CROSSED APHASIA ELICITED BY DIRECT CORTICAL STIMULATION

Abstract

I read with interest the article by Oishi et al.1 They report a patient with a right frontal tumor who was strongly right handed (Edinburgh Handedness Inventory) but had aphasic seizures and was dominant for speech on the right hemisphere by Wada test. They inserted subdural electrodes and were able to show that during electrical stimulation of one electrode placed over the right inferior frontal gyrus the patient was unable to speak (count numbers, speak spontaneously, or name objects) with totally intact auditory comprehension (he was able to point at requested objects). They concluded that the electrode was placed over Broca area, in a case of crossed aphasia. Unfortunately, the evidence presented by the authors is not sufficient to conclude that they localized language by cortical stimulation. In a high percentage of cases, electrical stimulation in the inferior frontal area immediately anterior to the primary motor area (MI) of the face produces negative motor signs with inability to move the tongue, the eyes, or other distal muscles of the face or extremities. Negative motor areas exist on the dominant and on the nondominant frontal lobes.2,3 A negative motor effect on tongue movements always is associated with inability to speak but intact comprehension. Therefore, in cases where stimulation of the inferior frontal gyrus produces inability to …