Investigating Forearm Muscle Adaptations in Hemiparetic Cerebral Palsy Using Diffusion MRI: Structural Correlates of Grip Strength Deficits

Motivation: Little is known regarding in vivo forearm musculoskeletal adaptations that underlie hand weakness in hemiparetic cerebral palsy (HCP). Goal(s): This study aimed to investigate diffusion MRI derived forearm muscle adaptations in individuals with HCP and typically developing (TD) individuals. Approach: T1- and diffusion-weighted MR images of both forearms were acquired in 30 individuals (14 HCP, 16 TD). Interlimb differences in forearm flexor muscle geometry and DTI-derived estimates, and their impact on hand grip strength, were evaluated. Results: In HCP, affected muscles had significantly reduced muscle volume, diffusivity, and fascicle lengths. Reduced muscle volume and diffusivity together explained 62% of the grip strength deficit. Impact: Decreased muscle volume and altered microstructure, as indicated by reduced diffusivity, contribute to functional impairments in HCP. DTI-based diffusivity metrics non-invasively reveal crucial insights into pathophysiological changes in muscle tissue, such as muscle atrophy and fibrosis.