Comprehensive Glabellar Anatomy for the Cosmetic Surgeon

Introduction: The purpose of this study was to clarify controversies in motor innervation to the glabellar muscles in order to create a comprehensive guide of anatomic relationships within the glabella for the cosmetic surgeon performing surgery or injections in this aesthetic region. Methods: Microdissection was performed on 28 sides of 14 preserved cadaver heads and 10 sides of 5 fresh-frozen cadaver heads. Dissection proceeded anterograde from the main trunk of the facial nerve to its terminal branches in the glabellar muscles. Measurements were made with calipers to record the locations of the motor nerve entry into the corresponding muscle and the locations of the sensory nerves, vessels, and orbital landmarks. Results: The temporal branch of the facial nerve did not terminate after supplying the posterolateral transverse corrugator muscle but continued medially to innervate the oblique head of the corrugator muscle, entering 4 mm inferior to the superior edge (range 2–6.5 mm). This pattern was identified in 26 of 38 dissections (68.4%). In 74% of specimens, a small artery coursed with the nerve toward the corrugator muscle that should be anticipated to avoid bleeding. In 4 specimens (10.5%), the temporal facial nerve supplied a branch to the depressor supercilii, which continued to enter the posterior surface of the procerus muscle. In the remaining specimens, the small terminal branches were lost after entering the oblique corrugator muscle. The supratrochlear nerve exited between, rather than lateral to, the 2 heads of the corrugator supercilii muscle near the muscle origin before dividing into 2–3 branches and measured 17 mm from midline. A sensory branch entered the procerus muscle 5 mm inferior to the motor nerve entering the muscle. The supraorbital notch and foramen was 26 mm from midline. Prominent angular vessels were located between the heads of the corrugator supercilii muscle and between the heads of the depressor supercilii muscle. Conclusions: With a thorough understanding of the anatomic relationships of the muscles to their associated innervation and vascular supply, complications such as prolonged paresthesia or dysesthesia from sensory nerve injury, eyebrow asymmetry from motor nerve damage, traumatic neuromas, and visual loss from vascular emboli from cosmetic injections may be avoided.