Encephalitis

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Encephalitis

Topic Overview

What is encephalitis?

Encephalitis is inflammation of the brain. Inflammation changes the normal blood flow in the brain. This can cause symptoms such as confusion, a fever, a bad headache, and a stiff neck. Sometimes it leads to symptoms like seizures and personality changes.

Encephalitis is rare, but it can be deadly. If you think you have symptoms of encephalitis, see a doctor right away.

Most people recover if they are treated promptly. But the illness can sometimes cause long-term problems, such as trouble with speech or memory.

What causes encephalitis?

Infection with a virus is the main cause of encephalitis. The herpes simplex virus is a common cause in Canada and the United States. This is the same virus that causes cold sores and genital herpes. The viruses that cause mumps, measles, chickenpox, mono (Epstein-Barr virus), influenza, and German measles (rubella) also can cause encephalitis. But these viruses only rarely infect the brain and cause encephalitis.

Another group of viruses, called arboviruses, can spread encephalitis through bites from mosquitoes and ticks. West Nile virus is one of these viruses. But most people who are bitten by infected mosquitoes or ticks do not get any symptoms. And only a very small number of people who have symptoms get encephalitis.

Infection with the rabies virus is a form of encephalitis, but this is very rare.

What are the symptoms?

Symptoms of encephalitis can be mild or very serious. Symptoms can include:

  • Confusion.
  • A fever.
  • A headache (which can be very painful).
  • A stiff neck and back.
  • Light hurting your eyes.
  • Nausea and vomiting.
  • Lack of energy.
  • Drowsiness.

More serious symptoms include:

  • Seizures.
  • Tremors.
  • Personality changes.
  • Memory loss.
  • Hallucinations (seeing or hearing things that aren't there).

Call your doctor right away if you or your child has any of these symptoms.

Early on, symptoms of encephalitis may be like those of meningitis. This is a serious viral or bacterial illness that causes swelling of the tissues around the brain and spinal cord.

In general, symptoms that come on suddenly and are very bad from the start point to a type of encephalitis that can be deadly.

How is encephalitis diagnosed?

Doctors usually diagnose encephalitis by testing the fluid in the spine for increases in white blood cells and protein.

An MRI or CT scan, which takes pictures of the inside of your body, may show bleeding, swelling, or other changes in the brain.

Another test, called an EEG, can measure the electrical signals in the brain. It may show a change related to the illness.

A sample of spinal fluid is taken during a lumbar puncture (also known as a spinal tap). In this test, the doctor puts a needle in your lower back between the bones of the spine.

You also may have blood tests to find out what type of virus is causing encephalitis. In some cases, a sample of brain tissue (biopsy) might be tested to look for infection.

How is it treated?

If you have encephalitis, you will need to be treated in a hospital. Your treatment will depend on your symptoms and the cause of your illness. Because herpes simplex virus is the most common cause of encephalitis, you will probably be treated right away with a medicine called acyclovir. This medicine can stop viruses. But it works best if you get it right away.

There is no antiviral medicine to treat encephalitis caused by viruses spread by mosquitoes or ticks. Instead, you would get care to ease your symptoms and allow your body to heal on its own. This is called supportive care. You may take medicines to reduce pain and fever or to stop seizures. In some cases, you may need a machine called a ventilator to help you breathe.

The doctor may think your symptoms are caused by bacteria, rather than by a virus. If so, he or she may prescribe antibiotics right away.

Can encephalitis be prevented?

Your chance of getting encephalitis is low. But you can reduce your chance of getting it even more.

  • Make sure that you and your children get shots (vaccines) against measles, mumps, rubella, chickenpox, and the flu.
  • Avoid areas where there has been an outbreak of viral encephalitis. If you can't avoid these areas, prevent mosquito bites:
    • Stay indoors at dawn, at dusk, and in the early evening, when mosquitoes are most active.
    • Wear long-sleeved shirts and long pants whenever you are outdoors and are likely to be where mosquitoes are.
    • Avoid wearing floral fragrances from perfumes, soaps, hair care products, and lotions. These may attract mosquitoes.
    • Spray clothing with an insect repellent containing DEET (N,N-diethyl-meta-toluamide), because mosquitoes may bite through thin clothing. DEET can damage plastic items, such as watch crystals or eyeglass frames, and some synthetic fabrics.
    • Use insect repellent with DEET (N,N diethylmetatoluamide). The repellent is available in strengths up to 30%. In young children, use a preparation containing less than 10% strength, because DEET can be toxic if too much of the chemical is absorbed through the skin. Do not use DEET on children younger than 6 months. To learn how to safely use insect repellents, visit Health Canada's Pest Management Regulatory Agency Web site at www.pmra-arla.gc.ca/english/consum/insectrepellents-e.html.2
    • Avoid applying repellent to the hands of children. Repellents may irritate the eyes and mouth.
    • Whenever you use an insecticide or insect repellent, be sure to read and follow the directions for use.
    • Do not keep open containers of water near your house. Standing water is a breeding place for mosquitoes.

Frequently Asked Questions

Learning about encephalitis:

Being diagnosed:

Getting treatment:

Ongoing concerns:

Symptoms

Be sure to seek immediate medical attention if you suspect that you have encephalitis. The key symptoms are fever, severe headache, and confusion.

Other symptoms that may occur include:

  • Abnormal sensitivity to light (photosensitivity).
  • Nausea and vomiting.
  • Stiff neck and back.
  • Lack of energy, sluggishness (lethargy).
  • Drowsiness.

More serious symptoms can also develop, including:

  • Seizures or tremors.
  • Personality changes.
  • Memory loss.
  • Trouble learning and understanding.
  • Restlessness.
  • Confused speech.
  • Hallucinations, which is seeing or hearing things that aren't there.
  • Delirium, which is a sudden change in your mental status, leading to confusion and unusual behaviour.

The most severe form of encephalitis can lead to coma and even death, especially if left untreated. In general, symptoms that develop suddenly and are severe from the start are more likely to progress to a life-threatening case of encephalitis.

Although complications such as speech or memory problems can occur, most people fully recover from encephalitis when they are treated promptly. But your chances for a full recovery decrease if you have severe symptoms, such as seizures or coma, or if you delay treatment.

The early stage of encephalitis may cause symptoms similar to meningitis, a serious viral or bacterial illness that causes inflammation of the tissues that surround the brain and spinal cord.

Examinations and Tests

Your doctor will ask questions about your past health and your symptoms. It is important to tell your doctor if you have taken any recent trips or have been sick lately. Your doctor may also ask about your sexual history to see if it's possible that you have had herpes simplex virus.

If your doctor thinks that you may have encephalitis, lab tests usually will be done to confirm the diagnosis.

A brain biopsy sometimes may be used to find the cause of encephalitis, but it is rarely done.

Treatment Overview

You may be treated for encephalitis in a hospital's intensive care unit. During your stay, your vital signs (blood pressure, heart rate, breathing, and level of body fluids) will be closely monitored. Treatment will depend on your symptoms and the particular cause of encephalitis, if the cause can be determined.

Because many cases of encephalitis are caused by the herpes simplex virus or the chickenpox (varicella-zoster) virus, doctors treat people with the antiviral medicine acyclovir, which is given in a vein (intravenous, or IV). It is important to start acyclovir treatment as soon as encephalitis is suspected, even if the exact cause of the illness is not known. This is because early treatment makes it more likely that you will get better.1

Call your doctor immediately if you think you have symptoms of encephalitis, such as a sudden and severe headache, fever, and confusion, especially if you also have a stiff neck, nausea, vomiting, and drowsiness. Treatment works best when given early in the illness.

Encephalitis caused by arboviruses, which are carried by mosquitoes and ticks, will not respond to acyclovir or other medicines. Instead of trying to kill the virus, doctors treat the symptoms so that you are comfortable and the body can heal itself.

  • High fever may be reduced with acetaminophen or non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, ASA, or naproxen. But a mild fever may actually promote healing and is usually not treated. ASA should not be given to anyone younger than 20 because of the risk of Reye syndrome.
  • Seizures may be controlled with anticonvulsant medicines such as phenytoin (Dilantin) or phenobarbital.
  • A machine to help you breathe (ventilator) and other supportive measures may be needed if you go into a coma.

If you have signs of encephalitis caused by bacteria, your doctor will prescribe antibiotics. This type of encephalitis is more common during tick season.

Home Treatment

Because encephalitis can be a life-threatening condition, it is not appropriate to treat it at home. Symptoms such as high fever, severe headache, and confusion along with nausea and vomiting and possibly a stiff neck and back may be caused by encephalitis. If you think you or someone you know may have encephalitis, seek immediate medical attention.

After you have been released from the hospital or are under the care of your doctor, it may take several weeks or months to fully recover from your symptoms. You can do things at home to help yourself feel better.

  • Get good nutrition and plenty of rest to help your body heal.
  • Follow your doctor's instructions on drinking fluids. Sometimes, too much fluid can cause more swelling in the brain and make symptoms of encephalitis worse.
  • Take non-prescription pain relievers, such as acetaminophen or non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen, ibuprofen, or ASA, for headaches unless your doctor has prescribed another pain reliever. Do not give ASA to anyone younger than 20 because of the risk of Reye syndrome.
  • Keep the lights low if you are sensitive to light.
  • Try to be patient while you are recovering—it may take several weeks or months to fully recover from all of your symptoms. Most people with encephalitis make a full recovery.

If you have muscle weakness or problems with coordination as a result of encephalitis, your doctor may prescribe physiotherapy and range-of-motion exercises. Likewise, if you have continued problems with speech or memory loss, your doctor may order speech and occupational therapies.

It is, of course, best if you can prevent encephalitis from ever occurring. You can decrease your risk of getting encephalitis by taking the following steps:

  • Make sure you are vaccinated against measles, mumps, rubella, chickenpox, and influenza. Encephalitis is a rare complication of these diseases.
  • Avoid areas where there has been an outbreak of viral encephalitis. If you cannot avoid these areas, prevent mosquito bites:
    • Stay indoors at dawn, at dusk, and in the early evening, when mosquitoes are most active.
    • Wear long-sleeved shirts and long pants whenever you are outdoors and are likely to be where mosquitoes are.
    • Avoid wearing floral fragrances from perfumes, soaps, hair care products, and lotions. These may attract mosquitoes.
    • Spray clothing with an insect repellent containing DEET (N,N-diethyl-meta-toluamide), because mosquitoes may bite through thin clothing. DEET can damage plastic items, such as watch crystals or eyeglass frames, and some synthetic fabrics.
    • Use insect repellent with DEET (N,N diethylmetatoluamide). The repellent is available in strengths up to 30%. In young children, use a preparation containing less than 10% strength, because DEET can be toxic if too much of the chemical is absorbed through the skin. Do not use DEET on children younger than 6 months. To learn how to safely use insect repellents, visit Health Canada's Pest Management Regulatory Agency at www.pmra-arla.gc.ca/english/consum/insectrepellents-e.html.2
    • Avoid applying repellent to the hands of children. Repellents may irritate the eyes and mouth.
    • Whenever you use an insecticide or insect repellent, be sure to read and follow the directions for use.
    • Do not keep open containers of water near your house. Standing water is a breeding place for mosquitoes.

Vaccines are available for certain types of mosquito- and tick-borne encephalitis that occur in the Far East and in central and eastern Europe. For example, there is a vaccine available for Japanese encephalitis. If you are planning an extended visit to one of these areas, especially if you will be spending time in rural areas, you may want to be vaccinated against the type of encephalitis that is widespread in that area.

No human vaccine is available yet for any of the types of mosquito-borne encephalitis that occur in the United States.

Other Places To Get Help

Online Resource

West Nile Virus information (Canada)
Public Health Agency of Canada
Web Address: www.phac-aspc.gc.ca/wn-no/index-eng.php
 

The Public Health Agency of Canada's West Nile virus information Web site provides an overview of the virus, its effects, and how it is spread; information on how you can protect yourself and your family from infection; and the latest statistics and maps of reported West Nile virus cases in Canada.


Organization

U.S. Centers for Disease Control and Prevention: National Center for Division of Vector Borne Diseases (DVBID)
3150 Rampart Road
Fort Collins, CO  80521
Phone: 1-800-CDC-INFO (1-800-232-4636)
Fax: (770) 488-4760
TDD: 1-888-232-6348
Email: cdcinfo@cdc.gov
Web Address: www.cdc.gov/ncidod/dvbid/index.htm
 

The Division of Vector-Borne Infectious Diseases is a national and international reference center for vector-borne viral and bacterial diseases. The mission of the division is to develop and maintain effective surveillance for vector-borne infectious diseases; conduct field and laboratory research and epidemic aid investigations; develop improved methods and strategies for disease diagnosis, surveillance, prevention, and control; and provide information and technical expertise.


References

Citations

  1. Roos KL, Tyler KL (2008). Meningitis, encephalitis, brain abscess, and empyema. In AS Fauci et al., eds, Harrison's Principles of Internal Medicine, 17th ed., vol. 2, pp. 2621–2641. New York: McGraw-Hill.
  2. Pest Management Regulatory Agency (2009).Pesticides and Pest Management. Available online: http://www.hc-sc.gc.ca/cps-spc/pest/index-eng.php.

Other Works Consulted

  • Drugs for non-HIV viral infections (2007). Treatment Guidelines From the Medical Letter, 5(59): 59–70.
  • Gilden DH (2008). Acute viral central nervous system diseases. In DC Dale, DD Federman, eds., ACP Medicine, section 11, chap. 16. Hamilton, ON: BC Decker.

Credits

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last Revised September 7, 2010

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.