The pyramidal tract in congenital hemiparesis: Relationship between morphology and function in periventricular lesions

Three-dimensional MRI data sets were obtained from 12 young adult patients with congenital spastic hemiparesis caused by unilateral periventricular wh ite matter lesions. The impact of these lesions on corticospinal projection s to the upper and lower extremities was assessed on reconstructed semi-cor onal planes following anatomical landmarks of somatotopic organization in t he precentral gyrus and in the internal capsule: a more anterior plane runn ing through the hand-knob of the precentral gyrus and the anterior portion of the posterior limb of the internal capsule representing projections to t he upper extremity, and a more posterior plane running through the top of t he precentral gyrus and the middle portion of the posterior limb of the int ernal capsule representing projections to the lower extremity. In addition, the total lesion extent was determined volumetrically, and Wallerian degen eration was assessed qualitatively in the internal capsule and quantitative ly by measuring brainstem asymmetry. We found a strong correlation between motor dysfunction of the upper and lower limb and the lateral extent of the periventricular lesion measured on the respective semi-coronal planes. The total lesion volume and the degree of Wallerian degeneration correlated le ss strongly, both reaching statistical significance only with motor impairm ent of the hand.