Miller Fisher syndrome is a regional variant of Guillain–Barré syndrome and characterized by cranial nerve involvement and the triad of ataxia, areflexia, and ophthalmoplegia. They are now believed to represent, along with a number of other entities, different clinical manifestations of a similar underlying autoimmune disorder, anti-GQ1b IgG antibody syndrome.
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Clinical presentation
Patients who develop Miller Fisher syndrome usually have a rapid onset of ataxia, areflexia, and 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.
Areflexia of the limbs only occasionally is associated with weakness 5.
Electrophysiological findings most commonly include reduced sensory nerve action potentials and absent H reflexes 7.
Pathology
Miller Fisher syndrome is considered to be a 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 present in most (~80-90%) of 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 nerves enhancement is reported, as it is with 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 is controversial 6.
History and etymology
It 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 IgG antibody-associated conditions.