Distal lower motor neuron syndrome with high-titer serum IgM anti-GM1 antibodies : improvement following immunotherapy with monthly plasma exchange and intravenous cyclophosphamide

Motor neuropathies associated with electrodiagnostic evidence of motor conduction block often improve after treatment with immunotherapy, but there is less evidence about the responsiveness of lower motor neuron (LMN) syndromes without conduction block. In this study we treated four patients with an asymmetric, predominantly distal LMN syndrome associated with high serum titers of IgM anti-GM1 ganglioside antibodies but without conduction block on electrodiagnostic testing. Treatment courses consisted of five to seven repeated monthly regimens of plasma exchange on 2 consecutive days followed, on day 3, by intravenous cyclophosphamide (1 g/m2).