Fulminant multifocal motor neuropathy: a report of two cases

Multifocal motor neuropathy (MMN) shows stepwise progression over decades. The multifocal weakness usually remains asymmetric, confined to distal limb muscles, while sparing cranial, phrenic, and sensory nerves. One electrophysiological hallmark is partial motor conduction block (CB) at sites not exposed to compression; whether CB is an essential feature remains debatable. High titer of anti-GM1 antibodies is found with figures usually between 40% and 50% of patients. Intravenous immuneglobulin (IVIg) is effective in almost 80%, but plasmapheresis and steroids are not. The condition is reported as lethal exceptionally, mimicking motor neuron diseases (MND). We have studied two patients who failed to respond to treatment and who died with respiratory failure; one of the two had high titer of IgM antibody to the ganglioside GM1. Our cases confirm that great attention should be paid in order to define the borderland between MMN and MND and the entity of their clinical and electrophysiological overlaps.