Anatomical study of the variations in innervation of the orbicularis oculi by the facial nerve.

While the divisions of the facial nerve in the face are well known, the innervation of the orbicularis oculi by the different distal branches of the facial nerve is poorly described. To determine which branches of the facial nerve play a role in this innervation, the facial nerve was dissected in 30 fresh cadavers. The innervation of this muscle was in the form of two plexuses, a superior one, most often (93%) formed by the union of the temporal and superior zygomatic branches, and an inferior one, usually formed (63%) by the union of the inferior zygomatic and superior buccal branches. This new mode of innervation explains how, without damage to both plexuses, innervation of orbicularis oculi by the facial nerve remains functional. It also explains the often unsatisfactory results of treatment of primary blepharospasm, and the unusual character of palsies of this muscle in cervicofacial lifts.