Not necessarily. When the myelin is damaged (CMT1) the nerve impulses are conducted more slowly than normal. If the axon itself is damaged (CMT2) the speed of nerve conduction is almost normal, but the strength of the signal is reduced. All forms of CMT are either demyelinating or axonal in nature. CMT is a multi-gene disorder and so there are many different defective genes which cause the disorder.

CMT affects the peripheral nervous system (PNS) and therefore it results in both motor symptoms (weakness and muscle wasting) and sensory symptoms (numbness). CMT is progressive and usually slowly.

Hope this helps.