Anatomy of facial and trigeminal nerve branches associated with the corrugator supercilii muscle: microdissection and modified Sihler staining.

BACKGROUND: Deactivation of the corrugator supercilii for the treatment of unintentional glabellar lines requires high selectivity to avoid sensory complications. OBJECTIVE: The aim of this study was to delineate the topographic anatomy of facial and trigeminal nerves in relation to the corrugator supercilii to improve the selectivity and safety of deactivation of the corrugator supercilii muscle. MATERIALS AND METHODS: The number, courses, and attachments of the facial nerve to the corrugator supercilii muscle were investigated by dissection of 27 cadaveric hemifaces. Twelve cadaveric hemiforehead flaps were stained using a modified Sihler method to trace the supraorbital and supratrochlear branches. RESULTS: On average, 1.8 branches of the facial nerve at the zygomatic arch were associated with the corrugator supercilii muscle through 1 (29.3%) or 2 terminal rami (70.7%). The trigeminal nerve gave off 7.7 supraorbital and 5.1 supratrochlear branches emerging from orbit. The majority of the supraorbital branches became intramuscular branches (60.4%), whereas the majority of the supratrochlear branches became superficial branches (67.8%). CONCLUSION: Resection of the muscle may damage the intramuscular trigeminal branches, leading to sensory changes. The course of the facial nerve branches to the corrugator supercilii muscle was much more predictable at their distal part than the proximal part.