Evoked potential monitoring of the upper extremities during thoracic and lumbar spinal deformity surgery: a prospective study.

We prospectively investigated the usefulness of somatosensory evoked potential (SEP) monitoring to detect clinically significant peripheral nerve or brachial plexus compression in the upper extremities during spinal deformity surgery. All patients had bilateral median and ulnar nerve SEPs evaluated as a baseline, both intermittently throughout the surgical procedure and at termination of surgery. This information was correlated with pre- and postoperative upper extremity neurologic examinations. Twenty-five upper extremities in 21 patients had intraoperative SEP changes consisting of at least a 60% decline in amplitude or a 10% increase in latency. On many occasions, repositioning of the upper extremities improved the SEP responses to acceptable baselines. Overall, SEP monitoring of the upper extremities was 78% sensitive for detecting upper extremity sensory deficits, 100% sensitive for detecting combined sensory and motor deficits, and 98.5% specific for predicting normal postoperative upper extremity function. We recommend the simultaneous electrophysiologic monitoring of the upper and lower extremities during spinal surgery to allow identification of brachial plexus and/or peripheral nerve stretch/compression that may be amenable to intraoperative correction.