Motor neuron diseases and amyotrophic lateral sclerosis: GM1 antibodies and paraproteinemia.

Six of 110 patients (5.5%) with forms of motor neuron disease had abnormal titers of GM1 antibodies of 1:1,600 or higher. Four others came with previously known high titers. Three patients with upper motor neuron (UMN) signs had titers of 1,600; those with probable or no UMN signs had higher titers. Nine patients had conduction block; six of them had abnormal antibody titers, four with 6,400 or higher. Therefore, patients with motor neuron disease and abnormal anti-GM1 titers may have UMN signs or conduction block.