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Encephalitis

Pronounced: En-sef-uh-light-iss

by Rosalyn Carson-DeWitt, MD


Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention
En Español (Spanish Version)
 

Definition

Encephalitis is inflammation of the brain. The inflammation may involve the whole brain, or just parts of the brain.

Encephalitis

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© 2009 Nucleus Medical Media, Inc.

 

Causes

Viral infection of the central nervous system can be asymptomatic, present with mild symptoms, or cause meningitis and/or encephalitis. Most cases of encephalitis are caused by a viral infection. Encephalitis may be sporadic or epidemic. In the United States, the most common cause of sporadic encephalitis is the herpes simplex virus. Epidemic encephalitis are usually mosquito- or tick-borne, which may be dependant on the geography and season.

The most common viruses that cause encephalitis include:

  • Viruses carried by mosquitoes such as West Nile virus
  • Chickenpox virus
  • Herpes simplex virus
  • Polio virus
  • Epstein-Barr virus
  • Measles virus
  • Mumps virus
  • Rotavirus
  • Influenza virus
  • Rabies
  • Enterovirus

 

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors for encephalitis include:

  • Living, working, or playing in an area where mosquito-borne viruses are common
  • Not being immunized against diseases such as:
    • Measles
    • Mumps
    • Chickenpox
    • Polio
  • Having cancer
  • Taking immunosuppressive medicines after organ transplant
  • Having AIDS

Newborns of mothers who have genital herpes simplex are at risk for herpes simplex encephalitis.

 

Symptoms

The symptoms may range from mild, such as fever and headache, to severe, such as seizures, loss of consciousness, and permanent neurological damage. Death may also result.

Symptoms include:

  • Fever
  • Weakness, severe fatigue
  • Headache
  • Sensitivity to light
  • Stiff neck and back
  • Vomiting
  • Changes in consciousness
  • Muscle aches
  • Rash
  • Personality changes
  • Confusion
  • Irritability
  • Seizures
  • Partial or complete paralysis
  • Progressive drowsiness
  • Yawning
  • Trouble walking
  • Trouble speaking
  • Trouble swallowing

 

Diagnosis

The doctor will ask about your symptoms and medical history, and do a physical exam.

Tests may include:

  • Blood tests—to look for signs of infection
  • Spinal tap—to test spinal fluid for signs of infection
  • CT and/or MRI scans of the head—to look for abnormal areas of enhancement, hemorrhage, or edema in the brain
  • Electroencephalogram (EEG)— to look for abnormal electrical activity in the brain
  • Brain biopsy—removal of a small sample of brain tissue to test for signs of infection

 

Treatment

Treatment is mostly supportive. It may include:

  • Antiviral drugs (eg, 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

 

Prevention

Make sure that you and your children are vaccinated against preventable viral illnesses.

 RESOURCES:

Encephalitis Information Resource
http://www.encephalitis.info/

National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov/

 CANADIAN RESOURCES:

Canadian Neurological Sciences Federation
http://www.ccns.org/

Health Canada
http://www.hc-sc.gc.ca/index-eng.php/

REFERENCES:

Cecil RL, Goldman L, Bennett JC. Cecil Textbook of Medicine. 21st ed. Philadelphia, PA: WB Saunders Company; 2000.

Conn HF, Rakel RE. Conn's Current Therapy 2001. 53rd ed. Philadelphia, PA: WB Saunders Company; 2001.

Herpes simplex encephalitis. EBSCO Publishing DynaMed website. Available at: http://www.ebscohost.com/dynamed/. Updated December 2, 2007. Accessed February 23, 2008.

Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 6th ed. New York, NY: Churchill Livingstone; 2004.

Rosen P, Barkin RM, Danzl DF, et al. Emergency Medicine: Concepts and Clinical Practice. 4th ed. St. Louis, MO: Mosby-Year Book; 1999.

Samuels MA, Feske SK. Office Practice of Neurology. Philadelphia, PA: Churchill Livingstone; 2003.



Last reviewed October 2009 by Rimas Lukas, MD
Last Updated: 10/26/2009

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