Neuropsychological impairment following traumatic brain injury: a dose-response analysis

Dikmen, Machamer, Winn, and Temkin (1995) administered the Halstead-Reitan Battery (HRB) to a sample of TBI patients. Similar patients were obtained from the second author (JEM) for two main purposes. First, we wished to determine if there is a dose-response relationship between TBI severity and residual cognitive deficit. Second, are Dikmen et al. results generalizable to other TBI samples? Analyses of the Meyers sample replicated the analyses of Dikmen sample. A significant dose-response relationship between loss of consciousness (LOC) and cognitive impairment was found using effect sizes for the Dikmen sample, as well as using regression-based normative T scores for the Meyers sample. The two methods were highly correlated with one another. Using mean scores for the six LOC-severity groups and the two samples resulted in a correlation coefficient r=.97, p<.0001. Results are presented for clinicians to use when assessing individual patients.