Acute motor axonal neuropathy
AMAN is characterized by symmetric limb weakness, facial and oropharyngeal muscle weakness, areflexia, and respiratory insufficiency. A variant is AMSAN, which involves damage to axons of sensory neurons in addition to those of motor neurons and is characterized by acute onset of quadriparesis, distal sensory loss, areflexia, and respiratory insufficiency. There can also be autonomic dysfunction in both diseases. AMAN typically progresses to nadir more rapidly than AIDP.
The exact etiology is unclear, but GBS typically presents days to weeks after an infection, most commonly Campylobacter jejuni. Other reported triggers include cytomegalovirus, influenza, Epstein-Barr virus, HIV, and Japanese encephalitis. Of note, GBS has been reported in patients with probable Zika virus infection in South America, French Polynesia, Latin America, and the Caribbean. Rarely, GBS has been associated with surgery or immunization. There have been rare reports of GBS occurring about 2 weeks after having the Johnson & Johnson (Janssen) COVID-19 vaccine.
AMAN occurs more frequently in China and Japan. It often progresses more rapidly than AIDP. Recovery is unpredictable; some patients recover completely in days, while others have slow and incomplete recovery.
G61.0 – Guillain-Barre syndrome
715770009 – Acute motor axonal neuropathy
Differential Diagnosis & Pitfalls