Miller Fisher syndrome

Miller Fisher syndrome is an immune-mediated condition characterized by the triad of cerebellar ataxia, areflexia, and external ophthalmoplegia. It is believed to represent, along with several other entities, different clinical manifestations of a similar underlying autoimmune disorder, the anti-GQ1b antibody syndrome. 

Clinical presentation

There is a rapid onset of cerebellar ataxia, areflexia, and external ophthalmoplegia, which usually follows a viral illness in the preceding 5-10 days ^1,5. Ophthalmoplegia (initially upgaze, then lateral gaze and then downgaze) and ataxia usually precede areflexia ⁵. Weakness is usually absent ⁵. 

Electrophysiological findings commonly include reduced sensory nerve action potentials and absent H reflexes ⁷. 

Pathology

Miller Fisher syndrome is considered to be an immune-mediated peripheral neuropathy. However, involvement of the central nervous system has also been reported (somewhat controversially), including lesions within the posterior columns of the spinal cord and in the brainstem 1,4. Anti-GQ1b antibodies are pathogenic and present in most (~85%) cases ^6,7.

Radiographic features

MRI

Although MRI is usually used to investigate patients with these symptoms, there can be no abnormalities ⁷. Multiple cranial nerve enhancement is reported, similar to Guillain-Barré syndrome ⁸.

Treatment and prognosis

Although most cases of Miller Fisher syndrome have a good prognosis, occasional cases with permanent neurological disability are encountered. Fatal progression has also been described but is uncommon (<5%) ^1,7.

Generally, recovery begins a few weeks after symptom onset and is usually complete by 6 months ⁵.  

Treatment with immunomodulatory therapies, such as intravenous immunoglobulin, is controversial, but usually employed ⁶. 

History and etymology

This syndrome is named after Charles Miller Fisher (1913-2012) a renowned Canadian neurologist, who first described the condition in 1956 ^2,3,9.

Differential diagnosis

Clinically the differential includes primarily the other anti-GQ1b antibody syndromes and Guillain-Barré syndrome variants.