Retrograde changes of nerve fibers with the carpal tunnel syndrome. An electroneurographic investigation.

In the CTS the motor nerve conduction velocity proximal to the wrist is reduced in proportion to the degree of severity of the nerve lesion. Furthermore the evoked nerve action potential is significantly reduced when recordings are made from the median nerve at the elbow and when the compound nerve is stimulated proximal to the lesion at the wrist. The extent of the retrograde changes correlates with the degree of severity and duration of nerve compression. Measurement of the evoked nerve action potential in the proximal nerve segment enables us to estimate the extent of the retrograde nerve fiber degeneration and therefore might be important for prognosis.