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Visual hallucinations (VH) are common in Parkinson’s disease (PD) and lead to a poor quality of life. For a long time, dopaminergic therapy was considered to be the most important risk factor for the development of VH in PD. Recently, the cholinergic system, including the pedunculopontine nucleus (PPN), has been implicated in the pathophysiology of VH. The aim of the present study was to investigate grey matter density of the PPN region and one of its projection areas, the thalamus. Thirteen non-demented PD patients with VH were compared to 16 non-demented PD patients without VH, 13 demented PD patients (PDD) with VH and 11 patients with dementia with Lewy bodies (DLB). Isotropic 3-D T1-weighted MRI images (3T) were analysed using voxel-based morphometry (VBM) with the PPN region and thalamus as ROIs. PD and PDD patients with VH showed grey matter reductions of the PPN region and the thalamus compared to PD patients without VH. VH in PD(D) patients are associated with atrophy of the PPN region and its thalamic target area, suggesting that a cholinergic deficit may be involved in the development of VH in PD(D).

Unilateral stroke can lead to a disorder of postural balance that manifests as a pushing away toward the contralesional side. It is called "pusher syndrome" (PS). The aims of this study were first to assess the anatomical cortical regions that induce PS and second to clarify whether tilt of the subjective visual vertical (SVV)--a sign of vestibular otolith dysfunction--is associated with PS. Sixty-six patients with acute unilateral strokes (28 left-sided lesions, 38 right-sided lesions) were tested for PS, for tilts of the SVV, for hemineglect and for the anatomical lesion site by magnetic resonance imaging (MRI)-based voxelwise lesion-behavior mapping analysis. Our data indicated no significant voxels; however, there was a trend towards an association between lesions of the posterior part of the insula, the operculum and the superior temporal gyrus--key areas of the multisensory vestibular cortical network--and the extent of pushing in patients with right-sided lesions, whereas the rather anterior part of the insula, the operculum as well as the internal capsule reaching to the lateral thalamus seemed to be involved in PS in left-sided lesion patients. These data might point toward a link between the systems responsible for postural control and for processing vestibular otolith information. These findings indicate that vestibular information might be fundamental in right-sided lesion patients for maintaining body posture in space.

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