Brachial plexopathy in patients with breast cancer: unusual electromyographic findings in two patients

2 patients with breast cancer developed progressive brachial plexopathy. The unusual electrographic finding in both patients was conduction block (neuropraxia) along the medial cord of the brachial plexus. The plexus was explored in 1 patient. Constrictive connective tissue or another source of nerve entrapment was not identified. The exact cause of the conduction block remains unclear; its presence neither indicates a good prognosis nor an indication for surgical exploration.