ADEM is short for acute disseminated encephalomyelitis.

This neurological condition involves a severe bout of inflammation in the central nervous system. It can include the brain, spinal cord, and sometimes the optic nerves.

The swelling can damage myelin, the protective substance that coats nerve fibers throughout the central nervous system.

ADEM occurs all over the world and in all ethnic groups. It happens more frequently in the winter and spring months.

About 1 in 125,000 to 250,000 people develop ADEM each year.

Over 50 percent of people with ADEM experience an illness in the preceding two weeks. This illness is usually a bacterial or viral upper respiratory tract infection, but it can be any kind of infection.

Symptoms usually come on suddenly and can include:

  • fever
  • headache
  • stiff neck
  • weakness, numbness, and tingling of the arms or legs
  • balance problems
  • drowsiness
  • blurred or double vision due to inflammation of the optic nerve (optic neuritis)
  • difficulty swallowing and speaking
  • bladder or bowel problems
  • confusion

It’s not typical, but ADEM can lead to seizures or coma.

Most of the time, symptoms last a few days and improve with treatment. In the most severe cases, symptoms can linger for several months.

The exact cause of ADEM isn’t known.

ADEM is rare, and anyone can get it. It’s more likely to affect children than adults. Children under age 10 represent over 80 percent of ADEM cases.

It usually occurs a week or two after an infection. Bacterial, viral, and other infections have all been associated with ADEM.

Occasionally, ADEM develops after a vaccination, usually the one for measles, mumps, and rubella. The resulting immune system response causes inflammation in the central nervous system. In these cases, it may take up to three months after the vaccine for symptoms to appear.

Sometimes, there’s no vaccination or evidence of infection prior to an ADEM attack.

Check out: Demyelination: What is it and why does it happen? »

If you have neurologic symptoms consistent with ADEM, your doctor will want to know if you’ve been ill within the past few weeks. They’ll also want a complete medical history.

There’s no single test that can diagnose ADEM. Symptoms mimic those of other conditions that must be ruled out. The diagnosis will be based on your specific symptoms, physical examination, and diagnostic tests.

Two tests that can help with the diagnosis are:

MRI: The scans from this noninvasive test can show changes to white matter in the brain and spinal cord. Lesions or damage to white matter could be due to ADEM, but it could also indicate a brain infection, tumor, or multiple sclerosis (MS).

Lumbar puncture (spinal tap): Analysis of your spinal fluid can determine if symptoms are due to infection. The presence of abnormal proteins called oligoclonal bands means that MS is the more likely diagnosis.

The goal of treatment is to reduce inflammation in the central nervous system.

ADEM is usually treated with steroid medications such as methylprednisolone (Solu-Medrol). This medication is administered intravenously for five to seven days. You may also need to take oral steroids, such as prednisone (Deltasone), for a short time. Depending on your doctor’s recommendation, this could be anywhere from a few days up to a few weeks.

While on steroids, you’ll need to be carefully monitored. Side effects can include a metallic taste, swelling of the face, and flushing. Weight gain and difficulty sleeping are also possible.

If steroids don’t work, another option is intravenous immune globulin (IVIG). It’s also given intravenously for about five days. Potential side effects include infection, allergic reaction, and shortness of breath.

For severe cases, there’s a treatment called plasmapheresis, which usually requires a stay in the hospital. This procedure filters your blood to remove harmful antibodies. It may have to be repeated several times.

If you don’t respond to any of these treatments, chemotherapy can be considered.

Following treatment, your doctor may want to perform a follow-up MRI to make sure the inflammation is under control.

ADEM and MS are remarkably similar, but only in the short term.

How they’re alike

Both conditions involve an abnormal immune system response that affects myelin.

Both can cause:

  • weakness, numbness, and tingling of the arms or legs
  • balance problems
  • blurred or double vision
  • bladder or bowel problems

Initially, they can be difficult to tell apart on MRI. Both cause inflammation and demyelination in the central nervous system.

Both can be treated with steroids.

How they’re different

Despite the similarities, these are two very distinct conditions.

One clue to the diagnosis is that ADEM can cause fever and confusion, which aren’t common in MS.

ADEM is more likely to affect men, while MS is more common in women. ADEM is also more likely to occur in childhood. MS is usually diagnosed in early adulthood.

The most notable difference is that ADEM is almost always an isolated incident. Most people with MS have recurring attacks of inflammation of the central nervous system. Evidence of this can be seen on follow-up MRI scans.

That means treatment for ADEM is also most likely a one-time thing. On the other hand, MS is a chronic condition that requires ongoing disease management. There are a variety of disease-modifying treatments designed to slow the progression.

Learn more: Acute disseminated encephalomyelitis vs. MS »

In rare instances, ADEM can be fatal. More than 85 percent of people with ADEM recover fully within a few weeks. Most others recover within a few months. Steroid treatments can shorten the duration of an attack.

A small number of people are left with mild cognitive or behavioral changes, such as confusion and drowsiness. Adults may have a harder time recovering than children.

Eighty percent of the time, ADEM is a one-time event. If it does return, your doctor may want to perform additional testing to confirm or rule out MS.

Because the exact cause isn’t clear, there’s no known prevention method.

Always report neurological symptoms to your doctor. It’s important to get a proper diagnosis. Treating inflammation in the central nervous system early can help prevent more severe or lasting symptoms.