A clinical role for 99mTc-HMPAO SPECT in the investigation 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.

The scope of using pragmatic language tests for early detection of dementia: A systematic review of investigations using figurative language

INTRODUCTION

Dementia cases are expected to rise to 81.1 million in 2040. Efforts are underway to develop diagnostic methods to facilitate early detection of the disease. Herein we review research findings focusing on pragmatic dysfunction in patients with dementia and evaluate the usefulness of assessing dementia and its progress with a battery of tests assessing figurative language skills.

METHODS

A total of 74,778 article titles were identified from EMBASE, PubMed, and Google Scholar databases. After systematic screening, 51 journal articles were selected for the final review.

RESULT

The review suggests that impaired figurative language might be a marker for early cognitive decline. Different forms of figurative language may be impaired at different stages of the disease and in different types of dementia involving different neuropathologies.

CONCLUSION

The use of pragmatic tests in combination with the existing diagnostic protocols might increase the probability of early diagnosis. HIGHLIGHTS Pragmatic impairment could be a marker of early cognitive impairment. Figurative language-an important pragmatic aspect-is disrupted in mild cognitive impairment (MCI) and early Alzheimer's disease (AD). Figurative language impairment might precede literal language impairment. Pragmatic tests could be more sensitive than standard neuropsychological tests. Inclusion of pragmatic tests in diagnostic guidelines might bolster early detection.

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.

The Neuropsychological Correlates of Brain Perfusion and Gray Matter Volume in Alzheimer's Disease

BACKGROUND

Neuropsychological tests, structural neuroimaging, and functional neuroimaging are employed as diagnostic and monitoring biomarkers of patients with Alzheimer's disease (AD)Objective:We aimed to elucidate the similarities and differences in neuropsychological tests and neuroimaging with the use of the Mini-Mental State Examination (MMSE), Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog), structural magnetic resonance image (MRI), and perfusion single photon emission computed tomography (SPECT), and parametric image analyses to understand its role in AD.

METHODS

Clinically-diagnosed AD patients (n = 155) were scanned with three-dimensional T1-weighted MRI and N-isopropyl-p-[123I] iodoamphetamine SPECT. Statistical parametric mapping 12 was used for preprocessing images, statistical analyses, and voxel-based morphometry for gray matter volume analyses. Group comparison (AD versus healthy controls), multiple regression analyses with MMSE, ADAS-cog total score, and ADAS-cog subscores as variables, were performed.

RESULTS

The AD group showed bilateral hippocampal volume reduction and hypoperfusion in the bilateral temporo-parietal lobe and posterior midline structures. Worse MMSE and ADAS-cog total score were associated with bilateral temporo-parietal volume loss and hypoperfusion. MMSE, but not ADAS-cog, was associated with the posterior midline structures. The ADAS-cog subscores were associated with the temporal volume, while perfusion analyses were linked to the left temporo-parietal region with the language function and right analogous region with the constructional praxis subscore.

CONCLUSION

MMSE and ADAS-cog are associated with temporo-parietal regions, both in volume and perfusion. The MMSE score is associated with posterior midline structures and linked to an abnormal diagnostic AD pattern. Perfusion image analyses better represents the cognitive function in AD patients.

ACR Appropriateness Criteria® Dementia

Degenerative disease of the central nervous system is a growing public health concern. The primary role of neuroimaging in the workup of patients with probable or possible Alzheimer disease has typically been to exclude other significant intracranial abnormalities. In general, the imaging findings in structural studies, such as MRI, are nonspecific and have limited potential in differentiating different types of dementia. Advanced imaging methods are not routinely used in community or general practices for the diagnosis or differentiation of forms of dementia. Nonetheless, in patients who have been evaluated by a dementia expert, FDG-PET helps to distinguish Alzheimer disease from frontotemporal dementia. In patients with suspected dementia with Lewy bodies, functional imaging of the dopamine transporter (ioflupane) using SPECT may be helpful. In patients with suspected normal-pressure hydrocephalus, DTPA cisternography and HMPAO SPECT/CT brain may provide assessment. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Combining SPECT and Quantitative EEG Analysis for the Automated Differential Diagnosis of Disorders with Amnestic Symptoms

Single photon emission computed tomography (SPECT) and Electroencephalography (EEG) have become established tools in routine diagnostics of dementia. We aimed to increase the diagnostic power by combining quantitative markers from SPECT and EEG for differential diagnosis of disorders with amnestic symptoms. We hypothesize that the combination of SPECT with measures of interaction (connectivity) in the EEG yields higher diagnostic accuracy than the single modalities. We examined 39 patients with Alzheimer's dementia (AD), 69 patients with depressive cognitive impairment (DCI), 71 patients with amnestic mild cognitive impairment (aMCI), and 41 patients with amnestic subjective cognitive complaints (aSCC). We calculated 14 measures of interaction from a standard clinical EEG-recording and derived graph-theoretic network measures. From regional brain perfusion measured by 99mTc-hexamethyl-propylene-aminoxime (HMPAO)-SPECT in 46 regions, we calculated relative cerebral perfusion in these patients. Patient groups were classified pairwise with a linear support vector machine. Classification was conducted separately for each biomarker, and then again for each EEG- biomarker combined with SPECT. Combination of SPECT with EEG-biomarkers outperformed single use of SPECT or EEG when classifying aSCC vs. AD (90%), aMCI vs. AD (70%), and AD vs. DCI (100%), while a selection of EEG measures performed best when classifying aSCC vs. aMCI (82%) and aMCI vs. DCI (90%). Only the contrast between aSCC and DCI did not result in above-chance classification accuracy (60%). In general, accuracies were higher when measures of interaction (i.e., connectivity measures) were applied directly than when graph-theoretical measures were derived. We suggest that quantitative analysis of EEG and machine-learning techniques can support differentiating AD, aMCI, aSCC, and DCC, especially when being combined with imaging methods such as SPECT. Quantitative analysis of EEG connectivity could become an integral part for early differential diagnosis of cognitive impairment.

MR Elastography Demonstrates Unique Regional Brain Stiffness Patterns in Dementias

OBJECTIVE

The purpose of this study was to investigate age-corrected brain MR elastography (MRE) findings in four dementia cohorts (Alzheimer disease, dementia with Lewy bodies, frontotemporal dementia, and normal pressure hydrocephalus) and determine the potential use as a differentiating biomarker in dementia subtypes.

SUBJECTS AND METHODS

Institutional review board approval and written informed consent were obtained to perform MRE on 84 subjects: 20 patients with normal pressure hydrocephalus, eight with Alzheimer disease, five with dementia with Lewy bodies, five with frontotemporal dementia, and 46 cognitively normal control subjects. Shear waves of 60-Hz vibration frequency were transmitted into the brain using a pillowlike passive driver, and brain stiffness was determined in eight different regions (cerebrum, frontal, occipital, parietal, temporal, deep gray matter-white matter, sensorimotor cortex, and cerebellum). All stiffness values were age-corrected and compared with control subjects. The Wilcoxon rank sum test and linear regression were used for statistical analysis.

RESULTS

Regional stiffness patterns unique to each dementing disorder were observed. Patients with Alzheimer disease and frontotemporal dementia showed decreased cerebral stiffness (p = 0.001 and p = 0.002, respectively) with regional softening of the frontal and temporal lobes. Patients with Alzheimer disease additionally showed parietal lobe and sensorimotor region softening (p = 0.039 and p = 0.018, respectively). Patients with normal pressure hydrocephalus showed stiffening of the parietal, occipital, and sensorimotor regions (p = 0.007, p < 0.001, and p < 0.0001, respectively). Patients with dementia with Lewy bodies did not show significant stiffness changes in any of the regions.

CONCLUSION

Quantitative MRE of changes in brain viscoelastic structure shows unique regional brain stiffness patterns between common dementia subtypes.

Regional cerebral blood flow single photon emission computed tomography for detection of Frontotemporal dementia in people with suspected dementia

BACKGROUND

In the UK, dementia affects 5% of the population aged over 65 years and 25% of those over 85 years. Frontotemporal dementia (FTD) represents one subtype and is thought to account for up to 16% of all degenerative dementias. Although the core of the diagnostic process in dementia rests firmly on clinical and cognitive assessments, a wide range of investigations are available to aid diagnosis.Regional cerebral blood flow (rCBF) single-photon emission computed tomography (SPECT) is an established clinical tool that uses an intravenously injected radiolabelled tracer to map blood flow in the brain. In FTD the characteristic pattern seen is hypoperfusion of the frontal and anterior temporal lobes. This pattern of blood flow is different to patterns seen in other subtypes of dementia and so can be used to differentiate FTD.It has been proposed that a diagnosis of FTD, (particularly early stage), should be made not only on the basis of clinical criteria but using a combination of other diagnostic findings, including rCBF SPECT. However, more extensive testing comes at a financial cost, and with a potential risk to patient safety and comfort.

OBJECTIVES

To determine the diagnostic accuracy of rCBF SPECT for diagnosing FTD in populations with suspected dementia in secondary/tertiary healthcare settings and in the differential diagnosis of FTD from other dementia subtypes.

SEARCH METHODS

Our search strategy used two concepts: (a) the index test and (b) the condition of interest. We searched citation databases, including MEDLINE (Ovid SP), EMBASE (Ovid SP), BIOSIS (Ovid SP), Web of Science Core Collection (ISI Web of Science), PsycINFO (Ovid SP), CINAHL (EBSCOhost) and LILACS (Bireme), using structured search strategies appropriate for each database. In addition we searched specialised sources of diagnostic test accuracy studies and reviews including: MEDION (Universities of Maastricht and Leuven), DARE (Database of Abstracts of Reviews of Effects) and HTA (Health Technology Assessment) database.We requested a search of the Cochrane Register of Diagnostic Test Accuracy Studies and used the related articles feature in PubMed to search for additional studies. We tracked key studies in citation databases such as Science Citation Index and Scopus to ascertain any further relevant studies. We identified 'grey' literature, mainly in the form of conference abstracts, through the Web of Science Core Collection, including Conference Proceedings Citation Index and Embase. The most recent search for this review was run on the 1 June 2013.Following title and abstract screening of the search results, full-text papers were obtained for each potentially eligible study. These papers were then independently evaluated for inclusion or exclusion.

SELECTION CRITERIA

We included both case-control and cohort (delayed verification of diagnosis) studies. Where studies used a case-control design we included all participants who had a clinical diagnosis of FTD or other dementia subtype using standard clinical diagnostic criteria. For cohort studies, we included studies where all participants with suspected dementia were administered rCBF SPECT at baseline. We excluded studies of participants from selected populations (e.g. post-stroke) and studies of participants with a secondary cause of cognitive impairment.

DATA COLLECTION AND ANALYSIS

Two review authors extracted information on study characteristics and data for the assessment of methodological quality and the investigation of heterogeneity. We assessed the methodological quality of each study using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) tool. We produced a narrative summary describing numbers of studies that were found to have high/low/unclear risk of bias as well as concerns regarding applicability. To produce 2 x 2 tables, we dichotomised the rCBF SPECT results (scan positive or negative for FTD) and cross-tabulated them against the results for the reference standard. These tables were then used to calculate the sensitivity and specificity of the index test. Meta-analysis was not performed due to the considerable between-study variation in clinical and methodological characteristics.

MAIN RESULTS

Eleven studies (1117 participants) met our inclusion criteria. These consisted of six case-control studies, two retrospective cohort studies and three prospective cohort studies. Three studies used single-headed camera SPECT while the remaining eight used multiple-headed camera SPECT. Study design and methods varied widely. Overall, participant selection was not well described and the studies were judged as having either high or unclear risk of bias. Often the threshold used to define a positive SPECT result was not predefined and the results were reported with knowledge of the reference standard. Concerns regarding applicability of the studies to the review question were generally low across all three domains (participant selection, index test and reference standard).Sensitivities and specificities for differentiating FTD from non-FTD ranged from 0.73 to 1.00 and from 0.80 to 1.00, respectively, for the three multiple-headed camera studies. Sensitivities were lower for the two single-headed camera studies; one reported a sensitivity and specificity of 0.40 (95% confidence interval (CI) 0.05 to 0.85) and 0.95 (95% CI 0.90 to 0.98), respectively, and the other a sensitivity and specificity of 0.36 (95% CI 0.24 to 0.50) and 0.92 (95% CI 0.88 to 0.95), respectively.Eight of the 11 studies which used SPECT to differentiate FTD from Alzheimer's disease used multiple-headed camera SPECT. Of these studies, five used a case-control design and reported sensitivities of between 0.52 and 1.00, and specificities of between 0.41 and 0.86. The remaining three studies used a cohort design and reported sensitivities of between 0.73 and 1.00, and specificities of between 0.94 and 1.00. The three studies that used single-headed camera SPECT reported sensitivities of between 0.40 and 0.80, and specificities of between 0.61 and 0.97.

AUTHORS' CONCLUSIONS

At present, we would not recommend the routine use of rCBF SPECT in clinical practice because there is insufficient evidence from the available literature to support this.Further research into the use of rCBF SPECT for differentiating FTD from other dementias is required. In particular, protocols should be standardised, study populations should be well described, the threshold for 'abnormal' scans predefined and clear details given on how scans are analysed. More prospective cohort studies that verify the presence or absence of FTD during a period of follow up should be undertaken.

Neuroimaging referral for dementia diagnosis: The specialist's perspective in Ireland

BACKGROUND

Neuroimaging is an increasingly important tool in the diagnostic workup of dementia. Neurologists, geriatricians, and old-age psychiatrists are involved in key tasks in the diagnostic process, frequently referring patients with suspected dementia for neuroimaging.

METHODS

The research design was a postal survey of all geriatricians, old-age psychiatrists, and neurologists in the Republic of Ireland (N = 176) as identified by the Irish Medical Directory 2011-2012 and supplementary listings.

RESULTS

Almost 65% of specialists did not have access to 2-[18F]fluoro-2-deoxy-D-glucose positron emission (FDG-PET) or FDG-PET/computed tomography (CT), and 80.3% did not have access to perfusion hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) or dopaminergic iodine-123-radiolabeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane SPECT. Most specialists (88.7%) referred patients with mild cognitive impairment or suspected dementia for magnetic resonance imaging (MRI), 81.7% referred for CT, and 26.8% for FDG-PET or FDG-PET/CT. Only 44.6% of respondents were aware of dementia-specific protocols for referrals for neuroimaging.

CONCLUSION

Specialist access to imaging modalities other than CT and MRI is restricted. Improved access may affect patient treatment and care.

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

OBJECTIVE

Perfusion single photon emission computed tomography (SPECT) and 18F fluorodeoxyglucose positron emission tomography (FDG-PET) both have clinical utility for the differential diagnosis of dementia. Although PET is often viewed by some as more accurate and therefore preferential, the extent to which published evidence supports this is not clear. The aim of this review was to address the question by reviewing studies of SPECT and PET imaging in dementia diagnosis, with a particular focus on all published head-to-head studies.

DESIGN

A MEDLINE search was carried out using the following keywords: "PET" and "SPECT" and "dementia" or "Mild Cognitive Impairment," together with "alzheimers" or "DLB" or "lewy body" or "frontotemporal" or "FTD" or "Picks." Articles were included up to February 2013, limited to human studies and in English language.

RESULTS

Published studies of SPECT accuracy show that it is a useful tool for differential diagnosis, with sensitivities of 65-85% for diagnosing Alzheimer's disease (AD) and specificities (for other neurodegenerative dementias) of 72-87%. PET studies generally report higher accuracy, with sensitivities of 75-99% for AD and specificities of 71-93%. However, there have been few direct head-to-head comparisons, with some indicating SPECT and PET to be equally useful in dementia diagnosis and others favouring PET. Many of these studies are limited with respect to numbers and methodically with poorly matched control groups.

CONCLUSIONS

Overall, although studies suggest superiority of PET over SPECT, the evidence base for this is actually quite limited. We suggest that further direct comparative studies, including health economic and patient preference evaluations, are needed to help direct future service provision.

Is the cerebellum the optimal reference region for intensity normalization of perfusion MR studies in early Alzheimer's disease?

The cerebellum is the region most commonly used as a reference when normalizing the intensity of perfusion images acquired using magnetic resonance imaging (MRI) in Alzheimer's disease (AD) studies. In addition, the cerebellum provides unbiased estimations with nuclear medicine techniques. However, no reports confirm the cerebellum as an optimal reference region in MRI studies or evaluate the consequences of using different normalization regions. In this study, we address the effect of using the cerebellum, whole-brain white matter, and whole-brain cortical gray matter in the normalization of cerebral blood flow (CBF) parametric maps by comparing patients with stable mild cognitive impairment (MCI), patients with AD and healthy controls. According to our results, normalization by whole-brain cortical gray matter enables more sensitive detection of perfusion abnormalities in AD patients and reveals a larger number of affected regions than data normalized by the cerebellum or whole-brain white matter. Therefore, the cerebellum is not the most valid reference region in MRI studies for early stages of AD. After normalization by whole-brain cortical gray matter, we found a significant decrease in CBF in both parietal lobes and an increase in CBF in the right medial temporal lobe. We found no differences in perfusion between patients with stable MCI and healthy controls either before or after normalization.

The diagnosis and evaluation of dementia and mild cognitive impairment with emphasis on SPECT perfusion neuroimaging

As the world population ages, the incidence of dementing illnesses will dramatically increase. The number of people afflicted with dementia is expected to quadruple in the next 50 years. Since the neuropathology of the dementias precedes clinical symptoms often by several years, earlier detection and intervention could be key steps to mitigating the progression and burden of these diseases. This review will explore methods of evaluating, differentiating, and diagnosing the multiple forms of dementia. Particular emphasis will be placed on the diagnosis of mild cognitive impairment-the precursor to dementia. Anatomical imaging; cerebrospinal fluid markers; functional neuroimaging, such as positron emission tomography and single photon emission tomography; and molecular imaging, such as amyloid marker imaging, will be assessed in terms of sensitivity and specificity. Cost will also be a consideration, as the growing population afflicted with dementia represents an increasingly large financial encumbrance to the healthcare systems of every nation. In the face of expensive new markers and limited availability of cyclotrons, single photon emission computer tomography (SPECT) provides relatively high sensitivity and specificity at a comparatively low overall cost.

Vascular dementia: Diagnostic criteria and supplementary exams. Recommendations of the Scientific Department of Cognitive Neurology and Aging of the Brazilian Academy of Neurology. Part I

Vascular dementia (VaD) is the most prevalent form of secondary dementia and the second most common of all dementias. The present paper aims to define guidelines on the basic principles for treating patients with suspected VaD (and vascular cognitive impairment - no dementia) using an evidence-based, systematized approach. The knowledge used to define these guidelines was retrieved from searches of several databases (Medline, Scielo, Lilacs) containing scientific articles, systematic reviews, meta-analyses, largely published within the last 15 years or earlier when pertinent. Information retrieved and selected for relevance was used to analyze diagnostic criteria and to propose a diagnostic system encompassing diagnostic criteria, anamnesis, as well as supplementary and clinical exams (neuroimaging and laboratory). Wherever possible, instruments were selected that had versions previously adapted and validated for use in Brazil that take into account both schooling and age. This task led to proposed protocols for supplementary exams based on degree of priority, for application in clinical practice and research settings.

Perfusion SPECT and FDG-PET

Both perfusion SPECT and FDG-PET provide images that closely reflect neuronal activity. There is a characteristic regional impairment in Alzheimer’s disease (AD) that involves mainly the temporo-parietal association cortices, mesial temporal structures and to a more variable degree also the frontal association cortex. This pattern of functional impairment can provide a biomarker for diagnosis of AD and other neurodegenerative dementias at the clinical stage of mild cognitive impairment, and for monitoring of progression. FDG-PET is quantitatively more accurate and thus better suited to multicenter studies than perfusion SPECT. Regional metabolic and blood flow changes are closely related to clinical symptoms, and most areas involved in these changes will also develop significant cortical atrophy. FDG-PET is complementary to amyloid PET, which targets a molecular marker that does not have a close relation to current symptoms. Current restrictions in the availability and cost of FDG-PET are being reduced, as oncological FDG-PET is being adopted as a standard clinical service in most countries. Limitations in the availability of trained staff should be overcome by training programs set up by professional organizations. Against the background of the development of new criteria for diagnosing AD before the onset of dementia, FDG-PET is expected to play an increasing role in diagnosing patients at an early stage of AD and in clinical trials of drugs aimed at preventing or delaying the onset of dementia.

Could clinical profile influence CSF biomarkers in early-onset Alzheimer disease?

In common forms of Alzheimer disease (AD), anterograde memory impairment is the first deficit to occur. However, the disease, especially in its presenile forms, may also manifest itself through initial deficits that are predominantly of a nonmemory type. These distinct clinical profiles, which reflect the distinct topography of the underlying pathologic processes, may also differ in terms of their cerebrospinal fluid (CSF) markers. The aim of this study was to assess the levels of total tau, phosphorylated tau, and amyloid-beta 42 peptide in the CSF of "atypical" (nonmemory) early-onset AD patients. CSF biomarkers were evaluated in 22 atypical patients, and compared with those from a group of 13 "typical" patients, with a memory onset form of the disease. Our results show that independently of age, disease duration, education level, and clinical severity indices, patients with an atypical onset have significantly higher levels of total tau in the CSF (P=0.023). These findings indicate that an assessment of CSF biomarkers may be of particular use in the clinical diagnosis of "atypical-onset" forms of early-onset AD in which the initial symptoms involve language and visuospatial abilities rather than memory. In addition, they highlight the heterogeneity of pathologic processes in AD, suggesting more intense degeneration in the forms of the disease that primarily involve neocortical structures.

Working memory, attention, and executive function in Alzheimer's disease and frontotemporal dementia

Working memory deficits are a recognised feature of Alzheimer's disease (AD). They are commonly ascribed to central executive impairment and assumed to relate to frontal lobe dysfunction. Performance failures on standard tests of attention and executive function reinforce this interpretation. Nevertheless, early-onset AD patients do not show the frank behavioural changes indicative of frontal lobe dysfunction, and the characteristic functional neuroimaging changes are in posterior hemispheres rather than frontal lobes. We explored this anomaly through a comparison of working memory, attention and executive test performance in patients with AD (a 'typical' early-onset group with deficits in memory, language and perceptuospatial function and an 'amnesic' group) and frontotemporal dementia (FTD). Typical-AD and FTD patients both showed impaired performance, whereas amnesic-AD patients performed well. Despite similar quantitative performance measures, typical-AD and FTD patients showed qualitatively distinct performance profiles. Impairments in FTD patients were interpreted in 'frontal' executive terms as deficits in attention, set shifting and response inhibition. AD patients' performance appeared to be influenced by information load and was interpreted in terms of working memory capacity. In keeping with these different interpretations, neuroimaging showed characteristic frontal lobe abnormalities in FTD and temporoparietal change in typical-AD. The findings highlight the importance of the posterior hemispheres in working memory and point to a need for caution in the automatic attribution of working memory, attention and executive test failures to frontal lobe failure. They underline also the phenotypic variation within AD.

An analysis of communication in conversation in patients with dementia

Patients with degenerative dementia often show language disorders, but little is known about their verbal (VC) and non-verbal communication (NVC). Our aim was to analyse VC and NVC in patients with standard criteria of mild-moderately severe dementia (MMSE ≥14/30) resulting from Alzheimer's disease (AD; 29 cases), behavioural variant of frontotemporal dementia (FTD; 16), or dementia with Lewy bodies (DLB; 13). We used the Lille Communication Test, which addresses three domains: participation in communication (PC: greeting, attention, participation), VC (verbal comprehension, speech outflow, intelligibility, word production, syntax, verbal pragmatics and verbal feedback), and NVC (understanding gestures, affective expressivity, producing gestures, pragmatics and feedback). Patients were compared with 47 matching control subjects. AD patients were partially impaired (p≤0.01) in PC (greeting), and more definitely in VC, especially by verbal comprehension and word finding difficulties and to a much lesser degree in verbal pragmatics (responding to open questions, presenting new information), while NVC was mostly preserved. FTD patients were severely impaired in PC. VC difficulties were related to lexical-semantic, syntactic and more specifically pragmatic problems. NVC was impaired by difficulties in affective expressivity, pragmatics and feedback management. DLB patients showed modest difficulties with VC. PC, VC and NVC strongly correlated with performance in the dementia rating scale. In conclusion, the profile of communication difficulties was quite different between groups. FTD patients showed most severe difficulties in PC and verbal and non-verbal pragmatics, in relation to their frontal lesions. AD patients had prominent impairment of lexical-semantic operations.

Functional correlates of instrumental activities of daily living in mild Alzheimer's disease

Instrumental activities of daily living (IADL) includes the integration of task-initiation, -planning, and -performance. Little is known on the cerebral perfusion correlates of these subcomponents of IADL in Alzheimer's disease (AD). In 121 AD patients, cerebral perfusion, using single-photon emission computed tomography, in 13 bilateral regions of interest (ROI) and the perfusion correlates of IADL subcomponents, rated on the Disability Assessment in Dementia scale, were explored. Significant correlations were observed between IADL initiation and multiple bilateral prefrontal-striatal-anterior cingulate ROI (p < 0.01), IADL planning and right occipital ROI (p < 0.05), and IADL performance and right parietal ROI (p < 0.05). Multiple regression, accounting for age, cognitive impairment, and depression severity, revealed significant relationship between right basal ganglia perfusion and IADL-initiation (R = 0.6, R(2) = 0.39, F(4,117) = 17.8, SE = 1.56; p < 0.001) and right occipital perfusion and IADL-planning (R = 0.6, R(2) = 0.34, F(4,117) = 19.5, SE = 1.47; p < 0.001). In AD, perfusion correlates of these subcomponents may be linked to the heterogenous cognitive processes involved in IADL.

Imaging improves diagnosis of dementia with lewy bodies

Dementia with Lewy bodies (DLB) is the second most common cause of degenerative dementia after Alzheimer's disease (AD), and is clinically characterized by the progressive cognitive decline with fluctuations in cognition and alertness, recurrent visual hallucinations and Parkinsonism. Once these characteristic symptoms of DLB emerge, discriminating it from AD is relatively easy. However, in the early disease stages, the clinical symptoms of various types of dementias largely overlap and it is difficult to distinguish DLB from other neurodegenerative dementias based on clinical manifestations alone. To increase the accuracy of antemortem diagnosis of DLB, the latest diagnostic criteria incorporate findings from 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy, or from neuroimaging such as computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). In the present guidelines, decreased dopamine transporter uptake revealed by SPECT or PET receives the greatest importance among various neuroimaging findings and is listed as one of the suggestive features. Supportive features that commonly present but are not proven to have diagnostic specificity include relatively-preserved medial-temporal-lobe structures, occipital hypoperfusion, and abnormal MIBG myocardial scintigraphy. In this paper, we review the major findings on various neuroimaging modalities and discuss the clinical usefulness of them for the diagnosis of DLB. Although there is not enough evidence to reach the conclusion, considering the accessibility in clinical practice, in our personal views, we recommend the use of brain-perfusion SPECT and MIBG myocardial scintigraphy to improve the diagnosis of DLB.

[Diagnostic value of multislice perfusion CT in dementia patients]

BACKGROUND

The diagnostic value of perfusion CT in dementia patients was retrospectively evaluated in comparison to the Mini-Mental State Examination (MMSE).

MATERIAL AND METHODS

The perfusion CT database of 55 subjects was investigated. All patients underwent an unenhanced, contrast-enhanced, and perfusion CT of the head. The clinical evaluation of the degree of dementia was performed with the MMSE. In the perfusion CT data, 24 ROI were marked. Then blood volume (BV), blood flow (BF), and mean transit time (MTT) were calculated and compared with the ipsilateral and contralateral regions and with the degree of dementia.

RESULTS

With increasing degree of dementia, a significant decrease of the occipital and temporal BV was found. A significant decrease of the BF in the frontal lobe, basal ganglia, and occipital region was found. Concurrently, the MTT increased significantly in the basal ganglia region. The group with Alzheimer's disease showed significant regional hypoperfusion compared with the group of cognitively normal subjects in the frontal, basal ganglia, occipital, and temporal region.

CONCLUSIONS

The cerebral perfusion decreased with increasing degree of dementia. The inexpensive and widely available perfusion CT reveals information about regional differences of cerebral perfusion, which may be useful in differentiating severity and types of dementia.

Neuropsychological patterns in magnetic resonance imaging-defined subgroups of patients with degenerative dementia

We hypothesized that specific neuropsychological deficits were associated with specific patterns of atrophy. A magnetic resonance imaging volumetric study and a neuropsychological protocol were obtained for patients with several frontotemporal lobar dementia phenotypes including a social/dysexecutive (SOC/EXEC, n = 17), progressive nonfluent aphasia (n = 9), semantic dementia (n = 7), corticobasal syndrome (n = 9), and Alzheimer's disease (n = 21). Blinded to testing results, patients were partitioned according to pattern of predominant cortical atrophy; our partitioning algorithm had been derived using seriation, a hierarchical classification technique. Neuropsychological test scores were regressed versus these atrophy patterns as fixed effects using the covariate total atrophy as marker for disease severity. The results showed the model accounted for substantial variance. Furthermore, the "large-scale networks" associated with each neuropsychological test conformed well to the known literature. For example, bilateral prefrontal cortical atrophy was exclusively associated with SOC/EXEC dysfunction. The neuropsychological principle of "double dissociation" was supported not just by such active associations but also by the "silence" of locations not previously implicated by the literature. We conclude that classifying patients with degenerative dementia by specific pattern of cortical atrophy has the potential to predict individual patterns of cognitive deficits.

Neuroimaging in dementia

Although dementia is a clinical diagnosis, neuroimaging often is crucial for proper assessment. Magnetic resonance imaging (MRI) and computed tomography (CT) may identify nondegenerative and potentially treatable causes of dementia. Recent neuroimaging advances, such as the Pittsburgh Compound-B (PIB) ligand for positron emission tomography imaging in Alzheimer's disease, will improve our ability to differentiate among the neurodegenerative dementias. High-resolution volumetric MRI has increased the capacity to identify the various forms of the frontotemporal lobar degeneration spectrum and some forms of parkinsonism or cerebellar neurodegenerative disorders, such as corticobasal degeneration, progressive supranuclear palsy, multiple system atrophy, and spinocerebellar ataxias. In many cases, the specific pattern of cortical and subcortical abnormalities on MRI has diagnostic utility. Finally, among the new MRI methods, diffusion-weighted MRI can help in the early diagnosis of Creutzfeldt-Jakob disease. Although only clinical assessment can lead to a diagnosis of dementia, neuroimaging is clearly an invaluable tool for the clinician in the differential diagnosis.

Cognitive phenotypes in Alzheimer's disease and genetic risk

Variation in the clinical characteristics of patients with Alzheimer's disease (AD) is increasingly recognised, although the factors underlying variation are not fully understood. The study examined the cognitive characteristics of 523 AD patients at the time of their presentation to a neurological dementia clinic and explored the relationship to family history and apolipoprotein E (APOE) genotype. Distinct profiles were identified, which were mirrored by topographical differences on neuroimaging. Clinical distinctions were maintained over time. Two-thirds of patients showed a constellation of deficits at presentation which included memory, language, visuospatial and constructional difficulties. However, a quarter had circumscribed presentations of amnesia, aphasia, perceptuospatial disorder or apraxia. The rare presence of frontal lobe characteristics was associated with a younger age of onset, an increased incidence of myoclonus at presentation, a positive family history but not with possession of APOE epsilon4 allele. An amnestic presentation (severe, yet circumscribed amnesia) was strongly associated with an older age of onset, a positive family history and the presence of APOE epsilon4 allele. Posterior cortical presentations showed a female bias, were typically sporadic, and showed no association with APOE epsilon4. The findings support the notion of phenotypic variation in AD, and show that genetic risk factors can influence clinical presentation. The findings draw attention to the specific association between APOE epsilon4 allele and memory but challenge the commonly held notion that the presence of the epsilon4 allele inevitably reduces onset age. The findings indicate that risk factors other than APOE epsilon4 allele underlie the non-familial, early onset posterior hemisphere presentations of AD.

Variability in cognitive presentation of Alzheimer's disease

The aim of the present study was to explore the nature and prevalence of phenotypic variations in Alzheimer's disease (AD). Neuropsychological profiles of a large cross-sectional cohort of patients with a clinical diagnosis of the disease were examined. All tests distinguished the AD group from controls confirming their sensitivity to the presence of early AD. Factor analysis of test scores revealed five factors, reflecting the discrete cognitive domains of memory, language, perceptuospatial abilities, executive skills, and praxis. Cluster analysis revealed distinct performance profiles that could not be accounted for by disease severity. Some patients showed an accentuation of memory impairment relative to other domains, whereas others showed relative sparing. Cognitive deficits other than memory were the salient presenting feature in a relatively high proportion of patients. A subset of the cohort (22%) showed grossly disproportionate impairments in one cognitive domain. The findings emphasise variability in presentation and indicate that distinct phenotypic variations appear to lie on a continuum rather than representing discrete forms of disease.

Accuracy of single-photon emission computed tomography in differentiating frontotemporal dementia from Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) and frontotemporal dementia (FTD) are the commonest causes of presenile dementia. In the absence of a biological marker, diagnosis is reliant on clinical evaluation. Confirmation is often sought from neuroimaging, including single-photon emission computed tomography (SPECT). Most previous SPECT studies lack pathological validation.

AIM

To examine the accuracy of SPECT in differentiating FTD from AD in patients with subsequent pathological confirmation.

METHODS

Technetium-99-labelled hexamethyl propylene amine oxime SPECT images obtained at initial evaluation in 25 pathologically confirmed cases of FTD were examined. These images were visually rated by an experienced blinded nuclear medicine consultant and compared with those of 31 patients with AD, also with pathological validation.

RESULTS

A reduction in frontal cerebral blood flow (CBF) was more common in FTD and was of diagnostic value (sensitivity 0.8, specificity 0.65 and likelihood ratio (LR) 2.25; 95% CI 1.35 to 3.77). A pattern of bilateral frontal CBF reduction without the presence of associated bilateral parietal CBF change is diagnostically more accurate (sensitivity 0.80, specificity 0.81 and +LR 4.13, 95% CI 1.96 to 8.71). Diagnostic categorisation (FTD or AD) on the basis of SPECT alone was less accurate than clinical diagnosis (based on neurology and detailed neuropsychological evaluation). One patient with FTD was initially clinically misdiagnosed as AD, owing to the lack of availability of full neuropsychological assessment. However, SPECT correctly diagnosed this patient, providing a diagnostic gain of 4%.

CONCLUSION

Technetium-99-labelled hexamethyl propylene amine oxime SPECT CBF patterns provide valuable information in the diagnosis of FTD and AD. These data can be better used as an adjunct to clinical diagnosis if pathology is to be correctly predicted in life.

La lunga attesa: towards a molecular approach to neuroimaging and therapeutics in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterised by the gradual onset of dementia. The pathological hallmarks of the disease are Aβ amyloid plaques, neurofibrillary tangles (NFT), synaptic loss and reactive gliosis. Current diagnosis of AD is made by clinical, neuropsychologic, and neuroimaging assessments. Routine structural neuroimaging evaluation with computed tomography (CT) and magnetic resonance imaging (MRI) is based on non-specific features such as atrophy, a late feature in the progression of the disease, hence the crucial importance of developing new approaches for early and specific recognition at the prodromal stages of AD. Functional neuroimaging techniques such as functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), positron emission tomography (PET) and single photon emission computed tomography (SPECT), possibly in conjuction with other related Aβ biomarkers in plasma and CSF, could prove to be valuable in the differential diagnosis of AD, as well as in assessing prognosis. With the advent of new therapeutic strategies aimed at reducing the Aβ amyloid burden in the brain, there is increasing interest in the development of MRI contrast agents and PET and SPECT radioligands that will permit the assessment of Aβ amyloid burden in vivo. - ma dov'è / la lenta processione di stagioni / che fu un'alba infinita e senza strade, / dov'è la lunga attesa e qual è il nome / del vuoto che ci invade. - Eugenio Montale.

Imaginem oblivionis: the prospects of neuroimaging for early detection of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterised by the gradual onset of dementia. The pathological hallmarks of the disease are A beta amyloid plaques, neurofibrillary tangles, and reactive gliosis. Current diagnosis of AD is made by clinical, neuropsychologic, and neuroimaging assessments. Routine structural neuroimaging evaluation is based on non-specific features such as atrophy, a late feature in the progression of the disease, hence the crucial importance of developing new approaches for early and specific recognition at the prodromal stages of AD. Functional neuroimaging techniques such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) could prove to be valuable in the differential diagnosis of AD, as well as in assessing prognosis. With the advent of new therapeutic strategies aimed at reducing the A beta amyloid burden in the brain, there is increasing interest in the development of PET and SPECT radioligands that will permit the assessment of A beta amyloid burden in vivo. From this, the prospect of specific preclinical diagnosis arises, possibly in conjunction with other related A beta biomarkers in plasma and CSF.

CT perfusion as a useful tool in the evaluation of leuko-araiosis

Background

Leuko-araiosis (LA) and dementia are common geriatric conditions but their pathogenesis and clinical significance are not completely understood. An evaluation of CT perfusion (CTP) in both these conditions can further enhance the understanding of these diseases.

Methods

Twenty-one patients with LA and 21 age-matched controls were studied with CTP and assessed for their cognitive function. The subjects were classified into four groups: Group 1, with LA (n = 21); Group 2, without LA (n = 21); Group 3, with dementia (n = 7); Group 4, without dementia (n = 11). The mean cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) values were compared between groups 1 and 2, while mean CBF values were compared between groups 3 and 4.

Results

Mean white matter CBF was considerably reduced in patients with LA in the frontal region by 42% (p = 0.000), basal ganglia by 37% (p = 0.000) and occipital region by 18% (p = 0.019). The mean white matter CBV was reduced in patients with LA in the frontal region by 36% (p = 0.000) and basal ganglia by 28% (p = 0.017). The mean white matter CBF was dramatically reduced in patients with dementia in the frontal region by 44% (p = 0.000), basal ganglia by 32% (p = 0.038) and occipital regions by 24% (p = 0.001).

Conclusion

The CTP showed reduced white matter CBF and CBV in patients with LA. This is consistent with chronic ischemia as the pathogenesis of LA. The CTP is also a potentially important technique in the diagnosis and management of dementia, because of its ability to reveal cerebral hypoperfusion.

Frontotemporal dementia

Frontotemporal dementia (FTD) is a focal clinical syndrome characterised by profound changes in personality and social conduct and associated with circumscribed degeneration of the prefrontal and anterior temporal cortex. Onset is typically in the middle years of life and survival is about 8 years. The presence of microtubule-associated-protein-tau-based pathological features in some patients and the discovery, in some familial cases, of mutations in the tau gene links FTD to other forms of tauopathy, such as progressive supranuclear palsy and corticobasal degeneration. However, more than half of all patients with FTD, including some with a strong family history, show no apparent abnormality in the tau gene or protein, indicating pathological and aetiological heterogeneity. FTD provides a challenge both for clinical management and for theoretical understanding of its neurobiological substrate.

Pathological aging of the brain: an overview

The number of elderly people is increasing rapidly and, therefore, an increase in neurodegenerative and cerebrovascular disorders causing dementia is expected. Alzheimer disease (AD) is the most common cause of dementia. Vascular dementia, dementia with Lewy bodies, and frontotemporal dementia are the most frequent causes after AD, but a large proportion of patients have a combination of degenerative and vascular brain pathology. Characteristic magnetic resonance (MR) imaging findings can contribute to the identification of different diseases causing dementia. The MR imaging protocol should include axial T2-weighted images (T2-WI), axial fluid-attenuated inversion recovery (FLAIR) or proton density-weighted images, and axial gradient-echo T2*-weighted images, for the detection of cerebrovascular pathology. Structural neuroimaging in dementia is focused on detection of brain atrophy, especially in the medial temporal lobe, for which coronal high resolution T1-weighted images perpendicular to the long axis of the temporal lobe are extremely important. Single photon emission computed tomography and positron emission tomography may have added value in the diagnosis of dementia and may become more important in the future, due to the development of radioligands for in vivo detection of AD pathology. New functional MR techniques and serial volumetric imaging studies to identify subtle brain abnormalities may also provide surrogate markers for pathologic processes that occur in diseases causing dementia and, in conjunction with clinical evaluation, may enable a more rigorous and early diagnosis, approaching the accuracy of neuropathology.

Evidence of biochemical and biomagnetic interactions in Alzheimer's disease: an MEG and MR spectroscopy study

BACKGROUND

Several neuroimaging studies have shown reliable differences between Alzheimer's disease (AD) patients and age-matched controls. However, few studies have demonstrated the interactions between neuroimaging methods for the diagnoses of AD.

OBJECTIVE

In this study, we try to elucidate the complementary nature of magnetoencephalography (MEG) and magnetic resonance spectroscopy (MRS) examinations in the assessmentof AD.

METHODS

Ten patients fulfilling the NINCDS-ADRDA criteria of probable AD, and 10 elderly individuals with no history of neurological or psychiatric illness serving as age-matched controls participated in the study. All patients and controls received an MRS, MEG and neuropsychological assessment. MEG data were obtained in the context of a working memory task, previously utilized in a similar sample of patients.

RESULTS

The AD group showed a reduced number of activity sources over left temporoparietal areas during the late portion of the evoked magnetic field (between 400-800 ms), as well as a bilateral temporoparietal increase in creatine and myoinositol concentrations, and in the myoinositol/N-acetyl-aspartate ratio. The combination of the variables 'number of dipoles during the late portion of the evoked magnetic field' and 'myoinositol/N-acetyl-aspartate ratio' accounted for 65% of the variance of the Mini Mental State Examination scores.

CONCLUSIONS

These results highlight the importance of assessing the complex brain pathology underlying AD by utilizing multiple brain examination modalities in a coordinate approach.

Qualitative neuropsychological performance characteristics in frontotemporal dementia and Alzheimer's disease

BACKGROUND

Frontotemporal dementia (FTD) and Alzheimer's disease are clinically distinct disorders, yet neuropsychological studies have had variable success in distinguishing them. A possible reason is that studies typically rely on overall accuracy scores, which may obscure differences in reasons for failure.

OBJECTIVES

To explore the hypothesis that analysis of qualitative performance characteristics and error types, in addition to overall numerical scores, would enhance the neuropsychological distinction between FTD and Alzheimer's disease.

METHODS

38 patients with FTD and 73 with Alzheimer's disease underwent assessment of language, visuospatial abilities, memory, and executive function, using a neuropsychological screening instrument and standard neuropsychological tests. In each of these cognitive domains, performance characteristics and error types were documented, in addition to numerical scores on tests.

RESULTS

Whereas comparison of neuropsychological test scores revealed some group differences, these did not occur consistently across tests within cognitive domains. However, analysis of performance characteristics and error types revealed qualitative differences between the two groups. In particular, FTD patients displayed features associated with frontal lobe dysfunction, such as concrete thought, perseveration, confabulation, and poor organisation, which disrupted performance across the range of neuropsychological tests.

CONCLUSIONS

Numerical scores on neuropsychological tests alone are of limited value in differentiating FTD and Alzheimer's disease, but performance characteristics and error types enhance the distinction between the two disorders. FTD is associated with a profound behavioural syndrome that affects performance on cognitive assessment, obscuring group differences. Qualitative information should be included in neuropsychological research and clinical assessments.

Antemortem diagnosis of frontotemporal lobar degeneration

The objective of this article is to study the accuracy of antemortem clinical diagnoses of frontotemporal lobar degenerations (FTLDs). From brain autopsies performed on subjects enrolled in the Mayo Alzheimer Center between 1991 and 2003, cases with neuropathological diagnoses of FTLD were identified. Neuropathological diagnoses of FTLDs were based on consensus criteria for FTLD. The initial clinical histories, neuropsychological test results, brain imaging studies, and initial clinical diagnoses were reviewed. There were 34 pathological FTLD cases among 433 subjects who underwent autopsy; 29 of these 34 cases were diagnosed as FTLD antemortem based on the sum of clinical, neuropsychological, and imaging features (sensitivity, 85%). The specificity was 99%. Among the 34 cases with pathological FTLD, 27 (79%) had clinical histories diagnostic of an FTLD syndrome, 20 (62%) had neuropsychological profiles consistent with FTLD, 17 (50%) had magnetic resonance scans consistent with FTLD, and 7 of 8 who had functional imaging studies had ones consistent with FTLD. In those with incorrect antemortem diagnoses, three were thought to have Alzheimer's disease, one was considered hard to classify, and one was diagnosed with vascular dementia. The antemortem consensus diagnosis of FTLD was moderately sensitive and very specific. With experienced clinicians and awareness of the unique manifestations of FTLD, accurate antemortem diagnosis was feasible.

Single-photon emission computed tomography perfusion imaging in the differential diagnosis of dementia: a retrospective regional audit

A retrospective audit of (99m)Tc-HMPAO SPECT scans was undertaken to assess the utility of brain perfusion imaging in a cohort of young cognitively impaired patients in whom diagnostic uncertainty remained after standard clinical and neuropsychological assessment and structural brain imaging. SPECT scans were assessed by five raters (two neurologists and three nuclear medicine specialists) on two occasions 6 months apart, first without any clinical data and second with brief pertinent clinical information. SPECT diagnoses were compared with criterion diagnoses subsequently established by the two neurologists with access to all clinical, neuropsychological and neuroimaging data. Despite reasonable intra- and interrater reliability, diagnostic accuracy ranged from 32 to 58%. SPECT scan normality or abnormality in blind and informed viewings gave respective sensitivities of 77 and 71%, specificities of 44 and 38%, positive predictive values of 88 and 87% and negative predictive values of 27 and 18%. Calculating pairwise disease group comparisons, likelihood ratios suggested some diagnostic gain in differentiating AD from 'not AD' and from FTD/focal syndromes. SPECT scanning was of little help in establishing diagnoses in this cohort of patients, a finding which supports the conclusion of the American Academy of Neurology evidence-based review that SPECT imaging cannot be recommended for either the initial or the differential diagnosis of suspected dementia because it has not demonstrated superiority to clinical criteria.

2-deoxy-fluorglucose–positron emission tomography imaging of the brain: Current clinical applications with emphasis on the dementias

A number of very significant advances in the field of positron emission tomography (PET) imaging are now beginning to have an impact on clinical PET brain imaging. Among the most significant advances are further improvements in PET scanner detectors and computers. Increasingly, more sophisticated methods of image analysis and quantitation are also beginning to emerge. In addition, there has been a very rapid introduction of newer PET radiotracers that will ultimately work their way into the clinical environment. Finally, there is an expanding interest in the potential of PET brain imaging in the evaluation of a wide variety of clinical neuropsychiatric conditions.

Predicting the accuracy of a diagnosis of Alzheimer's disease with 99mTc HMPAO single photon emission computed tomography

The current clinical practice of reporting images obtained with single photon emission computed tomography (SPECT) with 99mTc-d,l-hexamethylpropylene amine oxime (99mTc HMPAO) images was examined by having 16 experts evaluate the appearance of SPECT images in patients with probable Alzheimer type dementia (ATD), patients with major depressive episode (DSM-IV), and healthy volunteers. The experts rated diagnostic criteria of scan appearance in respect of importance for their individual diagnostic practice. Experts were nuclear medicine specialists, psychiatrists and physicists taking part in a European multi-centre collaborative project. They examined 158 perfusion scans and then the same perfusion scans together with statistical parametric maps (SPMs). The sensitivity of experts' diagnostic judgments was significantly and negatively correlated with the importance they attributed to reduced regional perfusion in the parietal lobes. A corresponding positive correlation was observed for diagnostic specificity against depressed and healthy volunteers. Similar results were observed with SPMs, where in addition area under the receiver operating characteristic (ROC) curve was significantly reduced with raters' increased diagnostic reliance on frontal lobe perfusion deficits. Sensitivity was greater with SPM for patients younger than 70 years and with dementia severity. The more importance experts placed on parietal (symmetrical) perfusion deficits, the less sensitive and the more specific their diagnostic judgment was. Using multiple raters in large patient samples may provide a way of identifying successful explicit diagnostic strategies for clinical image analysis.

Posterior Cingulate Hypoperfusion in Alzheimerʼs Disease, Senile Dementia of Alzheimer type, and Other Dementias Evaluated by Three-Dimensional Stereotactic Surface Projections Using Tc-99m HMPAO SPECT

Hypoperfusion in the posterior cingulate cortex is thought to be useful for the early diagnosis of dementia of Alzheimer type (DAT). In the present study, we compared the incidence of posterior cingulate hypoperfusion in patients with Alzheimer's disease (AD), patients with senile dementia of Alzheimer type (SDAT), and patients with other types of dementia, as evaluated by three-dimensional stereotactic surface projection (3D-SSP) imaging. The subjects were 20 AD patients, 20 SDAT patients, 13 frontotemporal dementia patients, and 3 other types of dementia patients. A SPECT study was performed 5 minutes after the injection of 740 MBq technetium-99m hexamethylpropylene amine oxime. 3D-SSP images were obtained with global normalization to perform the statistical analysis. The normal database of 3D-SSP consisted of 15 healthy volunteers. Hypoperfusion was considered to be significant when the Z-score was over 2.5. Posterior cingulate hypoperfusion was observed in 13 of 20 AD patients (65%), in 5 of 20 SDAT patients (25%), but in none of other type of dementia patients. Posterior cingulate hypoperfusion was considered to be a finding specific to DAT, and this finding was thought to be useful to diagnose DAT patients, especially for AD patients. However, it was considered to be difficult to diagnose early-stage SDAT patients.

Significance of non-presynaptic SPECT tracer methods in Parkinson's disease

Tropane-related tracers for SPECT and PET scanning have shown their value in assessing the in vivo striatal presynaptic status of the dopaminergic neurotransmitter system in man. Previously, there were a few other tracers suggested to be useful in the study of in vivo brain biochemistry in humans, particularly in patients afflicted with Parkinson's disease (PD) or parkinsonian syndromes. We summarize the work concerning the two main tracers applied in that context using single photon emission tomography (SPECT) scanning in patients with PD: IBZM and HMPAO. IBZM binds specifically to striatal dopamine D(2) receptors and HMPAO uptake is a measure of cerebral tissue perfusion.