Anomalous Functional Lumbrical Muscle Causing Carpal Tunnel Syndrome: A Case Report

Anatomical variations within the carhpal tunnel can contribute to compression of the median nerve. This can include abnormal flexor digitorum superficialis or palmaris profundus muscle bellies underneath the transverse carpal ligament. We report a rare case of an accessory lumbrical muscle found within the carpal tunnel in a patient with clinical carpal tunnel syndrome (CTS). This was found to be a functional lumbrical muscle to the middle finger. On division of the transverse carpal ligament without resection of this muscle, the patient had clinical resolution of their symptoms. This case is the first to show high-quality images of these lumbrical muscles actively functioning in a patient with carpal tunnel syndrome. This highlights the importance of considering anatomical variations in patients with CTS. Careful intraoperative inspection is essential to identify and address these anomalies, ensuring resolution of symptoms, without impairing function.