The role of the visual thalamus in hallucinations in dementia with Lewy bodies

Introduction:Complex visual hallucinations occur in70% of dementia with Lewy bodies (DLB) cases and sig-nificantly affect patient wellbeing. Visual cortical andretinal abnormalities have been recorded in DLB casesand may contribute to visual hallucinations. The visualthalamus plays a vital role in relaying and modulatingsensory input. In particular, the lateral geniculatenucleus (LGN) and pulvinar nucleus play importantroles in relaying optical input and visual attention,respectively. This study therefore determined whetherpathological changes occur in the LGN and pulvinarnucleus in post-mortem tissue taken from hallucinatingDLB patients, when compared against non-hallucinat-ing control and ‘disease control’ Alzheimer’s disease(AD) cases.Material and methods:The LGN from six DLB, seven ADand seven control cases, and the pulvinar nucleus fromeight DLB, eight AD and eight control cases, was seri-ally sectioned for quantitative analyses of cellular pop-ulations using stereology and neuropathological lesionsusing densitometric analysis.Results:In DLB, the LGN was found to be relativelyintact, while greater cell loss and neuropathologicallesions were found in AD cases. In contrast, Lewy bodypathology was found in the pulvinar nucleus of all DLBcases. Additionally, a significant mean 30% neuronalloss was found in the lateral pulvinar of DLB cases.40Abstracts©2016 The AuthorsNeuropathology and Applied Neurobiology©2016 British Neuropathological Society,42(Suppl. 1), 11–52Conclusions:Our results suggest that the pre-corticalprimary visual pathway is structurally intact in DLBcases but that the secondary visual pathway, routedthrough the pulvinar, may be impaired. Degenerationof the lateral pulvinar may lead to visuospatial impair-ments, which are a prominent clinical feature of DLBand are related to the occurrence of visual hallucina-tions.