Cognitive deficits in multiple sclerosis: correlations with T2 changes in normal appearing brain tissue

Although disease load in multiple sclerosis (MS) often is based on T2 lesion volumes, the changes in T2 of normal appearing brain tissue (NABT) are rarely considered. By means of magnetic resonance, (MR) we retrospectively investigated whether T2 changes in NABT explain part of the cognitive impairment seen in MS and constitute a supplement to traditional measurement of T2 lesion volume.

Fifty patients with clinically definite MS were included (38 women, 12 men). Patients were MR scanned, neuropsychologically tested, and evaluated clinically with the Kurtzke Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Impairment Scale (MSIS). Voxel-wise T2 estimates and total T2 lesion volume were tested for correlations with eight cognitive domains, a general cognitive dysfunction factor (CDF), and the two clinical scales.

We found distinct clusters of voxels with T2 estimates correlating with CDF, mental processing speed, complex motor speed, verbal fluency, and MSIS. A significant negative correlation was found between total lesion volume and CDF (r = -0.34, P = 0.02), verbal intelligence (r = -0.40, P = 0.005), mental processing speed (r = -0.34, P = 0.03), visual problem solving (r = -0.40, P = 0.01), and complex motor speed (r = -0.39, P = 0.01). No significant correlation was detected between total lesion load and the clinical measures EDSS and MSIS.

Our results suggest that even in the NABT MR detects changes likely to be associated with an underlying pathology and possibly contributes to the cognitive impairment in MS.