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Viral encephalitis

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of viral encephalitis.

Alternative Names

West Nile virus

Prognosis

In most cases of arbovirus infection, symptoms are mild, last 3 - 5 days, and resolve without becoming serious. In fact, the infection is generally unrecognized as anything other than a mild flu.

Prognosis for Severe Encephalitis

Prognosis for severe encephalitis depends on a host of factors such as the following:

• The age of the patient -- worse outcomes for infants under age 12 months and adults over age 55
• Immune status
• Preexisting neurological conditions
• Virulence of the virus

Death From Suppression of Vital Functions

In severe cases of encephalitis, the swelling of the brain inside the skull places downward pressure on the brain stem. The brain stem controls vital functions such as respiration and heartbeat, and if the pressure becomes too severe, these vital functions can cease and cause death.

Effects of Coma

Coma is a common symptom in patients with severe encephalitis, but does not necessarily predict a fatal or severe outcome. In one study of Eastern equine encephalitis, some survivors averaged 5 days in a coma and had no or only mild to moderate complications afterward. One patient was in a coma for 9 days and had only mild complications afterward.

Complications from Brain Damage

Survivors of encephalitis commonly experience neurologic consequences, which can be very long-term and even permanent. The degree and type of brain damage can vary from mild-to-severe and from focal (in one part of the brain) to multifocal (several parts of the brain) to diffuse (throughout the brain).

The location and severity of the infection largely determines the pattern of brain damage and therefore its effects, which can be:

• Physical (muscle control)
• Behavioral and emotional (personality changes)
• Cognitive (memory, speech)
• Sensory (vision, hearing)
• Some patients who experience memory problems and personality changes afterward describe their condition as being an "invisible disease." They appear to be normal to others, but they are plagued with forgetfulness and lapses in attention that has a considerable affect on the quality of their daily lives. Helpful support groups are now available on the Internet.

• Review Date: 1/18/2007
• Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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