Shiee et al. Revisiting brain atrophy and its relationship to disability in multiple sclerosis. PLoS One. 2012;7(5):e37049.
BACKGROUND: Brain atrophy (shrinkage) is a well-accepted imaging biomarker of multiple sclerosis (MS) that partially correlates with both physical disability and cognitive impairment.
METHODOLOGY/PRINCIPAL FINDINGS: Based on MRI scans of 60 MS cases and 37 healthy volunteers, we measured the volumes of white matter (WM) lesions, cortical gray matter (GM), cerebral WM, caudate nucleus, putamen, thalamus, ventricles, and brainstem using a validated and completely automated segmentation method. We correlated these volumes with the Expanded Disability Status Scale (EDSS), MS Severity Scale (MSSS), MS Functional Composite (MSFC), and quantitative measures of ankle strength and toe sensation. Normalized volumes of both cortical and subcortical GM structures were abnormally low in the MS group, whereas no abnormality was found in the volume of the cerebral WM. High physical disability was associated with low cerebral WM, thalamus, and brainstem volumes (partial correlation coefficients ∼0.3-0.4) but not with low cortical GM volume. Thalamus volumes were inversely (the smaller the volume the more lesions) correlated with lesion load (r = -0.36, p<0.005).
CONCLUSION:The GM is atrophic in MS. Although lower WM volume is associated with greater disability, as might be expected, WM volume was on average in the normal range. This paradoxical result might be explained by the presence of co-existing pathological processes, such as tissue damage and repair, that cause both atrophy and hypertrophy and that underlie the observed disability.
This study reports that in MS the grey matter is shrinking indicating nerve loss. In the white matter disability was correlated with white matter shrinkage, however the volume of the white matter was not that different from that found in healthy people. However the volume of the white matter can be artificially heightened by swelling and tissue scarring and so can mask the damage that is occurring. MS is affecting both grey and white matter.This study lends further credence that monitoring grey matter changes may be a better way to monitor progression.