Since identification of the autoantibodies in Fisher syndrome, remarkable progress has been made in our understanding of that syndrome and related conditions. Because of the similarities in the clinical presentations of it and Bickerstaff brainstem encephalitis, opinions differ as to whether the two are distinct or related syndromes and whether the lesions responsible for ophthalmoplegia, ataxia and areflexia are in the peripheral or central nervous system. The finding that both conditions have autoantibodies in common suggested that the autoimmune mechanism is the same in both and they are not distinct conditions. Common autoantibodies, antecedent infections, and neuroimaging and neurophysiological results from a large study offer conclusive evidence that these conditions form a continuous spectrum with variable central and peripheral nervous system involvement. A new eponymic terminology "Fisher-Bickerstaff syndrome" may be helpful for nosology. A considerable number of patients with Bickerstaff brainstem encephalitis have associated Guillain-Barré syndrome, indicative that these two disorders are closely related on a continuous spectrum. That finding is further evidence of continuity between Bickerstaff brainstem encephalitis and Fisher syndrome, a variant of Guillain-Barré syndrome.