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Key Features

Essentials of Diagnosis

  • Viral illness precedes neurologic signs

  • Flaccid paralysis usually affects upper limbs or all four limbs

  • Enterovirus is commonly isolated; poliomyelitis must be ruled out

General Considerations

  • Before widespread polio vaccination in the 1950s, polio was the most common cause of acute flaccid myelitis (also known as acute flaccid paralysis)

  • This disease has been reported throughout

    • Africa (20 countries)

    • The Eastern Mediterranean region (5 countries)

    • Intermittently in Europe (Germany and France)

    • The United States (48 states and the District of Colombia)

  • The CDC began surveillance for acute flaccid myelitis in 2014

    • Since then, there have been three outbreaks in the United States

      • The largest to date occurred in 2018, with 80 confirmed cases between January 1, 2018, and November 1, 2018

      • All but 1 of the cases (99%) had a preceding viral illness in the month before presentation of neurologic signs

  • The most commonly associated viruses (among the 50 cases in which virus was isolated) were enterovirus A71 and enterovirus D68

  • In all instances, poliomyelitis was ruled out, but an exact cause for the acute flaccid myelitis was not always determined

  • All suspected cases should be reported to the state health department, the CDC or both

Clinical Findings

  • Usually a childhood disease; the average age of presentation is 5 years

  • Cases usually present in late summer or early fall

  • There are three clinical stages of acute flaccid myelitis

    • A prodromal illness

    • Acute neurologic injury

    • Convalescence

  • Prodrome illness typically consists of

    • Fever

    • Upper respiratory symptoms

    • Gastrointestinal symptoms

  • Neurologic symptoms

    • Begin 1–4 weeks later

    • Usually manifest as flaccid limb weakness with decreased reflexes

    • Fever may recur, and the patient experiences myalgia and flaccid weakness in one or more limbs

    • Upper extremities are affected more often than lower extremities

  • Convalescent phase

    • Can last for months to years

    • Patients may experience residual muscle weakness and atrophy


Laboratory Findings

  • Cerebrospinal fluid analysis shows pleocytosis (white blood cells > 5/mcL [0.005 × 109/L]) often with an elevated protein level (and a normal glucose concentration)

  • All individuals with suspected acute flaccid myelitis should be tested for enteroviruses (including D68 and A71) and rhinovirus from relevant anatomic sites

  • Testing for arboviruses, adenovirus, and herpesviruses should also be considered


  • MRI typically shows disease of the central gray matter within the spinal cord in the location of the anterior horn cells

  • MRIs of the brain and spinal cord should be accompanied by lumbar puncture


  • No specific treatment

  • Supportive care

  • Many adjunctive therapies have been used, including IVIG, high-dose corticosteroids, and plasmapheresis, but none have shown efficacy

  • Long-term therapy during the ...

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