A Case Report on Unilateral Accessory Humeral Head of Pronator Teres.

The presence of an accessory muscle in the forearm is likely to compress on the neurovascular structures and has clinical implications. We encountered an accessory humeral head of pronator teres during routine dissection of left upper limb in a male cadaver. The accessory head had fleshy origin from medial supracondylar line, medial intermuscular septum and brachialis fascia. It coursed downwards in the cubital region covering brachial artery and median nerve. Further, it narrowed becoming mostly tendinous and joined with the humeral head of pronator teres. Awareness of accessory head is essential to explain multiple sites of nerve compression. High proximal origin of pronator teres and its course superficial to median nerve makes it more susceptible for distal entrapment neuropathy. Accessory muscles affect surgical field and can be confused with soft tissue pathologies.