Anatomic observations in carpal tunnel syndrome as they relate to the tethered median nerve stress test.

The Tethered Median Nerve Stress Test (TMNST) has proved to be a reliable clinical tool in the diagnosis of chronic, low-grade carpal tunnel syndrome (CTS). The TMNST consists of hyperextending the index finger at the distal interphalangeal joint with the wrist maintained in a supinated position. Proximal volar forearm pain radiation is experienced by patients with chronic CTS during this maneuver. This investigation shows that significant distal excursion of the median nerve occurs with hyperextension of the index finger and to a greater degree than with hyperextension of the adjacent digits. Pain experienced during the TMNST appears to be vascular in origin and its severity is directly related to the duration of testing. This finding emphasizes the important role of ischemia in chronic entrapment neuropathies.