Encephalitis is inflammation of the brain. The inflammation 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:
Viruses carried by mosquitoes such as
Eastern equine encephalitis
Herpes simplex virus
Epstein-Barr virus (EBV)Polio
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- or tick-borne viruses are common.
Not being immunized against diseases, such as:
A suppressed immune system caused by certain medications, or health conditions, such as
HIV infectionHaving cancer—sometimes immune system overactivity may be the first sign of cancer
Newborns of mothers who have
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: FeverWeakness, severe fatigueHeadacheSensitivity to lightStiff neck and backVomitingMuscle achesRashYawning
More severe symptoms may include: Changes in consciousnessPersonality changesConfusionIrritabilitySeizuresLoss of mobility
Progressive drowsinessTrouble walkingTrouble speakingTrouble swallowing
You will be asked about your symptoms and medical history. A physical exam will be done.
Your bodily fluids may be tested. This can be done with: Blood testsLumbar puncture
to test the cerebrospinal fluid that surrounds the brain and spinal cord
Images may be taken of your head. This can be done with: CT scanMRI scan
Your brain's electrical activity may be tested. This can be done with an electroencephalogram (EEG).
Treatment is mostly supportive. It may include: Antiviral drugs to shorten the duration of the illnessSteroids to reduce brain inflammationDiuretics to decrease elevated intracranial pressureIntubation with hyperventilation to decrease elevated intracranial pressure, and to maintain respiration and ventilationAnticonvulsants to prevent and/or treat seizures
To help reduce your chance of encephalitis: Make sure that you and your children are vaccinated against preventable viral illnesses
Protect yourself from mosquito bites:
Fix window screens.Drain standing water around your home.Wear long clothes after dark.Use repellent when you are outside.Use proper mosquito netting at night. Look for netting treated with insecticide.
Mann AP, Grebenciucova E, Lukas RV. Anti-N-methyl-D-aspartate-receptor encephalitis: diagnosis, optimal management, and challenges. Ther Clin Risk Manag. 2014;10:517-525.
Nicholas MK, Lukas R, van Besein K. Youmans Textbook of Neurological Surgery, 6th Edition. Section II: General Neurosurgery. Chapter 46. AIDS. 2011.
NINDS meningitis and encephalitis information page. National Institute of Neurologic Disorders and Stroke website. Available at:
http://www.ninds.nih.gov/disorders/encephalitis_meningitis/encephalitis_meningitis.htm. Updated April 16, 2014. Accessed September 23, 2014.
Last reviewed August 2015 by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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