BSOA - British Society of Orthopaedic Anaesthetists

Introduction: Continuous monitoring of spinal cord function using posterior tibial somatosensory evoked potentials (SSEPs) predicts, and helps reduce, the incidence of post-operative neurological deficits in spinal deformity surgery.  In an attempt to reduce false positives we recently began to monitor ulnar nerve SSEPs as a control for recording electrode function.  It was evident that there was a high rate of isolated intra-operative neurophysiological abnormalities (‘events’) detected in these control records. Ulnar nerve injury is a well documented complication of surgery in the prone position.  Monitoring of the upper limb nerves may give early warning of impending neuropraxia, allowing remedial action before permanent damage occurs.¹

The aim of this audit was to estimate a rate for abnormalities in ulnar nerve SSEPs with current monitoring techniques in patients in the prone position and to investigate possible causative factors, as a pilot for a further formal study.