Acute Flaccid Myelitis (AFM) is a type of inflammation in the spinal cord that has specific clinical and MRI features. AFM abnormalities noted on MRI are predominantly found in the gray matter (lower motor neuron) of the spinal cord. In 2012, an outbreak of AFM occurred in California and more cases were reported in the summer and fall of 2014, 2016, and 2018 across the United States. Non-polio enteroviruses have been implicated as potential causal factors in the development of AFM. The enterovirus D68 and enterovirus A71 have been suspect in many of these cases, although others such as coxsackie viruses have been implicated as well. Enterovirus D68 most often causes a respiratory illness and has been circulating in the United States during the summer and fall every two years since 2014, which coincides with the increase of cases of AFM seen every other year. It has not been definitively proven that these particular viruses have directly caused cases of AFM but the temporal onset of neurological symptoms with infections produced by those viruses implicate them as direct or indirect triggers of the neurological problem.
AFM
Signs & Symptoms
Most of those diagnosed with AFM report having a respiratory or gastrointestinal illness before the onset of weakness. The predominant presentation is a rapid onset of weakness that may affect the limbs, face, oropharyngeal muscles, or the muscles that control breathing. Those with AFM may not be able to breathe, swallow, or move their eyes normally. Weakness varies greatly ranging from mild to very severe. AFM may result in weakness, partial paralysis, or total paralysis of just one limb or all limbs. The pattern of paralysis and how individuals present are widely variable. Weakness most often occurs in proximal muscles, meaning the muscles closest to the center of the body. Pain in the neck, back, or limb may be an early symptom. Autonomic instability, such as issues with heart rate, may occur as well. Since it is mainly the gray matter of the spinal cord that is damaged in individuals with AFM, they may not have bladder or bowel dysfunction or issues with sensation. However, some individuals may have inflammation in both the white and gray matter of the spinal cord (upper and lower motor neuron), so some of those with AFM may experience impaired sensation, bladder, and/or bowel dysfunction.
