Acute Flaccid Myelitis: Do I Need to Worry?

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Debbie is the mother of Brooke, a healthy 4 month old girl. Debbie took Brooke to the local ER because the infant kept her arms in a flexed position, bent at the elbows, and was not moving them as much. She had no fever, did not seem to be in pain, had no swelling or bruising anywhere, and otherwise was acting normally. She recently had a cold, but that resolved, and then the lack of movement in the arms appeared. Debbie stated that Brooke had been rolling over during the past several weeks, but had not done so in the last 4 days.1

In the ER, the doctors noted Brooke had a weak cry, absent or decreased reflexes, and hypotonia (low muscle tone) all over her body. All the usual blood and urine tests were normal. An MRI of her spinal cord showed abnormal findings consistent either with transverse myelitis (inflammation of the spinal cord with a variety of causes) or acute flaccid myelitis. She was given intravenous immunoglobulins (antibodies used to fight infectious or inflammatory diseases) and steroids. After 5 days of treatment, Brooke’s cry the muscle tone in her arms improved, but her leg muscle tone was still poor. She was transferred to a rehabilitation hospital for more intensive physical and occupational therapy.

What Is Acute Flaccid Myelitis?

Brooke has acute flaccid myelitis (AFM), a serious neurological condition that causes muscle weakness in one or more limbs, hypotonia, and decreased reflexes. Specifically, the condition affects the area of the spinal cord known as the gray matter, as in Brooke’s case.2-3

It is not a new disease, but was almost unheard of before 2014. Since then, there has been an increase in cases every year.

Currently, there is no known cause of AFM, but experts think that a virus is the cause. Like Brooke, over 90% of the patients identified since 2014 have had a preceding upper respiratory illness (a cold) or fever consistent with a viral infection before contracting AFM.2 To date, no single virus has been identified as the cause, but many viruses have been found in the patients with AFM, including enteroviruses. AFM looks a lot like polio, which is caused by another type of enterovirus, but no poliovirus has been found in any of the patients with AFM.

Most patients show onset of symptoms between August and October, and over 90% of the cases are in children.2

It is important to remember that acute flaccid myelitis is extremely rare, occurring in less than 1-2 in a million children per year, according to the CDC.2

What Are the Symptoms?

Symptoms of AFM include:2

  • Sudden arm or leg weakness: most people will have this symptom.
  • Difficulty moving the eyes or drooping eyelid
  • Facial droop or weakness
  • Trouble swallowing
  • Slurred speech
  • Pain in arms or legs: but tingling or numbness is rare
  • Unable to pass urine
  • Respiratory failure due to muscle weakness: this is rare in AFM, but can occur.

Not all of these symptoms will be seen in every patient with AFM.

The diagnosis is usually made with an MRI of the spinal cord, tests on spinal fluid, and nerve conduction tests.

Again, most cases are often preceded by cold or fever consistent with viral infection. If you notice any of these symptoms, call your doctor.

Is There a Treatment?

Unfortunately, there is not a treatment at this time. Usually, doctors will order intense physical and occupational therapy to help restore function. Other treatments have not been proven to be effective, but are sometimes tried to see if they help. These may include steroids, immunoglobulins, plasmapheresis (a process of filtering the plasma that is similar to dialysis), and other treatments.2 You can find out more about some of those treatments here.

The long term outcome of AFM is unclear, but residual neurological deficits are common.

So should you worry about AFM? Well, remember that it is extremely rare, so in terms of the likelihood that your child will contract AFM, then no, there are many other more common things to worry about and try to prevent. But if you or your child have any of those symptoms described above, call your doctor. Even with those symptoms, there is probably some other more common diagnosis that is the cause. But whatever the cause, you should seek medical attention if these symptoms are present.

References:

  1. Sierakowski J, Arthur J, Wylie T. Acute hypotonia in an infant. J Emerg Med. 2017 Jun;52(6):e245-e247.
  2. Centers for Disease Control and Prevention. Acute Flaccid Myelitis. https://www.cdc.gov/acute-flaccid-myelitis/.
  3. Andersen EW, et al. Acute flaccid myelitis in childhood: a retrospective cohort study. Eur J Neurol. 2017 Aug:24(8):1077-1083.
Ruben Rucoba
Dr. Rucoba has over 25 years of experience as a primary care pediatrician after completing medical school at the University of California, San Francisco. His clinical areas of expertise include caring for children with special health care needs and assisting families with international adoption. He has been a freelance medical writer since 2010, writing for health websites, continuing medical education providers, and various print outlets. He currently works at Wheaton Pediatrics in the suburbs of Chicago, where he lives with his wife and four daughters, including a set of twins.

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