A 35-year-old woman presents with ascending weakness over 3 weeks following a Campylobacter jejuni diarrhoeal illness 4 weeks earlier. NCS shows reduced CMAP amplitudes with normal conduction velocities and no demyelination. Anti-GM1 ganglioside antibodies are positive. What subtype of GBS does this represent?

• A Acute inflammatory demyelinating polyneuropathy (AIDP)
• B Acute motor axonal neuropathy (AMAN) ✓
• C Miller Fisher syndrome
• D Bickerstaff brainstem encephalitis

Explanation

Acute motor axonal neuropathy (AMAN) is a pure motor axonal variant of GBS strongly associated with Campylobacter jejuni infection and anti-GM1 (also anti-GD1a) antibodies. NCS shows reduced CMAP amplitudes without demyelination, distinguishing it from AIDP (which shows slowed velocities, prolonged latencies, conduction block). AMAN is more prevalent in China and can have rapid recovery or prolonged course. Miller Fisher syndrome presents with ophthalmoplegia, ataxia, and areflexia with anti-GQ1b antibodies.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.