To determine if response to immunosuppressive treatment in motor neuron syndromes could be predicted on the basis of clinical features, anti-GM1 antibodies, or conduction block.
Prospective, uncontrolled, treatment trial using prednisone for 4 months followed by intravenous cyclophosphamide (3 g/m2) continued orally for 6 months.
All patients were referred to university hospital medical centers.
Sixty-five patients with motor neuron syndromes were treated with prednisone; 11 patients had elevated GM1 antibody titers, and 11 patients had conduction block. Forty-five patients received cyclophosphamide, eight of whom had elevated GM1 antibodies and 10 had conduction block.
One patient responded to prednisone, and five patients responded to cyclophosphamide treatment. Only patients with a lower motor neuron syndrome and conduction block improved with either treatment. Response to treatment did not correlate with GM1 antibodies.
GM1 antibodies did not serve as a marker for improvement in patients with motor neuron syndrome treated with immunosuppressive drugs. Patients with amyotrophic lateral sclerosis failed to improve irrespective of laboratory findings.