In Guillain-Barré Syndrome (GBS), which electrodiagnostic and clinical finding MOST reliably predicts a severe motor axonopathy subtype (AMAN) rather than AIDP?

• A Elevated CSF protein with normal cell count (albumino-cytological dissociation)
• B Anti-GM1 or anti-GD1a ganglioside antibodies with pure motor involvement and preserved sensory nerve action potentials ✓
• C Pronounced sensory ataxia with anti-GQ1b antibodies
• D Demyelinating pattern with prolonged distal motor latencies and conduction block

Explanation

Acute motor axonal neuropathy (AMAN) is characterised by anti-GM1 or anti-GD1a IgG antibodies targeting nodes of Ranvier on motor axons, leading to pure motor weakness with preserved or normal sensory nerve conduction. Albuminocytological dissociation occurs in both AMAN and AIDP. Sensory ataxia with anti-GQ1b is Miller Fisher syndrome. Demyelinating features (prolonged DML, conduction block, slowed NCV) are hallmarks of AIDP. AMAN is prevalent in Asia, often post-Campylobacter jejuni, and recovery may be faster despite axonal changes due to reversible paranodal injury.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.