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Acute Flaccid Myelitis

What is acute flaccid myelitis (AFM)?

Acute flaccid myelitis (AFM) is a sudden onset of paralysis in the spinal cord. Acute means quick or fast onset. Flaccid is a decrease or lack of muscle movement where the affected body part becomes floppy or without muscle tone and with diminished reflexes. Myelitis is an inflammatory change in myelin which is the covering that supports nerves. -itis means inflammation. AFM targets the spinal cord which carries messages for sensation and movement to and from the brain throughout the body. This makes feeling and movement diminished.

Myelin is an important substance that coats nerve cells. When messages are conducted through nerves back and forth from the brain to the body and from the body to the brain, the message impulse travels along the nerve. Myelin is a white fatty substance that helps to hold the message within the nerve. When myelin is not present or damaged in some way, the impulse message cannot get through correctly.

In acute flaccid myelitis, myelin is attacked and destroyed for some unknown reason. At first, the myelin becomes damaged, so message transmission is not as effective as it should be. Eventually, the myelin can become destroyed which then affects the nerve directly. Nerve impulses can stop. In acute flaccid myelitis, a quick onset of damage occurs to the myelin which interrupts the messages nerves are attempting to send throughout the body.

In the spinal cord, lower motor neurons (LMN)(nerves) in the gray matter make the connection from upper motor neurons to skeletal muscles in the body. LMNs transfer messages between the brain and the body. This is how messages are transmitted in the central nervous system. AFM affects LMNs, with the result of flaccid (limp) muscle weakness, muscular atrophy (wasting), fasciculation (single nerve twitches), and hyporeflexia (poorly responding reflexes).

AFM is considered a non-polio virus. This means the results appear like a polio episode, but AFM is not caused from the polio virus. Polio is contagious while AFM is not.

Causes of AFM

AFM is thought to be caused by viral infections, environmental toxins and/or genetic disorders.

Viral infections: Enterovirus is virus that affects the gastrointestinal tract (stomach and bowel) of the body. A particular strain of this virus, enterovirus D68 (EV-D68), was identified in 1962 in California as a non-polio virus. It was very rare until 2014, when 1,395 cases of this virus were reported in the U.S. and 59 cases were reported in Japan. Why this outbreak occurred is unknown. However, sporadic cases have been appearing since this outbreak.

Mild symptoms of EV-D68 are much like any flu, runny nose, sneezing, cough, and muscle aches. Severe symptoms are wheezing and difficulty breathing. It is spread through air droplets or by touching something that someone with EV-D68 has touched. It is contagious any time of the year but peaks in spring and fall. Children and teens are much more likely to have effects of the virus because they have less built up immunities than adults, but adults can become ill with EV-D68 as well. Hand hygiene and covering your mouth and nose when sneezing or coughing reduces the spread of this virus.

Environmental toxins: Toxins in our surroundings have been associated with AFM. Snakebite toxin has been documented as one unusual source as well.

Genetic disorders: Diseases that are connected through family inheritance have been related to AFM. One example is Familial Hypokalemic (low potassium) Periodic Paralysis which is a rare autosomal dominant (an abnormal gene from one parent) neuromuscular disease that includes attacks of flaccid paralysis with recurring low potassium.

It has been thought that AFM is a variation of diseases such as Transverse Myelitis (TM) or Guillain Barré Syndrome (GBS). Internal body inflammation could be the source of damage to myelin. Others think that the cause could be trauma or disease of the muscles.

Symptoms of AFM

Symptoms of AFM are the result of the effects on the lower motor neurons in the spinal cord.

  • Sudden onset of arm or leg weakness and loss of muscle tone and reflexes
  • Difficulty moving the eyes or drooping eye lids
  • Facial droop or weakness on one or both sides
  • Difficulty with swallowing or slurred speech
  • An inability to urinate
  • Some people develop pain
  • Respiratory failure (if respiratory muscles are affected)

As with all diseases of the spinal cord, only the nerves affected will result in symptoms. Therefore, a person could have all, some or a combination of some of the symptoms listed above. Cases of AFM can look completely different from one another.

Diagnosing acute flaccid myelitis

The diagnosis of AFM can be complicated as the symptoms mimic those of other diseases such as Guillain Barré and Transverse Myelitis. There is not a definitive test but rather the history and clinical picture is used for diagnosis once other diseases have been ruled out.

To begin the diagnostic process, the physician will do a complete physical and neurological examination. This will include an assessment of all muscle groups, joints, sensation and reflexes. Muscles are examined by asking the individual to move body parts against gravity and with gravity reduced and eliminated. Sensation is tested with a cotton swab and pin point for gross and fine sensation. Reflexes are assessed by applying a sharp and quick pressure or tap with a reflex hammer to the areas of the body where a tendon attaches to the bone. The typical response of the reflexes in AFM are reduced or diminished.

Imaging studies include an MRI to assess the brain and spinal cord within the body. Signs of swelling or demyelination might be noted in AFM.

A lumbar puncture or spinal tap to remove a small amount of cerebral spinal fluid is performed sterilely by inserting a needle into the space between fourth and fifth lumbar space in the back. A small amount of fluid is removed and sent to the lab for analysis for coxsackievirus A16, EV-A71, and EV-D68 and other abnormal balances in cerebral spinal fluid. This is also important for ruling out other neurological diseases.

Nerve conduction testing is completed to note the timing of impulse message transmission along selected nerves. Time delays can indicate AFM.

Treatment of acute flaccid myelitis

There is no formal treatment protocol for AFM. Instead, treatment is based on individual symptoms of each case.

Different medical treatments including cortical steroids, plasmapheresis, intravenous immunoglobulin, fluoxetine, antiviral medications, interferon and other immunosuppressant drugs have been attempted for treatment of AFM without evidence of success. However, these treatments may be attempted depending on individual situations.

The Centers for Disease Control and Prevention has issued a document,
Acute Flaccid Myelitis: Interim Considerations for Clinical Management, as a guideline for treatment.


AFM can affect breathing if any part of the respiratory system is affected. It is necessary to provide breathing assistance as needed.

Breathing is a needed process where the diaphragm, abdominal muscles and intercostal muscles (tiny muscles between the ribs) work together to draw air from the environment into the lungs. The vagus nerve does the yeoman’s work to pull the diaphragm down which then causes the lungs to pull downward in the body causing air to be drawn into them. The abdominal muscles assist with pulling the lungs downward. The intercostal muscles pull the ribs outwardly in the chest to assist.

When the three muscle groups relax, the tension in the lungs is reduced and air just naturally flows out as opposed to being pushed out. This becomes an important distinction when mechanical ventilation is needed. In inspiration, air is actively drawn into the lungs by three working sets of muscles but in expiration, air is expelled by relaxation of the lungs, not actively pushed out by the muscles. In breathing, air is forced or drawn in as the lungs are physically expanded and dilated but air is expelled when the lungs relax and return to their natural shape and size.

All three muscle groups have their job to do. The diaphragm is essential for breathing. Sometimes, the abdominals or intercostal muscles don’t assist as well as they should. Individuals might be able to adapt to this but typically, all three need to be working together to achieve a good breath.

Depending on the individual situation, there are treatments that can help individuals breathe. Non-Invasive Ventilation (NIV) is used for acute respiratory dysfunction (ARD) or acute respiratory failure (ARF) but can also be used for long term breathing.

Some examples of NIV are if a person is not getting enough oxygen without a structural problem in the body, oxygen might be provided through a tube by the nose. This can be accomplished by using low flow or high flow nasal cannula. A nasal cannula is the two-pronged tube that releases oxygen just barely into the nose. When using this technique, the mouth should be able to be closed most of the time to get the full effect of the oxygen.

Continuous Positive Airway Pressure (CPAP) is an external breathing device for NIV that fits over the nose and sometimes also the mouth. There are several versions of this treatment including nasal Continuous Positive Airway Pressure (nCPAP) and Bubble Continuous Positive Airway Pressure (BCPAP). Each have differences but in general they gently blow in condensed air to keep the nose, airway and lungs open.

Other types of NIV might include Nasal Intermittent Positive Pressure Ventilation (NIPPV) which uses a ventilator to provide intermittent breaths at full inspiratory pressure through the nose. Bilevel Nasal Positive Airway Pressure (BiPAP) uses lower pressure, longer inspirations and sighs (occasional deeper breaths). These machines follow a typical breathing pattern of taking in air then resting to allow air containing carbon dioxide to flow out.

Mechanical Ventilation (MV) is when a tube is placed in the mouth or throat to accommodate breathing. This is considered invasive because the breathing tube is placed inside the body. A tracheostomy or a surgical incision at the front base of the neck is made to make the effort of breathing easier if the ventilation will be long term.

Rehabilitation for acute flaccid myelitis

Recovery from AFM is a process. There is no curative treatment found to date. Recovery is based on treating symptoms.
A physician that specializes in physical medicine and rehabilitation (called a physiatrist), a neurologist, a pediatrician or a combination of specialists will coordinate medical needs. A urologist might also be consulted for bladder management. There might be a combination of specialists who will work together to coordinate care.

Rehabilitation will include physical and occupational therapy to provide input to those nerves and muscles that are underpowered. Physical therapy directs their efforts towards gross movement such as sitting, standing and walking. Occupational therapy focuses on fine movement of hands and fingers, as well as activities of daily living, dressing, bathing and feeding. Avoiding further complications is also in their plan. They advance therapy as the individual improves.
Respiratory therapy will assist with ventilation needs (both noninvasive and with mechanical ventilation). They can provide direction for increasing ventilation as well as weaning when no longer needed.

Speech therapy will be involved if there are oral motor deficits. This will help with controlling swallowing and avoiding aspiration or swallowing of fluid and foods into the lungs. The Speech and Language Pathologist will assist with speaking as needed.

Registered nurses will carry out the therapist’s recommendations throughout the day. They will plan bladder, bowel and skin care management as well as helping transition to home.

The hospital case manager will be in contact with your insurance case manager to coordinate needed care. Once home, you will work directly with the insurance case manager.

All these professionals will work together to coordinate the needed care and to encourage recovery. A few individuals will have recovery, others might not see much improvement. There is no indication about how much people will recover.

Prevention of acute flaccid myelitis

Since the cause of AFM is unknown, prevention measures for this disease are not clear. Some general prevention techniques are important to be followed by everyone to avoid many diseases. These include:

  • Washing hands often with warm water and soap, using friction
  • Covering your mouth and nose when sneezing or coughing by doing so into the inside of your elbow
  • Staying home when ill as well as avoiding people who are ill.
  • Avoid touching your face, eyes, nose or mouth with your hands
  • Washing doorknobs, toys, and surfaces in your home and car
  • Keeping up with immunizations


The causes and treatments for AFM are actively being researched. AFM has been diagnosed for several years but in extremely rare cases. Since 2014, the number of cases has been growing quickly. Because this disease is so new, scientists are focusing on isolating the cause. Many studies are being conducted to find out more about the etiology (origin) of the condition. Once this is discovered, treatments will be developed or used from similarly related diseases.

The Centers for Disease Control and Prevention is reviewing possible cases from the past to make connections. They have a campaign for healthcare professionals to report new cases for review by contacting the CDC at [email protected]

A clinical trial is underway to collect information about AFM in individuals ages 0-18. The study is titled CAPTURE: Collaborative Assessment of Pediatric Transverse Myelitis; Understand, Reveal, Educate. You can submit information here.

The United States National Library of Medicine organizes a public site to research any medical diagnosis that has funding from the US government. You can volunteer for studies but also read about the outcomes of funded studies. Log on to and search for the diagnostic category of interest (acute flaccid myelitis).

Ongoing studies for improving the outcomes of paralysis are being conducted in a variety of focus areas. These involve secondary conditions for bladder, bowel and skin care.

There are efforts being made to develop national guidelines for pediatric ventilation. Many professionals who specialize in pediatrics have developed their own effective treatment plans, however, consensus across the country has been difficult because there are relatively few pediatric aged individuals who require long term mechanical ventilation, a variety of ages, differences in body development and mental development and a wide range of diagnoses. This makes finding like groups a challenge for protocol development since the populations are small in number for wide range testing.

Facts and figures

  • Less than 1-2 children out of one million will be affected by AFM. AFM has been peaking in the US every two years since 2014.
  • Thousands of individuals have viruses every year. Why some people develop AFM is unknown.
  • 90% of individuals who develop AFM had a respiratory infection first.
  • Over 90% of AFM cases are in children.
  • AFM is not caused by the polio virus.


If you are looking for more information on acute flaccid myelitis or have a specific question, our Information Specialists are available business weekdays, Monday through Friday, toll-free at 800-539-7309 from 9:00 am to 8:00 pm ET.

Additionally, the Reeve Foundation maintains a fact sheet on acute flaccid myelitis with resources from trusted Reeve Foundation sources. Check out our repository of fact sheets on hundreds of topics ranging from state resources to secondary complications of paralysis.

We encourage you to also reach out to acute flaccid myelitis support groups and organizations, including:

Further reading


Messacar K, Schreiner TL, Van Haren K, Yang M, Glaser CA, Tyler KL, Dominguez SR. Acute flaccid myelitis: A clinical review of US cases 2012-2015. Ann Neurol. 2016 Sep;80(3):326-38. doi: 10.1002/ana.24730. Epub 2016 Aug 4.

Morens DM, Folkers GK, Fauci AS. Acute Flaccid Myelitis: Something Old and Something New. MBio. 2019 Apr 2;10(2). pii: e00521-19. doi: 10.1128/mBio.00521-19.

Causes of AFM section

Hatayama K, Goto S, Yashiro M, Mori H, Fujimoto T, Hanaoka N, Tanaka-Taya K, Zuzan T, Inoue M. Acute flaccid myelitis associated with enterovirus D68 in a non-epidemic setting. IDCases. 2019 May 3;17:e00549. doi: 10.1016/j.idcr.2019.e00549. eCollection 2019.

Rupesh Kaushik, Parampreet S. Kharbanda, Ashish Bhalla, Roopa Rajan, and Sudesh Prabhakar. Acute Flaccid paralysis in adults: Our experience. J Emerg Trauma Shock. 2014 Jul-Sep; 7(3): 149–154.doi: 10.4103/0974-2700.136847

Symptoms of AFM section

Nelson GR, Bonkowsky JL, Doll E, Green M, Hedlund GL, Moore KR, Bale JF Jr. Recognition and Management of Acute Flaccid Myelitis in Children. Pediatr Neurol. 2016 Feb;55:17-21. doi: 10.1016/j.pediatrneurol.2015.10.007. Epub 2015 Oct 20.

Diagnosing AFM section

Sarah E. Hopkins, MD, MSPH, Matthew J. Elrick, MD, PhD, Kevin Messacar, MD. Acute Flaccid Myelitis—Keys to Diagnosis, Questions About Treatment, and Future Directions. JAMA Pediatr. 2019;173(2):117-118. doi:10.1001/jamapediatrics.2018.4896

Andersen EW, Kornberg AJ, Freeman JL, Leventer RJ, Ryan MM. Acute flaccid myelitis in childhood: a retrospective cohort study. Eur J Neurol. 2017 Aug;24(8):1077-1083. doi: 10.1111/ene.13345. Epub 2017 Jun 22.

Treatment of AFM section

Hopkins SE. Acute Flaccid Myelitis: Etiologic Challenges, Diagnostic and Management Considerations. Curr Treat Options Neurol. 2017 Nov 28;19(12):48. doi: 10.1007/s11940-017-0480-3.

Tyler KL. Rationale for the evaluation of fluoxetine in the treatment of enterovirus D68-associated acute flaccid myelitis. JAMA Neurol. 2015 May;72(5):493-4. doi: 10.1001/jamaneurol.2014.4625

Breathing section

Fatemi Y, Chakraborty R. Acute Flaccid Myelitis: A Clinical Overview for 2019. Mayo Clin Proc. 2019 May;94(5):875-881. doi: 10.1016/j.mayocp.2019.03.011

Rehabilitation for AFM section

Nath RK, Somasundaram C. Functional Improvement of Upper and Lower Extremity After Decompression and Neurolysis and Nerve Transfer in a Pediatric Patient with Acute Flaccid Myelitis. Am J Case Rep. 2019 May 10;20:668-673. doi: 10.12659/AJCR.915235.

Martin JA, Messacar K, Yang ML, Maloney JA, Lindwall J, Carry T, Kenyon P, Sillau SH, Oleszek J, Tyler KL, Dominguez SR, Schreiner TL. Outcomes of Colorado children with acute flaccid myelitis at 1 year. Neurology. 2017 Jul 11;89(2):129-137. doi: 10.1212/WNL.0000000000004081

Research section

Aliabadi N, Messacar K, Pastula DM, Robinson CC, Leshem E, Sejvar JJ, Nix WA, Oberste MS, Feikin DR, Dominguez SR. Enterovirus D68 Infection in Children with Acute Flaccid Myelitis, Colorado, USA, 2014. Emerg Infect Dis. 2016 Aug;22(8):1387-94. doi: 10.3201/eid2208.151949.

Greninger AL, Naccache SN, Messacar K, Clayton A, Yu G, Somasekar S, Federman S, Stryke D, Anderson C, Yagi S, Messenger S, Wadford D, Xia D, Watt JP, Van Haren K, Dominguez SR, Glaser C, Aldrovandi G, Chiu CY. A novel outbreak enterovirus D68 strain associated with acute flaccid myelitis cases in the USA (2012-14): a retrospective cohort study. Lancet Infect Dis. 2015 Jun;15(6):671-82. doi: 10.1016/S1473-3099(15)70093-9. Epub 2015 Mar 31.

Facts and Figures section

Center for Disease Control

The National Paralysis Resource Center website is supported by the Administration for Community Living (ACL), U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $9,447,037 with 100 percent funding by ACL/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by ACL/HHS, or the U.S. Government.