Background: Parkinson disease with dementia (PDD) results from neuropathological changes in cortical and subcortical brain regions. Voxel-based morphometric analysis of magnetic resonance images can contribute to in vivo identification of the cerebral regions predominantly involved in PDD.Objective: To identify structural cerebral regions most closely related to the presence of PDD.Design: Magnetic resonance images were obtained from 16 patients who had PDD, 13 patients with PD without dementia, and 13 age-matched healthy control subjects. Gray matter volumes were compared using optimized voxel-based morphometric analyses.Results: Compared with healthy controls, patients with PDD showed gray matter volume decreases in several of the following regions: bilateral putamen, accumbens nuclei, left side of the thalamus, bilateral hippocampus, parahippocampal region, and anterior cingulate gyrus. Patients with PD also showed gray matter reductions compared with healthy controls in the right side of the hippocampus, left anterior cingulate gyrus, and left superior temporal gyrus. Conclusions:The hippocampus, thalamus, and anterior cingulate are the regions most affected in PDD. Our results agree with recent neuropathological findings suggesting the involvement of the limbic and cortical areas in PD.

Although visual hallucinations (VH) are relatively frequent in Parkinson's disease (PD) patients, their neural substrates are only known from neuropathological and functional magnetic resonance studies. The aim of this study was to investigate possible structural brain changes on MRI in non-demented PD patients with VH using voxel-based morphometry. Eighteen PD patients with VH were compared to 20 patients with PD without VH and 21 healthy controls. Compared with both controls and the non-hallucinating PD group, PD patients with VH had grey matter volume reductions in the lingual gyrus and superior parietal lobe. Structural changes in these areas involved in higher visual processing may be important in understanding the VH and visual deficits in PD patients.

We studied regional gray matter density in the hippocampus in Parkinson's disease (PD) patients. We obtained magnetic resonance scans in 44 PD patients (PD patients with dementia (PDD) = 9, non-demented PD patients with visual hallucinations (PD + VH) = 16, and PD patients without dementia and without visual hallucinations (PD - VH) = 19) and 56 controls matched for age and years of education. A region of interest (ROI) of the hippocampus following voxel-based morphometry (VBM) procedures was used to perform group comparisons, single-case individual analysis and correlations with learning scores. Group comparisons showed that PDD patients and PD+VH patients had significant hippocampal gray matter loss compared to controls. In PDD patients, hippocampal gray matter loss involved the entire hippocampus and in PD+VH this reduction was mainly confined to the hippocampal head. 78 % of PDD patients, 31 % of PD+VH patients and 26 % of PD-VH patients had hippocampal head gray matter loss when compared to controls. These results suggest that in PD the neurodegenerative process in the hippocampus starts in the head of this structure and later spreads to the tail and that, in addition, memory impairment assessed by Rey's Auditory Verbal Learning Test (RAVLT) correlates with hippocampal head gray matter loss.