Monitoring of sensory evoked potentials is highly reliable and helpful in the operating room.

Abstract

Because short-latency evoked potentials are relatively resistant to anesthetic agents, they can be used to monitor neural pathways during surgical procedures. The use of median nerve somatosensory evoked potentials to localize the central sulcus is an established aid of indisputable value in neurosurgical procedures involving cortical incisions for resection of certain epileptic foci, vascular malformations, or neoplasms near the central area of the brain. Likewise, recording of intraoperative nerve action potentials is currently regarded as indispensable in management of the neuroma-incontinuity after peripheral nerve trauma, as this evoked potential monitoring technique provides the only reliable method of distinguishing between axonotmetic and neurotmetic lesions. Evoked potential monitoring has been of value during many other types of surgical procedures, including cerebral aneurysm clipping, carotid endarterectomy, aortic procedures, microvascular decompression for trigeminal neuralgia and hemifacial spasm, acoustic neuroma resection, and a variety of spinal procedures. A detailed review of the literature is presented on the use of evoked potential monitoring for one of the more common indications: scoliosis surgery. Many orthopedic surgeons use the "wake-up test" only if the somatosensory evoked potentials change during surgery. A detailed review of the few reported cases of "false negative" evoked potentials is presented. The dearth of convincing reports of such phenomena in the face of so many positive experiences should persuade even the skeptical that monitoring of evoked potentials is a highly reliable and helpful intraoperative tool.