Acute Disseminated Encephalomyelitis (ADEM): What It Is, Who It Affects, and How It Is Treated
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
Editorial note: This article is for educational purposes only. It is not medical advice, and it cannot replace evaluation and care from a qualified healthcare professional. If you or your child shows sudden neurological symptoms — confusion, vision loss, or weakness — seek emergency medical care immediately.
TL;DR
Acute disseminated encephalomyelitis (ADEM) is a rare condition in which the immune system mistakenly attacks the myelin coating around nerves in the brain and spinal cord, usually within one to two weeks after a viral or bacterial infection. It is most common in children aged 5 to 8. Most people recover fully or nearly fully after steroid treatment, and the vast majority live a normal lifespan.
Quick Answer: What Is Acute Disseminated Encephalomyelitis (ADEM)?
Acute disseminated encephalomyelitis (ADEM) is a rare, sudden attack of inflammation in the brain and spinal cord that damages myelin — the protective coating around nerve fibers. It usually begins 7 to 14 days after a viral or bacterial infection, most often affects children under 10, and affects roughly 1 in 125,000 to 250,000 people each year. Symptoms include fever, headache, confusion, and neurological problems such as vision loss and muscle weakness. First-line treatment is intravenous steroids, and most patients recover fully or nearly fully within six months.
Why Does ADEM Happen After an Infection?
ADEM is not caused by the germ itself. It happens because the immune system, while fighting off an infection, misfires. Cells and antibodies designed to attack a virus or bacteria mistakenly recognize parts of the myelin sheath — the fatty insulation around nerve fibers — as a threat and attack them instead.
The myelin sheath works like the plastic coating around an electrical wire. When it is damaged, electrical signals traveling along the nerve slow down or misfire, producing the wide range of neurological symptoms seen in ADEM. Because this damage is triggered by the body's own immune response, ADEM is classified as an autoimmune, demyelinating condition.
The exact trigger mechanism is still not fully understood. Researchers believe it may involve immune cells or antibodies that cross-react with myelin proteins such as myelin basic protein. A closely related condition, myelin oligodendrocyte antibody-associated disease (MOGAD), is an increasingly recognized underlying cause of ADEM, particularly in children.
How Common Is ADEM, and Who Gets It?
ADEM is rare. Population studies across the United States and Europe estimate that it affects roughly 1 in 125,000 to 250,000 people each year, which translates to an annual incidence of about 0.07 to 0.9 cases per 100,000 children.
Annual incidence (children): 0.07–0.9 per 100,000 children per year
U.S. prevalence estimate: 1 in 125,000–250,000 people
Nationwide Chinese incidence (2016–2018): 0.054 per 100,000 person-years overall; 0.134 in children vs. 0.038 in adults
Peak age of onset: 5–9 years (0.171 per 100,000 person-years in the China study)
Typical age range: Median 5–8 years; majority under 10; remainder 10–20
Male-to-female ratio: ~1.3:1 (China study: 1.16:1)
Seasonal pattern: Winter and spring peaks, consistent with an infectious trigger
Children under 10 are predominantly affected, though ADEM can occur in adults as well — documented cases range from 18 to 82 years old. Most studies find a slight male predominance, and cases cluster in winter and spring, when respiratory viral infections are most common.
Europe: 0.07–0.51 per 100,000 children (population study)
North America: 0.2–0.6 per 100,000 children (population study)
Japan: ~0.4 per 100,000 children (population study)
United States: 1 in 125,000–250,000 per year (clinical reference)
What Are the Symptoms of ADEM?
Symptoms usually appear one to two weeks after a viral or bacterial illness, and their severity varies widely from person to person.
Constitutional (whole-body): Fever, headache, nausea or vomiting, fatigue, malaise
Mental status: Confusion, irritability, drowsiness, altered behavior; in severe cases coma
Sensory: Numbness or tingling in the arms and legs
Vision: Vision loss from optic neuritis
Motor: Muscle weakness, difficulty walking, paraparesis or tetraparesis
Brainstem and other: Difficulty swallowing, seizures, unsteady gait (ataxia)
A defining feature of ADEM is encephalopathy — an altered mental state such as confusion, irritability, or extreme sleepiness. International pediatric diagnostic criteria require both encephalopathy and multiple (polyfocal) neurological deficits for a formal ADEM diagnosis.
Symptoms may start mildly but typically worsen rapidly over several hours to four days. That rapid progression is why ADEM requires urgent medical evaluation.
What Causes ADEM? Which Infections Trigger It?
The precise cause is unknown, but research points to an abnormal immune response following an infection. Roughly 70 to 80 percent of people diagnosed with ADEM report a preceding infection, and ADEM symptoms typically begin about 7 to 14 days afterward. Other sources estimate a preceding infection or vaccination in 50 to 85 percent of cases, with a lag time that can range from a few days up to 60 days.
Common viruses: Influenza (flu), measles, mumps, rubella, chickenpox, Epstein-Barr virus, cytomegalovirus, herpes simplex virus
Other organisms reported: HHV-6, hepatitis A, HIV, Mycoplasma pneumonia, and occasionally bacteria such as Leptospira, streptococci, or Borrelia burgdorferi
Vaccination (rare): Reported 8–21 days after immunization, historically most with the older rabies vaccine; far less common with modern vaccines
No identifiable trigger: Around 25 percent of patients have no apparent preceding event
No single infectious agent causes all ADEM cases — many different viruses and bacteria have been associated with it. One increasingly recognized contributor is MOGAD (myelin oligodendrocyte antibody-associated disease), an autoimmune condition in which antibodies attack a specific myelin protein. MOGAD is a particularly important cause to identify in children, because it carries a higher risk of recurrence.
How Is ADEM Diagnosed?
Diagnosis combines a detailed medical history, a neurological examination, and several key tests. Because ADEM can mimic other conditions, testing also looks for underlying causes such as MOGAD.
Medical history: Recent infection or illness; symptom onset and progression
Neurological examination: Weakness, reflex changes, vision problems, altered mental status
MRI of brain and spinal cord: Multiple, widespread lesions in the brain's white and gray matter — the imaging hallmark of ADEM
Spinal tap (lumbar puncture): Increased white blood cells (predominantly lymphocytes) in cerebrospinal fluid
Blood tests: MOG antibodies, markers to rule out other causes
An MRI looks for lesions in three areas of the central nervous system: the brain, the spinal cord, and the optic nerves. Lesions appear in the white matter (myelinated nerve fibers, which appear bright white on basic MRI sequences) and can also involve deep gray matter structures such as the basal ganglia and thalamus. A follow-up MRI months later helps clinicians monitor how the lesions change over time.
Because encephalopathy is required for diagnosis, a key distinction doctors must make is between ADEM and the first episode of multiple sclerosis (MS). ADEM typically shows large, widespread, asymmetric lesions and monophasic (single-event) illness, while MS shows more localized lesions and a relapsing course.
How Is ADEM Treated?
Treatment focuses on calming the immune attack and reducing inflammation in the brain and spinal cord as quickly as possible.
Intravenous corticosteroids: High-dose IV steroids rapidly suppress inflammation. First-line treatment; may require more than one infusion followed by oral steroids
Intravenous immune globulin (IVIG): Antibodies from donor plasma given through an infusion. Used when steroids are not enough
Plasmapheresis (plasma exchange): Blood is cycled through a machine that removes immune components. Reserved for steroid-refractory cases
Side effects are usually temporary. Short-term steroid therapy can cause elevated blood glucose, low potassium, difficulty sleeping, mood changes, weight gain, flushed cheeks, or a metallic taste. IVIG may cause allergic reactions, headaches, blood clots, or kidney injury, and plasmapheresis carries risks of bleeding, infection, and low blood pressure.
How Long Does Recovery Take, and What Is the Outlook?
Most people begin to feel better within a few days of finishing treatment, and full recovery can take up to six months, depending on how severe the initial attack was.
Overall recovery: Most patients make a full or nearly complete recovery
Time to recovery: Average 1–6 months (Orphanet); up to 6 months (Cleveland Clinic)
Relapse rate: 5–25% of cases relapse, usually 6–18 months after onset — higher when MOGAD underlies the ADEM
Hospital mortality: ~1.7% in a nationwide 3-year Chinese study; annual child mortality fell from 3.0% to 0.8%
Life expectancy: Normal for the majority of patients
The picture is somewhat different for adults. Most studies find that adults have worse outcomes than children, with fewer achieving complete motor recovery and a higher risk of residual deficits. A 2022 outcomes study found an overall mortality of 7.8 percent in its cohort, driven largely by adult cases.
Some symptoms may linger after treatment, including severe headaches, numbness, trouble with coordination, and blurry vision. In very rare cases, severe inflammation is life-threatening.
Can ADEM Be Prevented?
There is no way to prevent ADEM directly. Because most cases follow an infection, general infection-reduction habits — good hand hygiene, avoiding sick contacts, and staying current on routine vaccinations — are the practical way to lower risk. Notably, modern vaccines are far less likely than past formulations to trigger ADEM, and the infectious diseases that vaccines prevent were historically much stronger ADEM triggers.
Living With ADEM: What You Should Know
Most people experience only a single ADEM attack. Because recurrence is possible — especially when MOGAD is the underlying cause — follow-up care with a neurologist matters. A repeat MRI months after the attack helps the clinical team confirm that lesions are resolving and not evolving into another condition such as MS.
Questions worth asking your healthcare team include how to prepare for diagnostic testing, what treatment approach they recommend, which side effects to watch for, and whether your symptoms are expected to persist after treatment.
When Should You Seek Immediate Medical Care?
ADEM can develop quickly. Seek emergency care — call 911 or go to the nearest emergency department — if you or your child develops any of the following, especially within one to two weeks of an infection:
Sudden confusion or unusual drowsiness: Encephalopathy is a hallmark of ADEM
New vision loss or double vision: Optic nerve inflammation is common
New weakness in arms or legs, or difficulty walking: Spinal cord and brain involvement
Numbness or tingling spreading through limbs: Demyelination in sensory pathways
Seizures: A recognized neurological symptom
Difficulty swallowing or breathing changes: Brainstem involvement
The Bottom Line
Acute disseminated encephalomyelitis is a rare but serious immune-driven attack on the myelin of the brain and spinal cord, usually arriving one to two weeks after a common infection. It is overwhelmingly a childhood condition — peaking around ages 5 to 9 with a slight male predominance — and it strikes in winter and spring alongside the viral seasons.
The encouraging news is substantial: with prompt treatment using intravenous steroids (and, when needed, IVIG or plasma exchange), most people recover fully or nearly fully within six months, maintain a normal life expectancy, and never have a second attack.
Talk to a neurologist if you or your child has unexplained neurological symptoms after an illness — early treatment gives the best chance of a full recovery.
Frequently Asked Questions (FAQ)
1. What is the difference between ADEM and multiple sclerosis?
ADEM is typically a single (monophasic) attack that follows an infection, with large, widespread lesions on MRI and required encephalopathy. MS is a chronic condition with repeated relapses over time and more localized lesions. About 5–25 percent of ADEM patients relapse, and those cases are more often linked to MOG antibody disease.
2. Is ADEM contagious?
No. ADEM itself is not contagious — you cannot "catch" it from someone who has it. What can spread is the underlying viral or bacterial infection that may have triggered the immune response.
3. Can adults get ADEM?
Yes, though it is much less common. Most cases occur in children aged 5–8, but ADEM has been documented in adults from ages 18 to 82. Adults generally have a worse prognosis than children.
4. How long does it take to recover from ADEM?
Most people feel better within a few days of finishing steroid treatment, but full recovery typically takes up to six months depending on the severity of the attack.
5. Does ADEM come back?
Most people have only one attack. Relapse occurs in roughly 5–25 percent of cases, usually 6–18 months after the first episode, and is more likely when MOG antibody disease is the underlying cause.
6. Is ADEM the same as encephalitis?
No. Encephalitis is direct inflammation of brain tissue caused by an infection in the brain. ADEM is an immune-mediated demyelinating process that usually follows (not accompanies) an infection elsewhere in the body.
7. Can a vaccine cause ADEM?
Historically, ADEM was reported after certain vaccines — most notably older rabies vaccine formulations — typically 8 to 21 days afterward. The risk with modern vaccines is extremely low (about 1–2 cases per million doses for measles-containing vaccines), and vaccines have made ADEM-favoring infections like measles far less common.
8. What is MOG antibody disease (MOGAD), and how is it related to ADEM?
MOGAD is an autoimmune condition in which antibodies attack the myelin oligodendrocyte glycoprotein. It is an increasingly recognized cause of ADEM in children and is associated with a higher chance of relapse, making MOG antibody testing important in follow-up care.
References
Cleveland Clinic — Acute Disseminated Encephalomyelitis (ADEM) (medically reviewed, last updated 05/30/2023)
StatPearls, National Institutes of Health — Acute Disseminated Encephalomyelitis (last updated January 26, 2024)
Orphanet — Acute Disseminated Encephalomyelitis
Neuroscience Bulletin, 2021 — Incidence and Mortality of Acute Disseminated Encephalomyelitis in China: A Nationwide Population-Based Study
Transverse Myelitis Association — Acute Disseminated Encephalomyelitis (ADEM)
2022 — Clinical Presentation and Outcomes of Acute Disseminated Encephalomyelitis
Children (MDPI), 2021 — Update on Acute Disseminated Encephalomyelitis in Children
NIH Genetic and Rare Diseases Information Center — Acute Disseminated Encephalomyelitis
National Institute of Neurological Disorders and Stroke (NINDS) — Acute Disseminated Encephalomyelitis
National Organization for Rare Disorders (NORD) — Acute Disseminated Encephalomyelitis
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