Topography, extent, and clinical relevance of neurochemical deficits in dementia of Lewy body type, Parkinson's disease, and Alzheimer's disease

Cholinesterase Inhibitors for Treatment of Psychotic Symptoms in Alzheimer Disease and Parkinson Disease: A Meta-analysis

Importance

Psychotic symptoms greatly increase the burden of disease for people with neurodegenerative disorders and their caregivers. Cholinesterase inhibitors (ChEIs) may be effective treatment for psychotic symptoms in these disorders. Previous trials only evaluated neuropsychiatric symptoms as a secondary and an overall outcome, potentially blurring the outcomes noted with ChEI use specifically for psychotic symptoms.

Objective

To quantitatively assess the use of ChEIs for treatment of individual neuropsychiatric symptoms, specifically hallucinations and delusions, in patients with Alzheimer disease (AD), Parkinson disease (PD), and dementia with Lewy bodies (DLB).

Data Sources

A systematic search was performed in PubMed (MEDLINE), Embase, and PsychInfo, without year restrictions. Additional eligible studies were retrieved from reference lists. The final search cutoff date was April 21, 2022.

Study Selection

Studies were selected if they presented the results of placebo-controlled randomized clinical trials, including at least 1 donepezil, rivastigmine, or galantamine treatment arm in patients with AD, PD, or DLB; if they applied at least 1 neuropsychiatric measure including hallucinations and/or delusions; and if a full-text version of the study was available in the English language. Study selection was performed and checked by multiple reviewers.

Data Extraction and Synthesis

Original research data were requested on eligible studies. A 2-stage meta-analysis was then performed, using random-effects models. Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed for extracting data and assessing the data quality and validity. Data extraction was checked by a second reviewer.

Main Outcomes and Measures

Primary outcomes were hallucinations and delusions; secondary outcomes included all other individual neuropsychiatric subdomains as well as the total neuropsychiatric score.

Results

In total, 34 eligible randomized clinical trials were selected. Individual participant data on 6649 individuals (3830 [62.6%] women; mean [SD] age, 75.0 [8.2] years) were obtained from 17 trials (AD: n = 12; PD: n = 5; individual participant data were not available for DLB). An association with ChEI treatment was shown in the AD subgroup for delusions (-0.08; 95% CI, -0.14 to -0.03; P = .006) and hallucinations (-0.09; 95% CI, -0.14 to -0.04; P = .003) and in the PD subgroup for delusions (-0.14; 95% CI, -0.26 to -0.01; P = .04) and hallucinations (-0.08, 95% CI -0.13 to -0.03; P = .01).

Conclusions and Relevance

The results of this individual participant data meta-analysis suggest that ChEI treatment improves psychotic symptoms in patients with AD and PD with small effect sizes.

MALDI imaging mass spectrometry: an emerging tool in neurology

Neurological disease and disorders remain a large public health threat. Thus, research to improve early detection and/or develop more effective treatment approaches are necessary. Although there are many common techniques and imaging modalities utilized to study these diseases, existing approaches often require a label which can be costly and time consuming. Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) is a label-free, innovative and emerging technique that produces 2D ion density maps representing the distribution of an analyte(s) across a tissue section in relation to tissue histopathology. One main advantage of MALDI IMS over other imaging modalities is its ability to determine the spatial distribution of hundreds of analytes within a single imaging run, without the need for a label or any a priori knowledge. Within the field of neurology and disease there have been several impactful studies in which MALDI IMS has been utilized to better understand the cellular pathology of the disease and or severity. Furthermore, MALDI IMS has made it possible to map specific classes of analytes to regions of the brain that otherwise may have been lost using more traditional methods. This review will highlight key studies that demonstrate the potential of this technology to elucidate previously unknown phenomenon in neurological disease.

Movement Disorder Emergencies

Acute presentation of new movement disorders and acute decompensation of chronic movement disorders are uncommon but potentially life-threatening. Inadvertent or purposeful overdose of many psychiatric medications can result in acute life-threatening movement disorders including serotonin syndrome, neuroleptic malignant syndrome, and malignant catatonia. Early withdrawal of potentiating medications, treatment with benzodiazepines and other diagnosis-specific drugs, and providing appropriate supportive care including airway and breathing management, hemodynamic stabilization, fluid resuscitation, and renal support including possible hemodialysis are the mainstays of acute management. Many of these conditions require admission to the neurologic intensive care unit.

The Role of EEG in the Diagnosis, Prognosis and Clinical Correlations of Dementia with Lewy Bodies-A Systematic Review

Despite improvements in diagnostic criteria for dementia with Lewy bodies (DLB), the ability to discriminate DLB from Alzheimer’s disease (AD) and other dementias remains suboptimal. Electroencephalography (EEG) is currently a supportive biomarker in the diagnosis of DLB. We performed a systematic review to better clarify the diagnostic and prognostic role of EEG in DLB and define the clinical correlates of various EEG features described in DLB. MEDLINE, EMBASE, and PsycINFO were searched using search strategies for relevant articles up to 6 August 2020. We included 43 studies comparing EEG in DLB with other diagnoses, 42 of them included a comparison of DLB with AD, 10 studies compared DLB with Parkinson’s disease dementia, and 6 studies compared DLB with other dementias. The studies were visual EEG assessment (6), quantitative EEG (35) and event-related potential studies (2). The most consistent observation was the slowing of the dominant EEG rhythm (<8 Hz) assessed visually or through quantitative EEG, which was observed in ~90% of patients with DLB and only ~10% of patients with AD. Other findings based on qualitative rating, spectral power analyses, connectivity, microstate and machine learning algorithms were largely heterogenous due to differences in study design, EEG acquisition, preprocessing and analysis. EEG protocols should be standardized to allow replication and validation of promising EEG features as potential biomarkers in DLB.

The Energy Homeostasis Principle: Neuronal Energy Regulation Drives Local Network Dynamics Generating Behavior

A major goal of neuroscience is understanding how neurons arrange themselves into neural networks that result in behavior. Most theoretical and experimental efforts have focused on a top-down approach which seeks to identify neuronal correlates of behaviors. This has been accomplished by effectively mapping specific behaviors to distinct neural patterns, or by creating computational models that produce a desired behavioral outcome. Nonetheless, these approaches have only implicitly considered the fact that neural tissue, like any other physical system, is subjected to several restrictions and boundaries of operations. Here, we proposed a new, bottom-up conceptual paradigm: The Energy Homeostasis Principle, where the balance between energy income, expenditure, and availability are the key parameters in determining the dynamics of neuronal phenomena found from molecular to behavioral levels. Neurons display high energy consumption relative to other cells, with metabolic consumption of the brain representing 20% of the whole-body oxygen uptake, contrasting with this organ representing only 2% of the body weight. Also, neurons have specialized surrounding tissue providing the necessary energy which, in the case of the brain, is provided by astrocytes. Moreover, and unlike other cell types with high energy demands such as muscle cells, neurons have strict aerobic metabolism. These facts indicate that neurons are highly sensitive to energy limitations, with Gibb's free energy dictating the direction of all cellular metabolic processes. From this activity, the largest energy, by far, is expended by action potentials and post-synaptic potentials; therefore, plasticity can be reinterpreted in terms of their energy context. Consequently, neurons, through their synapses, impose energy demands over post-synaptic neurons in a close loop-manner, modulating the dynamics of local circuits. Subsequently, the energy dynamics end up impacting the homeostatic mechanisms of neuronal networks. Furthermore, local energy management also emerges as a neural population property, where most of the energy expenses are triggered by sensory or other modulatory inputs. Local energy management in neurons may be sufficient to explain the emergence of behavior, enabling the assessment of which properties arise in neural circuits and how. Essentially, the proposal of the Energy Homeostasis Principle is also readily testable for simple neuronal networks.

Deciduous DPSCs Ameliorate MPTP-Mediated Neurotoxicity, Sensorimotor Coordination and Olfactory Function in Parkinsonian Mice

Parkinson's disease (PD) is a neurodegenerative disorder defined by progressive deterioration of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Dental pulp stem cells (DPSCs) have been proposed to replace the degenerated dopaminergic neurons due to its inherent neurogenic and regenerative potential. However, the effective delivery and homing of DPSCs within the lesioned brain has been one of the many obstacles faced in cell-based therapy of neurodegenerative disorders. We hypothesized that DPSCs, delivered intranasally, could circumvent these challenges. In the present study, we investigated the therapeutic efficacy of intranasally administered DPSCs in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. Human deciduous DPSCs were cultured, pre-labelled with PKH 26, and intranasally delivered into PD mice following MPTP treatment. Behavioural analyses were performed to measure olfactory function and sensorimotor coordination, while tyrosine hydroxylase (TH) immunofluorescence was used to evaluate MPTP neurotoxicity in SNpc neurons. Upon intranasal delivery, degenerated TH-positive neurons were ameliorated, while deterioration in behavioural performances was significantly enhanced. Thus, the intranasal approach enriched cell delivery to the brain, optimizing its therapeutic potential through its efficacious delivery and protection against dopaminergic neuron degeneration.

Mesencephalic and extramesencephalic dopaminergic systems in Parkinson's disease

Neurodegeneration of the nigrostriatal dopaminergic system and concurrent dopamine (DA) deficiency in the basal ganglia represent core features of Parkinson's disease (PD). Despite the central role of DA in the pathogenesis of PD, dopaminergic systems outside of the midbrain have not been systematically investigated for Lewy body pathology or neurodegeneration. Dopaminergic neurons show a surprisingly rich neurobiological diversity, suggesting that there is not one general type of dopaminergic neuron, but rather a spectrum of different dopaminergic phenotypes. This heterogeneity on the cellular level could account for the observed differences in susceptibility of the dopaminergic systems to the PD disease process. In this review, we will summarize the long history from the first description of PD to the rationally derived DA replacement therapy, describe the basal neuroanatomical and neuropathological features of the different dopaminergic systems in health and PD, explore how neuroimaging techniques broadened our view of the dysfunctional dopaminergic systems in PD and discuss how dopaminergic replacement therapy ameliorates the classical motor symptoms but simultaneously induces a new set of hyperdopaminergic symptoms.

Precision and False Perceptual Inference

Accurate perceptual inference fundamentally depends upon accurate beliefs about the reliability of sensory data. In this paper, we describe a Bayes optimal and biologically plausible scheme that refines these beliefs through a gradient descent on variational free energy. To illustrate this, we simulate belief updating during visual foraging and show that changes in estimated sensory precision (i.e., confidence in visual data) are highly sensitive to prior beliefs about the contents of a visual scene. In brief, confident prior beliefs induce an increase in estimated precision when consistent with sensory evidence, but a decrease when they conflict. Prior beliefs held with low confidence are rapidly updated to posterior beliefs, determined by sensory data. These induce much smaller changes in beliefs about sensory precision. We argue that pathologies of scene construction may be due to abnormal priors, and show that these can induce a reduction in estimated sensory precision. Having previously associated this precision with cholinergic signaling, we note that several neurodegenerative conditions are associated with visual disturbances and cholinergic deficits; notably, the synucleinopathies. On relating the message passing in our model to the functional anatomy of the ventral visual stream, we find that simulated neuronal loss in temporal lobe regions induces confident, inaccurate, empirical prior beliefs at lower levels in the visual hierarchy. This provides a plausible, if speculative, computational mechanism for the loss of cholinergic signaling and the visual disturbances associated with temporal lobe Lewy body pathology. This may be seen as an illustration of the sorts of hypotheses that may be expressed within this computational framework.

Longitudinal white matter microstructural change in Parkinson's disease

Postmortem studies of Parkinson's disease (PD) suggest that Lewy body pathology accumulates in a predictable topographical sequence, beginning in the olfactory bulb, followed by caudal brainstem, substantia nigra, limbic cortex, and neocortex. Diffusion-weighted imaging (DWI) is sensitive, if not specific, to early disease-related white matter (WM) change in a variety of traumatic and degenerative brain diseases. Although numerous cross-sectional studies have reported DWI differences in cerebral WM in PD, only a few longitudinal studies have investigated whether DWI change exceeds that of normal aging or coincides with regional Lewy body accumulation. This study mapped regional differences in the rate of DWI-based microstructural change between 29 PD patients and 43 age-matched controls over 18 months. Iterative within- and between-subject tensor-based registration was completed on motion- and eddy current-corrected DWI images, then baseline versus follow-up difference maps of fractional anisotropy, mean, radial, and axial diffusivity were analyzed in the Biological Parametric Mapping toolbox for MATLAB. This analysis showed that PD patients had a greater decline in WM integrity in the rostral brainstem, caudal subcortical WM, and cerebellar peduncles, compared with controls. In addition, patients with unilateral clinical signs at baseline experienced a greater rate of WM change over the 18-month study than patients with bilateral signs. These findings suggest that rate of WM microstructural change in PD exceeds that of normal aging and is maximal during early stage disease. In addition, the neuroanatomic locations (rostral brainstem and subcortical WM) of accelerated WM change fit with current theories of topographic disease progression.

Augmented frontal cortex diacylglycerol levels in Parkinson's disease and Lewy Body Disease

Background

Research from our laboratory, and that of other investigators, has demonstrated augmented levels of diacylglycerols (DAG) in the frontal cortex and plasma of subjects with Alzheimer’s disease (AD) and Mild Cognitive Impairment (MCI). We have extended these observations to investigate the frontal cortex of subjects with Parkinson’s disease (PD) and Lewy Body Disease (LBD), with and without coexisting pathologic features of AD.

Methods/Principal findings

Utilizing a high-resolution mass spectrometry analytical platform, we clearly demonstrate that DAG levels are significantly increased in the frontal cortex of subjects with PD, LBD with intermediate neocortical AD neuropathology, and in LBD with established neocortical AD neuropathology. In the case of the PD cohort, increases in cortical DAG levels were detected in cases with no neocortical pathology but were greater in subjects with neocortical pathology. These data suggest that DAG changes occur early in the disease processes and are amplified as cortical dysfunction becomes more established.

Conclusions

These findings suggest that altered DAG synthesis/metabolism is a common feature of neurodegenerative diseases, characterized by proteinopathy, that ultimately result in cognitive deficits. With regard to the mechanism responsible for these biochemical alterations, selective decrements in cortical levels of phosphatidylcholines in LBD and PD suggest that augmented degradation and/or decreased synthesis of these structural glycerophospholipids may contribute to increases in the pool size of free DAGs. The observed augmentation of DAG levels may be phospholipase-driven since neuroinflammation is a consistent feature of all disease cohorts. If this conclusion can be validated it would support utilizing DAG levels as a biomarker of the early disease process and the investigation of early intervention with anti-inflammatory agents.

Management of Psychosis in Parkinson's Disease: Emphasizing Clinical Subtypes and Pathophysiological Mechanisms of the Condition

Investigation into neuropsychiatric symptoms in Parkinson's disease (PD) is sparse and current drug development is mainly focused on the motor aspect of PD. The tight association of psychosis with an impaired quality of life in PD, together with an important underreporting of this comorbid condition, contributes to its actual insufficient assessment and management. Furthermore, the withdrawal from access to readily available treatment interventions is unacceptable and has an impact on PD prognosis. Despite its impact, to date no standardized guidelines to the adequate management of PD psychosis are available and they are therefore highly needed. Readily available knowledge on distinct clinical features as well as early biomarkers of psychosis in PD justifies the potential for its timely diagnosis and for early intervention strategies. Also, its specific characterisation opens up the possibility of further understanding the underlying pathophysiological mechanisms giving rise to more targeted therapeutic developments in the nearer future. A literature review on the most recent knowledge with special focus on specific clinical subtypes and pathophysiological mechanisms will not only contribute to an up to date practical approach of this condition for the health care providers, but furthermore open up new ideas for research in the near future.

N-Phenacylthiazolium Salts as Inhibitors of Cholinesterases

Inhibition of acetylcholinesterase is considered as a promising approach for treatment of neurodegenerative disorders including Alzheimer's disease. In this study, we demonstrated that 5-substituted N-phenacylthiazolium derivatives are capable of inhibiting acetylcholinesterase and butyrylcholinesterase activities with IC50 values in the micromolar range. Some of the new thiazolium-based inhibitiors showed more than 10-fold selectivity for butyrylcholinesterase. Kinetic experiments and molecular docking were performed for understanding the inhibition mechanisms.

The neurobiological basis of cognitive impairment in Parkinson's disease

The recent formalization of clinical criteria for Parkinson's disease with dementia (PDD) codifies many studies on this topic, including those assessing biological correlates. These studies show that the emergence of PDD occurs on the background of severe dopamine deficits with, the main pathological drivers of cognitive decline being a synergistic effect between alpha-synuclein and Alzheimer's disease pathology. The presence of these pathologies correlates with a marked loss of limbic and cortically projecting dopamine, noradrenaline, serotonin, and acetylcholine neurons, although the exact timing of these relationships remains to be determined. Genetic factors, such as triplications in the α-synuclein gene, lead to a clear increased risk of PDD, whereas others, such as parkin mutations, are associated with a reduced risk of PDD. The very recent formalization of clinical criteria for PD with mild cognitive impairment (PD-MCI) allows only speculation on its biological and genetic bases. Critical assessment of animal models shows that chronic low-dose MPTP treatment in primates recapitulates PD-MCI over time, enhancing the current biological concept of PD-MCI as having enhanced dopamine deficiency in frontostriatal pathways as well as involvement of other neurotransmitter systems. Data from other animal models support multiple transmitter involvement in cognitive impairment in PD. Whereas dopamine dysfunction has been highlighted because of its obvious role in PD, the role of the other neurotransmitter systems, neurodegenerative pathologies, and genetic factors in PD-MCI remains to be fully elucidated.

Clinical Trials in Parkinson's Disease Dementia and Dementia with Lewy Bodies

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are pathological overlapping and important causes of dementia for which clinical trials are in their infancy. Cholinesterase inhibitors may be of benefit in DLB and PDD, as suggested by placebo-controlled clinical trials of rivastigmine and donepezil. The anti-psychotic agent clozapine has been of benefit in PD and PDD, but other agents, such as quetiapine, require adequate assessment. Barriers to trials include pathological overlap that can lead to inaccuracies in clinical diagnosis, unavailability of a consensus definition for PDD, unanswered questions regarding natural history and the paucity of validated outcome measures. Motor impairment must be considered in patients with PDD and DLB; conversely, cognitive impairment should be assessed in trials targeting motor impairment in advanced PD. Potential targets for treatment include onset of dementia, cognitive impairment, behavioral impairment, functional decline, falls, nursing home placement, mortality, quality of life and economic impact. Biomarkers including neuroimaging and cerebrospinal fluid markers are not currently established. At present PDD and DLB are distinct entities by definition. Future studies, including clinical trials and biomarker studies, will help to further define the clinical and therapeutic implications of this distinction.

Parkinson disease and exercise

Parkinson disease (PD) is a progressive, neurodegenerative movement disorder. PD was originally attributed to neuronal loss within the substantia nigra pars compacta, and a concomitant loss of dopamine. PD is now thought to be a multisystem disorder that involves not only the dopaminergic system, but other neurotransmitter systems whose role may become more prominent as the disease progresses (189). PD is characterized by four cardinal symptoms, resting tremor, rigidity, bradykinesia, and postural instability, all of which are motor. However, PD also may include any combination of a myriad of nonmotor symptoms (195). Both motor and nonmotor symptoms may impact the ability of those with PD to participate in exercise and/or impact the effects of that exercise on those with PD. This article provides a comprehensive overview of PD, its symptoms and progression, and current treatments for PD. Among these treatments, exercise is currently at the forefront. People with PD retain the ability to participate in many forms of exercise and generally respond to exercise interventions similarly to age-matched subjects without PD. As such, exercise is currently an area receiving substantial research attention as investigators seek interventions that may modify the progression of the disease, perhaps through neuroprotective mechanisms.

Combined duloxetine and benzodiazepine-induced visual hallucinations in prodromal dementia with Lewy bodies

OBJECTIVE

We describe a patient with prodromal dementia with Lewy bodies (DLB) presenting with drug-induced visual hallucinations (VHs).

CASE REPORT

A 78-year-old woman complained of daytime recurrent VHs characterized by seeing her face and arms covered in fur and viewing moustaches on her daughter's face. VHs started a few days after the beginning of a combination therapy with duloxetine and lorazepam and ceased within 24 h after their discontinuation. Nonamnestic mild cognitive impairment with profound visual perception deficits and very mild extrapyramidal signs, with abnormal brain DaTscan single photon emission tomography, were present. Three years later, cognitive and neurological follow-up assessments supported the diagnosis of DLB.

CONCLUSION

Perturbation of cerebral serotonergic tone induced by duloxetine, associated with reduced attentional control due to benzodiazepine use, may be the physiopathological substrate of transient VHs in prodromal DLB.

Dementia with lewy bodies: diagnosis and management for primary care providers

OBJECTIVE

The purpose of this review is to aid primary care providers in distinguishing dementia with Lewy bodies (DLB) from Alzheimer's disease and from Parkinson's disease with dementia. Differentiating these entities has important treatment implications.

DATA SOURCES

A PubMed search was undertaken using the keywords Lewy body dementia, dementia with Lewy bodies, and Lewy body disease. There were no date restrictions. Only articles in the English language were reviewed. References of selected articles were reviewed for additional sources.

DATA SELECTION AND EXTRACTION

Initially, 2,967 articles were retrieved. All 3 authors participated in data selection and extraction. Articles were further selected for content specific to epidemiology, clinical presentation, diagnostic studies, treatment, and prognosis. For articles with repetitive information, the most current article was used. This resulted in a total of 62 articles included in the review.

DATA SYNTHESIS

Dementia with Lewy bodies is the second leading cause of dementia after Alzheimer's disease. The core symptoms of DLB, including cognitive fluctuations, visual hallucinations, and parkinsonism, may not always be present as a triad, and clinicians may be unaware of associated symptoms. Thus, this diagnosis is frequently missed by primary care providers. Often, DLB is misdiagnosed as Alzheimer's disease, Parkinson's disease, or a primary psychiatric illness. Treatments for DLB include cholinesterase inhibitors and N-methyl-D-aspartate antagonists. Antipsychotics should be avoided or used with caution.

CONCLUSIONS

Dementia with Lewy bodies is an often missed diagnosis. Symptoms are often attributed to other disorders. A high clinical suspicion is helpful in accurate diagnosis, and presence of any of the core symptoms should initiate clinical suspicion of DLB. Distinguishing DLB from other disorders has important treatment implications.

Hallucinations in neurodegenerative diseases

Patients with neurodegenerative disease frequently experience hallucinations and illusionary perceptions. As early symptoms, hallucinations may even have diagnostic relevance (i.e., for the diagnosis of Lewy Body Dementia). In the later course of the disease, hallucinations may appear as characteristic symptoms and often constitute a particular challenge for therapeutic endeavors. Here, the distinction of disease-inherent hallucinations from medication-associated perceptual disturbances is particularly relevant. Synucleinopathies and tauopathies have different risk profiles for hallucinations. In synucleinopathies hallucinations are much more frequent and phenomenology is characterized by visual, short-lived hallucinations, with insight preserved for a long time. A “double hit” theory proposes that dysfunctionality of both associative visual areas and changes of limbic areas or the ventral striatum are required. In contrast, in tauopathies the hallucinations are more rare and mostly embedded in confusional states with agitation and with poorly defined or rapidly changing paranoia. The occurrence of hallucinations has even been proposed as an exclusion criterion for tauopathies with Parkinsonian features such as progressive supranuclear palsy. To date, treatment remains largely empirical, except the use of clozapine and cholinesterase inhibitors in synucleinopathies, which is evidence-based. The risk of increased neuroleptic sensitivity further restricts the treatment options in patients with Lewy Body Dementia. Coping Strategies and improvement of visual acuity and sleep quality may be useful therapeutic complements.

Neurochemistry and the non-motor aspects of PD

Parkinson disease (PD) is a systemic disease with variegated non-motor deficits and neurological symptoms, including impaired olfaction, autonomic failure, cognitive impairment and psychiatric symptoms, in addition to the classical motor symptoms. Many non-motor symptoms appear before or in parallel with motor deficits and then worsen with disease progression. Although there is a relationship, albeit not causal, between motor symptoms and the presence of Lewy bodies (LBs) and neurites filled with abnormal α-synuclein, other neurological alterations are independent of the amount of α-synuclein inclusions in neurons and neurites, thereby indicating that different mechanisms probably converge in the degenerative process. This may apply to complex alterations interfering with olfactory and autonomic nervous systemfunctions, emotions, sleep regulation, and behavioral, cognitive and mental performance. Involvement of the cerebral cortex leading to impaired behavior and cognition is related to several convergent altered factors including: a. dopaminergic, noradrenergic, serotoninergic and cholinergic cortical innervation; b. synapses; c. cortical metabolism; d. mitochondrial function and energy production; e. oxidative damage; f. transcription; g. protein expression; h. lipid composition; and i. ubiquitin–proteasome system and autophagy, among others. This complex situation indicates that multiple subcellular failure in selected cell populations is difficult to reconcilewith a reductionistic scenario of a single causative cascade of events leading to non-motor symptoms in PD. Furthermore, these alterationsmay appear at early stages of the disease and may precede the appearance of substantial irreversible cell loss by years. These observations have important implications in the design of therapeutic approaches geared to prevention and treatment of PD.

Dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia in older people, accounting for 10% to 15% of all cases, it occupies part of a spectrum that includes Parkinson's disease and primary autonomic failure. All these diseases share a neuritic pathology based upon abnormal aggregation of the synaptic protein α-synuciein. It is important to identify DLB patients accurately because they have specific symptoms, impairments, and functional disabilities thai differ from other common dementia syndromes such as Alzheimer's disease, vascular cognitive impairment, and frontotemporal dementia. Clinical diagnostic criteria for DLB have been validated against autopsy, but fail to detect a substantial minority of cases with atypical presentations that are often due to the presence of mixed pathology. DLB patients frequently have severe neuroleptic sensitivity reactions, which are associated with significantly increased morbidity and mortality. Cholinesterase inhibitor treatment is usually well tolerated and substantially improves cognitive and neuropsychiatrie symptoms. Although virtually unrecognized 20 years ago, DLB could within this decade become one of the most treatable neurodegenerative disorders of late life.

Agitation and psychosis associated with dementia with lewy bodies exacerbated by modafinil use

Dementia with Lewy bodies (DLB) is commonly associated with excessive daytime somnolence (EDS). Modafinil is a wakefulness-promoting agent that is considered to have limited interaction with the dopaminergic system. As individuals with DLB are predisposed to psychotic symptoms that might be exacerbated by dopaminergic stimulation, modafinil is considered to be an attractive option for the treatment of EDS in DLB. We describe 2 cases in which administration of modafinil exacerbated agitation and hallucinations in DLB, and we also review data that may explain the mechanisms underlying this effect. In both cases, psychotic symptoms emerged concomitantly with modafinil administration and remitted following its discontinuation. Although definitive data regarding the benefits and adverse effects of modafinil for the treatment of EDS in DLB await controlled prospective randomized studies, our observations warrant caution regarding its use in this context.

Neuropathology and neurochemistry of nonmotor symptoms in Parkinson's disease

Parkinson disease (PD) is no longer considered a complex motor disorder characterized by Parkinsonism but rather a systemic disease with variegated non-motor deficits and neurological symptoms, including impaired olfaction, autonomic failure, cognitive impairment, and psychiatric symptoms. Many of these alterations appear before or in parallel with motor deficits and then worsen with disease progression. Although there is a close relation between motor symptoms and the presence of Lewy bodies (LBs) and neurites filled with abnormal α-synuclein, other neurological alterations are independent of the amount of α-synuclein inclusions in neurons and neurites, thereby indicating that different mechanisms probably converge in the degenerative process. Involvement of the cerebral cortex that may lead to altered behaviour and cognition are related to several convergent factors such as (a) abnormal α-synuclein and other proteins at the synapses, rather than LBs and neurites, (b) impaired dopaminergic, noradrenergic, cholinergic and serotoninergic cortical innervation, and (c) altered neuronal function resulting from reduced energy production and increased energy demands. These alterations appear at early stages of the disease and may precede by years the appearance of cell loss and cortical atrophy.

Molecular imaging and the neuropathologies of Parkinson's disease

The main motor symptoms of Parkinson's disease (PD) are linked to degeneration of the nigrostriatal dopamine (DA) fibers, especially those innervating the putamen. This degeneration can be assessed in molecular imaging studies with presynaptic tracers such as [(18)F]-fluoro-L-DOPA (FDOPA) and ligands for DA transporter ligands. However, the pathologies of PD are by no means limited to nigrostriatal loss. Results of post mortem and molecular imaging studies reveal parallel degenerations of cortical noradrenaline (NA) and serotonin (5-HT) innervations, which may contribute to affective and cognitive changes of PD. Especially in advanced PD, cognitive impairment can come to resemble that seen in Alzheimer's dementia, as can the degeneration of acetylcholine innervations arising in the basal forebrain. The density of striatal DA D(2) receptors increases in early untreated PD, consistent with denervation upregulation, but there is an accelerated rate of DA receptor loss as the disease advances. Animal studies and post mortem investigations reveal changes in brain opioid peptide systems, but these are poorly documented in imaging studies of PD. Relatively minor changes in the binding sites for GABA are reported in cortex and striatum of PD patients. There remains some controversy about the expression of the 18 kDa translocator protein (TSPO) in activated microglia as an indicator of an active inflammatory component of neurodegeneration in PD. A wide variety of autonomic disturbances contribute to the clinical syndrome of PD; the degeneration of myocardial sympathetic innervation can be revealed in SPECT studies of PD patients with autonomic failure. Considerable emphasis has been placed on investigations of cerebral blood flow and energy metabolism in PD. Due to the high variance of these physiological estimates, researchers have often employed normalization procedures for the sensitive detection of perturbations in relatively small patient groups. However, a widely used normalization to the global mean must be used with caution, as it can result in spurious findings of relative hypermetabolic changes in subcortical structures. A meta-analysis of the quantitative studies to date shows that there is in fact widespread hypometabolism and cerebral blood flow in the cerebral cortex, especially in frontal cortex and parietal association areas. These changes can bias the use of global mean normalization, and probably represent the pathophysiological basis of the cognitive impairment of PD.

Cell type specific sequestration of choline acetyltransferase and tyrosine hydroxylase within Lewy bodies

Lewy bodies (LBs), the pathological hallmark of Lewy body disease (LBD), contain α-synuclein, as well as other proteins. In this study, we examined the relationship of α-synuclein to two rate-limiting enzymes in neurotransmitter synthesis, tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT). Double-labeling immunohistochemistry for α-synuclein and TH revealed TH immunoreactivity within LBs in catecholaminergic neurons in the substantia nigra and locus coeruleus, but not within LBs in cholinergic neurons in the pedunculopontine nucleus and nucleus basalis of Meynert. In contrast, ChAT immunoreactivity within LBs was detected in cholinergic, but not within LBs in catecholaminergic neurons. The amygdala was devoid of TH and ChAT positive LBs, although a few Lewy neurites contained ChAT immunoreactivity. Further analysis revealed two distinct patterns of neurotransmitter immunoreactivity within LBs. One pattern had diffuse co-localization of TH or ChAT with α-synuclein as in cortical-type LBs, while the other had intense TH or ChAT immunoreactivity in the LB core surrounded by a peripheral rim of α-synuclein as in brainstem-type LBs. Levels of both TH and ChAT were higher in brainstem-type LBs than in the cytoplasm of the same neuron or in neurons from the same case devoid of LBs. Given the fact that LB-containing neurons have decreases in cytoplasmic TH and ChAT immunoreactivity, these results suggest LBs may disrupt cholinergic and catecholaminergic neurotransmitter production by sequestration of the rate-limiting enzymes for acetylcholine and catecholamine synthesis.

Emerging hypotheses regarding the influences of butyrylcholinesterase-K variant, APOE epsilon 4, and hyperhomocysteinemia in neurodegenerative dementias

Non-enzymatic functions of butyrylcholinesterase (BuChE) include prevention of the aggregation of amyloid-beta peptide (A beta) in a concentration-dependent manner. This is mediated by the C-terminus of the protein, distal from the enzymatic site. The BuChE-K variant polymorphism lowers expression of BuChE protein and/or alters C-terminal activity. In combination with factors that increase production or reduce elimination of A beta, and/or increase susceptibility to A beta toxicity - such as the apolipoprotein E (APOE) epsilon 4 allele and/or hyperhomocysteinemia - BuChE-K may accelerate cholinergic synaptic and neuronal damage and cognitive decline. A beta-mediated damage to ascending cholinergic pathways may be further accentuated by Lewy body and/or cerebrovascular disease. As the disease advances and functioning cholinergic synapses disappear, both the rapid cognitive decline and response to cholinesterase inhibitor therapy in individuals with these factors may diminish. Non-enzymatic functions of the BuChE protein, APOE epsilon 4 status and hyperhomocysteinemia influence the progression of pathology, symptom expression, and response to cholinesterase inhibition in a stage-specific manner in neurodegenerative disorders associated with Alzheimer, Lewy body and vascular pathology.

Visuospatial deficits predict rate of cognitive decline in autopsy-verified dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is often characterized by pronounced impairment in visuospatial skills, attention, and executive functions. However, the strength of the phenotypic expression of DLB varies and may be weaker in patients with extensive concomitant Alzheimer's disease (AD). To determine whether strength of the DLB clinical phenotype impacts cognitive decline, visuospatial and language tests were retrospectively used to predict 2-year rate of global cognitive decline in 22 autopsy-confirmed DLB patients (21 with concomitant AD) and 44 autopsy-confirmed "pure" AD patients. Generalized estimating equations (GEE) revealed a significant interaction such that poor baseline performances on tests of visuospatial skills were strongly associated with a rapid rate of cognitive decline in DLB but not AD (p < .001). No effect of confrontation naming was found. DLB patients with poor visuospatial skills had fewer neurofibrillary tangles and were more likely to experience visual hallucinations than those with better visuospatial skills. These results suggest that the severity of visuospatial deficits in DLB may identify those facing a particularly malignant disease course and may designate individuals whose clinical syndrome is impacted more by Lewy body formation than AD pathology.

A systematic review of the effectiveness of rivastigmine for the treatment of behavioral disturbances in dementia and other neurological disorders

BACKGROUND

Dementia is frequently associated with behavioral disturbances, some of which have a significant impact on patient quality of life and the likelihood of institutionalization. Cholinergic systems, among other neurotransmitters in the brain, appear to be involved with different behaviors, such as psychosis, depression, agitation, and personality changes.

SCOPE

This paper reviews the clinical data on the effectiveness of rivastigmine, a dual inhibitor of acetylcholinesterase and butyrylcholinesterase, in ameliorating behavioral disturbances in different patient populations. Relevant articles were identified through MEDLINE searches with no date restrictions.

FINDINGS

In particular, rivastigmine has shown efficacy in treating behavioral disturbances in patients with a wide range of dementias - Alzheimer's disease, vascular dementia, fronto-temporal dementia, mixed dementia, Lewy body dementia, Parkinson's disease with dementia, and schizophrenia with dementia. Most of the studies have been open-label clinical trials with behavior as a secondary endpoint. The behavior domains that most consistently showed improvement were apathy/indifference, anxiety, delusions (psychosis), and hallucinations. The major limitation of this review is that the effects on behavioral symptoms were usually secondary endpoints in clinical trials.

CONCLUSION

The efficacious effects of treatment with rivastigmine on various behavioral disturbances provide supporting evidence that cholinergic mechanisms, among other neurotransmitters, are involved in the manifestation of some behavioral and psychological symptoms of dementia.

Presentation and management of psychosis in Parkinson's disease and dementia with Lewy bodies

A 73-year-old man with a 10-year history of progressive Parkinson’s disease is referred for psychiatric evaluation and treatment by a neurologist for new-onset confusion and visual hallucinations of strangers in his house. Treatment of the early Parkinson’s symptoms began with a dopamine agonist, and /-dopa was added later to combat worsening tremor, rigidity, slowed mobility, and difficulty performing basic activities of daily living. A more detailed history elicits new-onset depression and vivid dreaming with insomnia. The patient’s wife is concerned about the hallucinations, worsening cognitive impairment, and disturbed sleep, all of which have an impact on her quality of life. Treatment options for addressing these new symptoms include lowering the dosages of antiparkinsonian medications, which can cause or aggravate visual hallucinations and confusion, or adding quetiapine, the atypical antipsychotic drug that is least likely to worsen the parkinsonism. After discussions with the patient and his wife, the decision is made to initiate quetiapine at a dose of 50 mg at bedtime and not to change the antiparkinsonian medication regimen. However, after only a few doses, the patient stops taking the quetiapine because of excessive sedation and increased confusion. An attempt is then made to slowly taper the dopamine agonist, which is more likely than /-dopa to cause psychiatric complications and is less effective as an antiparkinsonian medication. The patient’s parkinsonism worsens, however, so the dosage is restored to the previously effective level. The patient’s condition continues to deteriorate because of increasing visual hallucinations (now accompanied by persecutory delusions regarding the strangers in the house), confusion, and disturbed sleep. An urgent follow-up evaluation is arranged.

Clinical neurophysiology of aging brain: from normal aging to neurodegeneration

Physiological brain aging is characterized by a loss of synaptic contacts and neuronal apoptosis that provokes age-dependent decline of sensory processing, motor performance, and cognitive function. Neural redundancy and plastic remodelling of brain networking, also secondary to mental and physical training, promotes maintenance of brain activity in healthy elderly for everyday life and fully productive affective and intellectual capabilities. However, age is the main risk factor for neurodegenerative disorders such as Alzheimer's disease (AD) that impact on cognition. Oscillatory electromagnetic brain activity is a hallmark of neuronal network function in various brain regions. Modern neurophysiological techniques including electroencephalography (EEG), event-related potential (ERP), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS) can accurately index normal and abnormal brain aging to facilitate non-invasive analysis of cortico-cortical connectivity and neuronal synchronization of firing and coherence of rhythmic oscillations at various frequencies. The present review provides a perspective of these issues by assaying different neurophysiological methods and integrating the results with functional brain imaging findings. It is concluded that discrimination between physiological and pathological brain aging clearly emerges at the group level, with applications at the individual level also suggested. Integrated approaches utilizing neurophysiological techniques together with biological markers and structural and functional imaging are promising for large-scale, low-cost and non-invasive evaluation of at-risk populations. Practical implications of the methods are emphasized.

Demenz mit Lewy-Körperchen

Dementia with Lewy Bodies (DLB) is the second most common form of dementia in the elderly. Core features of the DLB are fluctuating cognitive symptoms, visual hallucinations and spontaneous parkinsonism. The clinical diagnostic criteria are very useful in the differentiation between DLB and Alzheimer's disease. The deficits in cholinergic neurotransmission are pronounced and associated with cognitive and psychotic symptoms. An 83 years old patient with DLB showed well formed recurrent visual hallucinations and fluctuating cognition and attention. There was no response to treatment with atypical neuroleptics. The patient responded within few days to treatment with Donepezil. Both cognitive and behavioural symptoms were improved significantly.

Changes in motor subtype and risk for incident dementia in Parkinson's disease

The objective of this study was to assess the temporal relationship between changes in predominant motor symptoms and incident dementia in Parkinson's disease (PD). A community-based sample of 171 nondemented patients with PD was followed prospectively and examined at baseline and after 4 and 8 years. The motor subtype of Parkinsonism was classified into tremor-dominant (TD), indeterminate, or postural instability gait difficulty (PIGD) subtype at each visit, based on defined items in the Unified Parkinson's Disease Rating Scale, subscales II and III. Dementia was diagnosed according to DSM-III-R criteria, based on clinical interview, cognitive rating scales, and neuropsychological examination. Logistic regression was used to analyze the relationship between subtype of Parkinsonism and dementia. Transition from TD to PIGD subtype was associated with a more than threefold increase in the rate of Mini-Mental State Examination decline. Compared to patients with persistent TD or indeterminate subtype, the odds ratio for dementia was 56.7 (95% CI: 4.0-808.4; P = 0.003) for patients changing from TD or indeterminate subtype to PIGD subtype, and 80.0 (95% CI: 4.6-1400.1; P = 0.003) for patients with persistent PIGD subtype. Patients with TD subtype at baseline did not become demented until they developed PIGD subtype, and dementia did not occur among patients with persistent TD subtype of Parkinsonism. In a substantial proportion of PD patients who develop postural instability and gait disorder during the course of the disease, this transition is associated with accelerated cognitive decline and highly increased risk for subsequent dementia. These findings raise the question whether PIGD and dementia share common or parallel neuropathology.

Motor cortex inhibitory circuits in dementia with Lewy bodies and in Alzheimer's disease

To determine whether a peculiar neurophysiological profile may contribute to characterize dementia with Lewy bodies (DLB) vs. Alzheimer disease (AD), we used transcranial magnetic stimulation to examine the excitability of two different inhibitory systems of the motor cortex, short latency intracortical inhibition (SICI) and short latency afferent inhibition (SAI) in 10 patients with DLB, in 13 patients with AD and in 15 healthy subjects. SICI and SAI were significantly reduced in AD patients, while both were not significantly different from the controls in DLB patients. The differential pattern of SICI and SAI exhibited by AD vs. DLB may have diagnostic significance in discriminating DLB from AD. Furthermore, this technique may help to clarify the pathophysiological entity of DLB; since SAI is a cortical phenomenon that depends on central cholinergic activity, our findings suggest that the mechanisms of cholinergic depletion in DLB may be different from that in AD, while normal SICI may reflect a less pronounced dysregulation of the intracortical GABAergic inhibitory circuitries in DLB.

PD-related psychosis: pathophysiology with therapeutical strategies

Parkinson's disease (PD) is a chronic, neurodegenerative disease with degeneration of the central dopaminergic neurons in the substantia nigra, leading to a depletion of dopamine (DA) in the striatum. This depletion causes the clinical hallmarks of this disease: bradykinesia, hypokinesia, rigidity, tremor and postural instability. Besides these well known motor symptoms, non-motor symptoms may develop, such as hyposmia, sleep disorders, autonomic disturbances, depression, cognitive impairment and psychosis. Pathophysiological mechanisms underlying these symptoms not only comprise Lewy body pathology in the central dopaminergic system, but also in the noradrenergic, serotinergic and cholinergic transmittersystems. Indeed, in Parkinson's disease, about 30-40% of the patients suffers fluctuating psychotic symptoms, mainly paranoid delusions and/or visual or acoustic hallucinations, symptoms considered to represent major contributors to patient and caregiver distress and nursing home placement. Endogenous (related to the disease process itself) as well as exogenous (related to therapeutical interventions) psychotogenic factors may contribute to the development of psychotic symptoms in PD. Therapeutical strategies, therefore, are aimed to reduce both endogenous and exogenous factors. To reduce endogenous psychotogenic factors, cholinesterase inhibitors, suggested to reduce cognitive deterioration, now seem to be the drugs of choice. In exogenously induced psychotic symptoms, atypical antipsychotics are considered the most effective. However, as psychotic symptoms in PD are often influenced by both endogenous and exogenous factors, a combination of both strategies may be preferred.

Effects of rivastigmine in patients with and without visual hallucinations in dementia associated with Parkinson's disease

We aimed to determine prospectively whether rivastigmine, an inhibitor of acetylcholinesterase and butyrylcholinesterase, provided benefits in patients with and without visual hallucinations in a population with dementia associated with Parkinson's disease (PDD). This was a 24-week double-blind placebo-controlled study. Primary efficacy measures were the Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog) and Alzheimer's Disease Cooperative Study-Clinician's Global Impression of Change (ADCS-CGIC). Secondary efficacy measures included activities of daily living, behavioral symptoms, and executive and attentional functions. Patients were stratified according to the presence of visual hallucinations at baseline. The study included 188 visual hallucinators (118 on rivastigmine, 70 on placebo) and 348 nonvisual hallucinators (239 on rivastigmine, 109 on placebo). Rivastigmine provided benefits in both visual hallucinators and nonvisual hallucinators. Absolute responses to rivastigmine on the ADAS-cog were comparable over 6 months, although rivastigmine-placebo differences tended to be larger in visual hallucinators (4.27; P = 0.002) than in nonhallucinators (2.09; P = 0.015). On the ADCS-CGIC, differences between rivastigmine and placebo were 0.5 in visual hallucinators (P = 0.030) and 0.3 in nonhallucinators (P = 0.111). Rivastigmine provided benefits on all secondary efficacy measures, and placebo declines and treatment differences were more marked in visual hallucinators. Adverse events were reported more frequently by rivastigmine-treated patients, although this difference was less marked in visual hallucinators. Visual hallucinations appear to predict more rapid decline and possibly greater therapeutic benefit from rivastigmine treatment in PDD.

Psychotic symptoms in Parkinson’s disease

Psychotic symptoms are common in Parkinson's disease (PD) and occur in at least 20% of medication-treated patients. Benign visual hallucinations usually appear earlier, while malignant hallucinations, confusional states, delusions, paranoid beliefs, agitation, and delirium become more frequent with disease progression. Virtually all antiparkinsonian drugs may produce psychotic symptoms. Cognitive impairment, increased age, disease duration and severity, depression, and sleep disorders have been consistently identified as independent risk factors for their development. Although the precise pathoetiologic mechanisms remain unknown, we review evidence that links ventral dopaminergic pathway dysfunction (overactivity) together with the involvement of other neurotransmitter system imbalances as likely contributors. The clinical importance of the proposed mechanism is that successful management of psychotic symptoms in PD may rely on a multitarget approach to restore neurotransmitter imbalances rather than focusing exclusively on the dopaminergic dysfunction.

Dementia in Parkinson's disease: a post-mortem study in a population of brain donors

OBJECTIVE

To identify factors associated with dementia in a cohort of Parkinson's disease (PD) brain donors and determine whether its presence may influence the clinical phenotype of the disease.

METHODS

We included 67 consecutive patients with a clinical and pathological diagnosis of PD, who while alive, consented to donate their brains to the University of Miami Brain Endowment Bank(TM). Dementia and psychiatric complications of PD were diagnosed according to established criteria. Case histories were abstracted and reviewed and comparisons between PD patients with (PD-D, n = 34) and without (PD, n = 33) dementia were made.

RESULTS

Age at death, age at disease onset and disease duration did not differ significantly between PD-D and PD patients. Other symptoms were similar in both groups. Visual hallucinations and bilateral symptoms at diagnosis were significantly higher in PD-D patients. No association between dementia and overall survival duration was found. Although the frequency of depression and psychosis was higher in the PD patients with dementia no statistical significance was reached. The overall lifetime prevalence of dementia in our group was 50.7%.

CONCLUSIONS

Visual hallucinations and bilateral symptoms were associated with dementia in our cohort of PD brain donors. No association between dementia and survival duration was found. Understanding the influence of dementia on the clinical phenotype of the disease and predicting its development is essential for the successful management of PD.

Depressive symptoms, sex, and risk for Alzheimer's disease

Depression associates with increased risk for dementia and Alzheimer's disease (AD), although it is unclear whether it represents an actual risk factor or a prodrome. To determine the relative hazard of premorbid depressive symptomatology for development of dementia and AD, we studied risk for incident dementia and AD over a 14-year period in 1,357 community-dwelling men and women participating in the 40-year prospective Baltimore Longitudinal Study of Aging. Screening for depressive symptoms, comprehensive medical and neuropsychological evaluations were prospectively collected every 2 years. Time-dependent proportional hazards of development of AD or dementia were calculated separately for men and women, with symptoms of depression detected at 2-, 4-, and 6-year intervals before onset of dementia symptoms. Vascular risk factors were analyzed as covariates. Premorbid depressive symptoms significantly increased risk for dementia, particularly AD in men but not in women. Hazard ratios were approximately two times greater than for individuals without history of depressive symptoms, an effect independent of vascular disease. We conclude that the impact of depressive symptoms on risk for dementia and AD may vary with sex. Further studies assessing separately the role of depression as a risk factor in men and women are necessary.

Mild cognitive impairment in Parkinson's disease: the challenge and the promise

This review addresses the literature surrounding Parkinson's disease (PD) and mild cognitive impairment (MCI). It discusses the neuropsychological, pharmaceutical, and pathological overlap, the socioeconomic impact of PD and MCI, and the value of recognizing, understanding, and treating MCI in PD. It is concluded from this review that MCI in PD does exist and should be considered in clinical and research investigations. Due to the lack of accepted clinical criteria, an inclusive operating definition of MCI in PD is proposed. Research guidelines for studying the presence of MCI in PD and evaluating the efficacy of pharmaceutical interventions are also suggested.

Factors associated with complex visual hallucinations during antidepressant treatment

Published case reports on complex visual hallucinations (CVH) occurring during antidepressant (AD) treatment were reviewed. Thirteen cases of CVH associated with SSRI treatment, 16 cases during tricyclic drug treatment and seven cases with other AD drug treatments were found. Nine patients were taking concomitant drugs while on therapy with SSRIs and four had a neurological disease in addition to depression. The cholinergic impoverishment occurring in dementia states or during concomitant therapy with anticholinergic drugs could increase the sensitivity to serotonergic agonists, triggering the manifestation of CVH. During tricyclic drug treatment, half of the reports were of hypnopompic or hypnagogic hallucinations and this can be associated with the effects of tricyclics (TCA) on sleep architecture. It is likely that the potent anticholinergic effect of amitriptyline was potentiated in a situation of a rapidly changing state of consciousness. In general, the review supports the view that an imbalance between serotonin and acetylcholine systems is at the root of AD-induced CVH, with a profile defined by a cholinergic hypoactivity and a serotonergic hyperactivity. Caution is needed when administering a combination of serotonergic and anticholinergic AD in the treatment of the demented population and in other already compromised patients because there is a risk of precipitating CVH.

Involvement of α6/α3 neuronal nicotinic acetylcholine receptors in neuropsychiatric features of Dementia with Lewy bodies: [125I]-α-conotoxin MII binding in the thalamus and striatum

Dementia with Lewy bodies (DLB) is a neurodegenerative disease associated with a range of neuropsychiatric symptoms and reduced expression of neuronal nicotinic acetylcholine receptors (nAChRs) in neocortex, hippocampus, thalamus and basal ganglia. To determine whether there are selective associations between alterations in alpha6/alpha3 neuronal nicotinic acetylcholine receptors (nAChRs) and the two key neuropsychiatric features of DLB, impaired consciousness (IC) and visual hallucinations (VH), quantitative [(125)I]-alpha-conotoxin MII ([(125)I]-alpha-Ctx MII) autoradiography was undertaken on 28 people with DLB and 15 control cases from the Newcastle Brain Bank. There was a highly significant overall trend for reduced thalamic [(125)I]-alpha-Ctx MII binding in DLB (p < 0.001), with significant deficits in the centromedian, ventral lateral and ventroposterior medial thalamic nuclei (p < 0.05), together with caudate and putamen (p < 0.001). [(125)I]-alpha-Ctx MII binding was significantly lower in DLB cases with IC than without IC in the putamen (p < 0.05), however there was no significant association between [(125)I]-alpha-Ctx MII binding and VH. Reductions in [(125)I]-alpha-Ctx MII binding in caudate and putamen were paralleled by similar reductions in [(125)I]PE2I binding. [(125)I]PE2I binding was also significantly lower in DLB cases with IC than without IC in the caudate (p < 0.05) and putamen (p < 0.001). These results demonstrate that deficits in alpha6/alpha3 nAChRs occur in specific brain regions in DLB, may in part be related to the loss of dopaminergic neurons and may contribute to the development of impaired consciousness in the disorder.