Acute oculomotor impairment with anti-GQ1b IgG due to central nervous system dysfunction

We report the case of a patient with isolated central oculomotor impairment and anti-GQ1b antibody. The patient was referred to us with acute vertical diplopia. The neurological examination revealed right internuclear ophthalmoplegia (INO), skew deviation and mild gait ataxia. Extensive laboratory analyses, CSF study, multimodal evoked potentials and brain MRI were normal. Eye movement recording showed saccade dysmetria in addition to the INO. The subjective visual vertical was abnormally tilted to the left. The anti-GQ1b IgG antibody was detectable on serum DOT-BLOT. The brainstem and cerebellar features of the oculomotor impairment suggested that in our patient the anti-GQ1b IgG antibody showed a preferential cross-reaction with central nervous system epitopes. This finding is at variance with previous reports on anti-GQ1b syndrome with acute ophthalmoplegia, all of which argue for a localization of GQ1b epitopes within the peripheral nervous system, even though, in the light of the description of the ocular motor disorder, a central involvement might have co-occurred in this case.