WHAT IS A TRAUMATIC BRAIN INJURY?
- Of all types of injury, those to the brain are among the most likely to result in death or permanent disability.
- Brain injury is the leading cause of death and disability worldwide.
- Traumatic brain injury is the leading cause of seizure disorders.
- Annually in the United States one million Americans are treated and released from hospital emergency departments as a result of traumatic brain injury (TBI). 230,000 people are hospitalized due to TBIs and survive. 80,000 people are estimated to be discharged from the hospital with some TBI-related disability. 50,000 people die due to TBIs. An estimated 5.3 million Americans are living today with disability related to traumatic brain injury.
What Is a Traumatic Brain Injury?
Traumatic brain injury (TBI) refers to damage to the brain caused by an external physical force that affects the functioning of the brain. TBIs can be caused by a bump or blow to the head (closed head injury) or by a penetrating head injury during which an object penetrates the skull. Events that may result in a TBI include car accidents, a gunshot wound to the head, or a fall.
A TBI is not caused by something internal such as a stroke or tumor, and does not include damage to the brain due to prolonged lack of oxygen (anoxic brain injuries). It is possible for an individual to suffer a TBI without ever losing consciousness. TBIs may result in mild, temporary problems, but more severe injuries can lead to serious physical and psychological symptoms, coma, and even death.
The following link contains a video with a helpful explanation of TBIs: http://www.traumaticbraininjuryatoz.org/The-Brain/What-is-Traumatic-Brain-Injury
To understand what happens when the brain is injured, it is important to grasp what a healthy brain is made of and what it does.
The brain is enclosed inside the skull which acts as a protective covering. The brain is made of neurons (nerve cells) that form tracts that route throughout the brain. These nerve tracts deliver messages to various parts of the brain to perform functions. The functions include coordinating and regulating the body’s systems, such as breathing; heart rate; body temperature; metabolism; thought processing; body movements; personality; behavior; and the senses of vision, hearing, taste, smell, and touch.
Each part of the brain serves a specific function and links with other parts of the brain to form more complex functions. “Minor” or “mild” injuries to the brain often significantly impede the brain’s ability to function.
The brain is made up of six parts that can be injured in a head injury. The effect of a brain injury is partially determined by the location of the injury. In some instances only a single area of the brain is affected, but in most cases of TBI multiple areas have been injured. When all areas of the brain are affected, the injury and its consequences for the individual can be very severe. In order to better understand the severe effects of a TBI, a brief explanation of the structure of the brain and the functions of each area of the brain is helpful.
BRAIN STRUCTURE & FUNCTION
The brain stem is at the very base of the human brain and assists in a number of the body’s most important functions. The brain stem assists in breathing; heart rate; swallowing; reflexes for seeing and hearing; controlling sweating, blood pressure, digestion, temperature; regulating an individual’s level of alertness, ability to sleep, and sense of balance.
The cerebellum is located directly above the brain stem. The brain stem controls coordination of voluntary movement; balance and equilibrium; and memory for reflex motor acts.
The frontal lobes are responsible for behavioral output such as cognitive and social behaviors, as well as movement of the body. This brain region is often affected by traumatic brain injuries, especially injuries caused by acceleration-deceleration forces that are often associated with motor vehicle accidents. The frontal lobes are involved in several behaviors and functions of the human brain including: inhibition, spontaneity; initiating behaviors; self-regulation of behavior; abstract reasoning; attention and working memory; executive functioning (e.g., multitasking, organizing, etc.); and movement (including speech movements, facial expressions).
The temporal lobes are composed of the primary auditory cortex and areas of the brain involved in the comprehension and production of spoken language. Regions of the temporal lobes are also responsible for learning and memory. Injury to the temporal lobes is also common with TBI. The temporal lobes are associated with several behaviors and functions of the human brain including: auditory processing or the ability to focus on one sound among many; comprehension of spoken words; language production (such as fluency and word-finding); and verbal and visual memory.
The occipital lobes include the primary visual cortex and the visual association areas of the brain. Injury or lesions to the primary visual cortex lead to impairments such as blindness or blind spots. Damage to the visual association area can also cause other complications including visual distortions and visual inattention. The occipital lobes are associated with several behaviors and functions of the human brain including: visual recognition; visual attention; and spatial analysis.
The Parietal Lobes
The parietal lobes include the posterior association cortex and are responsible for complex behaviors, including all behavior involving the senses. The parietal lobes are involved in various other behaviors and functions of the human brain including: language comprehension; constructional ability; body positioning and movement; sensory perception (e.g., touch); sensory neglect/inattention; right-left differentiation; self-awareness/insight (e.g., regarding cognitive limitations); and the ability to perform arithmetic.
The following link provides an interactive diagram of the brain and each of its critical areas: http://www.brainline.org
CAUSES OF TBI
A traumatic brain injury (TBI) can occur when there is a force on the head that results in penetration of the skull (aka open-head injury), or when there is a force to the head that leaves the skull intact but results in injury to the brain tissue (aka closed-head injury). A traumatic brain injury may result from any external force to the head.
The following forces and/or events may result in TBIs:
- a blow to the head.
- acceleration-deceleration forces, wherein no direct impact is required (e.g., a restrained passenger coming to a sudden stop when a car strikes an object).
- Projectile missile (e.g., bullet).
- Concussive forces (e.g., blast waves from an explosion).
Falls are the leading cause of TBI, with the greatest risk for injury among individuals aged 0-4 years and aged 75+ years. Motor vehicle accidents (MVAs) are the greatest cause of TBI-related hospitalizations. TBIs due to MVAs are most prevalent in individuals aged 15-24 years. Any force or trauma to the head may result in TBIs which could result in direct injury or bruising (contusion) to surface brain tissue; trauma to the blood vessels of the brain causing bleeding (hematoma) which can damage the brain tissue it contacts, and can increase pressure in the brain; edema or swelling of brain tissue; shearing or twisting of axonal fibers (white matter tracts) in the brain (Typically associated with acceleration-deceleration injuries).
DIAGNOSING A TBI
INDICES OF SEVERITY OF INJURY
TBI’s are generally graded as mild, moderate, or severe. Mild TBIs include concussions; these generally do not show lesions on MRI or CT scans. TBIs are specified as “mild complicated” or moderate when imaging shows evidence of lesion(s). TBIs typically result in emergency situations and because consequences can worsen swiftly without treatment, doctors usually need to assess the individual rapidly.
A common factor used to assess the severity of a TBI is the duration of Loss of Consciousness (LOC) experienced by the person who suffered the TBI. Duration of loss of consciousness (coma) following head trauma has historically been used as an indicator of TBI severity. However, significant TBIs do not necessarily lead to LOC, and research suggests that duration of LOC may not always be closely correlated with outcome.
According to research, TBIs are classified as mild when a patient experiences a loss of consciousness for 20 minutes or less.
TBIs are classified as moderate when a patient experiences a loss of consciousness that lasts for 6 hours or less from the time they were admitted to a hospital.
TBIs are classified as severe when a patient experiences a loss of conscious that last for more than 6 hours from the time they were admitted to the hospital.
GLASGOW COMA SCALE: One technique often utilized in diagnosing and assessing a TBI is the Glasgow Coma Scale. The Glasgow Coma Scale is a 15-point test that helps a doctor or other emergency medical personnel assess the initial severity of a brain injury by checking a person’s ability to follow directions and move their eyes and limbs. The coherence of speech also provides important clues. Abilities are scored numerically. Higher scores mean milder injuries.
CT SCAN: The cranial tomography (CT) scan is uses a series of X-rays to create a detailed view of the brain. A CT scan can quickly visualize fractures and uncover evidence of bleeding in the brain (hemorrhage), blood clots (hematomas), bruised brain tissue (contusions) and brain tissue swelling. CT scans are not painful. People with moderate to severe TBI will have several CT scans while in the hospital to keep track of lesions (damaged areas in the brain).
MAGNETIC RESONANCE IMAGING (MRI): An MRI uses powerful radio waves and magnets to create a detailed view of the brain. This testing creates a picture of the brain based on magnetic properties of molecules in tissue. Most people with severe TBI will have an abnormality on a CT scan or MRI scan. These scans cannot detect all types of brain injuries, so it is possible to have a severe TBI and be in a coma even though the scan results are normal. Doctors don’t often use MRIs during emergency assessments of traumatic brain injuries because the procedure takes too long. This test may be used after the person’s condition has been stabilized.
INTRACRANIAL PRESSURE MONITOR: Tissue swelling from a traumatic brain injury can increase the pressure inside the skull and cause additional damage to the brain. Doctors may insert a probe through the skull to monitor this pressure.
Commonly accepted criteria established by the TBI Model Systems (TBIMS) to identify the presence and severity of TBI include damage to brain tissue caused by an external force and at least one of the following:
- A documented loss of consciousness
- The person cannot recall the actual traumatic event (amnesia)
- The person has a skull fracture, post-traumatic seizure, or an abnormal brain scan due to the trauma.