Interhemispheric transfer in patients with incomplete section of the corpus callosum. Anatomic verification with magnetic resonance imaging

Tests of interhemispheric disconnection including visual, somesthetic, kinesthetic, auditory, and complex motor functions were performed on seven patients with chronic epilepsy who had undergone partial surgical section of the corpus callosum, verified by magnetic resonance imaging. Two patients with only one third of the splenium remaining demonstrated disconnection syndromes involving all modalities except vision, which was completely intact. Five patients had lesions involving the rostrum and the anterior two thirds to four fifths of the body of the callosum, with the splenium spared. They demonstrated little evidence of disconnection in the modalities indicated, except for left ear suppression on a dichotic listening task and partial somatosensory disruption in some cases. These results emphasize the importance of the posterior corpus callosum for interhemispheric sensory and sensorimotor transfer, although some discrepancies between current behavioral data and previous anatomic findings remain.