Everything You Need to Know About Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is a rare neurological condition with serious consequences. It causes inflammation and damage to neurons in the spinal cord, and it can lead to paralysis. It mainly affects children under the age of 10 but can occur in anyone.

AFM has gained attention recently due to an alarming increase in cases in the last several years. In fact, there have been many reports of outbreaks around the world since 2012. Since 2014 there have been 682 confirmed cases in the U.S. And to date, there have been 3 confirmed cases in 2022.

But AFM is not a new disease. AFM is a type of acute flaccid paralysis (AFP) that the medical community has known about for a long time. AFP is a form of sudden weakness or paralysis that a virus usually causes. Polio is a well-known virus that can cause AFP due to inflammation of the spinal cord. Fortunately, there are no more polio cases in the U.S. and very few around the world.

AFM has similar symptoms to AFP, but the poliovirus doesn’t cause AFM. It’s usually associated with non-polio viruses. 

What are the symptoms of acute flaccid myelitis?

People with AFM often have a recent history of cold or flu-like symptoms. But they can start to develop concerning symptoms days to weeks after that. Some concerning symptoms of AFM may include:

• Sudden weakness in one or more limbs

• Loss of muscle tone (limbs may become limp and floppy)

• Weakness in the muscles of the face

• Droopy eyelids

• Difficulty moving the eyes

• Double vision

• Trouble swallowing

• Shortness of breath

• Slurred speech

• Pain in the arm, leg, neck, or back

• Headache

• Neck stiffness

• Fever

• Difficulty walking

• Constipation and urinary retention (in some cases)

• Numbness and tingling (less common)

When AFM is severe, it can cause:

• Respiratory failure (requiring intubation)

• Changes in body temperature, heart rate, and blood pressure

How serious is acute flaccid myelitis?

Weakness may progress from mild to severe within hours to days. The weakness can vary between slight weakness of one arm or leg to severe weakness of all four limbs. But it’s usually more common and severe in the arms. The neck, shoulders, hips, and trunk may also get weak. 

Read more like this

Explore these related articles, suggested for readers like you.

Does Rystiggo Cure Myasthenia Gravis? Plus Answers to 6 Other Rystiggo FAQs

Long COVID: Live Updates on the Latest in Research and Policy

How Common Is Guillain-Barré Syndrome, and How Do You Get It?

View more

It can become life-threatening when there’s weakness in the muscles that help you breathe. This can lead to respiratory failure and death. Early treatment is crucial. If you or your child have any of the symptoms of AFM, you should seek immediate medical attention. 

What causes acute flaccid myelitis? 

AFM is often linked to viral infections. The virus associated with AFM is usually an enterovirus. Some reports show a coxsackie virus as the cause of AFM. 

There have been AFM outbreaks in the U.S. every other year since 2014. These disease waves occur mostly in the late summer or fall, the time of the year when many viruses spread. Based on the pattern of cases every other year, experts expected a wave to occur in 2020, but it did not happen. The use of masks and handwashing likely reduced the spread of enteroviruses. 

How does acute flaccid myelitis spread?

Non-polio enteroviruses can lead to AFM. They commonly spread through respiratory fluids, but they can also spread in other ways. The most common way to get exposed is when someone with an infection coughs or sneezes near you. You can also get infected if you touch contaminated surfaces and then touch your eyes, mouth, or nose.

Not everyone who gets an enterovirus will get AFM. Even though enteroviruses are highly contagious, very few of those infected experience paralysis. 

How do you diagnose acute flaccid myelitis?

Your healthcare provider may use different tools to diagnose AFM, including:

• Physical exam is useful to check your overall health and symptoms. Your healthcare provider may do a neurological exam and check for loss of reflexes. 

• MRI helps to take a closer look at the specific areas of the spinal cord and brain stem that AFM affects.

• Laboratory blood tests check for signs of infection in the blood.

• Respiratory tests use samples through a nose or throat swab. 

• Stool samples look for evidence of infection in the stool.

• Lumbar puncture uses a needle to draw fluid from around your spinal cord to check for abnormalities.

• Nerve conduction studies and electromyography check how the nerves and muscles are working. It’s useful to rule out other neuromuscular conditions, like Guillain-Barré syndrome.  

How do you treat acute flaccid myelitis?

Most people with AFM need hospitalization, and more than half are admitted to the intensive care unit (ICU). About 30% of people need breathing support with intubation. But there’s no cure for AFM, and no specific treatment exists. 

Treatment options consist of medications, supportive measures, and rehabilitation. These can include:

• Intravenous immunoglobulins (to boost the immune system)

• Intravenous steroids 

• Plasmapheresis (plasma exchange) 

• Physical therapy and/or occupational therapy

• Nerve and muscle transfers

Supportive treatment for people with AFM may include:

• Alternative methods of feeding and hydration due to difficulty swallowing 

• Management of bowel or bladder problems

• Heart rate and blood pressure control

• Pain management 

Can you recover from acute flaccid myelitis?

After the initial recovery, people typically have lasting disability and need long-term rehabilitation. Early, intensive physical therapy helps address muscle weakness and mobility issues. Unfortunately, few people recover completely. Many people have remaining weakness and loss of muscle mass. Muscles with severe weakness are the least likely to recover. 

In general, after 1 year children may show some improvement in function, but they’re still weak. Long-term complications after AFM include:

• Weakness

• Chronic pain

• Chronic constipation

• Long-term need of a ventilator

• Dependence on artificial nutrition and hydration

• Joint dislocation and limited range of motion due to weakness

• Scoliosis

• Differences in limb length 

• Anxiety and depression

• Need for walking aids or wheelchairs

Can you prevent acute flaccid myelitis?

A virus often causes AFM. But everyone who gets sick with a virus won’t develop AFM. Experts aren’t sure why some people have AFM and others don’t. So the best method to prevent AFM is to avoid catching viruses. You can take steps to help decrease infections that may lead to AFM, including: 

• Washing your hands often

• Avoiding close contact with people who are sick

• Cleaning and disinfecting surfaces regularly

• Staying at home when you’re sick to protect others

Why trust our experts?

Written by:

Itza Rivera, MD

Dr. Rivera is a board-certified physical medicine and rehabilitation specialist. She completed her medical degree and residency training at the University of Puerto Rico School of Medicine, and her neuromuscular disorders subspecialty training at Northwestern University.

Edited by:

Karla Robinson, MD

Karla Robinson, MD, is a medical editor for GoodRx. She is a licensed, board-certified family physician with almost 20 years of experience in health through varied clinical, administrative, and educational roles.

Our editorial standards

Meet our experts