Idiopathic Isolated Flexor Pollicis Longus Denervation (Incomplete Kiloh-Nevin Syndrome)—A Rare Presentation Managed by Tendon Transfer

Abstract

This case report describes a rare presentation of isolated denervation of the Flexor Pollicis Longus (FPL), known as incomplete Kiloh-Nevin syndrome. The FPL, responsible for thumb flexion, is innervated by a motor branch of the anterior interosseous nerve (AIN), a branch of the median nerve. A 19-year-old female presented with sudden difficulty in holding a pen, and electromyographic findings revealed complete denervation of the FPL. Tendon transfer from the flexor digitorum superficialis to the FPL was performed, followed by physiotherapy. Postoperatively, full active flexion was achieved at the thumb’s distal interphalangeal joint. The discussion explores AIN dysfunction causes, diagnostic considerations, and treatment options, emphasizing the importance of surgical intervention when paralysis persists. This case highlights the significance of recognizing and addressing uncommon neuromuscular conditions for effective management