Somatosensory evoked potentials over the non-affected hemisphere in patients with unilateral cerebrovascular lesions

Changes in somatosensory evoked potentials (SEPs) over the non-affected hemisphere in 61 patients with unilateral cerebrovascular lesions were studied using age-matched controls. The latencies showed no significant differences when compared to controls. In cerebral infarctions produced by occlusion of the perforating artery in the middle cerebral artery (MCA), the amplitudes over the non-affected hemisphere decreased in the acute phases, but did not change in the chronic phases in comparison with the controls; whereas in cerebral infarctions produced by occlusion of the cortical artery in the MCA, the amplitudes over the non-affected hemisphere increased in the chronic phases compared to controls. The amplitudes over the non-affected hemisphere in intracerebral hemorrhages (ICH) increased in the chronic phases in comparison with the controls, but in the acute phases, they showed no change in the cortical artery group nor in ICH. The increases in the amplitudes were more prominent in patients with than in patients without sensory impairment. These data suggest that the affected hemisphere gives rise to high amplitude SEPs over the non-affected hemisphere.