischaemic stroke. PATIENTS AND METHODS: Perivascular space volumes and cluster counts were compared between stroke survivors (n = 124; 39 women; median [Q1, Q3] age = 70 [62, 76] years) and healthy controls (n = 39; 15 women; median age = 69 [66, 72.5] years). Magnetic resonance imaging scans were acquired at 3 months, 12 months and 36 months post-stroke. Perivascular spaces were automatically segmented from T1-weighted MRI using a validated deep learning algorithm (nnU-Net). Generalised linear mixed-effects models were used to assess group differences and longitudinal changes in PVS, adjusting for baseline age, sex, total intracranial volume and body mass index. RESULTS: At the 3-month timepoint, whole-brain PVS metrics were significantly greater in the stroke group than in controls. By 36 months, stroke patients demonstrated significant PVS reductions relative to controls in the frontal lobe (PVS volume: exp(β) = 0.93; 95% CI, 0.82, 0.99, P = .032; PVS cluster count: exp(β) = 0.91; 95% CI, 0.83, 1; P = .037). DISCUSSION: Contrary to age-related PVS enlargement observed in controls, stroke survivors showed significant longitudinal reductions in PVS volume and cluster counts over 36 months. These findings suggest that MRI-visible PVS trajectories after stroke are dynamic and region-specific, challenging the interpretation of PVS enlargement as a simple marker of cerebrovascular disease burden. CONCLUSION: Ischaemic stroke is associated with dynamic and regional changes in PVS volume and count.