What are the other Names for this Condition? (Also known as/Synonyms)

• ADEM (Acute Disseminated Encephalomyelitis)
• Immune-Mediated Encephalomyelitis
• Post-Infectious Encephalomyelitis

What is Acute Disseminated Encephalomyelitis? (Definition/Background Information)

• Acute Disseminated Encephalomyelitis (ADEM) is an acute demyelinating disorder that affects the brain and spinal cord. It is considered to be an autoimmune disorder resulting in inflammation in various areas of the central nervous system (brain and spinal cord)
• The condition predominantly occurs in children. individuals usually exhibit signs and symptoms related to sudden onset neurologic deficits. The neurologic deficits can affect different parts of the body
• In most cases, with prompt diagnosis and adequate treatment, the prognosis of Acute Disseminated Encephalomyelitis is good (particularly in children); no long-term damage is noted in most cases. However, in some, long-term neurological damage has been reported

Who gets Acute Disseminated Encephalomyelitis? (Age and Sex Distribution)

• According to reports, the incidence of Acute Disseminated Encephalomyelitis is between 2.3 to 4 cases per million population, making it a very rare condition
• Most cases are noted in children below age 10, although it can affect adults too. The mean age of onset is between 4 to 7 years
• Both males and females may be affected; but, a greater number of cases are reported in girls than boys
• Worldwide, individuals of all races and ethnicity are prone to developing the condition. However, the condition is less common in the tropical regions of the world

What are the Risk Factors for Acute Disseminated Encephalomyelitis? (Predisposing Factors)

The most significant risk factor for developing Acute Disseminated Encephalomyelitis is an antecedent viral or bacterial infection (i.e., history of viral, bacterial, and parasitic infections). The following pathogens are associated with ADEM:

• Viral:
  • Coxsackie B
  • Cytomegalovirus (CMV)
  • Dengue
  • Enterovirus
  • Epstein-Barr virus (EBV)
  • H1N1
  • Hepatitis A and hepatitis C
  • Herpes simplex virus (HSV)
  • HIV
  • Human herpesvirus 6 (HHV-6)
  • Influenza
  • Measles
  • Rubella
  • Varicella zoster virus
  • West Nile virus
• Bacterial:
  • Beta-hemolytic Group-A Streptococcus
  • Borrelia burgdorferi
  • Campylobacter jejuni
  • Chlamydia pneumoniae
  • Legionella pneumoniae
  • Leptospira spp.
  • Mycoplasma pneumoniae
• Parasitic:
  • Falciparum malaria
  • Vivax malaria
  • Toxoplasmosis spp.
• Some cases of ADEM are known to be associated with the following vaccines:
  • Diphtheria pertussis tetanus (DPT)
  • H1N1
  • Hepatitis B
  • Human papilloma virus (HPV)
  • Influenza
  • Japanese encephalitis
  • Measles mumps and rubella (MMR)
  • Meningococcal
  • Oral polio
  • Rabies
  • Smallpox
  • Tetanus toxoid
  • Yellow fever
• Individuals who have undergone transplant surgery
• Poisoning from the jequirity bean or rosary pea plant (Abrus precatorius)
• The condition appears to be more common in winter and spring

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Acute Disseminated Encephalomyelitis? (Etiology)

The exact cause of Acute Disseminated Encephalomyelitis (ADEM) is unknown. 

• It is considered be an autoimmune disorder that occurs following an infection or vaccination. The condition may be a part of post-vaccination CNS demyelination syndromes

·In ADEM, an abnormal inflammation of the brain and spinal cord causes the destruction of myelin affecting the function of the central nervous system (CNS)

According to medical experts, there is a higher risk for CNS demyelination from the infections, and not from the vaccines that are used against them. The risk for ADEM following vaccination is very low (about 0.1%). Besides, the relationship between vaccination and ADEM is not well understood. Hence, one should not avoid vaccinations, which are particularly essential for children.

What are the Signs and Symptoms of Acute Disseminated Encephalomyelitis?

The signs and symptoms of Acute Disseminated Encephalomyelitis may vary from one individual to another. It may be mild or severe. It is reported that sometimes it is difficult to distinguish between ADEM and multiple sclerosis (MS) early in the condition.

A wide variety of signs and symptoms may be noted, and these include:

• Weakness of the arms and legs
• Headache
• Nausea and vomiting
• Paralysis of the cranial nerves
• Inflammation of the optic nerve causing a set of associated vision symptoms
• Seizures
• Fever
• Ataxia

How is Acute Disseminated Encephalomyelitis Diagnosed?

Acute Disseminated Encephalomyelitis may be diagnosed by the following observations and tests:

• Complete evaluation of medical history and family history, along with a thorough physical exam
• Evaluation of the presenting signs and symptoms
• Neurological examination
• Magnetic resonance imaging (MRI) scan of the brain and spinal cord
• Spinal tap
• Visual evoked potential (VEP) test
• Nerve function test

According to the International Pediatric Multiple Sclerosis Study Group (IPMSSG), the diagnostic criteria for ADEM in children include:

• Multifocal, clinical CNS event with presumed inflammatory demyelinating cause
• Encephalopathy that cannot be explained by fever, systemic illness, or post-ictal fever
• No new clinical and MRI findings 3 months or more after the onset
• Brain MRI is abnormal with changes consistent with demyelination during the acute, 3-month phase

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acute Disseminated Encephalomyelitis?

The complications of Acute Disseminated Encephalomyelitis may include:

• 20-30% may show permanent neurological deficits
• Occasionally, epilepsy may develop in children
• On rare occasion, permanent cognitive impairments resulting in attention deficits and other cognitive abnormalities may take place
• Decreased quality of life
• Rarely, ADEM can progress to multiple sclerosis

How is Acute Disseminated Encephalomyelitis Treated?

Acute Disseminated Encephalomyelitis is usually a self-limiting condition. A spontaneous resolution of the condition has been documented.

• Once a diagnosis is established, immunosuppressive therapy to control autoinflammation is the treatment of choice
• In individuals who do not respond to immunosuppressive therapy, plasma exchange may be considered

How can Acute Disseminated Encephalomyelitis be Prevented?

Currently, there are no methods to prevent Acute Disseminated Encephalomyelitis (ADEM). However, availing early treatment of any viral, bacterial, or parasitic infections, may help lower one’s risk for ADEM.

What is the Prognosis of Acute Disseminated Encephalomyelitis? (Outcomes/Resolutions)

The prognosis of Acute Disseminated Encephalomyelitis is based on its severity, and this can vary from one individual to another.

• The prognosis is generally good in children; most children return to normal neurologic function within 3-6 weeks (in between 60-90% of them)
• Adults with ADEM often tend to have more severe signs and symptoms requiring hospitalization

Additional and Relevant Useful Information for Acute Disseminated Encephalomyelitis:

Please visit our Brain & Nerve Health Center for more physician-approved health information:

https://www.dovemed.com/health-topics/neurological-institute/