Information-processing speed in mildly disabled relapsing-remitting multiple sclerosis patients correlates with volumetry of optic chiasma and subcortical grey matter nuclei.

Introduction: Multiple sclerosis (MS) is an inflammatory demyelinating disease leading not only to physical disability but also to cognitive dysfunction. The aim of our study was to test cognitive functions of MS patients with mild relapsing-remitting form and to find out the relationship between cognitive functions and brain volumetry.

Methods: 52 patients (RRMSp) and 23 age-related healthy participants (CON) were enrolled. Mild disability was defined by mean EDSS 2.4 (≤ 4.0), and by median of disease duration 5.2 years. Cognitive status was tested using Single Digit Modality Test (SDMT). Brain volumetry was processed in FreeSurfer 2.0.0.

Results: RRMSp patients showed significantly lower SDMT score than CON. SDMT results correlated positively with volume of thalamus, putamen and nc. caudate, and negatively with optic chiasma volume. Compared with CON, RRMSp presented with significantly lower volume in left and right nc. accumbent, cuneus and insular GM, right putamen, total brain cortical grey matter (GM), white matters hypointensities, and 3rd ventricular widths.

Conclusion: To our best knowledge, this is the first study that presents results showing a correlation of lower SDMT with higher optic chiasma volume, due to its subclinical chronic demyelination. We confirmed that GM atrophy is involved in cognitive functions in MS (Tab. 3, Fig. 2, Ref. 73).