Brachialis syndrome: A rare consequence of patient positioning causing postoperative median neuropathy

Background: Poor positioning of patients can result in devastating permanent neurologic deficits. We describe a previously unreported cause of median nerve compression that we have termed the brachialis syndrome, associated with patient positioning that results in permanent median nerve damage. Methods: We identified this condition affecting 6 median nerves. All patients underwent surgical decompression of the proximal median nerve at the level of the antecubital fossa. Results: Five patients presented with symptoms of median nerve compression; 6 affected median nerves manifested brachialis syndrome after a lengthy index surgery. Every patient had a similar presentation characterized by a mixed sensory and motor deficit. Average time to symptom presentation postoperatively was 1 hour. Two patients had delayed time to decompression, one of 25 days and one of 92 days. In the additional patients, the average time to decompression was 19.7 hours. At median nerve decompression, the brachialis was found to have varying degrees of muscle necrosis. In the patients whose decompression was delayed, there was only partial neurologic recovery at follow-up to 1 year. In the patients expeditiously decompressed, full neurologic recovery occurred in 1 to 14 days. Conclusions: This is the first description of the brachialis syndrome. During surgery, arms were placed into full extension, compressing the brachialis against the trochlea. The brachialis reliably developed necrosis, resulting in swelling, compressing the median nerve against the lacertus fibrosus. Two patients with delayed decompression had poor neurologic outcomes. This supports modification of patient positioning, postoperative vigilance, and timely surgical management of brachialis syndrome.