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.