What are the characteristics of the acute motor axonal neuropathy (AMAN) subtype of Guillain-Barre syndrome (GBS)?

Updated: Jul 14, 2021
  • Author: Michael T Andary, MD, MS; Chief Editor: Milton J Klein, DO, MBA  more...
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The acute motor axonal neuropathy (AMAN) subtype is a purely motor disorder that is more prevalent in pediatric age groups. [14] AMAN is generally characterized by rapidly progressive symmetrical weakness and ensuing respiratory failure.

Nearly 70-75% of patients with AMAN are seropositive for Campylobacter, with the majority of cases of AMAN being associated with preceding C jejuni diarrhea. Patients typically have high titers of antibodies to gangliosides (ie, GM1, GD1a, GD1b). Inflammation of the spinal anterior roots may lead to disruption of the blood-CNS barrier. [12] Biopsies show wallerianlike degeneration without significant lymphocytic inflammation.

Many cases have been reported in rural areas of China, especially in children and young adults during the summer months. [15] Pure axonal cases may occur more frequently outside of Europe and North America. AMAN cases may also be different from cases of axonal GBS described in the West.

Prognosis is often quite favorable. Although recovery for many is rapid, severely disabled patients with AMAN may show improvement over a period of years. [16]

One third of patients with AMAN may actually be hyperreflexic. Although the mechanism for this hyperreflexia is unclear, dysfunction of the inhibitory system via spinal interneurons may increase motor neuron excitability. Hyperreflexia is significantly associated with the presence of anti-GM1 antibodies. [8]

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