Brain atrophy as a marker of cognitive impairment in mildly disabling relapsing-remitting multiple sclerosis

Background and purpose: We have studied the relationship between neuropsychological impairment and magnetic resonance imaging (MRI) measures in mildly disabling relapsing-remitting multiple sclerosis (RRMS). Methods: We compared measures of lesion burden and atrophy in 52 patients with Expanded Disability Status Scale <= 3.0. Neuropsychological testing explored various cognitive domains: attention and processing speed (APS), verbal and visual memory (VerbM; VisM), visual/constructional processes (VC), executive functions and motor programming/coordination. Specific and global index scores were derived to classify patients as deteriorated or not deteriorated by comparing their performance with 51 matched normal control subjects. Brain MRI analysis included proton density (PD)-lesion volume and T1-hypointensity volume, measures of central atrophy, including the third ventricle width, and corpus callosum (CC). Results: Patients with either APS, MCP or Verbal Learning impairments had a higher ventricular atrophy than unimpaired. The atrophy of the CC was only associated to VisM dysfunction. Patients with VisM deficits had higher lesion load on PD images. After controlling for age and education a higher third ventricle width was the best predictor for global and specific cognitive impairment. Conclusions: Our results suggest that cognitive impairment in RR patients with mild disease is better explained by atrophic changes than by total lesion load.