Correlation between clinical symptoms and striatal DAT uptake in patients with DLB

Association between longitudinal changes in striatal dopamine transporter uptake and clinical features of dementia with Lewy bodies

BACKGROUND

It is widely known that there is low striatal 123 I-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3- fluoropropyl) nortropane (123 I-FP-CIT) dopamine transporter single photon emission tomography (DaT-SPECT) uptake in patients with dementia with Lewy bodies (DLB). No studies to date have analyzed the association between longitudinal changes of clinical features and DaT uptake in patients with Parkinson syndrome, particularly those with DLB. The aim of this study was to investigate the association between the longitudinal changes in DaT uptake and the severity of parkinsonism and cognitive function in DLB patients.

METHODS

A total of 35 outpatients with probable DLB who underwent DaT-SPECT twice (at the initial examination and the follow-up period) in the Memory Disorder Clinic at the Department of Geriatric Medicine, Tokyo Medical University, were enrolled in this study between April 2014 and September 2020. The correlation between annual changes in DaT uptake and clinical features (cognitive function decline and parkinsonism) of the patients was analyzed.

RESULTS

A significant correlation was detected between annual changes in parkinsonism symptom severity and DaT uptake in the left posterior putamen (r = -0.39, P = 0.03), and between Mini-Mental State Examination scores and DaT uptake in all regions except the right posterior putamen (P < 0.05) in patients with DLB.

CONCLUSIONS

Our results suggested that the pathway from the ventrolateral tier of the substantia nigra to the putamen might be more crucial for motor function than other pathways, not only in Parkinson's disease but also in DLB.

Genetic Architecture and Molecular, Imaging and Prodromic Markers in Dementia with Lewy Bodies: State of the Art, Opportunities and Challenges

Dementia with Lewy bodies (DLB) is one of the most common causes of dementia and belongs to the group of α-synucleinopathies. Due to its clinical overlap with other neurodegenerative disorders and its high clinical heterogeneity, the clinical differential diagnosis of DLB from other similar disorders is often difficult and it is frequently underdiagnosed. Moreover, its genetic etiology has been studied only recently due to the unavailability of large cohorts with a certain diagnosis and shows genetic heterogeneity with a rare contribution of pathogenic mutations and relatively common risk factors. The rapid increase in the reported cases of DLB highlights the need for an easy, efficient and accurate diagnosis of the disease in its initial stages in order to halt or delay the progression. The currently used diagnostic methods proposed by the International DLB consortium rely on a list of criteria that comprises both clinical observations and the use of biomarkers. Herein, we summarize the up-to-now reported knowledge on the genetic architecture of DLB and discuss the use of prodromal biomarkers as well as recent promising candidates from alternative body fluids and new imaging techniques.

β-Amyloid PET and 123I-FP-CIT SPECT in Mild Cognitive Impairment at Risk for Lewy Body Dementia

OBJECTIVE

To determine the clinical phenotypes associated with the β-amyloid PET and dopamine transporter imaging (123I-FP-CIT SPECT) findings in mild cognitive impairment (MCI) with the core clinical features of dementia with Lewy bodies (DLB; MCI-LB).

METHODS

Patients with MCI who had at least 1 core clinical feature of DLB (n = 34) were grouped into β-amyloid A+ or A- and 123I-FP-CIT SPECT D+ or D- groups based on previously established abnormality cut points for A+ with Pittsburgh compound B PET standardized uptake value ratio (PiB SUVR) ≥1.48 and D+ with putamen z score with DaTQUANT <-0.82 on 123I-FP-CIT SPECT. Individual patients with MCI-LB fell into 1 of 4 groups: A+D+, A+D-, A-D+, or A-D-. Log-transformed PiB SUVR and putamen z score were tested for associations with patient characteristics.

RESULTS

The A-D+ biomarker profile was most common (38.2%), followed by A+D+ (26.5%) and A-D- (26.5%). The least common was the A+D- biomarker profile (8.8%). The A+ group was older, had a higher frequency of APOE ε4 carriers, and had a lower Mini-Mental State Examination score than the A- group. The D+ group was more likely to have probable REM sleep behavior disorder. Lower putamen DaTQUANT z scores and lower PiB SUVRs were independently associated with higher Unified Parkinson's Disease Rating Scale-III scores.

CONCLUSIONS

A majority of patients with MCI-LB are characterized by low β-amyloid deposition and reduced dopaminergic activity. β-Amyloid PET and 123I-FP-CIT SPECT are complementary in characterizing clinical phenotypes of patients with MCI-LB.

Biomarker Use for Dementia With Lewy Body Diagnosis: Survey of US Experts

BACKGROUND

Dementia with Lewy body (DLB) diagnostic criteria define "indicative" and "supportive" biomarkers, but clinical practice patterns are unknown.

METHODS

An anonymous survey querying clinical use of diagnostic tests/biomarkers was sent to 38 center of excellence investigators. The survey included "indicative" biomarkers (dopamine transporter scan, myocardial scintigraphy, polysomnography), "supportive" biomarkers [magnetic resonance imaging (MRI)], positron emission tomography, or single-photon emission computed tomography perfusion/metabolism scans, quantitative electroencephalography), and other diagnostic tests (neuropsychological testing, cerebrospinal fluid analysis, genetics). Responses were analyzed descriptively.

RESULTS

Of the 22 respondents (58%), all reported the capability to perform neuropsychological testing, MRI, polysomnography, dopamine transporter scans, positron emission tomography/single-photon emission computed tomography scans, and cerebrospinal fluid analysis; 96% could order genetic testing. Neuropsychological testing and MRI were the most commonly ordered tests. Diagnostic testing beyond MRI and neuropsychological testing was most helpful in the context of "possible" DLB and mild cognitive impairment and to assist with differential diagnosis. Myocardial scintigraphy and electroencephalograpy use were rare.

CONCLUSIONS AND RELEVANCE

Neuropsychological testing and MRI remain the most widely used diagnostic tests by DLB specialists. Other tests-particularly indicative biomarkers-are used only selectively. Research is needed to validate existing potential DLB biomarkers, develop new biomarkers, and investigate mechanisms to improve DLB diagnosis.

[Fluctuation of cognitive functions in dementia with Lewy bodies]

Fluctuations of cognitive function (FCF) is one of the core diagnostic features of dementia with Lewy bodies (DLB). However, identification, pathophysiology, management of this unusual phenomena remain poor understood. The review presents modern ideas about phenomenology, causes, systematization, clinical significance and current methods of diagnosis and treatment of FCF in patients with DLB.

Fluctuating cognition in the Lewy body dementias

Fluctuating cognition is a core diagnostic feature of dementia with Lewy bodies and is also a key clinical feature of Parkinson's disease dementia. These dementias share common pathological features and are referred to as Lewy body dementias. Whilst highly prevalent in Lewy body dementia, with up to 90% of patients experiencing the symptom at some point in the disease trajectory, clinical identification of fluctuating cognition is often challenging. Furthermore, its underlying pathophysiological processes remain unclear. However, neuroimaging and neurophysiological techniques have recently provided insight into potential drivers of the phenomenon. In this update, we review data pertaining to clinical features and underlying mechanisms of fluctuating cognition in Lewy body dementia. We collate evidence for different proposed aetiologies: fluctuating cognition as an attentional disorder, as a consequence of loss of cholinergic drive, as a manifestation of failure in neuronal efficiency and synchrony, and as a disorder of sleep/arousal. We also review data relating to putative mechanisms that have received less attention to date. Increased understanding of fluctuating cognition may help to illuminate pathophysiological mechanisms in cognitive processing in Lewy body dementia, guide future research, and facilitate the design of targeted therapeutic approaches.

A diagnostic strategy for Lewy body disease using DAT-SPECT, MIBG and Combined index

PURPOSE

The functional imaging methods widely used for the diagnosis of Lewy body disease (LBD) are ¹²³I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropan (FP-CIT) with dopamine transporter single photon emission computed tomography (DAT-SPECT) and ¹²³I-iodobenzylguanidine (MIBG) myocardial scintigraphy. The aim of this study was to determine whether DAT-SPECT or ¹²³I-MIBG myocardial scintigraphy should be examined first and to evaluate whether the combined use of DAT-SPECT and MIBG myocardial scintigraphy is superior to using either modality alone for diagnosing suspected LBD.

METHODS

In this retrospective study, a total of 117 patients suspected of having LBD underwent DAT-SPECT imaging followed by MIBG myocardial scintigraphy. The delayed heart-to-mediastinum (H/M) ratio of MIBG scintigraphy, and the specific binding ratio (SBR) of DAT-SPECT imaging, and Combined index (defined as SBR mean × H/M in the delayed phase) were used as semi-quantitative measures. The diagnostic ability was evaluated using these indexes.

RESULTS

The sensitivity, specificity, and accuracy of diagnosing Lewy body disease were 59.6%, 71.4%, and 67.5% by SBR mean of DAT-SPECT, 85.1%, 91.4%, and 88.9% by delayed H/M ratio of MIBG myocardial scintigraphy, 76.6%, 74.3%, and 75.2% by Combined index, respectively.

CONCLUSION

In the diagnosis of LBD, DAT-SPECT, MIBG myocardial scintigraphy, and Combined index may be reliable indices. In particular, MIBG myocardial scintigraphy was the specific modality for LBD diagnosis. Understanding the effectiveness and limits of DAT-SPECT and MIBG myocardial scintigraphy and using both properly will lead to a more accurate diagnosis and better treatment.

Longitudinal study of striatal aromatic l-amino acid decarboxylase activity in patients with idiopathic rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

To determine if nigrostriatal dopaminergic system function, evaluated by aromatic l-amino acid decarboxylase (AADC) activity using 6-[¹⁸F]fluoro-meta-tyrosine brain positron emission tomography (FMT-PET) can accurately and efficiently identify idiopathic rapid-eye-movement behavior disorder (IRBD) individuals at risk for conversion to a clinical diagnosis of Parkinson's disease (PD) or dementia with Lewy bodies (DLB).

METHODS

We assessed prospectively striatal aromatic l-amino acid decarboxylase activity using FMT brain PET imaging in IRBD patients who were followed systematically every 1-3 months for 1-10 years. IRBD patients (n = 27) were enrolled in this prospective cohort study starting in 2009. Those who underwent follow-up scans between January 2011 and September 2014 (n = 24) were analyzed in the present study.

RESULTS

Of the 24 IRBD patients with baseline and follow-up FMT-PET scans, 11 (45.8%) developed PD (n = 6) or DLB (n = 5). Compared to IRBD patients who were still disease-free, those who developed PD (n = 5) or DLB with parkinsonism (n = 1) had significantly reduced bilateral putaminal FMT uptake during the follow-up. Furthermore, the rate of FMT decline between baseline and follow-up scans was higher in all converted patients, even for those with DLB without parkinsonism, than in IRBD patients who remained disease-free.

CONCLUSIONS

FMT-PET, which represents a dynamic change in AADC activity over time, may also be a useful predictor for the risk of conversion to PD or DLB over short-term clinical follow-up periods, or when testing neuroprotective and restorative strategies in the prodromal phases of PD or DLB.

The Pharmacology of Visual Hallucinations in Synucleinopathies

Visual hallucinations (VH) are commonly found in the course of synucleinopathies like Parkinson's disease and dementia with Lewy bodies. The incidence of VH in these conditions is so high that the absence of VH in the course of the disease should raise questions about the diagnosis. VH may take the form of early and simple phenomena or appear with late and complex presentations that include hallucinatory production and delusions. VH are an unmet treatment need. The review analyzes the past and recent hypotheses that are related to the underlying mechanisms of VH and then discusses their pharmacological modulation. Recent models for VH have been centered on the role played by the decoupling of the default mode network (DMN) when is released from the control of the fronto-parietal and salience networks. According to the proposed model, the process results in the perception of priors that are stored in the unconscious memory and the uncontrolled emergence of intrinsic narrative produced by the DMN. This DMN activity is triggered by the altered functioning of the thalamus and involves the dysregulated activity of the brain neurotransmitters. Historically, dopamine has been indicated as a major driver for the production of VH in synucleinopathies. In that context, nigrostriatal dysfunctions have been associated with the VH onset. The efficacy of antipsychotic compounds in VH treatment has further supported the notion of major involvement of dopamine in the production of the hallucinatory phenomena. However, more recent studies and growing evidence are also pointing toward an important role played by serotonergic and cholinergic dysfunctions. In that respect, in vivo and post-mortem studies have now proved that serotonergic impairment is often an early event in synucleinopathies. The prominent cholinergic impairment in DLB is also well established. Finally, glutamatergic and gamma aminobutyric acid (GABA)ergic modulations and changes in the overall balance between excitatory and inhibitory signaling are also contributing factors. The review provides an extensive overview of the pharmacology of VH and offers an up to date analysis of treatment options.

Visual hallucinations, thalamocortical physiology and Lewy body disease: A review

One of the core diagnostic criteria for Dementia with Lewy Bodies (DLB) is the presence of visual hallucinations. The presence of hallucinations, along with fluctuations in the level of arousal and sleep disturbance, point to potential pathological mechanisms at the level of the thalamus. However, the potential role of thalamic dysfunction in DLB, particularly as it relates to the presence of formed visual hallucinations is not known. Here, we review the literature on the pathophysiology of DLB with respect to modern theories of thalamocortical function and attempt to derive an understanding of how such hallucinations arise. Based on the available literature, we propose that combined thalamic-thalamic reticular nucleus and thalamocortical pathology may explain the phenomenology of visual hallucinations in DLB. In particular, diminished α7 cholinergic activity in the thalamic reticular nucleus may critically disinhibit thalamocortical activity. Further, concentrated pathological changes within the posterior regions of the thalamus may explain the predilection for the hallucinations to be visual in nature.

Dementia with Lewy bodies: Challenges in the diagnosis and management

OBJECTIVE

Dementia with Lewy bodies is the second most common form of neurodegenerative dementia in older age yet is often under-recognised and misdiagnosed. This review aims to provide an overview of the clinical features of dementia with Lewy bodies, discussing the frequent challenges clinicians experience in diagnosing dementia with Lewy bodies, and outlines a practical approach to the clinical management, particularly in the Australian setting.

METHODS

This paper is a narrative review and a semi-structured database (PubMed and MEDLINE) search strategy was implemented. Articles were screened and clinically relevant studies were selected for inclusion.

RESULTS

Dementia with Lewy bodies is clinically characterised by complex visual hallucinations, spontaneous motor parkinsonism, prominent cognitive fluctuations and rapid eye movement sleep behaviour disorder. Neuropsychiatric features and autonomic dysfunction are also common. The new diagnostic criteria and specific diagnostic biomarkers help to improve detection rates and diagnostic accuracy, as well as guide appropriate management. Clinical management of dementia with Lewy bodies is challenging and requires an individualised multidisciplinary approach with specialist input.

CONCLUSION

Dementia with Lewy bodies is a common form of dementia. It often presents as a diagnostic challenge to clinicians, particularly at early stages of disease, and in patients with mixed neuropathological changes, which occur in over 50% of people with dementia with Lewy bodies. Prompt diagnosis and comprehensive treatment strategies are important in improving patients' care.

Diffuse Lewy body disease

Diffuse Lewy body disease, also called dementia with Lewy bodies (DLB), is defined as progressive dementia and pathological Lewy bodies distributed in the central and autonomic nervous systems. The clinical features are dementia, cognitive fluctuations, visual hallucinations, parkinsonism, and REM sleep behavior disorder (RBD). Confirmatory techniques include dopamine transporter imaging, meta-iodobenzylguanidine (MIBG) myocardial scintigraphy, and polysomnography. The pathology finding in DLB is misfolded alpha-synuclein, the main component of Lewy bodies, propagating in the central nervous system. This may interrupt the acetylcholine pathway and activate an inflammatory response. Mutations of several genes have been found in patients with DLB, including SNCA, GBA, and APOE. The differential diagnosis of DLB and Parkinson's disease with dementia (PDD) is a debated issue. Clinical features distinguishing DLB from PDD include the timing of dementia and visual hallucinations, responses to dopaminergic agents and anti-psychotics, and imaging findings. As to the management of DLB, cholinesterase inhibitors are the Level-A recommendation for treating dementia in DLB patients and also are beneficial for treating visual hallucinations and psychotic symptoms. Dopamine agonists have the risk of inducing psychotic symptoms, while levodopa should be used carefully for motor symptoms. Melatonin and clonazepam are effective in controlling RBD. Several other treatment methods are undergoing trials, including pimavanserine, nilotinib, psychological interventions, and behavior therapy.

Molecular Imaging of Dementia With Lewy Bodies

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia. The core clinical features of DLB include fluctuating cognition, visual hallucinations, rapid eye movement sleep behavior disorder, and parkinsonism. Molecular imaging is a powerful tool to assess the brain function in vivo. In this chapter, we reviewed the positron emission tomography, single-photon emission computed tomography, and [¹²³I]-metaiodobenzylguanidine scintigraphy studies evaluating the pathological processes underlying DLB, including altered brain metabolism and neurotransmitter pathways, abnormal protein aggregation, and neuroinflammation. These techniques can aid in the differential diagnosis of DLB (versus Alzheimer's disease and related dementia) and in the monitoring disease progression and treatment efficacy of disease-modifying drugs. Furthermore, we explored the limitations of current imaging biomarkers and future directions, particularly focusing on the vital need for tracers that have high affinity for alpha-synuclein.

SPG11-related parkinsonism: Clinical profile, molecular imaging and l-dopa response

BACKGROUND

Molecular imaging has proven to be a powerful tool to elucidate degenerated paths in a wide variety of neurological diseases and has not been systematically studied in hereditary spastic paraplegias.

OBJECTIVES

To investigate dopaminergic degeneration in a cohort of 22 patients with hereditary spastic paraplegia attributed to SPG11 mutations and evaluate treatment response to l-dopa.

METHODS

Patients and controls underwent single-photon emission computed tomography imaging utilizing ^99m Tc-TRODAT-1 tracer. A single-blind trial with 600 mg of l-dopa was performed comparing UPDRS scores.

RESULTS

Reduced dopamine transporter density was universal among patients. Nigral degeneration was symmetrical and correlated with disease duration and motor and cognitive handicap. No statistically significant benefit could be demonstrated with l-dopa intake during the trial.

CONCLUSION

Disruption of presynaptic dopaminergic pathways is a widespread phenomenon in patients with SPG11 mutations, even in the absence of parkinsonism. Unresponsiveness to treatment could be related to postsynaptic damage that needs to be further investigated.

Advances in SPECT Methodology

The emerging role of molecular imaging has made possible to evaluate and quantify biochemical changes of molecular targets in specific neurochemical systems involved in movement disorders, providing neurochemical information of clinical changes before the pathological features occurred. In detail, radionuclides imaging techniques are frequently used for the in vivo study of neurotransmitter and receptor function, alterations in cerebral blood flow and metabolic activity, abnormal protein deposition, and inflammation, with a central role in molecular imaging for preclinical and clinical studies. The present chapter represents an overview of main use of single-photon emission computed tomography (SPECT) in movement disorders, with a focal attention on specific radiotracers used, recent advances in SPECT technology and reconstruction algorithm and added specific value of semiquantitative methods for images analysis. Finally, a brief paragraph is dedicated to description of SPECT/CT devices and advantages of using hybrid technology.

Clinical imaging in dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is a common neurodegenerative dementia in older people; however, the clinical features, particularly cognitive fluctuations and rapid eye movement sleep disorder, are often hard to elicit, leading to difficulty in making the diagnosis clinically. Here we examine the literature for the evidence behind imaging modalities that could assist in making the diagnosis. Dopamine transporter (DAT) imaging remains the best modality for differentiation from dementia of Alzheimer's type with high sensitivity and specificity reported based on pathological diagnoses. 123Iodine-metaiodobenzylguanidine myocardial scintigraphy (MIBG) however is rapidly becoming an alternative imaging modality for the diagnosis of DLB, though studies assessing its accuracy with postmortem verification are still awaited. However, there are suggestions that MIBG may be better in the differentiation of vascular parkinsonism from DLB than DAT scans but may have lower sensitivity for detecting DLB compared with the 80% sensitivity seen in DAT imaging. Structural MRI scans have long been used for the diagnosis of dementia; however, their utility in DLB is limited to revealing the presence of coexisting Alzheimer's disease. Fluorodeoxyglucose (FDG) PET is an alternative biomarker that can also differentiate Alzheimer's disease and DLB but lacks the evidence base of both DAT and MIBG scans.

Dementia with Lewy bodies and Parkinson's disease-dementia: current concepts and controversies

Dementia with Lewy bodies (DLB) and Parkinson's disease-dementia (PDD), although sharing many clinical, neurochemical and morphological features, according to DSM-5, are two entities of major neurocognitive disorders with Lewy bodies of unknown etiology. Despite considerable clinical overlap, their diagnosis is based on an arbitrary distinction between the time of onset of motor and cognitive symptoms: dementia often preceding parkinsonism in DLB and onset of cognitive impairment after onset of motor symptoms in PDD. Both are characterized morphologically by widespread cortical and subcortical α-synuclein/Lewy body plus β-amyloid and tau pathologies. Based on recent publications, including the fourth consensus report of the DLB Consortium, a critical overview is given. The clinical features of DLB and PDD include cognitive impairment, parkinsonism, visual hallucinations, and fluctuating attention. Intravitam PET and post-mortem studies revealed more pronounced cortical atrophy, elevated cortical and limbic Lewy pathologies (with APOE ε4), apart from higher prevalence of Alzheimer pathology in DLB than PDD. These changes may account for earlier onset and greater severity of cognitive defects in DLB, while multitracer PET studies showed no differences in cholinergic and dopaminergic deficits. DLB and PDD sharing genetic, neurochemical, and morphologic factors are likely to represent two subtypes of an α-synuclein-associated disease spectrum (Lewy body diseases), beginning with incidental Lewy body disease-PD-nondemented-PDD-DLB (no parkinsonism)-DLB with Alzheimer's disease (DLB-AD) at the most severe end, although DLB does not begin with PD/PDD and does not always progress to DLB-AD, while others consider them as the same disease. Both DLB and PDD show heterogeneous pathology and neurochemistry, suggesting that they share important common underlying molecular pathogenesis with AD and other proteinopathies. Cognitive impairment is not only induced by α-synuclein-caused neurodegeneration but by multiple regional pathological scores. Recent animal models and human post-mortem studies have provided important insights into the pathophysiology of DLB/PDD showing some differences, e.g., different spreading patterns of α-synuclein pathology, but the basic pathogenic mechanisms leading to the heterogeneity between both disorders deserve further elucidation. In view of the controversies about the nosology and pathogenesis of both syndromes, there remains a pressing need to differentiate them more clearly and to understand the processes leading these synucleinopathies to cause one disorder or the other. Clinical management of both disorders includes cholinesterase inhibitors, other pharmacologic and nonpharmacologic strategies, but these have only a mild symptomatic effect. Currently, no disease-modifying therapies are available.