Acute disseminated encephalomyelitis (ADEM) and multiple sclerosis (MS) are inflammatory autoimmune disorders. Our immune system protects us by attacking foreign invaders that enter the body. Sometimes, the immune system mistakenly attacks healthy tissue.

In ADEM and MS, the target of the attack is myelin, which is the protective insulation that covers nerve fibers throughout the central nervous system (CNS). Damage to myelin makes it difficult for signals from the brain to get through to other parts of the body. This can cause a wide variety of symptoms, depending on the area(s) damaged.

Learn more: Autoimmune disease »

In both ADEM and MS, symptoms include vision loss, weakness, and numbness. Problems with balance and coordination or difficulty walking are common. In severe cases, paralysis is possible. Symptoms vary according to the location of the damage within the CNS.

Symptoms of ADEM come on suddenly. Unlike MS, they can include:

Most of the time, an episode of ADEM is a single occurrence. Recovery usually begins within days, and the majority of people make a full recovery within six months. MS lasts a lifetime. In relapsing-remitting forms of MS, symptoms come and go but may lead to accumulation of disability. People with progressive forms of MS experience steady deterioration and permanent disability.

One can develop ADEM at any age, but it’s more likely to occur in children under the age of 10 years old. In fact, according to the National Multiple Sclerosis Society, more than 80 percent of ADEM cases occur in people younger than 10 years old. Most other cases occur in people between the ages of 10 and 20. ADEM is rarely diagnosed in adults. Experts believe ADEM affects 1 in every 125,000 to 250,000 people in the United States annually.

It’s more common in boys than girls, affecting boys 60 percent of the time, and it’s seen across the world in all ethnic groups. It’s more likely to appear in the winter and springtime than the summer and fall. ADEM often develops within months of an infection. In rare cases, it may be triggered by an immunization. Doctors aren’t always able to identify the triggering event.

MS can also develop at any age. However, it’s usually diagnosed between the ages of 20 and 40, with 32 being the average age of diagnosis. MS strikes women at twice the rate of men, and disease incidence is higher in Caucasians than in people of other ethnic backgrounds. It becomes more prevalent the farther away one moves from the equator. Experts believe MS affects about 400,000 people in the United States or about 90 out of 100,000 people. MS isn’t hereditary, but researchers believe there’s a genetic predisposition toward developing MS. Having a first-degree relative — such as a sibling or parent — with MS slightly increases your risk.

Due to similar symptoms and the appearance of lesions or scars on the brain, it’s easy for ADEM to be initially misdiagnosed as an MS attack. ADEM generally consists of a single attack, while MS involves multiple attacks. In this instance, an MRI of the brain can help.

Read more: Why getting a second opinion on multiple sclerosis counts »

MRI can differentiate between older and newer lesions. The presence of multiple older lesions on the brain is more consistent with MS. The absence of older lesions could indicate either condition.

However, several key factors in ADEM distinguish it from MS, including sudden fever, confusion, and possibly even coma. These are rare in MS patients. Similar symptoms in children are more likely to be ADEM.

When trying to differentiate ADEM from MS, doctors may also:

  • ask for your medical history, including a recent history of illnesses and vaccinations
  • ask about your symptoms
  • perform a lumbar puncture (spinal tap) to check for infections in the spinal fluid, such as meningitis and encephalitis
  • perform blood tests to check for other types of infections or conditions that could be confused with ADEM

The cause of ADEM isn’t well-understood. However, experts have noticed that, in more than half of all cases, symptoms arise after a viral or bacterial infection and very rarely after a vaccination for measles, mumps, or rubella. But in some cases, no causal event is known and vaccination prior to ADEM diagnosis is rare.

Most researchers believe that MS is caused by a genetic predisposition to developing the disease combined with a viral or environmental trigger.

Neither condition is contagious.

The goal of treatment for ADEM is to stop inflammation in the brain. Intravenous and oral corticosteroids aim to decrease the inflammation and can usually control ADEM. In more difficult cases, intravenous immunoglobulin therapy may be recommended. Long-term medications aren’t necessary.

MS currently has no cure. Disease-modifying drugs are used to treat relapsing-remitting MS in the long term. However, these drugs have no benefit for people with progressive MS. Recently, a new drug has been approved for the treatment of progressive forms of MS. Targeted treatments can help manage individual symptoms and improve quality of life.

Read more: Multiple sclerosis (MS) treatments »

About 80 percent of people have a single episode of ADEM. Most make a complete recovery within months following the illness. In a small number of cases, a second attack of ADEM occurs within the first few months.

More severe cases that can result in lasting impairment are rare. According to the Genetic and Rare Disease Information Center, “a small fraction” of people diagnosed with ADEM eventually develop MS.

MS worsens over time, and there is no cure. Treatment may be ongoing.