Diagnosis

Your doctor will start with a thorough physical examination and medical history.

Your doctor might then recommend:

• Brain imaging. MRI or CT images can reveal any swelling of the brain or another condition that might be causing your symptoms, such as a tumor.
• Spinal tap (lumbar puncture). A needle inserted into your lower back removes a small amount of cerebrospinal fluid (CSF), the protective fluid that surrounds the brain and spinal column. Changes in this fluid can indicate infection and inflammation in the brain. Sometimes samples of CSF can be tested to identify the virus or other infectious agent.
• Other lab tests. Samples of blood, urine or excretions from the back of the throat can be tested for viruses or other infectious agents.
• Electroencephalogram (EEG). Electrodes affixed to your scalp record the brain's electrical activity. Certain abnormal patterns may indicate a diagnosis of encephalitis.
• Brain biopsy. Rarely, a small sample of brain tissue might be removed for testing. A brain biopsy is usually done only if symptoms are worsening and treatments are having no effect.