CORTICAL TONGUE AREA STUDIED BY CHRONICALLY IMPLANTED SUBDURAL ELECTRODES - WITH SPECIAL REFERENCE TO PARIETAL MOTOR AND FRONTAL SENSORY RESPONSES

Motor and sensory cortical tongue representations were examined in 40 patients with intractable seizures who underwent chronic subdural elec trode grid implantation. Tongue responses were observed in a wide area 4.5 cm anterior and 3 cm posterior to the central sulcus. The distrib ution of the responses was not influenced by whether the responses wer e unilateral or bilateral. In patients with fronto-parietal lesions, t he tongue motor area was located significantly more superior to the Sy lvian fissure and more anterior to the central sulcus than was the ton gue motor area of patients without organic lesion. Both motor and sens ory responses were found outside of the classic precentral or postcent ral area on the lateral surface of the cortex. Motor responses ('parie tal motor responses') could occur posterior to the central sulcus and, rarely, sensory responses (frontal sensory responses') were identifie d anterior to the central sulcus. These paradoxical parietal motor and frontal sensory responses were seen in 17 out of 40 (42.5%) patients. Nine of these 17 patients had no organic brain lesion on MRI. Clinica l factors, such as patient's age, duration of seizures and cognitive f unctions (IQ, word fluency score), did not influence the frequency of the paradoxical responses. However, patients with brain lesions showed a tendency to have associated paradoxical responses (P < 0.05). In co nclusion, paradoxical responses are not uncommon in epilepsy patients, particularly in those with organic lesions. The physiological and cli nical implications of the paradoxical responses are discussed.