The expansion and severity of chronic MS lesions follows a periventricular gradient

Background and Objectives: Expansion of chronic lesions in multiple sclerosis (MS) patients and recently described cerebrospinal fluid (CSF)-related gradient of tissue damage are linked to microglial activation. The aim of this study was to investigate whether lesion expansion is associated with proximity to ventricular CSF spaces. Methods: Pre- and post-gadolinium three-dimensional (3D)-T1, 3D FLAIR and diffusion tensor images were acquired from 36 relapsing-remitting MS (RRMS) patients. Lesional activity was analysed between baseline and 48 months at different distances from the CSF using successive 1 mm thick concentric bands radiating from the ventricles. Results: Voxel-based analysis of the rate of lesion expansion demonstrated a clear periventricular gradient decreasing away from the ventricles. This was particularly apparent when lesions of equal diameter were analysed. Periventricular lesional tissue showed higher degree of tissue destruction at baseline that significantly increased during follow-up in bands close to CSF. This longitudinal change was proportional to degree of lesion expansion. Lesion-wise analysis revealed a gradual, centrifugal decrease in the proportion of expanding lesions from the immediate periventricular zone. Discussion: Our data suggest that chronic white matter lesions in close proximity to the ventricles are more destructive, show a higher degree of expansion at the lesion border and accelerated tissue loss in the lesion core.