MRI structural connectivity, disruption of primary sensorimotor pathways, and hand function in cerebral palsy.

Brain injury and subsequent plasticity of sensory and corticospinal pathways play an integral role in determining paretic hand function in congenital hemiplegia. There is limited knowledge regarding the relationship between the disruption of sensorimotor thalamic pathways projecting into the primary motor cortex and motor control. This study sought to investigate the relationship between the structural connectivity of motor networks that anatomically link the brain stem with the precentral and postcentral gyri with paretic motor sensory function by using an automated analysis strategy. Magnetic resonance imaging structural connectivity was measured by using high-angular-resolution diffusion imaging, probabilistic tractography, and the anatomic parcellation of high-resolution structural images in 16 children with congenital unilateral periventricular white-matter damage. Connectivity of the corticospinal and corticothalamic pathways was determined by using an asymmetry index based on the number of streamlines contained within these projections and compared with measures of paretic hand function and bimanual coordination. For cortical development, the volume of the ipsilesional precentral gyrus was significantly reduced. For connectivity measures, the numbers of streamlines in corticospinal tracts and corticothalamic pathways within the ipsilesional hemisphere were decreased compared with the contralesional side. The sensorimotor thalamic projections were more significantly correlated with paretic hand functions than were the corticospinal tracts. These data support the concept that preservation of sensorimotor thalamic pathways that directly project into the primary motor cortex has more influence on motor function control of the paretic hand than does preservation of corticospinal tracts.