Diagnosis

Your health care provider will start with a thorough physical examination and medical history.

Your provider 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, known as a 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 point to infection and inflammation in the brain. Sometimes samples of CSF can be tested to identify the cause. This may include testing for infection or presence of antibodies associated with autoimmune encephalitis.
  • 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.
  • Body imaging. Sometimes, autoimmune encephalitis may be triggered by an abnormal immune response to a tumor, benign or cancerous, in your body. Your health care provider may order imaging studies, such as ultrasound, MRI, CT or CT-PET scans. These scans may look at your chest, abdomen or pelvis to check for these tumors. If a mass is found, a small piece of it may be removed to study it in a lab. This is known as a biopsy.
  • 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.

Treatment

Treatment for mild encephalitis usually consists of:

  • Bed rest.
  • Plenty of fluids.
  • Anti-inflammatory medicines — such as acetaminophen (Tylenol, others), ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve) — to relieve headaches and fevers.

Antiviral medicines

Encephalitis caused by certain viruses usually requires antiviral treatment.

Antiviral medicines commonly used to treat encephalitis include:

  • Acyclovir (Zovirax).
  • Ganciclovir (Zirgan).
  • Foscarnet (Foscavir).

Some viruses, such as insect-borne viruses, don't respond to these treatments. But because the specific virus may not be identified immediately or at all, health care providers often recommend immediate treatment with acyclovir. Acyclovir can be effective against HSV, which can result in significant complications when not treated promptly.

Antiviral medicines are generally well tolerated. Rarely, side effects can include kidney damage.

Autoimmune encephalitis

If the tests show an autoimmune cause of encephalitis, then medicines that target your immune system, known as immunomodulatory medicines, or other treatments may be started. These may include:

  • Intravenous or oral corticosteroids.
  • Intravenous immunoglobulin.
  • Plasma exchange.

Some people with autoimmune encephalitis need long-term treatment with immunosuppressive medicines. These may include azathioprine (Imuran, Azasan), mycophenolate mofetil (CellCept), rituximab (Rituxan) or tocilizumab (Actemra).

Autoimmune encephalitis caused by tumors may require treatment of those tumors. This may include surgery, radiation, chemotherapy or a combination of treatments.

Supportive care

People who are hospitalized with severe encephalitis might need:

  • Breathing assistance, as well as careful monitoring of breathing and heart function.
  • Intravenous fluids to ensure proper hydration and levels of essential minerals.
  • Anti-inflammatory medicines, such as corticosteroids, to reduce swelling and pressure within the skull.
  • Anticonvulsant medicines, such as phenytoin (Dilantin), to stop or prevent seizures.

Follow-up therapy

If you experience complications of encephalitis, you might need additional therapy, such as:

  • Brain rehabilitation to improve cognition and memory.
  • Physical therapy to improve strength, flexibility, balance, motor coordination and mobility.
  • Occupational therapy to develop everyday skills and to use adaptive products that help with everyday activities.
  • Speech therapy to relearn muscle control and coordination to produce speech.
  • Psychotherapy to learn coping strategies and new behavioral skills to improve mood disorders or address personality changes.

Preparing for your appointment

Serious illness associated with encephalitis is usually severe and relatively sudden, so seek emergency care. The emergency care team will likely include specialists in infectious diseases, the brain and nervous system (neurologist).

Questions from your doctor

You may need to answer these questions, or answer them on behalf of your child or another person with severe illness:

  • When did the symptoms begin?
  • Have you recently started taking any new medicines? If so, what is the medicine?
  • Have you been bitten by a mosquito or tick during the past few weeks?
  • Have you traveled recently? Where?
  • Have you recently had a cold, flu or other illness?
  • Are you up to date on your immunizations? When was your last one?
  • Have you had any exposure to wild animals or known toxins recently?
  • Have you had unprotected sex with a new or long-term sexual partner?
  • Do you have a condition or take any medicines that result in a weakened immune system?
  • Do you have an autoimmune condition or do autoimmune conditions run in the family?
By Mayo Clinic Staff