Fisher syndrome.

OPINION STATEMENT: Fisher syndrome is characterized by the clinical triad of ophthalmoplegia, ataxia, and areflexia. It is considered a variant form of Guillain-Barré syndrome, which is associated with anti-GQ1b antibodies. During initial examinations of patients, physicians must rule out other neurologic disorders or conditions that resemble Fisher syndrome, such as vitamin B1 deficiency (Wernicke's encephalopathy), vascular disease, multiple sclerosis, collagen disease, Behçet disease, sarcoidosis, neoplasm of the brainstem, and infectious diseases such as diphtheria, botulism, and viral infections (eg, herpes encephalitis). The acute phase of Fisher syndrome should be carefully observed to see if it occurs concomitantly with Guillain-Barré syndrome or if there is development to Bickerstaff brainstem encephalitis, as these require specific immune treatments. Typically, Fisher syndrome has a fairly good natural course. Although several reports have suggested the possible efficacy of immunotherapies such as plasmapheresis and intravenous immunoglobulins (IVIg) in treating Fisher syndrome, there have been no randomized controlled studies. Large retrospective studies have suggested that neither plasmapheresis nor IVIg alters the clinical outcome of patients with Fisher syndrome, probably because of the good spontaneous recovery in these patients. Therefore, Fisher syndrome alone does not necessarily require immunotherapy. To accelerate the start of recovery, IVIg can be given, but it is important to first obtain informed consent from patients after the potential risks of blood products are explained. When overlap with Guillain-Barré syndrome or development to Bickerstaff brainstem encephalitis occurs, plasma exchange or IVIg should be administered as early as possible because Guillain-Barré syndrome can cause respiratory failure or severe weakness with axonal degeneration, and Bickerstaff brainstem encephalitis may not have as good a natural course as Fisher syndrome alone. There have been no prospective, controlled studies (randomized or nonrandomized) of the use of immunotherapy to treat Fisher syndrome. To evaluate the efficacy of immunotherapies used to treat Fisher syndrome, large prospective studies are required.