Multifocal motor neuropathy

Abstract

Purpose of review: Multifocal motor neuropathy (MMN) has specific clinical and electrophysiologic features but can be difficult to diagnose if cases are not typical. Intravenous immunoglobulin (IVIg) remains the core initial and long-term treatment. In this review, recent advances in the diagnosis, monitoring and treatment of MMN are discussed.

Recent findings: The pathology of MMN likely depends on immune-mediated attack of the nodes of Ranvier and paranodal regions leading to conduction block. Antiganglioside antibodies are present in over 50% of patients. The sensitivity of antibody detection can be improved by testing for GM1/galactocerebroside (GM1/GalC) complexes. Complement activation plays a key role in the pathophysiology of MMN. Subcutaneous immunoglobulins are an efficacious alternative to IVIg for maintenance therapy in MMN. Complement inhibitor eculizumab may be a potential future treatment, but further studies are necessary.

Summary: The European Federation of Neurological Societies (EFNS)/Peripheral Nerve Society (PNS) guidelines for the diagnosis of MMN are currently widely used but probably need revision. Nerve ultrasound and plexus/nerve MRI can be helpful in diagnostic dilemmas. Monitoring of disease and response to treatment may improve using disease-specific evaluation scales such as MMN-Rasch-built overall disability scale. Further research into the pathophysiology of MMN is necessary to direct future treatment strategies.