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Encephalitis is uncommon but is a neurological emergency which must be considered in a patient presenting with altered consciousness. Encephalitis is a diffuse inflammatory process of the brain parenchyma associated with evidence of brain dysfunction. The presentation of encephalitis can be acute or chronic. The aetiology of encephalitis can be broadly divided into two major subtypes. (1) Infection-related encephalitis which is a direct consequence of pathogenic viral, bacterial or parasitic.agents. Herpes simplex virus (HSV) and varicella-zoster virus (VZV) are the most common cause of acute infectious encephalitis. (2) Autoimmune-mediated encephalitis which is mediated by an aberrant immune response. This can be triggered by a recent viral infection or vaccination. An example of this would be acute disseminated encephalitis (ADEM). This article will focus on the medical management of acute encephalitis. This will involve an extensive overview of the literature reviewing the diagnosis, investigation and treatment of acute viral encephalitis, ADEM and acute haemorrhagic leukoencephalopathy (AHLE). Encephalitis can also present chronically, and some of the different types of chronic encephalitis will be discussed.

Encephalitis is a brain inflammation that occurs due to an infection such as a virus or bacteria, medication or immune system malfunction. Encephalitis is a rare, often serious condition that requires timely care.


You’ll likely experience physical and neurologic symptoms.

Physical symptoms may include:



Joint pain.

Muscle weakness.


Stiff neck.

Neurologic encephalitis symptoms may include:

Behavior changes.


Difficulty speaking or moving.

Loss of consciousness.

Memory issues.


Sensitivity to light.


The type of encephalitis you experience depends on the cause. And there are many causes, including:

Viruses: Infections from herpes, enteroviruses, human immunodeficiency virus (HIV), West Nile and tick-borne viruses lead to viral encephalitis. This is the most common cause.

Problem with the immune system: The immune system can mistakenly attack the brain, causing autoimmune encephalitis.

Bacteria and parasites: On rare occasions, these germs can cause bacterial encephalitis.

Risk factors

In general, young children and older adults are at greater risk of most types of viral encephalitis. Weakened immune system. People who have HIV/AIDS, take immune-suppressing drugs or have another condition causing a weakened immune system are at increased risk of encephalitis.

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Older adults and those who do not receive prompt treatment have a higher risk of developing complications.

Complications may include:

Loss of memory, especially among those who had HSV encephalitis

behavioral or personality changes, such as mood swings, bouts of frustration and anger, and anxiety


aphasia, language, and speech problems


The best way to prevent viral encephalitis is to take precautions to avoid exposure to viruses that can cause the disease. Try to: Practice good hygiene. Wash hands frequently and thoroughly with soap and water, particularly after using the toilet and before and after meals.

Vaccines are an important part of preventing encephalitis. Vaccines for viruses such as measles, mumps, rubella, and chickenpox have greatly lowered the rate of encephalitis from these diseases. Use proper hygiene and hand washing to help prevent the spread of viruses and encephalitis.

Keeping up to date with vaccines is the most effective way of reducing the risk of developing encephalitis. These include vaccines for measles, mumps, rubella, and if the virus exists in a person’s area, Japanese encephalitis and tick-borne encephalitis.

In areas known to have mosquitoes that carry encephalitis-causing viruses, individuals should take measures to reduce the risk of being bitten.