How is encephalitis diagnosed?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Encephalitis may be diagnosed using a variety of methods. A spinal tap is a common procedure used to diagnose encephalitis. A needle is used to collect a small amount of cerebrospinal fluid (fluid that surrounds the brain and spine). The fluid is then tested for an elevation in the number of white blood cells or evidence of antibodies to the virus. Brain imaging is another method used to diagnose encephalitis. This method can detect swelling of the brain by using computerized tomography, or magnetic resonance imaging.

To diagnose encephalitis, doctors will do computed tomography (CT) and magnetic resonance imaging (MRI) scans to take pictures of the brain.

Next, doctors may do a lumbar puncture, taking some of the fluid that surrounds the spinal cord in the back. The spinal cord is connected to the brain, so testing the fluid from the spinal cord lets the doctors know if there’s a problem in the brain. The doctors numb the skin around the spine before inserting the needle. This means that the lumbar puncture doesn’t hurt too much.

Finally, doctors might also use an electroencephalogram (EEG) test. This is when the doctors put sensors on the head and check the electrical activity inside the brain. If there are seizures, it will alter the electrical pattern. This change will be detected and show up on the EEG printout.

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