Structural and Functional Neuroimaging of Visual Hallucinations in Lewy Body Disease: A Systematic Literature Review
OBJECTIVE To determine the course of cognitive deficits and the regional progression of brain atrophy in patients with Parkinson's disease (PD) with and without visual hallucinations (VH). METHODS The authors performed MRI and neuropsychological assessment at entry to the study and at follow-up (mean+/-SD=29.91+/-5.74 months) in a sample of initially non-demented 12 PD patients with VH, 14 PD patients without VH and 12 healthy controls (HC). Grey-matter changes over time were assessed by means of voxel-based morphometry (VBM) and cognitive changes by an extensive neuropsychological battery. RESULTS At follow-up, 75% of patients with VH developed dementia. The greatest decline was observed in verbal memory, semantic fluency, language comprehension and visuoperceptive functions. None of the patients without VH met criteria for dementia and did not show any worsening in cognitive functions over time. Patients with VH showed widespread limbic, paralimbic and neocortical grey-matter loss, whereas in the PD without VH group, grey-matter loss was restricted to a small region in the frontal cortex and cerebellum. The authors also found significant correlations between the changes in several cognitive functions and grey-matter loss over time in PD patients with VH. CONCLUSION The presence of VH in PD determines a different cognitive outcome and a different pattern of progressive brain atrophy. PD patients with VH, unlike PD without VH, frequently develop dementia and show a widespread atrophy involving limbic, paralimbic and neocortical areas.