Among men under the age of 35 motor vehicle accidents and violent crime are a major cause of death. 70% of them die of head injuries. Of people who survive head injuries, around 20% are left with brain damage of varying severity.

Minor head injuries are so common that no GP is without experience of their treatment.

Head injury is frequently found associated with spinal cord injury.

In Western countries the last 20 years have seen a decline in mortality and subsequent disability from head and spinal cord injuries due to the use of seat belts in cars, motor cycle helmets and improved training of ambulance personnel who are first at the scene of an accident. We have yet to see a similar improvement in South Africa, although the recent Arrive Alive campaign led to a decrease in the number of accidents over the past holiday season in some provinces.

Types of head injury

Skull fractures

There is significant underlying brain damage in two thirds of skull fractures, so their presence indicates the need for further investigation of the underlying brain. They can also result in injuries to the cranial nerves which supply the head and neck, because of the position of these nerves both on the skin overlying the skull and at their origin in the brain stem. Obviously if the skull is broken, that allows a pathway for bacteria and other pathogens to enter the fluid bathing the brain, the cerebrospinal fluid, so causing infection.

Cranial nerve injuries

The cranial nerves are a group of nerves supplying the face, head and neck. They arise in the brain stem, which is situated at the base of the brain where it joins the spinal cord. Consequently they are most liable to be injured in fractures of the base of the skull.

The nerves most often affected are those supplying smell, eye movements, hearing, facial movements and facial sensation.

Concussion

This typically occurs with blunt impact or so-called deceleration injuries to the front or back of the skull which produces sudden movement of the brain within the skull. There is an immediate, but short lived loss of conciousness, the person often described as "dazed" and a brief period of amnesia.

There may be a brief convulsion, faintness, pallor, slow pulse and low blood pressure in severe cases. However, most people with concussion are neurologically normal.

If someone loses consiousness after hitting their head they must have a skull X-ray to exclude a fracture. About 3% of people who have experienced concussion will have an intracranial (within the skull) bleed. The presence of an associated skull fracture increases this risk many times.

Contusion, brain haemorrhages and shearing lesions

Contusions, or bruises, on the surface of the brain, and deeper haemorrhages (bleeds) result from the mechanical forces which move the brain relative to the skull. These occur when the head is struck with enough force to cause the brain to move slowly within the skull relative to the speed of the head. This results in the brain hitting the inside of the skull, either at the point at which the head has been struck, or on the opposite side of the skull.

These injuries are common in boxing, and in car accidents at speed, particularly when the head hits the dashboard or windscreen.

Clinical signs of contusions vary according to their position, but a stroke like picture is common. Extensive bruising leads to coma.

Widespread disruption of the white matter of the brain can be caused by shearing of the axons, which carry nerve impulses between nerve cells, usually occurring at impact. Widespread shearing injury will also lead to coma.

In some cases there is extensive brain swelling within a few hours of head injury, generally caused by multiple bruising over the surface of the brain. The effects of this are disastrous since the brain swelling causes widespread disruption in all functions. It is most common in young adults and children probably due to disruption of the small blood vessels in the brain, increased blood pressure and increased blood flow to the brain.

Deep cerebral haemorrhages, or bleeds, can occur several days after serious injury. This will result in a sudden deterioration, often in an already comatose patient.

Subdural and epidural haematoma

A tough, fibrous sheath called the dura lines the inside of the skull. A haematoma is a build up of blood.

In serious head injury, bleeds beneath the dura (subdural) or between the dura and skull (epidural) may be associated with contusions and other injuries.

These can also occur in isolation, each with a characteristic clinical picture and appearance on investigation.

An acute subdural haematoma may be symptomatic within minutes to hours of injury. Most people are drowsy or comatose from the moment of injury, but around one third are lucid for a while before becoming comatose. People who are rousable often complain of a headache on one side of the head, and often have an enlarged pupil on the side of the bleed.

CT scan is the best investigation for an acute subdural bleed.

Subacute subdural haematoma occurs in the elderly and in alcoholics where drowsiness, confusion and headache may be seen days to weeks after the injury.

These injuries can occur with direct trauma, or indirectly, through the acceleration forces of something like whiplash injury. This latter is particularly common in the elderly.

Acute epidural haematoma occurs more rapidly and so tends to be more dangerous. They occur in 1 to 3% of all head injuries and in up to 10% of severe injuries. They are less often associated with underlying brain damage than subdural haematoma.

Most patients are comatose when first seen, although the history and physical findings may be similar to those of subdural haematoma, but occurring more quickly.

Chronic subdural haematoma is seen mainly in the elderly, where there may or may not be a clear history of a preceding injury. In fact 20 to 30% do not have a history of injury. In some cases the bleeding may occur spontaneously, or they may be a history of relatively minor head injury such as hitting the head against a tree branch, or falling when fainting.

There is a period of weeks, or even months, when the elderly person becomes increasingly confused, with personality changes, complains of a fluctuating headache, and shows some weakness on one side of the body. There may also be seizures.

Diagnosis is often difficult since this picture can be seen in a number of other neurological conditions. There is generally little progression and coma is rare.

Penetrating injury, compressions and lacerations

Obviously the clinical picture in each of these will vary widely according to the position of the injury or missile within the brain.

A bullet injury causes a rapid increase in intracranial pressure initially, followed by a drop depending on how much bleeding there is.

The risk of infection is high after something has penetrated the brain, and treatment by exploring for bleeding tissue and removing dead tissue is necessary after removing the foreign body.

Damage to the vessels of the neck can occur with trauma to the neck, either by a blow or whiplash. This can happen after relatively minor neck injury, so must always be excluded in a patient with headache and neck pain following injury.

How are head injuries treated?

Any patient with anything other than the most minor head injury is assessed according to the Glasgow Coma Scale. In this the patient is scored according to a number of neurological criteria. For example is the patient orientated, will they obey commands and do they open their eyes spontaneously? This is then translated into eye opening (E), best motor response (M) and best verbal response (V). The Glasgow Coma Score is then E+M+V. The maximum possible score is 15 which would indicate a fully orientated person, responding to commands and lying with their eyes open. Patients scoring 3 or 4 have an 85% chance of dying from their injuries or remaining comatose. Intermediate scores correlate with proportional chances of recovering.

Treatment will depend on the nature and site of the injury. In some cases injury may be so profound that lifesaving treatment is not warranted. In this case the doctors looking after the patient will discuss options with the relatives. It is always worth considering organ donation in this case. Although a difficult decision to make when faced with the death of a loved one, the advances in organ transplant surgery now are such that this sacrifice may allow someone else to lead a full and productive life as a result of your generosity.