What Parents Need to Know About Acute Flaccid Myelitis (AFM)
Nov 02, 2018
Acute flaccid myelitis (AFM) is a rare condition that has received much attention recently. The reports are scary, with most cases involving young healthy children who suffer from muscle weakness or paralysis that can last a long time.
What is AFM?
Let’s break down the words of this disorder. Acute means a condition begins abruptly. Flaccid refers to muscle weakness or paralysis, and myelitis describes inflammation within the spinal cord.
In AFM, inflammation affects the gray matter of the spinal cord, which includes nerve cells that control muscles of the face, trunk and extremities. Inflammation prevents these cells from working properly. The location of symptoms depends on the region of spinal cord involvement and can range from facial drooping to weakness and paralysis of arms or legs. If the disorder affects breathing muscles, it can be life threatening.
Although it comes on abruptly, AFM tends to last a long time. In some cases, symptoms improve, but for others the weakness or paralysis is permanent. There is no way to predict which patients will improve and which ones will not.
What causes AFM?
The condition is similar to paralytic polio (poliomyelitis), which results from infection with a type of enterovirus called poliovirus. Frequency of AFM began to increase in 2014 during a national outbreak of another enterovirus called enterovirus D68. Given these connections, it would make sense that enterovirus D68 is responsible for the current increase in AFM cases. The problem is that investigators have not found evidence of enterovirus D68 infection in many children with AFM.
It is possible the virus escapes detection or the immune system (in response to the virus) causes the damage after the infection has cleared. West Nile virus, adenovirus and environmental toxins are other possible culprits, but again, there isn’t a clear link.
One barrier in establishing a cause is that AFM is rare with an incidence of less than 1 case per 1 million people and fewer than 500 cases in the past four years. Compare these numbers to polio, which affected thousands of children each year in the first half of the twentieth century. Greater numbers help scientists determine the cause. To make matters more difficult, there may be more than one cause of AFM, and genetics may play a role, making AFM more likely in some folks and less likely in others.
How is AFM treated?
There is no cure for AFM. Treatment is largely supportive with a primary goal of maintaining function through physical therapy. Sometimes this helps and sometimes it doesn’t. When breathing muscles are affected, oxygen therapy and mechanical ventilation may be necessary. There isn’t enough experience with this disorder to predict long-term outcomes, but if polio is an accurate indicator, we can expect the weakness and paralysis to last a lifetime in many patients.
Can we prevent AFM?
In order to stop AFM like we stopped polio, scientists need to establish a definite cause. They are working hard to do this. In the meantime, we should remember AFM is rare, and whatever is causing this weakness and paralysis is affecting far fewer children than poliovirus of decades past.
Dr Mike Patrick is an Assistant Professor of Pediatrics at the Ohio State University College of Medicine and Medical Director of Interactive Media for Nationwide Children's Hospital. Since 2006, he has hosted the award-winning PediaCast, a pediatric podcast for parents. Dr Mike also produces a national podcast for healthcare providers—PediaCast CME, which explores general pediatric and faculty development topics and offers free AMA PRA Category 1 Credit™ to listeners.
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