Dementia and visual hallucinations associated with limbic pathology in Parkinson's disease
Introduction
The pathological hallmark of Parkinson's disease (PD) is the aggregation of α-synuclein (αSyn) in Lewy bodies (LBs) and in the form of Lewy neurites (LNs). While the disease is initially characterized by motor deficits, later on dementia and visual hallucinations (VH) are commonly present [1], [2], [3], [4], [5], [6], [7] although the specific anatomical and pathological correlates of these clinical features remain unclear. The presence of LBs in limbic and neocortical regions has been suggested as a cause for cognitive impairment and dementia but this does not account for co-existent Alzheimer's disease (AD)-type changes that are often found alongside αSyn pathology. In cases with mixed pathology it is difficult to determine whether LBs or AD-type pathology are responsible for dementia. In addition, to date there have been few neuropathologic studies of PD patients with VH [8], [9], [10] and the anatomico-pathological correlate(s) for VH is/are still unknown.
In this study, we assessed the association between dementia and VH with αSyn and AD-type pathology (amyloid β peptide (Aβ) and tau) using an experimental design that enabled us to isolate clinical features of interest and study their anatomical and pathological basis.
Section snippets
Clinical assessment and selection of cases
Clinical data of cases were compiled retrospectively from hospital records into summaries by a movement disorder neurologist (RKBP). Only subjects who had been evaluated by a clinician within 2 years prior to death and had complete clinical histories were included. The clinical diagnoses of PD, PDD and dementia with Lewy bodies (DLB) were based on published criteria [11], [12], [13]. PD was considered to be present if the patient had at least 2 of the 4 cardinal symptoms (rigidity, hypokinesia,
Results
For the 30 PD cases included in this study (Table 1) age at disease onset and age at death did not differ between groups, however PD(H+) cases had a statistically significant longer disease duration (p = 0.03). All PD cases had received medication with the potential to exacerbate hallucinations (Table 1).
Statistical analysis revealed a significant association between dementia in PD and αSyn burden in the ACG (p = 0.001), superior frontal gyrus (p = 0.02), temporal cortex (p = 0.02), entorhinal cortex (p
Discussion
Dementia is a common feature in PD but its anatomical correlates remain a matter of controversy. In our cases dementia was associated with significant degenerative changes in the limbic system. While the number of our cases with dementia was relatively small (n = 16), pathological changes in the amygdaloid complex, entorhinal cortex, ACG and CA2 sector of the hippocampus seem likely responsible for dementia in PD. Other recently published findings demonstrate a relationship between LB densities
Acknowledgements
This work was funded by the UK Parkinson's Disease Society, registered charity 948776. SMG is funded in part by NIH grant AG12411. Tissue samples were supplied by the Parkinson's Disease Society Tissue Bank at Imperial College London, funded by the Parkinson's Disease Society of the United Kingdom. The help of tissue bank members is greatly appreciated. The authors would also like to thank Dr Federico Turkheimer for his statistical advice. We express our deepest appreciation to the donors and
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