Not All Brain Injuries Are The Same
There are many names and definitions for the different types of brain injuries. Several of them have overlapping meanings. Below is a list of 15 commonly used terms followed by more detailed definitions:
Acquired brain injury (ABI) is an injury to the brain acquired after birth that is not hereditary, congenital or degenerative. Examples of ABI’s are traumatic brain injury (TBI), dementia and Alzheimer’s.
Traumatic brain injury (TBI) results from a blow to the head. Injuries of this sort are categorized as severe, moderate or mild, depending on symptoms displayed shortly after the incident. The existing categorization system does not, however, describe prognosis or the underlying injury causing the symptoms.
Mild TBI is often referred to as a concussion and generally involves a brief change in mental status. It may, but does not have to, involve a loss of consciousness for a few seconds or minutes. It is estimated that up to 80 percent of head injuries fall into this category. Conventional imaging techniques such as X-rays, MRIs and CT scans are often unable to show structural injuries to the brain for mild TBI. However, new tests and imaging techniques such as diffusion tensor imaging (DTI) and biomarkers, which can help show an injury to the brain, are being developed.
Moderate TBI is often defined as a loss of consciousness for between 20 minutes and 6 hours. The injured person may display some brain swelling or bleeding, causing sleepiness, but is still able to be aroused. They may display similar symptoms as someone with mild TBI, but can have a worsening headache, vomiting, nausea, seizures or dilation of one or both pupils. Some health care professionals state that moderate TBI may include a period of post traumatic amnesia of up to 24 hours. Patients with a moderate TBI often suffer from a number of longer-term symptoms.
Severe TBI involves a more extended period of unconsciousness or amnesia after the injury. It is sometimes defined as 6 hours or more of unconsciousness or 24 hours or more of post traumatic amnesia. The patient is likely to be hospitalized and receive rehabilitation once the acute phase has passed. These patients tend to have more serious long-term symptoms.
Concussion occurs when a force impacts the head and alters brain function. The immediate effects typically involve memory and orientation disturbance. Concussion does not always involve a loss of consciousness — loss of consciousness occurs in only about 20 percent of all head injury cases. Concussion is the most commonly diagnosed type of TBI.
Repetitive concussion syndrome most often affects those who experience repetitive head impacts, a group including athletes and military personnel. Based on studies of boxers, this condition was previously referred to as dementia pugilistica. It can also lead to chronic encephalopathy (CTE). Repetitive concussion syndrome may cause long-term neurological and functional problems.
Second-impact syndrome typically occurs when someone, most often an athlete, suffers a concussion and returns to play within a short period of time before all symptoms have resolved (usually within days or several weeks) and suffers a second concussion. It may result in rapid and dangerous brain swelling and is different from repetitive concussion syndrome.
Coup contrecoup (Acceleration-deceleration injury) occurs when an impact or violent motion brings the head to a sudden stop, causing the brain to strike the skull while “bouncing” back and forth within it.
Closed head injury describes an injury in which the skull (and brain tissue) has not been penetrated. An example of a closed head injury is a coup contrecoup injury (see above). This type of injury may still result in contusions, swelling, bleeding and/or diffuse axonal injury (see below).
Open head injury means the skull and other protected layers have been penetrated and are exposed to the air. A classic example is a gunshot wound.
Diffuse axonal injury (DAI) is an injury caused by a force that sheared or tore the nerve tissue. It may also be referred to as traumatic axonal injury (TAI). This type of injury interferes with a nerve cell’s ability to send signals to other nerve cells.
Coma occurs when a person is unconscious, unaware of anything and unable to respond to any stimulus. Coma results from widespread damage to all parts of the brain.
Minimally conscious state occurs when there is a condition of severe altered consciousness, but one that includes some evidence of self-awareness or awareness of one’s environment. It is often a transitional state from a coma or vegetative condition to greater recovery.
Locked-in syndrome occurs when a person is aware of his or her surroundings and is awake, but he or she isn’t able to speak or move. The person may be able to communicate with eye movement or blinking. This state results from damage limited to the lower brain and brainstem. This rarely occurs after trauma.