Acute Disseminated Encephalomyelitis MRI: Scan & Appearance

If you or a loved one is experiencing fever and illness after a viral infection, you may be concerned about acute disseminated encephalomyelitis (ADEM). Although rare, this inflammatory condition can be serious, especially in children, so it’s natural to be worried. 

Our guide will take you through the symptoms of ADEM, its causes and treatment, and explain why an MRI is the gold standard for detecting ADEM and other disorders that cause brain and spinal cord inflammation. 

What is Acute Disseminated Encephalomyelitis?

Acute disseminated encephalomyelitis is a rare inflammatory autoimmune disorder that affects the brain and spinal cord and is caused by a disordered immune system response to a viral infection, such as measles, flu, or vaccination. 

The immune system attacks the healthy myelin, a fatty coating that protects the nerves in the brain and spinal cord. Myelin is essential for fast and efficient signalling along the nerves, so signals can slow or become disrupted when it’s damaged or removed. This leads to a series of neurological symptoms, such as nausea, unsteadiness, problems with vision or even seizures. ADEM often progresses quickly, over hours or days, so symptoms can come on suddenly.

Acute disseminated encephalomyelitis usually affects children and teenagers under 15, though it can happen at any age. It’s more common in the spring when viral infections, such as flu and other respiratory diseases, peak. Children between the ages of 5 and 8 are most commonly affected.

What Are the Symptoms of Acute Disseminated Encephalomyelitis?

Symptoms of ADEM can vary widely, changing from person to person, depending on which part of the brain or spinal cord is affected. Some people have only mild symptoms, while others can present with more severe signs of ADEM.

Fever and systemic illness

ADEM often begins with a mild fever and general illness, usually several days after the triggering infection or event. Someone with ADEM may feel like they have flu, feel tired, uncomfortable, and are generally ill as the body reacts to the infection or immune response. Symptoms may also include headaches, nausea or vomiting.

Neurological symptoms

Neurological symptoms will become worse as the condition progresses and may include:

• Difficulty with coordination and movements or a loss of balance (ataxia)

• Weakness in the arms or legs

• As the inflammation disrupts cranial nerve signals in the brain, people may experience symptoms such as double vision, slurred speech, hearing loss, difficulty swallowing and loss of smell or taste.

• Sensory changes such as numbness, burning sensations or tingling in the body

• Sudden bursts of electrical activity in the brain (seizures)  that cause changes in behaviour, movement or even convulsions. These are more common in children under five.

• Inflammation of the optic nerve can lead to vision problems, such as blurred vision or temporary vision loss.

• In severe cases, someone with ADEM may fall into a state of deep unconsciousness (coma) as the inflammation causes damage to, or dysfunction in, the brain.

Bladder and bowel problems

If the inflammation affects the spinal cord, people may experience urinary incontinence or have difficulty emptying their bladder completely. They may also become constipated or lose control over their bowel movements.

Meningeal signs

Some people with ADEM may show symptoms similar to meningitis, such as neck stiffness and sensitivity to light (photophobia), though these symptoms are less common.

Will ADEM Show on an MRI?

Yes. Magnetic resonance imaging for ADEM is one of the key tools doctors will use to diagnose the condition. This is because areas of damage caused by inflammation and demyelination in the brain and spinal cord (lesions) show up clearly on MRI. Spotting these lesions is crucial for medical experts to differentiate ADEM from other demyelinating disorders. 

What Does ADEM Look Like on an MRI?

In ADEM, lesions can appear in different parts of the brain, especially the white matter (the brain areas that transmit signals) and grey matter (where brain processes happen).

These lesions are often scattered and asymmetric—meaning they don’t follow a clear pattern or shape, and their edges may be blurred. They can also appear in the brainstem, cerebellum, and spinal cord, but these areas rarely show damage on their own without also showing issues in the brain.

Lesions will appear as bright spots on certain types of MRI scans, such as T2-weighted and FLAIR scans. Other MRI scans, such as T1-weighted, usually don’t show these areas clearly, but more extensive lesions may appear darker.

Diagnosing ADEM 

Your clinician will take several steps to ensure that ADEM is clearly diagnosed and that other conditions or illnesses are ruled out. Here’s how they’ll do it:

Clinical evaluation

Your doctor will perform a physical examination and take a medical history of recent infections or vaccinations. They’ll also ask about any physical or neurological symptoms. 

Neurological examination

The clinician will conduct a series of tests to identify and assess neurological symptoms. These tests may change from person to person but may include speech, movement and reflexes assessment. They help your doctor determine whether the symptoms are due to ADEM or another condition. 

MRI scan of the brain and spinal cord

An MRI scan is essential for diagnosing ADEM. It often shows areas of damage (lesions) in the brain and spinal cord. These lesions are usually on both sides of the brain, which helps tell ADEM apart from other conditions, like multiple sclerosis. During the MRI, injecting a contrast agent (dye) may help identify areas of active inflammation.

Lumbar puncture (CSF analysis)

A lumbar puncture (also known as a spinal tap) is a procedure that takes a small sample of cerebrospinal fluid (CSF) from the base of the spine. When ADEM is present, the CSF typically shows an increase in white blood cells, especially lymphocytes. These cells are part of your immune system and help fight infections.

Blood tests

Your doctor will offer blood tests to check for other infections or autoimmune issues that could be causing your symptoms. Though there are no specific blood tests for ADEM, it’s important to rule out other conditions so a diagnosis of ADEM can be made.

Electroencephalogram (EEG)

Your clinician may recommend an EEG to look for abnormal brain activity, such as seizures. While it’s not used to diagnose ADEM directly, it can give clues about your brain function, aiding in diagnosis.

Exclusion of other conditions

Excluding other conditions, such as brain infections, diseases that damage nerves (like multiple sclerosis), or brain tumours, is important as it helps your doctor arrive at a final diagnosis of ADEM and provide the right treatment.

Review recent infections or vaccinations

Finally, a thorough review of your recent medical history is essential. ADEM often happens after viral infections (such as influenza, measles, or varicella) or vaccinations. Understanding the relationship between these events and the onset of your symptoms is vital for confirming the diagnosis of ADEM.

Causes of ADEM

Experts aren’t always exactly sure what causes ADEM, but there are several possible causes, including:

Infections

Studies suggest (2019) that between half and three-quarters of ADEM cases are triggered by viral or bacterial infections. Viral infections that trigger the onset of ADEM symptoms include:

• Common viral infections such as measles, mumps, and rubella, particularly in unvaccinated people

• Herpes simplex virus, often following encephalitis

• Epstein-Barr virus

• Coxsackie virus, particularly in children

• Dengue virus

• COVID-19  

Although rarer, certain bacterial infections have been linked to triggering ADEM, including:

• Mycoplasma pneumonia, the bacteria responsible for walking pneumonia

• Borrelia burgdorferi, the bacteria that causes Lyme disease

• Streptococcus, which causes strep throat, pneumonia, and other illnesses

• Rickettsia, bacteria transmitted by ticks, fleas, and lice

Reaction to a vaccination

Certain vaccinations can trigger an autoimmune response that leads to demyelination, although experts think this may account for fewer than 5% of ADEM cases. Vaccines associated with ADEM development are hepatitis B, Japanese B encephalitis, measles, mumps, pertussis, polio, rubella, tetanus and rabies.

Autoimmune mechanisms

In ADEM, the immune system mistakenly attacks the body's myelin due to a process called molecular mimicry. After an infection, the immune system targets the virus or bacteria, but sometimes the antigens (proteins) on these invaders are similar to the body’s myelin proteins. 

This confusion leads the immune system to attack the myelin, causing the damage and inflammation that results in ADEM. The immune response causes demyelination, which disrupts nerve function and leads to the neurological symptoms seen in the condition.

Genetic and environmental factors

Some people may have a genetic predisposition to autoimmune responses, although experts still don't understand exactly why. Environmental factors, such as the time of year, can also play a part. Respiratory infections are more common in the colder months, which causes a rise in ADEM.

Prognosis and Treatment For ADEM

ADEM generally has a positive outlook, with most children fully recovering. In adults, the prognosis is not always as good, and they may have lasting neurological issues, such as cognitive problems or difficulties with movement. 

How well a person recovers depends on how severe the symptoms are at the start, how much of the nervous system is affected, and how quickly treatment begins.

ADEM is usually restricted to a single episode following infection. However, some patients with ADEM may have a relapse in the future. It’s more common in children, affecting around one in three, and it’s called multiphasic disseminated encephalomyelitis (MDEM). 

The primary treatment for ADEM is high-dose corticosteroids, usually given intravenously for three to five days. Steroids help reduce inflammation and promote recovery during the early stages of the disease.

If steroids don't work well enough, doctors will recommend another treatment called intravenous immunoglobulin (IVIG).  If symptoms don't improve, a treatment called plasma exchange (plasmapheresis) may be considered, where harmful antibodies and other inflammatory substances are removed from the blood.

Your clinician may also recommend treatment to help with the symptoms of ADEM, such as medication to control seizures and physical therapy for patients with movement problems.

In severe cases where swelling in the brain causes too much pressure, lifesaving surgery may be needed to help relieve pressure on the brain.

It’s also crucial that patients with ADEM are carefully and regularly monitored during their recovery to catch any potential relapses or complications early. It’s especially important for children, who may need ongoing support as they grow.

Differential Diagnosis From ADEM

It’s important to rule out other conditions with symptoms that are similar to ADEM, including:

• Multiple sclerosis (MS): MS causes recurring neurological problems. However, symptoms tend to repeatedly flare up and then improve, while ADEM typically happens just once. MRI in MS shows specific patterns around the brain’s ventricles, which helps tell it apart from ADEM.

• Neuromyelitis optica spectrum disorder (NMOSD): NMOSD causes inflammation similar to ADEM, but it has specific antibodies that are not present with ADEM. Clinicians will test for these antibodies to help distinguish NMOSD from ADEM.

• Viral encephalitis: Viral encephalitis causes symptoms similar to ADEM but usually progresses faster and shows more infection signs in the brain. Testing the cerebrospinal fluid (CSF) with a lumbar puncture can help to differentiate the two conditions.

• Acute necrotising encephalitis of childhood (ANEC): ANEC also has rapid neurological symptoms like ADEM, but it’s linked to viral infections, such as herpes simplex. MRI in ANEC often shows brain tissue damage, which helps distinguish it from ADEM.

• Autoimmune encephalitis: This condition causes the immune system to attack the brain, resulting in confusion and seizures, similar to ADEM. However, doctors will look for specific blood antibodies or CSF antibodies to confirm autoimmune encephalitis.

• Balo's disease: Balo's disease is a rare and severe form of demyelination that causes sudden neurological problems like ADEM. However, it develops more slowly, and shows up very differently on MRI, so doctors can distinguish it from ADEM.

• Other conditions: Conditions like cerebral venous sinus thrombosis (CRST), mitochondrial encephalopathy, and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) can mimic ADEM, but they have distinct causes and will show up differently on MRI. 
  

Why an MRI Scan is a Good Option

An acute disseminated encephalomyelitis MRI is considered the gold standard for diagnosing ADEM. MRI findings will help identify signs of demyelinating disorders, such as ADEM or spinal cord inflammation (transverse myelitis), and rule out other causes. 

MRI can also help your doctor detect and track how much damage ADEM has caused the brain and spinal cord, which will help determine your treatment. It’s non-invasive, and results are ready in hours or days, which is particularly helpful in urgent cases of ADEM as the condition can progress rapidly.

How an MRI Scan Detects ADEM

An MRI scan uses magnets and radio waves to create detailed brain and spinal cord images. It relies on the magnetic properties of hydrogen atoms in your body's water molecules, which align when exposed to a magnetic field. When the MRI machine applies radiofrequency pulses, these water molecules shift and emit signals as they return to their original place. These signals create the images you’ll see in your MRI results.

In the case of ADEM, MRI detects areas where the myelin, the protective covering of nerve cells, has been damaged. 

Find an MRI Scan for Acute Disseminated Encephalomyelitis

If you’re worried that you or a loved one have symptoms of ADEM, you can book a private MRI scan today, including a head and brain MRI or a thoracic spine MRI. If you’re unsure whether an MRI is right for you, one of our expert clinicians is available for a personalised consultation. They can discuss your symptoms and concerns and guide you on the best route.

Sources

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Acute disseminated encephalomyelitis (ADEM). (2024). https://radiopaedia.org/articles/acute-disseminated-encephalomyelitis-adem-1?lang=gb 

Acute Disseminated Encephalomyelitis. (2022). https://rarediseases.org/rare-diseases/acute-disseminated-encephalomyelitis/ 

Anilkumar A.C., et al. (2024). Acute Disseminated Encephalomyelitis (ADEM).https://www.ncbi.nlm.nih.gov/books/NBK430934/ 

Balamurugesan K., et al. (2019). An interesting case of acute disseminated encephalomyelitis following E. coli infection. https://journals.lww.com/jfmpc/fulltext/2019/08010/an_interesting_case_of_acute_disseminated.53.aspx 

Chaudry L.A., et al. (2018). Acute disseminated encephalomyelitis: a call to the clinicians for keeping this rare condition on clinical radar. https://www.panafrican-med-journal.com/content/article/29/138/full/