MR DEMONSTRATION OF AN ANOMALOUS MUSCLE IN A PATIENT WITH COEXISTENT CARPAL AND ULNAR TUNNEL-SYNDROME CASE-REPORT AND LITERATURE SUMMARY

An aberrant muscle is demonstrated by magnetic resonance (MR) imaging in a patient presenting with focal wrist swelling and compression neur opathy of median and ulnar nerves following 4 months of carpentry work . The muscle originated from the palmaris longus tendon and ulnar ante brachial fascia at the lower half of the forearm as a single belly, th en diverged medially from palmaris longus tendon and bifurcated. Both portions of the split muscle extended into the distal ulnar tunnel or Guyon's canal. One segment joined with the abductor digiti minimi musc le and the other with the flexor retinaculum. MR was able to clearly d elineate this hypertrophied, symptomatic muscle anomaly. It may be hel pful when mass effect is suspected in either tunnel, or in patients wi th atypical work-related carpal tunnel syndrome with evidence of signi ficant ulnar neuropathy for evaluation of underlying anomalous muscula ture. Normal MR images of the wrist are included for comparison and th e literature is reviewed.