Pneumothorax Following Botulinum Neurotoxin Injection for Trapezius Hypertrophy

Botulinum neurotoxin (BoNT) injection into the trapezius muscle is increasingly performed for aesthetic contouring. However, iatrogenic pneumothorax has not been previously documented for this cosmetic indication, despite the inherent anatomical risks. We report a 26-year-old woman who developed immediate severe radiating pain during bilateral trapezius BoNT type A (BoNT-A) injections using a 4.8-cm, 25-gauge needle. During the injection, the patient experienced immediate severe radiating pain, followed by pleuritic chest pain and dyspnea within 30 minutes. Computed tomography confirmed a 30% left pneumothorax, effectively ruling out systemic botulism. Subsequent ultrasound revealed a skin-to-pleura distance of only 2.27 cm at the injection site, highlighting the stark mismatch with the 4.8-cm needle used. The patient was managed conservatively with high-flow oxygen, achieving complete clinical and radiographic resolution within 1 month. This case underscores that pneumothorax is a real risk with blind injection techniques and overly long needles. To minimize harm, practitioners should adhere to anatomically defined safe zones, select conservative needle lengths, and utilize ultrasound assistance when necessary, particularly for thin patients.