Loss of Dopamine Transporter Binding and Clinical Symptoms in Dementia With Lewy Bodies

Behavioral disorders in dementia with Lewy bodies: old and new knowledge

Dementia with Lewy bodies (DLB), the second most common primary degenerative neurocognitive disorder after Alzheimer disease, is frequently preceded by REM sleep behavior disorders (RBD) and other behavioral symptoms, like anxiety, irritability, agitation or apathy, as well as visual hallucinations and delusions, most of which occurring in 40-60% of DLB patients. Other frequent behavioral symptoms like attention deficits contribute to cognitive impairment, while attention-deficit/hyperactivity disorder (ADHD) is a risk factor for DLB. Behavioral problems in DLB are more frequent, more severe and appear earlier than in other neurodegenerative diseases and, together with other neuropsychiatric symptoms, contribute to impairment of quality of life of the patients, but their pathophysiology is poorly understood. Neuroimaging studies displayed deficits in cholinergic brainstem nuclei and decreased metabolism in frontal, superior parietal regions, cingulate gyrus and amygdala in DLB. Early RBD in autopsy-confirmed DLB is associated with lower Braak neuritic stages, whereas those without RBD has greater atrophy of hippocampus and increased tau burden. αSyn pathology in the amygdala, a central region in the fear circuitry, may contribute to the high prevalence of anxiety, while in attention dysfunctions the default mode and dorsal attention networks displayed diverging activity. These changes suggest that behavioral disorders in DLB are associated with marked impairment in large-scale brain structures and functional connectivity network disruptions. However, many pathobiological mechanisms involved in the development of behavioral disorders in DLB await further elucidation in order to allow an early diagnosis and adequate treatment to prevent progression of these debilitating disorders.

Diagnostic Sensitivity and Symptomatic Relevance of Dopamine Transporter Imaging and Myocardial Sympathetic Scintigraphy in Patients with Dementia with Lewy Bodies

Background

Dementia with Lewy bodies (DLB) presents with various symptoms, posing challenges for early diagnosis challenging. Dopamine transporter (123I-FP-CIT) single-photon emission tomography (SPECT) and 123I-meta-iodobenzylguanidine (123I-MIBG) imaging are crucial diagnostic biomarkers. Hypothesis about body- and brain-first subtypes of DLB indicate that some DLB may show normal 123I-FP-CIT or 123I-MIBG results; but the characteristic expression of these two subtypes remains unclear.

Objective

This study aimed to evaluate the diagnostic sensitivity of 123I-FP-CIT and 123I-MIBG imaging alone, combined in patients with DLB and explore symptoms associated with the abnormal imaging results.

Methods

Demographic data, clinical status, and imaging results were retrospectively collected from patients diagnosed with possible DLB. Both images were quantified using semi-automated software, and the sensitivity of each imaging modality and their combination was calculated. Demographic data, cognition, and motor and non-motor symptoms were compared among the subgroups based on the imaging results. Symptoms related to each imaging abnormality were examined using binomial logistic regression analyses.

Results

Among 114 patients with DLB, 80 underwent 123I-FP-CIT SPECT (sensitivity: 80.3%), 83 underwent 123I-MIBG imaging (68.2%), and 66 both (sensitivity of either abnormal result: 93.9%). Visual hallucinations differed among the four subgroups based on imaging results. Additionally, nocturia and orthostatic hypotension differed between abnormal and normal 123I-MIBG images.

Conclusions

Overall, 123I-FP-CIT SPECT was slightly higher sensitivity than 123I-MIBG imaging, with combined imaging increasing diagnostic sensitivity. Normal results of a single imaging test may not refute DLB. Autonomic symptoms may lead to abnormal 123I-MIBG scintigraphy findings indicating body-first subtype of 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.

Striatal dopamine transporter binding differs between dementia with Lewy bodies and Parkinson's disease with dementia

¹²³I-ioflupane single-photon emission computed tomography (SPECT) is a highly sensitive and established neuroimaging technique for parkinsonian syndromes (PS). However, differentiating PS by visual inspection or analysis of regions of interest is challenging. To date, image analysis has not been able to differentiate dementia with Lewy bodies (DLB) from Parkinson's disease with dementia (PDD). This study aimed to differentiate PS based on the characteristics of striatal dopamine transporter (DAT) binding using voxel-based analysis. We acquired ¹²³I-ioflupane SPECT data from patients with DLB (n = 30), Parkinson's disease (PD; n = 122), PDD (n = 19), multiple system atrophy with predominant parkinsonism (MSA-P; n = 18), and progressive supranuclear palsy (PSP; n = 45). DAT binding was reduced in the posterior striatum of patients with PD and PDD, whereas it was similar in MSA-P, PSP, and DLB. Hippocampal atrophy, visually evaluated by cerebral magnetic resonance imaging, did not affect striatal DAT binding in DLB. DAT binding in the anterior striatum was inversely correlated with the severity of parkinsonism in PD and PDD but not in DLB. Thus, the appearance of striatal DAT binding might indicate different pathological processes in DLB and PDD.

Substantia nigral dopamine transporter uptake in dementia with Lewy bodies

Nigrostriatal dopaminergic degeneration is a pathological hallmark of dementia with Lewy bodies (DLB). To identify the subregional dopamine transporter (DAT) uptake patterns that improve the diagnostic accuracy of DLB, we analyzed N-(3-[18F] fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl)-nortropane (FP-CIT) PET in 51 patients with DLB, in 36 patients with mild cognitive impairment with Lewy body (MCI-LB), and in 40 healthy controls (HCs). In addition to a high affinity for DAT, FP-CIT show a modest affinity to serotonin or norepinephrine transporters. Specific binding ratios (SBRs) of the nigrostriatal subregions were transformed to age-adjusted z-scores (zSBR) based on HCs. The diagnostic accuracy of subregional zSBRs were tested using receiver operating characteristic (ROC) curve analyses separately for MCI-LB and DLB versus HCs. Then, the effect of subregional zSBRs on the presence of clinical features and gray matter (GM) density were evaluated in all patients with MCI-LB or DLB as a group. ROC curve analyses showed that the diagnostic accuracy of DLB based on the zSBR of substantia nigra (area under the curve [AUC], 0.90) or those for MCI-LB (AUC, 0.87) were significantly higher than that based on the zSBR of posterior putamen for DLB (AUC, 0.72) or MCI-LB (AUC, 0.65). Lower zSBRs in nigrostriatal regions were associated with visual hallucination, severe parkinsonism, and cognitive dysfunction, while lower zSBR of substantia nigra was associated with widespread GM atrophy in DLB and MCI-LB patients. Taken together, our results suggest that evaluation of nigral DAT uptake may increase the diagnostic accuracy of DLB and MCI-LB than other striatal regions.

The diagnostic performance of functional dopaminergic scintigraphic imaging in the diagnosis of dementia with Lewy bodies: an updated systematic review

INTRODUCTION

Dopaminergic scintigraphic imaging is a cornerstone to support the diagnosis in dementia with Lewy bodies. To clarify the current state of knowledge on this imaging modality and its impact on clinical diagnosis, we performed an updated systematic review of the literature.

METHODS

This systematic review was carried out according to PRISMA guidelines. A comprehensive computer literature search of PubMed/MEDLINE, EMBASE, and Cochrane Library databases for studies published through June 2022 was performed using the following search algorithm: (a) "Lewy body" [TI] OR "Lewy bodies" [TI] and (b) ("DaTscan" OR "ioflupane" OR "123ip" OR "123?ip" OR "123 ip" OR "123i-FP-CIT" OR "FPCIT" OR "FP-CIT" OR "beta?CIT" OR "beta CIT" OR "CIT?SPECT" OR "CIT SPECT" OR "Dat?scan*" OR "dat scan*" OR "dat?spect*" OR "SPECT"). Risk of bias and applicability concerns of the studies were evaluated using the QUADAS-2 tool.

RESULTS

We performed a qualitative analysis of 59 studies. Of the 59 studies, 19 (32%) addressed the diagnostic performance of dopamine transporter imaging, 15 (25%) assessed the identification of dementia with Lewy bodies in the spectrum of Lewy body disease and 18 (31%) investigated the role of functional dopaminergic imaging in distinguishing dementia with Lewy bodies from other dementias. Dopamine transporter loss was correlated with clinical outcomes in 19 studies (32%) and with other functional imaging modalities in 15 studies (25%). Heterogeneous technical aspects were found among the studies through the use of various radioligands, the more prevalent being the [123I]N‑ω‑fluoropropyl‑2β‑carbomethoxy‑3β‑(4‑iodophenyl) nortropane (123I-FP-CIT) in 54 studies (91.5%). Image analysis used visual analysis (9 studies, 15%), semi-quantitative analysis (29 studies, 49%), or a combination of both (16 studies, 27%).

CONCLUSION

Our systematic review confirms the major role of dopaminergic scintigraphic imaging in the assessment of dementia with Lewy bodies. Early diagnosis could be facilitated by identifying the prodromes of dementia with Lewy bodies using dopaminergic scintigraphic imaging coupled with emphasis on clinical neuropsychiatric symptoms. Most published studies use a semi-quantitative analytical assessment of tracer uptake, while there are no studies using quantitative analytical methods to measure dopamine transporter loss. The superiority of a purely quantitative approach to assess dopaminergic transmission more accurately needs to be further clarified.

The low dopamine hypothesis: A plausible mechanism underpinning residual urine, overactive bladder and nocturia (RON) syndrome in older patients

INTRODUCTION

Aging is associated with a combination of several lower urinary tract (LUT) signs and symptoms, including residual urine, overactive bladder and nocturia. One of the mechanisms of this LUT dysfunction that has not been discussed in dept so far is the role of dopamine (DA).

METHODS

In this narrative review, we explore the dopaminergic hypothesis in the development of this combination of LUT signs and symptoms in older adults.

RESULTS

DA is one of the neurotransmitters whose regulation and production is disrupted in aging. In synucleinopathies, altered DAergic activity is associated with the occurrence of LUTS and sleep disorders. Projections of DAergic neurons are involved in the regulation of sleep, diuresis, and bladder activity. The low dopamine hypothesis could explain the genesis of a set of LUT signs and symptoms commonly seen in this population, including elevated residual urine, Overactive bladder syndrome and Nocturia (discussed as the RON syndrome). This presentation is however also common in older patients without synucleinopathies or neurological disorders and therefore we hypothesise that altered DAergic activity because of pathological aging, and selective destruction of DAergic neurons, could underpin the presentation of this triad of LUT dysfunction in the older population.

CONCLUSION

The concept of RON syndrome helps to better understand this common phenotypic presentation in clinical practice, and therefore serves as a useful platform to diagnose and treat LUTS in older adults. Besides recognizing the synucleinopathy "red flag" symptoms, this set of multi-causal LUT signs and symptoms highlights the inevitable need for combination therapy, a challenge in older people with their comorbidities and concomitant medications.

Efficacy and Safety of Zonisamide in Dementia with Lewy Bodies Patients with Parkinsonism: A Post Hoc Analysis of Two Randomized, Double-Blind, Placebo-Controlled Trials

Background:

Although previous phase II and III clinical trials conducted in Japan showed that zonisamide improved parkinsonism in patients with dementia with Lewy bodies (DLB), some differences in efficacy outcomes were observed between the trials.

Objective:

We aimed to further examine the efficacy and safety of zonisamide in DLB patients with parkinsonism in a post hoc analysis of pooled data from the previous phase II and III trials.

Methods:

Both trials featured a 4-week run-in period followed by a 12-week treatment period with a double-blind, placebo-controlled, parallel-group, randomized, multicenter trial design. In our pooled analysis, the primary outcome was the change in Unified Parkinson’s Disease Rating Scale (UPDRS) part III total score. Other outcomes included the changes in Mini-Mental State Examination (MMSE) and Neuropsychiatric Inventory-10 (NPI-10) scores, and the incidence of adverse events.

Results:

Zonisamide significantly decreased the UPDRS part III total and individual motor symptom scores but did not affect the MMSE or NPI-10 scores at week 12. There was no difference in the incidence of adverse events between the zonisamide and placebo groups except for decreased appetite, which had an increased frequency in the zonisamide 50 mg group compared with placebo.

Conclusion:

Our findings indicate that zonisamide improved parkinsonism with DLB without deterioration of cognitive function and or worsening behavioral and psychological symptoms of dementia.

LeSCoD: a new clinical scale for the detection of Lewy body disease in neurocognitive disorders

BACKGROUND

Dementia with Lewy bodies remains underdiagnosed in clinical practice mainly because of the low sensitivity of existing diagnostic criteria and a strong overlap with Alzheimer's pathology that can mask the Lewy phenotype.

OBJECTIVE

The objective of this study was therefore to develop and validate a new clinical scale designed to detect signs of Lewy body disease, called LeSCoD for Lewy body Screening scale in Cognitive Disorders.

METHODS

128 patients who fulfilled the clinical criteria of dementia with Lewy bodies (DLB; n = 32), Alzheimer's disease (AD; n = 77) or both (n = 19) was prospectively enrolled. ¹⁸F-DOPA PET imaging and/or CSF biomarkers were available in some patients. LeSCoD scale was systematically administered and the potential correlation with ¹⁸F-DOPA PET imaging was evaluated in a subgroup of patients.

RESULTS

LeSCoD scale showed robust internal and external validity. We determined a cut-off of 10 above which the sensitivity and specificity for Lewy body disease diagnosis were 86% and 95%, respectively. The LeSCoD scale correlated with striatal dopamine uptake in ¹⁸F-DOPA PET.

CONCLUSION

LeSCoD scale is a simple and reliable tool for the evaluation of Lewy body disease in routine clinical practice, with a higher sensitivity and specificity than the existing criteria. It might be an alternative to the use of dopamine-specific imaging.

The Relationship Between the Striatal Dopaminergic Neuronal and Cognitive Function With Aging

Both cognitive function and striatal dopamine function decline by normal aging. However, the relationship among these three factors remains unclear. The aim of this study was to elucidate the association among age-related changes in the striatal dopamine transporter (DAT) and cognitive function in healthy subjects. The 30 healthy volunteers were enrolled in this research, the age ranged from 41 to 82 (64.5 ± 11.5, mean ± SD). All subjects were scanned with both T1-weighted magnetic resonance imaging (MRI) and ¹²³I-FP-CIT single-photon emission computed tomography (SPECT) images. The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) was used to evaluate cognitive function. Six spherical regions of interest (ROI) using 10 mm in diameter on the caudate nucleus, anterior putamen and posterior putamen were manually drawn on MRI image which was applied onto SPECT image. The relationship between striatal occipital ratio (SOR) values and WAIS-III subscore were analyzed by multiple regression analysis. Subscores which was significant were further analyzed by path analyses. Full intelligence quotient (IQ), verbal IQ, verbal comprehension were all positively correlated with age-adjusted striatal DAT binding (P < 0.01). Multiple regression analyses revealed that the coding digit symbol correlated with all striatal regions except for the left caudate (P < 0.04). Picture completion and right caudate, similarities and left caudate also showed a positive correlation (P < 0.04). Path analysis found that the right caudate and picture completion; the left caudate and similarities were correlated independently from age, whereas the models of coding digit symbol were not significant. These results suggest that age-based individual diversity of striatal DAT binding was associated with verbal function, and the caudate nucleus plays an important role in this association.

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.

Distinct FP-CIT PET patterns of Alzheimer's disease with parkinsonism and dementia with Lewy bodies

PURPOSE

Little is known regarding the clinical relevance or neurobiology of subtle motor disturbance in Alzheimer's disease (AD). This study aims to investigate the patterns of striatal ¹⁸F-FP-CIT uptake in patients with AD-related cognitive impairment (ADCI) with mild parkinsonism.

METHODS

We recruited 29 consecutive patients with ADCI with mild parkinsonism. All patients underwent ¹⁸F-FP-CIT PET scans and dopamine transporter (DAT) availability in striatal subregions (anterior/posterior caudate, anterior/posterior putamen, ventral putamen, ventral striatum) was quantified. Additionally, 32 patients with dementia with Lewy bodies (DLB) and 21 healthy controls were included to perform inter-group comparative analyses of the striatal DAT availability. The discriminatory power of striatal DAT availability to differentiate ADCI from DLB was assessed using receiver operating characteristics (ROC) analyses. The Spearman's correlation coefficient was calculated to assess the relationship between motor severity and DAT availability in striatal subregions.

RESULTS

Patients with ADCI with mild parkinsonism exhibited decreased DAT availability in the caudate that was intermediate between healthy controls and patients with DLB. The DAT availability in other striatal subregions, including the posterior putamen, did not differ between the ADCI with parkinsonism and healthy control groups. The ROC analysis showed that DAT availability of all striatal subregions, especially the whole striatum, had a fair discriminatory power. Parkinsonian motor severity did not correlate with the striatal DAT availability in ADCI with parkinsonism.

CONCLUSIONS

The present study demonstrated that patients with ADCI with mild parkinsonism had distinct DAT scan patterns and suggests that parkinsonism is associated with the extranigral source of pathology.

Monoamines and their Derivatives on GPCRs: Potential Therapy for Alzheimer's Disease

Albeit cholinergic depletion remains the key event in Alzheimer's Disease (AD), recent information describes stronger links between monoamines (trace amines, catecholamines, histamine, serotonin, and melatonin) and AD than those known in the past century. Therefore, new drug design strategies focus efforts to translate the scope on these topics and to offer new drugs which can be applied as therapeutic tools in AD. In the present work, we reviewed the state-of-art regarding genetic, neuropathology and neurochemistry of AD involving monoamine systems. Then, we compiled the effects of monoamines found in the brain of mammals as well as the reported effects of their derivatives and some structure-activity relationships. Recent derivatives have triggered exciting effects and pharmacokinetic properties in both murine models and humans. In some cases, the mechanism of action is clear, essentially through the interaction on G-protein-coupled receptors as revised in this manuscript. Additional mechanisms are inhibition of enzymes for their biotransformation, regulation of free-radicals in the central nervous system and others for the effects on Tau phosphorylation or amyloid-beta accumulation. All these data make the monoamines and their derivatives attractive potential elements for AD 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.

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.

Comparison of diagnostic utility of semi-quantitative analysis for DAT-SPECT for distinguishing DLB from AD

PURPOSE

It is widely known that there is low striatal ¹²³I-FP-CIT dopamine transporter single photon emission computed tomography (DAT-SPECT) uptake in patients with dementia with Lewy bodies (DLB). However, a consistent quantitative evaluation method for DAT-SPECT has not yet been established. There are two semi-quantitative software packages for DAT-SPECT available in Japan, namely, DaTView and DaTQUANT. The aim of this study was to identify which of these is superior for distinguishing DLB from AD. Moreover, we aimed to identify which region of the striatum is more suitable for distinguishing DLB from AD.

METHODS

Patients with Alzheimer's disease (AD) (n=95) and patients with DLB (n=133) who underwent DAT-SPECT were enrolled. DaTView and DaTQUANT were used as semi-quantitative analysis tools for DAT-SPECT.

RESULTS

There were significant correlations in DAT uptake between DaTView and entire regions by DaTQUANT. There was no significant difference in diagnostic accuracy between DaTView and DaTQUANT except in the posterior putamen by DaTQUANT.

CONCLUSIONS

For distinguishing DLB from AD, both of DaTView and DaTQUANT software are useful. Moreover, assessing the DAT uptake in entire striatum by DaTView might be sufficient for distinguishing DLB from AD.