Acute Disseminated Encephalomyelitis, Adult

Acute disseminated encephalomyelitis (ADEM) is a rare condition of sudden severe inflammation in the central nervous system. The central nervous system includes the brain and spinal cord. The condition can also affect the nerves of the eyes (optic nerves). With ADEM, inflammation attacks the protective covering around nerves (myelin sheath). This disrupts nerve conduction, which causes symptoms that include changes in brain function (encephalopathy).

ADEM is most common in children and young adults, but older adults may also be affected. ADEM happens more often in the winter and spring. Symptoms start suddenly and can range from mild to severe. Most people recover within 3 months of starting treatment. In most cases, ADEM does not come back after treatment.

What are the causes?

The exact cause of this condition is not known. You may develop ADEM if your body’s defense system (immune system) mistakenly attacks the myelin of your central nervous system (autoimmune reaction). In many people, the condition may be triggered by an infection. ADEM can be triggered by:

  • A viral infection. This is the most common cause.

  • Another type of infection, such as a bacterial infection.

  • Some other unknown cause.

In rare cases, ADEM was associated with certain vaccines in the past, particularly smallpox and rabies vaccines. These vaccines have been modified, and no currently approved vaccines in the United States are associated with ADEM.

What are the signs or symptoms?

The first symptoms of ADEM usually begin from 2 days to 4 weeks after an infection. They may be similar to the symptoms of other conditions. General symptoms may include:

  • Fever.

  • Headache.

  • Nausea or vomiting.

  • Tiredness.

  • Irritation.

  • Sleepiness.

Symptoms of encephalopathy may include:

  • Confusion.

  • Slurred speech.

  • Clumsiness and loss of balance while walking (ataxia).

  • Weakness, numbness, or paralysis.

  • Changes in vision.

  • Seizure.

  • Difficulty breathing (in severe cases).

How is this diagnosed?

Your health care provider may suspect ADEM based on your symptoms. A physical exam and a brain imaging study, such as an MRI, may be done to look for specific symptoms of the condition. To confirm a diagnosis of ADEM, your health care provider will check for:

  • Damage (lesions) in more than one area of the central nervous system.

  • Symptoms of encephalopathy.

You may also have other tests to rule out similar conditions, such as multiple sclerosis. These tests may include blood tests and a spinal tap (lumbar puncture).

Having no new symptoms or lesions after 3 months may help confirm a diagnosis of ADEM.

How is this treated?

A strong anti-inflammatory medicine (corticosteroid) is the main treatment for ADEM. You may start taking corticosteroids as soon as your health care provider suspects you have the condition. Your symptoms may improve within days of starting treatment. At first, you may get a high dose of corticosteroids by IV for about 5 days. You may continue to take corticosteroid medicine by mouth for 4 to 6 weeks. The dose is reduced gradually.

If corticosteroids are not helping, you may get a transfusion of antibodies from a healthy donor (intravenous immunoglobulins). You may also have a transfusion of your own white blood cell fluid (plasma) after autoimmune antibodies have been filtered out. This procedure is called plasmapheresis.

Follow these instructions at home:

  • Take over-the-counter and prescription medicines only as told by your health care provider.

  • Take corticosteroid medicine as told by your health care provider. Do not stop taking it even if you start to feel better.

  • Return to your usual activities as told by your health care provider. Ask your health care provider what activities are safe for you.

  • Keep all follow-up visits. This is important.

Where to find more information

Contact a health care provider if:

  • You have new symptoms.

  • Your existing symptoms get worse.

  • Your symptoms last longer than 3 months.

  • Your symptoms return after 3 months.

Get help right away if:

  • You have a seizure.

  • You have trouble breathing.

These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.). Do not drive yourself to the hospital.


  • ADEM is a rare condition of sudden and severe inflammation in the central nervous system.

  • The exact cause of the condition is not known. It may be caused by an autoimmune reaction that is triggered by an infection.

  • Symptoms may start suddenly 2 days to 4 weeks after an infection.

  • Corticosteroid medicine is the main treatment for ADEM.

  • Symptoms may start to improve days after starting treatment, and most people recover within 3 months. In most cases, ADEM is a one-time event.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.

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