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Exams and Tests

Geographic location and seasonal occurrence can help identify the specific cause of encephalitis. Depending on your unique situation, the doctor may perform 1 or more of the following tests:

• A picture of the brain such as a CT scan or magnetic resonance imagining (MRI) is often done. MRI is the procedure of choice if herpes encephalitis is suspected.

• A DNA study called polymerase chain reaction (PCR) has greatly improved the diagnosis of herpes encephalitis.

• A reading of the electrical activity of the brain with an EEG can detect irregularities. Herpes encephalitis produces a characteristic EEG pattern.

• A lumbar puncture, also known as a spinal tap, may be necessary to isolate the virus. During this procedure, the doctor applies local numbing medication and then inserts a needle into your lower back to collect fluid from the space around the spinal column for analysis.

• The virus may also be isolated from tissue or blood.

• Brain biopsy is an option although it is rarely done and usually only if the other tests do not give an answer.