[The accessory brachial tendon--a rare cause of pronator teres syndrome].

The pronator syndrome is caused by a compression of the median nerve at the level of the elbow. In the case presented bizonal compression of the nerve was seen, first by the lacertus fibrosus, second by an isolated abnormal tendon of the brachialis muscle. The treatment, therefore, includes the early and extensive operative exploration of the nerve, the resection of all compressive structures and sometimes interfascicular neurolysis and transposition of the nerve anterior to the pronator teres, when the nerve is in a badly scarred bed.