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 point to infection and inflammation in the brain. Sometimes samples of CSF can be tested to identify the cause. This may include a virus, other cause of infection or autoimmune disorder.
  • 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.

Treatment

Treatment for mild encephalitis usually consists of:

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

Antiviral drugs

Encephalitis caused by certain viruses usually requires antiviral treatment.

Antiviral medications commonly used to treat encephalitis include:

  • Acyclovir (Zovirax)
  • Ganciclovir (Valcyte, Zirgan, others)
  • 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, doctors often recommend immediate treatment with acyclovir. Acyclovir can be effective against HSV, which can result in significant complications when not treated promptly.

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

Autoimmune encephalitis

If the tests show an autoimmune cause of encephalitis, then immunosuppressant drugs such as steroids may be started.

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 drugs, such as corticosteroids, to reduce swelling and pressure within the skull
  • Anticonvulsant medications, 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:

  • 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

Clinical trials

Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this condition.

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 medications? If so, what is the medication?
  • 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 medications that result in a weakened immune system?
  • Do you have an autoimmune condition or do autoimmune conditions run in the family?

Encephalitis care at Mayo Clinic

May 26, 2022
  1. Bennett JE, et al. Encephalitis. In: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Saunders Elsevier; 2020. http://www.clinicalkey.com. Accessed April 5, 2022.
  2. Krogstad P, et al. Acute viral encephalitis in children: Clinical manifestations and diagnosis. https://www.uptodate.com/contents/search. Accessed April 5, 2022.
  3. Ferri FF. Encephalitis, acute viral. In: Ferri's Clinical Advisor 2022. Elsevier; 2022. http://www.clinicalkey.com. Accessed April 5, 2022.
  4. AskMayoExpert. Viral encephalitis. Mayo Clinic; 2022.
  5. Gluckman SJ. Viral encephalitis in adults. https://www.uptodate.com/contents/search. Accessed April 5, 2022.
  6. Meningitis and encephalitis fact sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Meningitis-and-Encephalitis-Fact-Sheet. Accessed April 5, 2022.
  7. Bradshaw MG, et al. Emergency evaluation and management of encephalitis and myelitis in adults. Seminars in Neurology. 2019; doi:10.1055/s-0038-1676845.
  8. Patel H, et al. Long-term sequelae of West Nile virus-related illness: A systematic review. The Lancet Infections Diseases. 2015;15:951.
  9. Krogstad P, et al. Acute viral encephalitis in children: Treatment and prevention. https://www.uptodate.com/contents/search. Accessed April 5, 2022.
  10. Daroff RB, et al. Viral encephalitis and meningitis. In: Bradley's Neurology in Clinical Practice. 8th ed. Saunders Elsevier; 2022. https://www.clinicalkey.com. Accessed April 5, 2022.
  11. Zachary KC. Acyclovir: An overview. https://www.uptodate.com/contents/search. Accessed April 5, 2022.
  12. Breisch N. Prevention of arthropod and insect bites: Repellents and other measures. https://www.uptodate.com/contents/search. Accessed April 5, 2022.
  13. West Nile virus prevention. Centers for Disease Control and Prevention. http://www.cdc.gov/westnile/faq/repellent.html. Accessed April 5, 2022.
  14. Dubey D, et al. Autoimmune encephalitis epidemiology and a comparison to infectious encephalitis. Annals of Neurology. 2018; doi:10.1002/ana.25131.
  15. Thomas AR. Allscripts EPSi. Mayo Clinic. Jan. 28, 2022.
  16. Krogstad P, et al. Acute viral encephalitis in children: Treatment and prevention. https://www.uptodate.com/contents/search. Accessed April 13, 2022.
  17. Singh TD, et al. Predictors of outcome in HSV encephalitis. Journal of Neurology. 2016;263:277.
  18. Wormser GP, et al. Update and commentary on four emerging tick-borne infections. Infectious Disease Clinics of North America. 2015;29:371.
  19. Howe CL, et al. Neuroprotection mediated by inhibition of calpain during acute viral encephalitis. Scientific Reports. 2016;6:28699.
  20. Graff-Radford J (expert opinion). Mayo Clinic. April 14, 2022.

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