Since the first systematic study of the significance of post-traumatic amnesia (PTA) in closed head injury, by Russell (1932), the findings of other studies have been consistent and in general agreement. A recent review (Smith, 1961) of investigations of the diagnostic and prognostic significance of duration of disturbed consciousness following closed head injury showed that all studies which had employed a definitive scale with absolute intervals had reported positive correlations between the length of PTA and the incidence of neurological signs and symptoms. In addition to providing confirmation of Russell's original findings, the range of clinical features whose incidence showed positive correlations has been extended considerably.
The purpose of the present paper is four-fold:
1. To define limitations and sources of ambiguity in the use of PTA as an index of severity of brain damage.
2. To present a preliminary report of significant representative findings in a study of 1,766