Plaques and tangles as well as Lewy-type alpha synucleinopathy are associated with formed visual hallucinations

Mild behavioural impairment in Parkinson's disease: a systematic review

Behavioural symptoms are common manifestations of Parkinson's disease (PD). Early behavioural symptoms characterise mild behavioural impairment (MBI). The prevalence and intensity of MBI in people with PD (PwP) have been studied across various cohorts. However, methodological differences have obscured our understanding of MBI in these individuals. This systematic review examines and synthesises findings from relevant studies, enhancing understanding of the symptoms and implications of MBI in PD. Nine studies from five separate research institutions were identified. The conceptualisation of MBI varied considerably, affecting the reported prevalence rates of MBI in individuals with early-stage PD. Among PwP, MBI was associated higher education and impaired cognition. Affective dysregulation and impulse control disorders were primary contributors to MBI; abnormal perception was least contributor. This systematic review underscores the specific characteristics and incidence of MBI in early-stage PD. Mood and impulse control disorders are primary concerns associated with MBI. Future longitudinal studies are required to clarify the progression of these symptoms and evaluate MBI's potential as an indicator for PD-related dementia or increased dependency.

"Advanced" Parkinson's disease: A review

There is no consensus driven definition of "advanced" Parkinson's disease (APD) currently. APD has been described in terms of emergence of specific clinical features and clinical milestones of the disease e.g., motor fluctuations, time to increasing falls, emergence of cognitive decline, etc. The pathological burden of disease has been used to characterize various stages of the disease. Imaging markers have been associated with various motor and nonmotor symptoms of advancing disease. In this review, we present an overview of clinical, pathologic, and imaging markers of APD. We also propose a model of disease definition involving longitudinal assessments of these markers as well as quality of life metrics to better understand and predict disease progression in those with Parkinson's disease.

Predictors for early-onset psychotic symptoms in patients newly diagnosed with Parkinson's disease without psychosis at baseline: A 5-year cohort study

AIMS

To investigate the risk factors for early-onset psychosis in Parkinson's disease (PD) in a cohort of patients from the Parkinson's Progression Markers Initiative.

METHODS

Longitudinal data on motor and non-motor features, dopamine transporter (DAT) imaging, and cerebrospinal fluid (CSF) measurements were collected. The survival probability of psychotic symptoms, potential risk factors for psychosis development over a 5-year follow-up period, and the performance of the prediction model were evaluated.

RESULTS

Among the 338 newly diagnosed patients with PD, 83 developed psychotic symptoms. Gastrointestinal autonomic dysfunction, presence of probable rapid-eye-movement sleep behavior disorder, and the ratio Aβ42: total-tau could independently predict onset of psychosis in PD (hazard ratio (HR) = 1.157, 95% confidence interval (CI) 1.022-1.309, p = 0.021, HR = 2.596, 95% CI 1.287-5.237, p = 0.008, and HR = 0.842, 95% CI 0.723-0.980, p = 0.027, respectively). The combined model integrating baseline clinical predictors, DAT imaging, and CSF measurements achieved better sensitivity than the clinical predictors alone (area under the curve = 0.770 [95% CI 0.672-0.868] vs. 0.714 [95% CI 0.625-0.802], p = 0.098).

CONCLUSION

We identified clinical and CSF predictors of early-onset psychosis in patients with PD. Our study provides evidence and implications for prognostic stratification and therapeutic approaches for PD psychosis.

Behavioral and neural correlates of pareidolic illusions in dementia with Lewy bodies

INTRODUCTION

Pareidolia, a form of visual illusions phenomenologically similar to complex visual hallucinations, is a phenomenon that is associated with visual hallucinations in dementia with Lewy bodies (DLB). This study aimed to identify commonalities and differences in behavioral and neural correlates between pareidolic illusions and visual hallucinations in DLB.

METHODS

Forty-three patients with DLB underwent the scene pareidolia test, which evokes and measures pareidolic illusions, and standardized neuropsychological and behavioral assessments. Regional cerebral blood flow (rCBF) was measured by single-photon emission computed tomography. Factor analysis was performed to assess the relationships among pareidolic illusions, cognitive functions, and behavioral symptoms. Partial least squares correlation analysis was used to investigate the relationship between these symptoms and rCBF.

RESULTS

Factor analysis yielded three behavior factors: the first factor (hallucinations/fluctuations) consisted of pareidolic illusions, visual hallucinations, and fluctuating cognition; the second factor (general cognitive function) consisted of general cognitive function and working memory; and the third factor (visual processing) consisted of visual processing and pareidolic illusions. Partial least squares correlation analysis identified two brain-behavior correlation patterns: (1) rCBF reduction in the frontal and perisylvian/periventricular regions was associated with lower general cognitive function and lower visual processing; and (2) rCBF reduction in the bilateral occipitotemporal cortex was associated with more severe hallucinations/fluctuations and lower visual processing.

CONCLUSIONS

At the behavioral level, pareidolic illusions are associated with visual hallucinations, fluctuating cognition, and visual processing in DLB. At the neural level, pareidolic illusions may arise from the synergistic effects of global neuropathological changes and occipitotemporal cortical dysfunctions.

Neuropathological correlates of neuropsychiatric symptoms in dementia

INTRODUCTION

Neuropsychiatric symptoms (NPS) are common in Lewy body disease (LBD), but their etiology is poorly understood.

METHODS

In a population-based post mortem study neuropathological data was collected for Lewy body (LB) neuropathology, neurofibrillary tangles (NFT), amyloid beta burden, TDP-43, lacunar infarcts, cerebral amyloid angiopathy (CAA), and hyaline atherosclerosis. Post mortem interviews collected systematic information regarding NPS and cognitive status. A total of 1038 cases were included: no pathology (NP; n = 761), Alzheimer's disease (AD; n = 189), LBD (n = 60), and AD+LBD (n = 28).

RESULTS

Hallucinations were associated with higher LB Braak stages, while higher NFT Braak staging was associated with depression, agitation, and greater number of symptoms in the Neuropsychiatric Inventory. Cases with dual AD+LBD pathology had the highest risk of hallucinations, agitation, apathy, and total symptoms but a multiplicative interaction between these pathologies was not significant.

DISCUSSION

LB and AD pathology contribute differentially to NPS likely with an additive process contributing to the increased burden of NPS.

Potential roles of oxidative distress on neurodegeneration in Parkinson's disease with neuropsychiatric symptoms

Background

Neuropsychiatric symptoms (NPSs) belong to a category of non-motor symptoms of Parkinson's disease (PD), which seriously compromise the quality of life and prognosis of PD. This study focused on the correlations between NPSs, free radicals, neuroinflammatory factors, and neuropathological proteins in cerebrospinal fluid (CSF) in patients with PD, aiming to provide insights into the potential mechanisms and therapeutic target for PD with NPSs (PD-NPSs).

Methods

In total, 129 patients with PD were enrolled and assessed by the Neuropsychiatric Symptoms Inventory (NPI); they were divided into the PD-NPSs group (75 patients) and PD with no NPSs (PD-nNPSs) group (54 patients). The levels of hydrogen peroxide (H₂O₂) and nitric oxide (NO), and hydroxyl radical (·OH), anti-oxidative enzyme, neuroinflammatory factors, and neuropathological proteins in CSF from patients with PD were measured. The levels of the above variables were compared between PD-NPSs and PD-nNPSs groups, and correlation analyses among the above variables were conducted.

Results

(1) The levels of H₂O₂ and NO in CSF from the PD-NPSs group were significantly elevated compared with the PD-nNPSs group (p = 0.001), and NPI score positively correlated with the levels of H₂O₂ and NO (r = 0.283, P = 0.001; r = 0.231, P = 0.008). Reversely, total superoxide dismutase (tSOD) activity in CSF from the PD-NPSs group was significantly reduced compared with the PD-nNPSs group (p = 0.011), and negatively correlated with NPI score (r = -0.185, p = 0.036). (2) The tumor necrosis factor (TNF)-α level in CSF from the PD-NPSs group was significantly decreased compared with the PD-nNPSs group (p = 0.002) and negatively correlated with NPI score (r = -0.211, p = 0.016). (3) The total tau (T-tau) level in CSF from the PD-NPSs group was significantly higher than in the PD-nNPSs group (p = 0.014) and positively correlated with the NPI score (r = 0.167, p = 0.060). (4) The levels of H₂O₂ and NO positively correlated with the T-tau level in CSF from the PD-NPSs group (r = 0.183, p = 0.039; r = 0.251, P = 0.004), and the levels of TNF-α and T-tau showed a negative correlation (r = -0.163, p = 0.067).

Conclusion

Oxidative distress characterized by the elevations of H₂O₂ and NO levels may closely correlate with the neurodegeneration in brain regions related to PD-NPSs. Thus, therapeutic antioxidants may become an important target for PD-NPSs therapy.

Emerging role of psychosis in Parkinson's disease: From clinical relevance to molecular mechanisms

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Psychosis is one of the common psychiatric presentations in the natural course of PD. PD psychosis is an important non-motor symptom, which is strongly correlated with a poor prognosis. Increasing attention is being given to PD psychosis. In this opinion review, we summarized and analyzed the identification, screening, epidemiology, mechanisms, risk factors, and therapeutic approaches of PD psychosis based on the current clinical evidence. PD psychosis tends to have a negative effect on patients' quality of life and increases the burden of family caregiving. Screening and identification in the early stage of disease is crucial for establishing tailored therapeutic strategies and predicting the long-term outcome. Development of PD psychosis is believed to involve a combination of exogenous and endogenous mechanisms including imbalance of neurotransmitters, structural and network changes, genetic profiles, cognitive impairment, and antiparkinsonian medications. The therapeutic strategy for PD psychosis includes reducing or ceasing the use of dopaminergic drug, antipsychotics, cholinesterase inhibitors, and non-pharmacological interventions. Ongoing clinical trials are expected to provide new insights for tailoring therapy for PD psychosis. Future research based on novel biomarkers and genetic factors may help inform individualized therapeutic strategies.

Possible Contribution of Altered Cholinergic Activity in the Visual Cortex in Visual Hallucinations in Parkinson's Disease

OBJECTIVE

Up to one-third of patients with Parkinson's disease (PD) experience visual hallucinations (VHs). Lewy bodies are sparse in the visual cortices and seem unlikely to explain the hallucinations. Some neuroimaging studies have found that perfusion is reduced in the occipital lobe in individuals with VHs. Recent work has suggested that decreased cholinergic input may directly lead to the decreased perfusion. The investigators hypothesized that individuals with PD and VHs would have biochemical evidence of reduced microvascular perfusion and reduced cholinergic activity in areas of the brain that process visual images.

METHODS

Tissue from Brodmann's area (BA) 18 and BA 19 was obtained from a well-characterized cohort matched for age, gender, and postmortem interval in 69 individuals (PD without VHs, N=11; PD without dementia plus VHs N=10, N=10; PD with dementia plus VHs, N=16; and control subjects, N=32). Von Willebrand factor, vascular endothelial growth factor A, and myelin-associated glycoprotein:proteolipid protein-1 (MAG:PLP1) ratio-a measure of tissue oxygenation relative to metabolic demand, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), choline acetyltransferase, and α-synuclein-were quantified by enzyme-linked immunosorbent assay. The primary outcome was the MAG:PLP1 ratio.

RESULTS

There was no biochemical evidence of chronic hypoperfusion in PD, although microvessel density was decreased in ventral BA 18 and BA 19. There was no between-group difference in BChE in either dorsal BA 18 or BA 19. AChE concentration was reduced in individuals with PD compared with control subjects in dorsal and ventral BA 18 and dorsal BA 19, and it was increased in ventral BA 19. These changes were most marked in the PD plus VHs group.

CONCLUSIONS

These results suggest that changes in cholinergic activity rather than chronic hypoperfusion may underlie VHs in PD.

Associations Between Neuropsychiatric Symptoms and Neuropathological Diagnoses of Alzheimer Disease and Related Dementias

IMPORTANCE

Understanding associations of Alzheimer disease (AD) and related dementias (ADRD) pathologies with common neuropsychiatric symptoms (NPS) may have implications for diagnosis and management.

OBJECTIVE

To evaluate ADRD neuropathological diagnoses and NPS without consideration of clinical diagnosis.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study evaluated 1808 brains from 39 sites in the US National Alzheimer Coordinating Center v. 10 collection for participants among whom the Neuropsychiatric Inventory Questionnaire (NPIQ) was administered annually. Brain autopsy diagnoses of AD, Lewy body disease (LBD), cerebral amyloid angiopathy, frontotemporal lobar degeneration, cerebrovascular disease, hippocampal sclerosis, and no known pathology were examined. Autopsy data collected from January 2012 to January 2018 were deidentified and compiled into the publicly available v. 10 database. Data were analyzed from February 2021 to August 2021.

MAIN OUTCOMES AND MEASURES

The primary outcome was NPIQ domain score, if present at any time point, and mean NPIQ domain score during follow-up was secondary. Associations of ADRD diagnoses with 12 NPIQ symptom domains were examined in regression analyses, correcting for multiple comparisons.

RESULTS

The study sample of 1808 adults had a mean (SD) age of 80.0 (11.0) years, and 987 participants (54.6%) were male. Apathy was the most prevalent NPS, reaching 80% (203 of 254 individuals) in those with hippocampal sclerosis. Cerebrovascular disease showed few NPS associations. Frontotemporal lobar degeneration was associated with increased apathy, increased disinhibition, and decreased psychosis and agitation compared with AD. Hippocampal sclerosis was associated with increased apathy (odds ratio, 2.60; 95% CI; 1.86-3.66, false discovery rate controlled P < .001) and disinhibition (odds ratio, 2.15; 95% CI, 1.63-2.84; false discovery rate controlled P < .001). In multiple regression analyses that included concomitant neuropathologies, the main findings remained. More severe pathology was consistently associated with increased NPS (eg, LBD was associated with an increase in hallucinations from brain stem [β, 0.23; 95% CI, 0.07-0.76; P = .02] to limbic [β, 1.69; 95% CI, 1.27-2.27; P < .001] to neocortical [β, 4.49; 95% CI, 3.27-6.16; P < .001] pathology). Hallucinations were more common in participants with AD and LBD (168 of 534 [31.5%]) compared with those with AD without LBD (152 of 704 [21.6%]) and those with LBD without AD (23 of 119 [19.6%]).

CONCLUSIONS AND RELEVANCE

In this cohort study of 1808 brains from the US National Alzheimer Coordinating Center, patients with LBD and AD showed a higher prevalence of hallucinations compared with those with LBD without AD. Neuropsychiatric symptom criteria of apathy and disinhibition in behavioral variant frontotemporal lobar degeneration were supported in this study. In hippocampal sclerosis, the findings of increased apathy and disinhibition merit further investigation. Severity of neuropathology was associated with NPS severity, indicating that NPS may reflect underlying ADRD pathology and highlighting the importance of diagnosing and treating NPS.

Psychiatric symptoms of frontotemporal dementia and subcortical (co-)pathology burden: new insights

Three subtypes of distinct pathological proteins accumulate throughout multiple brain regions and shape the heterogeneous clinical presentation of frontotemporal lobar degeneration (FTLD). Besides the main pathological subtypes, co-occurring pathologies are common in FTLD brain donors. The objective of this study was to investigate how the location and burden of (co-)pathology correlate to early psychiatric and behavioural symptoms of FTLD. Eighty-seven brain donors from The Netherlands Brain Bank cohort (2008-2017) diagnosed with FTLD were included: 46 FTLD-TAR DNA-binding protein 43 (FTLD-TDP), 34 FTLD-tau, and seven FTLD-fused-in-sarcoma (FTLD-FUS). Post-mortem brain tissue was dissected into 20 standard regions and stained for phosphorylated TDP-43, phosphorylated tau, FUS, amyloid-β, and α-synuclein. The burden of each pathological protein in each brain region was assessed with a semi-quantitative score. Clinical records were reviewed for early psychiatric and behavioural symptoms. Whole-brain clinico-pathological partial correlations were calculated (local false discovery rate threshold = 0.01). Elaborating on the results, we validated one finding using a quantitative assessment of TDP-43 pathology in the granular layer of the hippocampus in FTLD-TDP brain donors with (n = 15) and without (n = 15) hallucinations. In subcortical regions, the presence of psychiatric symptoms showed positive correlations with increased hippocampal pathology burden: hallucinations with TDP-43 in the granular layer (R = 0.33), mania with TDP-43 in CA1 (R = 0.35), depression with TDP-43 in CA3 and with parahippocampal tau (R = 0.30 and R = 0.23), and delusions with CA3 tau (R = 0.26) and subicular amyloid-β (R = 0.25). Behavioural disinhibition showed positive correlations with tau burden in the thalamus (R = 0.29) and with both TDP-43 and amyloid-β burden in the subthalamus (R = 0.23 and R = 0.24). In the brainstem, the presence of α-synuclein co-pathology in the substantia nigra correlated with disinhibition (R = 0.24), tau pathology in the substantia nigra correlated with depression (R = 0.25) and in the locus coeruleus with both depression and perseverative/compulsive behaviour (R = 0.26 and R = 0.32). The quantitative assessment of TDP-43 in the granular layer validated the higher burden of TDP-43 pathology in brain donors with hallucinations compared to those without hallucinations (P = 0.007). Our results show that psychiatric symptoms of FTLD are linked to subcortical pathology burden in the hippocampus, and hallucinations are linked to a higher burden of TDP-43 in the granular layer. Co-occurring non-FTLD pathologies in subcortical regions could contribute to configuring the clinical phenotype of FTLD.

Plasma Neurofilament Light and p-tau181 and Risk of Psychosis in Parkinson's Disease

BACKGROUND

Neuropsychiatric symptoms are common and important to people with Parkinson's disease (PD), but their etiology is poorly understood. Plasma neurofilament light (NfL) and p-tau181 are biomarkers of neuro-axonal degeneration and tau pathology respectively, which have yet to be explored in association with the affective and psychotic symptoms in PD.

OBJECTIVE

To investigate the relationship between plasma NfL and p-tau181 with the affective and psychotic symptoms in PD.

METHODS

We assessed the baseline concentration of plasma NfL and p-tau181 in a cohort of 108 patients with PD and 38 healthy controls. A subgroup of patients (n = 63) were assessed annually with clinical measures for up to 7 years. Psychotic symptoms were assessed using the Non-Motor Symptom Scale and affective symptoms were measured in the Hospital Anxiety and Depression Scale.

RESULTS

Baseline plasma NfL was a significant predictor of psychotic symptoms longitudinally across the study adjusted for age, Hoehn and Yahr stage, duration of follow up, duration of disease, baseline levodopa and dopamine agonist medication, and baseline cognition: (OR 8.15 [95% CI 1.40-47.4], p = 0.020). There was no association between NfL concentration and the cumulative prevalence of affective symptoms. Plasma p-tau181 concentration was not associated with psychotic or affective symptoms.

CONCLUSION

These findings suggest psychotic symptoms are associated with greater neurodegeneration in PD. Further studies are needed to explore NfL as a potential biomarker for psychosis in PD.

[Causes of visual hallucinations in Parkinson's disease]

BACKGROUND

Visual hallucinations (VH) have mainly been considered as late symptoms of Parkinson's disease (PD); however, minor forms of VH also occur in early stages of the disease. Initially dopaminergic overstimulation was discussed as the cause and later on VH have been considered as an early red flag of dementia in PD.

OBJECTIVE

The present study analyzed whether the pathophysiological concept of VH has been enlarged in recent years.

MATERIAL AND METHODS

Clinical, pharmacological, neuropathological as well as functional magnetic resonance imaging studies dealing with VH were reviewed. A systematic classification in monomodal and multimodal models of VH is proposed. The applicability to various forms of VH and various triggering situations is critically examined.

RESULTS

Reduction of the visual information input, erroneous visual processing, attention deficits, and dysfunctional connectivity between various cerebral networks have been shown. There is partial overlapping with the Lhermitte syndrome and the Charles Bonnet syndrome. No model is able to fully explain all VH variants. Not all VH have the same pathogenesis and the same poor prognosis.

CONCLUSION

The chain of causes underlying VH is complex and can vary from patient to patient. So far the therapeutic applications are largely unexplored; however, there is preliminary evidence that beside adjustment of the medication, improvement of visual acuity, active involvement of the partner, and possibly, individually adaptable coping strategies could be successfully implemented.

Soluble endogenous oligomeric α-synuclein species in neurodegenerative diseases: Expression, spreading, and cross-talk

There is growing recognition in the field of neurodegenerative diseases that mixed proteinopathies are occurring at greater frequency than originally thought. This is particularly true for three amyloid proteins defining most of these neurological disorders, amyloid-beta (Aβ), tau, and alpha-synuclein (αSyn). The co-existence and often co-localization of aggregated forms of these proteins has led to the emergence of concepts positing molecular interactions and cross-seeding between Aβ, tau, and αSyn aggregates. Amongst this trio, αSyn has received particular attention in this context during recent years due to its ability to modulate Aβ and tau aggregation in vivo, to interact at a molecular level with Aβ and tau in vivo and to cross-seed tau in mice. Here we provide a comprehensive, critical, and accessible review about the expression, role and nature of endogenous soluble αSyn oligomers because of recent developments in the understanding of αSyn multimerization, misfolding, aggregation, cross-talk, spreading and cross-seeding in neurodegenerative disorders, including Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, Alzheimer's disease, and Huntington's disease. We will also discuss our current understanding about the relative toxicity of endogenous αSyn oligomers in vivo and in vitro, and introduce potential opportunities to counter their deleterious effects.

Visual Hallucinations and the Role of Medications in Parkinson's Disease: Triggers, Pathophysiology, and Management

Visual hallucinations, which are part of the syndrome of Parkinson's disease (PD) psychosis, affect patients' quality of life and increase the likelihood of residential aged-care placement. The association between visual hallucinations and dopaminergic and other medications that are necessary for the symptomatic management of motor and other symptoms of PD is a common clinical dilemma. While dopaminergic medications have long been associated with PD psychosis, a clear causal link has not been established, and other neurotransmitter systems, particularly noradrenaline, serotonin, and acetylcholine, are implicated and important. A diverse range of demographic and disease-related risk factors, some being modifiable, highlight the complexity of potential underlying pathophysiological processes but also broaden practical options for prevention and treatment that can be multifaceted and individualized. The investigators reviewed the clinical features and epidemiology of visual hallucinations and PD, explored the pathological evidence for dysfunction of multiple neurotransmitter systems that may be relevant to these phenomena, and addressed the potential of medications commonly used in PD to either trigger or treat these symptoms.

Neuroanatomical and cognitive correlates of visual hallucinations in Parkinson's disease and dementia with Lewy bodies: Voxel-based morphometry and neuropsychological meta-analysis

Visual hallucinations (VH) are common in Parkinson's disease and dementia with Lewy bodies, two forms of Lewy body disease (LBD), but the neural substrates and mechanisms involved are still unclear. We conducted meta-analyses of voxel-based morphometry (VBM) and neuropsychological studies investigating the neuroanatomical and cognitive correlates of VH in LBD. For VBM (12 studies), we used Seed-based d Mapping with Permutation of Subject Images (SDM-PSI), including statistical parametric maps for 50% of the studies. For neuropsychology (35 studies), we used MetaNSUE to consider non-statistically significant unreported effects. VH were associated with smaller grey matter volume in occipital, frontal, occipitotemporal, and parietal areas (peak Hedges' g -0.34 to -0.49). In patients with Parkinson's disease without dementia, VH were associated with lower verbal immediate memory performance (Hedges' g -0.52). Both results survived correction for multiple comparisons. Abnormalities in these brain regions might reflect dysfunctions in brain networks sustaining visuoperceptive, attention, and executive abilities, with the latter also being at the basis of poor immediate memory performance.

Cognitive correlates and baseline predictors of future development of visual hallucinations in dementia with Lewy bodies

Visual hallucinations (VH) are common in dementia with Lewy bodies (DLB), and are among the core symptoms for its clinical diagnosis. VH have been associated with cognitive alterations, although research findings in this area are still limited. The present study aimed at investigating the cognitive correlates of VH in DLB, and the baseline neuropsychological features predicting the future development of VH. A cross sectional study compared the cognitive profile of 18 DLB patients with VH with that of 32 DLB without VH. A longitudinal study involved 34 DLB patients with no VH at baseline, among whom 17 developed VH and 17 remained without VH at follow-up. Logistic regression analyses were carried out to investigate what baseline cognitive variables independently predicted the development of VH at follow-up. DLB patients with VH had worse performance on the copy of the Rey complex figure, assessing visual construction/perception, than those without VH in the cross-sectional study (p = .001). Significant impairments in attention and visual memory delayed recall were also present. Baseline performance on the immediate prose memory was the only significant predictor of VH development in the longitudinal study (p = .03). DLB patients are more at risk of developing VH if presenting more severe immediate verbal memory impairment, and this might be related to a combination of (a) DMN-related dysfunctions, (b) impairment in medial temporal lobe-related functions, and (c) frontal abilities including long-term encoding of information and working memory. Differences between hallucinating and non-hallucinating patients in visual construction/perception, typical of DLB symptomatology, may be essential for VH to emerge in individuals with an at risk cognitive profile.

Treating hallucinations in Parkinson's disease

Introduction: Hallucinations in Parkinson's disease are common, can complicate medication management and significantly impact upon the quality of life of patients and their carers.Areas covered: This review aims to examine current evidence for the management of hallucinations in Parkinson's disease.Expert opinion: Treatment of hallucinations in Parkinson's disease should be both individualized and multifaceted. Screening, education, medication review and the avoidance of common triggers are important. For well-formed visual hallucinations, acetylcholinesterase inhibitors are recommended first-line. Refractory or severe symptoms may require the cautious use of atypical antipsychotics. Antidepressants may be beneficial in the appropriate setting. Unfortunately, current therapies for hallucinations offer only limited benefits and future research efforts are desperately required to improve the management of these challenging symptoms.

Visual hallucinations in psychiatric, neurologic, and ophthalmologic disease

PURPOSE OF REVIEW

Recent studies have increased our understanding of the biochemical and structural bases of visual hallucinations in patients with a variety of underlying causes.

RECENT FINDINGS

Visual hallucinations may be related to disruption of functional connectivity networks, with underlying biochemical dysfunction such as decreased in cholinergic activity. Structural abnormalities in primary and higher order visual processing areas also have been found in patients with visual hallucinations. The occurrence of visual hallucinations after vision loss, the Charles Bonnet syndrome, may have more functional similarity to psychiatric and neurodegenerative causes than previously suspected despite retained insight into the unreal nature of the phenomena.

SUMMARY

Visual hallucinations are common, and patients may not report them if specific inquiries are not made. Presence or absence of hallucinations may be of diagnostic and therapeutic importance, especially in patients with neurodegenerative conditions that have overlapping features. Treatment of visual hallucinations remains challenging and must be tailored to each patient based on the underlying cause and comorbid conditions.

Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management

Visual hallucinations are common in older people and are especially associated with ophthalmological and neurological disorders, including dementia and Parkinson's disease. Uncertainties remain whether there is a single underlying mechanism for visual hallucinations or they have different disease-dependent causes. However, irrespective of mechanism, visual hallucinations are difficult to treat. The National Institute for Health Research (NIHR) funded a research programme to investigate visual hallucinations in the key and high burden areas of eye disease, dementia and Parkinson's disease, culminating in a workshop to develop a unified framework for their clinical management. Here we summarise the evidence base, current practice and consensus guidelines that emerged from the workshop.Irrespective of clinical condition, case ascertainment strategies are required to overcome reporting stigma. Once hallucinations are identified, physical, cognitive and ophthalmological health should be reviewed, with education and self-help techniques provided. Not all hallucinations require intervention but for those that are clinically significant, current evidence supports pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. A broad treatment perspective is needed, including carer support. Despite their frequency and clinical significance, there is a paucity of randomised, placebo-controlled clinical trial evidence where the primary outcome is an improvement in visual hallucinations. Key areas for future research include the development of valid and reliable assessment tools for use in mechanistic studies and clinical trials, transdiagnostic studies of shared and distinct mechanisms and when and how to treat visual hallucinations.

Neuropsychiatric aspects of Parkinson disease psychopharmacology: Insights from circuit dynamics

Parkinson disease (PD) is a neurodegenerative disorder with a complex pathophysiology characterized by the progressive loss of dopaminergic neurons within the substantia nigra. Persons with PD experience several motoric and neuropsychiatric symptoms. Neuropsychiatric features of PD include depression, anxiety, psychosis, impulse control disorders, and apathy. In this chapter, we will utilize the National Institutes of Mental Health Research Domain Criteria (RDoC) to frame and integrate observations from two prevailing disease constructions: neurotransmitter anomalies and circuit physiology. When there is available evidence, we posit how unified translational observations may have clinical relevance and postulate importance outside of PD. Finally, we review the limited evidence available for pharmacologic management of these symptoms.

Visual hallucinations in Alzheimer's disease do not seem to be associated with chronic hypoperfusion of to visual processing areas V2 and V3 but may be associated with reduced cholinergic input to these areas

Background

Up to 20% of patients with AD experience hallucinations. The pathological substrate is not known. Visual hallucinations (VH) are more common in dementia with Lewy bodies (DLB). In autopsy studies, up to 60% of patients with AD have concomitant Lewy body pathology. Decreased perfusion of the occipital lobe has been implicated in DLB patients with VH, and post-mortem studies point to both decreased cholinergic activity and reduced oxygenation of the occipital cortex in DLB.

Methods

We used biochemical methods to assess microvessel density (level of von Willebrand factor, a marker of endothelial cell content), ante-mortem oxygenation (vascular endothelial growth factor, a marker of tissue hypoxia; myelin-associated glycoprotein to proteolipid protein-1 ratio, a measure of tissue oxygenation relative to metabolic demand), cholinergic innervation (acetylcholinesterase and choline acetyltransferase), butyrylcholinesterase and insoluble α-synuclein content in the BA18 and BA19 occipital cortex obtained post-mortem from 23 AD patients who had experienced visual hallucinations, 19 AD patients without hallucinations, 19 DLB patients, and 36 controls. The cohorts were matched for age, gender and post-mortem interval.

Results

There was no evidence of reduced microvessel density, hypoperfusion or reduction in ChAT activity in AD with visual hallucinations. Acetylcholinesterase activity was reduced in both BA18 and BA19, in all 3 dementia groups, and the concentration was also reduced in BA19 in the DLB and AD without visual hallucinations groups. Insoluble α-synuclein was raised in the DLB group in both areas but not in AD either with or without visual hallucinations.

Conclusions

Our results suggest that visual hallucinations in AD are associated with cholinergic denervation rather than chronic hypoperfusion or α-synuclein accumulation in visual processing areas of the occipital cortex.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0519-7) contains supplementary material, which is available to authorized users.

Review: Clinical, neuropathological and genetic features of Lewy body dementias

Lewy body dementias are the second most common neurodegenerative dementias after Alzheimer's disease and include dementia with Lewy bodies and Parkinson's disease dementia. They share similar clinical and neuropathological features but differ in the time of dementia and parkinsonism onset. Although Lewy bodies are their main pathological hallmark, several studies have shown the emerging importance of Alzheimer's disease pathology. Clinical amyloid-β imaging using Pittsburgh Compound B (PiB) supports neuropathological studies which found that amyloid-β pathology is more common in dementia with Lewy bodies than in Parkinson's disease dementia. Nevertheless, other co-occurring pathologies, such as cerebral amyloid angiopathy, TDP-43 pathology and synaptic pathology may also influence the development of neurodegeneration and dementia. Recent genetic studies demonstrated an important role of APOE genotype and other genes such as GBA and SNCA which seem to be involved in the pathophysiology of Lewy body dementias. The aim of this article is to review the main clinical, neuropathological and genetic aspects of dementia with Lewy bodies and Parkinson's disease dementia. This is particularly relevant as future management for these two conditions may differ.

Current treatment of behavioral and cognitive symptoms of Parkinson's disease

Cognitive and behavioral symptoms are common in Parkinson's disease, may occur even in the prodromal stages of the disease, worsen with disease progression, and surpass motor symptoms as the major factors affecting patient quality of life and caregiver burden. The symptoms may be caused by the disease pathology or they may represent adverse effects of treatment, or both etiological factors may contribute. Although many of these symptoms are related to dopaminergic dysfunction or dopaminergic medication, other neurotransmitters are involved as well. Behavioral symptoms including impulse control disorders, apathy, psychosis, as well as mild cognitive impairment and dementia are reviewed with a special focus on current treatment approaches.

Advances in Management of Psychosis in Neurodegenerative Diseases

PURPOSE OF THE REVIEW

Psychosis is broadly defined as a disengagement from reality. It describes syndromes that impair both thought content and thought process. Psychosis negatively impacts an individual's quality of life, in addition to the families caring for them. Psychosis with different types of hallucinations and delusions occurs in the context of delirium. Neuropsychiatric symptoms (NPS) are almost universal in the course of common neurodegenerative disorders (NDD) like Alzheimer's disease (AD) or Parkinson's disease (PD). In this paper, the authors took an effort to characterize AD and PD psychosis with a special focus on the most diagnostically reliable features. Effectiveness and limitations of pharmacological interventions are discussed.

RECENT FINDINGS

Consensus diagnostic criteria have evolved for psychosis secondary to AD as well as psychosis in PD. Psychotropic medications can be effective in the treatment of NPS in NDD; however, clinicians must be mindful of the side effects. There is a consensus on benefit of initiating any acetylcholinesterase inhibitor (ACHI: donepezil, rivastigmine, and galantamine) as a first line of treatment for psychosis in AD, as it may reduce and/or avoid the need for the use antipsychotics. Pimavanserin, a selective-serotonin inverse agonist that preferentially targets 5-HT2A receptors, while avoiding activity at dopamine and other receptors commonly targeted by antipsychotics had recently been approved by FDA to treat hallucinations and delusions in PD. Quetiapine is widely prescribed for the treatment of psychosis in different NDD, but the data remains equivocal. Psychosis with different types of hallucinations and delusions may occur in the context of delirium and is almost universal as a neuropsychiatric symptom in the course of PD and AD. Currently, pimavanserin remains the only pharmacologic agent approved for treatment of psychosis in PD. In cases of other NPS in other than Parkinson's diseases, atypical antipsychotics are commonly used off-label. More research is greatly needed to advance this field and address NPS especially psychosis in geriatric population.

Amyloid-β and Parkinson's disease

Parkinson's disease (PD) is the second commonest neurodegenerative disorder in the world with a rising prevalence. The pathophysiology is multifactorial but aggregation of misfolded α-synuclein is considered to be a key underpinning mechanism. Amyloid-β (Aβ) and tau deposition are also comorbid associations and especially Aβ deposition is associated with cognitive decline in PD. Some existing evidence suggests that low cerebrospinal fluid (CSF) Aβ₄₂ is predictive of future cognitive impairment in PD. Recent studies also show that CSF Aβ is associated with the postural instability and gait difficulties (PIGD) or the newly proposed cholinergic subtype of PD, a possible risk factor for cognitive decline in PD. The glial-lymphatic system, responsible for convective solute clearance driven by active fluid transport through aquaporin-4 water channels, may be implicated in brain amyloid deposition. A better understanding of the role of this system and more specifically the role of Aβ in PD symptomatology, could introduce new treatment and repurposing drug-based strategies. For instance, apomorphine infusion has been shown to promote the degradation of Aβ in rodent models. This is further supported in a post-mortem study in PD patients although clinical implications are unclear. In this review, we address the clinical implication of cerebral Aβ deposition in PD and elaborate on its metabolism, its role in cognition and motor function/gait, and finally assess the potential effect of apomorphine on Aβ deposition in PD.

Assessment and Management of Neuropsychiatric Symptoms in Parkinson's Disease

Neuropsychiatric symptoms are highly prevalent in Parkinson's disease and associated with decreased quality of life and adverse health outcomes. In this review, the assessment and management of common neuropsychiatric symptoms are discussed: depression, anxiety, psychosis, cognitive impairment, dementia and apathy. Validated assessment scales are now available for the majority of symptoms. Balancing dopaminergic therapy plays an important role in their management as increasing doses of dopaminergic agents might address depression and anxiety related to 'off' phases, non-motor fluctuations and apathy, while dose reduction might alleviate psychotic symptoms. More targeted treatment is possible through medications utilising different pathways. Although efficacy profiles of individual agents require further exploration, antidepressants as a drug class have shown utility in depression and anxiety in Parkinson's disease. Psychological therapies, especially cognitive behavioural approaches, are effective. Pimavanserin allows the treatment of psychosis in Parkinson's disease without directly affecting the dopaminergic and cholinergic system. The cholinergic system is currently the only target in Parkinson's disease dementia, and antagonists of this system, as are many psychotropic drugs, need to be used with caution. Management of apathy largely relies on non-pharmacological strategies adapted from dementia care, with antidepressants being ineffective and the role of stimulant therapy needing further evaluation.

Gender and Pathology-Specific Effect of Apolipoprotein E Genotype on Psychosis in Alzheimer's Disease

BACKGROUND

Symptoms of psychosis is one of the common clinical manifestations of Alzheimer's disease (AD). However, the pathophysiology behind psychosis is unknown.

OBJECTIVE

The aim of the present study was to explore the relationship between Apolipoprotein E (APOE) genotype, Lewy body pathology, and psychosis in AD.

METHOD

The data was obtained from the National Alzheimer's disease Coordinating Centre (NACC), using the Uniform Data Set and the Neuropathology Data Set. Subjects with frequent neuritic plaque on CERAD, and Braak Stage of V or VI, corresponding to high probability of AD based on the NIA-AA Regan criteria were included in the analysis.

RESULTS

Subjects with two copies of ε4 alleles were significantly more likely to develop psychosis, both delusions and/or hallucinations, during the course of their illness. This association was gender-specific, only reaching significance in females. Our findings further showed that presence of two copies of ε4 allele was positively associated with the formation of Lewy bodies. Only in females with Lewy bodies was the effect of two copies of ε4 allele significant, reaching an odd ratio of 4.5.

CONCLUSION

The APOE ε4 allele has a female-specific effect in inducing psychosis in AD through the formation of Lewy bodies.

Parkinson's disease psychosis: presentation, diagnosis and management

Parkinson's disease is a neurodegenerative disorder characterized by motor and nonmotor symptoms. Psychosis is a common feature of Parkinson's disease. Parkinson's disease psychosis (PDP) encompasses minor phenomena (illusions, passage hallucinations and presence hallucinations), visual and nonvisual hallucinations and delusions. PDP is associated with reduced function and quality of life. The initial management approach should focus on identification and treatment of any contributory medical factors, reduction or discontinuation of medications with potential to induce or worsen psychosis, nonpharmacological strategies and consideration of acetylcholinesterase inhibitor treatment in the setting of dementia. Pimavanserin, quetiapine and clozapine may all be considered for use in PDP. In this review, we discuss the presentation, diagnosis and management of PDP.

Neuropathology of Nonmotor Symptoms of Parkinson's Disease

Parkinson's disease (PD), a multiorgan neurodegenerative disorder associated with α-synuclein deposits throughout the nervous system and many organs, is clinically characterized by motor and nonmotor features, many of the latter antedating motor dysfunctions by 20 or more years. The causes of the nonmotor manifestations such as olfactory, autonomic, sensory, neuropsychiatric, visuospatial, sleep, and other disorders are unlikely to be related to single lesions. They are mediated by the involvement of both dopaminergic and nondopaminergic systems, and diverse structures outside the nigrostriatal system that is mainly responsible for the motor features of PD. The nonmotor alterations appear in early/prodromal stages of the disease and its further progression, suggesting a topographical and chronological spread of the lesions. This lends further support for the notion that PD is a multiorgan proteinopathy, although the exact relationship between presymptomatic and later developing nonmotor features of PD and neuropathology awaits further elucidation.

Psychosis in Parkinson's Disease: Epidemiology, Pathophysiology, and Management

Psychotic symptoms are common in Parkinson's disease (PD) and are associated with poorer quality of life and increased caregiver burden. PD psychosis is correlated with several factors, such as more advanced disease, cognitive impairment, depression, and sleep disorders. The underlying causes of psychosis in PD thus involve a complex interplay between exogenous (e.g., drugs, intercurrent illnesses) and endogenous (e.g., PD disease pathology) factors. Current theories of the pathophysiology of PD psychosis have come from several neuropathological and neuroimaging studies that implicate pathways involving visual processing and executive function, including temporo-limbic structures and neocortical gray matter with altered neurotransmitter functioning (e.g., dopamine, serotonin, and acetylcholine). Treatment of PD psychosis requires a step-wise process, including initial careful investigation of treatable triggering conditions and a comprehensive evaluation with adjustment of PD medications and/or initiation of specific antipsychotic therapies. Clozapine remains the only recommended drug for the treatment of PD psychosis; however, because of regular blood monitoring, quetiapine is usually first-line therapy, although less efficacious. Emerging studies have focused on agents involving other neurotransmitters, including the serotonin 5-HT2A receptor inverse agonist pimavanserin, cholinesterase inhibitors, and antidepressants and anxiolytics.

Risk factors for early psychosis in PD: insights from the Parkinson's Progression Markers Initiative

BACKGROUND

Parkinson's Disease (PD) psychosis refers to the spectrum of illusions, formed hallucinations and delusions that occur in PD. Visual hallucinations and illusions are thought to be caused by specific cognitive and higher visual function deficits and patients who develop such symptoms early in the disease course have greater rates of cognitive decline and progression to dementia. To date, no studies have investigated whether such deficits are found prior to the onset of PD psychosis.

METHOD

Here we compare baseline cognitive, biomarker (structural imaging and cerebrospinal fluid) and other PD psychosis risk factor data in patients who go on to develop illusions or hallucinations within 3-4 years of follow-up in the Parkinson's Progression Markers Initiative cohort of newly diagnosed PD.

RESULTS

Of n=423 patients with PD, n=115 (27%) reported predominantly illusions with the median time of onset at 19.5 months follow-up. At study entry these patients had reduced CSF amyloid Aß1-42, lower olfaction scores, higher depression scores and increased REM sleep behaviour disorder symptoms compared to patients without early onset PD psychosis but no differences in cognitive, higher visual or structural imaging measures. A subset of patients with early onset formed hallucinations (n=21) had reduced higher visual function at baseline, cortical thinning in parietal, occipital and frontal cortex and reduced hippocampal volume.

CONCLUSIONS

The findings suggest early onset illusions and formed hallucinations are linked to amyloid pathology in PD and point to a difference in the underlying pathophysiological mechanism of illusions and formed hallucinations, with implications for their respective links to future cognitive decline.

The psychosis spectrum in Parkinson disease

In 2007, the clinical and research profile of illusions, hallucinations, delusions and related symptoms in Parkinson disease (PD) was raised with the publication of a consensus definition of PD psychosis. Symptoms that were previously deemed benign and clinically insignificant were incorporated into a continuum of severity, leading to the rapid expansion of literature focusing on clinical aspects, mechanisms and treatment. Here, we review this literature and the evolving view of PD psychosis. Key topics include the prospective risk of dementia in individuals with PD psychosis, and the causal and modifying effects of PD medication. We discuss recent developments, including recognition of an increase in the prevalence of psychosis with disease duration, addition of new visual symptoms to the psychosis continuum, and identification of frontal executive, visual perceptual and memory dysfunction at different disease stages. In addition, we highlight novel risk factors - for example, autonomic dysfunction - that have emerged from prospective studies, structural MRI evidence of frontal, parietal, occipital and hippocampal involvement, and approval of pimavanserin for the treatment of PD psychosis. The accumulating evidence raises novel questions and directions for future research to explore the clinical management and biomarker potential of PD psychosis.

Pathology of behavior in PD: What is known and what is not?

Abnormal behavior in Parkinson's disease (PD) stems from a complex orchestration of impaired neural networks that result from PD-related neurodegeneration across multiple levels. Typically, cellular and tissue abnormalities generate neurochemical changes and disrupt specific regions of the brain, in turn creating impaired neural circuits and dysfunctional global networks. The objective of this chapter is to provide an overview of the array of pathological changes that have been linked to different behavioral symptoms of PD such as depression, anxiety, apathy, fatigue, impulse control disorders, psychosis, sleep disorders and dementia.

Lewy Bodies, Vascular Risk Factors, and Subcortical Arteriosclerotic Leukoencephalopathy, but not Alzheimer Pathology, are Associated with Development of Psychosis in Alzheimer's Disease

BACKGROUND

The neuropathological correlates of psychosis in Alzheimer's disease (AD) is unclear, with some studies reporting a correlation between psychosis and increased AD pathology while others have found no association.

OBJECTIVE

To determine the demographic, clinical, and neuropathological features associated with psychotic symptoms in clinically attributed and neuropathologically proven AD.

METHOD

We separately reviewed two overlapping groups of clinically diagnosed (cAD) AD patients with neuropathology data and neuropathologically definite (npAD) cases (regardless of clinical diagnosis) from the NACC database, and explored the relationships between psychosis and clinical variables, neuropathologic correlates, and vascular risk factors. Delusions and hallucinations, defined according to the NPI-Q, were analyzed separately.

RESULTS

1,073 subjects in the database fulfilled our criteria (890 cAD and 728 npAD patients). 34% of cAD and 37% of npAD had psychotic symptoms during their illness. Hallucinations were associated with greater cognitive and functional impairments on the MMSE and CDR, while delusional patients showed less impairment on CDR, consistent across cAD and npAD groups. Burden of AD pathology appears to relate to presence of psychotic symptoms in the clinical AD group, but this result is not confirmed in the neuropathologically confirmed group suggesting the findings in the clinical group were due to misdiagnosis of AD. Lewy body pathology, subcortical arteriosclerotic leukoencephalopathy, and vascular risk factors, including a history of hypertension and diabetes, were associated with the development of psychosis.

METHOD

Vascular and Lewy body pathologies and vascular risk factors are important modifiers of the risk of psychosis in AD.

Parkinson's disease psychosis as a serotonin-dopamine imbalance syndrome

Parkinson's disease psychosis (PDP) is theoretically a serotonin-dopamine imbalance syndrome due to disruption of the normal balance between the serotonergic and dopaminergic neurotransmitter systems in key brain circuits.

Mechanism of action of pimavanserin in Parkinson's disease psychosis: targeting serotonin 5HT2A and 5HT2C receptors

Pimavanserin, a novel agent approved for the treatment of Parkinson's disease psychosis, has potent actions as an antagonist/inverse agonist at serotonin 5HT2A receptors and less potent antagonist/inverse agonist actions at 5HT2C receptors.

Clinicopathological correlation of psychosis and brain vascular changes in Alzheimer's disease

Psychosis is common in Alzheimer’s disease (AD). However, studies on neuropathology in vascular etiology contributing to psychosis in AD is lacking to date. The aim of this study was to investigate neuropathological vascular related changes in Alzheimer’s disease with psychosis. Data of patients with AD from the National Alzheimer’s Coordinating Center between 2005 to September 2013 was accessed and reviewed. Presence of psychosis was determined based on Neuropsychiatric Inventory Questionnaire taken from the last visit within one year prior to death, and patients were divided into psychosis positive and negative group. Comparison of clinical details and neuropathological vascular changes between the groups was performed using Wilcoxon rank sum test and Chi-square/ Fisher’s exact test. Significant variables were further included in a multivariate logistic model. Overall, 145 patients was included. Of these, 50 patients were psychosis positive. Presence of one or more cortical microinfarcts and moderate to severe arteriosclerosis was found to be positively associated with psychosis. Our results suggest vascular changes correlate with psychosis in Alzheimer’s disease.

Significance of visual hallucinations and cerebral hypometabolism in the risk of dementia in Parkinson's disease patients with mild cognitive impairment

INTRODUCTION

Mild cognitive impairment (MCI) and visual hallucinations (VH) are common co-morbidities and risk factors for dementia in Parkinson's disease (PD). The relative value of each of them in the progression to dementia is unknown. We investigated cognitive impairment and cerebral hypometabolism in PD-MCI patients with VH (VH-positive) and without (VH-negative).

METHODS

Twenty-one PD-MCI patients (12 VH-negative, nine VH-positive) and 19 controls were studied using a comprehensive neuropsychological battery and [18F]-Fluorodeoxyglucose positron emission tomography (FDG-PET). The neuropsychological assessment was repeated after 30 months. Regional FDG uptake was analyzed using statistical parametric mapping.

RESULTS

VH-positive patients had lower FDG uptake bilaterally in the occipital, and parietal cortex, right temporal lobe and in the left cingulum compared with VH-negative patients. The two groups showed no significant differences in clinical characteristics and cognitive status at baseline. After 30 months of follow-up, three (25%) and four (50%) of the VH-negative and VH-positive patients, respectively, had progressed to dementia.

CONCLUSION

Even in the absence of significant cognitive differences, PD-MCI patients with VH exhibit more severe cerebral hypometabolism and had a higher rate of progression to dementia than VH-negative patients, supporting the importance of VH and cerebral hypometabolism in establishing the risk of dementia in PD-MCI.