Is CMT1X primarily a demyelinating or axonal neuropathy?
According to criteria that were developed to distinguish the demyelinating (CMT1) from the axonal (CMT2) forms of CMT (Harding and Thomas, 1980), CMT1X is more like CMT2 than CMT1. Nerve conduction velocities are typically in 30-40 m/s in affected males and 30-50 m/s in affected females (Nicholson and Nash, 1993; Rouger et al., 1997; Birouk et al., 1998; Hahn et al., 1999; Senderek et al., 1999); this is faster than the 20 m/s typically seen in CMT1A patients (Birouk et al., 1997). In addition, electrophysiological studies pronounced loss of distal motor axons in CMT1X (Rozear et al., 1987; Hahn et al., 1990, 1999; Nicholson and Nash, 1993; Rouger et al., 1997; Birouk et al., 1998; Senderek et al., 1999). Finally, nerve biopsies show more axonal loss and less remyelination than is typically seen in CMT1A or CMT1B (Sander et al., 1998; Hahn et al., 2001). These data have lead to the frequent supposition that CMT1X is an axonal neuropathy (Hahn et al., 1990; Timmerman et al., 1996; Birou
