Objective: To determine the gray matter (GM) changes in different clinical stages of Parkinson’s disease (PD) using Voxel Based Morphometry (VBM).

Background: PD is a chronic neurodegenerative disorder, with gradual progression of disease pathology in the central nervous system. While different clinical stages of PD is typically assessed using Hoehn and Yahr (H&Y) scale, assessment of GM changes using VBM in different clinical stages of PD may be useful to determine the progression of disease as well correlate clinically.

Methods: Forty-five patients with idiopathic PD at different H&Y stages of PD (15 each in H&Y stages I, II and III) and 45 healthy controls (HC) were part of this study. T1-weighted images were acquired on a 3 Tesla MRI. Regional GM differences between groups were assessed using VBM8 toolbox. Data processing was performed with Statistical Parametric Mapping 8. One way ANOVA analysis was performed to determine differences between H&Y I, II, III and HC using age, gender and total intracranial volume as covariates.

Results: There were no significant differences in demographics and clinical characteristics between the groups except for duration of illness (H&Y I vs H&Y III: 2.7±1.9 vs 7.4±5.2, p<0.01) and UPDRS-III score (H&Y I vs H&Y III: 16.2±8.4 vs 24.5±8.3, p<0.02). There was a significant difference in GM volume (FWE corrected <0.05) between the 4 groups in one way ANOVA analysis with involvement of left parahippocampal gyrus (Brodmann Area (BA) 34). On post hoc analysis there was a significant increase in atrophy in parahippocampal gyrus with disease progression from H&Y I to H&Y III when compared to controls. Cluster sizes and peak T values also increased with the stages (H&Y I: 76mm3 and 5.3; H&Y II: 695 mm3 and 5.97; H&Y III: 887 mm3 and 6.33). There was no significant difference in GM volumes on post hoc analysis between the H&Y subgroups.

Conclusions: Our study demonstrates progressive GM atrophy of parahippocampal gyrus (part of BA 34) in PD patients with increase H&Y stages. BA 34, which is a part of olfactory cortex, is reported to be involved in PD causing anosmia and cognitive deficits. Our findings suggest that volume of parahippocampal gyrus may be useful structural correlate of H&Y clinical staging in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/progressive-atrophy-of-parahippocampal-gyrus-correlates-with-hoehn-yahr-stages-of-parkinsons-disease-a-voxel-based-morphometric-study/