Intraoperative detection of cerebral ischemia with somatosensory cortical evoked potentials during carotid endarterectomy--presentation of a new method.

Somatosensory evoked potentials (SEP) are an objective measure of cerebral function. They depend on the integrity of cortical blood flow. After stimulation of the median nerve, SEP of subcortical and cortical origin can be recorded within a short time during carotid surgery by means of 3 scalp electrodes. Intraoperative SEP recordings are more resistant to anesthetic influence than is the EEG. In a 69-year-old woman, monitoring with SEP gave an early warning of cerebral ischemia during carotid endarterectomy. The cortical SEP disappeared immediately after carotid cross-clamping. The entire loss of the cortical SEP was associated with a new neurologic deficit postoperatively. This technique is simple and convenient to use and appears to be predictive of neurologic outcome.