How to Recognize AFM

The term acute flaccid myelitis was created in fall of 2014 to describe patients with sudden onset of acute flaccid limb weakness without a known cause and with lesions in gray matter of the spinal cord. There can be some white matter involvement. Most cases are in children.

Viral causes include:

• Non-polio enteroviruses (EV-D68, EV-A71)
• Flaviviruses (West Nile virus, Japanese encephalitis virus)
• Herpesviruses
• Adenoviruses

Clinical presentation is similar to poliomyelitis, but poliovirus has not been detected in any specimens from patients with AFM.

AFM Clinical Presentation

Most patients had preceding febrile illness 1–2 weeks before onset of acute flaccid limb weakness.

• Frequently respiratory or gastrointestinal illness (GI) with symptoms of fever, rhinorrhea, cough, vomiting or diarrhea.
• Onset of weakness is rapid, within hours to a few days.
• Weakness is in one or more limbs and is more proximal than distal.
• Loss of muscle tone and reflexes in the affected limb(s).

Cranial nerve abnormalities can be present:

• Facial or eyelid droop
• Difficulty swallowing or speaking
• Hoarse or weak cry

Some patients might complain about stiff neck, headache, or pain in the affected limb(s).

In uncommon cases, people can also have numbness or tingling.

The most severe symptoms of AFM are:

• Respiratory failure, requiring mechanical ventilation
• Serious neurologic complications such as body temperature changes and blood pressure instability that could be life threatening

Differential Diagnosis of Flaccid Limb Weakness

AFM can resemble:

• Synovitis
• Neuritis
• Limb injury
• Guillain-Barre syndrome (GBS)
• Transverse myelitis
• Stroke, including spinal stroke
• Tumor
• Acute cord compression
• Conversion disorder

AFM must be high on differential diagnosis in late summer or early fall, especially in patients with preceding viral symptoms.

Careful neurological examination, laboratory testing, and MRI of the spine and brain can help guide diagnosis.