Acute flaccid myelitis (AFM) is a rare neurological condition that can cause paralysis. It mainly occurs in children, but it can occur in adults, too.

As of writing, the Centers for Disease Control and Prevention (CDC) reports that there have been 13 confirmed cases of AFM in 2022. A total of 692 cases have been reported since the CDC began tracking the condition in 2014.

Below, we’ll go into more detail about AFM, including its symptoms and causes, as well as how doctors diagnose and treat it.

AFM is a rare neurological condition that impacts the nervous system. The most common symptom of AFM is limb weakness or paralysis that comes on suddenly.

People with AFM have areas of damage in the gray matter of the spinal cord that doctors can see using an MRI. The gray matter is important for things like muscle movement and gathering sensory information.

The damage that occurs due to AFM can be permanent and life threatening. This makes AFM a medical emergency. According to the CDC, 98% of people with AFM get hospital admittance, and 54% go to the intensive care unit (ICU).

Many people who develop AFM have an illness with fever about 1 to 10 days before any symptom onset. In addition to fever, other early symptoms can include a runny or stuffy nose, cough, or sore throat.

When the symptoms of AFM develop, they can include:

Fever and headache are also common symptoms of AFM.

AFM is a medical emergency. If you or a child experiences any of the symptoms above, call 911 or go to the emergency room immediately.

The exact cause of AFM is still unknown. However, an increase in the occurrence of AFM often links to a rise in illnesses due to the enterovirus EV-D68, which can cause a cold-like illness.

Indeed, many people who develop AFM report having an illness with fever before their symptoms come on. Most cases of AFM happen between August and November, a time of the year when many enteroviruses like EV-D68 circulate.

Enteroviruses are a diverse group of viruses. Several types of enteroviruses can cause the common cold, while others cause hand, foot, and mouth disease and polio.

We don’t know how exactly EV-D68 may cause AFM. It’s possible that the damage in the gray matter, which leads to the symptoms of AFM, could be due to the virus itself, the immune system’s response to the infection, or both.

Many people that get AFM are children. A 2020 research review noted that the average age at diagnosis is 6.3 years old. Less than 15% of people who develop AFM are adults.

Is AFM related to polio?

Polio and AFM cause very similar symptoms. Additionally, EV-D68 and poliovirus are both enteroviruses. However, experts have not detected poliovirus in samples from people with AFM.

According to the CDC, experts adopted the term “AFM” in 2014. It refers to a polio-like illness that has an unknown cause.

Since the introduction of the polio vaccine, experts effectively eliminated polio in the United States. In rare cases, travelers who’ve contracted it have brought it into the country.

The diagnosis of AFM can be tricky. Not only is it rare overall, but its symptoms can be similar to other neurological conditions, including, but not limited to:

Getting a thorough medical history is important. In addition to evaluating your symptoms, a doctor will note things like age, time of year, and if you have a recent history of illness with fever.

They can also do the following tests to help confirm a diagnosis of AFM:

  • Physical exam: During this exam, your doctor will look for areas with reduced muscle tone and weakness. They’ll also check your reflexes.
  • MRI scan: An MRI scan uses radio waves and strong magnets to create images of the inside of your body. Doctors can use it to look for signs of damage in your spinal cord.
  • Cerebrospinal fluid analysis: This test uses a sample of cerebrospinal fluid that a doctor collects using a lumbar puncture. It can help your doctor to look for signs of inflammation in your spinal cord.
  • Nerve conduction tests: These tests help check the signaling along your nerves. They can help a doctor figure out where along your nerves the weakness or paralysis starts.
  • Laboratory tests: Additional laboratory tests of blood, stool, or respiratory samples can aid your doctor in confirming or ruling out other health conditions as the causes of your symptoms.

There’s currently no standard treatment for AFM. Further, according to a 2020 research review, only observational studies on treatment outcomes for AFM are currently available. Experts need to perform further research to find effective treatments for the condition.

Right now, the treatment of AFM focuses on providing supportive care, such as:

It’s also possible that your doctor may choose to use other types of treatments as well, such as:

These treatments can help suppress the immune system to reduce an immune response that could be a factor in an underlying condition.

However, according to CDC guidance, there’s currently no evidence for or against the use of these treatments for AFM.

Since experts don’t yet know the exact cause of AFM, there’s currently no way to prevent it completely. It’s unclear why some people develop AFM and others do not.

However, since AFM links with a viral infection, there are some general steps that you can take to help reduce your risk, such as:

  • washing your hands frequently with soap and water
  • refraining from touching your eyes, mouth, or nose with unwashed hands
  • cleaning frequently touched surfaces in your home regularly, such as doorknobs and light switches
  • avoiding close physical contact with people who are sick

AFM can lead to permanent muscle weakness or paralysis. Although the outlook can vary by individual, generally speaking, a full recovery is uncommon.

For example, a small 2015 study involved a follow-up with 45 people who had experienced AFM. During an average follow-up of 9 months, 38% reported persistent limb weakness.

A small 2017 study involved a follow-up with 8 children a year after they had developed AFM. Although experts observed some improvements over time, 6 children had continuing problems with movement a year later.

Whether or not experts detect enterovirus in samples may also affect the outlook, according to a small 2020 study. Compared with patients who tested negative for enterovirus, those who tested positive had a higher likelihood of:

  • admission to the ICU
  • weakness or paralysis affecting all four limbs
  • bulbar palsy, which can cause symptoms like trouble breathing and difficulty swallowing or speaking
  • problems with bowel or bladder function
  • cardiovascular instability, which can include atypical heart rate or blood pressure

Doctors will likely recommend physical therapy, occupational therapy, or both if you’ve had AFM. Physical therapy focuses on improving strength and flexibility, while occupational therapy helps you to learn ways to do daily activities.

AFM is a rare neurological condition that can lead to permanent muscle weakness or paralysis. It mainly affects children, but adults can develop the condition as well.

Experts generally believe that a viral infection may trigger AFM, specifically with the enterovirus EV-D68. However, why some people develop AFM while others do not is currently unclear.

AFM is a medical emergency. If you or a child experiences limb weakness or paralysis that comes on suddenly, get emergency medical care.