Anterior interosseous nerve syndrome.

Weakness of the flexor pollicis longus, flexor digitorum profundus and pronator quadratus is usually related to an isolated paralysis of the anterior interosseous nerve in the volar aspect of the forearm. The same syndrome may be caused by lesions of the median nerve in the supracondylar region and by involvement of the fibers assigned to the abovementioned nerve in the medial and lateral cords of the brachial plexus. We report 4 cases of the anterior interosseous nerve syndrome (3 spontaneous and one traumatic), review and discuss etiological factors, clinical features and electromyographic findings in the syndrome.