Gray matter correlates of progression of motor symptoms in patients with Parkinson’s disease

OBJECTIVE: The objective of this study was to evaluate the gray matter (GM) volume alterations in different clinical stages of Parkinson’s disease (PD) through voxel-based morphometry (VBM). BACKGROUND: Assessment of the clinical stages of PD is usually carried out using the Hoehn and Yahr (H–Y) scale. However, there is paucity of literature on the association of GM atrophy with the progression of motor symptoms in PD. METHODS: Forty-five patients with a diagnosis of PD (H–Y I: 15, H–Y II: 15, H–Y III: 15) and 45 healthy controls (HC) were recruited. T1-weighted images were obtained through a 3-Tesla magnetic resonance imaging machine. VBM was used to compare the regional changes in the GM volume of the three groups. RESULTS: No significant differences were observed in the demographic and clinical characteristics of the groups except in the duration of symptoms (H–Y I vs. H–Y III, 2.7 ± 1.9 vs. 7.4 ± 5.2 years, P < 0.01), and Unified Parkinson’s Disease Rating Scale III ON-state score (H–Y I vs. H–Y III, 16.2 ± 8.4 vs. 24.5 ± 8.3, P < 0.02). Volume of the left parahippocampal gyrus (Brodmann area 34) was significantly different among the four groups. Post hoc analysis revealed gradual reduction in the volume of the parahippocampal gyrus from H–Y stage I (highest) to H–Y stage III (lowest). CONCLUSION: There is progressive decrease in GM volume of the parahippocampal gyrus with the advancement of stage of PD. This result suggests that the volume of parahippocampal gyrus may represent one of the neuroimaging correlates of the H–Y staging of PD.