The brain is arguably the human’s most precious organ. It is well protected by the skull, but it is large and heavy and so is prone to injury, especially from blows that rapidly accelerate and then decelerate it within the confines of the skull. Significant injuries to the brain lead to a temporary shut-down of higher functions (concussion). However, it must never be forgotten that unconsciousness can also be coma, or a result of stroke, hypoglycaemia, epilepsy or drugs. So, the loss of consciousness may have been the cause of the accident not the result.

The key to the management of most head injuries is ensuring that the brain remains well perfused in the post-injury and recovery period. Failure to keep the airway clear, the blood well oxygenated and the brain well perfused may lead to so-called ‘secondary injury’ to the brain. This damage should be avoidable.

As in any serious injury the initial management is ABC (see Chapter 42) followed by an assessment of conscious state and a check for any other injuries. Patients with serious head injuries may not be making any effort to breathe or may have lost their gag reflex. Early endotracheal intubation may be needed to keep the patient well oxygenated, and to protect the airway from inhalation.

Assessment of conscious state is initially made using AVPU (see below), but later the Glasgow coma scale should be used which gives marks for the best response in a set of different areas (response to verbal command, response to pain, eye movements). An early measure of the conscious state is valuable because it is any subsequent change in the conscious state, rather than the absolute level that guides further investigation and treatment. If the conscious state starts to deteriorate, always check ABC before looking for neurological causes.

A scan of the brain is needed if intracranial bleeding is suspected but the patient must first be made safe to enter the scanner.

Cuts on the scalp

These bleed profusely and can cause hypovolaemic shock. They should always be explored in case they lie over a fracture or even a penetrating wound into the brain itself.

Fractured skull

A fractured skull is of no great significance in itself unless it is depressed and fragments are pressing into the brain. However, it is an indication of the severity of trauma, and if close to a blood vessel may provoke an intracranial bleed. If the fracture is open then blood mixed with cerebrospinal fluid will flow out of the ear, nose or wound and prophylactic antibiotics need to be given to protect against meningitis.

Extradural haemorrhage

Fractures near cranial arteries – especially the middle meningeal artery (running up the side of the skull by the temple) – may tear the artery itself. This produces bleeding between the skull and the dural membrane, which will slowly start to compress the brain over a period of hours. Classically the patient has a short period of unconsciousness (concussion) followed by a recovery of faculties. However, some time later, after this lucid interval , the patient may start to develop localising signs of raised intracranial pressure, with weakness on the side opposite to the lesion and a fixed dilated pupil on the side of the lesion.

Rapid recognition of the possibility of an extradural haemorrhage should result in immediate imaging using a CT scan or MRI, followed by surgical decompression using burr holes, followed by raising a flap. The moment that the pressure is relieved the patient miraculously recovers.

Subdural and intracranial haemorrhage following trauma

These can be diffuse or localised. Diagnosis is best made by CT or MRI. Treatment in the first instance is to avoid ‘secondary injury’ by making sure that the patient is well perfused and well oxygenated.

Brain injury

Direct damage to the brain itself will be made worse by bleeding and swelling secondary to the trauma of the injury. Controlled dehydration, hyperventilation reducing blood carbon dioxide and high-dose steroids are all used to try to minimise the secondary damage caused by the brain swelling inside a rigid container (the skull), but so far there is no conclusive evidence that any of these techniques improve the outcome. However, what does make a difference is making sure that the brain is well perfused and well oxygenated.

Chronic sbdural haemorrhage

In the elderly a trivial fall can lead to a small subdural haemorrhage that may continue to expand long after the original trauma has been forgotten. The patient may show a gradual deterioration in mental faculties over a period of weeks or even months. The underlying cause will only be revealed once a scan has been performed.

Raised intracranial pressure

In the acute phase of raised intracranial pressure, the patient’s conscious state will be depressed and respiration will be reduced, as will the pulse, although paradoxically blood pressure may go up (the opposite of hypovolaemic shock). If pressure continues to rise, the patient’s conscious state will deteriorate and they will become rigid and spastic (decerebrate). Eventually the brainstem will be driven down into the foramen magnum, leading to coning and death.

Although the central nervous system is thought to have very limited powers of regeneration, the brain does seem to be able to achieve some recovery by plasticity – recruiting new pathways to perform tasks where the old pathway has been damaged. This appears to occur much more easily in the young than in the old, but either way occurs over a period of many months. During that time the patient will need considerable social and physical support, as their personality can be profoundly altered and their behaviour may become very disruptive.