Somesthetic disconnection syndromes in patients with callosal lesions.

Somesthetic disconnection syndromes were investigated in relation to the sites of lesions in the corpus callosum in 3 patients with callosal lesions, in order to identify the callosal regions responsible for the interhemispheric transfer of somesthetic information. Cases 1 and 2 with lesions in the posterior truncus exhibited transfer deficits of discriminative sensations between the left and right hands, left-sided tactile anomia and left-sided somesthetic alexia. Case 3 with lesions in the posteroventral part of the posterior truncus showed no signs of somesthetic disconnection syndromes. The results suggest the importance of the anterior and/or dorsal part of the posterior truncus of the corpus callosum for interhemispheric transfer of the discriminative sensations and integrated somesthetic information necessary for tactile naming and somesthetic reading.