Post-traumatic amnesia (PTA) 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 their name, where they are, 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 "post-traumatic 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). PTA may refer to only anterograde forms, or to both retrograde and anterograde forms. 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. Individuals with retrograde amnesia may partially regain memory later, but memories are not regained with anterograde amnesia because they were not encoded properly. The term "post-traumatic amnesia" was first used in 1940 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.
Symptoms
The most prominent symptom of post-traumatic amnesia (PTA) is a loss of memory of the present time. As a result, patients are often unaware of their condition and may behave as if they are going about their regular lives. This can cause complications if patients are confined to a hospital and may lead to agitation, distress and anxiety. Many patients report feeling as though they were being "held prisoner" and being prevented from carrying on with their daily lives. Other symptoms include agitation, confusion, disorientation, and restlessness. Patients also often display behavioral disturbances. Patients may shout, swear and behave in a disinhibited fashion. There have been cases in which patients who do not recognize anyone will ask for family members or acquaintances that they have not seen in years. Some patients exhibit childlike behavior. Other patients show uncharacteristically quiet, friendly and loving behavior. Although this behavior may seem less threatening because of its lack of aggressiveness, it may be equally worrisome. PTA patients are often unaware of their surroundings and will ask questions repeatedly. Patients may also have a tendency to wander off, which can be a major concern in those who have sustained additional injuries at the time of trauma, such as injured limbs, as it may lead to the worsening of these secondary injuries.
Attention Attention is a cognitive resource that contributes to many mental functions. The ability to engage attention requires a certain level of conscious awareness, arousal and concentration, all mechanisms that are generally impaired by traumatic brain injury. The involvement of attention in such a vast array of cognitive processes has led to the suggestion that attentional deficit may act as an underlying factor in the range of cognitive deficits observed in patients experiencing post-traumatic amnesia (PTA). Attention has been regarded as an important factor in the healthy functioning of encoding, verbal comprehension and new learning. Automatic attention processes (such as counting forwards) are recovered before simple memory skills (such as a recognition test of verbal material) in individuals with mild to moderate brain injury. This implies that the recovery of attentional ability precedes the progression of memory recovery after injury, helping to pave the way to regain ability for new learning. In terms of more severe brain injuries, this automatic attention task performance recovers before disorientation completely resolves. One of the weaknesses of the method most often used in assessing PTA, the Galveston Orientation and Amnesia Test (GOAT), is that it does not include any assessment of attention, which could help give a better indication of potential for recovery. By omitting attention, the test is omitting some crucial aspects of a person's cognitive capabilities. In addition, assessing attention during the period of PTA may help determine whether the patient is still in a state of PTA or if they are experiencing a more permanent form of memory deficit. In patients with mild TBI, the damage consists primarily of diffuse axonal injury (widespread damage to white matter) without any focal damage (damage to specific areas). Sometimes, injury of the brainstem was also observed. In these cases, there is likely the presence of an attentional deficit without a true amnesiac state. In more severely brain-damaged individuals, the damage to the temporal lobes and the frontal lobes serves as good indication that amnesia will result. Patients with more chronic forms of memory impairment showed poor performance when tested with PTA scales, making differentiation between the two types of memory impairment very difficult. PTA patients exhibit poor simple reaction time, reduced information processing speed and reduced verbal fluency, which are all attentional deficits that could be used to distinguish these patients from those with more severe and permanent memory problems.
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