Acute Flaccid Myelitis (AFM) vs.Polio

Polio and acute flaccid myelitis (AFM) are illnesses that cause muscle weakness and paralysis (when you’re not able to move). They both typically affect children.

Polio is a viral infection that paralyzed more than 15,000 people in the U.S. each year -- mostly children -- in the early 1950s. It’s been wiped out in this country thanks to a vaccine, but it's still a problem in some places, including Nigeria, New Guinea, and Somalia.

Doctors don’t know exactly what causes AFM, but many cases seem to be brought on by a viral infection, too. (Researchers aren’t sure how the virus triggers it.)

There’s been a small outbreak in the U.S. in recent years, but it’s still very rare. Fewer than 1 in a million children in the U.S. get the disease each year.

Symptoms

AFM causes sudden weakness in your arms and legs, along with a loss of muscle tone and sometimes pain. Your face may also feel weak.

Other symptoms include:

  • Drooping eyelids and trouble moving your eyes
  • A hard time swallowing or speaking
  • Slurred speech
  • Trouble breathing

With polio, most children who have the virus don't show any signs of it. Only about 1 in 4 kids who are infected have symptoms like these:

These typically last 2 to 5 days, then go away.

A much smaller number of children who get the virus have more serious symptoms like:

  • A pins-and-needles feeling in their legs
  • A hard time moving their arms and legs
  • Trouble breathing

Only about 1 out of every 200 children with the virus has paralysis, but when it happens, it can be permanent.

Diagnosis

Doctors diagnose polio with a physical exam, a swab of your throat, and a stool sample. Your doctor also might take a sample of your blood. These are sent to a lab, where technicians check for the poliovirus.

AFM is harder to diagnose because its symptoms can be a lot like those of other diseases related to your brain and nervous system, such as transverse myelitis and Guillain-Barre syndrome.

Doctors do the following to try to find out if it’s AFM or something else:

  • Check your muscle tone and reflexes with a physical exam
  • Get a closer look at your brain and spinal cord with an MRI scan. This uses radio waves and powerful magnets to make detailed images of the inside of your body.
  • Test the fluid around your brain and spinal cord. This is called a spinal tap or lumbar puncture.
  • See how well your nerves respond to electrical impulses.

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Treatment

There’s no cure for either polio or AFM, but some things can help with symptoms. Children with either polio or AFM may need:

  • Pain relievers like ibuprofen to ease pain and bring down fever
  • Fluids to keep them from being dehydrated
  • A machine called a ventilator to help them breathe
  • Physical therapy to make weak muscles stronger
  • Occupational therapy to help with everyday activities like dressing and eating

Outlook

Most of the time, polio goes away within a few days. Even children who have the most serious kind are rarely paralyzed.

But a small number of people can have symptoms like these years afterward:

Doctors don't know the long-term outlook for AFM. Some people get better and don’t have any lingering effects, while others have weak muscles for a long time afterward.

Prevention

The polio vaccine will help keep your child from getting the virus that causes the disease. Children need four doses of the vaccine at ages:

  • 2 months
  • 4 months
  • 6 to 18 months
  • 4 to 6 years

There’s no vaccine for AFM and no sure way to prevent it. But you can lower your child’s chances of getting a virus that might trigger it:

  • Get them vaccinated against polio.
  • Ward off the West Nile virus by keeping them indoors at dusk and dawn, when mosquitoes are most likely to bite. You also might use bug repellent and get rid of any pots or other sources of standing water near your home where mosquitoes can lay their eggs.
  • Teach your children to wash their hands often with soap and water or to use hand sanitizer.
WebMD Medical Reference Reviewed by Amita Shroff, MD on November 14, 2018
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