Brain volumetry counterparts of cognitive impairment in patients with multiple sclerosis.

BACKGROUND

Cognitive impairment is frequent in multiple sclerosis (MS). Tissue-specific atrophy measures have been shown to correlate with cognitive performance in several studies. Voxel-based morphometry (VBM) aims to identify regional differences in the local composition of brain tissue and makes possible to correlate these findings with cognitive impairment patterns.

AIM

To investigate the associations between cognitive impairment in MS and tissue-specific atrophy and regional distribution of grey matter.

METHOD

15 patients with MS and cognitive impairment were included. Demographic (age and years of schooling) and clinical (Multiple Sclerosis Functional Composite-MSFC and subtests, Expanded Disability Status Scale-EDSS, disease duration) variables were recorded and neuropsychological assessments performed (Trail Making Test A and B-TMTA and B, Symbol Digit Modalities Test-SDMT, Digit Span Test-DST and Rey's Auditory Verbal Learning Test Delayed Recall-RAVLT-DR). Magnetic resonance (MR) 3D sequences (MPRAGE) were performed on all subjects and tissue-specific volumes (SIENAx and SPM2 software) and VBM grey matter probability maps (SPM2) were obtained.

RESULTS

Moderate correlations were obtained between tissue volumes obtained with SPM2 and SIENAx. Using SIENAx moderate correlations were obtained between normalised brain volume (NBV) and disease duration (rho=-0.575, p=0.025) and RAVLT-DR (rho=0.518, p=0.048). Using SPM2 moderate correlations were obtained between white matter and brain parenchymal fractions (WMF and BPF) and RAVLT-DR (rho=0.572 and 0.539, p=0.026 and 0.038), between grey matter fraction (GMF) and Z scores on the Paced Auditory Serial Addition Test (PASAT) (rho=0.570, p=0.026), and between BPF and disease duration (rho=-0.6, p=0.018). Significant correlations were observed only between regional grey matter probability maps and grey matter (and to a much lesser extent white matter) volumes from SPM2.

CONCLUSION

Quantitative tissue-specific atrophy measures may display better correlations with patients' variables than regional grey matter atrophy distribution obtained using VBM methodology. These results should be confirmed in larger samples.