A Case of Trigger Wrist Presenting with Median Nerve Irritation Symptoms Due to a Tumor

Trigger wrist is a rare disorder characterized by triggering at the wrist caused by finger, wrist, or forearm motion. We report a case of trigger wrist with symptoms of median nerve irritation due to a tumor.

[Case] A 41-year-old male presented with pain and numbness from the left thumb to the ring finger, accompanied by clicking at the wrist joint during flexion of the left finger. Physical examination revealed a palpable click over the volar wrist with active finger flexion and a positive Tinel sign. Nerve conduction velocity test (NCV) was normal. MRI revealed a 9×4×15-mm hypointense T1 and hyperintense T2 mass between the proximal palmar aspect of the third metacarpal and the flexor tendon. Sonography demonstrated that the mass moved with finger flexion and extension, and flattening of the median nerve was observed during triggering.

The diagnosis was trigger wrist caused by the mass, and the operation for its resection was performed under median nerve block. After releasing the flexor retinaculum, the mass attached to the dorsal surface of the flexor digitorum superficialis of the index finger was excised, and the popping phenomenon during active motion disappeared. The pathological diagnosis of the mass was a giant cell tumor of the tendon sheath. The patient had no limitation of wrist joint range of motion at 6 months postoperatively.

[Discussion] Previous literature has reported that more than half of patients with trigger wrist have carpal tunnel syndrome. However, NCV findings in previous reports have varied, with some lacking detailed mention of the NCV. In the present case, the nerve motor velocity test was normal. Intermittent compression of the median nerve was considered the cause, as flattening of the median nerve was observed on ultrasound only during triggering.

Keywords: Trigger wrist, Carpal tunnel syndrome, Nerve conduction velocity