Classical Features of Miller-Fisher Syndrome
Miller-Fisher syndrome (MFS) is characterized by the clinical triad of ophthalmoplegia, ataxia, and areflexia. 1
Core Clinical Manifestations
- Ophthalmoplegia: Eye movement abnormalities are a hallmark feature, which may begin unilaterally but typically progresses to bilateral involvement 2, 3
- Ataxia: Difficulty with coordination and balance, often presenting as an unsteady gait 1
- Areflexia: Reduced or absent deep tendon reflexes 1
Additional Clinical Features
- Facial weakness or facial palsy may occur in some cases 4, 3
- Paresthesias (sensory symptoms) in the extremities 3
- Dysphonia (voice disturbance) can be present 3
- Ptosis (drooping eyelids) may accompany the ophthalmoplegia 4
Epidemiology and Prevalence
- MFS accounts for approximately 5-25% of all Guillain-Barré syndrome cases 1
- Annual incidence is approximately one patient per million population 5
- May occur in incomplete forms with isolated ataxia or ophthalmoplegia 1
- Overlaps with classical sensorimotor GBS in approximately 15% of patients 1
Pathophysiology
- Associated with anti-GQ1b IgG antibodies, which can be identified in over 80% of patients 5, 6
- These antibodies typically peak in the first week of illness 5
- Considered to be an autoimmune response that typically follows an upper respiratory or diarrheal illness 3
Diagnostic Findings
- Cerebrospinal fluid analysis: Typically shows albuminocytologic dissociation (elevated protein with normal cell count), though this may appear later in the course 5
- Serum testing: Presence of anti-GQ1b antibodies is highly specific for MFS 1, 5
- Electrophysiological findings: Most consistently shows reduced sensory nerve action potentials and absent H reflexes 5
- Neuroimaging: Usually normal, though in rare cases may show contrast enhancement of nerve roots 5
Related Conditions
- MFS is part of a spectrum that includes Guillain-Barré syndrome and Bickerstaff brainstem encephalitis, sometimes referred to as the "anti-GQ1b syndrome" 5
- Can occasionally present with multiple autoimmune conditions 4
Prognosis
- Generally has a good prognosis with case fatality rate of less than 5% 5
- Most cases are self-limited with excellent recovery 6
Treatment Considerations
- Intravenous immunoglobulin (IVIG) at 0.4 g/kg/day for 5 days (total dose 2 g/kg) 1
- Plasmapheresis is an alternative treatment option 1, 3
- Corticosteroids may be considered, though their efficacy is less established than in other immune-mediated conditions 1
- Supportive care including respiratory monitoring may be necessary 3