Demyelinating symmetric motor polyneuropathy with high anti-GM1 antibody titer: do we need to split?

摘要

Multifocal motor neuropathy (MMN) is characterized by stepwise or progressive muscle weakness with wasting and fasciculations. Characteristic features include a finding indicative of demyelination, motor conduction block (CB) outside of sites of nerve compression. Although CB remains the hallmark of MMN, it was not considered essential for diagnosis. O'Ferrall et al. reported a patient with progressive motor demyelinating neuropathy associated with elevated titers of antibodies against the ganglio-side GM1. The patient had mostly distal weakness and normal sensory examination; over 5 years, his disorder remained symmetric and confined to the motor system. Treatment with intravenous immunoglobulins (IVIg), oral prednisone, methylprednisolone, and cyclophospha-mide had questionable benefit. The patient6 had demyelinating features in the motor nerves, including prolonged distal latencies, conduction slowing, prominent temporal dispersion, and CBs. The investigators concluded that the extent of findings was far beyond those expected from reported series of MMN patients. The electrophysiolog-ical abnormalities spared the sensory fibers, which demonstrated selectivity of this condition for motor axons and differentiated it from chronic inflammatory demyelinating polyneuropathy (CIDP). The patient's serum contained elevated titers of IgM antibodies to GM1.