Cerebellar gray matter lesions are common in pediatric multiple sclerosis at clinical onset.

Background: No data are available on the occurrence of gray matter lesions (GML) in the cerebellum of pediatric multiple sclerosis (pedMS). Objectives: We analyzed frequency, number and topography of GML, and their correlation with cerebellar-related disability in pedMS at clinical onset. Methods: Fifteen adolescents with pedMS (12F/3M; mean age 14.9 ± 2.2, range 11-17) were studied. Neurological and cognitive evaluations were done by means of EDSS, Trail Making Test-Part B (TMT-B) and Symbol Digit Modalities Test-oral version (SDMT). Cerebellar GML were investigated with double inversion recovery (DIR) and phase-sensitive inversion recovery (PSIR) sequences obtained with a 3 T-MRI scan. Results: All patients had white matter lesions (WML) and/or GML in the cerebellum. A significantly higher GML number was observed on PSIR compared to DIR (mean 2.3 ± 2.3 vs 1.1 ± 1.6; median 2.0 (IQR 1.0-2.0) vs 1.0 (IQR 0.0-1.5); p = 0.004). GML were observed in 14/15 (93.3%) patients and were more frequent in the posterior than in the anterior lobe (mean 1.8 ± 2.2 vs 0.47 ± 0.74; median 2.0 (IQR 0.5-2.0) vs 0.0 (IQR 0.0-1.0); p = 0.044). No correlation was found between lesion number or topography and EDSS (r = 0.12, p = 0.69), TMT-B and SDMT. Conclusion: At clinical onset, cerebellar GML are common in pedMS, are very often asymptomatic, do not correlate with physical and cognitive disability, and more frequently affect the posterior lobe.