Encephalitis (en-sef-uh-LI-tis) is inflammation of the brain. Viral infections are the most common cause of the condition.
Encephalitis can cause flu-like symptoms, such as a fever or severe headache, as well as confused thinking, seizures, or problems with senses or movement. Many cases of encephalitis may go unnoticed because they result in only mild flu-like symptoms or even no symptoms. Severe cases of encephalitis, while relatively rare, can be life-threatening.
Because the course of any single case of encephalitis is relatively unpredictable, it's important to get a timely diagnosis and treatment.
Most people with viral encephalitis have either no symptoms or mild flu-like symptoms, such as the following:
More-serious cases require prompt medical care. Signs and symptoms may include the following:
Signs and symptoms in infants and young children may also include:
When to see a doctor
Infants and young children with any signs or symptoms of encephalitis should receive urgent care.
One of the major signs of encephalitis in infants is bulging of the soft spots (fontanels) of the baby's skull. Pictured here is the anterior fontanel. Other fontanels are found on the sides and back ...
The cause of encephalitis is often unknown, but the most commonly diagnosed cause is a viral infection. Known causes of encephalitis may include:
An infection may result in one of two conditions affecting the brain:
Common viral causes
West Nile virus transmission cycle
When a mosquito bites an infected bird, the virus enters the mosquito's bloodstream and eventually moves into its salivary glands. When an infected mosquito bites an animal or a human (host), the ...
Anyone can develop encephalitis. Factors that may increase the risk of the condition include:
The complications resulting from encephalitis depend on several factors, including age, the cause of the infection, the severity of the initial illness and the time from disease onset to treatment.
In most cases, people with relatively mild illness recover within a few weeks with no long-term complications.
Complications of severe illness
Other complications — varying greatly in severity — may persist for many months or be permanent:
Preparing for your appointment
Because the onset of serious illness associated with encephalitis is usually severe and relatively sudden, seek emergency care. The emergency care team will likely include a specialist in disorders of the nervous system (neurologist).
Questions from your doctor
Tests and diagnosis
Questions about symptoms, risk factors and medical history are important in making a diagnosis of encephalitis. Diagnostic tests that may be needed include the following:
Treatments and drugs
Treatment for mild cases mainly consists of:
Some viruses, such as insect-borne viruses, don't respond to these treatments. However, because the specific virus causing the infection may not be identified immediately or at all, treatment with acyclovir is often begun immediately. This drug can be effective against the herpes simplex virus, which can result in significant complications or death when not treated promptly.
Side effects of the antiviral drugs may include nausea, vomiting, diarrhea, loss of appetite, and muscle or joint soreness or pain. Rare serious problems may include abnormalities in kidney or liver function or suppression of bone marrow activity. Appropriate tests are used to monitor for serious adverse effects.
The best way to prevent viral encephalitis is to take precautions to avoid exposure to viruses that can cause the disease:
Protection against mosquitoes and ticks
Protection for young children
Tips for using mosquito repellent with children include the following:
Last Updated: 2011-05-05
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