[Multifocal motor neuropathy with persistent conduction blocks. A chronic immune-mediated neuropathy].

Multifocal motor neuropathy with persistent conduction blocks was first specifically identified in 1986. Its major criterion is conduction blocks in motor nerves only. Clinically, this is a multifocal, thus asymmetric, neuropathy that begins and predominant touches upper limbs; it especially affects men after the age of 50 years and has a chronic course with relapses. Approximately 40-50% of patients also have IgM serum antibodies directed against GM1 ganglioside. There are no other laboratory criteria, although moderately high protein levels are found in cerebrospinal fluid. Its course is unpredictable, because the neuropathy may remain limited to one or two motor nerves or extend progressively to all the motor nerves of all four limbs. In general, there is no damage to sensory or cranial nerves or to the autonomic or central nervous systems. Intravenous polyvalent immunoglobulins at high doses are remarkably effective in the short term in 70 to 80% of cases. Corticosteroids and plasma exchange are generally ineffective and may aggravate the neuropathy. The long-term efficacy of intravenous immunoglobulins in delaying motor decline and axon loss in the affected motor nerves is controversial. No information is currently available about the long-term efficacy of other immunomodulatory treatment.