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Understanding Encephalitis: The Basics

Medically Reviewed by Jabeen Begum on September 29, 2021

What Is Encephalitis?

Encephalitis, or inflammation of the brain tissue, is rare, affecting about one in 200,000 people each year in the U.S.

When it strikes, it can be very serious, causing personality changes, seizures, weakness, and other symptoms depending on the part of the brain affected.

Children, the elderly, and those with a weak immune system are most vulnerable. The disease is usually caused by one of several viral infections, so it's sometimes referred to as viral encephalitis.

Most people who have mild encephalitis fully recover. The most appropriate treatment and the patient's chance of recovery depend on the virus involved and the severity of the inflammation.

In acute encephalitis, the infection directly affects the brain cells. In para-infectious encephalitis, the brain and spinal cord become inflamed within one to two weeks of contracting a viral or bacterial infection.

What Causes Encephalitis?

encephalitis

Viral encephalitis may develop during or after infection with any of several viral illnesses including influenza, herpes simplex, measles, mumps, rubella, rabies, chickenpox, and arbovirus infection including West Nile virus.

Herpes simplex type 1 virus is one of the more common and serious causes of viral encephalitis. Herpes-related encephalitis can erupt rapidly, and may cause seizures or mental changes and even lead to coma or death. It occurs when the herpes simplex type 1 virus travels to the brain rather than moving through the body to the surface of the skin and producing its more common symptom, a cold sore. Early recognition and treatment of herpes encephalitis can be life-saving. You are not more likely to get encephalitis if you have cold sores.

Arbovirus encephalitis is another form of viral encephalitis. It is caused by various viruses that are carried by insects (such as mosquitoes and ticks). Unlike herpes, arboviral infections are seasonal, occurring primarily in summer and early fall, and are clustered in specific regions, such as in the case of St. Louis encephalitis.

In rare instances, bacterial, fungal, parasitic, or rickettsial infections cause encephalitis. Cancer or even exposure to certain drugs or toxins may also cause encephalitis.

What Are the Symptoms of Encephalitis?

The symptoms of encephalitis are usually sudden and severe.

They include:

  • Fever
  • Drowsiness, lethargy, and possibly coma
  • Headaches
  • Personality changes, irritability, or emotional outbursts
  • Confusion
  • Weakness in one or more areas of the body
  • Seizures
  • Bulging soft spots in infants

Seek medical attention right away if you or someone else has any of these symptoms.

How Is Encephalitis Diagnosed?

Many clues as to the cause of encephalitis come from an exposure history. Because a person with encephalitis is usually disoriented, family and friends are key to getting a good history. It is important to know if the person may have come into contact with mosquitoes or ticks, infected animals, or sick people.

Your doctor may also order an MRI scan, spinal tap, or electroencephalogram (EEG).

Blood tests to check for bacteria or viruses and the immune cells produced in response to them can also be helpful.

Rarely, an analysis of a brain tissue sample (biopsy) may be necessary to confirm the diagnosis in cases where symptoms are getting worse and treatments aren't working. It can be very important to identify the type of encephalitis in order to give the right treatment.

What Are the Treatments for Encephalitis?

Because complications from encephalitis can be serious, the condition requires hospitalization. Treatment will depend largely on your age and condition, as well as the form and cause of the disease.

If encephalitis is caused by a bacterial infection, it can be treated with intravenous antibiotics. Treatment for herpes-related encephalitis includes supportive care, as well as intravenous antiviral therapy with a drug such as acyclovir. Other treatments may be used to lower fever, provide hydration, treat seizures if they develop, and reduce any pressure in the skull.

With proper care, most people recover from encephalitis. Infants and elderly people are at greater risk of permanent brain damage.

How Can I Prevent Encephalitis?

The elimination of smallpox and the use of vaccines against mumps, measles, and rubella have lowered cases of encephalitis, especially in children.

Vaccines have been developed for people who travel to high-risk areas as well.

Other ways to prevent it are to avoid viruses that can lead to the disease (like herpes) and to protect yourself against mosquito and tick bites.

WebMD Medical Reference

Sources

SOURCES: 

The Mayo Clinic. 

Nemours Foundation.

National Institute of Neurological Disorders and Stroke. 

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