Post-traumatic amnesia
[4] 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.
[8] 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.
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.
[12] 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.
The most common research strategy to clarify these mechanisms is the examination of the impaired functional capabilities of people with post-traumatic amnesia (PTA) after a traumatic brain injury.
[16] Individuals who have been subjected to repeated sexual abuse during childhood or who have experienced combat show significant impairment and atrophy of the hippocampal region of the brain.
[18] Diaschisis was originally believed to be a result of disruption to neural tissue, but more recent evidence implicates increased activity levels of choline acetyltransferase, the enzyme responsible for the production of acetylcholine, as a major cause.
[11] This encouraging finding points to the positive long term prognosis of PTA; most patients return to normal levels of functioning.
The duration of an episode of PTA was correlated with reduced bloodflow to the right hemisphere, a finding which was consistent with functional MRI studies that link working memory with right frontal activity.
[11] The prefrontal cortex, which plays an important role in explicit memory retrieval, was also found to have decreased neural activation in patients scanned during the episode of PTA.
[11] Memory and new learning involve the cerebral cortex, the subcortical projections, the hippocampus, the diencephalon and the thalamus, areas that often experience damage as a result of TBI.
Frontal lobe lesions may also play a role in PTA, as damage to these areas is associated with changes in behavior, including irritability, aggressiveness, disinhibition, and a loss of judgment.
For example, in the case report of a patient referred to as "JL", Demery et al. noted that his memory impairments were so severe following his injury that he had forgotten that he had attended a Major League Baseball game less than 30 minutes after returning to the center where he was being treated.
[29] An alternative to the GOAT is the Westmead Post-Traumatic Amnesia Scale (WPTAS)[30][31] which examines not only orientation to person, place and time, but also crucially the ability to consistently remember new information from one day to the next.
The retrospective method, however, fails to account for the apparent lucidity of patients who are still experiencing substantial disorientation, or the finding that the recovery from post-traumatic amnesia is often characterized by the presence of "islands of memory" (short periods of clarity).
[34] While the GOAT is a useful tool, these results suggest that using alternative methods of assessing PTA may increase the amount of information available to physicians and may help in predicting rehabilitative success.
[10] Early research pointed to vasopressin as a potential treatment for improving the memory of patients living with post-traumatic amnesia (PTA).
However, Eames et al. (1999) found statistically significant improvements on several tests of memory with the use of a vasopressin nasal spray, with no reported ill effects.
[39] Although the degree of improvement was mild, and it could be attributed to numerous other factors of the rehabilitative program, the lack of any ill effects suggests that vasopressin is, at the least, a possible enhancement for a treatment regimen.
Researchers developed a "reality orientation", which involved discussing general facts (e.g. date, time, names of family members, etc.)
[42] A comprehensive analysis of literature based on the effects of early rehabilitation of traumatic brain injury concluded that there is no strong evidence linking any one particular practice of post-injury care to a reduced severity in symptoms.
However, even in the absence of a concrete correlation between a specific rehabilitation program and improved outcomes, the evidence and research available can provide many good suggestions for how to proceed with treatment.
[46] Although there was a general lack of knowledge about its mechanisms, a review of patients seen during WWI combat reveals the symptoms of post-traumatic amnesia (PTA) in many soldiers.
These soldiers commonly displayed dizziness, varying degrees of consciousness, a loss of non-traumatic personal information, and a lack of normal self-awareness lasting anywhere from hours to days.
[47] The following excerpt from a case report illustrates the loss of personal information observed in one patient: A soldier was assessed three days after having been admitted into a field ambulance.
[48]Researchers found that physicians had documented reports of combatants where "[b]oth central and peripheral details of the traumatic experience were lost.
[47] As a result, there was controversy over the possible causes of PTA in these non-concussed soldiers, with a separation between proponents of Freudian repression and those supporting a dissociative view of the condition.
The results supported these hypotheses, leading researchers to suggest that the impact of traumatic brain injury gets more severe as age progresses.
Typically, "repressed memory" is the term used to explain this sort of traumatic amnesia; the experience was so horrific that the adult cannot process what occurred years before.
A more viable explanation for this forgetting is childhood amnesia, a phenomenon describing the fact that most children do not have recall of events in their lives before the age of three, partially due to the lack of development of cognitive elements such as language.
