Definition and Classification of TBI
Approximately 1.5 million Americans, representing some 1.2 million emergency room visits and 50,000 deaths, suffer traumatic brain injuries (TBI) each year (http://www.cdc.gov/traumaticbraininjury/tbi_report_to_congress.html). TBI—or intracranial injury—is defined as damage to the brain caused by external or traumatic force, such as a blow to the head, rapid acceleration/deceleration, violent shaking, explosive blast waves or penetration by a projectile (e.g., knife, bullet, shrapnel, etc.). TBI is not necessarily the same as a head injury. A head injury can encompass numerous types of trauma to the skull or face while not affecting the brain; nonetheless, the terms, TBI and head injury, are often used interchangeably to describe brain damage.
TBI is typically classified using three criteria:
- Degree of severity: mild, moderate or severe.
- Anatomical or pathological features.
- Mechanism of injury or causative force.
Extent of Severity
The Glasgow Coma Scale (GCS) is most commonly used to determine and classify TBI severity. The GCS is a five point neurologically-based scale, comprised of three tests—eye, verbal and motor responses—and as such, is graded on a scale of 15 (five points x three tests). A sixth point is assigned for motor function. The table below depicts these gradients.
Glasgow Coma Scale
When assessing the severity of a patient’s TBI, results of all of these tests are summed to determine a composite score. Generally, the following GCS scores are used as determinants of severity:
- 13 or above is regarded as a mild TBI (MTBI);
- 9-12 is deemed a moderate injury, and
- 8 or below is considered severe.
For various reasons—discussed at greater length later on—the GCS has its limitations as a diagnostic tool. It is not an appropriate instrument for assessing young children or nonverbal patients, and it has only limited potential in terms of predicting an individual’s long-term prognosis.
Anatomical or Pathological Features
TBI is also classified by its anatomical or pathological features. Wounds can be:
- Extra-axial: Located within the skull but not penetrating the brain.
- Intra-axial: Occurring within the brain.
- Focal: Localized to one area of the brain.
- Diffuse: Distributed throughout the brain, affecting many parts.
It is possible—and actually is fairly common—for TBI patients to demonstrate both focal and diffuse injuries.
Extra-axial automatically rules out Option A because an intra-cranial hemorrhage means bleeding inside the brain. Likewise, Option C involves diffuse or widespread damage to the brain as opposed to a focal injury which is confined to one area.
Signs and symptoms of TBI can vary widely depending on the degree of injury and the area(s) of the brain affected. Sometimes symptoms can appear right away or they may take days or even weeks (occasionally months) to develop. Some people with a concussion or MTBI may lose consciousness; others won’t. They may appear dazed or disoriented, feel fatigued and/or complain of headaches. They may exhibit marked changes in behavior or mood.
The Centers for Disease Control and Prevention (CDC) has developed a simple checklist of signs and symptoms that may indicate concussion. It appears below, categorized by the major functional areas impacted by concussion:
Concussion (MTBI) Checklist of Symptoms
- Difficulty thinking clearly
- Feeling slowed down
- Difficulty concentrating
- Difficulty remembering new information
- Fuzzy or blurry vision
- Nausea or vomiting (during the earliest stage)
- Sensitivity to light and/or sound
- Balance problems
- Feeling fatigues/having no energy
- More emotional than “normal” pattern
- Sleeping more than normal
- Sleeping less than usual
- Trouble falling asleep
Accurate diagnosis of concussions can be tricky and fraught with frustration. Some people may act fine after having sustained a concussion even though they are behaving much differently than normal. Other people will sense something is definitely amiss but will not seek medical attention because there are no visible signs of an injury. Older adults, young children and those who have suffered recurrent concussions may exhibit persistent symptoms and take much longer to recover from MTBI or will develop chronic problems due to the anatomy and condition of their brain tissue.