1. An amplified description of the anatomy of the palmaris brevis muscle based on dissections of ten cadaver hands is reported. Specific details regarding its shape, attachments, its bipartite structure with separate innervation to each part, and presence of tendons are noted.
2. Structural boundaries of the pisohamate tunnel (loge of Guyon) are described, based on these dissections.
3. The function of the palmaris brevis is believed to be to protect the ulnar nerve and artery from overlying pressure. Contraction of the muscle appears to prevent displacement of the hypothenar pad by the pressure produced by gripping hard objects. As a result this pad of soft tissue is maintained over the ulnar neurovascular bundle and the risk of trauma to the nerve and artery from prolonged pressure is minimized.
4. In view of this possible function, we believe that in the surgical approach to this region the integrity of the palmaris brevis should be preserved.