Brain volumetry counterparts of cognitive impairment in patients with multiple sclerosis

Abstract

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.