Acute flaccid myelitis is a rare condition that affects the nervous system. Inflammation of the gray matter in the spinal cord leads to muscle weakness and paralysis.
Acute flaccid myelitis (AFM) is usually caused by infection with a virus. While AFM is rare, there has been a slight increase in cases of AFM since 2014. Most new cases have occurred in children or young adults.
AFM usually occurs after a cold, fever, or gastrointestinal illness.
Different kinds of viruses may be the cause of AFM. These include:
It is unclear why certain viruses trigger AFM, or why some people develop the condition and others don't.
Environmental toxins also can cause AFM. In many cases, a cause is never found.
A fever or a respiratory illness is often present before weakness and other symptoms begin.
AFM symptoms often start with sudden muscle weakness and loss of reflexes in an arm or leg. Symptoms may progress rapidly over a few hours to days. Other symptoms may include:
Some people may have:
Severe symptoms include:
Your health care provider will take your medical history and vaccination history to know if you are up-to-date with your polio vaccines. Unvaccinated individuals who are exposed to poliovirus are at higher risk for acute flaccid myelitis. Your provider also may want to know if within the last 4 weeks you have:
Your provider will do a physical exam. Tests that may be done include:
Your provider also may take stool, blood, and saliva samples to test.
There is no specific treatment for AFM. You may be referred to a doctor specializing in disorders of the nerves and nervous system (neurologist). The doctor will likely treat your symptoms.
A number of medicines and treatments that work on the immune system have been tried but have not been found to help.
You may need physical therapy to help restore muscle function.
The long-term outlook of AFM is not known.
Complications of AFM include:
Contact your provider right away if you or your child have:
There is no clear way to prevent AFM. Having a polio vaccine may help reduce the risk of AFM related to the poliovirus.
Take these steps to help avoid viral infection:
To learn more and get recent updates, go to the CDC webpage about acute flaccid myelitis at www.cdc.gov/acute-flaccid-myelitis/index.html.
Reviewed By: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.