Vascular pathologic changes in the flexor tenosynovium (subsynovial connective tissue) in idiopathic carpal tunnel syndrome.

We used the Verhoeff-van Gieson stain method to identify histopathology and to localize elastin in the subsynovial connective tissue of the tendon sheath (SSCT) of the middle finger flexor digitorum superficialis (FDS) within the carpal tunnel in 10 carpal tunnel syndrome (CTS) patients and 10 control cadaver specimens. Normal SSCT stained for elastin abundantly around blood vessels and within vessel walls. The typical pathologic findings of CTS patients SSCT included vascular proliferation, vascular hypertrophy, and vascular obstruction with wall thickening. There was a decreased amount of elastin in the blood vessel walls and around the vessels in the CTS patients as well. The changes in the carpal tunnel patients were particularly remarkable in that the patients were younger than the controls, yet showed findings more characteristic of chronic degeneration.