Functional Outcome in TBI II: Verbal Memory and Information Processing Speed Mediators

Following traumatic brain injury (TBI), patients often report memory difficulties, as well as reduced information processing speed. However, it remains unclear the extent to which these deficits contribute to functional impairment. In the present study, we compared the relative contribution of verbal memory and information processing speed to functional impairment at 12-month post-injury, in 87 patients with moderate-to-severe TBI. Employing structural equation modeling, we found that information processing speed, but not verbal memory functions, significantly mediated the relationship between TBI severity and post-TBI adaptive functioning. These findings suggest that despite the pervasive memory complaints among patients with TBI, it is the impact of neurotrauma on frontal systems that appears to be primarily responsible for patients' difficulties in social and occupational functioning.

Functional Outcome in TBI I: Neuropsychological, Emotional, and Behavioral Mediators

Literature exists to suggest that the severity of traumatic brain injury (TBI) is positively associated with the severity of functional impairment. However, potential mediators of this relationship have not been studied systematically. In the present study, we evaluated a model hypothesized to explain the relationship between TBI severity and functional impairment in 87 patients with moderate-to-severe TBI, studied longitudinally. Using structural equation modeling, we found that only neuropsychological status (but not emotional or behavioral difficulties) consistently mediated the relationship between TBI severity and functional outcome at 12-months post-injury. These findings suggest that, of the factors examined here, neurocognitive compromise plays the most prominent role in mediating post-TBI adaptive functioning in moderate-to-severe TBI, which has important implications for post-injury interventions.