Does executive impairment define a frontal variant of Alzheimer's disease?

Behavioral and dysexecutive variant of Alzheimer's disease: Insights from structural and molecular imaging studies

Frontal variant Alzheimer's disease (AD) manifests with either behavioral or dysexecutive syndromes. Recent efforts to gain a deeper understanding of this phenotype have led to a re-conceptualization of frontal AD. Behavioral (bAD) and dysexecutive (dAD) phenotypes could be considered subtypes, as suggested by both clinical and neuroimaging studies. In this review, we focused on imaging studies to highlight specific brain patterns in these two uncommon clinical AD phenotypes. Although studies did not compare directly these two variants, a common epicenter located in the frontal cortex could be inferred. On the contrary, 18F-FDG-PET findings suggested differing metabolic patterns, with bAD showing specific involvement of frontal regions and dAD exhibiting widespread alterations. Structural MRI findings confirmed this pattern, suggesting that degeneration might involve neural circuits associated with behavioral control in bAD and attentional networks in dAD. Furthermore, molecular imaging has identified different neocortical tau distribution in bAD and dAD patients compared to typical AD patients, although the distribution is remarkably heterogeneous. In contrast, Aβ deposition patterns are less differentiated between these atypical variants and typical AD. Although preliminary, these findings underscore the complexity of AD frontal phenotypes and suggest that they represent distinct entities. Further research is essential to refine our understanding of the pathophysiological mechanisms in frontal AD.

A systematic review of atypical Alzheimer's disease including behavioural and psychological symptoms

Alzheimer's disease (AD) is the commonest cause of dementia, characterized by the clinical presentation of progressive anterograde episodic memory impairment. However, atypical presentation of patients is increasingly recognized. These atypical AD include logopenic aphasia, behavioural variant AD, posterior cortical atrophy, and corticobasal syndrome. These atypical AD are more common in patients with young onset AD before the age of 65 years old. Since medical needs (including the behavioural and psychological symptoms of dementia) of atypical AD patients could be different from typical AD patients, it is important for clinicians to be aware of these atypical forms of AD. In addition, disease modifying treatment may be available in the future. This review aims at providing an update on various important subtypes of atypical AD including behavioural and psychological symptoms.

New insights into atypical Alzheimer's disease in the era of biomarkers

Most patients with Alzheimer's disease present with amnestic problems; however, a substantial proportion, over-represented in young-onset cases, have atypical phenotypes including predominant visual, language, executive, behavioural, or motor dysfunction. In the past, these individuals often received a late diagnosis; however, availability of CSF and PET biomarkers of Alzheimer's disease pathologies and incorporation of atypical forms of Alzheimer's disease into new diagnostic criteria increasingly allows them to be more confidently diagnosed early in their illness. This early diagnosis in turn allows patients to be offered tailored information, appropriate care and support, and individualised treatment plans. These advances will provide improved access to clinical trials, which often exclude atypical phenotypes. Research into atypical Alzheimer's disease has revealed previously unrecognised neuropathological heterogeneity across the Alzheimer's disease spectrum. Neuroimaging, genetic, biomarker, and basic science studies are providing key insights into the factors that might drive selective vulnerability of differing brain networks, with potential mechanistic implications for understanding typical late-onset Alzheimer's disease.

Frontal Variant of Alzheimer Disease Differentiated From Frontotemporal Dementia Using in Vivo Amyloid and Tau Imaging

The frontal variant of Alzheimer disease (fvAD) is characterized by behavioral and/or dysexecutive impairments that can resemble those of behavioral-variant frontotemporal dementia (bvFTD). This overlap, in addition to the lack of consensus clinical criteria for fvAD, complicates its identification. We provide the first case report of fvAD differentiated in vivo from bvFTD using amyloid-beta and tau PET imaging. The patient, a right-handed woman, presented with forgetfulness at age 60. Cognitive testing at that time revealed mild impairments in memory, attention, and executive functions. Three years later, her family reported that she was displaying socially inappropriate behaviors, inertia, diminished social interest, and altered food preferences-the sum of which met the criteria for possible bvFTD. PET using an amyloid-beta tracer (F-AZD4694) identified diffuse amyloid plaques across the cerebral cortex. PET using a tau tracer specific for neurofibrillary tangles (F-MK6240) identified substantial tau pathology in the brain's frontal lobes. Together with the clinical findings, these images supported the diagnosis of fvAD rather than bvFTD. Considering past and emerging evidence that tau topography in Alzheimer disease (AD) matches the clinical features of AD, we discuss the potential utility of in vivo tau imaging using F-MK6240 for identifying fvAD.

An Initial Empirical Operationalization of the Earliest Stages of the Alzheimer's Continuum

PURPOSE

The Alzheimer's Continuum (AC) includes 2 preclinical stages defined by subjective cognitive complaints, transitional cognitive declines, and neurobehavioral symptoms. Operationalization of these stages is necessary for them to be applied in research.

METHODS

Cognitively normal individuals with known amyloid biomarker status were selected from the National Alzheimer's Coordinating Center Uniform Data Set. Participants and their caregivers provided information on subjective cognitive complaints, neurobehavioral features, and objective cognitive functioning.

PATIENTS

The sample included 101 amyloid positive (A+) and 447 amyloid negative (A-) individuals.

RESULTS

Rates of subjective cognitive complaints (A+: 34.90%, A-: 29.90%) and neurobehavioral symptoms (A+: 22.40%, A-: 22.40%) did not significantly differ between A+/- individuals. However, the frequency of transitional cognitive decline was significantly higher among A+ (38.00%) than A- participants (24.90%). We explored various empirical definitions for defining the early stages of the AC among A+ participants. Rates of classification into AC stage 1 versus AC stage 2 varied depending on the number of symptoms required: 57.40% versus 42.60% (1 symptom), 28.70% versus 71.30% (2 symptoms), and 6.90% versus 93.10% (all 3 symptoms).

CONCLUSION

The presence of 2 of the proposed symptom classes to separate AC stage 2 from stage 1 seems to provide a good empirical balance.

Quantitative and qualitative features of executive dysfunction in frontotemporal and Alzheimer's dementia

Behavioral variant fronto-temporal degeneration (bvFTD) is typically distinguished from Alzheimer's disease (AD) by early, prominent dysexecutive findings, in addition to other clinical features. However, differences in executive functioning between these groups are not consistently found. The current study sought to investigate quantitative and qualitative differences in executive functioning between those with bvFTD and AD in a large sample, while controlling for dementia severity and demographic variables. Secondary data analyses were completed on a subset of cases from the National Alzheimer's Coordinating Center collected from 36 Alzheimer's Disease Research Centers and consisting of 1,577 individuals with AD and 406 individuals with bvFTD. Groups were compared on 1) ability to complete three commonly administered executive tasks (letter fluency, Trail Making Test Part B [TMTB], and digits backward); 2) quantitative test performance; and 3) errors on these tasks. Findings suggested that individuals with bvFTD were less likely to complete letter fluency, χ²(2) = 178.62, p < .001, and number span tasks, χ²(1) = 11.49, p < .001), whereas individuals with AD were less likely to complete TMTB, χ²(2) = 460.38, p < .001. Individuals with bvFTD performed more poorly on letter fluency, F(1) = 28.06, p = .013, but there were not group differences in TMTB lines per second or number span backwards. Errors generally did not differentiate the diagnostic groups. In summary, there is substantial overlap in executive dysfunction between those with bvFTD and AD, though individuals with bvFTD tend to demonstrate worse letter fluency performance.

Independent effects of white matter hyperintensities on cognitive, neuropsychiatric, and functional decline: a longitudinal investigation using the National Alzheimer's Coordinating Center Uniform Data Set

BACKGROUND

Longitudinal investigations are needed to improve understanding of the contributions of cerebral small vessel disease to the clinical manifestation of Alzheimer's disease, particularly in the early disease stages. This study leveraged the National Alzheimer's Coordinating Center Uniform Data Set to longitudinally examine the association between white matter hyperintensities and neuropsychological, neuropsychiatric, and functional decline among participants with normal cognition.

METHODS

The sample included 465 participants from the National Alzheimer's Coordinating Center Uniform Data Set who had quantitated volume of white matter hyperintensities from fluid-attenuated inversion recovery MRI, had normal cognition at the time of their MRI, and were administered the National Alzheimer's Coordinating Center Uniform Data Set neuropsychological test battery within 1 year of study evaluation and had at least two post-MRI time points of clinical data. Neuropsychiatric status was assessed by the Geriatric Depression Scale-15 and Neuropsychiatric Inventory-Questionnaire. Clinical Dementia Rating Sum of Boxes defined functional status. For participants subsequently diagnosed with mild cognitive impairment (MCI) or dementia, their impairment must have been attributed to Alzheimer's disease (AD) to evaluate the relationships between WMH and the clinical presentation of AD.

RESULTS

Of the 465 participants, 56 converted to MCI or AD dementia (average follow-up = 5 years). Among the 465 participants, generalized estimating equations controlling for age, sex, race, education, APOE ε4, and total brain and hippocampal volume showed that higher baseline log-white matter hyperintensities predicted accelerated decline on the following neuropsychological tests in rank order of effect size: Trails B (p < 0.01), Digit Symbol Coding (p < 0.01), Logical Memory Immediate Recall (p = 0.02), Trail Making A (p < 0.01), and Semantic Fluency (p < 0.01). White matter hyperintensities predicted increases in Clinical Dementia Rating Sum of Boxes (p < 0.01) and Geriatric Depression Scale-15 scores (p = 0.01). Effect sizes were comparable to total brain and hippocampal volume. White matter hyperintensities did not predict diagnostic conversion. All effects also remained after including individuals with non-AD suspected etiologies for those who converted to MCI or dementia.

CONCLUSIONS

In this baseline cognitively normal sample, greater white matter hyperintensities were associated with accelerated cognitive, neuropsychiatric, and functional decline independent of traditional risk factors and MRI biomarkers for Alzheimer's disease.

Frontal variant of Alzheimer's disease masquerading as behavioural-variant frontotemporal dementia: a case study comparison

The current clinical diagnostic criteria for Alzheimer's disease (AD) recognize an atypical, non-amnestic presentation of AD, characterized by prominent executive dysfunction. Increasing evidence, however, indicates that the clinical phenotype of this so-called "frontal-variant" of AD (fv-AD) includes behavioral symptoms and deficits in social cognition, together with disproportionate frontal lobe atrophy. As these features resemble those characteristic of behavioral-variant frontotemporal dementia (bvFTD), differential diagnosis can be challenging. Here, we report a case of fv-AD who met clinical diagnostic criteria bvFTD, but had in vivo amyloid neuroimaging evidence of AD pathology. We compare this case against two individuals who were clinically diagnosed with bvFTD and early-onset AD, with in vivo amyloid neuroimaging confirmation of pathology. We highlight the challenges in differential diagnosis by contrasting their behavioral, cognitive and structural neuroimaging findings.

Measuring executive dysfunction in Parkinson's disease: Reliability and validity of the Spanish version of Frontal Assessment Battery (FAB-E)

Background

Deficits in executive functions (EFs) are frequently detected in patients with Parkinson’s disease (PD). The Frontal Assessment Battery (FAB) is a screening test for assessing EFs although it has not been so far adapted and validated in Spain. We evaluated the reliability and validity of the Spanish version of the FAB (FAB-E) in PD patients.

Materials and methods

Our study included 54 healthy subjects and 67 PD patients. Cognitive assessment of participants was conducted using the FAB-E, Mini-Mental State Examination (MMSE), Trail Making Test (TMT), Revised-Barcelona Test (RBT) and Executive Interview (EXIT-25). Internal consistency, intra- and test-retest reliabilities, concurrent and discriminant validity of the FAB-E were examined. To evaluate the influence of cognitive dysfunction in PD on the performance of the FAB-E, we also classified the PD patients into groups according to their cognitive status as measured by the MMSE using published criteria to identify cognitive deficits in PD.

Results

The FAB-E showed good internal consistency (α = 0.751). The intraclass correlation coefficients (ranging from 0.559 to 0.891) and Spearman correlations (from 0.494 to 0.864) of the FAB-E subtests indicated a good-strong reliability. The total and subtest scores generally showed a good concurrent validity, except for the prehension behaviour item of the FAB-E and the Interference and Go/no-go tasks of the EXIT-25 that presented low estimates. Excluding the prehension behaviour subtest, the performance of the FAB-E was higher in the control group than in PD patients. Cognitive dysfunction in PD patients also indicated significant poorer FAB-E scores excepting the motor and prehension behaviour subtests. Discriminant analysis determined a cut-off of 14.5 was optimal to differentiate healthy subjects from PD patients. Moreover, a cut-off <12.5 allocated satisfactorily those PD patients with cognitive impairment (MMSE<26) and scores <11.5 classified suitably those PD patients with dementia (MMSE<24).

Conclusion

The FAB-E is an accurate tool for evaluating EFs in patients with PD and can provide useful information for distinguishing PD patients with and without cognitive dysfunction at a bedside assessment.

The frontal assessment battery in clinical practice: a systematic review

BACKGROUND

The frontal assessment battery (FAB) is a brief tool designed to evaluate executive function. Some studies have particularly focused on assessing its applicability addressing two issues: first, on detecting the brain regions responsible for the FAB performance, and second, on determining its capability for differential diagnosis. Our aim was to summarize and analyze critically the studies that assessed the neuroanatomical correspondence and the differential diagnostic value of the FAB in several study populations suffering from different pathologies.

METHODS

We completed a literature search in MEDLINE (via PubMed) database by using the term "frontal assessment battery" and the combination of this term with "applicability" or "use" or "usefulness". The search was limited to articles in English or Spanish languages, published between 1 September 2000 and 30 September 2016, human studies, and journal articles.

RESULTS

A total of 32 studies met inclusion criteria. Seventeen studies were aimed at identifying the brain regions or the neural substrates involved in executive functions measured by the FAB and 15 studies at verifying that the FAB was an appropriate tool for the differential diagnosis in neurological diseases.

CONCLUSION

Our study showed that the FAB may be an adequate assessment tool for executive function and may provide useful information for differential diagnosis in several diseases. Given that the FAB takes short time and is easy to administer, its usage may be of great interest as part of a full neuropsychological assessment in clinical settings. Copyright © 2017 John Wiley & Sons, Ltd.

Comparison of Prefrontal Atrophy and Episodic Memory Performance in Dysexecutive Alzheimer's Disease and Behavioral-Variant Frontotemporal Dementia

Alzheimer's disease (AD) sometimes presents with prominent executive dysfunction and associated prefrontal cortex atrophy. The impact of such executive deficits on episodic memory performance as well as their neural correlates in AD, however, remains unclear. The aim of the current study was to investigate episodic memory and brain atrophy in AD patients with relatively spared executive functioning (SEF-AD; n = 12) and AD patients with relatively impaired executive functioning (IEF-AD; n = 23). We also compared the AD subgroups with a group of behavioral-variant frontotemporal dementia patients (bvFTD; n = 22), who typically exhibit significant executive deficits, and age-matched healthy controls (n = 38). On cognitive testing, the three patient groups showed comparable memory profiles on standard episodic memory tests, with significant impairment relative to controls. Voxel-based morphometry analyses revealed extensive prefrontal and medial temporal lobe atrophy in IEF-AD and bvFTD, whereas this was limited to the middle frontal gyrus and hippocampus in SEF-AD. Moreover, the additional prefrontal atrophy in IEF-AD and bvFTD correlated with memory performance, whereas this was not the case for SEF-AD. These findings indicate that IEF-AD patients show prefrontal atrophy in regions similar to bvFTD, and suggest that this contributes to episodic memory performance. This has implications for the differential diagnosis of bvFTD and subtypes of AD.

Brain metabolism and cerebrospinal fluid biomarkers profile of non-amnestic mild cognitive impairment in comparison to amnestic mild cognitive impairment and normal older subjects

INTRODUCTION

Mild cognitive impairment (MCI) is classically considered a transitional stage between normal aging and dementia. Non-amnestic MCI (naMCI) patients, however, typically demonstrate cognitive deficits other than memory decline. Furthermore, as a group, naMCI have a lower rate of an eventual dementia diagnosis as compared to amnestic subtypes of MCI (aMCI). Unfortunately, studies investigating biomarker profiles of naMCI are scarce. The study objective was to investigate the regional brain glucose metabolism (rBGM) with [18F]FDG-PET and cerebrospinal fluid (CSF) biomarkers in subjects with naMCI as compared to a control group (CG) and aMCI subjects.

METHODS

Ninety-five patients were included in three different groups: naMCI (N = 32), aMCI (N = 33) and CG (N = 30). Patients underwent brain MRI and [18F]FDG-PET. A subsample (naMCI = 26, aMCI = 28) also had an assessment of amyloid-β, tau, and phosphorylated tau levels in the CSF.

RESULTS

Both MCI groups had lower rBGM in relation to the CG in the precuneus. Subjects with naMCI showed decreased right prefrontal metabolism as well as higher levels of CSF amyloid-β relative to aMCI subjects.

CONCLUSION

While amnestic MCI subjects showed a biomarker profile classically related to MCI due to Alzheimer's disease, naMCI patients illustrated a decrease in both prefrontal hypometabolism and higher CSF amyloid-β levels relative to the aMCI group. These biomarker findings indicate that naMCI is probably a heterogeneous group with similar precuneus hypometabolism compared to aMCI, but additional frontal hypometabolism and less amyloid-β deposition in the brain. Clinical follow-up and reappraisal of biomarkers of the naMCI group is needed to determine the outcome and probable etiological diagnosis.

Advancing research diagnostic criteria for Alzheimer's disease: the IWG-2 criteria

In the past 8 years, both the International Working Group (IWG) and the US National Institute on Aging-Alzheimer's Association have contributed criteria for the diagnosis of Alzheimer's disease (AD) that better define clinical phenotypes and integrate biomarkers into the diagnostic process, covering the full staging of the disease. This Position Paper considers the strengths and limitations of the IWG research diagnostic criteria and proposes advances to improve the diagnostic framework. On the basis of these refinements, the diagnosis of AD can be simplified, requiring the presence of an appropriate clinical AD phenotype (typical or atypical) and a pathophysiological biomarker consistent with the presence of Alzheimer's pathology. We propose that downstream topographical biomarkers of the disease, such as volumetric MRI and fluorodeoxyglucose PET, might better serve in the measurement and monitoring of the course of disease. This paper also elaborates on the specific diagnostic criteria for atypical forms of AD, for mixed AD, and for the preclinical states of AD.

Fluid biomarkers for diagnosing dementia: rationale and the Canadian Consensus on Diagnosis and Treatment of Dementia recommendations for Canadian physicians

Fluid biomarkers improve the diagnostic accuracy in dementia and provide an objective measure potentially useful as a therapeutic response in clinical trials. The role of fluid biomarkers in patient care is a rapidly evolving field. Here, we provide a review and recommendations regarding the use of fluid biomarkers in clinical practice as discussed at the Fourth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia (CCCDTD4) convened in Montreal, 4 to 5 May 2012. At present, there is no consensus regarding the optimal methodology for conducting quantification of plasma amyloid-beta (Aβ) peptides. In addition, since there is insufficient evidence supporting clinical applications for plasma Aβ-peptide measures, the CCCDTD4 does not recommended plasma biomarkers either for primary care or for specialists. Evidence for CSF Aβ1-42, total tau and phosphorylated tau in the diagnosis of Alzheimer pathology is much stronger, and can be considered at the tertiary care level for selected cases to improve diagnostic certainty, particularly in those cases presenting atypical clinical features.

Trail making test B and brain perfusion imaging in mild cognitive impairment and mild Alzheimer's disease

The trail making test (TMT) has long been used to investigate deficits in cognitive processing speed and executive function in humans. However, there are few studies that elucidate the neural substrates of the TMT. The aim of the present study was to identify the brain regional perfusion patterns associated with performance on TMT part B (TMT-B) in patients with amnestic mild cognitive impairment (aMCI) or mild Alzheimer's disease (AD). Twenty-one patients with good TMT-B scores and 21 age- and sex-matched patients with poor TMT-B scores were selected. All 42 subjects underwent brain single photon emission computed tomography (SPECT), and the SPECT images were analyzed by statistical parametric mapping. No significant differences between good- and poor-scoring groups were found with respect to years of education, Addenbrooke's Cognitive Examination scores, and scores on TMT-A. Compared to patients with good scores on TMT-B, patients with poor scores showed significant hypoperfusion in the bilateral anterior cingulate extending to the posterior region on the right side, bilateral caudate nucleus and putamen, and bilateral thalamus. Analysis of 63 AD or aMCI subjects revealed significant correlation a between regional cerebral blood flow in the right cingulate cortex and TMT-B scores. Our results suggest that functional activity of the anterior cingulate, striatum and thalamus is closely related to performance time on TMT-B. The performance time on the TMT-B score might be a promising index of dysfunction of the anterior cingulate, striatum, and thalamus among patients with aMCI or mild AD.

Clinical, imaging, and pathological heterogeneity of the Alzheimer's disease syndrome

With increasing knowledge of clinical in vivo biomarkers and the pathological intricacies of Alzheimer's disease (AD), nosology is evolving. Harmonized consensus criteria that emphasize prototypic illness continue to develop to achieve diagnostic clarity for treatment decisions and clinical trials. However, it is clear that AD is clinically heterogeneous in presentation and progression, demonstrating variable topographic distributions of atrophy and hypometabolism/hypoperfusion. AD furthermore often keeps company with other conditions that may further nuance clinical expression, such as synucleinopathy exacerbating executive and visuospatial dysfunction and vascular pathologies (particularly small vessel disease that is increasingly ubiquitous with human aging) accentuating frontal-dysexecutive symptomatology. That some of these atypical clinical patterns recur may imply the existence of distinct AD variants. For example, focal temporal lobe dysfunction is associated with a pure amnestic syndrome, very slow decline, with atrophy and neurofibrillary tangles limited largely to the medial temporal region including the entorhinal cortex. Left parietal atrophy and/or hypometabolism/hypoperfusion are associated with language symptoms, younger age of onset, and faster rate of decline - a potential 'language variant' of AD. Conversely, the same pattern but predominantly affecting the right parietal lobe is associated with a similar syndrome but with visuospatial symptoms replacing impaired language function. Finally, the extremely rare frontal variant is associated with executive dysfunction out of keeping with degree of memory decline and may have prominent behavioural symptoms. Genotypic differences may underlie some of these subtypes; for example, absence of apolipoprotein E e4 is often associated with atypicality in younger onset AD. Understanding the mechanisms behind this variability merits further investigation, informed by recent advances in imaging techniques, biomarker assays, and quantitative pathological methods, in conjunction with standardized clinical, functional, neuropsychological and neurobehavioral evaluations. Such an understanding is needed to facilitate 'personalized AD medicine', and eventually allow for clinical trials targeting specific AD subtypes. Although the focus legitimately remains on prototypic illness, continuing efforts to develop disease-modifying therapies should not exclude the rarer AD subtypes and common comorbid presentations, as is currently often the case. Only by treating them as well can we address the full burden of this devastating dementia syndrome.

Executive function and activities of daily living in Alzheimer's disease: a correlational meta-analysis

BACKGROUND

The assessment of executive function (EF) and activities of daily living (ADL) are important elements in the diagnosis of Alzheimer's disease.

METHODS

Following a comprehensive search in three databases, a random-effects meta-analysis was used to investigate the association between ADL ability and seventeen tests of EF, three tests of attention and working memory and the Mini-Mental State Examination. The association between EF and ADL ability was further investigated in relation to four different methods of assessing ADL, and one specific ADL, driving.

RESULTS

Forty-nine studies met the inclusion criteria, and a total of 3,663 participants were included, the majority of whom were diagnosed with Alzheimer's disease. Most of the individual tests, including commonly used tests of EF such as the Clock Drawing Test, Letter Fluency and the Trail Making Test Part B, showed a significant moderate association with ADL. Associations between EF and ADL ability were similar for all four methods of assessing ADL ability. Driving ability was also moderately associated with EF.

CONCLUSION

The meta-analysis suggests a consistent moderate association between ADL and EF, supporting the growing evidence for a link between ADL and executive dysfunction in early dementia.

Frontal assessment battery and brain perfusion imaging in Alzheimer's disease

BACKGROUND

The frontal assessment battery (FAB) is reported to be a useful tool for assessing frontal dysfunction. However, the neural substrates involved in patients with Alzheimer's disease (AD) remain to be elucidated. The aim of the present study was to identify the regional perfusion patterns of the brain associated with performance scores on the FAB of patients with AD using brain perfusion assessed by single photon emission computed tomography (SPECT).

METHODS

Twenty-four AD patients with high scores and 24 age- and sex-matched AD patients with low scores on the FAB were selected from 470 consecutive Japanese patients of the Memory Clinic of Okayama University Hospital. All 48 participants underwent brain SPECT with 99mTc-ethylcysteinate dimer, and the SPECT images were analyzed by statistical parametric mapping.

RESULTS

No significant differences were found between high and low FAB scoring groups with respect to Addenbrooke's Cognitive Examination scores, Mini-Mental State Examination scores, or the depression score of the Neuropsychiatric Inventory subscale. Compared with patients with high scores on the FAB, AD patients with low scores showed significant hypoperfusion in the left middle frontal gyrus (MFG) and the right superior frontal gyrus (SFG) extending to the left SFG.

CONCLUSION

Our results suggest that functional activity of the SFG and MFG is closely related to the FAB score. The FAB might be a promising strategy to detect early stages of AD with low SFG and MFG function.

Cerebral correlates of psychotic syndromes in neurodegenerative diseases

Psychosis has been recognized as a common feature in neurodegenerative diseases and a core feature of dementia that worsens most clinical courses. It includes hallucinations, delusions including paranoia, aggressive behaviour, apathy and other psychotic phenomena that occur in a wide range of degenerative disorders including Alzheimer's disease, synucleinopathies (Parkinson's disease, dementia with Lewy bodies), Huntington's disease, frontotemporal degenerations, motoneuron and prion diseases. Many of these psychiatric manifestations may be early expressions of cognitive impairment, but often there is a dissociation between psychotic/behavioural symptoms and the rather linear decline in cognitive function, suggesting independent pathophysiological mechanisms. Strictly neuropathological explanations are likely to be insufficient to explain them, and a large group of heterogeneous factors (environmental, neurochemical changes, genetic factors, etc.) may influence their pathogenesis. Clinico-pathological evaluation of behavioural and psychotic symptoms (PS) in the setting of neurodegenerative and dementing disorders presents a significant challenge for modern neurosciences. Recognition and understanding of these manifestations may lead to the development of more effective preventive and therapeutic options that can serve to delay long-term progression of these devastating disorders and improve the patients' quality of life. A better understanding of the pathophysiology and distinctive pathological features underlying the development of PS in neurodegenerative diseases may provide important insights into psychotic processes in general.

Perseverative errors on the Wisconsin Card Sorting Test and brain perfusion imaging in mild Alzheimer's disease

BACKGROUND

The Wisconsin Card Sorting Test (WCST) has long been used to investigate deficits in executive function in humans. The majority of studies investigating deficient WCST performance focused on the number of categories achieved (CA) and the number of perseverative errors of the Nelson type (PEN). However, there is insufficient evidence that these two measures reflect the same neural deficits.

METHODS

Twenty AD patients with high PEN scores, and 20 age- and sex-matched AD patients with low PEN scores were selected. All 40 subjects underwent brain SPECT, and the SPECT images were analyzed by Statistical Parametric Mapping.

RESULTS

No significant differences were found between high and low PEN score groups with respect to years of education, Addenbrooke's Cognitive Examination scores, and Mini-Mental State Examination scores. However, higher z scores for hypoperfusion in the bilateral rectal and orbital gyri were observed in the high PEN score group compared with the low PEN score group.

CONCLUSIONS

Our results suggest that functional activity of the bilateral rectal and orbital gyri is closely related to PEN scores on a modified WCST (mWCST). The PEN score on a mWCST might be a promising index of dysfunction of the orbitofrontal area among patients with mild AD.

Clinicopathological correlates of behavioral and psychological symptoms of dementia

Behavioral and psychological symptoms are commonly observed in a majority of demented patients at some time during the course of their illness. Many of these psychiatric manifestations, especially those related to mood, may be early expressions of dementia and/or mild cognitive impairment. The literature suggests that behavioral and psychological symptoms of dementia (BPSD) are an integral part of the disease process. The dissociation, in many cases, between BPSD and the rather linear decline in cognitive functions suggests that independent pathophysiological mechanisms give rise to these symptoms. A review of the neuroimaging and neuropathology literature indicates that BPSD are the expression of regional rather than diffuse brain pathology. Psychotic symptoms in demented patients usually demonstrate preferential involvement of the frontal lobe and/or limbic regions. Visual hallucinations differentiate themselves from other psychotic symptoms by their tendency to involve the occipital lobes. There is a significant association between apathy and structural changes of the anterior cingulate gyrus. White matter hyperintensities occur in a significant number of depressed patients; otherwise, there is lack of association between depression and either specific brain changes or affected regions. Strictly neuropathological explanations are likely to be insufficient to explain BPSD. Environmental changes, neurochemical abnormalities, past psychiatric history (including premorbid personality), social history (e.g., intellectual achievement and life-long learning), family history, and genetic susceptibility are factors, among others, that influence BPSD.