Some commonly asked questions and their answers

What exactly is encephalitis?

Encephalitis means, simply, inflammation of the brain and is usually  a very rare consequence of a viral infection. Encephalitis is different from meningitis which is an inflammation of the layers which cover the brain (the meninges) although this also may be the result of a bacterial or viral infection.

How many types of encephalitis are there?

Essentially there are 2 types:  

• Acute Viral Encephalitis  - in which the virus attacks the brain directly.
• Post Infectious Encephalitis (also called Acute Disseminated Encephalomyelitis or ADEM ) – in which an infection outside the brain triggers the body's immune system to  attack the brain.

Who can get encephalitis?

Anyone, at any age.  The estimated annual incidence in the UK and Republic of Ireland is 4 per 100,000 (2,500 people per year).

What causes encephalitis?

The viruses responsible are often common viruses.  They include measles, chicken pox, influenza, enteroviruses (tummy bugs) and herpes simplex I (the cold sore virus).  In most cases the virus involved is not identified. 

What are the main symptoms?

Encephalitis  often begins with a “flu-like” illness or with headache.  Symptoms indicating that this is a more serious illness follow later and typically include “alteration in level of consciousness”.  These might include confusion, drowsiness, seizures (fits) and coma.  Other symptoms can include aversion to bright lights, inability to speak or control movement, sensory changes, neck stiffness, uncharacteristic behaviour, as well as other symptoms depending on the area of the brain under attack.

How is encephalitis diagnosed?

Diagnosis of encephalitis is made where there is evidence of inflammation.  The range of possible symptoms and their rate of development vary widely, and are not just found in encephalitis, so making the diagnosis can be difficult. 

What tests are undertaken?

• Lumbar puncture - to exclude bacterial meningitis and test for the herpes simplex virus. 
• Brain scans (CT or MRI) - to exclude brain tumours, aneurysms and strokes and show the extent of any inflammation.  
• Blood tests - to exclude metabolic encephalopathies.
• It is not unusual for the results of tests to be “normal” , it is important to initially exclude some more common and treatable diseases. 

How is encephalitis treated?

Prompt treatment with Acyclovir is important.  Acyclovir is an anti-viral agent effective against herpes viruses.  Although not always identified, herpes simplex I (the cold sore virus) is the commonest known cause of encephalitis in this country. There is no specific treatment, at present, for any other viruses infecting the brain.  Other treatments may include anti-convulsants to control seizures and sedatives to reduce agitation.  Intensive care with ventilation may also be necessary in severe cases to reduce swelling of the brain.  Antibiotics may be given as a precaution to prevent bacterial infections. 

Do people get better?

Nerve cells may be damaged or destroyed by the viral infection, the immune reaction and by pressure resulting from the inflammation.  This damage is termed “acquired brain injury (ABI).  Some loss of brain function is therefore a probable outcome of encephalitis.  In some cases, however, this loss occurs on a relatively small scale resulting in very minor impairment, such as some loss in speed of thinking.  In other cases damage can be extensive leading to significant impairments.

Recovery is a long and slow process.  An initial period of convalescence with plenty of rest is recommended.  This should be followed by a programme of graded activity and rest over 3 – 6 months giving the brain the opportunity to restore function.  In more severe cases a period in a brain injury rehabilitation unit may be necessary.

What are the after effects?

There will be a wide variation in exactly in how encephalitis affects the person in the long term.  Tiredness, recurring headaches, difficulties with memory, concentration and balance are often reported as are temper tantrums, mood swings, aggression and clumsiness.  Epilepsy, as well as being a feature of the acute illness, may develop weeks or months after the illness has subsided.  Physical problems may include weakness down one side of the body, loss of sensations and of control of bodily functions and movement.  Speech and language problems are also common features.  Speed of thought and reaction may be reduced.

Bereavement

Compared to other infectious diseases, encephalitis has a high mortality rate.  The illness can be very quickly fatal causing extreme trauma for all the family.  It is difficult to understand why a virus infection in the modern world can have such devastating consequences. 

MAY 2004

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Last modified: 07/11/06