Intraoperative SSEP detection of UInar nerve compression or ischemia in anobese patient: A unique complication associated with a specialized spinal retraction system

Objective: To report a case of peripheral nerve compression caused by a spe cialized spinal retraction system, the Thompson-Farley retractor system, th at most likely would not have been detected without intraoperative monitori ng of the ulnar nerve. Design: Bilateral median and peroneal nerve somatosensory evoked potentials (SSEPs) were monitored continuously during a C5 corpectomy, as was fore bo dy temperature. Results: Within minutes after cervical soft-tissue retraction, the left uln ar nerve SSEP began to decline in amplitude. Peroneal nerve SSEPs were norm al throughout the surgery; care body temperature remained at 36 degrees +/- 0.2 degrees C. After much effort to reposition the patient. the SSEPs retu rned to baseline and the Thompson-Farley system was replaced by a self-retr acting system. Conclusions: To our knowledge, this is the first report of peripheral nerve compression caused by the Thompson-Farley retractor system. Even with care ful positioning on the operating table, obese patients may be particularly at risk for upper arm compression. Continuous monitoring of SSEPs is sugges ted to prevent postoperative morbidity.