Acute disseminated encephalomyelitis (ADEM) is a rare inflammatory condition affecting the brain and spinal cord. The symptoms of ADEM and its effects on the brain may be similar to those of multiple sclerosis (MS). Because of this, ADEM is sometimes misdiagnosed as a severe first attack of MS. However, some key features separate the two.

What Are ADEM and MS?

ADEM and MS are referred to as demyelinating disorders, meaning they attack the myelin sheath — the white covering surrounding nerve fibers. This coating, which is made up of fats and proteins, helps insulate and speed up the transmission of electrical signals. Damage to this coating (known as demyelination) leaves the nerves vulnerable, reducing their ability to transmit nerve signals properly.

ADEM is a rare condition in which brief, intense inflammation (swelling) affects the brain and the spinal cord. The inflammation seen in people with ADEM damages tissues in the brain known as white matter. This white matter contains nerve fibers, many of which are coated in myelin.

MS is a chronic autoimmune disease of the central nervous system (CNS), which includes the brain and spinal cord. In people with MS, the body’s defenders (white blood cells) attack the CNS, causing inflammation and stripping nerves of their myelin coating. Over time, this demyelination can cause people with MS to experience a variety of symptoms that affect physical movement, eyesight, and cognitive (mental) functioning.

What Causes ADEM?

It is not clear exactly what causes ADEM. In more than half of all cases of the condition, symptoms begin after a bacterial or viral infection — typically, a sore throat or cough. In some very rare cases, ADEM can appear after vaccination.

Neurology experts believe that ADEM occurs when the body’s immune system overreacts and attacks itself, rather than just the viral or bacterial invaders. This prompts the inflammation that, in turn, creates the symptoms of ADEM.

According to the National Multiple Sclerosis Society, children are more likely to develop ADEM than adults, and about 80 percent of childhood cases of the condition affect children younger than age 10. Girls are slightly less likely (40 percent of cases) to develop ADEM than boys (60 percent). ADEM is also seen more often in the spring and winter than in other seasons.

What Causes MS?

As with ADEM, researchers also do not know exactly what causes multiple sclerosis. Several environmental, genetic, and immunological factors are presumed to play a role in the development of MS.

Those most likely to be diagnosed with MS are female, white, and between 20 and 40 years old. In addition, people with a family history of the disease are at greater risk of developing MS. Certain factors also make diagnosis more likely:

• Viruses, like Epstein-Barr
• Living in a temperate climate
• Having low levels of vitamin D
• Smoking

Symptoms of ADEM vs. MS

Because ADEM and MS are demyelinating diseases, people with these conditions can present with similar symptoms, including muscle weakness, numbness, loss of vision, and loss of balance. There are, however, some key differences between the symptoms of the two conditions.

Multiple sclerosis is a chronic (long-lasting) disease. Its symptoms can be managed, but it has no known cure. MS may start with individual episodes or attacks (relapses), or gradual progression. ADEM, on the other hand, is usually a single immune reaction. Although it’s possible for a person to develop repeated inflammation in the brain and spinal cord, in most cases, ADEM occurs just once.

Symptoms of ADEM

The symptoms of ADEM usually come on quickly. Initially, they may resemble the symptoms of encephalitis (inflammation of the brain).

The inflammation seen in people with ADEM can affect the entire body. Like the symptoms of MS, ADEM symptoms are caused by damage to the nerves’ myelin coating. This demyelination can lead to the typical symptoms of ADEM, including headaches, confusion, fever, vomiting, and seizures. Some people may also experience sleepiness, irritability, difficulty walking, vision issues, weakness throughout the body, and tingling sensations.

ADEM may sometimes affect the optic nerves. Severe cases of ADEM can involve vision loss in one or both eyes, as well as muscle weakness, muscle paralysis, and struggling to coordinate one’s muscle movements. This can cause everyday activities, like walking and sitting up, to become difficult. Severe ADEM or ADEM affecting certain parts of the brain can also impair a person’s ability to remain conscious, and may even cause a coma — something rarely seen with MS.

Symptoms of Multiple Sclerosis

People with multiple sclerosis can have many of the same symptoms as those with ADEM, such as vision problems, fatigue, body weakness, numbness, and cognitive changes. However, the typical symptoms of ADEM — including seizures, vomiting, fever, headache, and confusion — are not commonly seen in people with MS.

It’s important to note that this does not mean that people with MS will never experience these symptoms. Although fevers are also not typical of MS, low-grade fevers can sometimes occur. Although about two percent to five percent of people with MS experience seizures, they do have a higher risk of seizures than the general population. The characteristic symptoms of ADEM are not usually seen in people with multiple sclerosis, but they are sometimes seen in pediatric MS onset — especially in children younger than 11 years old.

Generally speaking, the variety of symptoms seen in those with MS is more varied than in ADEM. For instance, many people diagnosed with MS experience tremors and electric shock sensations, which are much less common in ADEM. People diagnosed with MS may also experience emotional changes, problems with sexual or bowel/bladder function, tingling, and dizziness or vertigo.

ADEM and MS Symptom Onset and Recovery

MS usually comes on slowly, and people diagnosed with ADEM will have symptoms that come on quickly. ADEM almost always starts within four to 14 days after a person has had an infection or received an immunization.

The reason for this difference in onset time is that ADEM is monophasic, meaning it occurs as one large attack on the myelin. MS, conversely, is multiphasic — it involves many smaller attacks that take place over a longer time period. When the large attack that characterizes ADEM occurs, symptoms come on all at once. People diagnosed with MS often experience symptoms that build over time.

Recovery from ADEM usually begins quickly, within just a few days. After six months, most people will have recovered completely or nearly completely. Others, however, may experience mild to moderate lifelong difficulties. These may involve brain function, muscle function, vision function, or nerve function. People diagnosed with MS may find ways to modify its progression or to go into remission, but their symptoms will eventually return and can progressively worsen.

Diagnosing ADEM vs. MS

MS and ADEM can be difficult to diagnose. Multiple sclerosis is believed to be misdiagnosed at least 10 percent of the time. When a person presents with symptoms that could qualify them for either diagnosis, the question doctors ask is whether they may have ADEM or whether they could be experiencing their first attack of multiple sclerosis. If you suspect you have either condition, see your doctor immediately.

Diagnosis of both conditions will usually involve giving your neurologist your health history, as having family members with MS may increase your likelihood of developing it. A doctor may also order various tests, including a magnetic resonance imaging scan (MRI) performed with or without contrast dye, a spinal tap to test cerebrospinal fluid, blood tests, and tests that measure how long it takes for your nerves to respond to different stimuli.

A differential diagnosis between ADEM and MS occurs, in part, based on differences in brain MRIs, myelin oligodendrocyte glycoprotein, and cellular bonds.

Brain MRIs

Brain MRI results of people diagnosed with ADEM are usually different from those of people diagnosed with MS. The patterns of lesions caused by demyelination will be different. In addition, follow-up MRIs on a person diagnosed with MS usually show more damage over time, while that is not true of those diagnosed with ADEM.

Myelin Oligodendrocyte Glycoprotein

People diagnosed with ADEM are more likely to have evidence in their blood of attacks against a certain type of antibody, called the myelin oligodendrocyte glycoprotein (MOG). In fact, between 36 percent and 64 percent of children diagnosed with ADEM have this evidence, while it is not common in those diagnosed with MS.

Cellular Bonds

Certain types of cellular bonding to a wide variety of antigens is more common in those diagnosed with ADEM than it is in those diagnosed with multiple sclerosis. These bonds can be seen in certain types of blood tests.

Talk to a Neurology Expert

If you or someone you love is experiencing symptoms that could be either ADEM or MS, getting prompt medical help is key. See a neurology expert or get emergency care, if necessary, to find out what is causing your symptoms and receive the right treatment.

Find Your Community

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