• Children's Center

    Mayo Clinic physician concerned by increase in cases of acute flaccid myelitis

a sick child sleeping in a hospital bed with an IV in his or her hand

The Centers for Disease Control and Prevention (CDC) has been reporting a dramatic increase in cases of acute flaccid myelitis since August 2014. To date, the CDC has confirmed at least 386 cases of acute flaccid myelitis across the U.S. At least six of those cases have been reported in Minnesota since September.

Acute flaccid myelitis is a poliolike condition that causes weakness in a person's arms or legs, most often occurring in children.

Dr. Kenneth Mack, a Mayo Clinic pediatric neurologist described the uptick in cases as concerning. He says the specific cause of acute flaccid myelitis is still unknown, but it generally appears immediately after an infection.

"We think that there's a group of viruses called enterovirus that may play a role in this," Dr. Mack says. "And in the course of fighting the infection, what probably happens is that the body fights some of the cells within the spinal cord that control motor movement of these limbs."

Dr. Mack says that while acute flaccid myelitis has been identified for decades, there has been a dramatic increase in cases in recent years, with 2014, 2016 and 2018 having significantly higher rates than in the past.

"Oftentimes [this condition] would present at a time where you would see a lot of infections from enteroviruses, which is the summer-fall season," Dr. Mack says. "And probably ... most of the cases in years past seem to have [had] a September or October presentation."

But there are still a lot of questions about the role of enteroviruses in acute flaccid myelitis.

"There's over 100 different types of enterovirus," Dr. Mack says. "And these specific enteroviruses that are thought to play a role in acute flaccid myelitis have been known to exist at least since the 1960s. And, so, why they are now causing this problem and why they are causing it in some children and not others is not really well-known."

The CDC reports that there are other possible causes for acute flaccid myelitis, including environmental toxins and genetic disorders.

Watch: Mayo Clinic physician discusses concerning increase in cases of acute flaccid myelitis.

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Dr. Mack says acute flaccid myelitis generally is not painful. But the CDC recommends parents look for these symptoms in their children:

  • Weakness and loss of muscle tone and reflexes in the arms or legs
  • Facial droop or weakness
  • Difficulty moving the eyes
  • Drooping eyelids
  • Difficulty swallowing
  • Slurred speech

The CDC reports that the long-term prognosis for children with acute flaccid myelitis is still unknown. Dr. Mack says children in some cases have shown significant improvement in their symptoms over time, while others have seen little to no improvement. At this point, treatment effort is focused mainly on improving symptoms – not curing the illness.

"We're first concentrating on making sure we have the correct diagnosis," Dr. Mack says. "And then we are typically trying to support the child. Sometimes some of these children will receive medicines called "IVIG," which is an IV medicine used to adjust and rectify the immune system. Sometimes some of these children may receive antibiotic or antiviral medications. The prognosis is concerning. And families and doctors have a right to be concerned."

Since the cause of acute flaccid myelitis is still not understood, it's difficult to know how to prevent it. The CDC recommends staying up to date on all vaccinations and avoiding mosquito bites.

"The CDC [also] has recommended the types of normal hygiene stuff that we all should practice," Dr. Mack says. "So washing hands, cleaning surfaces, trying to stay home when you're sick or ill so you don't spread infection. And right now, that's probably the biggest impact we can make on this."

Dr. Mack says health care providers around the country are working closely with the CDC to solve the mystery surrounding acute flaccid myelitis.

"I think the entire medical community is involved, is sharing information and wants to find out an answer as soon as possible," he says. "Unfortunately, it's going to take us more time."