SynopsisCodesLook ForDiagnostic PearlsDifferential Diagnosis & PitfallsBest TestsManagement PearlsTherapyReferences
Emergency: requires immediate attention
Acute motor axonal neuropathy
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Acute motor axonal neuropathy

Contributors: Jamie Adams MD, Richard L. Barbano MD, PhD
Other Resources UpToDate PubMed


Guillain-Barré syndrome (GBS) represents a spectrum of rare acute immune-related polyneuropathies with varying features and presentations. It is divided into 2 main subtypes: demyelinating and axonal. Demyelinating forms include acute inflammatory demyelinating polyneuropathy (AIDP) and clinical variant Miller Fisher syndrome (MFS). Axonal forms include acute motor axonal neuropathy (AMAN) and acute motor-sensory axonal neuropathy (AMSAN).

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

Look For

Subscription Required

Diagnostic Pearls

Subscription Required

Differential Diagnosis & Pitfalls

  • Acute inflammatory demyelinating polyneuropathy
  • Chronic inflammatory demyelinating polyneuropathy (CIDP)
  • Spinal cord compression
  • Transverse myelitis
  • Poliomyelitis
  • West Nile virus
  • Myasthenia gravis
  • Amyotrophic lateral sclerosis
  • Lead poisoning
  • Mercury poisoning
  • Hypermagnesemia
  • Organophosphate poisoning
  • Porphyria (eg, Acute intermittent porphyria, Variegate porphyria)
  • Botulism
  • Periodic paralysis (eg, Familial hypokalemic periodic paralysis)
  • Tick paralysis
  • Thallium poisoning

Best Tests

Subscription Required

Management Pearls

Subscription Required


Subscription Required


Subscription Required

Last Reviewed:02/07/2018
Last Updated:08/01/2021
Copyright © 2024 VisualDx®. All rights reserved.
Emergency: requires immediate attention
Acute motor axonal neuropathy
A medical illustration showing key findings of Acute motor axonal neuropathy : Flaccid paralysis, Muscle weakness
Copyright © 2024 VisualDx®. All rights reserved.