Aberrant Innervation of the Pectoralis Major Flap Resulting in Myospasm.

The pectoralis major flap is a reliable option in head, neck, and chest wall reconstruction; however, postoperative myospasm is a source of significant morbidity. The pathophysiological mechanism remains unclear, with proposed causes including incomplete nerve division or anatomical variation. We present 2 cases of patients who developed symptomatic myospasm following pectoralis major flap reconstruction, despite division of the medial and lateral pectoral nerves during the primary procedure. In both cases, aberrant motor nerves were identified intraoperatively running alongside the thoracoacromial pedicle. Stimulation of these nerves reproduced patient symptoms, and targeted neurectomy led to symptom resolution or significant improvement. These findings suggested that alternative motor innervation may underlie persistent myospasm in some patients. This was the first report to document the direct intraoperative identification and treatment of aberrant innervation as a contributing factor. Further anatomical studies are warranted to explore the prevalence, origin, and clinical significance of this variation.