(Kiosk 2) Left Posterior Cord Plexopathy from Anterior Shoulder Dislocation in the Setting of Primary Lateral Sclerosis

Case Diagnosis: Posterior Cord Brachial Plexus Injury

Case Description or Program Description: A 64-year-old male with PMH primary lateral sclerosis presented to the emergency department after a fall with left anterior shoulder dislocation with subsequent closed reduction. He initially had left wrist extension and finger extension weakness. At follow-up, the patient was found to have left shoulder abduction weakness. He underwent left upper extremity (LUE) EMG for further evaluation seven weeks after injury.

Setting: Hospital

Assessment/Results: LUE nerve conduction (median, ulnar, and radial nerve) studies were intact. Decreased recruitment with positive waves and fibrillations were appreciated in the left triceps, deltoid, and supinator muscles. With radial nerve palsy localized near the axilla due to triceps involvement and axillary nerve injury seen, posterior cord plexopathy without evidence of radiculopathy was diagnosed.

Discussion (relevance): Shoulder dislocation can cause peripheral nerve or, more rarely, brachial plexus injury. The patient had left posterior cord plexopathy with acute neurogenic findings from an anterior shoulder dislocation.

Conclusions: In the setting of anterior shoulder dislocation, careful consideration should be given in screening for peripheral nerve or brachial plexus injury. Pure cord plexopathies are rare in brachial plexus injuries. Furthermore, motor neuron diseases, such as primary lateral sclerosis, may complicate distinguishing between plexopathies and mononeuropathy clinically. Repeat EMG in 1-3 months could ascertain if evidence of neurogenic recovery is present.