Measuring post-traumatic amnesia (PTA): an historical review.

The duration of post-traumatic amnesia (PTA), which is the period following brain injury when patients are disoriented and impaired in the acquisition of new information, has been used as a behavioural indicator of the severity of injury. This paper reviews earlier retrospective and more recently developed prospective methods of assessing the duration of PTA. Prospective assessment that commences before the resolution of PTA overcomes the possible over- or underestimation of the duration of PTA inherent in methods that assess PTA retrospectively by clinical interview.