Neuro-ophthalmology and the Anti-GQ1b antibody syndromes.

The discovery of the association of the anti-GQ1b IgG antibody with the postinfectious clinical syndromes of ophthalmoplegia, ataxia, and areflexia helped house the phenotypes of the Miller Fisher syndrome (MFS), atypical MFS, Guillain-Barré syndrome with ophthalmoplegia, and Bickerstaff's brainstem encephalitis under one roof. The neuro-ophthalmologic signs classically predominate and may vary from case to case, but they maintain clinically recognizable patterns that assist with the diagnosis. The identification of a common lipopolysaccharide on the plasma membrane in human cranial and peripheral nerves at the GQ1b epitope and on infectious particles of bacteria and viruses (ie, Campylobacter jejuni) demonstrates molecular mimicry. The high frequency of oculomotor dysfunction is partially explained by the tissue ganglioside concentration and distribution and the attraction of antibody-stimulating complement activation. Current experimental treatment targets antibody removal and neutralization and prevents membrane attack complex formation through deactivation of complement. This article aims to bring together the historically disparate opinions on the origins of these syndromes as either a purely peripheral nervous system or central nervous system dysfunction, highlight the clinical neuro-ophthalmologic signs, discuss some of the biology of the anti-GQ1b antibody, and review imaging abnormalities and treatment of this fascinating disorder.