Acute Flaccid Myelitis – Symptoms and Causes

Acute flaccid myelitis (AFM) is an uncommon but serious neurologic condition that results from the inflammation and eventual paralysis of the spinal cord, primarily in children.

The condition can result in muscle weakness or even paralysis. Most children diagnosed with AFM have had a viral illness and then developed the symptoms weeks to months later, according to the U.S. Centers for Disease Control and Prevention (CDC).

About 90 percent of the estimated 412 children in the United States since 2014 have been either less than 2 years old or younger than 18 months old.

When to see a doctor

Individuals with AFM should see a health care provider if they develop sudden weakness in their arms or legs. Because the condition is so rare, it can often be misdiagnosed as other conditions.

Even when a diagnosis has been made, a health care provider can only provide symptomatic relief and do not have the ability to perform surgical procedures or take samples of the spinal fluid.

People with AFM who develop sudden weakness in their arms or legs should seek immediate medical attention. People with AFM who develop sudden weakness in their arms or legs should seek immediate medical attention.

In order to diagnose AFM, a health care provider may request to look at the medical history of a person who has sudden weakness in their arms or legs. This could include testing of the spinal fluid, a lumbar puncture, or a contrast CT scan.

Additionally, doctors may ask questions about the symptoms and activities that affected the person’s arms or legs.

They may also perform physical exams to see if muscles are tight or weak.

If a doctor notices certain muscle weakness or damage, they may order an MRI scan to look at the bones and tissues of the spinal cord.

Many doctors ask a person with AFM to return after 5 to 7 days to have additional tests completed, such as an MRI or another neurological exam.

Treatments for AFM

Doctors can treat AFM using a number of treatments. These include intravenous immunoglobulin, plasma exchange, and anesthetics for inflammation.

IV immunoglobulin and plasma exchange

In order to prevent severe damage to the nervous system, an injectable form of immunoglobulin called immunoglobulin (IVIG) is administered.

Immunoglobulin is often given to those who are immunosuppressed, and may help to decrease the inflammation.

Plasma exchange

People with AFM are often treated with blood plasma exchange. Plasma exchange helps remove the virus or other microorganisms in the body that could be causing the illness, which is not possible with immunoglobulin.

An example of this would be to take an intravenous (IV) infusion of a substance called plasmapheresis.

The amount of plasmapheresis that can be administered varies depending on the severity of the condition and the success of the treatments.

Anesthetics for inflammation

Anesthetics are used to relieve pain and inflammation from the inflammation and the area of the spinal cord that is affected.

People are usually given a local anesthetic first. The person then receives an injection of a general anesthetic, which is sent to the spinal cord through a catheter.

Benefits of these procedures are that they help reduce inflammation, improve blood flow, and stimulate the nerves that are affected. They also help the nerve cells to grow and form new connections.

Treating AFM with medical treatment

As AFM is considered an autoimmune disease, the treatments may only be temporary. However, long-term complications may develop if they do not work properly.

With a treatment, the illness is managed to the point that it is not causing any further harm. People with AFM are advised to avoid exertion, taking large amounts of medication, and if the body begins to recover, the treatments will have worked.

A person who develops sudden weakness or numbness in their arms or legs should see a doctor who can monitor the disease and help them make treatment decisions.

What is the outlook for people with AFM?

As long as a person is able to recognize the symptoms of AFM and get medical treatment, they can return to their normal life with their regular activities.

Although it is possible for AFM to return later, a person with AFM can often go home after a few days.

Complications from AFM can arise from a number of factors, including the types of fluids used during treatment and complications of surgery to remove the virus or other cause.

In the long term, people who experience AFM can develop problems with vision, motor skills, or breathing that could be permanent.

How is AFM diagnosed?

Early diagnosis is important to ensure a person has the best chance of recovery. Early diagnosis is important to ensure a person has the best chance of recovery.

Doctors typically diagnose AFM based on the symptoms, and people often have to undergo physical examination to look for specific signs.

A doctor will look for any blood vessels or nerves that appear altered, for signs of decreased ability to move the affected limbs, and for fatigue, which is a common side effect of the virus or injury.

Other common symptoms include difficulty with walking, loss of muscle mass, and tremors.

If a doctor suspects that AFM may be present, they may recommend a lumbar puncture to obtain a sample of spinal fluid to look for the virus.

Preliminary laboratory testing may show evidence of the virus in the spinal fluid, or these findings might be inconclusive.

Medical diagnosis will often come after an MRI, CT scan, or an ultrasound examination is performed to see if there are any abnormalities in the spine.

The diagnosis can be confirmed if people show clear signs of either:
  • paralysis of one or both legs
  • loss of nerve function in the limbs or one hand
  • decline in overall strength

MRI or CT imaging will usually show signs of inflammation in the spinal cord, in particular around the brain, that affects brain function. The virus is also associated with additional symptoms, such as weakness or lack of coordination.

A person with AFM should not attempt to operate a vehicle until they are fully recovered, because weakness or numbness might make it difficult to safely control the steering wheel.

A person with AFM may require surgery to remove the virus. The doctor will prescribe antiviral medications to reduce the risk of secondary complications.


Treating a person with AFM requires a comprehensive approach. These treatments include:

  1. warming the affected area to help stimulate the immune system to fight off the virus
  2. resting the person and minimizing stress
  3. medication to reduce swelling and pain
  4. laser therapy
  5. infusion with a specific blood product, such as mesna, to increase blood flow to the affected area

When to see a doctor

A person should seek immediate medical treatment if they develop any of the following symptoms of AFM:

  • trouble moving one or both arms
  • swallowing
  • loss of balance or coordination
  • loss of language skills or learning disabilities
  • numbness or tingling in one or both arms
  • difficulty with speech

In the first few days after the onset of symptoms, a person should also seek medical care if the symptoms do not go away or worsen:

  • fever
  • feverish signs, such as sweats, chills, and rash
  • very stiff muscles
  • feeling numb in one or both arms
  • confusion
  • Poor communication skills, such as difficulty speaking or understanding speech

There is no specific treatment for AFM, and many doctors do not recommend antiviral treatment for children.

Other Treatment Options

A doctor may suggest physiotherapy to help restore motor function. A doctor may suggest physiotherapy to help restore motor function.

Treatment for AFM varies between people. However, there are some recommended treatments, including:

Rest: the person needs to rest and not overexert themselves.

Medical management: If possible, doctors may prescribe drugs to help boost the immune system or reduce inflammation. Physical and occupational therapy may be recommended to help restore motor function.

Lifestyle changes: A person with AFM should minimize stress, if possible. Some people also find it helpful to take lots of deep breaths to relax their muscles.

Surgery: Some people may need surgery to remove the virus from the nervous system.

Recovery time

Recovery time for people with AFM varies. Anyone who has a fever, weakness, and one or both legs paralyzed should stay home from school or work until the fever subsides. If a child has only one arm or leg paralyzed, they are likely to be discharged from the hospital after 10–12 days.

Recovery time for the person with the loss of speech, and paralysis of the legs, may be longer, because they need therapy to regain their motor skills.

Some people may need to use a wheelchair for 3–6 months after AFM, and are at a higher risk for infection.

The child will also need to undergo physical and occupational therapy to learn how to control the wheelchair. A person may need help with everyday tasks for a few months following a severe respiratory infection or surgery.


It is not always possible to tell the cause of an illness, and doctors may not always know the course of the illness.

For some people, an illness like AFM can last months and cause a long recovery period.

The condition can be managed with medication and doctor’s visits, as well as physical and occupational therapy, to regain motor function.


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