The node of Ranvier in multifocal motor neuropathy.

Multifocal motor neuropathy affects myelinated motor axons in limb nerves at multifocal sites. It is characterized by weakness and muscle atrophy, motor conduction block, and antibodies against ganglioside GM1 which is expressed on the axolemma of nodes of Ranvier and perinodal Schwann cells. Treatment by regular IVIg courses results in temporary improvement but cannot prevent slowly progressing weakness due to axonal degeneration. This review discusses possible mechanisms of conduction block and the reasons why motor axons are selectively affected in this disorder.