Miller Fisher Syndrome or, 'MFS,' is a post-infectious, immune mediated neuropathy characterized in typical instances by the clinical triad of ataxia, areflexia and ophthalmoplegia. MFS is considered to be a variant of Guillain-Barre syndrome or, 'GBS.' The clinical symptoms usually develop within days and improve spontaneously or following treatment within a period of weeks. People with MFS often show only part of the clinical triad.
Miller Fisher syndrome is a rare, acquired nerve disease that is considered to be a variant of Guillain-Barré syndrome. It is characterized by abnormal muscle coordination, paralysis of the eye muscles, and absence of the tendon reflexes. Like Guillain-Barré syndrome, symptoms may be preceded by a viral illness.
Some people with MFS might have involvement of other cranial nerves, to include facial and lower bulbar nerve involvement, as well as paresis of shoulder, arm and neck musculature, or might progress to GBS. While MFS is mainly a clinical syndrome, the detection of anti-ganglioside antibodies in serum, CSF studies for increased protein content, EMG and brainstem MRI may be helpful in achieving a diagnosis. Greater than 90% of people with MFS have serum antibodies to the gangliosides, 'GQ1b,' and, 'GT1a,' yet these might also be found in people with rare overlapping syndromes. The antibodies are most likely induced during antecedent infection by molecular mimicry and are pathogenic for peripheral nerves in animal bio-assays. People with severe MFS, bulbar weakness, or progression to GBS may benefit from treatment with intravenous immunoglobulin or plasma exchange, although the therapeutic effects have not been studied in randomized, controlled studies.
MFS, Features, Natural Course and Prognosis
In the year 1956, Dr. Charles Miller Fisher described three people with the clinical triad of ataxia, areflexia and ophthalmoplegia without prominent signs of peripheral neuropathy. Follow publication, people presenting with this clinical triad were referred to as having the Miller Fisher syndrome (MFS). The initial symptom is usually diplopia and/or limb and gait ataxia. The full clinical picture of ataxia, areflexia and ophthalmoplegia commonly develops within five to ten days. The diplopia usually advances over a number of days and might result in a complete ophthalmoplegia, including areflexia, or a pure external ophthalmoplegia with average pupil reflexes.
The majority of people with MFS show a monophasic and benign course of disease leading to complete remission without residual deficits. Most people with MFS spontaneously begin to improve within two to four weeks following the onset of neurological symptoms. The recovery process is usually completed following weeks to months with a mean recovery time of ten weeks. A portion of those affected; however, will develop bulbar weakness with swallowing disturbances requiring intubation or progress to GBS with severe tetraparesis or respiratory insufficiency.
MFS Epidemiology and Differential Diagnosis
Miller Fisher syndrome is a rare disease. The incidence is not precisely known and might vary between geographical areas. Based upon a survey study performed in the South-West of the Netherlands, the incidence of MFS is estimated to be approximately one to two per million each year. Around one-third of people with MFS will progress to GBS and approximately five-percent of people with GBS began as MFS. Men are twice as likely to be affected as women. MFS may affect people from any age group, to include children.
A diagnosis is based on the clinical symptoms and the presence of serum antibodies to the ganglioside GQ1b and GT1a. Additional causes of these clinical features need to be excluded.
Serum in the acute stage of disease, prior to treatment, in more than 90% of people with MFS contain antibodies to GQ1b and GT1a, which may be determined by ELISA. Anti-GQ1b antibodies in serum from people with MFS are usually of the IgG isotype, although IgM and IgA to GQ1b may also be present. The antibodies commonly disappear within weeks with clinical improvement. Antibodies to other disialosyl gangliosides, to include GT1a, GD1b, GD3 and Gtba might also be detected less often.
MFS Genetics and Therapy
Miller Fisher syndrome does not occur in families. Polymorphisms in immune response genes might be involved in the susceptibility to develop cross-reactive antibodies following infection leading to MFS. No genetic susceptibility genes have been identified at this point, although they are being investigated.
Supportive treatment is usually sufficient in people with mild MFS, considering the monophasic and benign course of disease. People with more severe MFS who develop swallowing difficulties or progression to GBS may benefit from specific treatment, although no randomized controlled trials have been performed to demonstrate treatment efficacy. Based on the parallels with GBS and the results of case studies in people with the syndrome, treatment with intravenous immunoglobulin or plasma exchange may be effective. The effect of the combination of intravenous immunoglobulin and methylprednisolone remains unknown. Treatment with methylprednisolone alone has not been studied in MFS, although the results in GBS indicate it is not effective.