Post-traumatic amnesia
Encyclopedia
Post-traumatic amnesia is a state of confusion
that occurs immediately following a traumatic brain injury
(TBI) in which the injured person is disoriented
and unable to remember events that occur after the injury. The person may be unable to state his or her name, where he or she is, and what time it is. When continuous memory returns, PTA is considered to have resolved. While PTA lasts, new events cannot be stored in the memory. About a third of patients with mild head injury are reported to have "islands of memory", in which the patient can recall only some events. During PTA, the patient's consciousness is "clouded". Because PTA involves confusion in addition to the memory loss typical of amnesia, the term "posttraumatic confusional state" has been proposed as an alternative.
There are two types of amnesia
: retrograde amnesia
(loss of memories that were formed shortly before the injury) and anterograde amnesia
(problems with creating new memories after the injury has taken place). Both retrograde and anterograde forms may be referred to as PTA, or the term may be used to refer only to anterograde amnesia.
Frequently the last symptom to ameliorate after a loss of consciousness, anterograde amnesia may not develop until hours after the injury. A common example in sports concussion is the quarterback who was able to conduct the complicated mental tasks of leading a football team
after a concussion, but has no recollection the next day of the part of the game that took place after the injury. Retrograde amnesia sufferers may partially regain memory later, but memories are not regained with anterograde amnesia because they were not encoded
properly.
The term "posttraumatic amnesia" was first used in 1928 in a paper by Symonds to refer to the period between the injury and the return of full, continuous memory, including any time during which the patient was unconscious.
PTA has been proposed to be the best measure of head trauma severity, but it may not be a reliable indicator of outcome.
However, PTA duration may be linked to the likelihood that psychiatric and behavioral problems will occur as consequences of TBI.
Classification systems for determining the severity of TBI may use duration of PTA alone or with other factors such as Glasgow Coma Scale
(GCS) score and duration of loss of consciousness (LOC) to divide TBI into categories of mild, moderate, and severe. One common system using all three factors and one using PTA alone are shown in the tables at right. Duration of PTA usually correlates well with GCS and usually lasts about four times longer than unconsciousness.
PTA is considered a hallmark of concussion, and is used as a measure of predicting its severity, for example in concussion grading scales. It may be more reliable for determining severity of concussion than GCS because the latter may not be sensitive enough; concussion sufferers often quickly regain a GCS score of 15.
Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms from concussion. Increased duration of PTA is associated with a heightened risk for TBI complications
such as post-traumatic epilepsy
.
Mental confusion
Confusion of a pathological degree usually refers to loss of orientation sometimes accompanied by disordered consciousness and often memory Confusion (from Latin confusĭo, -ōnis, noun of action from confundere "to pour together", also "to confuse") of a pathological degree usually refers to loss...
that occurs immediately following a traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
(TBI) in which the injured person is disoriented
Orientation (mental)
Orientation is a function of the mind involving awareness of three dimensions: time, place and person. Problems with orientation lead to disorientation, and can be due to various conditions, from delirium to intoxication...
and unable to remember events that occur after the injury. The person may be unable to state his or her name, where he or she is, and what time it is. When continuous memory returns, PTA is considered to have resolved. While PTA lasts, new events cannot be stored in the memory. About a third of patients with mild head injury are reported to have "islands of memory", in which the patient can recall only some events. During PTA, the patient's consciousness is "clouded". Because PTA involves confusion in addition to the memory loss typical of amnesia, the term "posttraumatic confusional state" has been proposed as an alternative.
There are two types of amnesia
Amnesia
Amnesia is a condition in which one's memory is lost. The causes of amnesia have traditionally been divided into categories. Memory appears to be stored in several parts of the limbic system of the brain, and any condition that interferes with the function of this system can cause amnesia...
: retrograde amnesia
Retrograde amnesia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease....
(loss of memories that were formed shortly before the injury) and anterograde amnesia
Anterograde amnesia
Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
(problems with creating new memories after the injury has taken place). Both retrograde and anterograde forms may be referred to as PTA, or the term may be used to refer only to anterograde amnesia.
Frequently the last symptom to ameliorate after a loss of consciousness, anterograde amnesia may not develop until hours after the injury. A common example in sports concussion is the quarterback who was able to conduct the complicated mental tasks of leading a football team
Football team
A football team is the collective name given to a group of players selected together in the various team sports known as football.Such teams could be selected to play in an against an opposing team, to represent a football club, group, state or nation, an All-star team or even selected as a...
after a concussion, but has no recollection the next day of the part of the game that took place after the injury. Retrograde amnesia sufferers may partially regain memory later, but memories are not regained with anterograde amnesia because they were not encoded
Encoding (Memory)
Memory has the ability to encode, store and recall information. Memories give an organism the capability to learn and adapt from previous experiences as well as build relationships. Encoding allows the perceived item of use or interest to be converted into a construct that can be stored within the...
properly.
The term "posttraumatic amnesia" was first used in 1928 in a paper by Symonds to refer to the period between the injury and the return of full, continuous memory, including any time during which the patient was unconscious.
Measure of traumatic brain injury severity
|
||||||||||||||
|
PTA has been proposed to be the best measure of head trauma severity, but it may not be a reliable indicator of outcome.
However, PTA duration may be linked to the likelihood that psychiatric and behavioral problems will occur as consequences of TBI.
Classification systems for determining the severity of TBI may use duration of PTA alone or with other factors such as Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...
(GCS) score and duration of loss of consciousness (LOC) to divide TBI into categories of mild, moderate, and severe. One common system using all three factors and one using PTA alone are shown in the tables at right. Duration of PTA usually correlates well with GCS and usually lasts about four times longer than unconsciousness.
PTA is considered a hallmark of concussion, and is used as a measure of predicting its severity, for example in concussion grading scales. It may be more reliable for determining severity of concussion than GCS because the latter may not be sensitive enough; concussion sufferers often quickly regain a GCS score of 15.
Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms from concussion. Increased duration of PTA is associated with a heightened risk for TBI complications
Complications of traumatic brain injury
Traumatic brain injury can cause a variety of complications, health effects that are not TBI themselves but that result from it. The risk of complications increases with the severity of the trauma; however even mild traumatic brain injury can result in disabilities that interfere with social...
such as post-traumatic epilepsy
Post-traumatic epilepsy
Post-traumatic epilepsy is a form of epilepsy that results from brain damage caused by physical trauma to the brain . A person with PTE suffers repeated post-traumatic seizures more than a week after the initial injury...
.