Surgical anatomy of the platysma motor branch as a donor for transfer in brachial plexus repair.

OBJECT: Nerve transfers have become a major weapon in the battle against brachial plexus lesions. Recently, a case involving the successful use of the platysma motor branch to re-innervate the pectoralis major muscle was reported. The present anatomical study was conducted to clarify the surgical anatomy of the platysma motor nerve, in view of its potential use as a donor for transfer.
METHODS: Microsurgical dissections of the facial nerve and its terminal branches were performed bilaterally in five formaldehyde-fixed cadavers, thereby yielding ten samples for study. The relationships between the platysma motor branch and adjacent structures were studied and measurements performed. Specimens were removed and histologically studied.
RESULTS: The platysma branch of the facial nerve was found to arise from the cervicofacial trunk. In five instances, one main nerve innervated the platysma muscle, and there was a smaller accessory nerve; in four cases, there was just a single branch to the muscle; and in one case, there was a main branch and two accessory branches. The distance between the gonion and the platysma motor branch averaged 0.8 cm (range 0.4-1.1 cm). The platysma branch received thin anastomotic rami from the transverse superficial cervical plexus. The neural surface of the platysma motor branch, on average, was 76% the surface area of the medial pectoral nerve.
CONCLUSION: The anatomy of the platysma motor branch is predictable. Contraction of the platysma muscle is under voluntary control, which is an important quality for a donor nerve selected for transfer. The clinical usefulness of platysma motor branch transfer still must be elucidated.