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Encephalitis

What is encephalitis?

Encephalitis is inflammation of the brain. This leads to changes in neurological function. It can result in various symptoms, including mental confusion and seizures.

What causes encephalitis?

Viruses are the leading cause of encephalitis. Vaccines for many viruses, such as measles, mumps, and chickenpox, have greatly lowered the rate of encephalitis from these diseases. But other viruses can also cause encephalitis. These include herpes simplex virus and rabies.

Encephalitis can also occur from:

  • An infection caused by things that carry a disease, such as ticks (Lyme disease), mosquitoes (West Nile virus), and cats (toxoplasmosis).

  • Bacteria.

  • Autoimmune conditions that can attack the brain. This is called autoimmune encephalitis. It can also occur when your body may be trying to fight cancer. Sometimes encephalitis can start before a person knows about the cancer.

What are the symptoms of encephalitis?

Encephalitis often follows a viral illness such as an upper respiratory infection. It may occur after a gastrointestinal illness that causes diarrhea, nausea, or vomiting. Symptoms may vary. The most common symptoms of encephalitis include:

  • Headache.

  • Mild flu-like symptoms (aches, fatigue, slight fever).

  • Sensitivity to light.

  • A stiff neck.

  • Sleepiness or lethargy.

  • Increased irritability.

  • Seizures.

  • Changes in alertness, confusion, or hallucinations.

  • Loss of energy.

  • Loss of appetite.

  • Unsteady gait.

  • Nausea and vomiting.

  • Personality changes.

In severe cases, symptoms may include:

  • Weakness or paralysis in the arms and legs.

  • Double vision.

  • Impaired speech or hearing.

  • Coma.

These symptoms may look like other health problems. Always see your health care provider for a diagnosis.

How is encephalitis diagnosed?

Your health care provider can diagnose encephalitis based on your symptoms, physical exam, and certain tests. During the exam, your provider will ask about your past health, including what vaccines you’ve had. They may also ask if you have:

  • Recently had a cold or other respiratory or gastrointestinal illness.

  • Recently had a tick bite or been around pets or other animals.

  • Traveled to other countries or certain parts of the country.

You may need these tests:

  • MRI. This procedure uses large magnets, radio waves, and a computer to make detailed images of organs and structures within the body.

  • CT scan. This imaging test uses X-rays and computer technology to make detailed images of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.

  • Blood tests. In this test, the blood is examined for signs of infection or an immune system disorder.

  • Urine and stool tests. In this test, the urine and stool samples are examined for infection.

  • Sputum culture. This test is done on the material (sputum) that is coughed up from the lungs and into the mouth. A sputum culture is often done to see if an infection is present.

  • Electroencephalogram (EEG). This test records the brain's continuous electrical activity using electrodes attached to the scalp.

  • Spinal tap (lumbar puncture). For this test, a special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can be measured. A small amount of cerebrospinal fluid (CSF) can be removed and sent for testing to see if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.

  • Brain biopsy. This procedure involves removing tissue or cells from the body to examine it under a microscope. In rare cases, a biopsy of affected brain tissue may be removed for diagnosis.

  • Intracranial pressure monitoring (ICP). This test measures the pressure inside the skull. If there is a severe brain injury, head surgery, brain infection, or other problems, the brain may swell. The ICP reads the pressure inside the skull. If the pressure goes up, it can be treated right away. While the ICP device is in place, you will be given medicine to stay comfortable. When the swelling has gone down and there is little chance of more swelling, the device will be removed.

How is encephalitis treated?

The key to treating encephalitis is early detection and quick treatment. A person with encephalitis needs to be watched closely in a hospital.

The goal of treatment is to reduce the swelling in the head and to prevent other related complications. Your health care provider may use medicines to control the infection, seizures, fever, or other conditions. If the problem is from an immune attack, treatment to suppress the immune system is used. If underlying cancer is the cause, the cancer will be treated as well.

What are possible complications of encephalitis?

Complications of encephalitis depend on the severity of inflammation and whether you have other organ problems. Mild cases often don't last long, and most people fully recover. In severe cases, a breathing machine may be needed to help you breathe easier. Severe cases can cause permanent impairment, including:

  • Fatigue.

  • Irritability.

  • Problems concentrating.

  • Seizures.

  • Hearing loss.

  • Memory loss.

  • Blindness.

  • Death.

What can I do to help prevent encephalitis?

These measures can help prevent encephalitis:

  • Keep your immunizations up-to-date. Vaccines are an important part of preventing encephalitis. Vaccines for viruses such as measles, mumps, rubella, and chickenpox have greatly lowered the rate of encephalitis from these diseases.

  • Use proper hygiene and hand-washing to help prevent the spread of infection.

  • Reduce your exposure to mosquitoes and ticks.

If you are exposed to someone with bacterial encephalitis, you may be offered a course of antibiotics to prevent you from getting the disease.

Living with encephalitis

As you get better, physical, occupational, or speech therapy may help you regain muscle strength and speech skills.

Loved ones can learn how to best care for you at home. You will need frequent checkups after being in the hospital.

When should I call my doctor?

Contact your health care provider if you have:

  • A headache.

  • A fever.

  • Neck stiffness.

  • Drowsiness.

Also call if you have signs of neurological involvement, such as:

  • Seizures.

  • Memory loss.

  • Visual problems.

  • Impaired hearing.

  • Behavioral changes.

Key points on encephalitis

  • Encephalitis is inflammation of the brain.

  • It is most commonly caused by a virus.

  • Headache, stiff neck, and sensitivity to light are common symptoms.

  • Encephalitis can be deadly, and prompt treatment is crucial for full recovery.

  • Most people recover fully, but long-term complications can occur in severe cases.

  • Preventing encephalitis includes staying up-to-date on vaccines, having good hygiene, and staying away from ticks and mosquitoes.

Next steps

Here are some tips to help you get the most from a visit to your health care provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also, write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also, know what the side effects are and when they should be reported.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Online Medical Reviewer: Esther Adler
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Shaziya Allarakha MD
Date Last Reviewed: 1/1/2025
© 2000-2025 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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