What are the categories of brain trauma?
There are are two separate categories of trauma to the nervous system that can happen: trauma to the brain itself, otherwise known as traumatic parenchymal injuries, and trauma to the brain’s blood vessels, otherwise known as traumatic vascular injuries.
Under the category of traumatic parenchymal injuries, there are four types of injury: contusions (which can be further subdivided into coup injuries and contrecoup injuries), lacerations, concussions, and diffuse axonal injury. I’ll discuss each of them below.
Under the category of traumatic vascular injuries, there exist two different subtypes: epidural and subdural haematomas, which I’ll discuss in a page called Haematomas.
Effects of Contusion
The causes of contusion include the following: rapid displacement of tissue (through force), disruption of blood channels, haemorrhaging (bleeding), tissue injury and swelling. The words ‘coup’ and ‘countercoup’ are pronounced like ‘ballet’: the final letter is dropped, hence they actually sound like ‘coo’ and ‘countercoo’ respectively.
Coup injuries are contusions that are sustained at the area of impact. For example, if you hit your head during a crash in a vehicle (whether it be a car, a bus or on a plane), you would usually lean forward due to inertia (the force keeping you in motion during rapid braking according to Newton’s first law of motion) and hit your head against an object in front of you. This effect would be worsened if you don’t wear a seat-belt, because there would be nothing to push you back into your seat. In planes, the position known as ‘brace’ is designed to minimize head injury by placing your head either on the seat in front (in economy class) or on your legs (in business class).
Contrecoup injuries happen on the opposite side of the coup injury. A classic example of a contrecoup injury is sustaining whiplash during a minor car crash. Modern cars have adjustable head cushions as a safety feature to prevent whiplash from happening, but older cars didn’t have this feature, so therefore it was possible for the back of the head to sustain injury as well as the front.
Lacerations are defined as injuries that involve penetration of the brain from the outside in. The only way that this injury can be corrected is via surgery to remove the cause. This can happen in one of two circumstances:
- Fracturing of the skull, leading to skull fragments falling into the brain cavity
- Gunshot wounds
There are several symptoms associated with lacerations: tissue tearing, disruption of the blood vessels, bleeding in the brain and (under the second circumstance due to the speed of the weapon) injury along a straight path.
Concussion happens when there is a hit to the head, but there is no visible sign of injury. A scenario where this can happen is if you accidentally faint and hit the floor: your head may be injured but there might be only minor bleeding or nothing obvious at all to indicate something is wrong. Common symptoms of concussion are temporary loss of consciousness, temporarily not breathing, and a lack of response from your nervous system when tested with a reflex hammer, like the one pictured alongside. These symptoms generally resolve themselves within a day, however amnesia (loss of memory) may happen regarding the event that led to the concussion in the first place.
Diffuse Axonal Injury
As the name suggests, diffuse axonal injury is injury involving the axons within our brain cells. This tends to happen during a severe collision, where the force of the collision leads to swelling of the brain, development of lesions in the brain stem and within the ventricles and may eventually lead to a coma. This often happens in conjunction with the brain haemorrhaging (bleeding).