Ataxic hemiparesis from small capsular hemorrhage. Computed tomography and somatosensory evoked potentials.

We studied three cases that fit the clinical syndrome of ataxic hemiparesis. Computed tomography revealed small hemorrhages of the posterior limb of the internal capsule in all the cases, and somatosensory evoked potential studies predicted a disturbance of the lemniscal pathway from the thalamus to the parietal sensory cortex without demonstrable sensory loss. These results suggested that ataxia of the contralateral limbs following capsular lesion might result from a disruption of the thalamocortical sensory projection. The site of the lesion, the pathologic cause, and the underlying mechanism of ataxia are not necessarily homogeneous within the syndrome.