The Association Between Brain Reserve, Cognitive Reserve, and Neuropsychological and Functional Outcomes in Males With Chronic Moderate-to-Severe Traumatic Brain Injury

Purpose Moderate-to-severe traumatic brain injury (TBI) leads to significant neural and cognitive impairment, affecting functional outcome. This study investigated the chronic effects of moderate-to-severe TBI on brain reserve (BR), cognitive reserve (CR), and neuropsychological and functional outcome. Method The group with TBI consisted of 41 male participants with a primary diagnosis of moderate-to-severe closed head injury (time since injury [TSI], M = 6.12 years, range: 1–23, SD = 5.99, Mdn = 4). TBI survivors were compared to 24 neurotypical male participants, matched on age and education. Magnetic resonance imaging T1 anatomical images were used to calculate gray and white matter and cerebrospinal fluid volume. BR was calculated using the ventricle-to-brain ratio. CR was assessed using two hold measures: the Peabody Picture Vocabulary Test and the Pseudowords task. Functional outcome was measured using the Glasgow Outcome Scale–Extended. Results Neuropsychological performance of TBI survivors was significantly lower than their neurotypical controls, as measured by theoretically driven composites of verbal and visual memory, executive functions, attention, and CR. They presented greater ventricle-to-brain ratio volume, compared to noninjured controls, with higher scores indicating lower BR levels. Both BR and TSI were significantly associated with CR. Also, a median-split analysis revealed a TSI effect on CR. Significant associations were evident between the Glasgow Outcome Scale–Extended and the BR and CR measures. Conclusions Lingering neuropsychological deficits in chronic TBI support the role of BR and CR in functional outcome. Furthermore, TSI interferes with CR supporting the notion that TBI sets off a chronic neurodegenerative and progressive course that interferes with semantic knowledge. Supplemental Material https://doi.org/10.23641/asha.14049923