A 24-year-old man presents with ascending weakness and areflexia progressing over 10 days following a Campylobacter jejuni enteritis 3 weeks ago. CSF shows albuminocytological dissociation. Nerve conduction studies show marked reduction in CMAP amplitude with relative preservation of conduction velocity. Which subtype of Guillain-Barré syndrome does this suggest?
- A Acute motor axonal neuropathy (AMAN) ✓
- B Acute inflammatory demyelinating polyradiculoneuropathy (AIDP)
- C Miller Fisher syndrome
- D Acute motor and sensory axonal neuropathy (AMSAN)
Explanation
Reduced CMAP amplitude with preserved conduction velocity indicates axonal rather than demyelinating pathology. AMAN (acute motor axonal neuropathy) is the axonal variant of GBS, strongly associated with preceding Campylobacter jejuni infection and anti-GM1/GD1a antibodies. It affects motor axons without sensory involvement. AIDP (the classic form) shows demyelinating pattern with prolonged distal latencies and slowed conduction velocity. AMSAN additionally involves sensory axons. Miller Fisher syndrome (anti-GQ1b antibodies) presents with the triad of ophthalmoplegia, ataxia, and areflexia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.