Acute Flaccid Myelitis


What is acute flaccid myelitis (AFM)?

AFM is an uncommon disease that resembles polio. The disease is one of the nervous system. Muscle tone and responses become weak (flaccid). Although AFM is rare, it can be very serious, even to the point of making breathing difficult.

Before being described in 2014, AFM might have been diagnosed as a type of transverse myelitis. However, one difference between AFM and transverse myelitis has been found by magnetic resonance imaging (MRI) scans. The gray matter of the spinal cord is inflamed in people with AFM.

The number of cases of AFM has been rising. However, the Centers for Disease Control and Prevention predict that less than 1 person per 1 million people per year in the US will develop AFM. So far, most of the reported cases have involved people younger than age 18, but adults can get AFM.

Symptoms and Causes

What are the causes of acute flaccid myelitis (AFM)?

This disease, and diseases like it, may be caused by germs such as viruses, toxins or poisons in the environment, and possibly genetic issues. Some viruses that have been linked with AFM cases include the West Nile virus, poliovirus, and adenoviruses. Non-polio enteroviruses have also been linked to AFM and to diseases of the nervous system like AFM. Prior to the weakness setting in, the person with AFM often has symptoms of a cold-like illness, with fever and breathing issues.

What are the symptoms of acute flaccid myelitis (AFM)?

The onset of AFM is sudden (acute). Symptoms include:

  • Weakness in one or more limbs (arms, legs)
  • Flabby muscles affecting the face, head and neck, which might cause one side of the face to fall lower than the other
  • Unresponsive muscles and nerves in the mouth or throat that cause problems with swallowing or talking
  • Weakness in the eyes, so that you have drooping eyelids or problems moving your eyes.
  • Weakness in muscles and nerves in the respiratory system. You could have problems breathing, resulting in respiratory failure. At that point, a ventilator (a machine that breathes for you) is needed.
  • Pain in an arm or leg
  • Inability to urinate

With AFM, severe symptoms could result in partial paralysis or paralysis (inability to move the muscles). It is also possible that only one limb is affected severely. People with AFM generally do not have the spastic movements of someone with transverse myelitis.

Diagnosis and Tests

How is acute flaccid myelitis (AFM) diagnosed?

It might be hard to diagnose AFM because it resembles other neurological conditions. The following tests may be used:

  • Physical examination and patient history
  • An MRI of the spinal cord and brain
  • Cerebral spinal fluid (CSF) removal and testing
  • Nerve response testing like nerve conduction velocity (nerve speed) tests
  • Muscle response tests like electromyography
  • Tests of bodily fluids like blood or mucus

Management and Treatment

How is acute flaccid myelitis (AFM) treated?

There are no specific treatments for acute flaccid myelitis. Physical and occupational therapy to restore movement is seen as being very important. Some doctors might recommend treatments, like steroids, antivirals or immunoglobulin, which have been used to treat transverse myelitis and other neurological conditions. There is, as yet, little evidence that these are effective.

Sometimes, it is possible to transfer nerves from a functioning site to the affected site. These procedures are often best done by surgeons who specialize in hands and upper extremities.


How can you prevent acute flaccid myelitis (AFM)?

To prevent AFM, doctors recommend that you:

  • Get your vaccines on schedule, especially the polio vaccine.
  • Try to stay away from mosquitoes that can transmit viruses by not going outside when they are biting (dusk and dawn). Use products that repel mosquitoes, and do not allow water to collect near your home.
  • Follow good hand washing practices—using soap and water and washing frequently—is good advice to prevent illness in general. Also, wash your hands before and after eating; after using the bathroom or touching an animal; before and after taking care of someone who is sick or has a cut.
  • Avoid being around people who are sick if you can.
  • Do not share eating utensils or cups, straws, or cigarettes.
  • Use disinfectant to clean hard surfaces.

Outlook / Prognosis

What is the prognosis (outlook) for patients who have acute flaccid myelitis (AFM)?

The long-term outlook for patients with AFM is not known. It is possible that the prognosis for people with mild AFM symptoms might be better than the outlook for someone with severe symptoms. Some people may recover fully and quickly. Most people have muscle weakness that lingers for a long time.

Living With

When should I call the doctor about acute flaccid myelitis (AFM)?

If you or your child have a leg or arm that suddenly gets weak and does not function well, you should call the doctor right away. If you or your child also show any other symptom (problems of the face, mouth, eyes), call your doctor right away. Difficulty breathing always requires immediate medical attention.


Are there any resources for people affected by acute flaccid myelitis (AFM)?

Transverse Myelitis Association
1787 Sutter Parkway
Powell, OH 43065-8806
Toll-free: 1-855-380-3330
Telephone: 614-317-4884
E-mail: [email protected]

Also, there are current Facebook groups related to AFM. In addition, you might want to contact your local health department.

Last reviewed by a Cleveland Clinic medical professional on 10/23/2018.


  • Centers for Disease Control and Prevention. Acute flaccid myelitis. ( Accessed 10/23/2018.
  • Genetic and Rare Diseases Information Center. Acute flaccid myelitis. ( Accessed 10/23/2018.
  • Transverse Myelitis Association. Acute flaccid myelitis (AFM). ( Accessed 10/23/2018.

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