Miller Fisher syndrome is a variant of Guillain-Barré syndrome, characterized by 
ophthalmoplegia, ataxia and areflexia. The antiGQ1b immunoglobulin G antibody is 
a specific marker of Miller Fisher syndrome and related disorders, such as 
Guillain-Barré syndrome with ophthalmoplegia, atypical Miller Fisher syndrome 
characterized by acute ophthalmoplegia or acute ataxia and Bickerstaff's 
brainstem encephalitis. The antiGQ1b immunoglobulin G antibody may play some 
important roles in the pathogenesis of Miller Fisher syndrome and related 
disorders. Possible mechanisms are discussed. Molecular mimicry between an 
infectious agent of the antecedent infection and the ganglioside may be a 
mechanism of the antibody production. Plasmapheresis or intravenous 
immunoglobulin therapy may be warranted for Miller Fisher syndrome and 
Bickerstaff's brainstem encephalitis, as well as Guillain-Barré syndrome with 
ophthalmoplegia.