A 30-year-old man presents with ascending weakness after a Campylobacter gastroenteritis 3 weeks ago. NCS shows prolonged distal latencies, absent H-reflexes, and markedly reduced CMAP amplitudes with conduction block. CSF shows albuminocytological dissociation. Antibody testing shows anti-GM1 IgG. The NCS pattern suggests which variant of GBS?
- A Acute inflammatory demyelinating polyradiculoneuropathy (AIDP)
- B Acute motor axonal neuropathy (AMAN) ✓
- C Miller Fisher syndrome (MFS)
- D Bickerstaff brainstem encephalitis (BBE)
Explanation
Anti-GM1 IgG antibodies are strongly associated with AMAN (acute motor axonal neuropathy), a GBS variant caused by molecular mimicry between Campylobacter jejuni lipooligosaccharides and ganglioside GM1 on motor nerve nodes of Ranvier. NCS in AMAN shows absent or very reduced CMAP (motor) with preserved SNAP (sensory), which differs from AIDP (demyelinating features: prolonged latencies, reduced NCV, conduction block). AIDP shows demyelinating NCS pattern. Miller Fisher syndrome is associated with anti-GQ1b antibodies (ophthalmoplegia, ataxia, areflexia). Bickerstaff encephalitis has anti-GQ1b with CNS involvement (altered consciousness).
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.