Anatomic observations of the carpal tunnel in cadavers with a report of unusual thickening of the perineurium of the median nerve

The carpal tunnel of 50 cadavers (100 hands) was dissected. Macroscopic finding included 14 median nerves with pressure signs (in 4 cadavers, unilaterally and 5 bilaterally). In three cadavers, marked synovitis was seen around the tendons and the nerve; in one, lipoma was evident; and in the rest, thickening of the volar carpal ligament was seen. Microscopic examination of the compressed nerves showed concentric thickening of the perineurium, thrombosis of veins, and intrafascicular fibrosis. In one nerve, the thickening of the perineurium was not concentric, but only at that part of the fascicle adjacent to the volar carpal ligament in an "onion peel" form.