What Is Acute Disseminated Encephalomyelitis (ADEM)?

Acute disseminated encephalomyelitis (ADEM) is a relatively uncommon illness that causes sudden, rapidly worsening neurological symptoms. It typically affects young children, but adults can experience the illness as well. 

The condition is caused by inflammation in the brain and spinal cord. The symptoms can be very unsettling, but because ADEM resembles several other neurological disorders, an accurate diagnosis may take up to a few weeks. Most people who have an episode of ADEM recover with minimal long-term deficits after getting treatment. 

Symptoms

The symptoms of ADEM begin suddenly and are often preceded by an infection, but this is not necessarily the case. The severe phase of it can last two to four weeks.

ADEM has an abrupt onset and usually a monophasic course (meaning there is no relapse).

Acute disseminated encephalomyelitis (ADEM) has been found to more frequently affect prepubertal children, from under 10 to 18 years in age, and young adults.

Symptoms of ADEM can include:

• Tingling or unusual sensations 
• Weakness of the arms, legs, or face
• Inability to walk
• Diminished sensation 
• Loss of bowel or bladder control 
• Changes in vision 
• Back pain 
• Seizures
• Coma

A typical episode of ADEM is characterized by more than one neurological symptom, and the effects of the illness are usually very noticeable.

Complications

Most of the time, ADEM resolves after treatment. Some people have mild residual symptoms, such as sensory deficit or weakness. The lingering symptoms are usually substantially less severe than the acute symptoms that occurred during the episode.

Some children and adults may have lasting cognitive deficits (learning problems) or behavioral changes after the episode has resolved.

If your child has trouble learning, seems to regress behaviorally or intellectually, or seems easily overwhelmed or frustrated after recovering from ADEM, discuss these issues with their doctor. Similarly, if a teenager or adult who has recovered from ADEM develops changes in thinking or behavior, be sure to seek medical attention.

Recurrence 

Most of the time, ADEM is not a recurring condition, and it occurs only once. However, you or your child can experience more than one episode.

It is impossible to predict whether the illness will occur again, so it is important to get medical care if similar symptoms begin to arise, even if they are mild.

Causes

ADEM is caused by inflammation in the brain and/or spinal cord. Inflammation is the body’s normal immune response to infections and injuries. 

The inflammation of ADEM does not fight an infection or repair an injury—instead, it actually attacks the body’s nervous system. This type of attack against one’s own body is described as an autoimmune reaction.

The inflammatory process in ADEM attacks myelin in the brain and spinal cord. Myelin is a type of fat that insulates nerves to help them function efficiently. The inflammatory process of ADEM affects the white matter of the brain and spinal cord. White matter is the more heavily myelinated sections, and it is located deep in the central regions of the brain and toward the outer sections of the spinal cord.

Triggers

It isn’t clear why ADEM occurs or whether there are any risk factors that predispose a person to the illness. Unlike many other autoimmune disorders, ADEM rarely recurs.

Experts have noted that the condition is often preceded by a simple viral or bacterial infection. It has been suggested that an infection could trigger the inflammatory demyelinating autoimmune reaction of ADEM. Some experts have also suggested that that the earliest phase of ADEM could be mistaken for an infection. Other triggers include certain types of vaccines.

Diagnosis

The diagnosis of ADEM may require a number of tests. With ADEM, medical complaints and physical examination signs are expected to be indicative of a multifocal neurologic syndrome. This means that you have more than one neurological symptom and that your physical examination shows several abnormal neurological signs. For example, your physical examination may show weakness, sensory deficits, or abnormal reflexes involving your arms and/or legs. Diagnostic examinations are generally done to determine the cause and extent of the neurological signs and symptoms.

Imaging Tests

You may need to have a brain or spine magnetic resonance imaging (MRI) test or computerized tomography (CT) so that your medical team can visualize any abnormalities your brain and/ or spinal cord. 

ADEM is characterized by several inflammatory demyelinating lesions in the white matter. Sometimes, the spine may have one or more longitudinal demyelinating lesions, which are lesions that extend in the vertical (up and down) direction.

Blood Tests and Specialized Tests

You are likely to have blood tests, which can detect signs of an acute infection, such as an elevated white blood cell count. 

A lumbar puncture (LP), also called a spinal tap, is a diagnostic test that may be necessary as well. It is a way for your medical team to examine your cerebrospinal fluid (CSF), which is a fluid that surrounds and nourishes the brain and spinal cord. An LP can identify signs of infection, inflammation, multiple sclerosis (MS), and cancer. A doctor performs this examination by cleaning an area of your lower back and inserting a needle to slowly collect CSF. The CSF is examined in a laboratory.

Differential Diagnosis

There are several conditions that may have signs and symptoms similar to those of ADEM. The history, physical examination, and diagnostic tests can usually distinguish these different conditions, but sometimes the distinction is not apparent and it can take weeks to establish the right diagnosis.

Clinically isolated syndrome (CIS): CIS is an episode that is very much like MS except that it occurs only once. CIS tends to affect adults, generally progresses more slowly than ADEM, is characterized by visual changes more often than ADEM is, and the CSF is highly likely to contain a protein called oligoclonal bands (the CSF in ADEM usually does not have oligoclonal bands).

Meningitis: Meningitis is inflammation or an infection of the meninges. The meninges are thin layers of tissue that enclose and protect the brain, spinal cord, and CSF. Meningitis is usually characterized by a fever, stiff neck, nausea, and vomiting, and sometimes, by multiple neurological signs and symptoms.

Imaging tests are usually normal and CSF often shows signs of an infection. There are different types of meningitis, and some viral meningitis often resolves on its own. Bacterial meningitis requires antimicrobial medication to prevent worsening of the infection or long-lasting effects.

Infectious encephalitis: A rare type of infection, encephalitis is an infection of the brain and/or spinal cord. This usually occurs when someone has a weak immune system. Encephalitis does not resolve on its own, and it usually requires treatment with powerful intravenous (IV) antibiotics. Encephalitis can involve several areas of brain or spinal cord and it is not limited to the white matter. The CSF is likely to show signs of an infection in encephalitis.

Cancer and meningeal carcinomatosis: Cancer can develop within the brain or spinal cord and it can also spread to the brain, spinal cord, or meninges from elsewhere in the body. In some instances, cancer can spread throughout the meninges and CSF, resulting in a serious and difficult to treat condition called meningeal carcinomatosis (also called lepomeningeal metastases). Often, imaging tests or a CSF evaluation show signs of cancer in these regions of the nervous system.

Treatment

ADEM is typically treated with a high dose of IV steroids to diminish the inflammation. There is no direct treatment for the demyelination, but typically the myelin is renewed once the inflammation resolves, which allows recovery from symptoms.

In rare instances, severe nerve damage can occur, and symptoms may remain even after the inflammation resolves.

ADEM or MS? 

CIS, MS, and ADEM are all inflammatory demyelinating conditions that affect the white matter in the brain and spinal cord. Because ADEM can be confused with CIS and MS, sometimes there is a question about whether it is appropriate to start a disease-modifying therapy (DMT) that would normally be used for MS. This is highly dependent on whether you have a strong risk of MS—such as a family history of the condition, or previous events that may have been subtle and undiagnosed signs of MS.

You and your medical team will have to weigh the pros and cons of this option because, while DMTs can prevent MS relapses, they have some side effects.

Rehabilitation

After recovery from an episode of ADEM, you or your child may have residual neurological deficits, such as weakness or trouble waking. If that is the case, rehabilitation may be necessary to regain as much neurological function as possible.

Rehabilitation may include a variety of approaches, including physical therapy, strengthening maneuvers, and at home exercises.

If there is a cognitive or behavioral issue, rehabilitation may be focused on identifying the specific deficits and creating a plan for recovery.

A Word From Verywell

If you or your child has been diagnosed with ADEM, there is no need to panic. While the symptoms can seem dramatic and frightening, with treatment, this condition usually has a good prognosis and recovery.