Head injury
Clinical aspects
Assessment and management
The best indicator of head injury severity is impairment of consciousness. This either reflects brain stem dysfunction or diffuse hemispheric damage. Level of consciousness is assessed using the Glasgow Coma Scale (GCS) which quantifies responses to verbal and painful stimuli in terms of eye opening, speech and movement (Fig. 9.1). The aggregate score ranges from a maximum of 15 (alert and orientated) to a minimum of 3 (comatose or dead).
A GCS score of 13–15 corresponds to mild head injury, accounting for the majority of cases. A total score of 9–12 represents moderate head injury, whilst a score of 3–8 signifies severe head injury. In addition to providing an initial assessment of severity, any reduction in the GCS score is a sensitive indicator that the clinical state has deteriorated. This may signify development of a secondary complication requiring urgent intervention. The role of imaging in the assessment of head injury is discussed in Clinical Box 9.1.
Outcome following head injury
Factors that predict a less favourable outcome include increasing age (>60 years), an initial GCS score below 5, a fixed and dilated pupil, a prolonged period of hypotension/hypoxia or a haemorrhage requiring surgical decompression. Late complications may include hydrocephalus due to obstruction of CSF drainage pathways (see Ch. 2, Clinical Box 2.2) or seizures (Clinical Box 9.2).
Pathology of head injury
Cerebral contusions
Cerebral contusions (bruising) and lacerations (tears) are common in traumatic brain injury, occurring in more than 90% of fatal cases. Contusions are most pronounced at the crests of gyri in the frontal and temporal lobes, particularly in places where the brain comes into contact with the irregular contours of the skull base (Fig. 9.2). Cerebral contusions may be associated with haemorrhage into the overlying subarachnoid or subdural spaces and if blood continues to accumulate it will begin to act as an intracranial mass lesion. The combination of a cerebral contusion with an overlying subdural haemorrhage is called a burst lobe. This most often occurs at the frontal and temporal poles.