Acute Disseminated Encephalomyelitis: Symptoms, Types, Causes and Treatment

Acute Disseminated Encephalomyelitis (ADEM) is a rare but significant neurological condition, especially in children. Understanding its symptoms, variations, causes, and treatments is crucial for early recognition and effective intervention. This article provides a comprehensive, evidence-based overview, making complex medical information accessible and actionable.

Symptoms of Acute Disseminated Encephalomyelitis

ADEM can present suddenly, often leaving patients and families alarmed by the rapid onset of neurological symptoms. Recognizing these signs early is essential for timely treatment and improved outcomes.

Symptom	Description	Prevalence/Note	Source(s)
Ataxia	Loss of coordination/balance	Most common in children	1 6
Encephalopathy	Altered mental state, confusion, drowsiness	Frequent & defining feature	2 3 4 6
Fever	Elevated temperature	Often precedes neurological	3 4 6
Headache	Head pain or pressure	Common at onset	3 14
Vomiting	Nausea and emesis	Seen in many cases	3 14
Seizures	Involuntary convulsions	Possible, especially in severe cases	8
Weakness	Motor deficits; hemiparesis	Unilateral/bilateral	6
Visual Loss	Decreased vision (optic nerve involvement)	May indicate higher risk of disability	6
Fatigue	Profound tiredness	Frequently reported	3
Polyfocal Deficits	Multiple neurologic impairments	Hallmark of ADEM	2 4

Table 1: Key Symptoms of ADEM

Understanding ADEM Symptoms

ADEM often develops suddenly, typically days to weeks after a triggering event such as an infection. The clinical picture is dominated by encephalopathy—a global brain dysfunction manifesting as confusion, drowsiness, or even coma, which helps distinguish ADEM from other demyelinating diseases like multiple sclerosis (MS) 2 3 4 6.

Neurologic Features

• Ataxia (loss of coordination) is particularly common, especially in children, and may be the first noticeable sign 1.
• Motor deficits such as hemiparesis (weakness on one side) or bilateral long tract signs are often pronounced 6.
• Visual loss can occur if the optic nerves are involved; this may predict greater long-term disability 6.

Systemic and Nonfocal Symptoms

• Fever, headache, vomiting, and fatigue commonly accompany the neurologic symptoms, often making ADEM appear similar to viral encephalitis at first 3 4 14.
• Seizures and altered consciousness may signal more severe disease or younger age at onset 8 13.

Variability and Course

Symptoms tend to develop over several days and can vary depending on which areas of the brain and spinal cord are affected 1 7. The severity and combination of symptoms often differ from person to person.

Types of Acute Disseminated Encephalomyelitis

While ADEM is mostly seen as a single-episode illness, there are important variants that affect prognosis and management. Understanding these types helps clinicians tailor their approach and informs patient expectations.

Type	Definition/Features	Frequency/Notes	Source(s)
Monophasic	Single episode, no recurrence	Most common, >85-90% of cases	2 4 6 10
Multiphasic	Two or more episodes, separated in time	10-15% of pediatric cases	2 6 10
Acute Hemorrhagic	Severe, with brain hemorrhages	Rare variant, poor prognosis	6
Post-infectious	Follows infection (esp. viral)	Classic presentation	4 5 9
Post-vaccination	Follows immunization	Less common, recognized trigger	1 5 9

Table 2: Main Types of ADEM

Exploring the Types

ADEM is not a one-size-fits-all disease. Its manifestations can be categorized based on the number of episodes, triggers, and severity.

Monophasic ADEM

• Monophasic ADEM refers to a single episode of demyelination with no further relapses. This is by far the most common form, especially in children 2 4 6.
• Patients typically recover fully or with minimal sequelae, especially with prompt treatment 1 6.

Multiphasic (Recurrent) ADEM

• Multiphasic ADEM (also called recurrent or relapsing ADEM) involves a second or subsequent episode of neurologic symptoms, separated by at least three months from the first, often with new MRI lesions 2 6 10.
• This form represents about 10–15% of pediatric ADEM cases 6.
• Distinguishing multiphasic ADEM from early MS is important because long-term management strategies differ 2 10.

Acute Hemorrhagic Encephalomyelitis

• A rare and severe variant, acute hemorrhagic encephalomyelitis is characterized by rapid progression, hemorrhagic brain lesions, and a higher risk of poor outcomes or mortality 6.

By Trigger: Post-infectious vs. Post-vaccination

• Post-infectious ADEM occurs after infections, especially viral, and is the classic form seen in most cases 4 5 9.
• Post-vaccination ADEM can follow immunizations, although this is far less common. The latency from vaccination to onset is typically 1–4 weeks 1 5 9 12.

Causes of Acute Disseminated Encephalomyelitis

Understanding the causes of ADEM is key to prevention and early recognition. The disease is believed to be autoimmune, triggered by environmental factors in genetically susceptible individuals.

Cause	Details/Examples	Notes & Risk Factors	Source(s)
Viral Infection	Measles, rubella, chickenpox, influenza, EBV	Most common, especially in children	1 2 4 5
Bacterial Infection	Mycoplasma, others	Less common	5 9
Vaccination	Measles, rabies, hepatitis B vaccines	Rare, latency 1–6 weeks	1 5 9 12
Autoimmunity	Immune attack on CNS myelin	Central to pathogenesis	2 4 11 13
Other	Post-malaria, unknown triggers	Reported in rare cases	8

Table 3: Causes and Triggers of ADEM

What Causes ADEM?

ADEM is fundamentally an autoimmune disease, where the body’s immune system mistakenly attacks its own central nervous system (CNS) myelin—the protective sheath around nerve fibers 2 4 11 13. This leads to widespread inflammation and demyelination, disrupting brain and spinal cord function.

Infectious Triggers

• Viral infections are the leading known triggers. Common viruses include:
  • Measles, rubella, chickenpox (varicella), influenza, Epstein-Barr virus (EBV), adenovirus, cytomegalovirus, and others 1 4 5.
• Bacterial infections may occasionally precede ADEM, but are less commonly implicated 5 9.

Vaccinations

• Some cases of ADEM develop after immunizations, notably those for measles, smallpox, rabies, and hepatitis B 1 5 9 12.
• The risk after vaccination is extremely low compared to the risk after natural infection 12.

Other and Rare Causes

• Rarely, ADEM can follow recovery from diseases like malaria 8.
• In some cases, no clear trigger is identified, and the disease appears spontaneously 13.

Pathophysiology

The prevailing theory is molecular mimicry: the immune system, activated by an infectious agent or vaccine antigen, cross-reacts with myelin proteins in the CNS. This results in inflammation, edema, and demyelination 2 4 7 11.

Treatment of Acute Disseminated Encephalomyelitis

Effective treatment for ADEM is essential to reduce the risk of long-term complications and mortality. The mainstay of therapy is immunosuppression, with additional options available for severe or refractory cases.

Treatment	Description	Outcome/Notes	Source(s)
IV Corticosteroids	High-dose methylprednisolone (20–30 mg/kg/day for 3–5 days), followed by taper	First-line, rapid improvement	1 6 13 16
IV Immunoglobulin (IVIG)	2 g/kg over 2–5 days	For steroid-refractory/intolerant cases	14 15 16
Plasma Exchange	Plasmapheresis in severe cases	Used if poor steroid/IVIG response	16
Supportive Care	Antibacterial/antiviral agents, ICU if needed	While infectious causes ruled out	16
Rehabilitation	Cognitive, motor, visual therapies	For persistent deficits	6 13 16
Surgical Intervention	Decompressive craniectomy for intracranial hypertension	Rare, life-saving	16

Table 4: ADEM Treatment Overview

Approaches to Treatment

The primary goal in ADEM is to quickly halt ongoing inflammation and promote recovery.

First-line: High-dose Steroids

• Intravenous methylprednisolone is the cornerstone of ADEM treatment, typically given for 3–5 days, followed by a gradual oral taper over 4–6 weeks 1 6 13 16.
• Most patients respond rapidly, often with dramatic improvement in symptoms and MRI findings 1 6.
• Early initiation of steroids is associated with better outcomes 1 6.

Second-line: IV Immunoglobulin (IVIG)

• Used in patients who do not respond to steroids or cannot tolerate them 14 15 16.
• IVIG has been shown to promote recovery, sometimes even when steroids fail 14 15.
• Standard dosing is 2 g/kg given over 2–5 days 16.

Third-line: Plasma Exchange

• Plasmapheresis is considered for severe or life-threatening ADEM, especially if both steroids and IVIG are ineffective 16.
• This treatment removes pathogenic antibodies and inflammatory mediators from the blood.

Supportive and Additional Care

• Empirical antibiotics and antivirals may be administered until infectious causes are excluded 16.
• Intensive care support (including ventilation) can be necessary in severe cases.

Rehabilitation

• Patients with residual neurological deficits may require physical, occupational, cognitive, or visual rehabilitation 6 13.

Surgical Intervention

• In cases of increased intracranial pressure with risk of brain herniation, decompressive craniectomy has been used as a life-saving measure 16.

Prognosis

• The outlook is generally favorable, especially in children, with most making a full or near-full recovery 1 2 4 6 13.
• However, some may experience lasting neurocognitive or physical deficits, highlighting the importance of early recognition and intervention 6 13.
• Mortality rates vary in the literature but are now lower with current treatment approaches 5 9 10.

Conclusion

Acute Disseminated Encephalomyelitis remains a complex but increasingly treatable neurological disorder. Early recognition, timely intervention, and understanding its unique features are critical for optimal outcomes.

Key Points:

• ADEM often presents abruptly with encephalopathy, ataxia, motor deficits, and systemic symptoms, most commonly in children 1 2 3 6.
• Most cases are monophasic, but multiphasic and severe (hemorrhagic) forms exist 2 6 10.
• Infections (especially viral) and, less commonly, vaccinations are the main recognized triggers, though the disease is fundamentally autoimmune 1 2 4 5 9.
• First-line treatment is high-dose corticosteroids, with IVIG and plasmapheresis reserved for refractory or severe cases 1 6 14 15 16.
• Prognosis is generally favorable, but some patients may experience long-term neurocognitive or physical sequelae 6 13.
• Early diagnosis and multidisciplinary care are crucial for minimizing disability and maximizing recovery.

By staying informed about ADEM’s varied presentations and advances in therapy, healthcare providers and families can work together to ensure the best possible outcomes for those affected by this challenging condition.