Types of Traumatic Brain Injury

In addition to the severity of a brain injury, the type of injury can make a difference in a person’s recovery.

For instance, focal and penetrating injuries tend to injure specific portions of the brain. A person with this type of injury may have less overall damage as a result, depending on where the injury occurs and the cognitive processes involved in the damaged area of the brain. In contrast, a person whose head hits the pavement after a fall may injure both the area of the brain at the point of impact and the opposite side of the brain as well. This is called a coup-contrecoup injury. This type of injury may become diffuse because of the shearing and tearing that can occur as the brain moves back and forth within the skull.

Other possible types of damage include contusions or bruises that result in swelling. Rotation injuries also result in shearing and tearing of brain tissue. When a baby is shaken, the brain often has several types of injuries including coup contra coup, rotation injuries and swelling. In this, as well as similar injuries to older children, the blood vessels tear causing internal hemorrhaging in addition to the direct damage to the brain tissue.

Most brain injuries are compised of a mix of both primary and secondary injuries. The more severe the initial insult, the more likely the secondary injuries will have a major effects on the person's overall outcome

Primary Injury

Primary injuries include the injuries that are sustained at the time of the traumatic event, such as:

Intracranial Hemotomas

Intracranial hematomas are the rupture of a blood vessel leading to the collection of blood in brain tissues or empty spaces. There are several types of hematoma:

• Epidural Hematoma: A blood clot outside of the brain and the dura but under the skull.
• Subdural Hematoma: A blood clot between the brain and the dura.
• Subarachnoid Hemorrhage: Bleeding withing the layers of the dura, specifically under the aracnoid layer.
• Intracerebral Hematoma: Bleeding within the brain tissue itself caused by the rupture of a blood vessel within the brain.
• Intraventricular Hemorrhage: Bleeding into the ventricles of the brain

Skull Fractures

Skull fractures are a concern because a disruption in the skill can cause injury to the brain or provide an open avenue for infection or both.

• A linear skull fracture is a break in the skull resembling a thin line or crack. These unjuries are usually moitored and not treated sugically.
• A depressed skull fracture is a break in or crushing of part of the skull. These types of skull fractures may require elevation of the skull through craniotomy to prevent increased pressure on the brain.
• A basilar skull fracture occurs at the base of the brain and can cause leakage of cerebral spinal fluid.

Contusions/Coup-Countrecoup

A contusion, or a coup-contrecoup injury, is a bruise of the brain tissue. With this type of injury, flexion-extension or acceleration-deceleration results in the formation of a linear, anterior-posterior lesion at the point of impact. Injuries can also be lateral or side-to-side. This is the type of injury that occurs in a motor vehicle crash, where the head is propelled forward and accelerated and then moved back in deceleration.

Diffuse Axonal Injury (DAI)

Diffuse axonal injury or DAI usually results from rotational forces or violent stopping.Unlike brain trauma that occurs due to a direct blow, DAI is the reult of twisting and tearing of the connections between the cells of the brain.

Secondary Injury

Secondary brain injury results fro metabolic and physiologic changes that bedin at the time of the initial injury and may last for hours and days, such as:

• Hypoxia and Hypotensions
• Ischemia
• Cerebral Edema - resulting in increased intracranial pressure
• Hydrocephalus
• Second Impact Syndrome - an extremely rare outcome where death or severe neuroloic injury occurs when a person sustains a scond concussion before symptoms from an earlier one have subsided.

Penetrating vs. Closed BInjury

Traumatic brain injury (TBI) is commoly catorized as penetrating or closed.

Pentrating TBI: An injury in which the dura, the outer latyer od the meninges, is compromised. Penetrating injuries can be caused by high velocity projectiles (such as bullets and fragments) or objects of lower velocity (such as knives or bone fragments). Only 1-2% of TBIs are penetrating head injuries. Closed TBI: An injury in which the dura remains intact. It is further classifies as mild, moderate and severe. Mild TBI is also know as concussion.

Most brain injuries are comprised of a mix of both primary and secondary injuries.

The more severe the initial iinsult, the more likely the secondary injuries will have a moajor effect on the person's overall outcome.