Autoimmune encephalitis (AE) | Acute disseminated encephalomyelitis (ADEM)

Overview

Autoimmune encephalitis (AE) occurs when healthy cells and tissues in the brain or spinal cord are attacked by the body’s immune system, leading to inflammation. AE is a collection of conditions and some types, such as ADEM, can be caused by an infection while other forms are associated with finding specific antibodies in the blood. In most cases, it remains unknown why these antibodies are produced, while in other cases it may be due to the presence of a tumor.

ADEM causes brief but widespread inflammation and demyelination (white matter tissue damage) of the brain and spinal cord. Unfortunately, reviewing the existing medical literature on the topic can prove challenging, given that different terms have been used to describe and define the disorder. “Typically, ADEM is considered a monophasic disorder, which is a disorder that has a single occurrence of one phase in a particular individual.”  However, there is confusion over whether symptomatic recurrences are relapses of ADEM or if they are instead the presentation of other diseases with similar symptoms, such as multiple sclerosis.

Common Symptoms

Fever, headaches, irritability, fatigue, lethargy, malaise, unintended weight loss, nausea, and vomiting, vision loss in one or both eyes, muscle weakness even to the point of paralysis, difficulty coordinating voluntary muscle movements, confusion, stupor, delirium, and potentially coma.

Coexisting Diseases and Conditions

While ADEM does have a lot in common with multiple sclerosis (MS), there are some key differences:

  • In most but not all cases, ADEM occurs only once, while patients with MS have further, repeated attacks of inflammation in their brains and spinal cords.
  • Typical symptoms of ADEM such as fever, headache and confusion, vomiting, and seizures are not usually seen in people with MS, although they can be seen in pediatric MS onset especially in patients younger than 11 years.
  • Sometimes the pattern of MRI abnormalities helps differentiate these two disorders.
  • Most patients with MS are treated with ongoing medication to prevent attacks. Patients with ADEM generally do not require such medication because they do not experience flare-ups.
  • ADEM occurs more frequently in males; MS occurs more frequently in females.
  • ADEM is more common in children; MS is more common in adults.

Risk Factors and Prevalence

Environmental factors, including exposure to viral infections. Currently, it is not believed to be inherited as the NIH has no reports of ADEM occurring in more than one family member.

Sources

  1. Article Sources and Footnotes

    1. U.S. Department of Health and Human Services. (n.d.). Acute Disseminated Encephalomyelitis Information Page. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/All-Disorders/Acute-Disseminated-Encephalomyelitis-Information-Page. 

    2. NORD – National Organization for Rare Disorders, Inc. (2016, June 28). Acute Disseminated Encephalomyelitis. NORD (National Organization for Rare Disorders). https://rarediseases.org/rare-diseases/acute-disseminated-encephalomyelitis/#:~:text=Acute%20disseminated%20encephalomyelitis%20(ADEM)%20is,and%20proteins%20known%20as%20myelin.  

    3. The National Multiple Sclerosis Society. (n.d.). Acute Disseminated Encephalomyelitis (ADEM). National Multiple Sclerosis Society. https://www.nationalmssociety.org/What-is-MS/Related-Conditions/Acute-Disseminated-Encephalomyelitis-(ADEM). 

    4. Tenembaum, S., Chitnis, T., Ness, J., & Hahn, J. S. (2007, April 17). Acute disseminated encephalomyelitis. Neurology. https://n.neurology.org/content/68/16_suppl_2/S23. 

    5. Siegel Rare Neuroimmune Association. (2020, June 26). Acute Disseminated Encephalomyelitis (ADEM): Diagnosis. SRNA. https://wearesrna.org/living-with-myelitis/disease-information/acute-disseminated-encephalomyelitis/diagnosis/.