Prognostic value of computerized EEG analysis during carotid endarterectomy.

A single-channel EEG, analyzed in real time to produce a density spectral array (DSA) display was recorded during 111 carotid endarterectomies. A simple protocol that emphasized loss of high frequency activity was used to identify serious ischemic EEG events. In 70 patients (78 operations) with no preoperative neurologic deficits, new postoperative neurologic deficits appeared only in the seven patients who had ischemic EEG events that lasted 10 min or longer. The EEG was not predictive in the 31 patients (33 operations) who had preoperative neurologic deficits: one patient with no intraoperative change in EEG developed a new postoperative deficit, and one patient with EEG changes lasting 13 min had no demonstrable new deficit postoperatively. This EEG monitoring technique was simple and convenient to use, and appears to be predictive of gross neurologic outcome following carotid endarterectomy in patients without preoperative neurologic deficits.