Presentation
Left thumb painful movements for the last few weeks. No trauma. An incidental ultrasound finding is present on the left side.
Patient Data
A short-axis image just proximal to the left carpal tunnel shows muscle echopattern at the palmaris longus tendon location. Palmaris longus tracing shows its muscle belly in the mid-distal forearm and tendon in the proximal forearm.
Right palmaris longus was traced for a comparison. Its muscle belly is located proximally and tendon in the distal forearm.
At the site of pain pointed by the patient (radial styloid process region), the retinaculum involving the 1st extensor compartment is thickened. There is a common synovial sheath of abductor pollicis longus and extensor pollicis brevis up to the distal end radius level. There is anechoic effusion in the abductor pollicis longus tendon sheath.
The asymptomatic right side also shows features of De Quervain tenosynovitis similar to the left side.
Case Discussion
The case shows the incidental finding of a reversed palmaris longus in the left forearm and bilateral De Quervain tenosynovitis. The most common variation of the palmaris longus is an absent muscle1. Other variations are reversed, duplicated, bifid, or hypertrophied palmaris longus muscles1.