What is Miller Fisher syndrome (MFS), a rare neurological disorder?

From the Guidelines

Miller Fisher syndrome is a rare neurological disorder that should be treated with caution, and the current recommendation is to monitor patients closely, as most recover completely without treatment within 6 months, but a subgroup can develop severe complications, and treatment with intravenous immunoglobulin (IVIG) or plasma exchange may be considered in severe cases. The condition is characterized by the triad of ophthalmoplegia (eye muscle weakness), ataxia (poor coordination), and areflexia (absence of reflexes) 1. It's considered a variant of Guillain-Barré syndrome and typically develops after a viral or bacterial infection, most commonly Campylobacter jejuni.

Key Considerations

• The disease course of Miller Fisher syndrome can be relatively mild, but a subgroup of patients can develop limb weakness, bulbar or facial palsy, or respiratory failure, which requires prompt treatment 1.
• Treatment with IVIG or plasma exchange may be considered in severe cases, although evidence for the efficacy of treatment in this context is limited 1.
• Supportive care is essential, including monitoring respiratory function, as some patients may develop breathing difficulties, and physical therapy helps manage ataxia and maintain muscle strength.
• Early diagnosis and treatment improve outcomes, with prompt neurological evaluation recommended for anyone developing the characteristic symptoms, especially following a recent infection.

Diagnostic Approach

• MRI of the entire brain without and with IV contrast is the preferred modality for initial assessment, especially for posterior fossa evaluation, as it offers better visualization compared to CT 1.
• MRI with susceptibility weighted imaging or gradient echo T2-weighted sequences is useful for the detection of blood products in superficial siderosis, and diffusion weighted imaging can help to assess for an abscess or a highly cellular tumor 1.

From the Research

Definition and Characteristics of Miller Fisher Syndrome

• Miller Fisher syndrome (MFS) is a rare variant of Guillain-Barré syndrome, characterized by ophthalmoplegia, ataxia, and areflexia 2
• It is an acute, autoimmune response that typically follows either an upper respiratory or diarrheal illness 3
• The antiganglioside anti-GQ1b IgG antibody has a role in the pathogenesis of the syndrome, especially of ophthalmoplegia 2

Diagnosis and Treatment

• Diagnosis is based on the presence of anti-GQ1b antibodies in the serum, which can be identified in over 80% of patients 2
• Treatment options include supportive respiratory care, intravenous immunoglobulin therapy, or plasmapheresis 3, 4
• Plasmapheresis may remove humoral factors, including anti-GQ1b, and may induce a shift of the Th1/Th2 cytokine-producing cell balance in peripheral blood 4

Prognosis and Outcome

• The outcome of MFS is usually good with a case fatality of < 5% 2
• The annual incidence is around one patient per one million population 2
• Most patients recover fully, but some may experience residual neurological deficits 5

Electrophysiological Findings

• The most consistent electrophysiological findings in MFS are reduced sensory nerve action potentials and absent H reflexes 2
• More variability is seen with F waves and various investigations involving cranial structures 2

Rare Cases and Complications

• In rare cases, MFS can mimic brain death, but it is not associated with irreparable structural damage of the brain 5
• Treatment with alemtuzumab has been successful in a patient with refractory Guillain-Barré syndrome and chronic lymphocytic leukemia 6