Ultrasonographic study and anatomical guidelines for botulinum neurotoxin injection into the parotid gland

Benign enlargement of the parotid gland hypertrophy results in a bulky lateral facial contour and esthetic appearance. This study aimed to determine the depth from the skin surface to the parotid fascia, which encompasses the parotid gland. The anatomical properties of the parotid glands were evaluated in 40 patients using ultrasonography. An up-to-date understanding of the localization of botulinum neurotoxin (BoNT) injection based on anatomy could lead to better localization of the injection into the parotid gland through morphological measurements using data previously published from cadaveric studies. Measurement using the otobasion inferius as a landmark revealed parotideomasseteric fascia thickness averaging 4-6 mm from the skin surface, with the parotid gland extending approximately 15 mm anteriorly. Analysis showed a 3-7 mm thickness range, indicating an optimal injection depth for safety and efficacy in BoNT procedures. Utilizing the otobasion inferius as an anatomical landmark offers a practical approach for measuring parotideomasseteric fascia thickness, addressing cadaveric study limitations. These guidelines aim to maximize the effects of BoNT therapy, which can be useful in clinical settings, by minimizing its deleterious effects.