A 34-year-old woman developed weakness and sensory loss in her left hand following laceration injury of her left anterior forearm 2 years earlier. A cyst subsequently evolved over the area of the injury. Results from an examination confirmed her thenar weakness and median distribution sensory loss. The cyst was located 5 cm proximal to the distal wrist crease and was 1.5 cm × 1.5 cm in area, tender to palpation, and immobile. Tapping it yielded a Tinel sign. Median motor conduction velocity was slowed across the cyst (29 m/s), and distal response amplitude was decreased (1 mV) in the abductor pollicis brevis muscle.
Hobson-Webb LD, Walker FO. Traumatic Neuroma Diagnosed by Ultrasonography. Arch Neurol. 2004;61(8):1322-1323. doi:10.1001/archneur.61.8.1322