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

Definition

A non-degenerative injury to the brain occurring since birth.  It can be caused by an external physical force or by metabolic.  This definition described by the 1996 Standards Manual and Interpretative Guidelines for Medical Rehabilitation, The Rehabilitation Accreditation Commission (CARF).

The term "acquired brain injury" includes:

• Traumatic brain injuries, such as open or closed head injuries
• Non-traumatic brain injuries, such as
  • those caused by strokes and other vascular accidents
  • tumours
  • infectious diseases e.g. encephalitis
  • hypoxia
  • metabolic disorders e.g. liver disease
  • toxic products taken into the body through inhalation or ingestion e.g recreational drugs

Causes of Damage

There are a number of ways by which a viral infection of the brain may damage nerve cells.

• Viruses can enter nerve cells and hijack components of the cell to replicate (make copies of itself).  This may be serious enough to kill the cell.
• The characteristics of the cell membrane may be altered, disturbing the electrical properties of the nerve cell.
• Infected cells may be killed by the body’s immune system to limit the viral infection.  This collateral damage may cause brain dysfunction.
• Byproducts of the body’s defence against the infection (white blood cells, the contents of dead nerve cells and disabled viruses) can significantly alter the fluid surrounding nerve cells and affect their functioning.
• Swelling resulting from additional fluid entering the brain can compress the brain resulting in brain dysfunction.

Cell damage and death can, therefore, be caused both by the viral infection and by  the extreme pressure resulting from the inflammation.  Some loss of brain function is 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.

The degree and type of damage will vary according to the severity of the infection and the parts of the brain that have been attacked. The damage may be limited to one part of the brain (focal), in several parts of the brain (multifocal) or throughout the brain (diffuse). It is the combination of location and severity which  will determine the pattern of difficulties that remain after the illness.

Consequences of Damage

Significant changes may occur in personality and in the ability to function day to day even if there is a complete physical recovery.  Coming to terms with these problems can be very distressing and challenging for everyone concerned. The child or adult you knew, or who was you, may have changed and the child or person they have become, or you have become, may present with a number of problems.

It is important not to underestimate the time that the individual and the whole family will need to adjust, in both practical and emotional terms, to their new situation.  Those involved have, in effect, suffered a complicated form of bereavement; it is not unrealistic, therefore, to think of allowing at least two years to come to terms with what has happened. The kind of knowledge needed in order to come to terms and cope with these problems does not reside in the pages of a medical textbook nor with medical experts. It comes from knowing what it is really like to have encephalitis.

Last modified – 25/06/05