Intraoperative identification of the central sulcus: a practical method.

A practical method of intraoperative identification of the central sulcus using cortical evoked potentials (EP) was reported. The method herein proposed is unique with stimulation to the trigeminal and tibial nerve in addition to median nerve stimulation, depending on the location of the lesion. Thus, a wide coverage of the rolandic fissure was possible. Eighteen adult patients with peri-rolandic lesions were investigated. Fourteen cases had a malignant tumour but all except 3 showed only a minor neurological deficit preoperatively. In 13 cases, the central sulcus could be identified through the phenomenon of the phase-reversal of cortical EP across the central fissure. Of the remaining 5 cases, cortical EP were not detected in 3 (all showed hemiplegia and/or aphasia) and EP without phase-reversal were obtained in 2. As a result, in most cases showing only a trivial neurological deficit before surgery, aggressive removal of the tumour was successfully carried out without producing severe motor dysfunction.