What is encephalitis?
Encephalitis is brain inflammation.
What causes encephalitis?
- Encephalitis is a rare condition that is most often caused by viruses (viral encephalitis).
- It can also be caused by noninfectious diseases, such as systemic lupus erythematosus and Behçet's disease (an autoimmune disorder).
- The leading cause of severe encephalitis is the herpes simplex virus.
- Other causes include enterovirus infections or mosquito-borne viruses.
- Eastern equine encephalitis (EEE),
- Western equine encephalitis (WEE),
- Venezuelan equine encephalitis (VEE),
- Japanese encephalitis, and
- Zika virus.
- The very young and the elderly are more likely to have more severe encephalitis.
Exposure to viruses can occur through breathing in respiratory droplets from infected people, certain insect bites, and direct skin contact.
What are the risk factors for encephalitis?
Patients with suppressed immune systems (due to medications or diseases) have an increased risk for encephalitis.
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Sensitivity to light is the inability to tolerate light, medically known as photophobia. In someone who is light sensitive, any type of light source (sunlight, fluorescent light, incandescent light) can cause discomfort. Photophobia typically causes a need to squint or close the eyes, and headache, nausea, or other symptoms may be associated with photophobia. Symptoms may be worse with bright light. People with light-colored eyes are more likely to have sensitivity to bright light than those with darker-pigmented eyes. Light sensitivity is caused by a number of conditions that affect the eye (such as iritis, uveitis, and keratitis), as well as conditions that affect the entire body.
Is encephalitis contagious?
Infectious forms of encephalitis are contagious. Viral and many bacterial forms of encephalitis are contagious. Several forms of bacterial encephalitis can be spread by respiratory and throat excretions. Encephalitis can also be caused by an infection in the body that spreads to the brain. Noninfectious encephalitis, such as from diseases systemic lupus erythematosus and Behçet's disease, are not contagious.
What are encephalitis symptoms and signs?
The signs and symptoms of encephalitis can range from very mild flu-like symptoms to potentially life-threatening events. Signs and symptoms of encephalitis include
- sudden fever,
- visual sensitivity to light,
- stiff neck and back,
- unsteady gait,
- loss of consciousness,
- poor responsiveness,
- muscle weakness,
- sudden severe dementia, and
- memory loss.
Anyone experiencing symptoms of encephalitis should see a doctor immediately.
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What specialties of doctors treat
People with encephalitis usually need treatment in the hospital. A family practice or general internal-medicine physician or an infectious-disease specialist will usually treat someone with encephalitis.
How do health care professionals diagnose encephalitis?
A health care professional diagnoses encephalitis after performing a thorough history and exam. The exam will incorporate special techniques to look for signs of inflammation of the membranes that surround the spinal cord and brain (meninges). The doctor will order specific tests to help determine the diagnosis.
Tests that evaluate individuals suspected of having encephalitis include cerebrospinal fluid analysis, brain scanning (such as CT scan or MRI scan), and an evaluation of the blood for infection and the presence of bacteria.
The most common method of obtaining a sample of cerebrospinal fluid (or CSF) for examination is a spinal tap. A spinal tap, or lumbar puncture (LP), involves the insertion of a needle into the fluid within the spinal canal. The needle goes between the spine's bony parts until it reaches the CSF. A medical professional then collects a small amount of fluid to send to the laboratory for exam. Evaluating the CSF is necessary for a definitive diagnosis of encephalitis and to decide on the best treatment options.
Abnormal spinal fluid results confirm the diagnosis and, in the event of an infection, by identifying the organism that caused the infection.
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What is the treatment of encephalitis?
People require urgent treatment with antibiotic and/or antiviral medications if a physician suspects that person has encephalitis. Patients may need to take sedatives for irritability or restlessness. Doctors may administer other medications to decrease the fever or treat headaches.
Is it possible to prevent encephalitis? Is there an encephalitis vaccine?
Basic steps to avoid spread of infections (hand washing, covering mouth when coughing, etc.) can help prevent encephalitis.
Some vaccinations for bacterial or viral diseases can help prevent encephalitis.
What is the prognosis (outlook), and what are the complications for patients
The prognosis for encephalitis varies. Some cases are benign and patients recover fully. Other cases are severe. The type of infection present and how quickly treatment starts determine the prognosis. The acute phase of encephalitis may last for one to two weeks, with gradual or sudden resolution of fever and neurological symptoms. Neurological symptoms may require many months before full recovery occurs. Some patients will not fully recover.
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Medically Reviewed on 8/29/2019
United States. Centers for Disease Control and Prevention. "2012 Recommended Immunizations for Children From 7 Through 18 Years Old." Jan. 10, 2017. <http://www.cdc.gov/vaccines/who/teens/downloads/parent-version-schedule-7-18yrs.pdf>.
United States. Centers for Disease Control and Prevention. "Vaccines & Immunizations." Apr. 23, 2018. <http://www.cdc.gov/vaccines/index.html>.
United States. National Institute of Neurological Disorders and Stroke, National Institutes of Health. "Meningitis and Encephalitis Fact Sheet." July 6, 2018. <https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Meningitis-and-Encephalitis-Fact-Sheet>.