What is encephalitis?

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

What causes encephalitis?

The cause of encephalitis depends on the season, the part of the country, and the type of exposure. 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 a disease-carrying agent, such as ticks (Lyme disease), mosquitoes (West Nile virus), and cats (toxoplasmosis)

  • Bacteria

  • Autoimmune diseases that attack the brain. Certain immune system diseases can cause encephalitis when your body may be trying to fight cancer. Sometimes the 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. Or it may occur after a gastrointestinal illness that causes diarrhea, nausea, or vomiting. Symptoms depend on which part of the brain is being attacked. These are the most common symptoms of encephalitis:

  • Headache

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

  • Sensitivity to light

  • Neck stiffness

  • 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 partial paralysis in the arms and legs

  • Double vision

  • Impairment of speech or hearing

  • Coma

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

How is encephalitis diagnosed?

Your healthcare provider can diagnose encephalitis based on your symptoms and certain tests. During the exam, your healthcare provider will ask about your medical history, 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 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 exam 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. Since the brain is covered by the skull, there is only a small amount of room for it to swell. This means that, as the brain swells, the pressure inside the skull goes up. If the pressure gets significantly higher than normal, it can cause damage to the brain. Intracranial pressure is measured by placing a small, hollow tube (catheter) into the fluid-filled space in the brain (ventricle). Other times, a small, hollow device (bolt) is placed through the skull into the space just between the skull and the brain. Both devices are inserted in the intensive care unit (ICU) or in the operating room. The ICP device is then attached to a monitor that gives a constant reading of 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 healthcare 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 are often short and result in a full recovery. 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 viruses and encephalitis.

  • 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 be educated on how to best care for you at home. You will need frequent checkups after being in the hospital.

When should I call my healthcare provider?

Call your healthcare provider if there are signs of another infection including:

  • Headache

  • 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.

  • Encephalitis 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 severe cases can lead to long-term complications.

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

Next steps

Tips to help you get the most from a visit to your healthcare 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.

  • 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: Joseph Campellone MD
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Date Last Reviewed: 3/1/2022
© 2000-2024 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.