Quantifying structural properties of forearm flexor muscles in individuals with hemiparetic cerebral palsy using diffusion tensor imaging.

This study investigated diffusion tensor imaging (DTI) derived macro- and micro-structural musculoskeletal adaptations in forearm flexor muscles in individuals with hemiparetic cerebral palsy (HCP) and typically developing (TD) individuals, and their relationship to reduced grip strength. In 14 individuals with HCP and 16 TD individuals, T1-weighted and diffusion-weighted magnetic resonance images of both forearms were acquired, and maximum grip strength was measured. In two forearm flexors, muscle volume, DTI-based diffusivity metrics, and probabilistic tractography derived fascicle architecture was estimated. Linear mixed-effects models evaluated interlimb differences in structural parameters and their impact on grip strength. In the HCP group, paretic muscles showed significant reductions in volume, diffusivity values, fascicle lengths, and physiological cross-sectional area as compared to nonparetic forearm and TD participants. Furthermore, reduced muscle volume and diffusivity together explained 62% of the grip strength deficit. These findings demonstrate that decreased muscle volume and altered microstructure, as indicated by reduced diffusivity, contribute significantly 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. Future therapies should focus on both muscle macro- and micro-structural adaptations as targets to improve motor function in HCP.