Understanding Brain Injury

Scientific understanding of the workings of the brain continues to develop but there is still much that is not well known, and it is still not possible to reliably predict the outcome in many patients who have suffered a head injury.

Practitioners often use the words ‘head injury’ and ‘brain injury’ interchangeably, but whilst a brain injury will be a serious type of head injury, a head injury will not necessarily involve damage to the brain. For instance, concussion is commonly caused by a blow to the head but without any measurable damage to the brain, and the symptoms can be short lived with a full recovery. In other cases the patient may suffer headaches and impaired mental function for years without having recognised damage to the brain; a bleed in a blood vessel outside the brain may cause symptoms but not from damage to the brain itself.

A brain injury is usually – but not always – diagnosed by scanning. An MRI scan or CT scan will demonstrate any bleeding within the brain, any lesions, haemorrhages, skull fractures or shift in the structure of the brain tissue.

There are often three phases of a brain injury, where the first is the initial injury, the second represents the damage caused by interrupted oxygen supply in the minutes after the injury, and the third is bleeding and swelling that occurs over the following hours and days.

A head injury can be referred to as ‘open’ or ‘closed’. An open head injury refers to a penetrating injury, where an object such as a weapon enters the skull and damages the brain. These injuries are often fatal but are thankfully quite rare. In a closed injury the skull is not penetrated (although it can be fractured) and the damage is done by violent movement within the skull on impact or through shaking. The brain is a delicate and soft substance, and these violent forces can cause it to be sheared and bruised.

There are conventional measures which indicate the severity of a head injury. Reduced consciousness is measured by a 15 point test called the Glasgow Coma Scale. Anything less than 15 will indicate a degree of impaired consciousness but in many cases that reading will return to normal and there will be no lasting damage. Generally, the lower the score the more serious the injury.

The period of reduced consciousness is at least as important as the degree of reduced consciousness in assessing severity and outcome. It can be a matter of hours in more minor head injury cases and days or weeks in more serious brain injury cases. This does not mean that the patient is in a coma but it does mean that their level of awareness and understanding, and sometimes their physical functioning, are impaired. The period of reduced consciousness is called Post Traumatic Amnesia.

It is very common for people who suffer head injuries in an accident to have no recollection of the accident at all. Some have an even earlier period loss of consciousness, where they cannot recall events before the accident (retrograde amnesia), and this again is seen as an indicator of a more serious injury.

Other early indicators will include nausea and vomiting, impaired speech, balance or vision and headache.

A ‘minor’ head injury will usually resolve naturally within weeks or months, but will still involve unpleasant symptoms such as headaches and dizziness, fatigue and anxiety.

A ‘moderate’ head injury will usually include a period of Post Traumatic Amnesia (PTA) of up to 24 hours. Symptoms will often improve, and may completely resolve, but some patients continue to suffer in the longer term.

A longer period of PTA may be classified as a ‘severe’ or ‘very severe’ head injury and in these cases the patient is often left with long term disability from problems with brain and sensory function, and sometimes motor function.