A case of neuralgic amyotrophy manifesting bilateral anterior interosseous nerve syndrome

A 49-year-old woman acutely developed severe bilateral shoulder pain followed by weakness of the right shoulder girdle muscles. Within a few days, an inability to flex the terminal phalanges of the bilateral thumbs and index fingers emerged. Neurologic examination 1 month after the onset of symptoms showed atrophy of the right shoulder girdle muscles and mild decreased cutaneous sensation in the distribution of the right axillary nerve. Needle electromyography examination at this time showed fibrillation potentials in the right deltoid and bilateral flexor pollicus longus muscles. Recruitment of the right deltoid, supra- and infraspinatus muscles was reduced. Motor unit potentials in these muscles were of normal configuration. Nerve conduction studies in the upper limb were normal. She was diagnosed as neuralgic amyotrophy with bilateral anterior interosseous nerve syndrome. 4 months later, the muscles innervated by the bilateral anterior interosseous nerve improved in the muscle strength. Clinical features of this case were compatible with a mononeuropathy multiplex form of neuralgic amyotrophy associated with an autoimmune etiology. We think this case is important for speculating the pathogenesis of neuralgic amyotrophy. This case reminds us that patients with neuralgic amyotrophy sometimes demonstrate anterior interosseous nerve syndrome and most patients manifesting anterior interosseous nerve syndrome are patients with neuralgic amyotrophy.