Types Of Traumatic Brain Injuries
Traumatic brain injury, or TBI, includes both primary and secondary brain injury and is a factor in over 30 percent of trauma-related deaths. TBI can be classified according to the type of trauma, with multiple subcategories. It can also be classified by severity.
A traumatic brain injury, or TBI, occurs when an external force impacts the head and causes brain damage. In 2010, the Centers for Disease Control and Prevention estimated that TBI accounted for 2.5 million emergency department visits, hospitalizations and deaths. This does not include people who were treated for TBI in a health care provider’s office or did not receive treatment. Worldwide, TBI is a factor in over 30 percent of trauma-related deaths.
According to data from the Rhode Island Department of Health, the overall incidence of TBI in Rhode Island is slightly lower than in the United States as a whole. The most common cause of TBI in Rhode Island is unintentional falls, which account for 48 percent of cases of TBI.
Most falls occur in children under age 5 or in older adults. Motor vehicle crashes and striking or being struck by an object, which often happens to athletes, were the next most common causes of TBI in Rhode Island.
TBIs can be classified in a few different ways, including by whether the skull was penetrated, by the severity of the injury, and by the timing of the damage.
Types Of TBI
Doctors commonly classify TBI into two major categories: penetrating head injuries and closed head injuries.
Penetrating Head Injuries
In a penetrating head injury, also known as an open head injury, an object, or part of an object, pierces the skull as well as the outer covering of the brain. This is the most severe type of TBI, and it carries the worst prognosis.
Penetrating head injuries are less common than closed head injuries. Because they’re more severe, they represent a majority of the deaths caused by traumatic brain injury. Common causes of penetrating head injury include firearms and motor vehicle crashes.
Closed Head Injuries
In a closed head injury, the injury is caused by blunt trauma to the head. Closed head injuries can range from mild to severe. There are several different types of closed head injuries, including:
A generally mild type of closed head injury, a concussion is caused by rapid back-and-forth movements of the brain within the skull, which affect the metabolism of brain cells and alter blood flow in the brain.
These changes impair the brain’s ability to function. Most people with a concussion will return to normal levels of function within a few days. However, if a person gets a second concussion before the first one has fully healed, they may experience a condition known as second impact syndrome. This involves rapid and severe swelling in the brain and can be fatal.
Diffuse axonal injury (DAI)
Diffuse axonal injury is more severe than a concussion. In this type of injury, the rapid movements of the brain within the skull cause tearing of axons, which are long cables that brain cells use to communicate with each other. This has a significant effect on the brain’s ability to function. Most people with DAI are in a coma following the injury.
A contusion is a bruise of the brain that may occur in the area directly under the area of impact on the skull. The force of the impact can also cause the brain to make an impact with the opposite side of the skull, causing a contusion on that side of the brain. The injury to the opposite side of the brain is known as a contrecoup injury.
In the area of a contusion, there is swelling and bleeding from small blood vessels, which can lead to further damage to brain tissue over the hours to days following the injury.
A hematoma is a collection of blood caused by damaged and leaking blood vessels. A hematoma can cause pressure to gradually build up within the skull, causing brain damage. In severe cases, the brainstem may be pressed against the base of the skull, which can be fatal.
In a hemorrhage, an artery becomes torn. Unlike a hematoma, which is a slower bleed involving mostly clotted blood, a hemorrhage involves a more rapid flow of fresh blood into the brain. This can cause a rapid rise of pressure within the skull and exposes brain cells directly to blood, which is toxic to them.
Closed head injuries can be caused by falls, motor vehicle crashes, sports-related events, accidents and assaults. In babies and young children, being violently shaken can also cause a closed head injury.
Severity Of TBI
Another way to classify traumatic brain injury is by the severity of the injury. Doctors use the Glasgow Coma Scale (GCS) to evaluate a patient’s overall level of brain function. This test evaluates a patient’s eye responses, verbal responses and motor responses. Scores in each category range from 1 to 6. The scores are added to give a total GCS score between 3 and 15.
Using the GCS, doctors can classify TBI as mild, moderate or severe.
People with mild TBI have a GCS score of 14 or 15, meaning that they’re only minimally impaired. They may not lose consciousness at all or may be unconscious for less than 30 minutes. This type of TBI accounts for more than 80 percent of cases of TBI.
People with moderate TBI have a GBS score of 9 to 13. They are often confused or incoherent, may open their eyes only in response to a strong stimulus, and may or may not be able to obey a simple motor command. Those with moderate TBI generally experience a loss of consciousness that lasts more than 30 minutes but less than 24 hours. However, the alteration of mental state lasts for more than 24 hours. This type of traumatic brain injury accounts for about 10 percent of cases.
People with severe TBI have a GCS of 3 to 8, corresponding to severe impairment of consciousness. In general, a patient with a score of 7 or less is considered to be in a coma, and a patient with a score of 8 is nearly comatose. People with severe TBI lose consciousness for more than 24 hours.
Timing Of Brain Injury
When an injury to the head occurs, damage can occur to the brain both immediately and in the period following the injury. The initial injury is known as the primary brain injury, while secondary brain injury occurs over the hours to days following the injury, due to the brain’s response to damage.
Primary Brain Injury
The primary injury results from the direct mechanical trauma caused by the event. In general, any damage caused by the primary injury is irreversible. Because the damage from the primary injury occurs immediately, medical treatment cannot do anything to change it.
Secondary Brain Injury
Secondary brain injury results from the brain’s response to damage. It evolves over the hours to days following the initial injury. Although the exact mechanisms of secondary brain injury are still being studied, it’s known that both swelling and the release of toxic substances are involved.
Swelling occurs due to inflammation. When any part of the body is injured, this creates an inflammatory reaction. Blood flow to the area increases in order to bring cells and nutrients to repair the damage. This increase in blood flow causes swelling.
In most parts of the body, swelling doesn’t cause significant damage. However, the brain is different because it’s encased within the rigid cavity of the skull. When brain tissue swells even slightly, the pressure goes up inside of the skull. This pressure causes additional brain damage. If there’s bleeding inside the skull — a hematoma or hemorrhage — blood can also build up, causing an additional rise in pressure.
In addition, damaged brain cells release certain substances, including neurotransmitters and inflammatory chemicals, that are toxic to other brain cells. In fact, blood itself (outside of a blood vessel) is actually toxic to cells in the brain. As a result of a severe injury, various biochemical changes occur in brain cells that can affect their function and even cause them to die. Substances released as a result of the injury can also affect blood flow within the brain, depriving brain cells of oxygen and killing them.
Together, these processes lead to continuing brain damage after an injury. Secondary injury explains why many TBI patients worsen in the days following an injury and why many deaths from TBI don’t occur immediately. However, medical treatment can potentially lessen the severity of secondary brain injury. Treatments for TBI are often aimed at reducing secondary brain injury in order to preserve as much brain tissue as possible.
The highly skilled and profoundly compassionate attorneys at Marasco & Nesselbush have partnered with medical professionals, brain injury rehabilitation providers, and other advocates at the Brain Injury Association of Rhode Island to provide legal and medical resources to brain injury survivors and their families.
Contact us today at one of our Rhode Island offices to learn how we have helped others like you rebuild their lives in the aftermath of a traumatic brain injury. The consultation is free.
Recovered for a client who sustained a traumatic brain injury in a car crash.
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