“…The first is a conduction block of the fastest myelinating fibers in the carpal tunnel, measuring only the CV of the slower axons (Chang et al, 1993;Melvin et al, 1973;Stevens, 1997;Thomas and Fullerton, 1963;Wilson, 1998). The other presumed mechanism is retrograde axonal atrophy or retrograde conduction slowing (RCS), which may result in an increase in electrical resistance and a decrease in CV (Anderson et al, 1970;Chang et al, 2000Chang et al, , 2002aChang et al, , 2003aChang et al, , 2004Chang et al, , 2008Dyck et al, 1981;Devor and Govrin-Lippmarn, 1986). A direct measurement of the forearm (wrist-elbow) median mixed nerve CV (forearm-mix CV), with recording at the elbow and stimulation at the wrist, may reflect the real CV over the forearm and pinpoint the actual mechanism (Chang et al, 1993;Pease et al, 1990;Uchida and Sugioka, 1993;Wilson, 1998).…”