Beyond Gross Motor Function: The Association Between Fine Motor Skills and Cognitive Development in Treated SMA Type 1

Background: Disease-modifying therapies (DMTs) have transformed the natural history of spinal muscular atrophy (SMA) type 1, revealing heterogeneous developmental trajectories and renewing interest in cognitive and language outcomes beyond gross motor function. Within an embodied cognition framework, sensorimotor experience, object manipulation, and interactions with the environment may shape early cognitive development. This study aimed to describe the cognitive, language, and motor development of treated children with SMA type 1 and to explore associations between gross motor abilities and neurodevelopmental outcomes. Methods: A retrospective observational study included 32 children aged 18–30 months with confirmed SMA type 1. Participants were assessed using the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) at baseline (T0) and both CHOP-INTEND and the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III) at the time of neurodevelopmental assessment (T1). Associations among Fine Motor, Cognitive, Language, and Gross Motor scores were examined using Spearman’s correlations and multivariable rank-based regression. Results: Fine Motor scores showed inter-individual variability and were correlated with Cognitive (ρ = 0.647, p < 0.001) and Language (ρ = 0.753, p < 0.001) scores. The association between Fine Motor and Cognitive performance remained robust even after adjustment for gross motor function, assessed by CHOP-INTEND, indicating that fine motor ability is linked to cognitive outcome irrespective of overall motor severity. Conclusions: In our cohort, fine motor ability was associated with cognitive and language outcomes, regardless of gross motor severity. These findings suggest the important role of neurodevelopmental components, beyond gross motor function alone, supporting their systematic integration into the clinical characterization of children with treated SMA type 1.