Immunosuppressive treatment of motor neuron syndromes. Attempts to distinguish a treatable disorder.

OBJECTIVE: 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. DESIGN: Prospective, uncontrolled, treatment trial using prednisone for 4 months followed by intravenous cyclophosphamide (3 g/m2) continued orally for 6 months. SETTING: All patients were referred to university hospital medical centers. PATIENTS: 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. RESULTS: 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. CONCLUSIONS: 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.