The Measurement of Retrograde Post-Traumatic Amnesia

Retrograde amnesia is the inability to recall events which occurred immediately before head trauma or other acute brain insult. It is one aspect of a larger entity — posttraumatic amnesia — seen in some head injuries, and represents a defect in the consolidation of memories. Previous studies of retrograde amnesia have produced conflicting findings regarding its characteristics. A study was undertaken to identify the characteristics of retrograde amnesia, its relationship to anterograde amnesia, and the problems of its measurement. Forty-eight patients with head injuries admitted to the Emergency Department of the Winnipeg General Hospital were interviewed to identify all subjects meeting certain criteria regarding age, education, and so on, and twenty-five met the criteria and were included in the sample. Each subject was interviewed at least twice until the retrograde amnesia had reached a stable minimum. The duration of retrograde and anterograde amnesia as well as immediate and short-term memory were assessed. It was found that the duration of retrograde amnesia was directly related to the duration of the anterograde amnesia and to the duration of hospitalization. Some problems involved in measurement are discussed.