Miller-Fisher syndrome (MFS) is characterized by variable ophthalmoplegia, ataxia, and tendon areflexia. It seems to be a variant of Guillain-Barré syndrome (GBS), but unlike in GBS, there is a primitive involvement of the ocular motor nerves, and in some cases there is brainstem or cerebellum direct damage. The unusual case of MFS in the current study started with a bilateral areflexical mydriasis and a slight failure of accommodative-convergence. Ocular-movement abnormalities developed progressively with a palsy of the upward gaze and a bilateral internuclear ophthalmoplegia to a complete ophthalmoplegia. In the serum of this patient, high titers of an IgG anti-GQ1b ganglioside and IgG anti-cerebellum. anti-Purkinje cells in particular, were found. The former autoantibody has been connected to cases of MFS, of GBS with associated ophthalmoplegia, and with other acute ocular nerve palsies. The anti-cerebellum autoantibody could explain central nervous system involvement in MFS. The role of these findings and clinical implications in MFS and in other neuro-ophthalmologic diseases are discussed.