Variability in cognitive presentation of Alzheimer's disease

Cerebrospinal fluid biomarkers in clinical subtypes of early-onset Alzheimer's disease

BACKGROUND/AIMS

Accurate diagnosis of sporadic early-onset Alzheimer's disease (EOAD) can be challenging, and cerebrospinal fluid (CSF) biomarkers may assist in this process. We compared CSF indices between three EOAD subtypes: amnestic, logopenic progressive aphasia (LPA), and posterior cortical atrophy (PCA).

METHODS

We identified 21 amnestic EOAD, 20 LPA, and 12 PCA patients with CSF data, which included amyloid β1-42 (Aβ42), total tau (t-tau), phospho-tau181 (p-tau), and Aβ42/t-tau index (ATI) levels.

RESULTS

Aβ42 and ATI levels were similar across groups, but t-tau and p-tau levels were significantly lower in PCA patients.

CONCLUSIONS

The Aβ42 and ATI data confirm the commonality of the Aβ pathology in EOAD. The lower tau indices in PCA patients may reflect differences in the distribution of neurofibrillary tangles or rates of neurodegeneration.

Distinct cognitive phenotypes in Alzheimer's disease in older people

BACKGROUND

Alzheimer's disease (AD) is considered to be a disorder predominantly affecting memory. It is increasingly recognized that the cognitive profile may be heterogeneous. We hypothesized that it would be possible to define distinct “cognitive phenotypes” in older people with AD.

METHODS

Participants from three individual studies were included, consisting of 109 patients with a diagnosis of probable AD, and 91 age- and gender-matched control participants. All had demographic and cognitive assessment data available, including the Cambridge Cognitive Examination of the Elderly (CAMCOG). The CAMCOG scores and sub-scores were further analyzed using hierarchical cluster analysis and factor analysis.

RESULTS

Three clusters were identified. The scores loaded onto three factors representing the domains of attention, praxis, calculation, and perception; memory; and language comprehension and executive function. The main difference between the clusters related to degree of memory impairment. The composite score for memory between the clusters remained significantly different despite adjustment for illness duration and age of onset (p < 0.001).

CONCLUSIONS

These data suggest clinical heterogeneity within an older group of people with AD. This may have implications for diagnosis, prognosis, response to currently available treatments, and the development of novel therapies.

Early-onset Alzheimer's disease: nonamnestic subtypes and type 2 AD

Patients with Alzheimer's disease (AD), the most prevalent neurodegenerative dementia, are usually elderly; however, ∼4-5% develop early-onset AD (EOAD) with onset before age 65. Most EOAD is sporadic, but about 5% of patients with EOAD have an autosomal dominant mutation such as Presenilin 1, Presenilin 2, or alterations in the Amyloid Precursor Protein gene. Although most Alzheimer's research has concentrated on older, late-onset AD (LOAD), there is much recent interest and research in EOAD. These recent studies indicate that EOAD is a heterogeneous disorder with significant differences from LOAD. From 22-64% of EOAD patients have a predominant nonamnestic syndrome presenting with deficits in language, visuospatial abilities, praxis, or other non-memory cognition. These nonamnestic patients may differ in several ways from the usual memory or amnestic patients. Patients with nonamnestic EOAD compared to typical amnestic AD have a more aggressive course, lack the apolipoprotein Eɛ4 (APOE ɛ4) susceptibility gene for AD, and have a focus and early involvement of non-hippocampal areas of brain, particularly parietal neocortex. These differences in the EOAD subtypes indicate differences in the underlying amyloid cascade, the prevailing pathophysiological theory for the development of AD. Together the results of recent studies suggest that nonamnestic subtypes of EOAD constitute a Type 2 AD distinct from the usual, typical disorder. In sum, the study of EOAD can reveal much about the clinical heterogeneity, predisposing factors, and neurobiology of this disease.

Comparison of clinical characteristics between familial and non-familial early onset Alzheimer's disease

Although familial Alzheimer's disease (FAD) is an early onset AD (EAD), most patients with EAD do not have a familial disorder. Recent guidelines recommend testing for genes causing FAD only in those EAD patients with two first-degree relatives. However, some patients with FAD may lack a known family history or other indications for suspecting FAD but might nonetheless be carriers of FAD mutations. The study was aimed to identify clinical features that distinguish FAD from non-familial EAD (NF-EAD). A retrospective review of a university-based cohort of 32 FAD patients with PSEN1-related AD and 81 with NF-EAD was conducted. The PSEN1 patients, compared to the NF-EAD patients, had an earlier age of disease onset (41.8 ± 5.2 vs. 55.9 ± 4.8 years) and, at initial assessment, a longer disease duration (5.1 ± 3.4 vs. 3.3 ± 2.6 years) and lower MMSE scores (10.74 ± 8.0 vs. 20.95 ± 5.8). Patients with NF-EAD were more likely to present with non-memory deficits, particularly visuospatial symptoms, than were FAD patients. When age, disease duration, and MMSE scores were controlled in a logistical regression model, FAD patients were more likely to have significant headaches, myoclonus, gait abnormality, and pseudobulbar affect than those with NF-EAD. In addition to a much younger age of onset, FAD patients with PSEN1 mutations differed from those with NF-EAD by a history of headaches and pseudobulbar affect, as well as myoclonus and gait abnormality on examination. These may represent differences in pathophysiology between FAD and NF-EAD and in some contexts such findings should lead to genetic counseling and appropriate recommendations for genetic testing for FAD.

[Early diagnosis of Alzheimer's disease]

INTRODUCTION

Diagnosis of Alzheimer's disease (AD) remains difficult to establish, and can only be considered as certain thanks to anatomopathological evidence, or genetic mutations. Current diagnostic criteria rely on innovative imaging and biological tools, in order to detect pathological cues from very early stages, and with best sensibility and sensitivity.

STATE OF ART

Advances in neuro-imaging enabled the development of different tools to help establishing the diagnosis, such as cerebral atrophy assessment on magnetic resonance imaging (MRI), and cerebral metabolism study on positron emission tomography (PET). Besides, the increasing use of in vivo biological markers, combined to clinical criteria, enables to discriminate patients from healthy controls at even earlier stages. This includes studies on tau and beta-amyloid proteins concentrations in the cerebrosinal fluid, and amyloid-specific radioligands uptake. Familial forms of Alzheimer represent a great model for studying early or even pre-symptomatic AD, as genetic analyses constitute a diagnosis of certainty, even though they usually evolve earlier and faster.

PERSPECTIVES, CONCLUSION

Diagnostic tools are more and more numerous and performant. According to patients' clinical heterogeneity, it appears essential to associate different method to investigate, in order to make a diagnosis as early and as reliable as possible.

Neuropsychological and neuroimaging markers in early versus late-onset Alzheimer's disease

BACKGROUND

Early-onset Alzheimer's disease (EOAD) has been overshadowed by the more common late-onset AD (LOAD). Yet, the literature indicates EOAD may have less hippocampal-memory presentations and more focal neocortical localization early in the disease.

OBJECTIVE

To evaluate these proposed differences between these 2 forms of AD and to explore what they inform about differences in AD pathophysiology.

METHODS

In all, 21 patients with EOAD and 24 patients with LOAD matched for disease progression and severity were compared on neurocognitive measures and resting state fluorodeoxy-glucose positron-emission tomography (FDG-PET).

RESULTS

Patients with EOAD had worse executive functions with greater hypometabolism in the parietal regions; whereas patients with LOAD had worse confrontation naming and verbal recognition memory with greater hypometabolism in inferior frontotemporal regions.

CONCLUSIONS

In addition to highlighting significant differences between EOAD and LOAD, these results reveal dissociation between executive deficits in AD and frontal hypometabolism, suggesting early disturbances of the parietal-frontal network in EOAD.

Nonamnestic presentations of early-onset Alzheimer's disease

Early-onset Alzheimer's disease (EOAD) beginning before the age of 65 may differ from late-onset AD (LOAD) in clinical course and frequency of nonamnestic presentations. In a 10-year retrospective review, 125 patients with EOAD, diagnosed clinically and verified by functional neuroimaging, were compared with 56 patients with LOAD and further classified depending on predominant cognitive difficulty on presentation. Eighty (64%) of the patients with EOAD had a nonamnestic presentation, compared with only 7 (12.5%) of the patients with LOAD. Compared with LOAD, the patients with EOAD had a shorter duration with lower Mini-Mental State Examination scores. The neuroimaging reports among the patients with EOAD showed more hippocampal atrophy with an amnestic presentation, more left parietal changes with impaired language presentations, and more right parietal and occipital changes with impaired visuospatial presentations. These findings indicate that EOAD differs from LOAD in a more aggressive course and in having predominantly nonamnestic presentations that vary in neuropathological location.

The paradox of syndromic diversity in Alzheimer disease

Variant syndromes of Alzheimer disease (AD), led by deficits that extend beyond memory dysfunction, are of considerable clinical and neurobiological importance. Such syndromes present major challenges for both diagnosis and monitoring of disease, and serve to illustrate the apparent paradox of a clinically diverse group of disorders underpinned by a common histopathological substrate. This Review focuses on the most common variant AD phenotypes: posterior cortical atrophy, logopenic variant primary progressive aphasia and frontal variant AD. The neuroanatomical, molecular and pathological correlates of these phenotypes are highlighted, and the heterogeneous clinical presentations of the syndromes are discussed in the context of the emerging network paradigm of neurodegenerative disease. We argue that these apparently diverse clinical phenotypes reflect the differential involvement of a common core temporoparietofrontal network that is vulnerable to AD. According to this interpretation, the network signatures corresponding to AD variant syndromes are produced by genetic and other modulating factors that have yet to be fully characterized. The clinical and neurobiological implications of this network paradigm in the quest for disease-modifying treatments are also explored.

The relation of executive functioning to CVLT-II learning, memory, and process indexes

Previous research has found that executive functioning plays a role in memory performance. This study sought to determine the amount of variance accounted for in the California Verbal Learning Test-Second Edition (CVLT-II) by a global executive-functioning factor score. Archival data were extracted from 285 outpatients in a mixed neurologic sample. Measures used included: CVLT-II, Wisconsin Card-Sorting Test (Perseverative Errors), Trail-Making Test-Part B, Controlled Oral Word Association Test, Animal Naming, and Wechsler Adult Intelligence Scale-Third Edition Similarities. Executive data were reduced to a single executive-functioning factor score for each individual. Regression was used to determine the amount of variance accounted for by executive functioning in CVLT-II performance. Executive functioning accounted for minimal variance (0%-10%) in the following CVLT-II indexes: Total Learning (Trials 1-5), Semantic Clustering, Repetitions, Intrusions, and False Positives. However, executive functioning accounted for substantial variance (24%-31%) in CVLT-II performance for both Short- and Long-Delay Recall indexes and most discriminability indexes. CVLT-II indexes that would intuitively be associated with executive functioning accounted for a smaller-than-expected amount of variance. Additionally, level of executive functioning was related to level of CVLT-II performance. These results suggest that clinicians should consider executive deficits when interpreting mild-to-moderate memory impairments in recall and discriminability functions but that executive abilities have little effect on other aspects of memory.

Amyloid burden and metabolic function in early-onset Alzheimer's disease: parietal lobe involvement

Alzheimer's disease with early onset often presents with a distinct cognitive profile, potentially reflecting a different distribution of underlying neuropathology. The purpose of this study was to examine the relationships between age and both in vivo fibrillary amyloid deposition and glucose metabolism in patients with Alzheimer's disease. Dynamic [(11)C]Pittsburgh compound-B (90 min) and static [(18)F]fluorodeoxyglucose (15 min) scans were obtained in 100 patients with Alzheimer's disease and 20 healthy controls. Parametric non-displaceable binding potential images of [(11)C]Pittsburgh compound-B and standardized uptake value ratio images of [(18)F]fluorodeoxyglucose were generated using cerebellar grey matter as reference tissue. Nine [(11)C]Pittsburgh compound-B-negative patients were excluded. The remaining patients were categorized into younger (n=45, age: 56 ± 4 years) and older (n=46, age: 69 ± 5 years) groups, based on the median age (62 years) at time of diagnosis. Younger patients showed more severe impairment on visuo-spatial function, attention and executive function composite scores (P<0.05), while we found a trend towards poorer memory performance for older patients (P=0.11). Differences between groups were assessed using a general linear model with repeated measures (gender adjusted) with age as between subjects factor, region (frontal, temporal, parietal and occipital and posterior cingulate cortices) as within subjects factor and [(11)C]Pittsburgh compound-B binding/[(18)F]fluorodeoxyglucose uptake as dependent variables. There was no main effect of age for [(11)C]Pittsburgh compound-B or [(18)F]fluorodeoxyglucose, suggesting that overall, the extent of amyloid deposition or glucose hypometabolism did not differ between groups. Regional distributions of [(11)C]Pittsburgh compound-B binding and [(18)F]fluorodeoxyglucose uptake (both P for interaction <0.05) differed between groups, however, largely due to increased [(11)C]Pittsburgh compound-B binding and decreased [(18)F]fluorodeoxyglucose uptake in the parietal cortex of younger patients (both P<0.05). Linear regression analyses showed negative associations between visuo-spatial functioning and parietal [(11)C]Pittsburgh compound-B binding for younger patients (standardized β: -0.37) and between visuo-spatial functioning and occipital binding for older patients (standardized β: -0.39). For [(18)F]fluorodeoxyglucose, associations were found between parietal uptake with visuo-spatial (standardized β: 0.55), attention (standardized β: 0.39) and executive functioning (standardized β: 0.37) in younger patients, and between posterior cingulate uptake and memory in older patients (standardized β: 0.41, all P<0.05). These in vivo findings suggest that clinical differences between younger and older patients with Alzheimer's disease are not restricted to topographical differentiation in downstream processes but may originate from distinctive distributions of early upstream events. As such, increased amyloid burden, together with metabolic dysfunction, in the parietal lobe of younger patients with Alzheimer's disease may contribute to the distinct cognitive profile in these patients.

Staging of the cognitive decline in Alzheimer's disease: insights from a detailed neuropsychological investigation of mild cognitive impairment and mild Alzheimer's disease

OBJECTIVE

The decline of episodic memory in Alzheimer's disease (AD) is well established, but the exact appearance and staging of deficits in other cognitive domains is sometimes contentious. The current investigation attempted to elucidate the appearance of additional cognitive deficits in the non-episodic domains and to understand these deficits with respect to the known pathological staging of AD.

METHODS

A cross-sectional investigation compared cognitively normal age-matched controls with patients with mild AD and mild cognitive impairment (MCI) using a detailed neuropsychological assessment.

RESULTS

The systematic investigation of cognitive performance across the major cognitive domains demonstrates that the appearance of additional cognitive deficits in MCI and AD can be predicted, with impaired semantic cognition performance pre-empting the appearance of attention/executive dysfunction and visuospatial deficits in the majority of patients with MCI.

CONCLUSIONS

This progressive pattern of cognitive deficits fits with the known pathological staging of AD, and the data further highlight the relative rarity of pure amnestic MCI. These results indicate that any neuropsychological test battery used to assess patients with MCI should include language and semantic memory tests in addition to typical episodic memory tests, as changes within this domain might be a sensitive indication of incipient AD.

Distinct clinical and pathological characteristics of frontotemporal dementia associated with C9ORF72 mutations

The identification of a hexanucleotide repeat expansion in the C9ORF72 gene as the cause of chromosome 9-linked frontotemporal dementia and motor neuron disease offers the opportunity for greater understanding of the relationship between these disorders and other clinical forms of frontotemporal lobar degeneration. In this study, we screened a cohort of 398 patients with frontotemporal dementia, progressive non-fluent aphasia, semantic dementia or mixture of these syndromes for mutations in the C9ORF72 gene. Motor neuron disease was present in 55 patients (14%). We identified 32 patients with C9ORF72 mutations, representing 8% of the cohort. The patients' clinical phenotype at presentation varied: nine patients had frontotemporal dementia with motor neuron disease, 19 had frontotemporal dementia alone, one had mixed semantic dementia with frontal features and three had progressive non-fluent aphasia. There was, as expected, a significant association between C9ORF72 mutations and presence of motor neuron disease. Nevertheless, 46 patients, including 22 familial, had motor neuron disease but no mutation in C9ORF72. Thirty-eight per cent of the patients with C9ORF72 mutations presented with psychosis, with a further 28% exhibiting paranoid, deluded or irrational thinking, whereas <4% of non-mutation bearers presented similarly. The presence of psychosis dramatically increased the odds that patients carried the mutation. Mutation bearers showed a low incidence of motor stereotypies, and relatively high incidence of complex repetitive behaviours, largely linked to patients' delusions. They also showed a lower incidence of acquired sweet food preference than patients without C9ORF72 mutations. Post-mortem pathology in five patients revealed transactive response DNA-binding protein 43 pathology, type A in one patient and type B in three. However, one patient had corticobasal degeneration pathology. The findings indicate that C9ORF72 mutations cause some but not all cases of frontotemporal dementia with motor neuron disease. Other mutations remain to be discovered. C9ORF72 mutations are associated with variable clinical presentations and pathology. Nevertheless, the findings highlight a powerful association between C9ORF72 mutations and psychosis and suggest that the behavioural characteristics of patients with C9ORF72 mutations are qualitatively distinct. Mutations in the C9ORF72 gene may be a major cause not only of frontotemporal dementia with motor neuron disease but also of late onset psychosis.

Insights into spared memory capacity in amnestic MCI and Alzheimer's Disease via minimal interference

Impairment on standard tests of delayed recall is often already maximal in the aMCI stage of Alzheimer's Disease. Neuropathological work shows that the neural substrates of memory function continue to deteriorate throughout the progression of the disease, hinting that further changes in memory performance could be tracked by a more sensitive test of delayed recall. Recent work shows that retention in aMCI patients can be raised well above floor when the delay period is devoid of further material - 'Minimal Interference'. This memory enhancement is thought to be the result of improved memory consolidation. Here we used the minimal interference/interference paradigm (word list retention following 10 min of quiet resting vs. picture naming) in a group of 17 AD patients, 25 aMCI patients and 25 controls. We found (1) that retention can be improved significantly by minimal interference in patients with aMCI and patients with mild to moderate AD; (2) that the minimal interference paradigm is sensitive to decline in memory function with disease severity, even when performance on standard tests has reached floor; and (3) that this paradigm can differentiate well (80% sensitivity and 100% specificity) between aMCI patients who progress and do not progress to AD within 2 years. Our findings support the notion that the early memory dysfunction in AD is associated with an increased susceptibility to memory interference and are suggestive of a gradual decline in consolidation capacity with disease progression.

Use of the CogState Brief Battery in the assessment of Alzheimer's disease related cognitive impairment in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study

The aim of this study was to validate the CogState Brief Battery, which assesses psychomotor, attentional, working memory, and visual learning functions, in healthy older people and in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD), enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study. In healthy older adults, weak relationships between demographic variables (e.g., education, depression) and cognitive performance were observed. In AD and MCI groups, the magnitude of impairment was greatest for tasks of working memory and memory, with a negative influence of apolipoprotein E ϵ4 status on learning but not working memory. These results suggest that the CogState Brief Battery can be used to screen for AD-related cognitive changes.

TDP-43 pathological changes in early onset familial and sporadic Alzheimer's disease, late onset Alzheimer's disease and Down's syndrome: association with age, hippocampal sclerosis and clinical phenotype

TDP-43 immunoreactive (TDP-43-ir) pathological changes were investigated in the temporal cortex and hippocampus of 11 patients with autosomal dominant familial forms of Alzheimer's disease (FAD), 169 patients with sporadic AD [85 with early onset disease (EOAD) (i.e before 65 years of age), and 84 with late onset after this age (LOAD)], 50 individuals with Down's Syndrome (DS) and 5 patients with primary hippocampal sclerosis (HS). TDP-43-ir pathological changes were present, overall, in 34/180 of AD cases. They were present in 1/11 (9%) FAD, and 9/85 (10%) EOAD patients but were significantly more common (p = 0.003) in LOAD where 24/84 (29%) patients showed such changes. There were no demographic differences, other than onset age, between AD patients with or without TDP-43-ir pathological changes. Double immunolabelling indicated that these TDP-43-ir inclusions were frequently ubiquitinated, but were only rarely AT8 (tau) immunoreactive. Only 3 elderly DS individuals and 4/5 cases of primary HS showed similar changes. Overall, 21.7% of AD cases and 6% DS cases showed hippocampal sclerosis (HS). However, only 9% FAD cases and 16% EOAD cases showed HS, but 29% LOAD cases showed HS. The proportion of EOAD cases with both TDP-43 pathology and HS tended to be greater than those in LOAD, where nearly half of all the cases with TDP-43 pathology did not show HS. The presence of TDP-43-ir changes in AD and DS may therefore be a secondary phenomenon, relating more to ageing than to AD itself. Nevertheless, a challenge to such an interpretation comes from the finding in AD of a strong relationship between TDP-43 pathology and cognitive phenotype. Patients with TDP-43 pathology were significantly more likely to present with an amnestic syndrome than those without (p < 0.0001), in keeping with pathological changes in medial temporal lobe structures. HS was also associated more commonly with an amnestic presentation (p < 0.005), but this association disappeared when TDP-43-positive cases were excluded from the analysis. TDP-43 may, after all, be integral to the pathology of AD, and to some extent determine the clinical phenotype present.

Impairments of auditory scene analysis in Alzheimer's disease

Parsing of sound sources in the auditory environment or ‘auditory scene analysis’ is a computationally demanding cognitive operation that is likely to be vulnerable to the neurodegenerative process in Alzheimer’s disease. However, little information is available concerning auditory scene analysis in Alzheimer's disease. Here we undertook a detailed neuropsychological and neuroanatomical characterization of auditory scene analysis in a cohort of 21 patients with clinically typical Alzheimer's disease versus age-matched healthy control subjects. We designed a novel auditory dual stream paradigm based on synthetic sound sequences to assess two key generic operations in auditory scene analysis (object segregation and grouping) in relation to simpler auditory perceptual, task and general neuropsychological factors. In order to assess neuroanatomical associations of performance on auditory scene analysis tasks, structural brain magnetic resonance imaging data from the patient cohort were analysed using voxel-based morphometry. Compared with healthy controls, patients with Alzheimer's disease had impairments of auditory scene analysis, and segregation and grouping operations were comparably affected. Auditory scene analysis impairments in Alzheimer's disease were not wholly attributable to simple auditory perceptual or task factors; however, the between-group difference relative to healthy controls was attenuated after accounting for non-verbal (visuospatial) working memory capacity. These findings demonstrate that clinically typical Alzheimer's disease is associated with a generic deficit of auditory scene analysis. Neuroanatomical associations of auditory scene analysis performance were identified in posterior cortical areas including the posterior superior temporal lobes and posterior cingulate. This work suggests a basis for understanding a class of clinical symptoms in Alzheimer's disease and for delineating cognitive mechanisms that mediate auditory scene analysis both in health and in neurodegenerative disease.

The logopenic variant of primary progressive aphasia

PURPOSE OF REVIEW

The aim is to explore the evolution of the logopenic variant of primary progressive aphasia as a distinct clinical entity and to outline recent advances that have clarified its clinical characteristics, neural underpinnings, and potential genetic and pathological bases. This is particularly relevant as researchers attempt to identify clinico-pathological relationships in subtypes of primary progressive aphasia in hopes of utilizing language phenotype as a marker of underlying disease.

RECENT FINDINGS

Recent work has served to refine and expand upon the clinical phenotype of the logopenic variant. Logopenic patients show a unique pattern of spared and impaired language processes that reliably distinguish this syndrome from other variants of progressive aphasia. Specifically, they exhibit deficits in naming and repetition in the context of spared semantic, syntactic, and motor speech abilities. Further, there is a growing body of evidence indicating a possible link between the logopenic phenotype and specific pathological and genetic correlates.

SUMMARY

Findings indicate that the logopenic variant is a distinct subtype of progressive aphasia that may hold value as a predictor of underlying pathology. Additional research, however, is warranted in order to further clarify the cognitive-linguistic profile and to confirm its relation to certain pathological and genetic processes.

The clinical diagnosis of early-onset dementias: diagnostic accuracy and clinicopathological relationships

Accuracy of clinical diagnosis of dementia is increasingly important for therapeutic and scientific investigations. In this study, we examine diagnostic accuracy in a consecutive series of 228 patients referred to a specialist early-onset dementia clinic, whose brains were subsequently examined at post-mortem. Diagnosis was based on structured history, neurological examination and neuropsychological assessment, with emphasis on qualitative as well as quantitative aspects of performance. Neuroimaging provided support for but did not alter the clinical diagnosis. We set out the principles that guided diagnosis: (i) time course of illness; (ii) weighting of physical, behavioural and cognitive symptoms and signs; (iii) 'anterior' versus 'posterior' hemisphere character of cognitive change; and (iv) specificity of deficit, paying attention to the differentiation between syndromes of frontotemporal lobar degeneration and focal forms of Alzheimer's disease. Forty-two per cent of the patients had clinical diagnoses of one of the syndromes of frontotemporal lobar degeneration, the high proportion reflecting the research interests of the group. Forty-six per cent were diagnosed with Alzheimer's disease and the remaining patients, dementia with Lewy bodies, Creutzfeldt-Jakob disease, vascular or unclassified dementia. Frontotemporal lobar degeneration was identified with 100% sensitivity and 97% specificity and Alzheimer's disease with 97% sensitivity and 100% specificity. Patients with other pathologies were accurately identified on clinical grounds. Examination of subsyndromes of frontotemporal lobar degeneration showed a relatively predictable relationship between clinical diagnosis and pathological subtype. Whereas the behavioural disorder of frontotemporal dementia was associated with tau, transactive response DNA binding protein 43 and fused-in-sarcoma pathology, cases of frontotemporal dementia with motoneuron disease, semantic dementia and, with one exception, progressive non-fluent aphasia were associated with transactive response DNA binding protein 43 pathology, distinguished by ubiquitin subtyping (types B, C and A, respectively). Clinical diagnoses of progressive apraxia, corticobasal degeneration and progressive supranuclear palsy were, with one exception, associated with Pick, corticobasal and progressive supranuclear palsy subtypes of tau pathology, respectively. Unanticipated findings included Alzheimer pathology in two patients presenting with the behavioural syndrome of frontotemporal dementia and corticobasal pathology in four others with clinical frontotemporal dementia. Notwithstanding such anomalies, which serve as a reminder that there is not an absolute concordance between clinical phenotype and underlying pathology, the findings show that dementias can be distinguished in life with a high level of accuracy. Moreover, careful clinical phenotyping allows prediction of histopathological subtype of frontotemporal lobar degeneration. The principles guiding diagnosis provide the foundation for future prospective studies.

Cognitive phenotypes in Alzheimer's disease and genetic variants in ACE and IDE

Alzheimer's disease (AD) is generally considered to be a disorder primarily affecting memory. It is increasingly recognized that the clinical presentation or "cognitive phenotype" is variable. The apolipoprotein E ε4 (APOE ε4) allele has been associated with an amnestic presentation, but does not appear to fully explain the high prevalence of family history within this group. We examined polymorphisms in the genes ACE and IDE in relation to cognitive phenotype. In this study 276 participants with AD were categorized into 1 of 4 cognitive phenotype classifications: typical, amnestic, language, and posterior. Family history and possession of the APOE ε4 allele were most prevalent in the amnestic group. Of the 10 genetic variants of IDE, and the 3 genetic variants of ACE studied, only ACErs4291 and ACErs1800764 were nominally associated with the amnestic presentation.

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

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

Cluster analysis of symptoms among patients with upper extremity musculoskeletal disorders

INTRODUCTION

Some musculoskeletal disorders of the upper extremity are not readily classified. The study objective was to determine if there were symptom patterns in self-identified repetitive strain injury (RSI) patients.

METHODS

Members (n = 700) of the Dutch RSI Patients Association filled out a detailed symptom questionnaire. Factor analysis followed by cluster analysis grouped correlated symptoms.

RESULTS

Eight clusters, based largely on symptom severity and quality were formulated. All but one cluster showed diffuse symptoms; the exception was characterized by bilateral symptoms of stiffness and aching pain in the shoulder/neck.

CONCLUSIONS

Case definitions which localize upper extremity musculoskeletal disorders to a specific anatomical area may be incomplete. Future clustering studies should rely on both signs and symptoms. Data could be collected from health care providers prospectively to determine the possible prognostic value of the identified clusters with respect to natural history, chronicity, and return to work.

Apolipoprotein E (APOE) genotype has dissociable effects on memory and attentional-executive network function in Alzheimer's disease

The epsilon4 allele of the apolipoprotein E (APOE) gene is the major genetic risk factor for Alzheimer's disease (AD), but limited work has suggested that APOE genotype may modulate disease phenotype. Carriers of the epsilon4 allele have been reported to have greater medial temporal lobe (MTL) pathology and poorer memory than noncarriers. Less attention has focused on whether there are domains of cognition and neuroanatomical regions more affected in noncarriers. Further, a major potential confound of prior in vivo studies is the possibility of different rates of clinical misdiagnosis for carriers vs. noncarriers. We compared phenotypic differences in cognition and topography of regional cortical atrophy of epsilon4 carriers (n = 67) vs. noncarriers (n = 24) with mild AD from the Alzheimer's Disease Neuroimaging Initiative, restricted to those with a cerebrospinal fluid (CSF) molecular profile consistent with AD. Between-group comparisons were made for psychometric tests and morphometric measures of cortical thickness and hippocampal volume. Carriers displayed significantly greater impairment on measures of memory retention, whereas noncarriers were more impaired on tests of working memory, executive control, and lexical access. Consistent with this cognitive dissociation, carriers exhibited greater MTL atrophy, whereas noncarriers had greater frontoparietal atrophy. Performance deficits in particular cognitive domains were associated with disproportionate regional brain atrophy within nodes of cortical networks thought to subserve these cognitive processes. These convergent cognitive and neuroanatomic findings in individuals with a CSF molecular profile consistent with AD support the hypothesis that APOE genotype modulates the clinical phenotype of AD through influence on specific large-scale brain networks.

An exploration of cognitive subgroups in Alzheimer's disease

Heterogeneity is observed in the patterns of cognition in Alzheimer's disease (AD). Such heterogeneity might suggest the involvement of different etiological pathways or different host responses to pathology. A total of 627 subjects with mild/moderate AD underwent cognitive assessment with the Mini-Mental State Examination (MMSE) and the Dementia Rating Scale-2 (DRS-2). Latent class analysis (LCA) was performed on cognition subscale data to identify and characterize cognitive subgroups. Clinical, demographic, and genetic factors were explored for association with class membership. LCA suggested the existence of four subgroups; one group with mild and another with severe global impairment across the cognitive domains, one group with primary impairments in attention and construction, and another group with primary deficits in memory and orientation. Education, disease duration, age, Apolipoprotein E-epsilon4 (APOE epsilon4) status, gender, presence of grasp reflex, white matter changes, and early or prominent visuospatial impairment were all associated with class membership. Our results support the existence of heterogeneity in patterns of cognitive impairment in AD. Our observation of classes characterized by predominant deficits in attention/construction and memory respectively deserves further exploration as does the association between membership in the attention/construction class and APOE epsilon4 negative status.

Progressive logopenic/phonological aphasia: erosion of the language network

The primary progressive aphasias (PPA) are paradigmatic disorders of language network breakdown associated with focal degeneration of the left cerebral hemisphere. Here we addressed brain correlates of PPA in a detailed neuroanatomical analysis of the third canonical syndrome of PPA, logopenic/phonological aphasia (LPA), in relation to the more widely studied clinico-anatomical syndromes of semantic dementia (SD) and progressive nonfluent aphasia (PNFA). 32 PPA patients (9 SD, 14 PNFA, 9 LPA) and 18 cognitively normal controls had volumetric brain MRI with regional volumetry, cortical thickness, grey and white matter voxel-based morphometry analyses. Five of nine patients with LPA had cerebrospinal fluid biomarkers consistent with Alzheimer (AD) pathology (AD-PPA) and 2/9 patients had progranulin (GRN) mutations (GRN-PPA). The LPA group had tissue loss in a widespread left hemisphere network. Compared with PNFA and SD, the LPA group had more extensive involvement of grey matter in posterior temporal and parietal cortices and long association white matter tracts. Overlapping but distinct networks were involved in the AD-PPA and GRN-PPA subgroups, with more anterior temporal lobe involvement in GRN-PPA. The importance of these findings is threefold: firstly, the clinico-anatomical entity of LPA has a profile of brain damage that is complementary to the network-based disorders of SD and PNFA; secondly, the core phonological processing deficit in LPA is likely to arise from temporo-parietal junction damage but disease spread occurs through the dorsal language network (and in GRN-PPA, also the ventral language network); and finally, GRN mutations provide a specific molecular substrate for language network dysfunction.

Visuospatial function in early Alzheimer's disease: Preliminary study

Alzheimer’s disease (AD) is the most frequent cause of dementia, accounting for 55% of all cases. AD patients gradually lose functional capacity, manifesting deficits in attention, language, temporal and direction orientation, mood, socialization and visuospatial function. The visuospatial function entails identification of a stimulus and its location. AD patients can present deficits in visuo-spatial skills during initial stages of the disease, but in the course of clinical evolution this function can become severely impaired. One of the neuropsychological tests indicated to evaluate the visuospatial function is the VOSP (The Visual Object and Space Perception Battery).

Musical memory in Alzheimer disease

This study examines musical memory in 12 patients with moderate or severe AD and 12 healthy, older adult controls. Participants were asked to distinguish familiar from novel tunes, to identify distortions in melodies, and to sing familiar tunes. Comparison of the AD and control groups showed significant impairment of the AD participants. However, a more complex picture emerged as we compared each individual case to the control group. Five of the AD group performed within the control group range on most tasks. An additional four participants showed partial sparing in that they performed below the range of control participants, but their scores were above the level of chance. The final three participants showed near complete loss of musical memory, as their performance was consistently at or near the level of chance. These results are discussed in terms of the literature on the heterogeneity of cognitive presentation in AD.

Methodological improvements in quantifying cognitive change in clinical trials: an example with single-dose administration of donepezil

OBJECTIVES

Change in cognitive function in response to a pharmacologic challenge can be observed with greater sensitivity by employing cognitive tests with optimal psychometric properties and a statistical approach that more accurately accounts for individual variability in performance. To demonstrate this approach we examined the cognitive effects of a single acute dose administration of an acetylcholinesterase inhibitor, donepezil, in healthy older adults and in older adults with mild Alzheimer's disease (AD).

DESIGN

Placebo-controlled crossover study with three separate testing days: baseline, placebo, and donepezil, with assessments at baseline, and 1-, 2-, 3-, 6-, and 8-hrs post-dosing on each day.

SETTING

Early phase I clinical trial.

PARTICIPANTS

15 healthy older adults; 14 older adults with mild Alzheimer's disease.

INTERVENTION

Single acute dose of 5mg donepezil.

MEASUREMENTS

Performance on the Groton Maze Learning Test (GMLT), a computerized neuropsychological measure of spatial working memory and error monitoring.

RESULTS

A single acute dose of donepezil improved GMLT performance in healthy older adults (effect size: 0.83 at 6 hrs post-dosing) and older adults with mild AD (effect size: 0.58 at 3 hrs post-dosing).

CONCLUSION

The GMLT detected cognitive improvement following a single, acute dose administration of donepezil in healthy older adults and older adults with mild AD. The choice of cognitive tests designed for repeated administration, as well as an analytic approach that emphasizes individual-level change in cognitive function, provides a sensitive approach to detecting central nervous system drug penetration and activity of cognitive-enhancing agents.

Frontotemporal lobar degeneration: clinical and pathological relationships

Frontotemporal lobar degeneration (FTLD) encompasses a heterogeneous group of clinical syndromes that include frontotemporal dementia (FTD), frontotemporal dementia with motor neurone disease (FTD/MND), progressive non-fluent aphasia (PNFA), semantic dementia (SD) and progressive apraxia (PAX). Clinical phenotype is often assumed to be a poor predictor of underlying histopathology. Advances in immunohistochemistry provide the opportunity to re-examine this assumption. We classified pathological material from 79 FTLD brains, blind to clinical diagnosis, according to topography of brain atrophy and immunohistochemical characteristics. There were highly significant relationships to clinical syndrome. Atrophy was predominantly frontal and anterior temporal in FTD, frontal in FTD/MND, markedly asymmetric perisylvian in PNFA, asymmetric bitemporal in SD and premotor, parietal in PAX. Tau pathology was found in half of FTD and all PAX cases but in no FTD/MND or SD cases and only rarely in PNFA. FTD/MND, SD and PNFA cases were ubiquitin and TDP-43 positive. SD cases were associated with dystrophic neurites without neuronal cytoplasmic or intranuclear inclusions (FTLD-U, type 1), FTD/MND with numerous neuronal cytoplasmic inclusions (FTLD-U, type 2 ) and PNFA with neuronal cytoplasmic inclusions, dystrophic neurites and neuronal intranuclear inclusions (FTLD-U, type 3). MAPT mutations were linked to FTD and PGRN mutations to FTD and PNFA. The findings demonstrate predictable relationships between clinical phenotype and both topographical distribution of brain atrophy and immunohistochemical characteristics. The findings emphasise the importance of refined delineation of both clinical and pathological phenotype in furthering understanding of FTLD and its molecular substrate.