Cognitive reserve theories have been postulated in an attempt to explain individual differences in functional outcome following cerebral insult or disease. These theories suggest that higher education and psychometric intelligence may preserve functional capacity regardless of injury or disease severity. This study investigated cognitive reserve in 25 participants with traumatic brain injury (TBI) using high-resolution magnetic resonance imaging (MRI) analyses. We examined the relationships between total intracranial volume (TICV), ventricle-tobrain ratio (VBR), education level, and standardized testing obtained prior to injury with post-injury cognitive outcome. Participants with lower post-injury IQ scores had significantly lower TICV values, irrespective of injury severity, and experienced significantly greater change in IQ from pre- to post-injury. TICV and education correctly predicted participants' post-injury IQ category ( Y 90 or < 90). However, premorbid standardized testing (PST) scores did not predict cognitive outcome. The results of this study suggest that larger premorbid brain volume and higher education level may decrease vulnerability to cognitive deficits following TBI, consistent with the notion of a cognitive reserve.

This study examined the relative effectiveness of magnetic resonance (MR) imaging, single photon emission tomography (SPECT) and quantitative magnetic resonance (QMR) imaging in detecting brain abnormalities in 52 traumatically brain injured patients. The relationship between brain abnormalities and neuropsychological and psychological testing results was also investigated. Sixty-two per cent of patients had abnormal clinical MR findings, 57% had abnormal SPECT and 51% had abnormal QMR. Each neuroimaging modality detected brain abnormalities that the other two did not. Neuropsychological and psychological testing indicated significant memory impairments and subjective emotional distress even several years post-injury. Memory and intellectual impairments modestly but significantly correlated with the number of brain abnormalities indicated by all three imaging studies combined, as well as those detected individually by QMR and MR. SPECT abnormalities alone were not correlated with intellectual and memory outcome. Psychological distress was also related to the number of MR abnormalities, with most brain abnormalities being in the frontal areas.

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