A 35-Year-Old Man with Progressive Left-Hand Weakness

Multifocal motor neuropathy (MMN) may be mistaken for common entrapment neuropathies, although absence of significant sensory findings is a helpful clue to the diagnosis. Multifocal motor neuropathy may also mimic motor neuron disease. Electrophysiological evidence of conduction block at a nerve site not typically prone to compression is consistent with MMN. A positive anti-GM1 antibody also supports the diagnosis. First-line treatment of MMN is intravenous immunoglobulin (IVIG), and the majority of patients have rapid improvement of their weakness. The clinical features, differential diagnosis, investigations, and treatment options are described in this chapter.