Causes

The greatest cause of head injury in the developed world is road traffic accidents.  The vulnerability of motorcyclists, cyclists and pedestrians make them high risk especially if preventative measures such as wearing a helmet are not taken. Other common factors are falls, high risk sports such as boxing, work related accidents, assault and alcohol related injuries.  Unfortunately these causal factors mean that over 50% of head injuries in the UK occur in males under 20.  Head injuries in the elderly are often a result of falls and accidents around the home.  This is also true for very young children, however child abuse must also be taken into account as a major factor in this age group.

Traumatic brain injury can be classified as either 'closed' or 'open'  and is rated in terms of severity.  This will depend on how the injury was aquired and the impact of the injury on the persons mental and physical health such as cognitive and motor functions.

Closed Injuries

Closed head injuries are often a result of forceful accleration, deceleration or rotational forces such as in a road traffic accident.  They are characterised by a lack of an 'open' wound or damage to the skull but result from movement of the brain within the skull.  This movement can 'pull' on the nerve fibres and blood vessels within the brain resulting in diffuse (all over) damage.  As well as the diffuse injury, local damage can also occur.  These types of injuries do not require the head to actually hit a solid object but can result from a phenomenon called 'coup and countercoup' in which the brain hits the front of the skull (coup injury) and then bounces back and hits the back (countercoup injury).  Injuries where the head hits an object with great force (such as the steering wheel) may mean that only the 'coup' injury occurs but this will also be accompanied by diffuse damage.  Mild forms of this type of injury are often referred to as concussion.

Open or Penetrative Injuries

Penetrative head injuries are characterised by a lesion to the skull and underlying tissue surrounding the brain (dura) as well as the brain itself.  They are often the result of a local blow to the head such as assault with an object.  These types of injuries are more likely to result in symptoms that are asscoiated with loss of function in the damaged area.  However, they are very commonly associated with diffuse damage due to the forces that are involved and the over all effects of bleeding and damage to the brain.

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