Visual Hallucination and Pattern of Brain Degeneration in Parkinson's Disease

Abstract

Background and Objectives: The incidence of visual hallucination (VH) increases with Parkinson's disease (PD) progression, and its development is thought to be related to a specific neurodegenerative process in PD. This study aimed to reveal brain degeneration related to VH in PD by analyzing neuroimaging data obtained from patients in their different stages of PD. Methods: Data from 48 PD patients - 21 nondemented without VH (PNV group), 10 nondemented with VH (PV group), and 17 demented with VH (PVD group) - and 30 age-matched healthy controls (HC group) were analyzed. Voxel-based morphometry and tract-based spatial statistics were conducted. Previous magnetic resonance volumetric studies on VH in PD were collectively reviewed. Results: The PV group showed gray matter atrophy in the right inferior parietal lobule and supramarginal gyrus compared with the HC and PNV groups. The PVD group showed a wider range of gray matter atrophies in the temporo-parieto-occipital regions than those in the PV group. White matter changes seemed to be an earlier event than gray matter changes. Fractional anisotropy values diffusely decreased in all three PD subgroups compared with the HC group without significant differences between the PD subgroups. Mean diffusivity was not different between the PNV and HC groups but increased in the parieto-temporal region in the PV group and increased diffusely in the PVD group, additionally including the fronto-occipital regions. A review of previous studies supported our observations. Conclusions: Gray matter degenerations from the parieto-temporal junction to the parieto-occipital and temporo-occipital regions may be responsible for VH on the typical timeline of PD progression.

Fiber-specific white matter reductions in Parkinson hallucinations and visual dysfunction

“…35 In contrast, past whole-brain tensorbased analyses had not revealed any specific white matter changes between PD/VH and PD/non-VH. 36,37 We found widespread reductions in FC, as well as the FDC metric, suggesting that white matter macrostructural changes occur in Parkinson hallucinations together with changes that affect the ability to relay information between brain regions.…”

Structural and Functional Neuroimaging of Visual Hallucinations in Lewy Body Disease: A Systematic Literature Review

“…Studies investigating VH in LBD using more than one approach or imaging technique were included in more than one section of the review and the findings for each technique reported separately in the relevant section. There were eight studies combining different techniques, specifically structural and functional MRI [ 16 , 17 ]; structural MRI and PET [ 18 , 19 ]; structural MRI and DTI [ 20 , 21 ]; structural MRI, DTI, and fMRI [ 22 ]; and fMRI and arterial spin labelling (ASL)-MRI [ 23 ]. Moreover, in two structural MRI studies, different methods were used to investigate regional brain volumes [ 24 , 25 ].…”

“…A total of 12 VBM studies were identified. Ten studies focused on regional volumetric brain differences between LBD patients with and without VH, including nine studies which used whole brain analyses [ 21 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ], and three voxel-based analyses restricted to predefined regions of interest (ROI) [ 28 , 32 , 33 ]. Four studies also included results on the association between grey matter loss and VH or other cognitive variables [ 27 , 32 , 33 , 34 ].…”

“…The VBM methodology implemented was largely consistent between studies. All used the Statistical Parametric Mapping (SPM) software for imaging analysis, and seven [ 21 , 25 , 26 , 27 , 28 , 31 , 35 ] used the Diffeomorphic Anatomical Registration using Exponentiated Lie algebra (DARTEL) algorithm to create a study-specific template. A threshold corrected for multiple comparisons was applied in four whole brain [ 24 , 25 , 30 , 34 ], and four ROI [ 28 , 32 , 33 , 35 ] studies.…”

“…A threshold corrected for multiple comparisons was applied in four whole brain [ 24 , 25 , 30 , 34 ], and four ROI [ 28 , 32 , 33 , 35 ] studies. The results of those studies which used uncorrected thresholds [ 21 , 25 , 26 , 27 , 28 , 31 ] should be interpreted more cautiously, since analyses using an uncorrected threshold may generate a higher number of false positives. Clinical and demographic features, including severity of cognitive impairment, disease duration, age, and years of education varied between studies.…”