Immediate Injuries To The Brain

The injuries that are caused by trauma are divided into two separate categories: immediate and delayed injuries.

Immediate injuries are those that occur immediately at the time of injury and are due to the physical forces injuring or disrupting parts of the brain. There are two main types of immediate brain injuries: contusions and diffused axonal injury (DAI).

Contusions are bruises. Having a bruise to the brain certainly doesn’t sound good. When an area of the brain is bruised, some cells in that area of the brain can be totally disrupted or broken apart, and then die. Other cells can be permanently injured or stunned, and therefore unable to function properly. This damage can be permanent, or it can be temporary. It all depends on the severity of the brain injury.

Where contusions are located depends on the circumstances of the injury. If a stationary head is with an object ( like a brain getting struck with a hammer), the contusion will be in the cortex at the point of contact, and there will possibly be another bruise on the opposite side of the brain (180 degrees from the other bruise) These are often called “coups” or hits and “countercoup” contusions. This is not how contusions are typically distributed with a severe Closed Head Injury.

With a severe injury, such as in a car accident, there is usually more speed and energy involved in the impact; and the head is moving from the time of the accident. The contusions with this type of injury usually occur as the head is suddenly stopped, and then a split second later, the brain is suddenly stopped by hitting itself against the inside of the skull. This results in the brain crushing itself on prominent rough parts of the inner table/surface of the skull. Consequently, contusions with severe TBIs tend to occur in the areas of the frontal lobes, the temporal lobes, and the brain stem.

Diffuse Axonal Injury (DAI) is an injury to the axons (the extensions of neurons or nerve cells) which are located diffusely in the brain ( meaning all over the brain and not in one specific location). This injury is also referred to as a shearing injury. Because axons often extend long distances in the brain, they are particularly vulnerable to twisting movements of the brain at the time of injury. As the head and brain are accelerated and spun violently and then brought to a quick stop, the brain is twisting on itself. This can stretch the axons so far that they are physically pulled apart. This results in an immediate loss of function of that neuron, and in its death. As with contusions, certain parts of the brain are more vulnerable to DAI.

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