Multifocal motor neuropathy

Multifocal motor neuropathy, abbreviated MMN, is a progressively worsening condition in which muscles of the arms and legs gradually weaken. It is a pure motor neuropathy syndrome and is thought to be autoimmune. Because the clinical picture resembles amyotrophic lateral sclerosis, especially when muscle twitching is present, it is sometimes mistaken for that disease; unlike ALS, MMN involves only the lower motor neuron pathway, meaning the peripheral nerves that arise from those neurons. Diagnosis is often hard and can take months or years. Pain is usually slight, the condition is not fatal and does not shorten life, but it can cause real disability such as loss of hand function and foot drop. The source says it was first described in the mid-1980s.