[Monitoring somatosensory evoked potentials during carotid endarterectomy]

The tromboembolic and ischemic events during carotid endarterectomy can be avoided or detected with appropriate monitoring. Median nerve somatosensory evoked potentials recorded from the parietal cortex correlate with the blood flow in the middle cerebral artery. The good evoked responses after cross-clamping of the carotid artery indicate a sufficient collateral circulation, enabling a surgery without shunt, thus minimizing the risk of embolisation. Insufficient collateral circulation after cross-camping results in an amplitude reduction of the parietal N20-P25 complex of more than 50%. In this case an ischemic event can be prevented by shunting. As a total 83 carotid endarterectomies were done. In 65 cases (78.3%) the evoked potentials showed no significant alteration, and no postoperative neurological deficit occurred. Seven patients (8.45%) needed to be operated with a shunt, because of cross-clamping ischaemia. One of them presented a transient postoperative hemiparesis, which was predicted by the long-term loss of the SEP-s, and which resolved within 4 hours. Seven further patients (8.45%)--operated primarily with shunt, and 4 patients (4.8%)--monitored with transcranial Doppler sonography, showed no postoperative neurological deficit. We found that median nerve somatosensory evoked potential monitoring during carotid endarterectomy is a simple, sensitive and reliable method.