Head injuries and their severity vary significantly. Initial assessments are often measured according to the Glasgow Coma Scale (GCS) which looks at levels of consciousness and neurological functioning, and subsequently described as mild, moderate or severe.
However the classification of each of these can differ considerably according to which research study you look at.
In one study ‘mild’ injury is classified as loss of consciousness for less than 20 minutes, no deterioration in CGS score, no focal neurological deficit or complication, no intracranial mass lesion or intracranial surgery.
‘Moderate’ is defined as 9-12 on the GCS with complication focal brain lesions seen on CT scan.
‘Severe’ injury is defined as 3-8 on the GCS where loss of consciousness exceeds six hours.
Another defines a mild head injury as including no fracture and any loss of consciousness or post traumatic amnesia for less than 30 minutes. Moderate is characterised by loss of consciousness or post-traumatic amnesia lasting 30 minutes to 24 hours or a skull fracture. Severe head injury includes brain contusion, intracranial haematoma or loss of consciousness or post-traumatic amnesia for more than 24 hours.
Post traumatic amnesia refers to the period from the injury until the individual can form a reliable and continuous record of on-going events in memory. It is a transient state characterised by anterograde amnesia and attentional disturbance, sometimes accompanied by more bizarre behaviour such as gross disinhibition and hallucinations. It often terminates abruptly even though the patient may show persistent cognitive and memory deficits. It encompasses any period of loss of consciousness although a brain injury can cause disorientation and post-traumatic amnesia even when there has been no loss of consciousness.
Estimating the exact duration of post traumatic amnesia is difficult and often complicated by the fact it is not usually assessed reliably during the inpatient stay, and patients can be discharged home whilst in this state. Nonetheless, the length of post traumatic amnesia can be a good indicator of injury severity and a good prognosis indicator for long term cognitive recovery.
Cognitive deficits following moderate to severe head injuries are well recognised and include for instance, abnormalities of memory, language, visual perception, attentions – concentration and executive functioning.
Memory abnormalities are common particularly in patients who have suffered moderate to severe head injury including frontal and anterior temporal lobe damage. The severity and permanence of the memory loss is dependant upon the severity and location of the head injury. One study found that seven years after severe head trauma, memory deficit was the single most frequent symptom reported by 53% of the patients and by 79% of their relatives.
Find out more about the Glasgow Coma Scale in the document below.
Glasgow Trauma Scale (270.9 KiB)
Read more about minor head injuries here.