Ultrasonographic and Three-Dimensional Analyses at the Glabella and Radix of the Nose for Botulinum Neurotoxin Injection Procedures into the Procerus Muscle

Botulinum neurotoxin (BoNT) injections are widely used for facial rejuvenation procedures, and the procerus muscle is a major target in cases of glabellar transverse lines or rhytids. Although there have been many cadaveric studies of the procerus, its depth and thickness have not been investigated thoroughly. The aim of this study was to measure the depth and thickness of the procerus and identify the location of the intercanthal vein using ultrasonographic (US) imaging and the three-dimensional scanning method, which is needed to know to avoid side effects during BoNT injections. The morphology of the procerus was classified into two types based on the US images obtained at the glabella. The procerus was located deeper below the skin surface at the glabella than the sellion (3.8 +/- 0.7 mm versus 2.7 +/- 0.6 mm). The width of the procerus in US images increased from the sellion (10.9 +/- 0.2 mm) to the glabella (14.5 +/- 4.6 mm), whereas its thickness decreased (from 1.6 +/- 0.6 mm to 1.1 +/- 0.5 mm). The intercanthal vein was located 5.1 +/- 4.0 mm superior to the sellion and 3.0 +/- 0.6 mm below the skin's surface. The present findings provide anatomical knowledge as well as the reference location information for use when injecting BoNT into the procerus.