Changes to the lateral geniculate nucleus in Alzheimer's disease but not dementia with Lewy bodies.

Neuropathology and applied neurobiology

PubMedID: 25967384

Erskine D, Taylor JP, Firbank MJ, Patterson L, Onofrj M, O'Brien JT, McKeith IG, Attems J, Thomas AJ, Morris CM, Khundakar AA. Changes to the lateral geniculate nucleus in Alzheimer's disease but not dementia with Lewy bodies. Neuropathol Appl Neurobiol. 2016;.
AIMS
Complex visual hallucinations occur in 70% of dementia with Lewy bodies (DLB) cases and significantly affect patient well-being. Visuo-cortical and retinal abnormalities have been recorded in DLB and may play a role in visual hallucinations. The present study aimed to investigate the lateral geniculate nucleus (LGN), a visual relay centre between the retina and visual cortex, to see if changes to this structure underlie visual hallucinations in DLB.

METHODS
Fifty-one [17 probable DLB, 19 control and 15 probable Alzheimer's disease (AD)] cases were recruited for a functional magnetic resonance imaging study, in which patients' response to a flashing checkerboard stimulus was detected and measured in the LGN, before comparison across experimental groups. Additionally, post mortem LGN tissue was acquired for a cross-sectional study using 20 (six DLB, seven control and seven AD) cases and analysed using stereology. a-Synuclein, phosphorylated tau and amyloid-ß pathology was also assessed in all cases.

RESULTS
DLB cases did not significantly differ from controls on neuroimaging, morphometry or pathology. However, a significant increase in amyloid-ß pathology, a reduction in number of parvocellular neurones and magnocellular gliosis was found in AD cases compared with control and DLB cases.

CONCLUSIONS
These findings suggest that the early visual system is relatively spared in DLB, which implies that upstream visual structures may be largely responsible for the generation of hallucinatory percepts. The significance of the degeneration of the LGN in AD cases is uncertain.