Masseter Hypertrophy: Toxin Treatment Techniques, Causes of Complications, and Prevention

Botulinum neurotoxin (BoNT) injection for the correction of masseter muscle hypertrophy is an off-label but increasingly popular procedure, especially in Asians where masseter hypertrophy is a common facial feature. This chapter outlines and organizes the various possible complications of such a procedure and discusses their incidence rates, etiological explanations, and prevention methods. Complications were separated into four main categories: nonmuscular-related, neurotoxin-related, dosage- or injection-level-related, and injection-site-related categories. The ideal dosage and injection location are also described and discussed, with particular emphasis on the injection safe zone, where all injections to the masseter should be made in order to minimize complications and maxi- mize safety.