Cognitive performance in multiple sclerosis: the contribution of intellectual enrichment and brain MRI measures

Cognitive reserve (CR) is a construct that originates from the observation of poor correspondence between brain damage and clinical symptoms. The aim of the study was to investigate the association between cognitive reserve (CR), brain reserve (BR) and cognitive functions and to evaluate whether CR might attenuate/moderate the negative impact of brain atrophy and lesion load on cognitive functions in multiple sclerosis (MS). To achieve these aims, ninety-eight relapsing-remitting MS patients underwent the brief repeatable battery of neuropsychological tests and Stroop test (ST). CR was assessed by vocabulary-based estimate of lifetime intellectual enrichment. All patients underwent a 3T MRI to assess T2-lesion load and atrophy measures, including normalized gray matter and white matter (nWMV) volumes. The BR was evaluated by maximal lifetime brain volume expressed by intracranial volume (ICV). Hierarchical regressions were used to investigate whether higher BR and/or CR is related to better cognitive performances after controlling for potentially confounding factors. The ICV was not associated with any cognitive tests. Intellectual enrichment was positively associated with performance on tests assessing memory, attention and information processing speed, verbal fluency and inhibitory control. Significant relationship between nWMV and ST was moderated by intellectual enrichment. In conclusion, the findings suggested that CR seems to mitigate cognitive dysfunction in MS patients and can reduce the negative impact of brain atrophy on inhibitory control, relevant for integrity of instrumental activities of daily living.