Optimizing Botulinum Toxin Injections in the Platysma Muscle Based on Motor Nerve Distribution

Abstract

Background: Platysmal bands contribute to neck ageing and lower-face descent. Although botulinum toxin A (BoNT-A) is approved for this indication, conventional whole-muscle dosing requires many superficial injections with attendant risks. Objective: To develop an anatomically guided protocol that targets motor-dense zones of the platysma, optimizing efficacy while reducing dose and complications. Methods: Sihler-stained dissections mapped motor versus sensory innervation. Ultrasound-guided injections were performed in 40 patients, delivering 30-60 U BoNT-A per side at 15 sites concentrated in the upper two-thirds of the platysma and along the marginal mandibular border. Outcomes included band severity, jawline definition, adverse events, and cost. Results: Motor end-plates clustered in the upper platysma; the lower third was largely sensory. Targeted injections produced a >= 2-grade reduction in dynamic bands in 92.5% of patients by week 4, maintained through week 12. Mean toxin use fell 35% versus historical whole-muscle protocols; bruising dropped to 5%, with no dysphagia or lower-face weakness. Treatment costs were proportionally lower. Conclusions: Concentrating BoNT-A in the motor-rich upper platysma under ultrasound guidance maximizes aesthetic improvements while minimizing dose, discomfort and adverse events. This neural distribution-based algorithm offers a safer, more economical alternative to conventional platysmal band treatment.