| Risk Factors
Encephalitis is swelling of the brain. The swelling may involve the whole brain, or just parts of the brain. Encephalitis may just occur in individuals (sporadic) or may affect many people in a particular area (epidemic).
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Encephalitis is most often caused by a viral infection. In the United States, the most common cause of sporadic encephalitis is the
herpes simplex virus (HSV). Epidemic causes of encephalitis are usually
or tick-borne viruses.
The most common viruses that cause encephalitis include:
Not all encephalitis is caused by a virus. Some may be due to an overreaction of the immune system.
Factors that may increase your chance of encephalitis include:
- Living, working, or playing in an area where mosquito-borne viruses are common
Not being immunized against diseases such as:
- Taking immunosuppressive medicines after organ transplant
Newborns of mothers who have
genital herpes simplex
are at risk for herpes simplex encephalitis.
The symptoms may range from mild to severe. Severe symptoms can include permanent neurological damage. Encephalitis can also lead to death.
Milder symptoms include:
- Weakness, severe fatigue
- Sensitivity to light
- Stiff neck and back
- Muscle aches
More severe symptoms may include:
- Changes in consciousness
- Personality changes
Partial or complete
- Progressive drowsiness
- Trouble walking
- Trouble speaking
- Trouble swallowing
The doctor will ask about your symptoms and medical history. A physical exam will be done.
Tests may include:
- Blood tests—to look for signs of infection
Spinal tap (lumbar puncture)—to test cerebrospinal fluid (CSF) for signs of infection
scans of the head—to look for abnormal areas of enhancement, hemorrhage, or edema in the brain
to look for abnormal electrical activity in the brain
biopsy—removal of a small sample of brain tissue to test for signs of infection
Treatment is mostly supportive. It may include:
- Antiviral drugs (such as intravenous acyclovir for herpes simplex encephalitis)—to potentially help shorten the duration of the illness
- Steroid medicines—to decrease brain swelling
- Diuretics such as mannitol—to decrease elevated intracranial pressure
- Intubation with hyperventilation—to decrease elevated intracranial pressure and to maintain respiration and ventilation
- Anticonvulsant medicines—to prevent and/or treat seizures
Make sure that you and your children are vaccinated against preventable viral illnesses.