Practical Electrophysiology for the Diagnosis of Multifocal Motor Neuropathy

Nerve conduction studies (NCS) are necessary to distinguish multifocal motor neuropathy (MMN) from other disorders with a similar clinical picture. In MMN, NCS may show a unique combination of conduction block (CB) or conduction slowing consistent with demyelination, whereas sensory conduction in the same nerve is normal. This contribution discusses a relatively simple and practical electrophysiological approach for the diagnosis of MMN that can be used by any neurologist who has had training in NCS. When diagnosing MMN, the most important practical points are: careful stimulation technique, investigation according to a standardised protocol that includes at least five nerves per arm with stimulation up to Erb’s point, understanding of and adherence to criteria for conduction block and demyelinative slowing and exclusion of nerves with marked axon loss.