(Kiosk 1) Identifying Median Neuropathy at the Ligament of Struthers Using Ultrasound: A Case Report

Case Diagnosis: 19-year-old male with persistent numbness and weakness in right hand after polytrauma

Case Description or Program Description: Patient sustained a fall from fifty feet and sustained multiple injuries, most notably right olecranon, right capitate, and right scaphoid fractures with subsequent surgical fixation. Three days after surgery, he developed first through third digit numbness and weakness of the abductor pollicis brevis (APB). He was taken for carpal tunnel release for presumed acute carpal tunnel syndrome. This release did not improve his symptoms and outpatient electromyography and nerve conduction studies (EMG/NCS) were ordered after discharge from inpatient rehabilitation.

Setting: Outpatient electromyography clinic

Assessment/Results: EMG/NCS showed prolonged latency and decreased amplitude median motor studies and absent median sensory studies. EMG showed active denervation findings in the pronator teres and flexor pollicis longus, indicating a proximal entrapment scenario. Ultrasound was used to evaluate the median nerve from the mid humerus to the wrist. More proximally, around the ligament of Struthers, the median nerve appeared swollen with a cross-sectional area of 17-21 millimeter squared. Just distally to this it appeared 9 millimeters squared. Given these findings, in conjunction with EMG/NCS results, the entrapment most likely was caused at the ligament of Struthers.

Discussion (relevance): EMG/NCS is a vital tool in diagnosis of entrapment neuropathies, though it has limitations. Particularly, in more rare situations of proximal median entrapment neuropathies, specific localization of entrapment is often difficult. In these circumstances, neuromuscular ultrasound examination is particularly useful. In our case, we were able to highlight this usefulness by using scanning techniques and measurement features available on nearly all ultrasound machines to show differential median nerve edema.

Conclusions: Alone, EMG/NCS and ultrasound are invaluable tools for diagnosis of entrapment neuropathies, but when utilized together, their value is synergistic.