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Facial Nerve Supply to the Orbicularis Oculi around the Lower Eyelid: Anatomy and Its Clinical Implications

Background: The motor innervation of the lower orbicularis oculi has not been clearly established. There is a discrepancy between anatomical descriptions and clinical outcomes of the motor innervation of the pretarsal orbicularis oculi muscle. Therefore, the purposes of this study were to identify every motor and sensory nerve of the lower eyelid, and to reveal the detailed motor nerve pathways toward the medial canthal area. Methods: Fresh cadaver dissections were performed on 50 hemifaces under a surgical microscope. Submuscular and intramuscular nerves of the lower eyelid were identified, and the pathways of facial nerves that ran toward the medial canthus were traced. Results: Vertical submuscular nerves at the lower eyelid originated from the infraorbital foramen, indicating that all were sensory nerves. The zygomatic branch of the facial nerve traveled obliquely through the anterior cheek and supplied the orbicularis oculi of the lower eyelid and the medial portion of the upper eyelid. Its route was defined as a clinically useful line, the medial orbicularis motor line. In addition, the nerve innervating the pretarsal orbicularis oculi arose at the superomedial preseptal area and extended horizontally and laterally. Interestingly, the angular nerve appeared not to innervate the palpebral orbicularis oculi. Conclusions: In the lower eyelid, the vertical sensory and the oblique motor nerve supplies are independent and clearly distinguished in aspect of their own routes. The medial orbicularis motor line represents the motor route to the medial portion of the orbicularis oculi. These results might provide valuable knowledge about surgical anatomy for safe lower blepharoplasty with or without midface lift.