A 28-year-old man develops diplopia, unsteady gait, and blurred vision over 3 days after a diarrhoeal illness. Examination shows external ophthalmoplegia, limb and gait ataxia, and globally absent tendon reflexes. Pupils are spared. Which antibody is most likely positive?

• A Anti-GQ1b ✓
• B Anti-GM1
• C Anti-GD1a
• D Anti-MAG

Explanation

Ophthalmoplegia, ataxia, and areflexia form the Miller Fisher syndrome triad, a variant of Guillain-Barre syndrome strongly linked to IgG antibodies against the ganglioside GQ1b, which is highly expressed in cranial nerve paranodes. Anti-GM1 and anti-GD1a associate with axonal motor GBS variants, and anti-MAG with chronic demyelinating neuropathy in older adults. Preserved pupils help distinguish Miller Fisher syndrome from botulism, its closest mimic.

Reference: Adams and Victor's Principles of Neurology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.