Visual Hallucinations and Cognitive Impairment in Parkinson's Disease

Background: Visual hallucination (VH) is a common psychotic symptom in patients with Parkinson's disease (PD) and may be a significant predictor of cognitive impairment (CI) in such patients. Objective: This study aimed to investigate the pattern of glucose metabolism of VH and the relationship between VH and CI in PD. Methods: We studied 28 PD patients, including 15 with VH (PD-VH) and 13 without VH (PD-NVH). Of the 15 PD-VH patients, 8 patients had cognitive impalement (PD-VHCI) whereas 7 did not (PD-VHNCI). All patients underwent [F-18] fluorodeoxyglucose positron emission tomography ([F-18] FDG PET) followed by statistical parametric mapping (SPM) analyses. Results: Compared to the patients with PDNVH, PD-VHNCI patients showed glucose hypometabolism in the inferior and middle temporal cortices, fusiform gyri, and frontal areas, suggesting the involvement of the ventral visual pathway. Compared to the patients with PDNVH, PD-VHCI patients showed glucose hypometabolism in the temporoparietal association cortices with scattered frontal areas. Conclusion: Dysfunction of ventral visual pathway involving the temporal lobe may play a key role in VH development in PD patients. The evolving distribution from the ventral visual pathway to more extensive posterior cortices in PD-VHCI patients suggests that VH may be a prodromal symptom occurring prior to CI in PD patients.