Carpal tunnel syndrome occurs when the median nerve becomes compressed as it passes through the carpal tunnel, a narrow passageway in the wrist formed by the carpal bones and the transverse carpal ligament. On ultrasound, the key finding is an enlarged median nerve, typically measured by its cross-sectional area at the level of the pisiform bone, with an area greater than 10 to 12 square millimeters considered abnormal. Ultrasound can also visualize bowing of the flexor retinaculum, increased vascularity around the nerve, and any mass or fluid collection that may be compressing it. Musculoskeletal ultrasound has become an increasingly important tool for diagnosing carpal tunnel syndrome because it provides direct visualization of the nerve and surrounding structures without the discomfort of nerve conduction studies.
Sonography Term