Miller-Fisher Syndrome

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Miller-Fisher Syndrome
Gareth J. Parry
In 1956, Dr. C. Miller Fisher described a syndrome of ataxia, areflexia and ophthalmoplegia and suggested that it was a variant of Guillain-Barre syndrome (GBS). Ophthalmoplegia, or weakness of the muscles around the eyes, causes double vision (diplopia) and droopy eyelids (ptosis); the reaction of the pupil to light stimulation may also be affected. Loss of coordination and balance (ataxia) mainly affects walking but there may also be clumsiness of the arms. The combination of diplopia and ataxia makes walking particularly hazardous and falls are a substantial risk. When the patient is examined there is loss of the reflexes (areflexia) when the tendons at the ankles and knees and in the arms are tapped. Other cranial nerves may also be involved causing facial weakness, difficulty swallowing and slurred speech but these effects are usually mild. There may also be mild weakness of limb muscles. Some patients may progress from an initial pure MFS to a more generalised GBS, even including respiratory failure, but this is very uncommon. Nonetheless, patients with MFS should be admitted to the hospital for observation to ensure that the effects remain restricted to the cranial area. As in typical GBS, the symptoms often come on a week or two after some kind of infectious illness. The disease progresses usually for 1-2 weeks but occasionally for as long as 4 weeks, then stabilises and steadily improves. Prognosis for full recovery is excellent with most patients being back to normal within 2-3 months although a few have mild residual ataxia for longer; diplopia and ptosis almost always completely resolve.
There is no consensus concerning the treatment for MFS, mainly because there have been no carefully controlled therapeutic trials. The most important treatment is supportive. Patients should ambulate with care to avoid falls. An eye patch will eliminate diplopia which can be very distressing. Regular testing of bulbar functions (speech and swallowing) should be made to detect and appropriately manage any swallowing difficulty. Most of the immunological treatments that have been shown to benefit standard GBS have also been tried in MFS and many anecdotes in the literature attest to their benefit. Because most cases have only mild disability, improve rapidly without immunological treatment and fully recover, I generally do not recommend treatment unless there is ataxia of sufficient severity to interfere with safe ambulation. If treatment is used I recommend intravenous gammaglobulin (Intragam) rather than plasmapheresis as it is better tolerated and easier to administer.
Most cases of GBS result from antibodies attacking the myelin sheath of peripheral nerves; occasionally the axon is the primary target. Recent research has shown that MFS is very strongly associated with antibodies to a component of myelin called GQ1b. Over 90% of patients with MFS have these antibodies. In most countries, MFS makes up about 5% of cases of GBS but in Japan it is about 25%. The figure for New Zealand is unknown but it has been my impression over the last 2 years that MFS is more common here than in North America but it certainly is not as common as in Japan. The unusually high incidence of MFS in Japan and perhaps in New Zealand suggests that some populations are genetically more likely to develop GQ1b antibodies in response to a bacterial or viral infection.
In summary, MFS is a relatively benign variant of GBS that has a highly characteristic clinical appearance that is easily recognised. Like typical GBS, the disorder is self-limited and almost never recurs. Prognosis is excellent and specific immuno-therapy is seldom necessary.

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