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Acute Flaccid Myelitis: What Parents Should Know About a New, Polio-Like Illness 

Prompt diagnosis, careful monitoring important
Acute Flaccid Myelitis: What Parents Should Know About a New, Polio-Like Illness

A rare but frightening polio-like illness is striking more and more kids in the United States. It has also affected children in Australia and Asia.

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“It’s important for parents to seek prompt care for any child with acute flaccid myelitis (AFM),” says pediatric orthopaedic surgeon Joseph Styron, MD, PhD.

“While it usually affects the limbs, in rare cases, AFM can affect the muscles in the respiratory system, making it difficult for children to breathe. This can be life-threatening.”

Parents should seek help from an expert in AFM, he adds. Timely, expert diagnosis allows for close medical monitoring and makes it easier to intervene, if and when needed, to give a child the best possible recovery.

How does AFM develop?

Acute flaccid myelitis, first described in 2014, typically affects children and adolescents up to age 22. It usually follows a viral illness in the upper respiratory tract or GI tract.

“Typically, days or weeks after the illness, a child’s limb or limbs suddenly go limp,” says Dr. Styron. AFM is asymmetrical: It can weaken the muscles in one arm, or one leg, or one arm and one leg.

The viruses most often linked to AFM are called enteroviruses, including EV-D68, EV-A71 and others, according to the Centers for Disease Control and Prevention.

Not all kids with AFM have had a proven enterovirus infection, however.

“Like polio, AFM affects the anterior horn cells in the spinal cord, which are the nerves controlling your muscles,” he explains. Because only motor nerves are affected, kids can still feel the affected limb and protect it from accidental injury. 

Does anything increase a child’s risk?

Nothing appears to make one child more likely to develop acute flaccid myelitis than another. AFM affects kids of all races and backgrounds.

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In fact, sometimes an entire family will get an upper respiratory infection, but only one child will develop AFM.

“Parents should know that AFM is not linked to any type of any vaccination,” stresses Dr. Styron. “It affects kids who have not been vaccinated as well as kids who have been.” 

How do doctors diagnose AFM?

Doctors only need two things to make a diagnosis of AFM:

  1. A history of sudden flaccid paralysis. Flaccid paralysis, caused by an injury to the spinal cord or the peripheral nerves, makes muscles limp. (In comparison, spastic paralysis is caused by an injury to the brain, and makes muscles rigid.)
  2. An MRI of the affected limb. In AFM, magnetic resonance imaging shows a lesion visible in the gray matter of the spinal cord (similar to the gray matter in your brain).

A lumbar puncture can be helpful, but it — and other tests — are not necessary, notes Dr. Styron. 

How is AFM treated?

Unlike more common viral illnesses that affect the nerves — transverse myelitis and Guillain-Barré syndrome — kids with AFM often don’t fully recover their strength.

Experts monitor a child’s recovery from AFM to see how much strength they regain and to make sure they’re stable and doing well.

“But while function improves in many kids, most kids with AFM have persistent weakness that can last for months to years,” says Dr. Styron.

“When weakness is ongoing, we’ll discuss nerve transfer. This should be done six months to one year after the child becomes ill.” 

What is a nerve transfer?

In nerve transfers, experts move a nerve that is working to the nerve that is not working. The new nerve can then start signaling the weakened muscles to move the limb.

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“We look for redundant nerves from working muscles, where a few nerves are doing the same job,” explains Dr. Styron.

“For instance, when an arm is affected, we can swing one of the nerves that helps to shrug the shoulder over, so that it helps to lift the arm at the shoulder instead. This allows for better function.”

When the leg is affected, they can do the same thing using one branch of a leg nerve. 

Hand and upper extremity surgeons are well-suited for these procedures because of their expertise in repairing delicate nerves in the hand. 

Will there be a vaccine for AMF?

There’s a vaccine for polio. It is possible to develop one for AMF? “Hopefully, we’ll have a vaccine someday — but not until we figure out what’s causing this condition,” says Dr. Styron. “At this point, we have no idea why AFM develops.”

As more and more parents seek help, experts can gather more information about the causes and effects of acute flaccid myelitis.

Meanwhile, Dr. Styron has a message for parents.

“It’s scary to see your otherwise healthy child suddenly unable to move an arm or a leg,” he says.

“But you’re not alone. There is plenty of support out there for you — both within the medical community and from other parents of children affected by AFM.”

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