Early red nucleus atrophy in relapse‐onset multiple sclerosis

No study has investigated red nucleus (RN) atrophy in multiple sclerosis (MS) despite cerebellum and its connections are elective sites of MS-related pathology. In this study, we explore RN atrophy in early MS phases and its association with cerebellar damage (focal lesions and atrophy) and physical disability. Thirty-seven relapse-onset MS (RMS) patients having mean age of 35.6 ± 8.5 (18-56) years and mean disease duration of 1.1 ± 1.5 (0-5) years, and 36 age- and sex-matched healthy controls (HC) were studied. Cerebellar and RN lesions and volumes were analyzed on 3 T-MRI images. RMS did not differ from HC in cerebellar lobe volumes but significantly differed in both right (107.84 ± 13.95 mm³ vs. 99.37 ± 11.53 mm³ , p = .019) and left (109.71 ± 14.94 mm³ vs. 100.47 ± 15.78 mm³ , p = .020) RN volumes. Cerebellar white matter lesion volume (WMLV) inversely correlated with both right and left RN volumes (r = -.333, p = .004 and r = -.298, p = .010, respectively), while no correlation was detected between RN volumes and mean cortical thickness, cerebellar gray matter lesion volume, and supratentorial WMLV (right RN: r = -.147, p = .216; left RN: r = -.153, p = .196). Right, but not left, RN volume inversely correlated with midbrain WMLV (r = -.310, p = .008), while no correlation was observed between whole brainstem WMLV and either RN volumes (right RN: r = -.164, p = .164; left RN: r = -.64, p = .588). Finally, left RN volume correlated with vermis VIIb (r = .297, p = .011) and right interposed nucleus (r = .249, p = .034) volumes. We observed RN atrophy in early RMS, likely resulting from anterograde axonal degeneration starting in cerebellar and midbrain WML. RN atrophy seems a promising marker of neurodegeneration and/or cerebellar damage in RMS.