What are the diagnostic criteria and treatment options for Miller Fisher syndrome?

Miller Fisher Syndrome: Diagnosis and Treatment

Miller Fisher Syndrome (MFS) is diagnosed based on the classical triad of ophthalmoplegia, ataxia, and areflexia, with confirmation through anti-GQ1b antibody testing and supportive cerebrospinal fluid findings. 1, 2

Diagnostic Criteria

Core Clinical Features

• The clinical triad of MFS consists of:
  • Ophthalmoplegia (eye movement abnormalities) 1, 2
  • Ataxia (difficulty with coordination and balance) 2
  • Areflexia (reduced or absent deep tendon reflexes) 2

Laboratory Investigations

• Anti-GQ1b IgG antibody testing:
  • Present in over 80% of MFS cases 3
  • Peaks in the first week of illness 3
  • Highly specific for the diagnosis 3
• Cerebrospinal fluid analysis:
  • Albuminocytological dissociation (elevated protein with normal cell count) 3
  • May appear later in the disease course 3
  • Opening pressure may be elevated in some cases 4

Electrophysiological Studies

• Most consistent findings in MFS:
  • Reduced sensory nerve action potentials 3
  • Absent H reflexes 3
  • Variable F wave abnormalities 3
• These studies help differentiate MFS from other neuromuscular disorders 1

Atypical Presentations

• Approximately 30% of MFS patients may present with symptoms beyond the classic triad: 5

  • Headache (periorbital, temporal, or generalized) 5
  • Delayed facial nerve palsy 5
  • Divergence insufficiency without external ophthalmoplegia 5
  • Taste impairment 5
  • Pure sensory polyneuropathy 6
  • Respiratory compromise 7

• Incomplete forms of MFS may occur with isolated:

  • Ataxia (acute ataxic neuropathy) 1
  • Ophthalmoplegia (acute ophthalmoplegia) 1

Treatment Options

First-line Treatments

• Intravenous immunoglobulin (IVIG):

  • Recommended dosage: 0.4 g/kg/day for 5 days (total dose 2 g/kg) 2
  • Shown to improve symptoms in case reports 4, 7

• Plasmapheresis (plasma exchange):

  • Alternative to IVIG with similar efficacy 2, 3
  • Typically performed over 5 days 2

Adjunctive Therapy

• Corticosteroids:
  • Not recommended as monotherapy 2
  • May be considered in combination with IVIG in severe cases 2
  • Can be effective when IVIG alone fails to halt disease progression 4

Supportive Care

• Regular monitoring of respiratory function:

  • Vital capacity measurements 2
  • Negative inspiratory force testing 7
  • 15-30% of cases may require ventilatory support 2

• Daily neurological assessments to track disease progression 2

Prognosis

• Generally favorable prognosis with case fatality rate <5% 3
• Most patients recover within weeks to months 3
• Overlap with classical Guillain-Barré syndrome occurs in approximately 15% of patients 1, 2

Clinical Pearls

• MFS accounts for 5-25% of all Guillain-Barré syndrome cases 1, 2
• Recent infections, particularly gastrointestinal (Campylobacter jejuni) or respiratory, often precede MFS 7
• Anti-GM1-IgM antibodies may be present in some cases, even when anti-GQ1b antibodies are negative 4
• Neuroimaging is typically normal but may occasionally show contrast enhancement of nerve roots 3
• Consider MFS in the differential diagnosis of acute onset ophthalmoplegia, even when the full triad is not initially present 7