Neuropsychology of memory and SPECT in the diagnosis and staging of dementia of Alzheimer type

(99m)Tc-hexamethyl propyleneamine oxime brain perfusion single photon emission computed tomography in characterization of dementia: an initial experience in Indian clinical practice

There is a growing health burden in developing countries due to recent trends of increasing incidence of neurodegenerative diseases. To reduce the healthcare cost and effective management of dementia illness, early diagnosis, accurate differentiation and their progression assessment is becoming crucially important. We are utilizing ^99mTc-d, l-hexamethyl propyleneamine oxime (HMPAO) brain perfusion single photon emission computed tomography (SPECT) to characterize dementia on the basis of perfusion patterns and observed significant improvement in their management. Eleven patients (median age of 60 years range of 53-83 years) with clinical suspicion of dementia underwent ^99mTc-HMPAO brain perfusion SPECT. SPECT-computed tomography acquisition done, data are reconstructed, reviewed in three view and further processed in “neurogam” to get voxel based analysis and the comparison with age based normal database and surface mapping. Final diagnosis was done with clinical correlation. Four patients are diagnosed as Alzheimer's disease, two as frontotemporal dementia, one as dementia of Lewy bodies, two as vascular dementia and two as pseudodementia. All imaging findings are well-correlated with clinical background. Brain perfusion SPECT with HMPAO was very helpful to us in characterizing the patients of dementia by its perfusion pattern.

Systematic review of the diagnostic utility of SPECT imaging in dementia

Single-photon emission-computed tomography (SPECT) may potentially contribute to the diagnostic work up of patients with neurodegenerative dementia. This systematic review aims to establish the diagnostic utility of 99mTc-hexamethylpropyleneamine (99mTc-HMPAO) and 99mTc-ethylcysteine dimer SPECT in distinguishing between Alzheimer's disease (AD) and frontotemporal dementia (FTD), AD and vascular dementia (VD), AD and dementia with Lewy bodies (DLB), and AD and normal controls (NC). We searched MEDLINE and Embase databases via OVID for articles from January 1985 to May 2012 and identified additional studies from reviews and references. Of 755 studies, 49 studies met the inclusion and exclusion criteria for this systematic review; AD versus FTD (n=13), AD versus VD (n=18), AD versus DLB (n=5), and AD versus NC (n=18). We compiled relevant data and graded the studies with an internal and external validity criteria checklist. We pooled the studies with a clinical diagnosis and those using 99mTc-HMPAO SPECT in a meta-analysis, calculating the pooled weighted sensitivity, specificity, likelihood ratios, and diagnostic odds ratios using DerSimonian-Laird random-effects model. The pooled weighted sensitivity and specificity of 99mTc-HMPAO-SPECT in distinguishing clinically diagnosed AD from FTD are 79.7 and 79.9%, respectively, AD from VD are 74.5 and 72.4%, AD from DLB are 70.2 and 76.2%, and AD from NC are 76.1 and 85.4%. SPECT does have diagnostic value, particularly in differentiating Alzheimer's disease from frontotemporal dementia and normal controls; however, it should not be used in isolation, rather as an adjunct, and interpreted in the context of clinical information and paraclinical test results.

Initial mini-mental state and cerebral perfusion in Alzheimer's disease

PURPOSE

The relationship between the initial mini-mental state examination (MMSE) score and cerebral perfusion was evaluated in patients with Alzheimer's disease (AD).

METHODS

In the study single photon emission computed tomography (SPECT) images of the brains of 40 AD patients were compared with the brain scans of 10 healthy controls. Each patient underwent MMSE analysis at initial evaluation as well as Tc-99 m hexamethylpropyleneamine oxine (HMPAO) brain SPECT. The patients were followed up for at least 42 months.

RESULTS

The regional cerebral blood flow (rCBF) values for patients were found to be significantly decreased for all cerebral lobes compared to the control subjects and p-values were calculated to be less than 0.001 except for occipital lobes. The most statistically significant correlation between the MMSE scores and rCBF values was determined for the left temporal lobe (p < 0.0001). A significant correlation was also found for the right temporal lobe (p < 0.005). A minimal statistically significant correlation was found for the frontal lobes and the left parietal lobe (p < 0.05).

CONCLUSIONS

The overall cerebral perfusion was decreased except in the occipital lobes in AD cases with low initial MMSE scores and there was a significant relationship between the decrease in perfusion of the temporal/frontal lobes and the left parietal lobe with the decrease in the initial MMSE scores. The most significant relationship between the decrease in the initial MMSE scores and the rCBF values was determined for the temporal lobes (especially for the left temporal lobe). It was also found that the left frontal lobe was affected from the beginning of the disease.

[Use of CSF biomarkers in the diagnosis of Alzheimer's disease in clinical practice]

INTRODUCTION

The diagnosis of Alzheimer's disease (AD) currently relies on clinical criteria that are primarily based on the presence of an amnestic syndrome of the mesial temporal lobe type. In recent years, new diagnostic tools have been developed, such as the possibility of measuring a set of proteins directly involved in the pathophysiological process of AD. A profile suggestive of AD has been defined, characterized by decreased beta-amyloid peptide, combined with increased Tau protein and phopho-Tau.

STATE OF KNOWLEDGE

According to current data available in the medical literature, the potential usefulness of CSF biomarkers in the common forms of AD fulfilling usual clinical criteria remains modest. In contrast however, they could be of significant help in the diagnosis of early-onset AD, in particular in atypical forms with prominent non-memory impairment (involving vision, language or behavior). In addition, due to their close relationship with the pathological process, they bring useful prognosis information upon the aggressiveness of the disease.

CONCLUSION AND PERSPECTIVE

Taken together, in the current state of knowledge, use of CSF biomarkers in clinical practice should first be recommended for the assessment of early-onset cognitive disturbances, in particular when initial symptoms are of a non-memory type. Their development, however, offers new avenues in the fields of clinical and pharmacological research.

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.

The Cambridge Semantic Memory Test Battery: detection of semantic deficits in semantic dementia and Alzheimer's disease

The aims of this study were (a) to explore the utility of, and make more widely available, an updated and extended version of the Cambridge Semantic Memory test battery, and (b) to use this battery in conjunction with other tests to characterise the profile of several different forms of progressive cognitive impairment: semantic dementia (SD, n = 15), mild cognitive impairment (MCI, n = 7), established Alzheimer's disease (AD) (n = 8), all in comparison to normal controls (n = 45). The semantic battery is useful in a variety of ways for exploring the nature of semantic deficits; on its own, however, it does not provide sensitive differentiation between patients with AD and SD. An assessment including measures of episodic memory and visuospatial abilities as well as the semantic battery is recommended for good characterisation of the cognitive profiles associated with SD and AD.

Mapping of subcortical white matter abnormality in Alzheimer's disease using diffusion-weighted magnetic resonance imaging

RATIONALE AND OBJECTIVES

White matter (WM) abnormality in Alzheimer's disease (AD) has been less well characterized than cortical damage. We studied the spatial distribution of the subcortical WM abnormality using diffusion-weighted magnetic resonance imaging (DWI).

MATERIALS AND METHODS

Twenty-one AD patients and seven healthy, elderly subjects were included. DWIs were obtained using a cerebrospinal fluid (CSF)-nulled pulse sequence to reduce the partial volume contamination of CSF signal. Diffusivity in the subcortical WM voxels was mapped onto the cortical surface using original software so that the spatial distribution of subcortical WM damage, which was visualized as an area of increased diffusivity, could be viewed in a three-dimensional map. The damages in the lateral surface of the bilateral cerebral hemispheres were visually evaluated, and severities of the damages in five brain regions were compared with each other. In addition, the severity of the damage in each region was correlated with patient's mini-mental state examination (MMSE) score.

RESULTS

In both hemispheres, clear sparing of the pericentral regions and predominant involvement of the parietal and temporal regions were revealed with statistical significance (P < .05, respectively). Marginal correlation (P < .05 uncorrected for multiple comparisons) was observed between the damage severity in the bilateral frontal and right temporal regions and patient's MMSE score.

CONCLUSION

We demonstrated a subcortical WM abnormality over the parietal and temporal regions with clear sparing of the pericentral region using our mapping method, which supported the hypothesis that the subcortical WM abnormality in AD originates in Wallerian degeneration.

Regional cerebral blood flow deficits in mild Alzheimer's disease using high resolution single photon emission computerized tomography

In spite of its wide availability, single photon emission computerized tomography (SPECT) scanning is uncommonly used in the assessment of Alzheimer's disease (AD) and related dementias. In light of recent advances in scanning protocols and image analysis, SPECT needs to be re-examined as a tool in the diagnosis of dementia. A total of 18 subjects with early AD and 10 healthy elderly control subjects were examined with high resolution SPECT during the performance of a simple word discrimination task. SPECT images were coregistered with individual magnetic resonance imaging scans, allowing delineation of predetermined neuroanatomical Regions of Interest (ROI). There was a gradation of regional cerebral blood flow (rCBF) values in both groups, with the lowest values being in the hippocampus and the highest in the striatum, thalamus and cerebellum. Compared to healthy controls, AD subjects demonstrated lower relative rCBF in parietal and prefrontal cortices. Analysis of individual ROI demonstrated bilateral reduction of rCBF in prefrontal poles, posterior temporal and anterior parietal cortex, and unilateral reduction of rCBF in left dorsolateral prefrontal cortex, right posterior parietal cortex and the left cingulate body. There were no significant differences for hippocampal, occipital or basal ganglia rCBF. Discriminant function analysis indicated that rCBF in the prefrontal polar regions achieved the best classification of cases. SPECT has utility in the diagnostic assessment of AD if standardized and semiquantitative techniques are used.

[18F]FDG-PET in patients with Alzheimer's disease: marker of disease spread

BACKGROUND

It is not known yet whether temporoparietal glucose hypometabolism in patients with probable Alzheimer's disease (AD) reflects disease severity or different subtypes of patients.

METHODS

Twenty-five subjects with mild probable AD [NINCDS-ADRDA criteria; age 65.8 +/- 9.3 years (mean +/- SD); Mini-Mental State Examination (MMSE) 26.0 +/- 3.3] were investigated. [(18)F]FDG-PET data were analyzed visually with raters blinded to the diagnosis and with a quantitative analysis in the region of interest on individual anatomically normalized PET scans.

RESULTS

Thirteen of 25 patients showed temporoparietal hypometabolism on visual inspection (PET+; age 65.7 +/- 10.7), 12 patients had normal FDG-PET results (PET-; age 65.9 +/- 8.0; n.s.). The MMSE and immediate reproduction of the Wechsler Memory Scale (WMS-R-I) were 27.7 +/- 1.9 and 31.1 +/- 6.1 in the PET- vs. 24.5 +/- 3.6 (p = 0.012) and 22.0 +/- 7.4 (p = 0.006) in the PET+ group. Immediate and delayed recall in the California Verbal Learning Test and delayed reproduction in the Wechsler Memory Scale were alike. Regression analysis revealed a significant correlation of temporoparietal glucose metabolism with the block span (r = 0.60; p < 0.01) and the WMS-R-I (r = 0.68; p < 0.01) but not with measures of hippocampal function.

CONCLUSIONS

Temporoparietal glucose metabolism in patients with very mild AD is a sign of disease spread beyond the temporal lobe. This may aid in establishing objective parameters for future therapeutic studies.

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.

Correlation of neuropsychological evaluation and SPECT imaging in patients with Alzheimer's disease

BACKGROUND

Mini-Mental State Examination (MMSE) is a very useful tool for diagnosing changes in cognitive functions by the general practitioner or other medical staff who is not familiar with neuropsychological tests. On the other hand, HMPAO brain SPECT has been shown to have a high sensitivity to detect neurodegenerative processes, which lead to dementia. The correlation between both methods is unknown. We compared both methods in order to find a rational evaluation tool for the practitioner to obtain a higher efficacy and cost effective way of using both methods.

PATIENTS AND METHODS

Fifty-one patients diagnosed as having Alzheimer's disease (AD) were examined. Each patient underwent MMSE analysis, as well as HMPAO brain SPECT. The severity of SPECT abnormalities was categorized into mild, moderate and severe. Statistical analysis was performed in order to evaluate the correlation between imaging findings and neuropsychological testing.

RESULTS

Marginal inverse correlation was found between global MMSE SPECT imaging on right and left side (p = 0.05) and the left temporal region (p = 0.05). MMSE subgroup component of orientation was highly significantly inversely associated with SPECT imaging of right and left frontal region (p > 0.0001). The MMSE subgroup of immediate memory was significantly correlated to left and right temporal regions (p = 0.001 and p = 0.002 respectively). Age was not significantly correlated to global MMSE or any of its subtest components.

CONCLUSION

MMSE score has no linear correlation to SPECT perfusion findings. In cases of abnormal orientation score subgroup SPECT imaging is not recommended. In most instances, a combination of both methods should be employed by the general practitioner for further evaluation of dementia.

A meta-analysis of structural and functional brain imaging in dementia of the Alzheimer's type: a neuroimaging profile

We conducted a quantitative review of the imaging literature using meta-analytic methodology to characterize further the magnitude of hippocampal deficit in probable Alzheimer's disease (AD) and to determine whether other neuroanatomic structures in AD can better discriminate the disease from normal aging. Additionally, we parceled the discriminability of neuroanatomic structures by duration of disease to determine those structures most sensitive to AD in its early and late stages. One hundred twenty-one studies published between 1984 and 2000 met criteria for inclusion in the present analysis. In total, structural (i.e., CT and MRI) and functional (i.e., SPECT and PET) neuroimaging results from 3511 patients with AD, and 1632 normal healthy controls were recorded across meta-analyses. Our results include neuroimaging profiles for both early onset and longer duration patients with AD. In sum, these profiles yield a signature of diagnostic markers in both cortical and subcortical neuroanatomic areas. This signature is consistent with the clinical phenomenology of Alzheimer's dementia and should aid in the positive identification of AD.

Suppression of false recognition in Alzheimer's disease and in patients with frontal lobe lesions

Previous research has shown that patients with Alzheimer's disease show increasing levels of false recognition across five repeated study-test trials of semantic associates. The present study tested the hypotheses that (i) the increasing false recognition was partly due to the frontal lobe dysfunction of patients with Alzheimer's disease, and (ii) a failure of source monitoring was the central mechanism by which frontal lobe dysfunction led to increasing false recognition across trials. In Experiment 1, patients with frontal lobe lesions and controls were examined in the same repeated trials paradigm as that used previously in patients with Alzheimer's disease. Although controls were able to reduce their false recognition across trials, the patients with frontal lobe lesions were not, and instead showed a constant level of elevated false recognition across the study-test trials. In Experiment 2, two groups of patients with Alzheimer's disease and healthy older adult controls were studied: the first group was given a single study session followed by a recognition test, the second group was given five study sessions followed by a single recognition test. Older adults who were exposed to five study lists demonstrated lower levels of false relative to true recognition, whereas patients with Alzheimer's disease in this condition exhibited levels of false recognition elevated to that of their true recognition, even with the source memory confusion of intervening tests eliminated. The authors suggest that impairment in aspects of frontal lobe function, such as verification-inhibition mechanisms, probably contributes to the inability of patients with Alzheimer's disease to suppress their false recognition across repeated trials. Lastly, it is speculated that one way in which the frontal lobes enable normal episodic memory function is by facilitating the suppression of false recognition and other distortions of memory.

Is knowledge of famous people disproportionately impaired in patients with early and questionable Alzheimer's disease?

Twenty-two patients with early dementia of Alzheimer's type (DAT) and 31 controls were administered tests of person-specific semantics (Experiment 1). DAT patients were impaired on all test components. In Experiment 2, 31 DAT patients, 28 questionable DAT (QDAT) patients, and 42 controls were administered the Graded Naming Test (GNT) and the newly designed Graded Faces Test (GFT), matched for difficulty with the GNT. DAT patients were impaired throughout but showed an advantage for naming objects over faces. The QDAT patients were impaired on the GFT only. Of the 7 QDAT patients who evolved to DAT within 1-2 years, 6 showed initial impairment on the GFT, whereas 17 of the nonconverters scored normally on the GFT. Results suggest greater and earlier vulnerability of person knowledge than general semantic knowledge in DAT.

Single photon emission CT and positron emission tomography in the evaluation of neurologic disease

Widely available SPECT allows imaging of certain critical components of neurotransmission, providing clinically and experimentally significant information. Future efforts may be directed toward developing innovative techniques to delineate dynamic neurochemical changes in vivo.

Dementia with Lewy bodies: a pure case

A pure case of autopsy-confirmed dementia with Lewy bodies (DLB) is described. The patient presented with distinctive verbal fluency deficits in the context of mild language impairment, intact recognition memory, and impaired paragraph recall. Neuroimaging (CT and SPECT) showed progressive medial temporal lobe atrophy. Neuropathology revealed Lewy bodies, degeneration in the substantia nigra, nucleus basalis of Meynert (Nakano & Hirano, 1984), and locus ceruleus, but no pathology characteristic of Alzheimer's disease. It is in this sense that the case is "pure" DLB. Early neuropsychological diagnosis of DLB is essential (Salmon et al., 1996) given the potentially fatal hazard of neuroleptics (McKeith et al., 1992) and the difficulties associated with clinical neurological diagnoses (Litvan et al., 1998).

Sex differences in brain-behavior relationships between verbal episodic memory and resting regional cerebral blood flow

Women have better verbal memory, and higher rates of resting regional cerebral blood flow (rCBF). This study examined whether there are also sex differences in the relationship between verbal episodic memory and resting rCBF. Twenty eight healthy right-handed volunteers (14 male, 14 female) underwent a neuropsychological evaluation and a Positron Emission Tomography (PET) (15)O-water study. Immediate and delayed recall was measured on the logical memory subtest of the Wechsler Memory Scale - Revised (WMS-R), and on the California Verbal Learning Test (CVLT). Resting rCBF (ml/100 g/min) was calculated for four frontal, four temporal, and four limbic regions of interest (ROIs). Women had better immediate recall on both WMS-R and CVLT tasks. Sex differences in rCBF were found for temporal lobe regions. Women had greater bilateral blood flow in a mid-temporal brain region. There were also sex differences in rCBF correlations with performance. Women produced positive correlations with rCBF laterality in the temporal pole. Greater relative CBF in the left temporal pole was associated with better WMS-R immediate and delayed recall in women only. These results suggest that trait differences in temporal pole brain-behavior relationships may relate to sex differences in verbal episodic memory.

Specific temporoparietal gyral atrophy reflects the pattern of language dissolution in Alzheimer's disease

The aim of this study was to determine the topography and degree of atrophy in speech and language-associated cortical gyri in Alzheimer's disease. The post-mortem brains of 10 patients with pathologically confirmed Alzheimer's disease and 21 neurological and neuropathological controls were sectioned in serial 3 mm coronal slices and grey and white matter volumes were determined for specific cortical gyri. All Alzheimer's disease patients had prospectively documented impairments in verbal and semantic memory with concomitant global decline. The cortical regions of interest included the planum temporale, Heschl's gyri, the anterior superior temporal gyri, the middle and inferior temporal gyri, area 37 at the inferior temporoparietal junction, areas 40 and 39 (supramarginal and angular gyri) and Broca's frontal regions. Although most patients had end-stage disease, the language-associated cortical regions were affected to different degrees, with some regions free of atrophy. These included Broca's regions in the frontal lobe and Heschl's gyri on the superior surface of the temporal lobe. In contrast, the inferior temporal and temporoparietal gyri (area 37) were severely reduced in volume. The phonological processing regions in the superior temporal gyri (the planum temporale) were also atrophic in all Alzheimer's disease patients while the anterior superior temporal gyri were only atrophic in female patients. Such atrophy may underlie the more severe language impairments previously described in females with Alzheimer's disease. The present study is the first to analyse the volumes of language-associated gyri in post-mortem patients with confirmed Alzheimer's disease. The results show that atrophy is not global but site-specific. Atrophied gyri appear to reflect a specific network of language and semantic memory dissolution seen in the clinical features of patients with Alzheimer's disease. Females showed greater atrophy than males in the anterior superior temporal gyri.

Clinical features of frontal lobe dementia in comparison to Alzheimer's disease

Over the past decade it has become evident that a substantial minority of patients with primary dementing diseases, particularly those presenting in the presenium, have dementia of frontal lobe type (DFT) due to non-Alzheimer's pathology. Although post-mortem remains the only method of definitive diagnosis, DFT and Alzheimer's disease (AD) can, we would claim, be separated with a high degree of certainty based on a combination of informant history, neuropsychology and neuroimaging. In DFT, changes in personality, motivation, social interaction and organisational abilities, in the presence of well preserved memory and visuospatial abilities, are characteristic. The lack of insight emphasises the need for independent information particularly as patients may perform normally on bedside (and more sophisticated) tests of cognition. Psychiatric features especially mood disturbance appear to be common, but their prevalence remains to be established. In contrast, AD is a progressive amnestic disorder with episodic and semantic memory deficits, followed by breakdown in other attentional, perceptual and visuo-spatial abilities, which reflects the major locus of pathology in AD, namely the medial temporal lobe. These features are illustrated by reference to a longitudinal study of 52 patients with minimal to moderate AD. In addition, we shall describe the results of retrospective and prospective neuropsychiatric studies of a group of DFT patients.