Encephalitis

Definition

Encephalitis is irritation and swelling (inflammation) of the brain, most often due to infections.

See also: Meningitis

Causes

Encephalitis is a rare condition. It occurs more often in the first year of life and decreases with age. The very young and the elderly are more likely to have a severe case.

Encephalitis is most often caused by a viral infection. Many types of viruses may cause it. Exposure to viruses can occur through:

Different viruses will occur in different locations. Many cases will tend to cluster in a certain season.

Encephalitis caused by the herpes simplex virus is the leading cause of more severe cases in all ages, including newborns.

A number of viruses for which there is now a vaccine may also cause encephalitis. These include:

Other viruses that cause encephalitis include:

The virus causes inflammation of brain tissue. The brain tissue swells (cerebral edema), which may destroy nerve cells, cause bleeding in the brain (intracerebral hemorrhage), and brain damage.

Other causes of encephalitis may include:

Symptoms

Some patients may have symptoms of a cold or stomach infection before encephalitis symptoms begin.

When a case of encephalitis is not very severe, the symptoms may be similar to those of other illnesses, including:

Other symptoms include:

Symptoms in newborns and younger infants may not be as easy to recognize:

Emergency symptoms:

Exams and Tests

An examination may show:

Tests may include:

Treatment

The goals of treatment are to provide supportive care (rest, nutrition, fluids) to help the body fight the infection, and to relieve symptoms. Reorientation and emotional support for confused or delirious people may be helpful.

Medications may include:

If brain function is severely affected, interventions like physical therapy and speech therapy may be needed after the illness is controlled.

Outlook (Prognosis)

The outcome varies. Some cases are mild and short, and the person fully recovers. Other cases are severe, and permanent impairment or death is possible.

The acute phase normally lasts for 1 - 2 weeks. Fever and symptoms gradually or suddenly disappear. Some people may take several months to fully recover.

Possible Complications

Permanent brain damage may occur in severe cases of encephalitis. It can affect:

When to Contact a Medical Professional

Go to the emergency room or call the local emergency number (such as 911) if you have:

Prevention

Children and adults should avoid contact with anyone who has encephalitis.

Controlling mosquitoes (a mosquito bite can transmit some viruses) may reduce the chance of some infections that can lead to encephalitis.

Vaccinate animals to prevent encephalitis caused by the rabies virus.

Human vaccinations that are available include:


Review Date: 8/1/2012
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

This information should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. © 1997- 2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.