Acute flaccid myelitis (AFM) is a rare but serious cause of sudden limb weakness, especially in children. A case is confirmed when flaccid limb weakness comes on suddenly and an MRI shows spinal cord lesions largely confined to the gray matter, over one or more vertebral segments.
Since a cluster of three cases in 2014, Minnesota had averaged fewer than one AFM case a year. Then, from September 14 to October 1, 2018, the Minnesota Department of Health heard of six children hospitalized in the Minneapolis–St. Paul region with AFM symptoms. CDC confirmed all six — the largest AFM cluster Minnesota had identified, during a period of rising AFM reports nationally.
The children
- Ages 1.3 to 9.2 years (median 6.0); each lived in a different county, and no links among them were found. None had a weakened immune system.
- All first had fever and a cold-like illness — runny nose, cough — a median of 8 days (range 5–11) before the weakness. Four also had neck pain or headache; two had diarrhea.
- In every case, the weakness was first noticed on waking in the morning.
| Weakness | Children |
|---|---|
| One arm — marked weakness of the proximal muscle groups, with movement farther down the arm largely kept | 4 |
| One leg, which spread to both legs and rose quickly up the body in the hospital; both needed a breathing tube and ventilator | 2 |
In the hospital
MRI showed spinal cord gray matter involvement in all six, mostly in the anterior horns. The scans didn't always match the exam: three children with weakness in only one limb had involvement across several segments. Three had normal first MRIs that later showed extensive gray matter involvement. Three showed enhancement of anterior nerve roots and the facial nerve; two had involvement of the brainstem.
| Treatment | Children |
|---|---|
| Steroids, plasmapheresis, then intravenous immune globulin (IVIG) | 1 |
| Steroids, then IVIG | 1 |
| IVIG only | 3 |
| Supportive care only | 1 |
| Outcome at the time of the report | Children |
|---|---|
| Home | 3 |
| Inpatient rehabilitation | 2 |
| Still in hospital, with complete paralysis of all voluntary muscles, including the diaphragm | 1 |
Every child who went home or to rehabilitation still had some weakness; their hospital stays ranged from 1 to 14 days (median 8).
What the tests found
- Spinal fluid was collected from five children; two had raised white cell counts. One sample (patient B) was positive for enterovirus at a commercial lab, and CDC found enterovirus D68 (EV-D68) in it.
- Nose and throat samples: patient D's was positive for EV-D68; patient B's nasal washes were positive for EV-D68, and one also for parechovirus A6.
- Samples from the other three children were all negative, and every stool sample was negative for poliovirus.
So although all six had had cold-like symptoms, common respiratory viruses turned up in only two. EV-D68 in patient B's spinal fluid is considered the cause of that child's AFM; finding the virus there may be linked to how severe and prolonged the illness was, though what else made it so severe is unknown.
For clinicians
- Consider AFM in any child with sudden limb weakness.
- Collect specimens early — including spinal fluid — get MRI scans, and consult neurology and infectious disease specialists.
- Report possible cases to public health promptly — but don't delay care while experts review and classify the case.
Sources
Based on Moline H, Kalaskar A, Pomputius WF III, Lopez A, Routh J, Kenyon C, Griffith J, "Notes from the Field: Six Cases of Acute Flaccid Myelitis in Children — Minnesota, 2018," MMWR volume 68, number 15, Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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