Purpose: Although previous guidelines have established the anatomic landmarks for avoiding facial nerve injury during aesthetic and reconstructive procedures, reports of injuries persist. Facial nerve paralysis can be a potentially devastating complication.

The purpose of our study was to identify the terminal anatomy and intramuscular innervation of the upper branches of the facial nerve.

Methods: Fifteen anatomic dissections were performed on nine formalin-fixed cadaver heads. Magnifying loupes(4X) and a surgical microscope(100X) were used in tracing the facial nerve from the sylomastoid foramen through to it's terminal innervation into the frontalis, orbicularis oculi, and zygomaticus muscles. Tissue sectioning permitted identification of neuromuscular junctions.

Results: The frontalis muscle is innervated by 1-3 (average 1.7) terminal temporal branches. A dual innervation was witnessed in 46.7% of our dissections. Intramuscular innervation occured 27-55 mm from a medial-lateral canthal baseline. Axial, plexiform, and combination of branching patterns were identified. Neuromuscular junctions (80%) were located along the inferolateral portion of the muscle.

Conclusion: With an increasing number of deeper dissections and brow lifts performed for facial rejuvenation, precise anatomic knowledge of the terminal anatomy of the facial nerve is mandatory. Our dissections detail the specific branching patterns and plane of travel for avoiding nerve injury.