History
AFM has only been formally tracked since 2014, since the incidence has spiked in recent years.A group in Texas reported having observed a pattern in 2013 of one to four cases per year with similar polio-like characteristics.In 2014, the CDC Morbidity and Mortality Weekly Report and a CDC Clinician Outreach and Communication Activity (COCA) conference call, noted that many cases had neck, back, or extremity pain, but otherwise those affected generally had normal sensation in their limbs. A few participants in the conference call discussed whether pain, later abating, might precede the onset of paralysis.An October 2014 report described outbreaks in California and Colorado, suggesting that the number of cases might be 100 or more nationwide. Diagnosis included a detailed medical history, MRI imaging, and the elimination of transverse myelitis or Guillain–Barré syndrome as potential causes. Physicians were using an online mailing list to communicate about similar cases in Alabama and Kansas. The largest known cluster of cases was in Colorado, with 29 total, 12 of whom had been reported from August and onwards of that year. Three of four cases treated in Alabama involved a complete inability to move one arm, reminiscent of peripheral nerve injury: The three cases since August really look like each other. They have severe arm flaccidity and no mental status changes. All of them have similar spine MRIs showing gray-matter involvement. You could lay all three MRIs on top of each other and they look almost the same. Its pretty striking. ...
It you lift the arm up, it literally drops. Sensation is usually intact. There might be slightly decreased sensation in the other arm, but these are younger kids, so theyre not always so cooperative in giving you a good sensory exam. Childrens Mercy Hospital, which had three or four cases in 2014, reported that the MRI images and symptoms closely mimicked polio. They reported: "The sudden onset of flaccid paralysis in single or multiple limbs with absolutely no sensory findings, the MRIs all showing uniformly a signal increase in the ventral horns of the spinal cord — this is exactly the same region of the spinal cord affected in polio ... Almost all of the patients have an increase in their white blood cells in the cerebrospinal fluid. Some of the patients have brainstem findings and cranial-nerve findings. "Of 64 patients meeting the CDC criteria before October 29, 2014, 80% had had a preceding respiratory illness and 75% reported fever in the days leading up to limb weakness, the onset of which was generally abrupt. By November 20, the number of confirmed cases stood at 88 from 29 states.The CDC requested that physicians provide information about cases meeting these criteria: patients diagnosed after August 1, 2014, who are no older than 21 years of age, showing acute onset of focal limb weakness, with a spinal-cord lesion largely restricted to grey matter visualized by MRI.In November 2018, the CDC reported that they were investigating 286 cases, with at least 116 confirmed cases in 31 states.