Assessment of cortical degeneration in patients with Parkinson's disease by voxel-based morphometry, cortical folding, and cortical thickness

Abstract

Noninvasive brain imaging methods provide useful information on cerebral involution and degenerative processes. Here we assessed cortical degeneration in 20 nondemented patients with Parkinson's disease (PD) and 20 healthy controls using three quantitative neuroanatomical approaches: voxel-based morphometry (VBM), cortical folding (BrainVisa), and cortical thickness (FreeSurfer). We examined the relationship between global and regional gray matter (GM) volumes, sulcal indices, and thickness measures derived from the previous methods as well as their association with cognitive performance, age, severity of motor symptoms, and disease stage. VBM analyses showed GM volume reductions in the left temporal gyrus in patients compared with controls. Cortical folding measures revealed significant decreases in the left frontal and right collateral sulci in patients. Finally, analysis of cortical thickness showed widespread cortical thinning in right lateral occipital, parietal and left temporal, frontal, and premotor regions. We found that, in patients, all global anatomical measures correlated with age, while GM volume and cortical thickness significantly correlated with disease stage. In controls, a significant association was found between global GM volume and cortical folding with age. Overall these results suggest that the three different methods provide complementary and related information on neurodegenerative changes occurring in PD, however, surface-based measures of cortical folding and especially cortical thickness seem to be more sensitive than VBM to identify regional GM changes associated to PD.

Figure 1

Sulcal structures selected for measuring local cortical folding: the superior frontal sulcus, anterior sylvian fissure, inferior temporal sulcus, occipitotemporal sulcus, collateral fissure, and anterior cingulate sulcus. On the left: outer cortical surface of a PD patient. On the right: outer cortical surface of a control subject.

Figure 2

Group VBM differences. Results from the analysis of VBM8 showing gray matter volume reductions in PD patients compared with healthy elderly controls are displayed in the form of statistical maps superimposed on the surface of a standardized brain and on the sample's template created during Dartel normalization with peak intensity located at the global maxima.

Figure 3

Graphic presenting data distribution with average means and standard errors of local sulcal indices of PD patients and controls. (*) Indicates significant results after correction for multiple comparisons.

Figure 4

Group cortical thickness differences. Results from the analysis of cortical thickness showing cortical thinning in PD patients compared with healthy elderly controls are displayed at each vertex of the surface of a standardized brain (averaged over all subjects) in terms of t statistical maps.

Figure 5

Correlations between whole‐brain GM volume, global sulcal index and average cortical thickness plotted versus patient's age and disease stage as indexed by the Hoehn & Yahr scale. Correlations with Hoehn & Yahr stage have not been corrected for age and gender effects only for picture purposes; the corrected values can be found in the text. All correlations were statistically significant except the one between cortical folding and Hoehn & Yahr stage.