Questions and Answers
Here are some frequently asked questions and their answers
What exactly is encephalitis?
Encephalitis is inflammation of the brain.
Encephalitis is different from meningitis. Meningitis means inflammation of the
protective layers that cover the brain. Sometimes people have both meningitis and
encephalitis and this is called meningoencephalitis.
How is the inflammation caused?
The inflammation is caused either by an infection invading the brain (infectious);
or through the immune system attacking the brain in error (post-infectious / autoimmune
encephalitis).
Who can get encephalitis ?
Anyone, at any age. Statistics from the USA provide an indication of the prevalence
of encephalitis. Beghi et al (1984) reported the annual incidence as 7.4 people
per 100 000 and, more recently, Khetsuriani et al (2002) reported 7.3 hospitalizations
per 100 000 population. There are no statistics for the UK. However, based on the
US statistics, it can be estimated that about 4000 people are newly affected each
year (Easton et al, 2006).
What causes infectious encephalitis?
Viruses are the commonest cause of infectious encephalitis. Many viruses cause minor
infections elsewhere in the body, such as tummy upsets, skin rashes and cold sores.
Only very rarely do the same infections affect the brain, therefore encephalitis
is often described as a rare complication of common infections. The introduction
of vaccination for measles, mumps and rubella has greatly lowered the rate of encephalitis
from these diseases. Within the British Isles, Herpes Simplex Virus (HSV or the
cold sore virus) is the virus most frequently identified. Worldwide other viruses
are found, many of which can be transmitted by mosquito or tick bites.
More rarely bacteria, fungus and parasites can also cause encephalitis.
What causes Post-infectious Encephalitis / Autoimmune Encephalitis
Although viruses infecting the brain are a major cause of encephalitis, the body's
reaction to infection can lead to encephalitis. This occurs when the immune system
tries to fight off the infection, and by mistake attacks the brain at the same time.
This condition is called Post-infectious Encephalitis.
It has recently been recognised that there are other forms of encephalitis that
result from attack of the brain by the body’s immune system. Some of these
types of autoimmune encephalitis are identified by finding a specific antibody in
the blood. The trigger in these cases is not known.
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 an inflammatory process
of the brain in association with clinical evidence of neurologic dysfunction.
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 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 1 (the cold
sore virus) is the most commonly identified 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 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.
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Last modified: July 2009