Long-term effects of severe closed head injury on memory: evidence from a consecutive series of young adults.

Long-term cognitive sequelae of severe closed head injury were studied in a consecutive series of 39 young head-injury adults without gross intellectual deficits. Testing was carried out 2-5 years post-injury. Patients with a post-traumatic amnesia (PTA) greater than 3 weeks were impaired on a wide range of tests, particularly those requiring long-term retention of complex materials or where time constraints were a salient feature. Patients with a PTA of 1-3 weeks were unimpaired on all tasks. The results suggest that in young adults a threshold of brain damage related to long-term cognitive impairment operates at around a 2-3 week PTA duration.