Retrograde changes of nerve fibers with the carpal tunnel syndrome

Abstract

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.

Alteration of Proximal Conduction Velocity at Distal Nerve Injury in Carpal Tunnel Syndrome: Demyelinating Versus Axonal Change

“…The relationship between the severity of the lesion and the degree of RCS is less clear in humans than in animals. Someone have claimed that the degree of slowing in the forearm is not proportional to the severity of peripheral compression, whereas others have argued that its occurrence is specifically associated with severe compression, as in axonal injury (Buchthal et al, 1974;Joynt, 1989;Stoehr et al, 1978). Fox and Bangash (1996) first found substantial slowing in the median FMCV in the presence of minor abnormality in the carpal tunnel itself.…”

“…Occasionally, median forearm motor conduction velocity (FMCV) is also slowed (Buchthal et al, 1974;Chang et al, 2000Chang et al, , 2002bChang et al, , 2003Chang et al, , 2004Fox and Bangash, 1996;Kimura and Ayyar, 1985;Pease et al, 1990;Stevens, 1997;Stoehr et al, 1978;Thomas et al, 1967;Uchida and Sugioka, 1993). Our previous studies demonstrated that retrograde conduction slowing (RCS) does in fact occur in humans and that it is the primary cause of slowing of the median FMCV (Chang et al, 2000(Chang et al, , 2002b(Chang et al, , 2004.…”

“…However, those studies included CTS patients whose median FMCV were less than 50 m/s (Chang et al, 2000(Chang et al, , 2002b. Therefore, some authors argued that RCS occurs only in patients with CTS who have slowed median FMCV, lowamplitude compound muscle action potential (CMAP), or markedly decreased wrist-palm conduction velocities (Buchthal et al, 1974;Joynt, 1989;Stoehr et al, 1978). Recently, an experimental study in cats showed a 40% reduction in the conduction velocity of the proximal nerve in transected portions of nerves, along with a significant (7%) reduction in the remaining intact motor axons after partial transection of the motor nerve to the medial gastrocnemius (Havton et al, 2001).…”

The Real Role of Forearm Mixed Nerve Conduction Velocity in the Assessment of Proximal Forearm Conduction Slowing in Carpal Tunnel Syndrome

“…Occasionally, some patients also have a slowing of forearm median motor CV (Buchthal et al, 1974;Chang et al, 1993Chang et al, , 2000Chang et al, , 2002aChang et al, , 2003aChang et al, , 2004Chang et al, , 2008Melvin et al, 1973;Pease et al, 1990;Stoehr et al, 1978;Uchida and Sugioka, 1993;Thomas et al, 1967). This slowing is commonly ascribed to two possible mechanisms by electromyographers.…”

“…M edian wrist-palm conduction typically demonstrates a decreased conduction velocity (CV) or prolonged conduction time in patients with carpal tunnel syndrome (CTS) (Buchthal and Rosenfalck, 1971;Felsenthal and Spindler, 1979;Jackson and Clifford, 1989;Kimura, 1978Kimura, , 1979Mills, 1985;Stoehr et al, 1978). Occasionally, some patients also have a slowing of forearm median motor CV (Buchthal et al, 1974;Chang et al, 1993Chang et al, , 2000Chang et al, , 2002aChang et al, , 2003aChang et al, , 2004Chang et al, , 2008Melvin et al, 1973;Pease et al, 1990;Stoehr et al, 1978;Uchida and Sugioka, 1993;Thomas et al, 1967).…”