Symptoms and Causes of Acute Flaccid Myelitis

Symptoms of acute flaccid myelitis include the sudden onset of:

• Arm or leg weakness.
• Loss of muscle tone.
• Loss of reflexes (areflexia).
• Loss of coordination and balance.

These symptoms develop over a few hours or days.

Other symptoms include:

• Difficulty moving your eyes or drooping eyelids.
• Facial droopiness or muscle weakness.
• Difficulty with swallowing (dysphagia).
• Slurred speech.
• Pain in your arms, legs, neck or back.
• Bladder and bowel dysfunction.

AFM can affect any or all of your limbs, but it most commonly affects your upper limbs.

Sometimes, AFM can affect the muscles you need to breathe. This can lead to respiratory failure, which is life-threatening and requires immediate treatment.

Signs of respiratory failure include:

• Rapid and shallow breathing.
• Extreme fatigue and sleepiness.
• Restlessness.

If you or your child develop any symptoms of AFM, seek medical care right away.

What causes acute flaccid myelitis?

Researchers don’t know the exact cause of acute flaccid myelitis, but they think that viruses, especially non-polio enteroviruses, play a role in causing the condition. Most people with AFM had a mild respiratory illness (such as the common cold) or fever before they developed AFM.

Researchers and healthcare providers have suspected enterovirus D68 and enterovirus A71 in many AFM cases. Enterovirus D68 most often causes a respiratory illness and circulates in the United States during the summer and fall every other year.

Diagnosis and Tests

How is acute flaccid myelitis diagnosed?

It can be difficult for healthcare providers to diagnose AFM, as it’s rare and resembles other neurological conditions, such as transverse myelitis, Guillain-Barré syndrome and polio.

Your provider will ask about your symptoms and medical history. They’ll likely perform or order several tests to help diagnose AFM and/or rule out other conditions. Tests include:

• Physical exam.
• Neurological exam.
• MRI of your spinal cord and brain to look for changes in the gray matter of your spinal cord. This is the most useful test for confirming AFM.
• Spinal tap to check cerebral spinal fluid (CSF) to look for signs of inflammation.
• Nerve response tests like nerve conduction studies.
• Muscle response tests like electromyography.

Management and Treatment

What is the treatment for acute flaccid myelitis?

There’s no cure or specific treatment for acute flaccid myelitis. Instead, managing symptoms is the goal. If possible, it’s best to see a neurologist who has experience in treating and researching AFM.

Physical therapy and occupational therapy can help with arm and/or leg weakness. Neurologists typically recommend other treatments on a case-by-case basis. For example, peripheral nerve surgery that prevents muscle atrophy has been effective in some people with AFM.

As AFM is a rare and relatively new diagnosis, scientists and providers still have a lot to learn about it and its treatment.