Encephalitis is inflammation of the brain tissue. It is caused either by infection, which is usually viral, or by autoimmune conditions (conditions that cause the immune system to malfunction and attack healthy tissue).
Encephalitis is a complex condition that has a number of possible causes. It is often referred to as a ‘rare complication of common infections’.
The initial stage of encephalitis is usually serious and severe, and it is often followed by an injury to the brain (which can vary in degree and severity). Encephalitis usually begins with flu-like symptoms, such as:
- high temperature (fever) of 38ºC (100.4ºF) or above
- headache
- nausea and vomiting
- joint pain
More serious symptoms may then begin to develop, including:
- changes in mental state, such as confusion, drowsiness or disorientation
- seizures (fits)
- changes in personality and behaviour
See encephalitis - symptoms for more information.
Treatment
Encephalitis is usually regarded as a medical emergency, and it typically requires immediate admission to an intensive care unit.
Treatment options for encephalitis include:
- anti-viral medication
- steroid injections (the medical term for this is intravenous corticosteroids)
- immunosuppressants (medicines that stop the immune system from attacking healthy tissue)
For more information, see encephalitis – treatment.
Outlook
The inflammation that is associated with encephalitis can also result in an acquired brain injury, which can lead to long-term complications. These can include:
- memory loss
- epilepsy – a condition that causes repeated seizures
- personality and behavioural changes
- developmental difficulties
- problems with attention, concentration, planning and problem solving
- physical and motor difficulties
- fatigue (extreme tiredness)
For more information see encephalitis – complications.
How common is encephalitis?
In the UK, all types of encephalitis are relatively rare. The leading charity for people affected by encephalitis, the Encephalitis Society, estimates that there are 4,000 case of encephalitis in the UK each year.
People of all ages and both sexes can be affected by encephalitis, but the very young and the very old are most at risk because their immune system (the body’s natural defence against infection and illness) tends to be weaker.
Vaccinations
A number of vaccinations can help protect your child against encephalitis. The MMR vaccine is the best way to protect your child against it. Before the MMR vaccine was introduced, measles, mumps and rubella were leading causes of encephalitis in children.
See encephalitis - prevention and the Health A-Z topic about MMR for more information and advice.
