Acute Motor Axonal Neuropathy (AMAN)

Acute Motor Axonal Neuropathy (AMAN) is a rare autoimmune disorder that affects the motor nerves responsible for muscle movement. It is considered a variant of Guillain-Barre Syndrome (GBS) and causes rapid muscle weakness or paralysis, typically starting in the legs and moving upward. Unlike the more common type of GBS (AIDP), AMAN does not affect sensory nerves, meaning people usually do not have numbness or tingling, just motor weakness.

Sudden weakness or paralysis especially in legs and arms; Reflexes are lost (areflexia); No sensory loss - pain, touch, and temperature sensations usually remain intact; May involve difficulty breathing or swallowing in severe cases; Symptoms often worsen over days.

Caused by an autoimmune attack on the axons (the long parts of motor nerves) rather than the myelin sheath. Often triggered by bacterial infections especially Campylobacter jejuni, viral infections, or less commonly after vaccinations or other immune stressors.

Clinical exam showing weakness without sensory loss; Nerve conduction studies (NCS/EMG) showing axonal rather than demyelinating damage; Spinal tap (lumbar puncture) may show elevated protein with normal cell count; Antibody testing may show anti-GM1 or anti-GD1a antibodies.

IVIG (intravenous immunoglobulin) is first-line. Plasmapheresis (plasma exchange) as alternative if IVIG does not work. Supportive care including breathing support, nutrition, physical therapy. Steroids are not typically used.

Many people recover completely or significantly especially with early treatment. Recovery may be slower than in other GBS forms. Some people may experience long-term weakness or motor deficits. Children often recover faster and more fully than adults.

Extremely rare in the U.S.; more common in Asia and Latin America. Often occurs in children or young adults. Usually appears in summer months, often after a stomach infection.