Diagnosis and treatment of multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a unique disease mimicking motor neuron disease, but it is treatable with intravenous immunoglobulins. Anti-GM1 IgM antibody titers are not sensitive enough to predict the outcome. Electrodiagnosis is essential for the diagnosis of MMN. Conduction block has been suggested as the best diagnostic marker, but it is not found in all treatable cases. Activity-dependent conduction changes, as revealed by comparing conduction before and after maximal voluntary contraction of the muscle, are a convenient and promising tool. Treatment options include various immunosuppressants (including cyclophosphamide), but there has not been ample evidence in favor of any of these agents in randomized controlled trials. Intravenous immunoglobulins remain the mainstay for treating MMN.