Electroneurophysiological monitoring is employed during various supratentorial surgical procedures. EEG and evoked potential monitoring are used to detect and to facilitate the timely correction of cerebral ischemia during carotid endarterectomy and aneurysm surgery. Direct cortical recording and stimulation is used to identify areas or cortex that would be likely to produce clinical deficits if removed. Electrocorticography is used to identify epileptogenic cortex intraoperatively during surgical treatment of epilepsy.