Acute Flaccid Myelitis

Recent news reports described children affected with the sudden onset of Acute Flaccid Myelitis (AFM), a syndrome that produces polio-like paralysis. Let’s take a closer look at what we know about AFM.

Is it serious?

Acute Flaccid Myelitis (AFM) is a rare, but serious condition of the nervous system that affects the area of the spinal cord called gray matter and causes muscles and reflexes to become weak. It is not a new syndrome, but the number of cases reported to the Centers for Disease Control and Prevention (CDC) has increased since CDC began to track it in 2014.

It is rare and it is not polio

The risk of getting AFM varies by age and year. Young children seem most susceptible. Nonetheless, CDC estimates less than one to two in a million children in the United States will have AFM each year. Since 2014, there have been 460 confirmed cases throughout the United States. In that same period, more than 90% of AFM patients had a mild respiratory illness or fever consistent with a viral infection before they developed AFM. Also, CDC tests of stool samples from AFM patients showed no sign of poliovirus.

It looks like paralysis

Most people who get AFM will have a sudden onset of arm or leg weakness and loss of muscle tone and reflexes. Some will also have facial droop or weakness, eyelid droop, difficulty moving the eyes, difficulty swallowing or slurred speech. Rarely, people with AFM have numbness, tingling or pain in their arms and legs. Some have trouble passing urine.

The most severe symptom of AFM is respiratory failure that can occur when the muscles involved with breathing become weak. This can require urgent ventilator support (breathing machine).

It is hard to diagnose

AFM is diagnosed by examining a patient’s nervous system in combination with reviewing pictures of the spinal cord. The doctor will look for signs of weakness, poor muscle tone and decreased reflexes and do an MRI (magnetic resonance imaging) to look at a patient’s brain and spinal cord. In addition, the doctor may request lab tests on the cerebrospinal fluid (the fluid around the brain and spinal cord), and check nerve conduction to measure the impulse sent along a nerve fiber, and response. Tests are done as soon as possible after the patient develops symptoms.

AFM can be difficult to diagnose because it shares many of the same symptoms as other neurologic diseases, including transverse myelitis and Guillain-Barre syndrome.

Its causes are not well understood

Certain viruses are known to cause AFM, including enteroviruses such as poliovirus, enterovirus A71 and West Nile virus. But none of the cases since 2014 are linked to polio and in all except four cases confirmed by the CDC since 2014, no pathogen (germ) was found in the patient’s spinal fluid to confirm any cause. The CDC said sometimes the body clears the pathogen from the spinal fluid, or the pathogen hides in tissues or triggers an immune response that causes damage to the spinal cord.

It has no specific treatment

Doctors who specialize in brain and spinal cord illnesses will recommend case-by-case intervention that may include physical or occupational therapy to address arm or leg weakness.

Is it difficult to prevent?

There is no specific action to take to prevent AFM, but because certain enteroviruses are known to cause AFM, people are urged to protect themselves and their children with these steps:

  • Get vaccinated against poliovirus. The vaccine protects against poliovirus, but not against other viruses that may cause AFM.
  • Because mosquitoes can carry West Nile virus, protect against bites by using mosquito repellent, staying indoors at dusk and dawn when bites are more common, and removing standing water were mosquitoes can breed.
  • Wash hands often with soap and water, avoid close contact with people who are sick, and clean and disinfect frequently touched surfaces, including toys.

Please remember - AFM is a difficult disease to diagnose. Please contact your health care provider immediately if you or loved one has any symptoms of AFM. As with many diseases, early detection is critical.