Body Composition in Children With Spinal Muscular Atrophy Types 2 and 3 Receiving Nusinersen Treatment: A Longitudinal Cohort Study.

Introduction/aims: Body composition was reported as a biomarker of muscle atrophy in the natural history of children with spinal muscular atrophy (SMA). We aimed to analyze longitudinal changes in the body composition of patients receiving nusinersen treatment and to investigate its correlation with functional motor assessments.

Methods: This cohort study enrolled patients with SMA types 2 and 3 receiving nusinersen treatment for 14 months. Data including fat-free mass (FFM), muscle mass (MM) and their indexes, and Hammersmith Functional Motor Scale Expanded (HFMSE) scores at baseline and at 6, 10, and 14 months were analyzed.

Results: Forty-six patients with SMA type 2 and 3, median age at initial treatment 7.1(4.6-10.4) years, were included, with 25 males and 21 females. Compared with the baseline, FFM, MM, and indexes of both significantly increased during 14 months (p < 0.05) while body fat mass index showed no significant change (p = 0.18). Significant increases were noted in HFMSE scores (p < 0.001), which were moderately correlated with FFM index and MM index. The associations between HFMSE and muscle-related variables were strong in children who achieved walking at baseline.

Discussion: Body composition changes in muscle-related variables were found in children with SMA types 2 and 3 who received nusinersen treatment. Higher muscle mass was associated with better motor function.