Predicting severity of cognitive impairment after severe head injury

It is often assumed that age is an important variable in determining cognitive outcome following severe head injury. The present study was carried out to determine whether age at time of injury predicted severity of cognitive impairment. Our hypothesis was that the older the patient at time of head injury the worse should be the cognitive impairment. Cognitive impairment was assessed by scores on nine standardized tests. Scores were obtained from 144 consecutive referrals to a clinical psychologist; all subjects had sustained a severe head injury. Of these, 115 had suffered a closed head injury. Ages ranged from 13 to 65 years. Apart from Unusual Views and Verbal Fluency no significant correlations were found between age and test performance. Thus there was little evidence that age predicted performance on cognitive tests. A number of significant correlations were found between length of coma and cognitive performance. The findings would seem to confirm that cognitive outcome after severe head injury is predicted by length of coma (which reflects severity of brain damage) whilst age at time of injury does not appear to be a good predictor of outcome.