The anterior interosseous nerve syndrome.

A review of the literature pertaining to the anterior interosseous nerve (AIN) syndrome revealed that the diagnostic criteria for this syndrome need to be defined. The authors describe the etiology of the AIN syndrome and use two cases of their own and 52 cases reported in the English literature to draw up a definition of the diagnostic criteria. The recommended criteria are: (a) demonstrable weakness of muscles innervated by the anterior interosseous nerve; (b) electromyographic findings of marked denervation potentials and decreased or absent voluntary motor unit potentials of these muscles; (c) operative evidence of entrapment of, or injury to, the anterior interosseous nerve; and (d) improved power in the muscles and reversal of the electromyographic changes on follow-up after operation.