Hereditary Motor and Sensory Neuropathies (HMSNs) With Conduction Block.

Dysmyelinating forms of hereditary motor and sensory neuropathy (HMSN) typically exhibit uniform conduction slowing on electrophysiological studies. However, this has been challenged in the past few decades with the discovery of novel gene mutations that induce nonuniform conduction slowing resembling acquired demyelinating neuropathies. Conduction block (CB) and/or excessive temporal dispersion (TD) are characteristic of segmental changes. Nevertheless, there is no consistent definition for CB and TD in inherited neuropathies. Pathological changes at paranodal regions or segmental demyelination might be explanatory in some patients.