Objective: The purpose of this report is to examine the association between visual hallucinations during life and substantia nigra (SN) neuron density and Lewy pathology among autopsied decedents in the Honolulu-Asia Aging Study.

Background: Visual hallucinations are common in Parkinson’s disease (PD) and Lewy Body Dementia. While it is understood that medications taken to alleviate PD symptoms clearly contribute to these findings, it is not known whether visual hallucinations have associations with neurodegenerative processes that predate the classic motor features of PD and its treatment. We measured SN neuron density and assessed presence of Lewy bodies (LB) in the SN and locus coeruleus (LC) in decedents with and without PD or LB Dementia to determine whether low neuron density and LB were associated with hallucinations during life, even in the absence of PD medications or its diagnosis.

Method: Hallucinations, delusions, and paranoia were assessed from 1991 to 2008 using the BEHAVE-AD, in 480 men aged 72 to 103 years with later postmortem examinations. Neuron density (count/mm²) was measured in decedent brains in quadrants from transverse sections of the SN. LB were assessed on hematoxylin and eosin stained slides of the SN and LC.

Results: Visual hallucinations were reported in 13.1% of the men (63/480). Within each SN quadrant, neuron density was lower in the presence versus absence of visual hallucinations. In their presence, loss in neuron density ranged from 30.3% in the dorsolateral quadrant (12.2 vs 8.5/mm², p=0.006) to 39.2% in the dorsomedial quadrant (18.6 vs 11.3/mm², p=0.004). LB were positively associated with visual hallucinations. In their presence, 47.6% of brains had LB compared to 19.9% of those without (p=0.009). Findings persisted for both neuron density and LB in the absence of PD, LB dementia, and other types of hallucinations. Further adjustment for age and clinical correlates of PD failed to alter these findings.

Conclusion: Visual hallucinations are associated with SN neuron loss and presence of LB in decedents without clinical PD or LB dementia, and in the absence of PD medications. Findings suggest that visual hallucinations are related to underlying LB pathology and could be useful for detecting prodromal LB disease states, i.e., prodromal PD or LB Dementia.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/visual-hallucinations-and-parkinsons-disease-neuropathology-among-decedents-with-and-without-parkinsons-disease-or-lewy-body-dementia-during-life/