Anti-GQ1b IgG antibody is associated with ataxia as well as ophthalmoplegia

Close association between the increase in anti-GQ1b immunoglobulin G (IgG) antibody and ophthalmoplegia in Miller Fisher syndrome (MFS) and Guillain-Barré syndrome (GBS) has been reported. We investigated whether anti-GQ1b IgG antibody also is associated with ataxia, another of the MFS triad. Of 149 patients who had anti-GQ1b IgG antibody without profound weakness, 144 showed ophthalmoplegia (120 showed both ophthalmoplegia and ataxia; 24, ophthalmoplegia without ataxia). In contrast, five showed ataxia without ophthalmoplegia. Some large neurons of the dorsal root ganglia were immunostained with anti-GQ1b monoclonal antibody. Anti-GQ1b IgG antibody may thus be associated with ataxia as well as ophthalmoplegia. Ataxia may be due to its binding to a subset of primary sensory neurons.