An estimated 1 million people in Britain attend hospital each year as a result of head injury. Of these:
- 150,000 will suffer a minor head injury resulting in unconsciousness for 15 minutes or less
- 10,000 will suffer a moderate head injury, resulting in unconsciousness for up to 6 hours and after 5 years some will still have physical or psychological problems
- 11,600 people will suffer head injury and remain unconscious for six hours or more and after 5 years only 15% will have returned to work.
Road traffic accidents account for between 40%-50% of all head injuries and are often the cause of the most severe. It is important to note that you do not have to be traveling at a high rate of speed to get a head injury. You do not have to hit your head on an object (steering wheel, windshield) to injure the brain. Even at moderate rates of speed, traumatic brain injuries can and do occur. Domestic and industrial accidents cause between 20% and 30% whilst most of the rest are caused by sports and recreation (10%-15%) and assaults (10%).
Three separate processes work to injure the brain:
bruising (bleeding), tearing, and swelling.
BRUISING (BLEEDING)
If a person is driving a car at 45 miles per hour and is struck head-on by another car traveling at the same rate of speed, or hits a wall or a tree, the person’s brain goes from 45 miles per hour to zero in almost an instant. The soft tissue of the brain is propelled against the very hard bone of the skull. The brain tissue is catapulted against the skull and blood vessels may tear. When blood vessels tear, they release blood into areas of the brain in an uncontrolled way.
Why do medical experts seem so concerned about bleeding in the brain? A major problem is that there is no room for this extra blood. The skull, being hard and brittle, does not expand. So the blood begins to press on softer things, like brain tissue. Brain tissue is very delicate and will stop working properly or may even die off. With large amounts of bleeding in the brain, the pressure will make critical areas of the brain stop working. Areas that control breathing or heart rate could be affected, and a life or death situation could develop within hours of theaccident. Some people have sustained a head injury from a car accident and seem fine immediately after at the accident. Some have even got out of their car and directed traffic. Within a short period of time, they began to get more and more confused until they eventually lapse into a coma. So, you can see why emergency doctors or paramedics at the scene of the accident are so anxious to get people to a hospital following a car accident.
There is also an "odd" thing that the brain goes through during a car accident. The brain, which is very soft, is thrown against the front part of the skull, which is very hard, and bruising can happen. But the injury process is not over. The brain and rest of the body, flies backward. This bouncing of the brain first against the front of the skull and then against the back of the skull, can produce bruises in different parts of the brain. Thus people can have a bruise not only where their foreheads hit the steering wheel, but other areas of the brain as well. Doctors call this a "contra coup" injury.
TEARING
At some point in time, we’ve all played with jelly. If you slice a cut into a square of jelly with a knife and let it go, the jelly will come back to shape if you jiggle it. It will look perfectly good up until the time you come to lift it up, and there will be the slice. The brain has a consistency slightly firmer than jelly, but the same effect applies. In the case of the car accident, the brain is thrown forward, then bounced backward (remember those car commercials where the crashdummy flies forward, then comes flying backward). In this forward/backward motion, the brain can be torn. The brain can also be torn by the effects of "energy". If you take a block of ice and hit it with a hammer (assuming you don’t completely shatter the ice), you will see little cracks in the ice. Energy from the hammer has been transferred to the ice, producing the web-like cracks. Tearing in the brain is very serious. Tearing in the brain "cuts" the wires that make the brain work.
One of the problems with tearing is that it happens on a microscopic level (the brain has about 100 billion of these "wires"). This tearing may not show up on typical medical tests. Devices that take pictures of the brain will not see these small tears. Two common ways of viewing the brain are with a CT Scan (using X-rays) and an MRI (using magnetic fields) to create pictures of the brain. Both of these techniques are very good at seeing blood and tumors in the brain, but they are not good with tears (which are very small). In a number of medical studies with people who have head injuries, only 10 to 15 percent had "positive" CT Scans or MRI findings. By the way, a "positive" in the medical business is NOT necessarily a good thing. It means that they found something that is abnormal in the brain.
SWELLING
If I drop a bowling ball on my foot, my foot will turn "black and blue" due to blood leaking under the skin. But my foot will also do something else, it will swell up. The body realizes that the foot has been injured and sends agents to heal the injured area. The problem with the brain is that there is no extra room and the pressure begins to build up. This pressure pushes down on the brain and damages structures in the brain. If there is too much pressure, this can stop important structures that control breathing or the heart rate. A neurosurgeon, in these circumstances, will perform surgery on the brain, by removing a portion or flap of bone, and carefully searching out and removing the clots that have formed by reason of the intra cranial bleeding and thus reducing the pressure caused by the bleeding. Sometimes they will install a "relief valve" (intra-cranial pressure monitor or ICP) to let off any excess pressure.
OPEN VERSUS CLOSED HEAD INJURY
Not that long ago, doctors made the distinction between open and closed head injury. In an open head injury, the skull is fractured and doctors assumed this would produce a severe head injury. In closed head injury, the skull is not broken and doctors assumed these produce less severe injuries. Wrong! In closed head injury, pressure builds up and damages brain tissue.
MILD OR SUBTLE BRAIN INJURY
This has been dealt with separately at the end of this book, not because it is less important but because it deserves a section of its own.
THE GLASGOW COMA SCALE
You may have heard about this and wondered what it is and what it means in the context of a traumatic brain injury. The Glasgow Coma Scale is the most widely used scoring system around the world and is used to assess the level of consciousness following traumatic brain injury. It is used primarily because it is simple, has a relatively high degree of reliability and because it dovetails well with outcome following severe brain injury.
It is easy to use, particularly if a form is used with a table similar to the one below. It determines the best eye opening response, the best verbal response, and the best motor response of the victim. The score represents the sum of the numeric scores of each of the categories. Have a look at the table. There are limitations to its use. If the patient has an endotracheal tube in place, they cannot talk. For this reason, many prefer to document the score by its individual components; so a patient with a Glasgow Coma Score of 15 would be documented as follows: E4 [meaning a score of 4 – opened eyes spontaneously - on the eye openingtest] V5 [meaning a score of 5- the victim talked normally - on the verbal response test] M6 [meaning a score of 6 – normal physical responses – on the motor response test.]. An intubated patient would be scored as E4 Vintubated M6. Of these individual factors, the best motor response is probably the most significant.
Other factors which alter the patients level of consciousness interfere with the scale’s ability to accurately reflect the severity of a traumatic brain injury. So, shock, hypoxemia (compromised oxygen to the brain), drug use, alcohol intoxication, metabolic disturbances may alter the GCS independently of the brain injury. Obviously, a patient with a spinal cord injury will make the motor scale invalid, and severe eye trauma may make eye opening impossible to assess. The GCS also has limited use in children, particularly those less than 36 months. In spite of these limitations, it is quite useful and is far and away the most widely used scoring system used today to assess patients with traumatic brain injury.
Glasgow Coma Score Table
| Eye Opening |
E |
Best Verbal |
V |
Best Motor |
M |
| spontaneous |
4 |
oriented and converses |
5 |
obeys commands |
6 |
| to voice command |
3 |
confused |
4 |
localizes to pain |
5 |
| to pain stimuli |
2 |
inappropriate words |
3 |
withdrawals from pain |
4 |
| no response |
1 |
incomprehensible sounds |
2 |
decorticate posturing |
3 |
| |
|
no sounds |
1 |
decerebrate posturing |
2 |
| |
|
|
|
no response |
1 |
|
E + V + M = 3 to 15
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