Pseudo-anterior interosseous nerve syndrome.

The anterior interosseous nerve syndrome (AINS) is well known. A case is presented that had electromyographic findings limited to the distribution of the anterior interosseous nerve. A small area of sensory loss and slight asymmetry of amplitudes noted on median nerve conduction studies were inconsistent with an AIN syndrome. An antecubital level partial median nerve compromise primarily involving the bundles that form the anterior interosseous nerve was surgically noted. This case illustrates that localization of a peripheral nerve lesion must include consideration of the internal topography of peripheral nerves.