Demyelinating symmetric motor polyneuropathy with high titers of anti-GM1 antibodies.

High titers of anti-GM1 ganglioside antibodies have been associated with multifocal motor neuropathy, a chronic asymmetric and exclusively motor disorder. We describe a patient with a progressive selective motor but symmetric polyneuropathy, followed over 5 years, with markedly elevated titers of anti-GM1 antibodies. The electrophysiological changes suggestive of motor demyelination were widespread, beyond conduction block alone, and involved contiguous nerve segments with complete sparing of sensory conduction. Progressive, predominantly motor, symmetric, demyelinating polyneuropathy may be an unusual relative of multifocal motor neuropathy, associated with anti-GM1 antibodies.