A voxel-based analysis of cerebral perfusion in dementia and depression of old age

Trajectories in Cerebral Blood Flow Following Antidepressant Treatment in Late-Life Depression: Support for the Vascular Depression Hypothesis

OBJECTIVE

Studies have identified longitudinally that there exists an association between depression, cerebral blood flow (CBF), and white matter hyperintensities that are thought to be due to vascular pathologies in the brain. However, the changes in CBF, a measure that reflects cerebrovascular integrity, following pharmacotherapy are not well understood. In this study, we investigated the dynamic CBF changes over the course of antidepressant treatment and the association of these changes with depressive symptoms.

METHODS

We used pseudocontinuous arterial spin labeling to investigate CBF changes in a sample of older patients (≥ 50 years of age; N = 46; 29 female) with a DSM-IV diagnosis of major depressive disorder. Participants had 5 magnetic resonance imaging scans (at baseline, the day after receiving a placebo, the day after receiving a first dose of venlafaxine, a week after starting venlafaxine treatment, and at the end of trial [12 weeks]). Montgomery-Asberg Depression Rating Scale (MADRS) was used to evaluate depression severity and treatment outcome. We investigated the association between changes in depression severity with changes in voxel-wise CBF while adjusting for potential confounding factors.

RESULTS

Increased CBF in the middle and posterior cingulate between baseline and end of treatment was significantly associated with percent decrease in MADRS score, independent of sex and Mini-Mental State Examination score (5,000 permutations, cluster forming threshold P < .005, family-wise error P < .05). No significant effects were detected between baseline and other scans (ie, placebo, acute [single dose], or subacute [after a week]).

CONCLUSIONS

Regional CBF increases were associated with decreases in depressive symptoms. This observation is consistent with the vascular depression hypothesis in late-life depression.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers: NCT00892047 and NCT01124188.

Cortical changes associated with depression and antidepressant use in Alzheimer and Lewy body dementia: an MRI surface-based morphometric study

CONTEXT

Depression is common in dementia, especially in the early stages, with important clinical implications, but the etiology is unknown and most likely heterogeneous. Antidepressant use in the elderly without dementia has previously been shown to be associated with high risks of adverse events and with structural brain alterations.

OBJECTIVE

To investigate cortical changes associated with depression and antidepressant use in patients with mild Alzheimer's disease (AD) and Lewy body dementia (LBD).

METHODS

74 subjects with mild AD and LBD from geriatric and psychiatry outpatient clinics in Western Norway were included. The Montgomery-Asberg Depression Rating Scale (MADRS) was used to assess depression. Automatic preprocessing using Freesurfer included steps for white and grey matter surface reconstruction. The resulting cortical thickness was analyzed using linear modeling.

RESULTS

Clusters of depression-associated thinning were found in prefrontal and temporal areas. Treatment-associated thinning was observed in the parahippocampal region and was significant even after correction for age, sex, AD/LBD diagnosis, and MADRS scores.

CONCLUSION

Depression in mild AD and LBD is associated with cortical thinning in prefrontal and temporal areas. The findings suggest that depressive symptoms in mild dementia could develop due to neurodegeneration in the same neural circuits that are critical for depression across different brain disorders. Antidepressant use in patients with mild AD and LBD is associated with parahippocampal thinning. Taken together with low efficacy of antidepressants in cognitively impaired patients and high risks of adverse events, our results suggest a need to re-evaluate the treatment approaches for depression and the role of antidepressants in patients with dementia.

The interactive effects of cerebral perfusion and depression on cognitive function in older adults with heart failure

OBJECTIVE

Depression is common among persons with heart failure (HF) and has been linked to cognitive impairment in this population. The mechanisms of this relationship are unclear, and the current study examined whether cerebral perfusion moderates the association between depressive symptoms and cognitive impairment in patients with HF.

METHODS

Persons with HF (n = 89; mean [standard deviation] age = 67.61 [11.78] years) completed neuropsychological testing and impedance cardiography. Depressive symptoms were assessed using the Beck Depression Inventory II, and transcranial Doppler was used to quantify cerebral perfusion.

RESULTS

Depression was associated with reduced performance on tasks assessing attention/executive function (r = -0.28), language (r = -0.0.30), and motor function (r = -0.28) in unadjusted models (p values <.05). Global cerebral blood flow was correlated with memory performance (r = 0.22, p = .040) but not with other tasks. A moderation analysis was performed using hierarchical regression models for attention/executive function, memory, language, and motor function. For each model, medical and demographic characteristics were entered into the initial blocks, and the final block consisted of an interaction term between global cerebral blood flow velocity and the Beck Depression Inventory II. The interaction between greater depressive symptoms and decreased global cerebral blood flow velocity was associated with greater deficits in attention/executive function (β = .32, ΔR(2) = 0.08, p = .003).

CONCLUSIONS

Depressive symptoms and cerebral hypoperfusion interact to adversely affect cognitive performance in older adults with HF. Longitudinal studies are needed to clarify this relationship and elucidate subsequent neuropathology.

The vascular depression hypothesis: mechanisms linking vascular disease with depression

The 'Vascular Depression' hypothesis posits that cerebrovascular disease may predispose, precipitate or perpetuate some geriatric depressive syndromes. This hypothesis stimulated much research that has improved our understanding of the complex relationships between late-life depression (LLD), vascular risk factors, and cognition. Succinctly, there are well-established relationships between LLD, vascular risk factors and cerebral hyperintensities, the radiological hallmark of vascular depression. Cognitive dysfunction is common in LLD, particularly executive dysfunction, a finding predictive of poor antidepressant response. Over time, progression of hyperintensities and cognitive deficits predicts a poor course of depression and may reflect underlying worsening of vascular disease. This work laid the foundation for examining the mechanisms by which vascular disease influences brain circuits and influences the development and course of depression. We review data testing the vascular depression hypothesis with a focus on identifying potential underlying vascular mechanisms. We propose a disconnection hypothesis, wherein focal vascular damage and white matter lesion location is a crucial factor, influencing neural connectivity that contributes to clinical symptomatology. We also propose inflammatory and hypoperfusion hypotheses, concepts that link underlying vascular processes with adverse effects on brain function that influence the development of depression. Testing such hypotheses will not only inform the relationship between vascular disease and depression, but also provide guidance on the potential repurposing of pharmacological agents that may improve LLD outcomes.

The value of ethyl cysteinate dimer single photon emission computed tomography in predicting antidepressant treatment response in patients with major depression

OBJECTIVE

The purpose of this study is to examine whether the reversal of compromised regional cerebral blood flow (rCBF) in older patients with major depressive disorder (MDD) is dependent on specific parameters of selective serotonin reuptake inhibitor (SSRI) treatment and to examine the efficacy of such treatment.

METHODS

Forty-five patients with moderate MDD were studied following 8 weeks of treatment with SSRIs. Twelve patients displayed a positive response to SSRIs, whereas 33 patients did not respond to SSRI treatment. A comparison group of 30 healthy volunteers was also studied. The age of all participants was greater than 50 years. Age, gender, and the Hamilton Rating Scale for Depression scores were examined. The rCBF was assessed using 99mTc-ethyl cysteinate dimer single photon emission computed tomography after SSRI treatment.

RESULTS

The rCBF levels in the right middle frontal cortex in non-responsive MDD patients were lower compared with responsive MDD patients. Compared with healthy controls, non-responders had significantly lower rCBF levels in the bilateral middle frontal cortex and insula and had significantly higher rCBF levels in the bilateral inferior frontal cortex and left middle temporal cortex. Compared with healthy controls, responders had significantly higher rCBF levels in the left inferior frontal, middle temporal, precentral, and fusiform gyrus. We found no changes in single photon emission computed tomography between pre-treatment and post-treatment stages for the responders to SSRI treatment.

CONCLUSION

Hypoperfusion in older, non-responsive MDD patients was primarily localized in the middle frontal cortex. It is possible that the responders to SSRI treatment at baseline already displayed higher rCBF values in the frontal regions.

Quantitative evaluation of Alzheimer's disease

Alzheimer's disease (AD) can be definitively diagnosed only by histopathologic examination of brain tissue; the identification and differential diagnosis of AD is especially challenging in its early stages. Neuroimaging is playing an increasingly relevant role in the identification and quantification of AD in vivo, especially in the preclinical stages, when therapeutic intervention could be more effective. Neuroimaging enables quantification of brain volume loss (structural imaging), detection of early cerebral dysfunction (functional imaging), probing into the finest cerebral structures (microstructural imaging), and investigation of amyloid plaque and neurofibrillary tangle build-up (amyloid imaging). Throughout the years, several imaging tools have been developed, ranging from simple visual rating scales to sophisticated computerized algorithms. As recently revised criteria for AD require quantitative evaluation of biomarkers mostly based on imaging, this paper provides an overview of the main neuroimaging tools which might be used presently or in the future in routine clinical practice for AD diagnosis.

Changes in regional cerebral blood flow following antidepressant treatment in late-life depression

OBJECTIVE

Reversible/irreversible abnormalities of regional cerebral blood flow (rCBF) are seen in patients with depression. However, in late-life depression there is little evidence of a longitudinal change in rCBF through remission. We examined whether the decreased rCBF in individuals with late-life depression resolves following treatment.

METHODS

Twenty-five depressed patients older than 55 years completed the Hamilton Rating Scale for Depression and single photon emission computed tomography before and after a mean of 13.7 weeks of pharmacotherapy. Quantitative analyses were performed using the Statistical Parametric Mapping procedure.

RESULTS

Patients with depression demonstrated decreased rCBF in the anterior ventral and dorsal medial prefrontal cortex (PFC), including anterior cingulate cortices, bilateral ventrolateral PFC to temporal cortices, and bilateral medial to lateral parieto-occipital lobes relative to healthy controls. No particular areas showed increased rCBF. Following pharmacotherapy, rCBF significantly increased in the left dorsolateral PFC to precentral areas and the right parieto-occipital regions. However, decreased rCBF at baseline in the anterior ventral/dorsal medial PFC, bilateral ventrolateral PFC, bilateral temporal lobes, and bilateral parietal lobes did not show significant improvement after treatment.

CONCLUSIONS

Remarkable improvements in rCBF in the left dorsolateral PFC to precentral regions are consistent with the hypothesis that neuronetworks including the left frontal cortex may be functionally and reversibly involved in late-life unipolar major depression (state-dependent). In contrast, neural circuits including bilateral medial, dorsolateral, and parietal areas may reflect underlying and continuous pathognomonic brain dysfunction of depression (trait-dependent).

Prevalence of major depressive disorder and dementia in psychogeriatric outpatients

The relationship between depression and dementia in the elderly has been widely investigated, but the real interplay between these variables is still not clear. This observational study highlights the influence of some basic variables, such as sex and age, in the development of dementia and major depression. It shows (i) the importance of sex in the age of onset of depression and dementia, (ii) the presence of two types of depressive syndrome, the first linked to the development of dementia, the second as reactive depression; (iii) the need for more attention to depressive symptoms in young-elderly men.

Neuroimaging in late-life depression

Late-life depression may be associated with vasculopathy. Neuroimaging has been a critical tool in exploring the relationship between this form of depression and vascular factors. Magnetic resonance imaging has been the most widely used tool, but there is potential to use other structural imaging techniques as well as functional neuroimaging methodologies. Neuroimaging may potentially be utilized at some point as a biomarker for late-life depression, thus helping with diagnosis and guiding treatment.

Brain glucose metabolism in the early and specific diagnosis of Alzheimer's disease. FDG-PET studies in MCI and AD

The demographics of aging suggest a great need for the early diagnosis of dementia and the development of preventive strategies. Neuropathology and structural MRI studies have pointed to the medial temporal lobe (MTL) as the brain region earliest affected in Alzheimer's disease (AD). MRI findings provide strong evidence that in mild cognitive impairments (MCI), AD-related volume losses can be reproducibly detected in the hippocampus, the entorhinal cortex (EC) and, to a lesser extent, the parahippocampal gyrus; they also indicate that lateral temporal lobe changes are becoming increasingly useful in predicting the transition to dementia. Fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) imaging has revealed glucose metabolic reductions in the parieto-temporal, frontal and posterior cingulate cortices to be the hallmark of AD. Overall, the pattern of cortical metabolic changes has been useful for the prediction of future AD as well as in distinguishing AD from other neurodegenerative diseases. FDG-PET on average achieves 90% sensitivity in identifying AD, although specificity in differentiating AD from other dementias is lower. Moreover, recent MRI-guided FDG-PET studies have shown that MTL hypometabolism is the most specific and sensitive measure for the identification of MCI, while the utility of cortical deficits is controversial. This review highlights cross-sectional, prediction and longitudinal FDG-PET studies and attempts to put into perspective the value of FDG-PET in diagnosing AD-like changes, particularly at an early stage, and in providing diagnostic specificity. The examination of MTL structures, which has so far been exclusive to MRI protocols, is then examined as a possible strategy to improve diagnostic specificity. All told, there is considerable promise that early and specific diagnosis is feasible through a combination of imaging modalities.

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.

Imaging Alzheimer's disease: clinical applications

Extensive PET imaging research on AD has been conducted since PET scanners became available in the early 1980s. PET imaging using FDG, now commercially available, can detect early metabolic changes in AD and differential metabolic features of various dementing disorders. Image analysis techniques have also advanced in the field of functional brain imaging and permit accurate and consistent scan interpretation. PET studies that involve autopsy-confirmed cases suggest that the PET diagnosis of AD is no worse or may even be better than clinical diagnosis. Limited prospective studies demonstrated the effects of PET imaging in dementia management, which precludes the approval of FDG PET for more widespread, reimbursable use. Further evidence for the efficacy of PET imaging through well-organized clinical studies, as well as continuing efforts in technologic development and basic research to characterize functional alterations in dementing disorders in living patients, are equally important to achieve the goal of better dementia care.

Prognostic value of frontal functional neuroimaging in late-onset severe major depression

BACKGROUND

There is growing evidence of a relationship between frontal neuroimaging and neuropsychological abnormalities and the physiopathology and course of late-onset major depression.

AIMS

To assess acute antidepressant response in late-onset major depression in relation to baseline frontal perfusion ratios.

METHOD

A 99mTc HMPAO single photon emission computed tomographic brain scan was performed in medication-free patients with late-onset major depression, who were then included in a 12-week antidepressant treatment regimen. Logistic regression was used to define a predictive model of non-remission.

RESULTS

A total of 47 patients completed the study, 34 of whom were classed as remitters and 13 as non-remitters. The variable left anterior fronto-cerebellar perfusion ratio had a global predictive power of 87%. Analysing this variable together with the baseline variables age of onset and duration of index episode, the predictive power of the model rose to 94%.

CONCLUSIONS

Our study suggests that a specific frontal functioning could predict the acute antidepressant response in late-onset severe major depression.

Principal component and volume of interest analyses in depressed patients imaged by 99mTc-HMPAO SPET: a methodological comparison

Previous regional cerebral blood flow (rCBF) studies on patients with unipolar major depressive disorder (MDD) have analysed clusters of voxels or single regions and yielded conflicting results, showing either higher or lower rCBF in MDD as compared to normal controls (CTR). The aim of this study was to assess rCBF distribution changes in 68 MDD patients, investigating the data set with both volume of interest (VOI) analysis and principal component analysis (PCA). The rCBF distribution in 68 MDD and 66 CTR, at rest, was compared. Technetium-99m d, l-hexamethylpropylene amine oxime single-photon emission tomography was performed and the uptake in 27 VOIs, bilaterally, was assessed using a standardising brain atlas. Data were then grouped into factors by means of PCA performed on rCBF of all 134 subjects and based on all 54 VOIs. VOI analysis showed a significant group x VOI x hemisphere interaction ( P<0.001). rCBF in eight VOIs (in the prefrontal, temporal, occipital and central structures) differed significantly between groups at the P<0.05 level. PCA identified 11 anatomo-functional regions that interacted with groups ( P<0.001). As compared to CTR, MDD rCBF was relatively higher in right associative temporo-parietal-occipital cortex ( P<0.01) and bilaterally in prefrontal ( P<0.005) and frontal cortex ( P<0.025), anterior temporal cortex and central structures ( P<0.05 and P<0.001 respectively). Higher rCBF in a selected group of MDD as compared to CTR at rest was found using PCA in five clusters of regions sharing close anatomical and functional relationships. At the single VOI level, all eight regions showing group differences were included in such clusters. PCA is a data-driven method for recasting VOIs to be used for group evaluation and comparison. The appearance of significant differences absent at the VOI level emphasises the value of analysing the relationships among brain regions for the investigation of psychiatric disease.

Statistical parametric mapping of (99m)Tc-HMPAO-SPECT images for the diagnosis of Alzheimer's disease: normalizing to cerebellar tracer uptake

BACKGROUND

For a quantitative comparison of images obtained during (99m)Tc-hexamethylpropylene amine oxime (HMPAO) single-photon emission computed tomography (SPECT), brain activity values are usually normalized to a reference region. In studies of Alzheimer-type dementia (ATD), the cerebellum is often used as a reference region, assuming that it is spared any major pathological involvement. Statistical parametric mapping (SPM) may enhance the evaluation of SPECT scans in ATD patients. However, current SPM software only allows scaling to average whole brain activity (i.e., global normalization). The aim of this study was to develop an easily applied, objective, and reproducible method for determining average cerebellar tracer uptake so that images can be scaled specifically to cerebellar activity prior to the performance of SPM analysis. We also investigated whether cerebellar normalization increases the sensitivity and specificity of SPM analysis of ATD patients compared with global normalization.

METHODS

Image files were taken from a parallel study investigating the use of SPECT as a diagnostic tool for early onset of ATD. Two methods for determining cerebellar activity were developed: one manually, using templates, the other automated, using specified coordinates entered into a Matlab routine. Group comparison of ATD patients versus controls (= healthy volunteers and depressed patients) was performed on a voxel-by-voxel basis using SPM 96 on Windows 95. Receiver operator characteristics (ROC) were computed for 20 student raters examining patient and control scans with and without single-subject SPMs.

RESULTS

The reduction of cerebral blood flow in the group of ATD patients appeared 1.7 times greater in spatial extent when the tracer uptake was normalized to cerebellum rather than to average whole brain activity. Computing the reverse contrast (reductions in the control group compared with ATD patients) produced clusters of significance in globally normalized images which were not manifest after normalizing to cerebellum. This is consistent with the notion that the cerebellum is spared in ATD. Analysis of the area under the ROC curve showed that cerebellar-normalized SPM produced significantly improved accuracy over perfusion scans alone.

CONCLUSION

An easily applied, objective, reproducible method was developed for normalizing images to cerebellum prior to the performance of SPM analysis. Cerebellar normalization produced more extensive abnormalities in SPM analyses of ATD patients than global normalization. Furthermore, cerebellar normalization produced marginally more accurate diagnostic results in single-scan SPM analysis of ATD patients than did global normalization.

Normalization of frontal cerebral perfusion in remitted elderly major depression: a 12-month follow-up SPECT study

We examined global and regional cerebral blood flow abnormalities in a group of unmedicated nondemented elderly late-onset unipolar major depressed patients in acute depression and in remission (after a 12-month follow-up period). 35 somatic treatment remitter patients over the age of 60 years and 20 sex-, age-, and vascular risk factor-matched healthy controls were imaged with single photon emission computed tomography, using technetium-99m hexamethylpropylene amine oxime as a tracer. In depression, the depressed group had significantly lower uptake in the left anterior frontal region than the control group. In remission, the left frontal cerebral perfusion abnormalities disappeared, and there were no significant differences in uptake between controls and patients. No significant correlations were found between baseline clinical characteristics of patients and their regional cerebral perfusion at baseline or after a 12-month follow-up. These findings are consistent with the hypothesis that certain neuroanatomic regions of the central nervous system may be functionally and reversibly involved in unipolar major depression, particularly in the late-onset subgroup.

Experimental performance assessment of SPM for SPECT neuroactivation studies using a subresolution sandwich phantom design

The validity domain of voxel-based statistical analysis of SPECT neuroactivation studies with statistical parametric mapping (SPM) has been investigated by a limited number of theoretical and simulation studies. In this work, an experimental setup is described with an assessment of its activation detection performance together with the influence of acquisition and processing parameters. A subresolution sandwich phantom was constructed using a printed high-resolution digital Hoffman phantom with a (99m)TcO(4)-ink mixture. Activations of 8, 16, and 24 mm diameter, with an intensity ranging from 5 to 60%, were constructed in the right frontal cortex, anterior and posterior cingulate, and left striatum. Triple-headed SPECT acquisitions were carried out using both fan-beam and parallel beam geometry. The impact of activation characteristics (size, intensity and location), study size, physical degradation factors, and reconstruction technique were studied using SPM99 in a group comparison design with correction for multiple comparisons. For a 15 x 15 design, all 24-mm activations of 5% intensity were detected for the fan-beam data. Decreased focus or study size, lower SPECT resolution, absence of scatter, and attenuation correction resulted in an increase in minimally detectable activation. For a single study referred to 15 control studies, only 24-mm activation foci with a minimal intensity of 10% were detected in the optimal configuration. This approach allows experimental parameter optimization of SPM-based group or single-subject SPECT activation studies compared to normal data, as used in clinical applications. In principle, these findings can be extended to SPECT receptor studies or PET data.

Brain perfusion SPECT: age- and sex-related effects correlated with voxel-based morphometric findings in healthy adults

PURPOSE

To investigate brain perfusion at single photon emission computed tomography (SPECT) as a function of age and sex in healthy adult volunteers and to correlate perfusion with gray matter concentration determined by using voxel-based morphometry (VBM).

MATERIALS AND METHODS

Eighty-one healthy volunteers underwent both technetium 99m ethylene cysteine dimer SPECT and three-dimensional magnetization preparation rapid acquisition gradient-echo magnetic resonance (MR) imaging. Statistical parametric mapping was used to conduct VBM analysis of the morphologic data, which were compared voxel by voxel with the results of a similar analysis of the perfusion data and more specifically in brain areas showing significant perfusion changes.

RESULTS

VBM data, as compared with perfusion changes, indicated a more symmetric age-related gray matter volume decrease along the Sylvian fissure and in subcortical regions (P < .001). The combination of functional and structural changes indicated a relatively lower functional decrease with aging, as compared with the structural atrophy in the visual, parietal, sensorimotor, and right prefrontal cortices. Significant relative morphologic sex-based differences were found in the cerebellar and temporal cortices, but the comparison did not reveal significant differences between the functional and morphometric data.

CONCLUSION

Age-related perfusion changes are paralleled by similar more symmetric changes in gray matter concentration, which are more prominent than the perfusion changes in some regions. No sex-based differences between perfusion and gray matter concentration were found.

Evaluation of linear registration algorithms for brain SPECT and the errors due to hypoperfusion lesions

The semiquantitative analysis of perfusion single-photon emission computed tomography (SPECT) images requires a reproducible, objective method. Automated spatial standardization (registration) of images is a prerequisite to this goal. A source of registration error is the presence of hypoperfusion defects, which was evaluated in this study with simulated lesions. The brain perfusion images measured by 99mTc-HMPAO SPECT from 21 patients with probable Alzheimer's disease and 35 control subjects were retrospectively analyzed. An automatic segmentation method was developed to remove external activity. Three registration methods, robust least squares, normalized mutual information (NMI), and count difference were implemented and the effects of simulated defects were compared. The tested registration methods required segmentation of the cerebrum from external activity, and the automatic and manual methods differed by a three-dimensional displacement of 1.4+/-1.1 mm. NMI registration proved to be least adversely effected by simulated defects with 3 mm average displacement caused by severe defects. The error in quantifying the patient-template parietal ratio due to misregistration was 2.0% for large defects (70% hypoperfusion) and 0.5% for smaller defects (85% hypoperfusion).

Frontal cerebral perfusion dysfunction in elderly late-onset major depression assessed by 99MTC-HMPAO SPECT

Baseline regional cerebral blood flow of thirty unmedicated late-onset unipolar major depressed patients over the age of 60 years and 20 sex-, age-, and vascular risk factor-matched healthy controls was imaged with single photon emission computed tomography, using technetium-99m hexamethylpropylene amine oxime as a tracer. To avoid errors of diagnosis--in particular, confusion between major depression and organic cognitive impairment--only treatment responders were included in the final sample. Statistically significant differences were observed in both left and right anterior frontal regions, with reduced uptake in depressed patients; these differences were more pronounced in the left hemisphere. Among patients, there was no correlation between regional cerebral blood flow and the severity of baseline symptoms. Our results support the hypothesis that certain neuroanatomic regions of the central nervous system may be functionally involved in elderly unipolar major depression, particularly in the late-onset subgroup.

Perfusion brain SPECT and statistical parametric mapping analysis indicate that apathy is a cingulate syndrome: a study in Alzheimer's disease and nondemented patients

Apathy is the most frequent behavioral symptom in Alzheimer's disease and is also frequently reported in other brain organic disorders occurring in the elderly. Based on the literature, we hypothesized that apathy was related to an anterior cingulate hypofunction. Forty-one subjects were studied. According to ICD 10 diagnostic criteria, 28 patients had Alzheimer dementia (demented: diagnostic group 1), and 13 had organic personality disorders or mild cognitive impairment not attributable to dementia (nondemented: diagnostic group 2). Apathy was evaluated by the Neuro-Psychiatric Inventory. As a result each diagnostic group was divided into two symptomatic subgroups: apathetic or nonapathetic. Brain perfusion was measured by (99m)Tc-labeled bicisate (ECD) brain SPECT and the images were compared using Statistical Parametric Mapping (SPM96). We began by comparing apathetic vs nonapathetic patients, whatever their diagnostic group (whole population), then analyzed them within each group. Twenty-one subjects were apathetic (14 in group 1 and 7 in group 2) and 20 were not (14 in group 1 and 6 in group 2). For the whole population, the Z map showed a significant decrease in ECD uptake for the apathetic patients in the anterior cingulate (P < 0.002) bilaterally. This area was also identified as hypoactive by SPM analysis in the demented (P < 0.035) and in the nondemented (P < 0.02) apathetic patient groups. Finally, conjunction analysis indicated that the anterior cingulate was the common hypoactive structure of the two apathetic subgroups (Z = 4.35, P < 0.0009). These results point to a close relationship between apathy and the anterior cingulate region.

Statistical maps of cerebral blood flow deficits in Alzheimer's disease

Images of cerebral blood flow or metabolism are useful as adjunct to the differential diagnosis of cortical dementia. The aim of this study was to create statistical objective voxel maps of significant differences in regional cerebral blood flow between patients with Alzheimer's disease and age-matched healthy volunteers. Maps of significantly reduced cerebral blood flow were created based on a spatially normalized distribution of cerebral blood flow, measured with O-15-water and positron emission tomography in 16 Alzheimer's patients, compared to 16 healthy age-matched volunteers. After spatial normalization of voxel counts, the t-statistic of the cerebral blood flow deficit was determined from the local voxel-SDs. In the patients, significant reduction (P < 0.05) of the flow distribution was present in regions near the hippocampus, extending rostrally to the temporo-parietal region in both hemispheres, including the medial parietal cortex plus smaller frontal areas. The maximum reduction occurred in the left tapetum/hippocampus (53%, P = 0.061). In conclusion, statistical maps of cerebral blood flow deficits objectively reveal the location of deficits, identifying areas that are difficult to identify by subjective visual inspection of conventional sections of cerebral blood flow maps. This is particularly well illustrated by the pronounced flow reduction of the medial parietal cortices.

Cerebral blood flow and metabolism in late-life depression and dementia

Late-life depression (LLD) is characterized by abnormalities in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) for glucose. Unlike younger adults with major depression, global cortical CBF and CMR reductions have been reported in LLD. Patients with LLD are also characterized by topographic abnormalities, most commonly involving selective prefrontal, superior temporal, and anterior parietal cortex. The fate of these abnormalities with response to antidepressant treatment is highly uncertain, and heterogeneous findings have been reported in younger samples with major depression. The limited data in LLD suggest that response to electroconvulsive therapy or antidepressant medications does not involve reversal of baseline abnormalities but rather accentuation of prefrontal deficits. At minimum, these paradoxical findings suggest that abnormalities in CBF and CMR may be persistent in LLD and a trait characteristic. Characteristic profiles of CBF and CMR abnormalities have also been demonstrated in samples with Alzheimer's disease (AD) and other types of dementia. Functional imaging has shown sensitivity to disease severity and progression. Nonetheless, there is limited information regarding the sensitivity and specificity of the functional imaging modalities in the differential diagnosis of dementias. At present, the evidence does not support the use of functional imaging in isolation as a diagnostic tool. Rather, these imaging modalities may be considered as an adjunct to careful clinical assessment, either to improve diagnosis in early cases or to assist in subtyping difficult cases.

Affective behavioural disturbances in Alzheimer's disease and ischaemic vascular disease

OBJECTIVES

To investigate affective change in Alzheimer's disease and ischaemic vascular disease and examine the contribution of white matter disease to psychopathology in these dementias. Based on earlier studies, it was predicted that: (1) depression would be more prevalent and severe in ischaemic vascular disease; (2) psychomotor slowing would be more prevalent in ischaemic vascular disease; (3) apathy would be more prevalent in ischaemic vascular disease; and (4) The degree of white matter disease would be positively correlated with the severity of psychomotor slowing.

METHODS

Ratings of affective/behavioural states and white matter disease were compared in 256 patients with Alzheimer's disease and 36 patients with ischaemic vascular disease or mixed dementia with an ischaemic vascular component using analysis of variance (ANOVA) and linear regression models.

RESULTS

The findings were: (1) decreased affect/withdrawal was more prevalent and severe in patients with ischaemic vascular disease and patients with white matter disease; (2) psychomotor slowing was more severe in patients with ischaemic vascular disease and patients with white matter disease; and (3) differences between Alzheimer's disease and ischaemic vascular dementia groups in the degree of psychomotor slowing were independent of the severity of white matter disease.

CONCLUSIONS

Future studies using structural and functional neuroimaging techniques would be helpful for examining the relation between neurobiological factors and affective/behavioural disturbances in dementia.

A unifying hypothesis of Alzheimer's disease. III. Risk factors

Normal ageing and Alzheimer's disease (AD) have many features in common and, in many respects, both conditions only differ by quantitative criteria. A variety of genetic, medical and environmental factors modulate the ageing-related processes leading the brain into the devastation of AD. In accordance with the concept that AD is a metabolic disease, these risk factors deteriorate the homeostasis of the Ca(2+)-energy-redox triangle and disrupt the cerebral reserve capacity under metabolic stress. The major genetic risk factors (APP and presenilin mutations, Down's syndrome, apolipoprotein E4) are associated with a compromise of the homeostatic triangle. The pathophysiological processes leading to this vulnerability remain elusive at present, while mitochondrial mutations can be plausibly integrated into the metabolic scenario. The metabolic leitmotif is particularly evident with medical risk factors which are associated with an impaired cerebral perfusion, such as cerebrovascular diseases including stroke, cardiovascular diseases, hypo- and hypertension. Traumatic brain injury represents another example due to the persistent metabolic stress following the acute event. Thyroid diseases have detrimental sequela for cerebral metabolism as well. Furthermore, major depression and presumably chronic stress endanger susceptible brain areas mediated by a host of hormonal imbalances, particularly the HPA-axis dysregulation. Sociocultural and lifestyle factors like education, physical activity, diet and smoking may also modulate the individual risk affecting both reserve capacity and vulnerability. The pathophysiological relevance of trace metals, including aluminum and iron, is highly controversial; at any rate, they may adversely affect cellular defences, antioxidant competence in particular. The relative contribution of these factors, however, is as individual as the pattern of the factors. In familial AD, the genetic factors clearly drive the sequence of events. A strong interaction of fat metabolism and apoE polymorphism is suggested by intercultural epidemiological findings. In cultures, less plagued by the 'blessings' of the 'cafeteria diet-sedentary' Western lifestyle, apoE4 appears to be not a risk factor for AD. This intriguing evidence suggests that, analogous to cardiovascular diseases, apoE4 requires a hyperlipidaemic lifestyle to manifest as AD risk factor. Overall, the etiology of AD is a key paradigm for a gene-environment interaction. Copyright 2000 John Wiley & Sons, Ltd.

Validation of statistical parametric mapping (SPM) in assessing cerebral lesions: A simulation study

Simulated abnormalities were introduced in a normal SPECT with known and controllable characteristics (abnormality size and depth) in an attempt to provide validation for the analysis of SPECT lesion studies using SPM. Two simulations were carried out. The first determined the minimum hypoperfusion depth detectable using SPM by altering mean local intensity while keeping the size of the lesion constant. This was done by changing the mean local intensity in percentile increments of 10 down to -100 and up to 50. The second simulation determined the cluster size that SPM can detect by keeping the mean intensity of the lesion constant while altering its size from 4 voxels to 63,000 voxels in a total brain volume of 300, 000 voxels. Both simulations determined which method of normalization is most appropriate, what level of grey matter thresholding should be used, and at what statistical probability peak threshold (u) the results should be determined. Proportional scaling was found to be the most appropriate normalization method. ANCOVA was useful where very large abnormalities were present and normalization external to SPM was not available. In those cases, ANCOVA was used in conjunction with measurement of an unaffected part of the brain (in this case medial occipital lobe). For better results statistical probability peak threshold was set to p(u) = 0. 01 and grey matter threshold was set to a value below 0.5. SPM produced best results when the abnormality represented a decrease of about -50% from the normal or more and detected other decreases in an acceptable manner.

Follow-up study of depression in the elderly. Clinical and SPECT data

BACKGROUND

Imaging studies in depression of the elderly are often small and highly selective.

AIMS

To investigate a large group of elderly depressed patients in order to assess changes in clinical, imaging and neuropsychological variables at follow-up.

METHOD

Patients (n = 175, age range 65-91 years) with clinical depression were identified from consecutive local referrals. Clinical interviews, neuropsychological tests and SPECT scans were carried out at referral and at two-year follow-up.

RESULTS

Of 84 re-examined patients, 46.5% were well, 9.5% were ill, 33% partially recovered and 11% had developed dementia. Duration of illness before index assessment was the only factor to predict outcome. Thirty-nine patients could be scanned and followed up. There were no differences between patients with good or poor depressive outcome on SPECT. Ten clinically improved patients could be re-examined with SPECT. There were relative increases in right cingulate gyrus and right cerebellum at follow-up.

CONCLUSIONS

The patients group was comparable with other studies showing high levels of residual depressive symptoms. Activity changes in limbic cortex are implicated in depression of old age.

Cortical grey matter reductions associated with treatment-resistant chronic unipolar depression. Controlled magnetic resonance imaging study

BACKGROUND

The aetiology of treatment-resistant major depression is little understood; its apparent intractability may reflect brain abnormality.

METHOD

Magnetic resonance images of the brains of 20 subjects with major depression lasting for two years or more were compared with 20 healthy control subjects and 20 other subjects who had completely recovered from depression. Subjects were individually matched for age, gender, years of education and premorbid IQ. Grey matter was segmented from the images, and compared between groups on a voxel-by-voxel basis.

RESULTS

Subjects with chronic depression showed reduced grey matter density in the left temporal cortex including the hippocampus. There was also a trend for reduction in the right hippocampus. Left hippocampal grey matter density was correlated with measures of verbal memory, supporting the functional significance of the observed magnetic resonance imaging changes.

CONCLUSIONS

Our results potentially challenge the accepted view of depression as a functional and fully reversible illness, implying instead that more permanent brain changes may be associated with chronicity. Confirmatory longitudinal and prospective studies are required to determine whether these differences pre-date the onset of depression or are the result of the chronic illness process or its treatment.