image by John (lic)When the term traumatic brain injury (TBI) or similar terms like acquired brain injury, head injury, etc. are used they refer to an injury to the brain that has occurred because of some type of mechanical force being applied to the person. A person does not actually have to be hit in the head to receive a TBI. TBI's can result from acceleration/deceleration incidents (going very fast and then suddenly stopping or changing direction) in addition to being struck in the body or head. There have been many different grading systems for TBI based on different types of diagnostic measures or standards. Most often TBI's are rated as being either mild, moderate, or severe based on certain symptoms that people show. Obviously more serious issues occur with people who are in the moderate to severe range.
The majority of TBI's are closed head injuries meaning that the person's skull has not been pierced (although there may be scrapes, abrasions, bruises, etc. on the skull). An open head injury is typically defined as being an injury where the skull has been pierced and the brain has been exposed. The brain itself may or may not be penetrated in these cases.
Closed head injuries occur because of car accidents, being struck in the head, falls, etc. Most open head injuries occur because of objects penetrating the skull such as bullets, knives, pieces of metal of wood, etc. However, it is certainly possible to be hit in the head with a very heavy object such as a crowbar and have a penetrating head injury that would meet the criteria for a traumatic brain injury and that also qualifies as an open head injury.
Traumatic brain injuries are often very complicated. There are several different issues to consider. Just a few of these include:
Coup Injuries to the Brain: This refers to brain damage that occurs at the location where the skull has been struck.
Countercoup Injuries to the Brain: This refers to injuries that occur on the opposite side of the brain where the skull was struck. The brain can move slightly in the skull and hit the opposite end of the skull to where the skull was struck. The inner surface of the skull often has bony ridges that produce abrasions to the brain when the brain rubs against it. A person can have both coup injuries and countercoup injuries because of a TBI.
Diffuse Axonal Injury: The axons are the signaling part of the neuron (the nerve cells in the brain that are responsible for cognition). Injury to axons may extend beyond the actual area where the brain was struck or a countercoup injury. When the brain is rotated or twisted, the nerves in the brain are twisted. This can result in damage to neurons in the brain in areas of the brain that do not experience direct contact with the skull or another object. When this damage is extensive throughout the brain it is defined as diffuse axonal injury. Diffuse axonal injury often results in numerous cognitive issues.
Concussion: The term concussion is often used in many different situations. The term originally meant the experience of cognitive problems that did not last very long and happened because of a blow to the head or some other collision that may not directly involve the head being struck. There have been various rating systems designed to determine the severity of concussions. By current standards, concussions can range from mild to severe. People can may experience a loss of consciousness that can occur for 30 seconds or less to several or more minutes. These are often graded as being mild to moderate concussions depending on the system being used to longer losses of consciousness (more severe concussions) depending on the rating scale. Just experiencing one or two minor concussions over the course of a lifetime is not generally considered to be particularly dangerous and occurs to most people. Most everyone gets hit in the head or bumps their head and is shaken slightly at least once or twice in their lifetime. However, experiencing numerous mild concussions or experiencing one or more moderate to severe concussions can lead to significant issues.
Chronic Traumatic Encephalopathy (CTE): Many of the effects of TBI are not considered to be progressive (get worse over time). However, in a CTE, there is a progressive damage to the brain that occurs in people who have had many different traumatic events affecting the brain. This may be having multiple concussions that may have been very minor when they occurred but over time the effects of these traumatic events lead to significant brain damage. CTE has been a significant focus in football players recently, because these individuals receive numerous concussive-like events in both practice and during actual games. There been many high-profile cases of individuals that have developed severe issues such as amnesia, depression, and even suicidal behaviors following extensive participation in contact sports like football.
One of the clinical tools used to identify the severity of a TBI is known as the Glasgow Coma Scale. This scale is divided into three sections: eye-opening, verbal responses, and motor responses (physical or bodily responses). The maximum amount of points that can be assigned is 15. People with scores of 13 - 15 have mild TBI's, 9 to 12 have moderate TBI's, and those with a score of 8 or below have TBIs that are defined as being severe.
Another method to determine the severity of a TBI is measuring the length of post traumatic amnesia. Post traumatic amnesia is defined as the period following the TBI that it takes a person to become oriented and to be able to recall new memories (orientation refers to the ability to report the time, date, place, situation, etc. where a person is). In general, it is currently accepted that moderate to severe TBI's occur when the posttraumatic amnesia lasts for more than 24 hours. The longer the length of the person's posttraumatic amnesia the worse the prognosis for the person is.
The DSM-5 diagnostic criteria for neurocognitive disorder due to traumatic brain injury and some of the effects of brain injuries are discussed in the next section.