post-traumatic amnesia

n. Inability to store new information and/or retrieve previous information as a result of traumatic head injury. Head injury can be associated with coma, and post-traumatic amnesia becomes evident only when the patient can respond. Post-traumatic amnesia is associated with a diversity of cognitive impairments, including attention, perception, problem solving, and memory. After the head injury and once the patient can respond to questions, usually it is evident that he/she has not only significant anterograde amnesia (defect in acquiring new memories) but also retrograde amnesia (loss of previously acquired memories). As the patient improves, the duration of the retrograde amnesia shrinks to within a few hours, minutes, or seconds before the brain injury, and the anterograde amnesia also improves, as the patient becomes progressively capable of retaining some information. The duration of the post-traumatic amnesia has been used as a criterion of the head injury severity and in monitoring the course of traumatic brain injury. Mild head injury is associated with a post-traumatic amnesia shorter than 1 hour. Moderate traumatic brain injury includes a post-traumatic amnesia of 1 hour to 24 hours. Severe traumatic brain injury is associated with amnesia for more than 24 hours. – AA