COMMENTARY

Acute Flaccid Myelitis Tends to Spike in Even-Numbered Years. This Summer Could Bring Another Surge

Sarah E. Hopkins, MD, MSPH

Disclosures

May 08, 2020

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This transcript has been edited for clarity.

I am Sarah Hopkins. I'm an assistant professor of clinical neurology and an attending neurologist at the Children's Hospital of Philadelphia and the University of Pennsylvania, Perelman School of Medicine.

Today I'm going to talk about acute flaccid myelitis (AFM) — its characteristics, diagnostic testing, early management, complications, and outstanding questions that we're hoping to address in the upcoming year.

Characteristics

AFM is the acute onset of flaccid weakness that results from damage to the longitudinal gray matter in the spinal cord. [The Centers for Disease Control and Prevention (CDC) began tracking AFM in 2014] and since then, we've seen an increase in cases every 2 years in the United States. These children typically present in the setting of a current or very recent febrile illness, usually with upper respiratory infection symptoms, although sometimes with gastrointestinal symptoms.

Hallmarks include proximal weakness in the shoulders or hips. This manifests as weakness with shoulder elevation; children can't give a high five, can't raise both their arms.

Hip strength is also compromised. To assess hip strength, you can ask the child to get up from a seated position on the floor.

The child often has pain in the affected extremity and sometimes subtle sensory abnormalities as well.

Diagnostic Testing

Diagnostic testing includes MRI of the spinal cord to look for gray matter abnormalities that would be classic for AFM. Abnormalities often involve the anterior horn cells.

You also will want to identify the virus that may be associated with this presentation. We recommend testing for respiratory viruses, including an enteroviral polymerase chain reaction (PCR) of the patient's respiratory secretions, specifically a nasal pharyngeal swab. Typically, we also consider a spinal tap to look for CSF pleocytosis.

Complications

One reason for identifying AFM early is that once these children start to develop weakness, it can progress over hours to days and cause respiratory compromise. Especially in patients with upper extremity involvement, and as with any lesion involving the upper cervical spine, you want to watch closely, observing the patient in the hospital to be sure their breathing is not impaired.

Management

Right now we don't have a medicine that clearly alters the course of AFM. A mouse model demonstrated that intravenous immunoglobulin (IVIG) was helpful if given early. Because of this, we are trying to give IVIG therapy as early as possible. Again, this is not a proven treatment. We don't currently have a proven treatment.

If we see a lot of spinal cord swelling, we consider giving steroids, and some also consider giving plasma exchange.

Unanswered Questions

We know that some of these patients have had enterovirus infections. The one that's the most suspect is enterovirus D68, which was circulating at the time of the initial emergence of AFM in 2014 and has been associated with some of these cases. Another one that may be a culprit for some cases is enterovirus A71.

There's still a lot to be learned to firm up this connection so that we can consider what additional therapies would be appropriate. To that end, upcoming studies include a National Institutes of Health AFM natural history study, which is a multisite study that will be conducted throughout the United States.

Sarah E. Hopkins, MD, MSPH, is a pediatric neurologist and section head for Multiple Sclerosis and Neuroinflammatory Disorders at Children's Hospital of Philadelphia. Her research includes funding from the Centers for Disease Control and Prevention related to AFM surveillance.

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