This paper was prepared by the Encephalitis Society with advice from Dr Nicholas Davies, Research Registrar Dept of Neuroimmunology, King's College London

Diagnosis

Investigations undertaken in hospital are likely to include a brain scan (CT or MRI) to show the extent of the inflammation; an EEG to determine unusual patterns of brain activity; and a lumbar puncture to try and discover any organism or evidence of inflammation present in the spinal fluid.

Diagnosis of encephalitis is made where there is evidence of inflammation.  The encephalitis we are concerned with is usually caused by a viral infection.  In more than half the cases of viral encephalitis the identity of the infecting viruses is not conclusively determined.

Treatment

Prompt treatment with Acyclovir is important.  Acyclovir is an anti-viral agent effective against herpes viruses.  Although not always identified, herpes simplex (the cold sore virus) is the commonest found cause of encephalitis in this country. There is no specific treatment, at present, for the majority of other virus 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 brain swelling.  Antibiotics may be given to treat secondary bacterial infections resulting from being seriously ill. 

Acute disseminated encephalomyelitis (ADEM) is treated with steroids.

Notification

Encephalitis is a statutory notifiable disease.  The doctor who makes the diagnosis is responsible for reporting the incident to the local Public Health department.

Brain Scans

During the acute phase of an encephalitic illness, a scan will be taken to assess the extent of the inflammation. After encephalitis the scans may show areas of damage to the brain that sometimes account for residual problems such as seizures. The most common type of scan is CT (computerised tomography). The patient lies on a mobile couch which slides their head into the scanner, which looks a bit like the drum of a washing machine. X-rays are taken of the brain at different angles and analysed by a computer, to produce a picture of “slices” of the brain.

A more sophisticated technique is MRI (magnetic resonance imaging). This provides a high-quality image of the brain - without using x-rays.  The drum-like scanner contains a powerful magnet which stimulates molecules of the brain to emit unique signals.  The signals are fed into a computer - which from their pattern creates a 3-D image of the area being scanned. The test is very noisy and for the best pictures patient has to remain very still.

Scans will show only gross structural damage. Sometimes encephalitis results in microscopic damage which is too small to be seen on today’s scans.

The Brain and Spine Foundation produces booklets explaining scans in more detail.  They can be ordered through their web site at http://www.brainandspine.org.uk

Lumbar Puncture

A hollow needle is inserted between two of the lumbar vertebrae into the space surrounding the end of the spinal cord.  A specimen of cerebrospinal fluid (CSF), the fluid which supports and nourishes the brain, is taken to investigate  the presence of bacteria, virus or inflammation.

EEG

Electroencephalogram – a test to record the electrical activities of the brain.

Last modified – 25/11/05