Encephalitis - Diagnosis

The first step in diagnosis may be a medical history. A doctor will try to determine if the patient has had recent contact with a virus that can cause encephalitis. The diagnosis can be confirmed with a variety of tests. These include:

• Blood tests. Blood tests may detect antibodies against viruses. Antibodies are chemicals produced by the body's immune system. They are manufactured when a foreign agent, such as a virus, enters the body.
• Lumbar puncture (spinal tap). In a lumbar puncture, a long, thin needle is inserted into the spinal column. A small amount of cerebrospinal (pronounced suh-REE-bro-spyn-al) fluid (CSF) is removed. The fluid can be tested to see if viruses or bacteria are present.
• Electroencephalogram (pronounced ih-LEK-tro-en-SEF-ah-lo-gram; also called an EEG). An EEG is a test in which electrical currents in the brain are measured. The test can show whether there has been damage to the brain.
• Imaging scans. The brain can be studied by a number of imaging techniques, such as X rays and magnetic resonance imaging (MRI). These techniques often reveal abnormal structures in the brain.
• Biopsy. In a biopsy, a needle is used to remove a small portion of brain tissue. The brain tissue can then be studied under a microscope. The presence of viruses or other foreign agents may be detected.