Pathophysiology of conduction block in multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is a rare disorder of the peripheral nervous system characterised by the presence of focal motor conduction blocks. Although the pathological basis of conduction block is believed to be focal demyelination, in multifocal motor neuropathy this mechanism lacks definitive proof from morphological studies. In recent years special neurophysiological techniques for assessing axonal excitability non-invasively in humans have expanded knowledge on the pathophysiology of multifocal motor neuropathy. Nonetheless, several findings support the hypothesis that conduction blocks probably arise from more than one pathogenetic mechanism (hyperpolarisation or depolarisation) which can change during the course of the disease and probably represent the “tip of the iceberg” of axo-myelinic abnormalities.