MRI in unexplained mononeuropathy.

Four young patients with severe unexplained progressive mononeuropathy are described. None had a history of known trauma to the affected limb. In addition to the standard neurologic examination and electrophysiologic studies (nerve conduction studies and electromyography), all underwent neuroimaging of the involved extremity. In three patients, magnetic resonance imaging revealed intrinsic abnormalities of the appropriate nerve. The pattern or absence of magnetic resonance imaging changes directly influenced decisions about surgical exploration of the nerve in all four patients. With the advent of more sophisticated technology, magnetic resonance neurography has become a potent diagnostic tool in the evaluation of disorders of peripheral nerve and muscle.