Acute Flaccid Myelitis (AFM)

Peter O'Donnell Jr. Brain Institute

Appointment New Patient Appointment or 214-645-8300

At UT Southwestern Medical Center, our specialists in neurology, infectious diseases, physical medicine and rehabilitation, and nerve transplant surgery have expertise in accurately diagnosing and effectively treating acute flaccid myelitis (AFM).

AFM is a rare but serious condition that affects the spinal cord and can cause paralysis, primarily in children.

Using sophisticated diagnostic testing, we thoroughly evaluate patients to determine the cause of their symptoms, which can include muscle weakness and pain in the arms and legs, numbness, difficulty breathing, and difficulty swallowing or talking.

We provide the latest treatments, such as acute therapy and advanced nerve transfer surgery, to improve function and help patients get back to the activities they enjoy.

Expertise in Diagnosing and Treating Acute Flaccid Myelitis (AFM)

The spinal cord transmits information between the brain and the rest of the body via networks of nerves. To control motor function, neurons extend from the brain to the spinal cord (the upper motor neurons) and connect with a second set of neurons (the lower motor neurons), extending from the spinal cord to the muscle. The lower motor neurons initiate from the inside of the spinal cord, called the gray matter (also known as the anterior horn).

With acute flaccid myelitis, motor neurons within the gray matter of the spinal cord become damaged, causing muscle weakness and potentially paralysis of one or more limbs.

AFM is a type of acute flaccid paralysis, which has a variety of causes including several different viruses. Poliomyelitis (polio), caused by the poliovirus, was at one time the most common cause of AFM but has since been eradicated from the western hemisphere.

The Centers for Disease Control and Prevention (CDC) and UT Southwestern’s Dr. Benjamin Greenberg, an internationally recognized expert in treating rare autoimmune disorders of the central nervous system, have been studying AFM since 2014, when the first large outbreak occurred. These outbreaks have occurred every two years since then, usually in late summer through early fall. More than 90% of cases develop in children, but adults can get AFM too.

The Peter O'Donnell Jr. Brain Institute is ranked among the nation’s top hospitals for neurology and neurosurgery by U.S. News & World Report for 2020–21. Our experienced doctors and surgeons specialize in treating complex conditions affecting the brain and spinal cord, such as AFM.

At UT Southwestern, we take a team approach, working closely with other specialties here and at the Children’s Health Dallas Neurosciences Center to provide effective, compassionate care. Our team includes providers from neurology, neurosurgery, infectious disease, orthopaedics, pulmonology, pain management, physical therapy, and occupational therapy.

With years of expertise, we offer the most advanced health care options and personalized treatment plans for each person.

Causes of Acute Flaccid Myelitis (AFM)

The exact causes of AFM aren’t fully known, but research has shown that enterovirus D68, a respiratory virus, is the most likely cause for the alternating-year outbreaks.

More than 90% of people diagnosed with AFM initially had a mild illness or fever – symptoms that occur with viral infections – before they developed AFM. Several types of viruses have been linked with AFM, particularly when considering causes throughout the year.


Enteroviruses are a group of viruses that usually causes flu-like symptoms or gastrointestinal illness. Most people don’t get sick, or if they do, they experience mild symptoms such as fever, body aches, cough, and nasal congestion. In rare cases, enteroviruses can cause severe, life-threatening illnesses, usually in infants, young children, and people with weakened immune systems.

Diseases and symptoms caused by enteroviruses include:

  • Hand-foot-and-mouth disease
  • Heart infections such as myocarditis and pericarditis
  • Hemorrhagic conjunctivitis, a more severe form of pinkeye
  • Nervous system (brain and spinal cord) infections such as encephalitis and meningitis
  • Respiratory infections such as colds, pneumonia, and sinus infections
Mosquito-borne viruses

Some viruses are spread by the bite of infected mosquitos. Most people experience an itchy, inflamed bump where the mosquito bit them and don’t get sick. In rare cases, people can develop mild illnesses or severe, life-threatening diseases such as encephalitis or meningitis.

Mosquito-borne viruses associated with AFM include:

  • West Nile virus
  • Japanese encephalitis virus
  • Saint Louis encephalitis virus

It’s unclear why some people who have an infection develop AFM and others don’t. Current models suggest that the virus can spread from the lungs to a person’s spinal cord, infecting the lower motor neurons and causing death. This process might also draw out an immune response that can cause damage to the spinal cord.

AFM is often described as a “polio-like” illness, but in the U.S., AFM cases since 2014 have not been caused by poliovirus, a type of enterovirus. All the stool specimens from AFM patients that the CDC has received have tested negative for poliovirus.

Symptoms of Acute Flaccid Myelitis (AFM)

Symptoms of AFM develop quickly, often within just a few hours to days. It’s important for people who experience any of the disease’s symptoms to seek medical care immediately.

These symptoms are the most common and begin suddenly:

  • Muscle weakness in the arms and/or legs
  • Loss of muscle tone
  • Loss of reflexes

Other AFM symptoms include:

  • Facial weakness or drooping
  • Weakness in eye muscles, causing drooping eyelids or difficulty moving the eyes
  • Difficulty swallowing or talking
  • Pain in the neck, back, arms, or legs

Signs and symptoms that occur more rarely but should raise concern are:

  • Numbness or tingling
  • Stiffness in the neck
  • Inability to urinate

Other severe symptoms can occur:

  • Respiratory failure due to weakness in muscles that help with breathing
  • Serious nervous system problems such as changes in body temperature or blood pressure, which can be life threatening

Diagnosing Acute Flaccid Myelitis (AFM)

Diagnosing AFM can be difficult because its symptoms resemble those of other neurological conditions, such as transverse myelitis, vascular myelopathy, or Guillain-Barré syndrome.

It’s important for patients to see specialists in neurology and infectious disease with experience in diagnosing AFM for a thorough evaluation.

Our skilled specialists carefully evaluate each patient, beginning with a:

  • Discussion of symptoms
  • Review of medical history
  • Physical exam
  • Neurologic exam to assess muscle tone, strength, and reflexes

To confirm a diagnosis, we often use one or more additional tests, such as:

  • Cerebrospinal fluid (CSF) test: We take a small sample of CSF fluid, which surrounds and protects the brain and spinal cord, to check for signs of infection and rule out other causes. We first numb a small area on the lower back and then insert a narrow needle between two vertebrae (spine bones) to take the sample.
  • Electrodiagnostic exams: These tests measure nerve speed and muscle response to nerves.
    • Electromyogram: We insert a thin-needle electrode, about the size of those used in acupuncture, into a muscle. The needle records electrical activity as the patient moves and relaxes the muscle to show how well it responds to electrical signals from nerves.
    • Nerve conduction velocity study: We place electrodes (small, sticky pads) on the patient’s arm or leg. The electrodes send a mild electrical current through nerves in the muscle to show how fast the current traveled through nerves.
  • Magnetic resonance imaging (MRI) scans: Equipment that uses a powerful magnet and radio waves produces detailed images inside the body. We take MRI scans of the brain and spinal cord to check for possible damage to spinal cord gray matter.
  • Other lab tests: We can check for signs of infection and determine the type of infection using blood, saliva, nasopharyngeal swabs, or stool samples.

Treatments for Acute Flaccid Myelitis (AFM)

There is no specific treatment for AFM, and its long-term outcomes aren’t known. Some people completely recover, while others continue to have muscle weakness and symptoms for more than a year. Some therapies can help relieve symptoms and support recovery.

At UT Southwestern, our neurologists develop a customized treatment plan based on each patient’s specific symptoms and overall health. Treatment options include:

  • Anti-inflammatory therapies: These include corticosteroids, IVIG, and plasma exchange.
  • Pain management: Medications can help relieve pain caused by AFM.
  • Physical therapy: Our physical therapists guide patients through a variety of exercises to rebuild strength, balance, coordination, and other physical functions.
  • Occupational therapy: Our occupational therapists work with patients on specific skills, such as fine motor skills and sensory processing, that help with daily activities.
  • Oxygen therapy: Supplemental oxygen helps make breathing easier for people whose breathing muscles have become weak due to AFM.
  • Speech-language therapy: Our speech-language pathologists help patients regain fluency, swallowing, eating and drinking, and other face, head, and neck functions.
  • Nerve transfer surgery: Our highly skilled nerve surgeons repair damaged nerves by transferring nerves from a healthy area. These complex surgical procedures restore function to motor nerves to improve muscle movement.

Reducing the Risk of Acute Flaccid Myelitis (AFM)

There is no specific way to prevent AFM because its exact causes are unknown. Because viruses play a role in developing AFM, people can reduce their risk of getting or spreading viral infections by:

  • Washing hands often with soap and water
  • Avoiding touching the face with unwashed hands
  • Avoiding close contact with people who are sick
  • Cleaning and disinfecting surfaces that are frequently touched
  • Covering coughs and sneezes with a tissue or upper shirt sleeve, not hands
  • Staying home when sick
  • Avoiding sharing eating utensils, cups, straws, toothbrushes, cigarettes, and similar items
  • Reducing exposure to mosquitos by using mosquito repellants and wearing long sleeves and pants in areas with mosquitos

Additional Resources

Seigel Rare Neuroimmune Association: Get more information about AFM.