For demyelinating types, the characteristic findings are diffusely and equally decreased conduction velocities. In every nerve tested, both sensory and motor, roughly the same degree of marked slowing is found. Such slowing can also be found in asymptomatic individuals, and for this reason family members, even those who do not complain of weakness, are often tested to aid in the diagnosis. Nerve Biopsy Nerve biopsy is usually not necessary for diagnosis, especially since the availability of genetic testing. It is still helpful, however, for diagnostic dillemmas.
Findings depend upon the type.
Type 1 reveals demyelination and multiple layers of remyelination, called onion bulbing. Type 2 reveals axon loss with wallerian degeneration. Type 3 reveals demyelination with thinning of the myelin sheath. As important as what the biopsy shows, is what the biopsy should not show. There should be no inflammatory infiltrate indicating an autoimmune demyelinating process.