# What is acute flaccid myelitis (AFM)? Canonical page: https://clinicsjo.com/en/faq/what-is-acute-flaccid-myelitis-afm Language: en Category: neurology Publisher: ClinicsJo Published: 2026-09-11T14:50:43.627Z Content updated: 2026-09-11T14:50:43.627Z Translation (ar): https://clinicsjo.com/ar/faq/what-is-acute-flaccid-myelitis-afm Acute flaccid myelitis, or AFM, is a rare neurological disorder that affects part of the spinal cord and causes sudden weakness in the limbs. It occurs most often in children and may begin after a respiratory illness or fever, although the exact cause is not fully understood. AFM is important because weakness or loss of strength can progress quickly, so sudden weakness in an arm or leg requires immediate medical assessment. [\[1\]]() [\[2\]]() ## What happens in acute flaccid myelitis? AFM is a disorder of the nervous system, particularly involving an area of the spinal cord associated with muscle movement. The word “flaccid” refers to muscles becoming weak and floppy when the nerve pathways controlling movement are affected. Weakness may involve one limb or several limbs and may occur with changes in muscle tone or reflexes. The condition is rare and can vary in severity, so not every episode of limb weakness indicates AFM. [\[1\]]() [\[3\]]() ## What symptoms can occur? The main symptom is sudden weakness in the arms or legs. Some people may also have difficulty moving the eyes, drooping eyelids, facial changes, or difficulty swallowing or speaking. Pain in the neck, back, or limbs can occur, and breathing can be affected when the muscles used for breathing are involved. Sources state that some patients have symptoms resembling a viral illness before weakness begins, such as fever or respiratory symptoms. [\[2\]]() [\[3\]]() ## What is its relationship to viral infections? Viruses, including enteroviruses, can cause AFM, and the condition has attracted attention because of seasonal patterns among children. However, having a viral infection before weakness does not mean that one specific virus has been proven to cause every case. The CDC states that researchers continue to study the causes of AFM and that the exact mechanism is not completely understood. It is therefore important not to claim that the cause is known in every patient or that preventing one particular virus can definitively prevent AFM. [\[2\]]() ## When is the condition an emergency? Sudden weakness in one or more limbs, particularly when it is progressing, requires urgent evaluation. The need for urgent assessment is even greater when difficulty breathing, swallowing, or speaking, or other sudden neurological changes occur. AFM cannot be diagnosed from symptoms alone because other causes of acute weakness can also require rapid assessment. Diagnosis depends on the medical history, neurological examination, and appropriate testing, which may include imaging, spinal fluid testing, and other investigations depending on the situation. [\[1\]]() [\[2\]]() [Acute Flaccid Myelitis in Children: Symptoms and Prevention (Arabic)]() ## Medical references - [Acute Flaccid Myelitis]() - [About Acute Flaccid Myelitis]() - [Acute flaccid myelitis]() General health education; not a substitute for individualized clinical assessment. Citation URL: https://clinicsjo.com/en/faq/what-is-acute-flaccid-myelitis-afm#answer