Acute Flaccid Myelitis (AFM)

Acute Flaccid Myelitis (AFM) Facts

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Acute flaccid myelitis (AFM) is a rare but serious problem with the nervous system in the area of the spinal cord (gray matter) that causes muscles and reflexes in the body to become weak.

Acute flaccid myelitis (AFM) facts written by Melissa Conrad Stöppler, MD

  • Acute flaccid myelitis (AFM) is a rare disease that damages the spinal cord.
  • AFM is often associated with having a viral infection prior to disease onset, but sometimes medical professionals cannot identify the cause.
  • Symptoms and signs of AFM can include sudden (acute) weakness in the arms or legs, loss of muscle tone, decreased reflexes, and weakness of the facial muscles.
  • AFM is not contagious from person to person.
  • The prognosis or outlook for AFM is variable as is the recovery time from the symptoms.
  • There is no specific treatment available for AFM.
  • AFM can occur in adults or children, but it is most common in children.
  • A vaccine against AFM is not available, and there is no specific way to prevent its development.

What Is Acute Flaccid Myelitis (AFM)?

Acute flaccid myelitis (AFM) is a rare disease that affects the spinal cord, the part of the nervous system that carries messages to and from the brain.

What Are Signs and Symptoms of Acute Flaccid Myelitis?

  • Symptoms of AFM include sudden (acute) weakness in the arm(s) or leg(s), along with loss of muscle tone and decreased or absent reflexes.
  • Some people with AFM report pain.
  • In some cases, AFM can affect the nerves controlling the head and neck, causing facial weakness, drooping of the eyelids, and difficulty swallowing, speaking, or moving the eyes.

What Are Complications of Acute Flaccid Myelitis?

  • The most serious complication of AFM is a respiratory failure if the muscles involved with breathing become weakened.
  • Most cases of AFM have been in children, but it can develop in adults.

What Causes Acute Flaccid Myelitis?

  • Many times symptoms of AFM develop after a viral infection, such as poliovirus, West Nile virus, and adenovirus.
  • In some cases no clear possible cause is found.
  • In addition, even when associated with a viral infection, it is not known how the infection triggers AFM, and it is not clear why some people develop AFM after an infection and others do not.

What Tests Do Health Care Professionals Use to Diagnose Acute Flaccid Myelitis?

  • AFM can be difficult to diagnose because the symptoms are similar to other neurological diseases, such as Guillain-Barre syndrome (GBS), acute disseminated encephalomyelitis (ADEM), and transverse myelitis.
  • Diagnosis may include a physical exam, an MRI of the spine, testing of the cerebral spinal fluid (CSF), and tests checking nerve speed (nerve conduction velocity; NCV) and the response of muscles to the messages from the nerves (electromyography; EMG).

Is It Possible to Prevent Acute Flaccid Myelitis With a Vaccine?

To prevent infections by AFM-related viruses, specialists recommend staying up-to-date with polio vaccines and to minimize exposure to mosquitoes.

What Is the Treatment for Acute Flaccid Myelitis?

  • There is no specific treatment for AFM.
  • Treatments that have been tried include immunoglobulin, corticosteroids, plasma exchange, and antiviral therapy, but there is no clear evidence that any of these treatments affect recovery.
  • Other treatment is supportive and depends on the symptoms.

What Is the Recovery Time and Prognosis for Acute Flaccid Myelitis?

  • Physical therapy and occupation therapy are especially important during recovery.
  • The extent of recovery varies. Although some people may make a full recovery, most have continued muscle weakness even after a year.
  • Long term outcomes are not known.

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Acute Flaccid Myelitis Symptom

Difficulty Swallowing (Dysphagia)

  • Dysphagia means difficulty swallowing. Odynophagia means painful swallowing. Sometimes it is not easy for individuals to distinguish between these two problems.
  • For example, food that sticks in the esophagus (swallowing tube) can be painful. Is this dysphagia or odynophagia or both? Technically it is dysphagia, but individuals may describe it as painful swallowing (odynophagia).
  • Nevertheless, it is important to attempt to distinguish between the two because the causes of each may be quite different. When dysphagia is mild, it may cause an individual only to stop eating for a minute or less and drink a few sips of water.
  • When it is severe, however, it can prevent an individual from eating and taking in enough calories for adequate nutrition and to maintain weight.
  • Some conditions associated with dysphagia affect the area of the lower throat, primarily conditions in which there are abnormalities of nerves or muscles that control the function of the throat. This area also is the area from which the trachea, the main airway leading to the lungs, begins.

United States. National Institutes of Health. Genetic and Rare Diseases Information Center. "Acute Flaccid Myelitis." Oct. 9, 2018. <>.