Acute Flaccid Myelitis in US Children

Update for Clinicians

James J. Sejvar, MD


January 20, 2015

Editorial Collaboration

Medscape &

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Hello. I'm Dr James Sejvar, a neurologist and epidemiologist with the Centers for Disease Control and Prevention (CDC). Since September 2014, CDC has been investigating reports of children across the United States who suddenly developed arm or leg weakness and had MRIs showing inflammation in the center of their spinal cords. We are now referring to this illness as "acute flaccid myelitis," and today I will discuss what we have learned so far in our investigation of these cases and will share a clinical resource that can be considered when managing patients with acute flaccid myelitis.

Every year, children in the United States develop neurologic illness with limb weakness. Such illnesses can result from a variety of causes, including viral infections, environmental toxins, genetic disorders, and Guillain-Barré syndrome, a neurologic disorder caused by an abnormal immune response. Although Guillain-Barré syndrome is the most frequent cause of this type of illness, it is important to consider, test for, and exclude these other possible causes of limb weakness. However, assessing limb weakness cases can often be challenging, so the underlying causes often remain unidentified.

In September 2014, public health officials in Colorado notified CDC about a cluster of nine children in a Denver hospital who suddenly developed an unexplained neurologic illness with limb weakness.[1] Given concerns that similar cases may be occurring in other parts of the United States, on September 26, CDC issued a health advisory, requesting that clinicians report patients who meet a specific case definition. This case definition includes patients aged 21 years or younger who suddenly developed focal limb weakness on or after August 1, 2014, and had an MRI showing a spinal cord lesion largely restricted to the center of the cord (the gray matter).

As of December 12, CDC has verified reports of 96 children in 34 states with acute flaccid myelitis that meets this case definition. The median age of the children was 8 years, ranging from 5 months to 20 years, and 61% were boys. Most of the children had fever or symptoms of respiratory illness before they developed the neurologic symptoms. The limb weakness for most of the affected children was distinctly asymmetrical, often resulting in paralysis of one limb. Of this group of children, 34% developed signs of impairment to the brain functions that control the head and facial muscles, and this produced a range of problems, such as double vision, sagging of the face, difficulty swallowing, and difficulty controlling the muscles that control speech. Of note, less than 10% of the children experienced other neurologic problems aside from the limb weakness, but a few children experienced such symptoms as confusion, changes in consciousness, and seizures. Furthermore, more than 75% of the children were previously healthy, and for those few with underlying illnesses, asthma was most commonly reported.[2]

Among the children receiving a lumbar puncture, 83% had results suggesting infection or inflammation of the brain or spinal cord, including a moderately increased white blood cell count and normal or mildly elevated protein.

Many questions have been raised about how these children are recovering after becoming acutely ill. Children who have been followed up after their acute illness have been observed for a median of 19 days. Among this group, 63% have reported some improvement in symptoms, whereas 36% showed no improvement. Only one of the affected children has fully recovered. Additional details about these findings can be found in a recently published Morbidity and Mortality Weekly Report.[2]

CDC continues collaborating with health departments, hospitals, and academic centers across the country to better understand the recent cases of acute flaccid myelitis, including potential causes, risk factors, and how often the illness occurs. Although the specific cause of this illness is still under investigation, there are general steps that would be prudent for clinicians to take. Clinicians should make sure that patients are up-to-date on all recommended vaccinations, because vaccines are essential to prevent many severe diseases, including polio and influenza. You should also remind patients that they can help prevent many viral infections by practicing general hygiene such as frequent handwashing, avoiding sick people, and disinfecting frequently touched surfaces.

Clinicians should be vigilant for patients who suddenly develop neurologic illness with limb weakness, and report all patients who meet CDC's case definition to their local or state health departments. Health departments should then report these cases to CDC using a patient summary form, available on CDC's website.

In response to requests from clinicians and public health officials for information on management and care of patients with acute flaccid myelitis, CDC in early November published interim considerations summarizing expert opinion about this topic. For further information or for questions about acute flaccid myelitis, please visit CDC's website or send an email to

Thank you for your attention.

Web Resources

CDC: Investigation of Acute Neurologic Illness with Focal Limb Weakness of Unknown Etiology in Children, Fall 2014

CDC Health Advisory Network: Acute Neurologic Illness with Focal Limb Weakness of Unknown Etiology in Children

James J. Sejvar, MD, is a neurologist and epidemiologist, and has been with the CDC since 2000. He serves as a staff neuroepidemiologist at CDC's National Center for Emerging and Zoonotic Infectious Diseases. His research interests focus on the epidemiology, clinical manifestations, and outcome of infections of the nervous system. In recent years he has focused much of his work on the clinical syndromes and outcomes associated with emerging viral encephalitides, including West Nile, Japanese encephalitis, and Nipah viruses; etiologies of acute flaccid paralysis worldwide; emerging human prion diseases; and neurologic adverse events following vaccinations.