Impact of TBI
In the United States, there are 1.7 million traumatic brain injuries annually. That is eight times the prevalence of breast cancer. In the last few years, the landscape of TBI has changed in that TBI deaths have decreased over time. As our medical care has advanced in our ability to keep those with severe TBI alive, that leaves us is with a larger population of survivors of severe TBI with chronic lasting impairments. This focuses our need to address the long-term impact of survival with TBI.
The prevalence of challenging behaviors post-TBI is reported in different ranges in the literature. Anywhere from 35% to 70% of those with a TBI present with challenging behaviors. Most studies across the board are reporting that about 50% of those with TBI have challenging behaviors that tend to increase over time. In one particularly comprehensive study, researchers showed that there were challenging behaviors in 38% of patients with a TBI at less than one-year post-injury, but 67% of patients at five year's post-injury presented with challenging behaviors. It's interesting to note that increase over time, which we will discuss in more detail throughout this course (Sabaz et al., 2014).
There is a profound psychosocial impact of challenging behaviors. Above cognition, above memory impairment, and above physical deficits, challenging behaviors are reported to be one of the most difficult aspects of TBI to manage for those involved (Ylvisaker et al., 2005). After a person suffers a TBI resulting in behavioral deficits, they have increased care needs. These patients often can't be by themselves, and they need assistance in the community. As such, they are going to present an increased burden of care. Often, there is reduced family integration. If a person has deficits in their behavior, they are not going to be the same parent as before, or they are not going to be the same sibling or the same child. For example, if someone is aggressive, they are not going to be able to reintegrate back into their premorbid vocational or educational situation. They may experience reduced educational integration and may have to go into a different classroom.
Decreased community participation is one of the biggest psychosocial impacts of behavior, and is one of the main predictors of challenging behaviors. When TBI patients exhibit challenging behaviors, they experience difficulty being in the community. As a result, their support system restricts their participation in the community. As time passes, the challenging behaviors increase. The less a TBI survivor participates in their community, the worse their behavior becomes. As therapists, we need to be cognizant of the fact that our patients' participation in social and community aspects is critical. Because these behaviors have a significant impact, it's important to treat behaviors, not only for the benefit of the survivors but also for the benefit of caregivers.
Types of Brain Injury
Today, we're going to review the following types of brain injury:
- Closed Head Injury
- Direct Impact
- Acceleration-Deceleration
- Blast Injury
- Penetrating Injury
Closed head injury. Closed head injury can be caused by direct impact, where there is a force upon the head. This type of TBI can result when the head hits something (e.g., the windshield or the pavement) or when something hits the head (e.g., a baseball bat). A closed-head injury can also be caused by acceleration-deceleration, where there's no direct impact to the head, but the brain is injured due to its movement and rotational force within the skull (e.g., in a case of whiplash or shaken baby syndrome). In both of these types of closed head injury, you can have a coup injury, which is a contusion at the site of impact, such as when the head hits something. Even in an acceleration-deceleration injury, if the force is strong enough, it can result in a contusion or a lesion on the cortex. The coup injury is the initial point of impact. If there's enough force, then it will propel the brain in the opposite direction resulting in the contrecoup injury. A coup-contrecoup injury is damage to the cortex within the skull from a direct impact or acceleration-deceleration. Both direct impact and acceleration-deceleration injuries can result in diffuse axonal injury, which we will discuss in more detail shortly.
Blast injury. Blast injuries are predominantly seen in the military and are caused by being in close proximity to an explosion, which impacts brain tissue. I found two quotes from "Blast Injuries and the Brain" (2017) that succinctly describe blast injuries:
- A blast injury feels like being hit by a wave and then being pulled back into the ocean — all in intensely rapid succession (Jeffrey Barth, PhD).
- More scientifically, blast injuries result from the complex pressure wave generated by an explosion, an instantaneous rise in atmospheric pressure that is much higher than normal for humans to withstand. This is called a blast over-pressurization wave (CDC, Mass Casualties).
When a person experiences a blast injury, there are many levels of trauma/damage: primary, secondary, tertiary, quaternary and quinary, as well as psychological trauma. In a primary blast injury, the person will likely experience blast lung, a ruptured eardrum, abdominal hemorrhage and perforation, eye rupture, and non-impact, blast-induced mild TBI. There are also secondary injuries, such as damage caused by shrapnel and eye penetration. From the force of the primary blast, a person can be physically blown away, resulting in a tertiary brain injury, such as a closed or open brain injury from the force that pushes them out of the area. Quaternary injuries may include burns or even inhalation of toxic gases. A quinary injury may result if there is fallout (e.g., if there was a dirty bomb) or any other chemical or biological substances that can cause not only injury but also illnesses or diseases. Finally, of course, a person may experience PTSD.
Penetrating brain injury. With a penetrating injury, a foreign object penetrates through the skull and into the brain, resulting in an open wound to the head. A gunshot wound, a knife, even pieces of the skull (if there's enough force present) can cause a penetrating injury. This type of injury is marked by focal damage that occurs along the route the object has traveled in the brain. The injured person may sustain a fractured or a perforated skull, torn meninges, and damage to the brain tissue.
Physiological Damage
Along with these types of brain injuries, there is additional physiological damage that can occur in the brain. The additional damage may involve:
- Diffuse axonal injury
- Contusions, Hematomas or Hemorrhages
- Secondary Damage
- Edema
- Raised Intracranial Pressure
- Excitotoxic Reaction
Diffuse Axonal Injury
With a diffuse axonal injury, damage to the axon occurs by the shifting and rotation of the brain. Similar to acceleration-deceleration injuries, those axons are going to get twisted, torn and even broken. When you damage that axon, you are causing interference with the signals that are being transmitted. You're breaking those connections, which impacts our thinking, our movement, and our behavior. This causes widespread damage throughout the brain at the level of the gray and white matter boundary. In severe cases, sometimes imaging can reveal the diffuse axonal injury, but most of the time they do not appear on the standard images that you get in the hospital. However, just because you cannot see it doesn't mean that there is no significant damage.
Contusions, Hematomas and Hemorrhages
When we get a patient's medical records, we may have a tendency to immediately look and see if there has been any focal damage. First of all, are there any contusions? This is the coup-contrecoup damage that we talked about earlier. We want to determine if there any microhemorrhages or bruises on the cortex that may have been caused either by direct impact or from an acceleration-deceleration injury. Most commonly in TBI, focal damage and contusions occur on the frontal and temporal lobes, based on the nature of the injuries (e.g., falling and car accidents), as well as the internal structure of the skull. Hematomas involve bleeding between the skull and the brain. This can happen frequently within the layers of the dura mater and arachnoid mater. We frequently see subdural hematomas and epidural hematomas. Hemorrhaging can also occur. You can have a subarachnoid hemorrhage or intracranial hemorrhage as a result of traumatic brain injury.
Secondary Damage
Edema is a common secondary effect of traumatic brain injury. Edema is swelling; it's an inflammatory response. Serious swelling can disrupt blood flow, which decreases oxygen and glucose delivery to the cells causing further damage. With significant swelling, there can be an increase in intracranial pressure which results in further damage and must be monitored. Finally, you can get an excitotoxic reaction. This is also the metabolic damage after a brain injury. When neurons are damaged, they're releasing neurotransmitters and chemicals in reaction to the injury. Cells are further damaged by the excessive stimulation of neurotransmitters (e.g., glutamate).
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