Effects of lesions invading the postcentral gyrus on somatosensory thresholds on the face.

Patients with unilateral removals from either the parietal, frontal or temporal lobe and normal control subjects were examined on three tests of tactile sensibility. The patients with surgical excisions from the parietal lobe were subdivided into two groups: those whose lesions invaded the face area in the primary sensory cortex and those whose lesions spared this area. A significant percentage of patients with lesions that invaded the face area had mild to severe sensory deficits on the side of the face contralateral to the lesion. A much smaller number of patients had deficits on the ipsilateral side. Lesions to the face area in the primary sensory cortex were, however, associated with a lower incidence of severe and persistent sensory deficits when compared to previous results on the effects of lesions to the hand area on the sensory capacity of the hand. These results suggest that there is some preservation of sensory function after damage to the face area in the primary sensory cortex, presumably due to the bilateral representation of the face.