Cognition in multiple sclerosis: Between cognitive reserve and brain volume.

Background: Several correlations between cognitive impairment (CI), radiologic markers and cognitive reserve (CR) have been documented in MS.

Obiective: To evaluate correlation between CI and brain volume (BV) considering CR as possibile mitigating factor.

Methods: 195 relapsing MS patients underwent a neuropsychological assessment using BICAMS. BV was estimated using SIENAX to obtain normalized volume of brain (NBV), white matter (NWV), gray matter (NGV) and cortical gray matter (CGV). CR was estimated using a previously validated tool.

Results: Pearson test showed a correlation between the symbol digit modality test (SDMT) score and NBV (r=0.38; p<0.000) NGV(r=0.31; p<0.000), CGV (r=0.35; p<0.000) and CRI score(r=0.42; p<0.000). Linear regression (dependent variable:SDMT) showed a relationship with CR scores (p=0.000) and NGV(p<0.000). A difference was detected between cognitive impaired and preserved patients regarding mean of NBV(p=0.002), NGV(p=0.007), CGV(p=0.002) and CR Scores (p=0.007). Anova showed a association between the presence of CI (dependent variable) and the interaction term CRIQ × CGV (p=0.004) whit adjustment for age and disability evaluated by EDSS.

Conclusions: Our study shows a correlation between cognition and BV, in particular gray matter volume. Cognitive reserve is also confirmed as an important element playing a role in the complex interaction to determine the cognitive functions in MS.