Encephalitis is inflammation (swelling) of the brain. It happens when an infection or another condition affecting the brain switches on the immune system, and the inflammation can cause a wide range of symptoms. At its worst it can lead to brain damage, stroke or death.
Two main kinds
Infectious encephalitis
Viruses are the most common cause of encephalitis:
| Group | Examples |
|---|---|
| Herpes viruses | herpes simplex (HSV); Epstein-Barr virus, which causes infectious mononucleosis; varicella-zoster virus, which causes chickenpox |
| Tick-borne | tick-borne encephalitis (TBE) virus, Powassan virus |
| Mosquito-borne | eastern equine encephalitis virus, West Nile virus, La Crosse virus |
| Enteroviruses | a common group that mostly causes mild illness or respiratory infections, usually in summer and fall |
Bacteria, fungi and parasites can also cause it, but rarely.
Autoimmune encephalitis
Here the immune system attacks healthy brain cells by mistake. It can be set off by certain cancers, benign tumors or infections — and sometimes no cause is found.
Who is more at risk
Anyone can get encephalitis, but the risk is higher for:
- people with a weakened immune system — from HIV, for example, or from medicines such as those taken after an organ transplant, some chemotherapy, and specialized treatments for some autoimmune diseases;
- young children and older adults;
- people living where ticks and mosquitoes carry viruses that cause it.
Symptoms
They vary a great deal with severity. Many people have none. Others have mild, flu-like symptoms — fever, tiredness, headache, body aches.
| More serious encephalitis can cause | In infants, watch for |
|---|---|
| severe headache | fever |
| stiff neck | lethargy (weakness or drowsiness) |
| vomiting | poor feeding |
| seizures | vomiting |
| changes in behavior | body stiffness |
| drowsiness | unusual irritability or crying |
| muscle weakness | a full or bulging fontanel — the soft spot on top of the head |
| partial paralysis of the arms and legs | |
| coma |
Encephalitis can be dangerous in babies. If you or your child has symptoms, get medical care right away.
Diagnosis
A health care provider will examine you and ask about your symptoms and medical history, and may also:
- do a neurologic exam;
- order brain imaging — a CT scan or MRI;
- order an EEG (electroencephalography), which uses small electric sensors to measure brain activity;
- test your blood and cerebrospinal fluid (CSF).
Treatment
Most people need hospital care. Depending on the cause, treatment may include antiviral medicines, antibiotics, corticosteroids and other drugs. Some kinds of encephalitis have no specific medicine, but rest, nutrition and fluids help the body fight the infection and ease symptoms. Once the illness is under control, some people need physical, speech or occupational therapy.
Prevention
For encephalitis caused by infection:
- Wash your hands often with soap and water.
- Don't share food, drinks, utensils or glasses.
- Get vaccinated against viruses that can cause encephalitis.
- Avoid mosquito and tick bites:
- use an insect repellent with DEET or another EPA-registered repellent, following its instructions;
- wear clothes that cover your arms, legs and feet;
- treat clothes and gear with products containing 0.5% permethrin before going into grassy or wooded areas.
Sources
Based on "Encephalitis," MedlinePlus, National Library of Medicine, with content from the NIH's National Institute of Neurological Disorders and Stroke; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from medlineplus.gov
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