Innervation of the lower eyelid in relation to blepharoplasty and midface lift: Clinical observation and cadaveric study

Ectropion or scleral show resulting from weakness of the lower eyelids is n ot uncommon after lower blepharoplasty or midface lift via blepharoplasty i ncision. Denervation of the pretarsal orbicularis oculi muscle (OOM) attrib utes to such complications. The authors analyzed 102 patients who underwent midface lift via lower blepharoplasty incision for the past 3 years and in vestigated the motor nerve innervation of the lower OOM in 20 cadavers. The y encountered two cases of ectropion attributed to the denervation of the p retarsal OOM: one with dry-eye syndrome and scleral show, and the other wit h a "polar bear-like appearance" (i.e., outer eversion of the lower eyelid) , All pretarsal and preseptal OOMs were innervated by five to seven termina l twigs of the zygomatic branches of the facial nerve that approached the m uscle at a right angle. The medial portion of the lower OOM was innervated by one to two terminal twigs of the buccal branch, and the middle portion w as innervated with two to three twigs of the zygomatic branch. The lateral portion was supplied by tile uppermost zygomatic branch, which split into t wo to four twigs. The mean horizontal distance between the lateral canthus and the zygomatic branch was 2.31 +/- 0.29 cm (range, 1.7-2.7 cm) and the v ertical distance was 1.20 +/- 0.20 cm (range, 0.8-1.5 cm), The critical zon e was a circle with 0.5-cm radius, and its center was located 2.5 cm infero laterally (30 deg) from the lateral canthus. It is very important to unders tand the motor nerve innervation of the lower eyelid and the "critical zone " to avoid postoperative ectropion or weakness of the lower eyelid resultin g from paralysis of the pretarsal or preseptal OOM.