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What is Multifocal motor neuropathy (MMN) or MMNCB

Multifocal motor neuropathy (MMN) or multifocal motor neuropathy with conduction block (MMNCB) is a rare neuropathy characterized by progressive, asymmetric muscle weakness and atrophy. Signs and symptoms include weakness in the hands and lower arms; cramping; involuntary contractions or twitching; and atrophy of affected muscles. MMN is thought to be due to an abnormal immune response, but the underlying cause is not clear. Most people treated with intravenous immune globulin (IVIG) have rapid improvement in weakness, but maintenance IVIG is usually required for sustained improvement. (source)

Multifocal motor neuropathy (MMN) causes damage to the nerves in the arms and legs. Nerve damage begins in adulthood and slowly gets worse over time. One side of the body may be more affected than the other. Symptoms of MMN may include weakness in the hands and lower arms; cramping; involuntary contractions or twitching; wrist drop or foot drop, and wasting of the affected muscles. MMN is thought to be due to an abnormal immune response, but the underlying cause is not clear. Diagnosis is based on the symptoms, clinical exam, and specific laboratory testing. Guidelines for diagnosis have been published. Treatment includes intravenous immune globulin (IVIG). Most people with MMN have rapid improvement in weakness with IVIG, but this treatment needs to be repeated regularly. Cyclophosphamide has also been effective in treating MMN. Physical and occupational therapy may be helpful for some people with MMN.[1][2][3][4]

Signs and symptoms of multifocal motor neuropathy (MMN) may include weakness; cramping; involuntary contractions or twitching; wrist drop or foot drop; and wasting (atrophy) of affected muscles.[5][6] Atrophy occurs late in the course of the condition.[1] Muscles of the hands and lower arms are most commonly affected, but muscles of the lower limbs may also be involved. The symptoms are often asymmetrical, meaning that they differ on the right and left side of the body.[5][7]

Multifocal motor neuropathy (MMN) is considered treatable with intravenous immune globulin (IVIG). Early treatment shortly after symptoms begin is recommended.[8] Most people have a fairly rapid improvement in weakness with IVIG, but the improvement generally does not last beyond a few months. Maintenance IVIG infusions are usually needed every two to six weeks. For those with severe disease whose symptoms don’t respond to IVIG (or for those who become resistant), treatment options are limited. Several reports have suggested that cyclophosphamide may be partially effective.[1]

This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
https://rarediseases.info.nih.gov/diseases/11011/multifocal-motor-neuropathy

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