Regional cortical grey matter loss in Parkinson's disease without dementia is independent from visual hallucinations.

In our previous functional magnetic resonance imaging study, Parkinson's disease (PD) patients with visual hallucinations (VH) showed reduced activations in ventral/lateral visual association cortices preceding image recognition, compared with both PD patients without VH and healthy controls. The primary aim of the current study was to investigate whether functional deficits are associated with grey matter volume changes. In addition, possible grey matter differences between all PD patients and healthy controls were assessed. By using 3-Tesla magnetic resonance imaging (MRI) and voxel-based morphometry (VBM), we found no differences between PD patients with (n = 11) and without VH (n = 13). However, grey matter decreases of the bilateral prefrontal and parietal cortex, left anterior superior temporal, and left middle occipital gyrus were found in the total group of PD patients, compared with controls (n = 14). This indicates that previously demonstrated functional deficits in PD patients with VH are not associated with grey matter loss. The strong left parietal reduction in both nondemented patient groups was hemisphere specific and independent of the side of PD symptoms.