A carpometacarpal joint ganglion cyst causing median neuropathy.

anglion cysts are common wrist masses and may cause median neuropathy. The great majority of volar wrist ganglia arise from the radioscaphoid or scaphotrapezial joint, with a smaller percentage originating from the pisotriquetral joint. 1,2 The car-pometacarpal joints are uncommon locations for ganglia, especially for cysts causing median nerve compression. A literature review of ganglia within the carpal tunnel syndrome found only two reports of carpometacarpal ganglia causing median neuropathy. 3,4 We describe carpal tunnel syndrome in a 29-year-old woman that was caused by a ganglion cyst arising from the second carpometacarpal joint. A 29-year-old right-hand–dominant nursing student and waitress presented with a 1-year history of progressive numbness and tingling in her right thumb and index and long fingers without history of trauma. During that month, she had noted a small mass in her palm. Conservative treatment measures including nonsteroidal anti-inflammatory drugs and splinting failed to provide any lasting relief. She reported significant nighttime pain and paresthesias, but review of systems was otherwise negative for fevers, chills, or other systemic symptoms. Her medical history was positive for migraine headaches. On physical examination, a soft mass measuring approximately 2.0 × 1.0-cm was palpable at the radial dis-tal aspect of the transverse carpal ligament. The overlying skin was normal. Two-point discrimination was 5 to 6 mm in all digits; intrinsic and thenar strength was 5 out of 5 without evidence of thenar atrophy. Radial pulse and digital capillary refill were normal. The findings of provocative maneuvers for cubital tunnel were equivocal, but Phalen's, Tinel's, and carpal tunnel compression maneuvers were strongly positive, causing dysesthesias into the radial 3 digits. Examination of the contralateral extremity yielded unremarkable findings. Plain radiographs showed no evidence of bony or liga-mentous abnormality. Magnetic resonance images demonstrated a 3.5 × 1.0 × 1.0-cm homogenous mass with low T 1 signal, increased signal on T 2-weighted short tau inversion recovery (STIR) images, and no significant enhancement (Figure 1). The collection of fluid appeared to arise at the second carpometacarpal joint and extend into the carpal tunnel, situated between the flexor pollicus longus and flexor digitorum tendons. The mass was dor-sal (deep) to the median nerve, displacing and deforming the nerve within the carpal tunnel. A presumptive diagnosis of ganglion cyst was made, and excisional biopsy was performed. DISCUSSION Ganglion cysts are an infrequent but well-recognized cause of carpal tunnel syndrome. Although median neu-ropathy at the carpal tunnel is much …