A comparison of FDG-PET and blood flow SPECT in the diagnosis of neurodegenerative dementias: a systematic review

The Association of Ancillary Diagnostic Tests With Outcome in Dementia

OBJECTIVES

Dementia is a clinical diagnosis without curative treatment. It is uncertain whether ancillary testing is beneficial for patients. This study investigates the association between use of diagnostic tests and time to poor outcome and health care costs.

DESIGN

Nationwide register-based cohort study using health care reimbursement data in the Netherlands.

SETTING AND PARTICIPANTS

All Dutch hospitals, including 13,312 patients diagnosed with dementia in 2018.

METHODS

Diagnostic testing included computed tomography or magnetic resonance imaging (CT/MRI), neuropsychological examination (NPE), nuclear imaging (PET/SPECT), electroencephalography (EEG), and cerebrospinal fluid (CSF) testing. We compared time to poor outcome (institutionalization or death) and costs per month from 2018 to 2021 between those who underwent a specific diagnostic test in previous years to controls, propensity score matched for age, sex, type of hospital, and comorbidity.

RESULTS

Time to poor outcome in those who underwent CT/MRI, EEG, or CSF testing was similar to those who did not, but was longer for those who underwent NPE. Time to poor outcome was shorter in patients who underwent PET/SPECT. Patients who underwent CSF testing or PET/SPECT had higher mean total health care costs as compared to controls (CSF €248, 95% CI 64-433; PET/SPECT: €315, 95% CI 179-451). NPE during the diagnostic trajectory was associated with lower total health care cost (-€127, 95% CI -62, -193).

CONCLUSION AND IMPLICATIONS

NPE was associated with longer time to poor outcome and lower health care costs, potentially due to confounding by indication. Patients who underwent neuroimaging (CT, MRI, SPECT/PET), CSF testing, or EEG for dementia diagnostics did not experience a longer time to poor outcome or lower health care costs. This emphasizes the importance of clinical examination as anchor for the diagnosis of dementia.

The role of brain perfusion SPECT in the diagnosis of frontotemporal dementia: A systematic review

BACKGROUND AND PURPOSE

Frontotemporal dementia (FTD) is the second most common cause of presenile dementia. The clinical distinction between FTD, Alzheimer's disease (AD), and other dementias is a clinical challenge. Brain perfusion SPECT may contribute to the diagnosis of FTD, but its value is unclear.

METHODS

We performed a systematic review to investigate the diagnostic accuracy of the brain SPECT in (1) distinguishing FTD from AD and other dementias and (2) differentiating FTD variants.

RESULTS

Overall, 391 studies were retrieved on the initial search and 35 studies composed the final selection, comprising a total number of 3142 participants of which 1029 had FTD. The sensitivity and the specificity for the differential diagnosis of FTD versus AD ranged from 56% to 88% and from 51% to 93%, respectively. SPECT is not superior to the clinical method of diagnosis, but the combination of SPECT with clinical data seems to improve the diagnostic accuracy.

CONCLUSION

Brain perfusion SPECT has a limited value in the diagnostic framework of FTD. SPECT can be performed when FDG-PET is not available. SPECT is recommended only for selected cases when the diagnosis is challenging using conventional methods.

Early-phase amyloid PET reproduces metabolic signatures of cognitive decline in Parkinson's disease

INTRODUCTION

Recent work suggests that amyloid beta (Aβ) positron emission tomography (PET) tracer uptake shortly after injection ("early phase") reflects brain metabolism and perfusion. We assessed this modality in a predominantly amyloid-negative neurodegenerative condition, Parkinson's disease (PD), and hypothesized that early-phase 18F-florbetaben (eFBB) uptake would reproduce characteristic hypometabolism and hypoperfusion patterns associated with cognitive decline in PD.

METHODS

One hundred fifteen PD patients across the spectrum of cognitive impairment underwent dual-phase Aβ PET, structural and arterial spin labeling (ASL) magnetic resonance imaging (MRI), and neuropsychological assessments. Multiple linear regression models compared eFBB uptake to cognitive performance and ASL MRI perfusion.

RESULTS

Reduced eFBB uptake was associated with cognitive performance in brain regions previously linked to hypometabolism-associated cognitive decline in PD, independent of amyloid status. Furthermore, eFBB uptake correlated with cerebral perfusion across widespread regions.

DISCUSSION

EFBB uptake is a potential surrogate measure for cerebral perfusion/metabolism. A dual-phase PET imaging approach may serve as a clinical tool for assessing cognitive impairment.

Highlights

Images taken at amyloid beta (Aβ) positron emission tomography tracer injection may reflect brain perfusion and metabolism.Parkinson's disease (PD) is a predominantly amyloid-negative condition.Early-phase florbetaben (eFBB) in PD was associated with cognitive performance.eFBB uptake reflects hypometabolism-related cognitive decline in PD.eFBB correlated with arterial spin labeling magnetic resonance imaging measured cerebral perfusion.eFBB distinguished dementia from normal cognition and mild cognitive impairment.Findings were independent of late-phase Aβ burden.Thus, eFBB may serve as a surrogate measure for brain metabolism/perfusion.

Functional near-infrared spectroscopy in elderly patients with four types of dementia

BACKGROUND

Functional near-infrared spectroscopy (fNIRS) is commonly used to study human brain function by measuring the hemodynamic signals originating from cortical activation and provides a new noninvasive detection method for identifying dementia.

AIM

To investigate the fNIRS imaging technique and its clinical application in differential diagnosis of subtype dementias including frontotemporal lobe dementia, Lewy body dementia, Parkinson’s disease dementia (PDD) and Alzheimer’s disease (AD).

METHODS

Four patients with different types of dementia were examined with fNIRS during two tasks and a resting state. We adopted the verbal fluency task, working memory task and resting state task. Each patient was compared on the same task. We conducted and analyzed the fNIRS data using a general linear model and Pearson’s correlation analysis.

RESULTS

Compared with other types of dementias, fNIRS showed the left frontotemporal and prefrontal lobes to be poorly activated during the verbal fluency task in frontotemporal dementia. In Lewy body dementia, severe asymmetry of prefrontal lobes appeared during both verbal fluency and working memory tasks, and the patient had low functional connectivity during a resting state. In PDD, the patient’s prefrontal cortex showed lower excitability than the temporal lobe during the verbal fluency task, while the prefrontal cortex showed higher excitability during the working memory task. The patient with AD showed poor prefrontal and temporal activation during the working memory task, and more activation of frontopolar instead of the dorsolateral prefrontal cortex.

CONCLUSION

Different hemodynamic characteristics of four types of dementia (as seen by fNIRS imaging) provides evidence that fNIRS can serve as a potential tool for the diagnosis between dementia subtypes.

Advanced Overview of Biomarkers and Techniques for Early Diagnosis of Alzheimer's Disease

The development of early non-invasive diagnosis methods and identification of novel biomarkers are necessary for managing Alzheimer's disease (AD) and facilitating effective prognosis and treatment. AD has multi-factorial nature and involves complex molecular mechanism, which causes neuronal degeneration. The primary challenges in early AD detection include patient heterogeneity and lack of precise diagnosis at the preclinical stage. Several cerebrospinal fluid (CSF) and blood biomarkers have been proposed to show excellent diagnosis ability by identifying tau pathology and cerebral amyloid beta (Aβ) for AD. Intense research endeavors are being made to develop ultrasensitive detection techniques and find potent biomarkers for early AD diagnosis. To mitigate AD worldwide, understanding various CSF biomarkers, blood biomarkers, and techniques that can be used for early diagnosis is imperative. This review attempts to provide information regarding AD pathophysiology, genetic and non-genetic factors associated with AD, several potential blood and CSF biomarkers, like neurofilament light, neurogranin, Aβ, and tau, along with biomarkers under development for AD detection. Besides, numerous techniques, such as neuroimaging, spectroscopic techniques, biosensors, and neuroproteomics, which are being explored to aid early AD detection, have been discussed. The insights thus gained would help in finding potential biomarkers and suitable techniques for the accurate diagnosis of early AD before cognitive dysfunction.

Combining Neuropsychological Assessment with Neuroimaging to Distinguish Early-Stage Alzheimer's Disease from Frontotemporal Lobar Degeneration in Non-Western Tonal Native Language-Speaking Individuals Living in Taiwan: A Case Series

Neuropsychological tests (NPTs), which are routinely used in clinical practice for assessment of dementia, are also considered to be essential for differential diagnosis of Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), especially the behavioral variants of frontotemporal dementia (bvFTD) and primary progressive aphasia (PPA) at their initial clinical presentations. However, the heterogeneous features of these diseases, which have many overlapping signs, make differentiation between AD and FTLD highly challenging. Moreover, NPTs were primarily developed in Western countries and for native speakers of non-tonal languages. Hence, there is an ongoing dispute over the validity and reliability of these tests in culturally different and typologically diverse language populations. The purpose of this case series was to examine which of the NPTs adjusted for Taiwanese society may be used to distinguish these two diseases. Since AD and FTLD have different effects on individuals' brain, we combined NPTs with neuroimaging. We found that participants diagnosed with FTLD had lower scores in NPTs assessing language or social cognition than AD participants. PPA participants also had lower measures in the Free and Cued Selective Reminding Test than those diagnosed with bvFTD, while bvFTD participants showed poorer performances in the behavioral measures than PPA participants. In addition, the initial diagnosis was supported by the standard one-year clinical follow-up.

Brain PET Imaging: Frontotemporal Dementia

Brain PET adds value in diagnosing neurodegenerative disorders, especially frontotemporal dementia (FTD) due to its syndromic presentation that overlaps with a variety of other neurodegenerative and psychiatric disorders. 18F-FDG-PET has improved sensitivity and specificity compared with structural MR imaging, with optimal diagnostic results achieved when both techniques are utilized. PET demonstrates superior sensitivity compared with SPECT for FTD diagnosis that is primarily a supplement to other imaging and clinical evaluations. Tau-PET and amyloid-PET primary use in FTD diagnosis is differentiation from Alzheimer disease, although these methods are limited mainly to research settings.

Follow-Up of a Cohort of Patients with Post-Acute COVID-19 Syndrome in a Belgian Family Practice

Fifty-five patients who suffered from COVID-19, who were still very ill after several months, with extreme fatigue, effort exhaustion, brain fog, anomia, memory disorder, anosmia, dysgeusia, and other multi-systemic health problems have been followed in a family practice setting between May 2021 and July 2022. Data extracted from the medical records of the 55 patients (40 women), mean age 42.4 (12 to 79 years), and a qualitative study of 6 of them using a semi-open-ended questionnaire allowed to highlight the clinical picture described by WHO as post-acute COVID-19 syndrome (PACS) also known as long COVID. We used brain single-photon emission computed tomography (SPECT-CT) in thirty-two patients with a high severity index and a highly impaired functional status, demonstrating vascular encephalopathy in twenty nine patients and supporting the hypothesis of a persistent cerebral vascular flow disorder in post COVID-19 condition. The patients will benefit from the consortium COVID Human Genetic Effort (covidhge.com) to explore the genetic and immunological basis of their problem, as 23/55 cases don't have immunological certainty of a COVID-19 infection. There is no known verified treatment. Analyzing the data from the first 52 patients, three categories of patients emerged over time: 16 patients made a full recovery after 6-8 months, 15 patients were able to return to life and work after 12-18 months with some sequelae, both groups being considered cured. In the third group, 21 patients are still very ill and unable to resume their work and life after 18 months. The biopsychosocial consequences on patients' lives are severe and family doctors are left out in the cold. It is necessary to test the reproducibility of this description, conducted on a small number of patients. Nevertheless, identifying, monitoring and supporting these patients is a necessity in family medicine.

The Legacy of the TTASAAN Report-Premature Conclusions and Forgotten Promises: A Review of Policy and Practice Part I

Brain perfusion single photon emission computed tomography (SPECT) scans were initially developed in 1970's. A key radiopharmaceutical, hexamethylpropyleneamine oxime (HMPAO), was originally approved in 1988, but was unstable. As a result, the quality of SPECT images varied greatly based on technique until 1993, when a method of stabilizing HMPAO was developed. In addition, most SPECT perfusion studies pre-1996 were performed on single-head gamma cameras. In 1996, the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology (TTASAAN) issued a report regarding the use of SPECT in the evaluation of neurological disorders. Although the TTASAAN report was published in January 1996, it was approved for publication in October 1994. Consequently, the reported brain SPECT studies relied upon to derive the conclusions of the TTASAAN report largely pre-date the introduction of stabilized HMPAO. While only 12% of the studies on traumatic brain injury (TBI) in the TTASAAN report utilized stable tracers and multi-head cameras, 69 subsequent studies with more than 23,000 subjects describe the utility of perfusion SPECT scans in the evaluation of TBI. Similarly, dementia SPECT imaging has improved. Modern SPECT utilizing multi-headed gamma cameras and quantitative analysis has a sensitivity of 86% and a specificity of 89% for the diagnosis of mild to moderate Alzheimer's disease-comparable to fluorodeoxyglucose positron emission tomography. Advances also have occurred in seizure neuroimaging. Lastly, developments in SPECT imaging of neurotoxicity and neuropsychiatric disorders have been striking. At the 25-year anniversary of the publication of the TTASAAN report, it is time to re-examine the utility of perfusion SPECT brain imaging. Herein, we review studies cited by the TTASAAN report vs. current brain SPECT imaging research literature for the major indications addressed in the report, as well as for emerging indications. In Part II, we elaborate technical aspects of SPECT neuroimaging and discuss scan interpretation for the clinician.

A New Way Forward: How Brain SPECT Imaging Can Improve Outcomes and Transform Mental Health Care Into Brain Health Care

In the past three decades, brain single-photon-emission-computed-tomography (SPECT) imaging has garnered a significant, evidence-based foundation for a wide array of indications relevant to the field of clinical psychiatry, including dementia, traumatic brain injuries, seizures, cerebrovascular disease, complex neuropsychiatric presentations, and treatment-resistant disorders. In clinical psychiatric practice, however, SPECT remains underutilized. Only a small percentage of psychiatric clinicians use brain imaging technology. In this article, the authors provide a rationale for shifting the paradigm to one that includes broader use of SPECT in the clinical psychiatric setting, primarily for patients with complex conditions. This paper will outline seven specific clinical applications. Adding neuroimaging tools like SPECT to day-to-day clinical practice can help move psychiatry forward by transforming mental health care, which can be stigmatizing and often shunned by the general public, to brain health care, which the authors argue will be more likely to be embraced by a larger group of people in need.

Head-to-head comparison of cerebral blood flow single-photon emission computed tomography and 18 F-fluoro-2-deoxyglucose positron emission tomography in the diagnosis of Alzheimer disease

BACKGROUND

Clinical diagnosis of Alzheimer disease (AD) is only 70% accurate. Reduced cerebral blood flow (CBF) and metabolism in parieto-temporal and posterior cingulate cortex may assist diagnosis. While widely accepted that ¹⁸ F-fluoro-2-deoxyglucose positron emission tomography (¹⁸ F-FDG PET) has superior accuracy to CBF-SPECT for AD, there are very limited head-to-head data from clinically relevant populations and these studies relied on clinical diagnosis as the reference standard.

AIMS

To compare directly the accuracy of CBF-SPECT and ¹⁸ F-FDG PET in patients referred for diagnostic studies in detecting β-amyloid PET confirmed AD.

METHODS

A total of 126 patients, 56% with mild cognitive impairment and 44% with dementia, completed both CBF-SPECT and ¹⁸ F-FDG PET as part of their diagnostic assessment, and subsequently underwent β-amyloid PET for research purposes. Transaxial slices and Neurostat 3D-SSP analyses of ¹⁸ F-FDG PET and CBF-SPECT scans were independently reviewed by five nuclear medicine clinicians blinded to all other data. Operators selected the most likely diagnosis and their diagnostic confidence. Accuracy analysis used final diagnosis incorporating β-amyloid PET as the reference standard.

RESULTS

Clinicians reported high diagnostic confidence in 83% of ¹⁸ F-FDG PET compared to 67% for CBF-SPECT (P = 0.001). All reviewers showed individually higher accuracy using ¹⁸ F-FDG PET. Based on majority read, the combined area under the receiver operating characteristic curve in diagnosing AD was 0.71 for ¹⁸ F-FDG PET and 0.61 for CBF-SPECT (P = 0.02). The sensitivity of ¹⁸ F-FDG PET and CBF-SPECT was 76% versus 43% (P < 0.001), while specificity was 74% versus 83% (P = 0.45).

CONCLUSIONS

¹⁸ F-FDG PET is superior to CBF-SPECT in detecting AD among patients referred for the assessment of cognitive impairment.

Biomarkers of Alzheimer's Disease and Cerebrovascular Lesions and Clinical Progression in Patients with Subjective Cognitive Decline: A Systematic Review

BACKGROUND

Early identification of Alzheimer's disease (AD) may be extremely beneficial for delaying disease progression. Subjective cognitive decline (SCD) may be an early indicator of AD pathology. Not all individuals with SCD will eventually develop AD, making it critical to identify biomarkers during the SCD stage which indicate likely clinical progression.

OBJECTIVE

The present review aims to summarize available data on structural MRI and cerebrospinal fluid (CSF) biomarkers and their association with clinical progression to mild cognitive impairment (MCI) or AD in people with SCD.

METHODS

Database searches were conducted using Embase and PubMed until June 2020. Longitudinal studies assessing biomarkers in individuals with SCD and assessing clinical progression to MCI/AD were included. Two assessors performed data extraction and assessed the risk of bias in the included studies. Data were synthesized narratively.

RESULTS

An initial search identified 1,065 papers; after screening and review 14 studies were included. Sample size of the included studies ranged from 28-674, mean age was 60.0-68.6 years, and 10.2%-52%of participants converted to MCI/AD. Lower levels of CSF Aβ 42 were consistently associated with clinical progression. Combination measures identifying an AD-like profile of Aβ 42 and tau levels were strongly associated with clinical progression. Biomarkers identified with structural MRI were less conclusive, as some studies found significant associations while others did not.

CONCLUSION

Biomarkers may be able to predict clinical progression in those with cognitive complaints. Aβ 42, or combinations of Aβ 42 and tau may be useful biomarkers in identifying individuals with SCD who will progress to MCI/AD.

Cerebral glucose metabolism in bipolar disorder: A voxel-based meta-analysis of positron emission tomography studies

BACKGROUND

Previous positron emission tomography studies have reported the changes of cerebral glucose metabolism in bipolar disorder. However, the findings across studies remain controversial, containing differing results.

METHODS

A systematic literature search of the PubMed, Embase, Cochrane Library, and Web of Science databases was conducted. We conducted a voxel-wide meta-analysis of cerebral glucose metabolism studies, using the seed-based mapping approach, in patients with bipolar disorder (BD).

RESULTS

We identified 7 studies suitable for inclusion, which included a total of 126 individuals with BD and 160 healthy controls. The most consistent and robust findings were an increase in cerebral glucose metabolism in the right precentral gyrus and a decrease in the left superior temporal gyrus, left middle temporal gyrus, and cerebellum. Additionally, the sex distribution and illness duration had significant moderating effects on cerebral glucose metabolism alterations.

CONCLUSIONS

Cerebral glucose metabolism alterations in these brain regions are likely to reflect the disease-related functional abnormalities such as emotion and cognition. These findings contribute to a better understanding of the neurobiological underpinnings of bipolar disorder.

LIMITATIONS

This study was done at a study level and cannot be addressed at the patient level. Subgroup analysis of BD I and BD II is not possible due to limited literature data.

Imaging Familial and Sporadic Neurodegenerative Disorders Associated with Parkinsonism

In this paper, the structural and functional imaging changes associated with sporadic and genetic Parkinson's disease and atypical Parkinsonian variants are reviewed. The role of imaging for supporting diagnosis and detecting subclinical disease is discussed, and the potential use and drawbacks of using imaging biomarkers for monitoring disease progression is debated. Imaging changes associated with nonmotor complications of PD are presented. The similarities and differences in imaging findings in Lewy body dementia, Parkinson's disease dementia, and Alzheimer's disease are discussed.

Differentiating dementia with Lewy bodies from Alzheimer's disease and Parkinson's disease dementia: an update on imaging modalities

Dementia with Lewy bodies is the second most common cause of neurodegenerative dementia after Alzheimer's disease. Dementia with Lewy bodies can provide a diagnostic challenge due to the frequent overlap of clinical signs with other neurodegenerative conditions, namely Parkinson's disease dementia, and Alzheimer's disease. Part of this clinical overlap is due to the neuropathological overlap. Dementia with Lewy bodies is characterized by the accumulation of aggregated α-synuclein protein in Lewy bodies, similar to Parkinson's disease and Parkinson's disease dementia. However, it is also frequently accompanied by aggregation of amyloid-beta and tau, the pathological hallmarks of Alzheimer's disease. Neuroimaging is central to the diagnostic process. This review is an overview of both established and evolving imaging methods that can improve diagnostic accuracy and improve management of this disorder.

CCCDTD5: Clinical role of neuroimaging and liquid biomarkers in patients with cognitive impairment

Since 1989, four Canadian Consensus Conferences on the Diagnosis and Treatment of Dementia (CCCDTDs) have provided evidence-based dementia diagnostic and treatment guidelines for Canadian clinicians and researchers. We present the results from the Neuroimaging and Fluid Biomarkers Group of the 5th CCCDTD (CCCDTD5), which addressed topics chosen by the steering committee to reflect advances in the field and build on our previous guidelines. Recommendations on Imaging and Fluid Biomarker Use from this Conference cover a series of different fields. Prior structural imaging recommendations for both computerized tomography (CT) and magnetic resonance imaging (MRI) remain largely unchanged, but MRI is now more central to the evaluation than before, with suggested sequences described here. The use of visual rating scales for both atrophy and white matter anomalies is now included in our recommendations. Molecular imaging with [18F]-fluorodeoxyglucose ([18F]-FDG) Positron Emisson Tomography (PET) or [99mTc]-hexamethylpropyleneamine oxime/ethylene cysteinate dimer ([99mTc]-HMPAO/ECD) Single Photon Emission Tomography (SPECT), should now decidedly favor PET. The value of [18F]-FDG PET in the assessment of neurodegenerative conditions has been established with greater certainty since the previous conference, and it has now been recognized as a useful biomarker to establish the presence of neurodegeneration by a number of professional organizations around the world. Furthermore, the role of amyloid PET has been clarified and our recommendations follow those from other groups in multiple countries. SPECT with [123I]-ioflupane (DaTscanTM) is now included as a useful study in differentiating Alzheimer's disease (AD) from Lewy body disease. Finally, liquid biomarkers are in a rapid phase of development and, could lead to a revolution in the assessment AD and other neurodegenerative conditions at a reasonable cost. We hope these guidelines will be useful for clinicians, researchers, policy makers, and the lay public, to inform a current and evidence-based approach to the use of neuroimaging and liquid biomarkers in clinical dementia evaluation and management.

Neuroimaging in Frontotemporal Lobar Degeneration: Research and Clinical Utility

Frontotemporal lobar dementia (FTLD) is a clinically and pathologically complex disease. Advances in neuroimaging techniques have provided a specialized set of tools to investigate underlying pathophysiology and identify clinical biomarkers that aid in diagnosis, prognostication, monitoring, and identification of appropriate endpoints in clinical trials. In this chapter, we review data discussing the utility of neuroimaging biomarkers in sporadic FTLD, with an emphasis on current and future clinical applications. Among those modalities readily utilized in clinical settings, T1-weighted structural magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) are best supported in differential diagnosis and as targets for clinical trial endpoints. However, a number of nonclinical neuroimaging modalities, including diffusion tensor imaging and resting-state functional connectivity MRI, show promise as biomarkers to predict progression and as clinical trial endpoints. Other neuroimaging modalities, including amyloid PET, Tau PET, and arterial spin labeling MRI, are also discussed, though more work is required to establish their utility in FTLD in clinical settings.

PET and SPECT Imaging of the Brain: History, Technical Considerations, Applications, and Radiotracers

Advances in nuclear medicine have revolutionized our ability to accurately diagnose patients with a wide array of neurologic pathologies and provide appropriate therapy. The development of new radiopharmaceuticals has made possible the identification of regional differences in brain tissue composition and metabolism. In addition, the evolution of 3-dimensional molecular imaging followed by fusion with computed tomography and magnetic resonance imaging have allowed for more precise localization of pathologies. This review will introduce single photon emission computed tomography and positron emission tomographic imaging of the brain, including the history of their development, technical considerations, and a brief overview of pertinent radiopharmaceuticals and their applications.

The clinical utilities of multi-pinhole single photon emission computed tomography

Single photon emission computed tomography (SPECT) is an important imaging modality for various applications in nuclear medicine. The use of multi-pinhole (MPH) collimators can provide superior resolution-sensitivity trade-off when imaging small field-of-view compared to conventional parallel-hole and fan-beam collimators. Besides the very successful application in small animal imaging, there has been a resurgence of the use of MPH collimators for clinical cardiac and brain studies, as well as other small field-of-view applications. This article reviews the basic principles of MPH collimators and introduces currently available and proposed clinical MPH SPECT systems.

Neuroimaging in Dementia: A Brief Review

Dementia is a clinical syndrome that manifests itself with impairment in cognitive functions owing to various neurodegenerative etiologies causing severe disability in the older population. Although the diagnosis is largely dependent on clinical examination, biomarkers can significantly aid in early diagnosis of dementia, especially in those without any clinical evidence of neurocognitive impairment. These biomarkers can be discovered in cerebrospinal fluid (CSF) or can be assessed by neuroimaging. Our goal was to discuss and assess the role of different neuroimaging techniques in the early diagnosis of relatively common etiologies of dementia. We used PubMed as search engines to look for helpful articles; most of the sources used were peer reviewed. We discussed the utility of various neuroimaging techniques, such CT, MRI, positron emission tomography (PET) scan, and single-photon emission computed tomography (SPECT), in the diagnosis of dementia. We concluded that various modern neuroimaging techniques prove to be very helpful in early identification, diagnosis, and differentiation between subtypes. However, the actual clinical utility of these tests in terms of their cost-effectivity and availability remains to be seen. Ongoing research is required to further develop biomarkers for early identification and monitor the progression of different etiologies of dementia.

Functional near-infrared spectroscopy reveals decreased resting oxygenation levels and task-related oxygenation changes in mild cognitive impairment and dementia: A systematic review

Nuclear medicine and functional magnetic resonance imaging studies have shown that mild cognitive impairment (MCI) and dementia, including Alzheimer's disease (AD), are characterized by changes in cerebral blood flow. This article reviews the application of an alternative method, functional near-infrared spectroscopy (fNIRS), to the study of cerebral oxygenation changes in MCI and dementia. We synthesized 36 fNIRS studies that examined hemodynamic changes during both the resting state and the execution of tasks of word retrieval, memory, motor control, and visuospatial perception in MCI and dementia. This qualitative review reveals that (amnestic) MCI and AD patients have disrupted frontal and long-range connectivity in the resting state compared to individuals with normal cognition (NC). These patients also exhibit reduced frontal oxygenation changes in various cognitive domains. The review also shows that disrupted connectivity and decreased frontal oxygenation levels/changes are more severe in AD than in (amnestic) MCI, confirming that MCI is an intermediate stage between NC and dementia. Thus, there is reduced resting frontal perfusion, which is greater than expected for age, and a lack of frontal compensatory responses to functional decline across cognitive operations (i.e., word retrieval and memory functioning) in MCI and AD. These indices might potentially serve as perfusion- or oxygenation-based biomarkers for MCI/dementia. To expand the utility of fNIRS for MCI and dementia, further studies that measure tissue oxygenation in a wider range of brain regions and cognitive domains, compare different MCI and dementia types, and correlate changes in cerebral oxygenation over time with disease progression are needed.

Evaluating 2-[18F]FDG-PET in differential diagnosis of dementia using a data-driven decision model

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Addition of 2-[¹⁸F]FDG-PET to common diagnostic tests improved the accuracy for DLB and FTD.

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Two new 2-[¹⁸F]FDG-PET biomarkers demonstrated specific disease patterns for DLB and FTD.

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Different combinations of diagnostic tests were valuable for each subtype of dementia.

2-[¹⁸F]fluoro-2-deoxy-d-glucose positron emission tomography (2-[¹⁸F]FDG-PET) has an emerging supportive role in dementia diagnostic as distinctive metabolic patterns are specific for Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and frontotemporal dementia (FTD). Previous studies have demonstrated that a data-driven decision model based on the disease state index (DSI) classifier supports clinicians in the differential diagnosis of dementia by using different combinations of diagnostic tests and biomarkers. Until now, this model has not included 2-[¹⁸F]FDG-PET data.

The objective of the study was to evaluate 2-[¹⁸F]FDG-PET biomarkers combined with commonly used diagnostic tests in the differential diagnosis of dementia using the DSI classifier.

We included data from 259 subjects diagnosed with AD, DLB, FTD, vascular dementia (VaD), and subjective cognitive decline from two independent study cohorts. We also evaluated three 2-[¹⁸F]FDG-PET biomarkers (anterior vs. posterior index (API-PET), occipital vs. temporal index, and cingulate island sign) to improve the classification accuracy for both FTD and DLB.

We found that the addition of 2-[¹⁸F]FDG-PET biomarkers to cognitive tests, CSF and MRI biomarkers considerably improved the classification accuracy for all pairwise comparisons of DLB (balanced accuracies: DLB vs. AD from 64% to 77%; DLB vs. FTD from 71% to 92%; and DLB vs. VaD from 71% to 84%). The two 2-[¹⁸F]FDG-PET biomarkers, API-PET and occipital vs. temporal index, improved the accuracy for FTD and DLB, especially as compared to AD. Moreover, different combinations of diagnostic tests were valuable to differentiate specific subtypes of dementia.

In conclusion, this study demonstrated that the addition of 2-[¹⁸F]FDG-PET to commonly used diagnostic tests provided complementary information that may help clinicians in diagnosing patients, particularly for differentiating between patients with FTD, DLB, and AD.

Multiscale spatial gradient features for 18F-FDG PET image-guided diagnosis of Alzheimer's disease

BACKGROUND AND OBJECTIVE

¹⁸F-FluoroDeoxyGlucose Positron Emission Tomography (¹⁸F-FDG PET) is one of the imaging biomarkers to diagnose Alzheimer's Disease (AD). In ¹⁸F-FDG PET images, the changes of voxels' intensities reflect the differences of glucose rates, therefore voxel intensity is usually used as a feature to distinguish AD from Normal Control (NC), or at earlier stage to distinguish between progressive and stable Mild Cognitive Impairment (pMCI and sMCI). In this paper, ¹⁸F-FDG PET images are characterized in an alternative way-the spatial gradient, which is motivated by the observation that the changes of ¹⁸F-FDG rates also cause gradient changes.

METHODS

We improve Histogram of Oriented Gradient (HOG) descriptor to quantify spatial gradients, thereby achieving the goal of diagnosing AD. First, the spatial gradient of ¹⁸F-FDG PET image is computed, and then each subject is segmented into different regions by using an anatomical atlas. Second, two types of improved HOG features are extracted from each region, namely Small Scale HOG and Large Scale HOG, then some relevant regions are selected based on a classifier fed with spatial gradient features. Last, an ensemble classification framework is designed to make a decision, which considers the performance of both individual and concatenated selected regions.

RESULTS

the evaluation is done on ADNI dataset. The proposed method outperforms other state-of-the-art ¹⁸F-FDG PET-based algorithms for AD vs. NC with an accuracy, a sensitivity and a specificity values of 93.65%, 91.22% and 96.25%, respectively. For the case of pMCI vs. sMCI, the three metrics are 75.38%, 74.84% and 77.11%, which is significantly better than most existing methods. Besides, promising results are also achieved for multiple classifications under ¹⁸F-FDG PET modality.

CONCLUSIONS

¹⁸F-FDG PET images can be characterized by spatial gradient features for diagnosing AD and its early stage, and the proposed ensemble framework can enhance the classification performance.

The Use of Biomarkers and Genetic Screening to Diagnose Frontotemporal Dementia: Evidence and Clinical Implications

Within the wide range of neurodegenerative brain diseases, the differential diagnosis of frontotemporal dementia (FTD) frequently poses a challenge. Often, signs and symptoms are not characteristic of the disease and may instead reflect atypical presentations. Consequently, the use of disease biomarkers is of importance to correctly identify the patients. Here, we describe how neuropsychological characteristics, neuroimaging and neurochemical biomarkers and screening for causal gene mutations can be used to differentiate FTD from other neurodegenerative diseases as well as to distinguish between FTD subtypes. Summarizing current evidence, we propose a stepwise approach in the diagnostic evaluation. Clinical consensus criteria that take into account a full neuropsychological examination have relatively good accuracy (sensitivity [se] 75–95%, specificity [sp] 82–95%) to diagnose FTD, although misdiagnosis (mostly AD) is common. Structural brain MRI (se 70–94%, sp 89–99%) and FDG PET (se 47–90%, sp 68–98%) or SPECT (se 36–100%, sp 41–100%) brain scans greatly increase diagnostic accuracy, showing greater involvement of frontal and anterior temporal lobes, with sparing of hippocampi and medial temporal lobes. If these results are inconclusive, we suggest detecting amyloid and tau cerebrospinal fluid (CSF) biomarkers that can indicate the presence of AD with good accuracy (se 74–100%, sp 82–97%). The use of P-tau₁₈₁ and the Aβ_1–42/Aβ_1–40 ratio significantly increases the accuracy of correctly identifying FTD vs. AD. Alternatively, an amyloid brain PET scan can be performed to differentiate FTD from AD. When autosomal dominant inheritance is suspected, or in early onset dementia, mutation screening of causal genes is indicated and may also be offered to at-risk family members. We have summarized genotype–phenotype correlations for several genes that are known to cause familial frontotemporal lobar degeneration, which is the neuropathological substrate of FTD. The genes most commonly associated with this disease (C9orf72, MAPT, GRN, TBK1) are discussed, as well as some less frequent ones (CHMP2B, VCP). Several other techniques, such as diffusion tensor imaging, tau PET imaging and measuring serum neurofilament levels, show promise for future implementation as diagnostic biomarkers.

The Cingulate Island Sign on FDG-PET vs. IMP-SPECT to Assess Mild Cognitive Impairment in Alzheimer's Disease vs. Dementia with Lewy Bodies

BACKGROUND AND PURPOSE

The cingulate island sign (CIS) on ¹⁸ F-fluorodeoxyglucose positron emission tomography (FDG-PET); ie, the relative preservation of mid-posterior cingulate cortex metabolism, is a supportive biomarker in the diagnostic criteria for dementia with Lewy bodies (DLB). However, limited information is currently available on the diagnostic value of the CIS on FDG-PET or ¹²³ I-iodoamphetamine single-photon emission computed tomography (IMP-SPECT) for differentiating between mild cognitive impairment (MCI) due to Alzheimer's disease (AD) (MCI-AD) and MCI due to DLB (MCI-DLB).

METHODS

We examined the CIS ratio in 9 AD patients, 9 DLB patients, 8 patients with MCI-AD, and 9 patients with MCI-DLB using FDG-PET and IMP-SPECT. The CIS ratio was calculated using NEUROSTAT software.

RESULTS

In the dementia groups, a receiver operating characteristic analysis of the CIS ratio showed significant accuracy for differentiating between AD and DLB on FDG-PET and IMP-SPECT. In the MCI groups, only the FDG-PET derived CIS ratio displayed significant accuracy for differentiating between AD and DLB.

CONCLUSIONS

The FDG-PET and IMP-SPECT derived CIS ratios are both useful for differentiating between AD and DLB. The FDG-PET derived CIS ratio is more valuable than the IMP-SPECT derived CIS ratio for differential diagnosis in patients with MCI. A larger study is needed to confirm these results.

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.

Single-photon emission computed tomography (SPECT) perfusion and neuropsychological performance in mild cognitive impairment

Single-photon emission computed tomography (SPECT) is an affordable neuroimaging technique that measures cerebral perfusion and has been utilized repeatedly in aging populations. However, we are aware of no studies to date examining relationships between SPECT imaging and comprehensive neuropsychological evaluations in a clinical sample of patients with mild cognitive impairment (MCI). Participants were 124 older adults with MCI (age, M = 75.07 years, SD = 7.65; years of education, M = 14.03, SD = 3.09; 60.2% female) who underwent neuropsychological evaluations and brain SPECT scans as part of their routine clinical care. Based on SPECT interpretations, participants were grouped by suspected etiology (i.e., the neuroradiologists noted that hypoperfusion patterns were most consistent with Alzheimer's disease, AD; frontotemporal lobar degeneration, FTLD; or other disease processes) and regional hypoperfusion (e.g., frontal, temporal, right/left hemisphere). Neuropsychological tests were grouped into domain scores (i.e., attention/processing speed, language, visuospatial, memory, executive; verbal/nonverbal). Consistent with a priori predictions, patients with an AD pattern of hypoperfusion scored lower than comparison groups on the attention/processing speed (partial χ² = 0.10) and memory (partial χ² = 0.07) composites. More patients with the AD-hypoperfusion signal met criteria for amnestic MCI (82%) than did those with a non-AD pattern (70%); this result approached statistical significance (p = .07). Contrary to hypotheses, patients whose SPECT scans were most consistent with FTLD did not underperform on the executive composite, and most regional analyses were nonsignificant. When integrating SPECT data into their clinical conceptualizations of MCI, neuropsychologists should place more weight on AD patterns of hypoperfusion, while de-emphasizing data suggestive of FTLD or regional pathology. Alternative neurodiagnostic markers may be more informative in these instances.

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.

Amyloid deposition and CBF patterns predict conversion of mild cognitive impairment to dementia

Mild cognitive impairment (MCI) can include the transition from a normal state to dementia. To explore biomarkers for the development of dementia, we performed an 18-month follow-up study in 28 patients with amnestic MCI. Amyloid deposition was examined using PiB PET, and cerebral blood flow (CBF) was examined using SPECT. Cognitive function was periodically assessed. The rate of conversion to dementia was higher in the PiB-positive/equivocal group (74%) than in the PiB-negative group (33%) (p = 0.041). Perfusion SPECT was performed in 16 patients. MCI patients with an AD-characteristic pattern of reduced CBF had a higher PiB-positive/equivocal rate (82%) than those with a non-AD pattern (20%) (p = 0.018), and patients with an AD pattern had a higher conversion rate (82%) than those with a non-AD pattern (40%) (p = 0.094). Clinically, all PiB-positive converters were diagnosed as having Alzheimer's disease (AD), whereas PiB-negative converters were thought to have some form of dementia other than AD. Amyloid PET is useful for predicting conversion to AD in MCI patients. A pattern analysis of perfusion SPECT findings might also be helpful for predicting conversion to AD, but with a lower specificity.

Positron Emission Tomography and Single-Photon Emission Computed Tomography in Neurology

PURPOSE OF REVIEW

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are now available for routine clinical applications in neurology. This article discusses their diagnostic use in dementia, brain tumors, epilepsy, parkinsonism, cerebrovascular disease, and traumatic brain injury.

RECENT FINDINGS

Neuromolecular imaging, also known as nuclear neurology, involves clinical imaging of both basal regional physiology (perfusion, metabolism, and transport mechanisms) and specific neurochemical physiology (currently, only the dopamine transporter). This article serves as an introduction to neuromolecular imaging, reviewing the literature supplemented by the author's experience.

SUMMARY

Neurologic PET and SPECT are no longer restricted to the research realm. These modalities have high diagnostic accuracy.

Support vector machine-based classification of neuroimages in Alzheimer's disease: direct comparison of FDG-PET, rCBF-SPECT and MRI data acquired from the same individuals

Objective:

To conduct the first support vector machine (SVM)-based study comparing the diagnostic accuracy of T1-weighted magnetic resonance imaging (T1-MRI), F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and regional cerebral blood flow single-photon emission computed tomography (rCBF-SPECT) in Alzheimer’s disease (AD).

Method:

Brain T1-MRI, FDG-PET and rCBF-SPECT scans were acquired from a sample of mild AD patients (n=20) and healthy elderly controls (n=18). SVM-based diagnostic accuracy indices were calculated using whole-brain information and leave-one-out cross-validation.

Results:

The accuracy obtained using PET and SPECT data were similar. PET accuracy was 68∼71% and area under curve (AUC) 0.77∼0.81; SPECT accuracy was 68∼74% and AUC 0.75∼0.79, and both had better performance than analysis with T1-MRI data (accuracy of 58%, AUC 0.67). The addition of PET or SPECT to MRI produced higher accuracy indices (68∼74%; AUC: 0.74∼0.82) than T1-MRI alone, but these were not clearly superior to the isolated neurofunctional modalities.

Conclusion:

In line with previous evidence, FDG-PET and rCBF-SPECT more accurately identified patients with AD than T1-MRI, and the addition of either PET or SPECT to T1-MRI data yielded increased accuracy. The comparable SPECT and PET performances, directly demonstrated for the first time in the present study, support the view that rCBF-SPECT still has a role to play in AD diagnosis.

Advances in neuroimaging in frontotemporal dementia

Frontotemporal dementia (FTD) is a clinically and neuroanatomically heterogeneous neurodegenerative disorder with multiple underlying genetic and pathological causes. Whilst initial neuroimaging studies highlighted the presence of frontal and temporal lobe atrophy or hypometabolism as the unifying feature in patients with FTD, more detailed studies have revealed diverse patterns across individuals, with variable frontal or temporal predominance, differing degrees of asymmetry, and the involvement of other cortical areas including the insula and cingulate, as well as subcortical structures such as the basal ganglia and thalamus. Recent advances in novel imaging modalities including diffusion tensor imaging, resting-state functional magnetic resonance imaging and molecular positron emission tomography imaging allow the possibility of investigating alterations in structural and functional connectivity and the visualisation of pathological protein deposition. This review will cover the major imaging modalities currently used in research and clinical practice, focusing on the key insights they have provided into FTD, including the onset and evolution of pathological changes and also importantly their utility as biomarkers for disease detection and staging, differential diagnosis and measurement of disease progression. Validating neuroimaging biomarkers that are able to accomplish these tasks will be crucial for the ultimate goal of powering upcoming clinical trials by correctly stratifying patient enrolment and providing sensitive markers for evaluating the effects and efficacy of disease-modifying therapies. This review describes the key insights provided by research into the major neuroimaging modalities currently used in research and clinical practice, including what they tell us about the onset and evolution of FTD and how they may be used as biomarkers for disease detection and staging, differential diagnosis and measurement of disease progression. This article is part of the Frontotemporal Dementia special issue.

Brain perfusion during rapid-eye-movement sleep successfully identifies amnestic mild cognitive impairment

INTRODUCTION

Prodromal markers of Alzheimer's disease (AD) have been derived from wakefulness. However, brain perfusion during rapid-eye movement (REM) sleep could be a sensitive marker of amnestic mild cognitive impairment (aMCI), as activation of REM sleep relies more on the cholinergic system.

METHODS

Eight subjects with aMCI, and 16 controls, underwent two single-photon emission computed tomography (SPECT) scans with tracer injected during REM sleep then wakefulness.

RESULTS

Perfusion in the anterior cingulate cortex was significantly decreased in aMCI cases compared to controls for both conditions. That defect was much larger and more severe in REM sleep (1795 voxels) compared to wakefulness (398 voxels), and extended to the middle cingulate cortex and the olfactory cortex. Hypoperfusion in the anterior cingulate cortex during REM sleep allowed better classification than hypoperfusion found in wakefulness (93.8 vs 81.3%).

CONCLUSION

REM sleep imaging is a valuable tool with which to identify individuals at risk of developing AD.

Cerebral Glucose Metabolism Assessment in Rat Models of Alzheimer's Disease: An 18F-FDG-PET Study

OBJECTIVE

This study was designed to detect the brain glucose metabolism in rat models of Alzheimer's disease (AD) by the application of (18)F-2-fluoro-deoxy-d-glucose positron emission tomography ((18)F-FDG-PET) and to provide new insights for the early detection of AD.

METHODS

Forty Wistar rats were randomly divided into 2 groups. Fifteen sham-operated rats were used as a control group. The remaining rats as a premodel group were intracerebroventricularly injected with ibotenic acid and were intraperitoneally injected with d-galactose, of which 15 rats were included as the experimental group. The above-mentioned 2 groups were assigned to Y-maze test and underwent (18)F-FDG-PET scanning. Positron emission tomography images were processed with SPM 2.0.

RESULTS

The learning and memory skills were weakened in AD rats. Besides, the glucose metabolic activity of AD rats decreased in hippolampus, hypothalamus, insular cortex, piriform cortex, striatum, cingulate gyrus, stria terminalis, and parietal lobe and increased in olfactory bulb, cerebellum, midbrain, pontine, and retrosplenial cortex compared with the control group. Dorsal thalamus had shown both enhanced and reduced glucose metabolic activity.

CONCLUSION

Our data indicate that the changed glucose metabolism in cerebral regions in (18)F-FDG-PET imaging could be an important predictor for early AD.

The Current Status of SPECT or SPECT/CT in South Korea

The first step to nuclear medicine in Korea started with introduction of the gamma camera in 1969. Although planar images with the gamma camera give important functional information, they have the limitations that result from 2-dimensional images. Single-photon emission computed tomography (SPECT) due to its 3-dimensional image acquisition is superior to earlier planar gamma imaging in image resolution and diagnostic accuracy. As demand for a hybrid functional and anatomical imaging device has increased, integrated SPECT/CT systems have been used. In Korea, SPECT/CT was for the first time installed in 2003. SPECT/CT can eliminate many possible pitfalls on SPECT-alone images, making better attenuation correction and thereby improving image quality. Therefore, SPECT/CT is clinically preferred in many hospitals in various aspects. More recently, additional SPECT/CT images taken from the region with equivocal uptake on planar images have been helpful in making precise interpretation as part of their clinical workup in postoperative thyroid cancer patients. SPECT and SPECT/CT have various advantages, but its clinical application has gradually decreased in recent few years. While some researchers investigated the myocardial blood flow with cardiac PET using F-18 FDG or N-13 ammonia, myocardial perfusion SPECT is, at present, the radionuclide imaging study of choice for the risk stratification and guiding therapy in the coronary artery disease patients in Korea. New diagnostic radiopharmaceuticals for AD have received increasing attention; nevertheless, brain SPECT will remain the most reliable modality evaluating cerebral perfusion.

Lewy Body Dementias: Dementia With Lewy Bodies and Parkinson Disease Dementia

PURPOSE OF REVIEW

This article provides an overview of the clinical features, neuropathologic findings, diagnostic criteria, and management of dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD), together known as the Lewy body dementias.

RECENT FINDINGS

DLB and PDD are common, clinically similar syndromes that share characteristic neuropathologic changes, including deposition of α-synuclein in Lewy bodies and neurites and loss of tegmental dopamine cell populations and basal forebrain cholinergic populations, often with a variable degree of coexisting Alzheimer pathology. The clinical constellations of DLB and PDD include progressive cognitive impairment associated with parkinsonism, visual hallucinations, and fluctuations of attention and wakefulness. Current clinical diagnostic criteria emphasize these features and also weigh evidence for dopamine cell loss measured with single-photon emission computed tomography (SPECT) imaging and for rapid eye movement (REM) sleep behavior disorder, a risk factor for the synucleinopathies. The timing of dementia relative to parkinsonism is the major clinical distinction between DLB and PDD, with dementia arising in the setting of well-established idiopathic Parkinson disease (after at least 1 year of motor symptoms) denoting PDD, while earlier cognitive impairment relative to parkinsonism denotes DLB. The distinction between these syndromes continues to be an active research question. Treatment for these illnesses remains symptomatic and relies on both pharmacologic and nonpharmacologic strategies.

SUMMARY

DLB and PDD are important and common dementia syndromes that overlap in their clinical features, neuropathology, and management. They are believed to exist on a spectrum of Lewy body disease, and some controversy persists in their differentiation. Given the need to optimize cognition, extrapyramidal function, and psychiatric health, management can be complex and should be systematic.

Early differential diagnosis between Alzheimer's disease and dementia with Lewy bodies: Comparison between (18)F-FDG PET and (123)I-IMP SPECT

Both (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and (123)I-iodoamphetamine (IMP) single-photon emission computed tomography (SPECT) have been used for the differential diagnosis of Alzheimer's disease (AD) and dementia with Lewy bodies (DLB). Less information is available, however, regarding the differential diagnosis of mild cognitive impairment (MCI) due to AD and MCI due to DLB. We examined nine AD patients (AD group), nine DLB patients (DLB group), eight MCI due to AD patients (MCI-AD group), and nine MCI due to DLB patients (MCI-DLB group) with FDG PET and IMP SPECT using a well-characterized normal database and a stereotactic extraction estimation method. In the AD and DLB groups, receiver operating characteristic (ROC) analysis in the occipital regions showed significant accuracy of both FDG PET and IMP SPECT for the differential diagnosis. In the MCI-AD and MCI-DLB groups, ROC analysis showed significant accuracy of only FDG PET for the differential diagnosis. Both FDG PET and IMP SPECT would be useful for the differential diagnosis between AD and DLB. For the differential diagnosis of MCI-AD versus MCI-DLB, FDG PET would be more useful than IMP SPECT.

Brain imaging in dementia

The introduction of MRI and positron emission tomography (PET) brain imaging has contributed significantly to the understanding of different dementia syndromes. Over the past 20 years these imaging techniques have been increasingly used for clinical characterisation and differential diagnosis, and to provide insight into the effects on functional capacity of the brain, patterns of spatial distribution of different dementia syndromes and their natural history and evolution over time. Brain imaging is also increasingly used in clinical trials, as part of inclusion criteria and/or as a surrogate outcome measure. Here we review all the relatively specific findings that can be identified with different MRI and PET techniques in each of the most frequent dementing disorders.

Early Dementia Screening

As the population of the world increases, there will be larger numbers of people with dementia and an emerging need for prompt diagnosis and treatment. Early dementia screening is the process by which a patient who might be in the prodromal phases of a dementing illness is determined as having, or not having, the hallmarks of a neurodegenerative condition. The concepts of mild cognitive impairment, or mild neurocognitive disorder, are useful in analyzing the patient in the prodromal phase of a dementing disease; however, the transformation to dementia may be as low as 10% per annum. The search for early dementia requires a comprehensive clinical evaluation, cognitive assessment, determination of functional status, corroborative history and imaging (including MRI, FDG-PET and maybe amyloid PET), cerebrospinal fluid (CSF) examination assaying Aβ_1–42, T-τ and P-τ might also be helpful. Primary care physicians are fundamental in the screening process and are vital in initiating specialist investigation and treatment. Early dementia screening is especially important in an age where there is a search for disease modifying therapies, where there is mounting evidence that treatment, if given early, might influence the natural history—hence the need for cost-effective screening measures for early dementia.

Is there a preference for PET or SPECT brain imaging in diagnosing dementia? The views of people with dementia, carers, and healthy controls

BACKGROUND

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) brain imaging are widely used as diagnostic tools for suspected dementia but no studies have directly compared participant views of the two procedures. We used a range of methods to explore preferences for PET and SPECT.

METHODS

Patients and controls (and accompanying carers) completed questionnaires immediately after undergoing PET and SPECT brain scans. Pulse rate data were collected during each scan. Scan attributes were prioritized using a card sorting exercise; carers and controls additionally answered willingness to pay (WTP) questions.

RESULTS

Few differences were found either between the scans or groups of participants, although carers marginally preferred SPECT. Diagnostic accuracy was prioritized over other scan characteristics. Mean heart rate during both scans was lower than baseline heart rate measured at home (p < 0.001).

CONCLUSION

Most participants viewed PET and SPECT scans as roughly equivalent and did not have a preference for either scan. Carer preference for SPECT is likely to reflect their desire to be with the patient (routine practice for SPECT but not for PET), suggesting that they should be able to accompany vulnerable patients throughout imaging procedures wherever possible. Pulse rate data indicated that brain imaging was no more stressful than a home visit (HV) from a researcher. The data do not support the anecdotal view that PET is a more burdensome procedure and the use of PET or SPECT scans in dementia should be based on diagnostic accuracy of the technique.

Comparisons of clinical symptoms in biomarker-confirmed Alzheimer's disease, dementia with Lewy bodies, and frontotemporal dementia patients in a local memory clinic

BACKGROUND

There has been no previous Chinese study that differentiated the clinical symptoms among biomarker-confirmed Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and frontotemporal dementia (FTD). The objective of this study was to compare the cognitive, behavioural, and neuropsychiatric symptoms in biomarker-confirmed AD, DLB, and FTD patients.

METHODS

We recruited 30 patients (14 AD, 7 DLB, 9 FTD) who presented to the memory clinic at Queen Mary Hospital from 1 January 2007 to 31 December 2013. AD was diagnosed according to the National Institution of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria with cerebrospinal fluid biomarkers (tau, phosphorylated tau, and amyloid β-42) fulfilling locally determined cut-off values for AD. DLB was diagnosed based on the McKeith diagnostic criteria. The behavioural variant of FTD was diagnosed based on the revised diagnostic criteria proposed by the International bvFTD Criteria Consortium, and language variant FTD was diagnosed based on the latest published criteria. In addition, patients with DLB and FTD had typical imaging features on single-photon emission computed tomography or (18) fludeoxyglucose-positron emission tomography, either with or without Pittsburgh Compound B imaging, which supported their diagnoses. Data on patient characteristics including demographics, presenting clinical features, Mini-Mental State Examination, clinical dementia ratings, and neuropsychiatry inventory scores were collected.

RESULTS

There were no differences in age, education level, dementia severity, and duration of symptoms before presentation among the three subgroups of patients. All patients had amnesia symptoms, which were not statistically significant. Apraxia was most common in AD. While 83% of the patients were affected by behavioural and neuropsychiatric symptoms of dementia, behavioural disinhibition and decline in executive function were most common in FTD patients. Recurrent hallucinations, fluctuation of consciousness, parkinsonism, and rapid eye movement sleep behaviour disorder were most common in DLB.

CONCLUSION

Memory impairment and apathy are not useful discriminative symptoms in diagnosing AD, DLB, and FTD. Apraxia favours AD. Hallucinations, particularly well-formed visual hallucinations, favour DLB. Overall, behavioural and neuropsychiatric symptoms of dementia symptoms are common among the three groups of dementia patients.

Brain PET in the diagnosis of Alzheimer's disease

OBJECTIVES

The aim of this article was to review the current role of brain PET in the diagnosis of Alzheimer dementia. The characteristic patterns of glucose metabolism on brain FDG-PET can help in differentiating Alzheimer's disease from other causes of dementia such as frontotemporal dementia and dementia of Lewy body. Amyloid brain PET may exclude significant amyloid deposition and thus Alzheimer's disease in appropriate clinical setting.

CONCLUSIONS

FDG-PET and amyloid PET imaging are valuable in the assessment of patients with Alzheimer's disease.

CT-based attenuation and scatter correction compared with uniform attenuation correction in brain perfusion SPECT imaging for dementia

This study investigated if the appearance and diagnostic accuracy of HMPAO brain perfusion SPECT images could be improved by using CT-based attenuation and scatter correction compared with the uniform attenuation correction method. A cohort of subjects who were clinically categorized as Alzheimer's Disease (n = 38), Dementia with Lewy Bodies (n = 29) or healthy normal controls (n = 30), underwent SPECT imaging with Tc-99m HMPAO and a separate CT scan. The SPECT images were processed using: (a) correction map derived from the subject's CT scan or (b) the Chang uniform approximation for correction or (c) no attenuation correction. Images were visually inspected. The ratios between key regions of interest known to be affected or spared in each condition were calculated for each correction method, and the differences between these ratios were evaluated. The images produced using the different corrections were noted to be visually different. However, ROI analysis found similar statistically significant differences between control and dementia groups and between AD and DLB groups regardless of the correction map used.We did not identify an improvement in diagnostic accuracy in images which were corrected using CT-based attenuation and scatter correction, compared with those corrected using a uniform correction map.

Molecular imaging biomarkers for dementia with Lewy bodies: an update

BACKGROUND

Dementia with Lewy body (DLB) is considered to be the second most common form of neurodegenerative disorders after Alzheimer's disease (AD), affecting as many as 100,000 people in the UK and up to 1.3 million in the USA. However, nearly half of patients with DLB remain undiagnosed thus depriving many of them from an early and adequate treatment of their distressing symptoms. Accurate and early diagnosis of DLB is important for both patients and their caregivers, since the neuropsychiatric symptoms require specific management.

METHODS

In the current study, we review the most recent developments in the field of molecular nuclear imaging to diagnose DLB.

RESULTS

The review addresses, the neurotransmitter based (dopaminergic, cholinergic, and glutamatergic) nuclear imaging techniques, role of the autonomic dysfunction and its visualization in DLB with myocardial sympathetic imaging and vesicular catecholamine uptake, as well as the use of amyloid polypeptides and glial markers as molecular imaging probes in the clinical diagnosis of DLB.

CONCLUSIONS

Most of the above nuclear imaging methods are restricted to highly specialized clinical centers, and thus not applicable to a large number of patients requiring dementia (e.g. DLB) diagnosis in routine clinical setting. Validating them against more readily accessible peripheral biomarkers, e.g. CSF and blood biomarkers linked to the DLB process, may facilitate their use in wider clinical settings.