Hippocampal subfield pathologic burden in Lewy body diseases vs. Alzheimer's disease.

AIMS: Lewy body diseases (LBD) are characterized by alpha-synuclein (SYN) pathology, but comorbid Alzheimer's disease (AD) pathology is common and the relationship between these pathologies in microanatomic hippocampal subfields is understudied. Here we use digital histological methods to test the association between hippocampal SYN pathology and the distribution of tau and amyloid-beta (Aß) pathology in LBD and contrast with AD subjects. We also correlate pathologic burden with antemortem episodic memory testing. METHODS: Hippocampal sections from 49 autopsy-confirmed LBD cases, 30 with no/low AD copathology (LBD - AD) and 19 with moderate/severe AD copathology (LBD + AD), and 30 AD patients were stained for SYN, tau, and Aß. Sections underwent digital histological analysis of subfield pathological burden which was correlated with antemortem memory testing. RESULTS: LBD - AD and LBD + AD had similar severity and distribution of SYN pathology (P > 0.05), CA2/3 being the most affected subfield (P < 0.02). In LBD, SYN correlated with tau across subfields (R = 0.49, P < 0.001). Tau burden was higher in AD than LBD + AD (P < 0.001), CA1/subiculum and entorhinal cortex (ERC) being most affected regions (P = 0.04 to <0.01). However, tau pathology in LBD - AD was greatest in CA2/3, which was equivalent to LBD + AD. Aß severity and distribution was similar between LBD + AD and AD. Total hippocampal tau and CA2/3 tau was inversely correlated with memory performance in LBD (R = -0.52, -0.69, P = 0.04, 0.009). CONCLUSIONS: Our findings suggest that tau burden in hippocampal subfields may map closely with the distribution of SYN pathology in subfield CA2/3 in LBD diverging from traditional AD and contribute to episodic memory dysfunction in LBD.

Comparison of sporadic and familial behavioral variant frontotemporal dementia (FTD) in a North American cohort.

INTRODUCTION: Behavioral variant frontotemporal dementia (bvFTD) may present sporadically or due to an autosomal dominant mutation. Characterization of both forms will improve understanding of the generalizability of assessments and treatments. METHODS: A total of 135 sporadic (s-bvFTD; mean age 63.3 years; 34% female) and 99 familial (f-bvFTD; mean age 59.9; 48% female) bvFTD participants were identified. f-bvFTD cases included 43 with known or presumed chromosome 9 open reading frame 72 (C9orf72) gene expansions, 28 with known or presumed microtubule-associated protein tau (MAPT) mutations, 14 with known progranulin (GRN) mutations, and 14 with a strong family history of FTD but no identified mutation. RESULTS: Participants with f-bvFTD were younger and had earlier age at onset. s-bvFTD had higher total Neuropsychiatric Inventory Questionnaire (NPI-Q) scores due to more frequent endorsement of depression and irritability. DISCUSSION: f-bvFTD and s-bvFTD cases are clinically similar, suggesting the generalizability of novel biomarkers, therapies, and clinical tools developed in either form to the other.

Active lifestyles moderate clinical outcomes in autosomal dominant frontotemporal degeneration.

INTRODUCTION: Leisure activities impact brain aging and may be prevention targets. We characterized how physical and cognitive activities relate to brain health for the first time in autosomal dominant frontotemporal lobar degeneration (FTLD). METHODS: A total of 105 mutation carriers (C9orf72/MAPT/GRN) and 69 non-carriers reported current physical and cognitive activities at baseline, and completed longitudinal neurobehavioral assessments and brain magnetic resonance imaging (MRI) scans. RESULTS: Greater physical and cognitive activities were each associated with an estimated >55% slower clinical decline per year among dominant gene carriers. There was also an interaction between leisure activities and frontotemporal atrophy on cognition in mutation carriers. High-activity carriers with frontotemporal atrophy (-1 standard deviation/year) demonstrated >two-fold better cognitive performances per year compared to their less active peers with comparable atrophy rates. DISCUSSION: Active lifestyles were associated with less functional decline and moderated brain-to-behavior relationships longitudinally. More active carriers "outperformed" brain volume, commensurate with a cognitive reserve hypothesis. Lifestyle may confer clinical resilience, even in autosomal dominant FTLD.

Classification of primary progressive aphasia and its variants.

This article provides a classification of primary progressive aphasia (PPA) and its 3 main variants to improve the uniformity of case reporting and the reliability of research results. Criteria for the 3 variants of PPA--nonfluent/agrammatic, semantic, and logopenic--were developed by an international group of PPA investigators who convened on 3 occasions to operationalize earlier published clinical descriptions for PPA subtypes. Patients are first diagnosed with PPA and are then divided into clinical variants based on specific speech and language features characteristic of each subtype. Classification can then be further specified as "imaging-supported" if the expected pattern of atrophy is found and "with definite pathology" if pathologic or genetic data are available. The working recommendations are presented in lists of features, and suggested assessment tasks are also provided. These recommendations have been widely agreed upon by a large group of experts and should be used to ensure consistency of PPA classification in future studies. Future collaborations will collect prospective data to identify relationships between each of these syndromes and specific biomarkers for a more detailed understanding of clinicopathologic correlations.

Clinical syndromes associated with posterior atrophy: early age at onset AD spectrum.

OBJECTIVE: Posterior cortical atrophy (PCA) and logopenic progressive aphasia (LPA) are clinical syndromes associated with posterior brain atrophy. We compared PCA and LPA to each other and to an age-matched group of patients with early age at onset of Alzheimer disease (EO-AD). We hypothesized that these 3 syndromes are part of a single clinical and biologic continuum. METHODS: Voxel-based morphometry (VBM) was used to assess atrophy in 14 PCA, 10 LPA, and 16 EO-AD patients compared to 65 healthy controls. Genetic analysis for APOE was conducted in 30 patients and 44 controls. Four patients came to autopsy. An additional 14 were studied with the beta-amyloid specific PET with tracer (11)C-labeled Pittsburgh Compound-B (PIB). RESULTS: VBM results demonstrated that, compared to controls, each patient group showed a large area of overlapping atrophy in bilateral parietal, occipital, precuneus, posterior cingulate, posterior temporal, and hippocampal regions. Surrounding this common area, group-specific atrophy was found in small, symptom-specific regions for each group: the right ventral-occipital and superior parietal regions in PCA, the left middle and superior temporal gyri in LPA, and the prefrontal cortex in EO-AD. APOE epsilon4 frequency was higher in all patient groups compared to controls. Four PCA, 5 LPA, and 8 EO-AD patients showed evidence of cortical amyloid at pathology (n = 3) or on PIB-PET (n = 14). CONCLUSIONS: Logopenic progressive aphasia and posterior cortical atrophy showed largely overlapping anatomic and biologic features with early age at onset of Alzheimer disease, suggesting that these clinical syndromes represent the spectrum of clinical manifestation of the nontypical form of Alzheimer disease that presents at an early age.

Distinct MRI atrophy patterns in autopsy-proven Alzheimer's disease and frontotemporal lobar degeneration.

To better define the anatomic distinctions between Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD), we retrospectively applied voxel-based morphometry to the earliest magnetic resonance imaging scans of autopsy-proven AD (N = 11), FTLD (N = 18), and controls (N = 40). Compared with controls, AD patients showed gray matter reductions in posterior temporoparietal and occipital cortex; FTLD patients showed atrophy in medial prefrontal and medial temporal cortex, insula, hippocampus, and amygdala; and patients with both disorders showed atrophy in dorsolateral and orbital prefrontal cortex and lateral temporal cortex (P(FWE-corr) < .05). Compared with FTLD, AD patients had decreased gray matter in posterior parietal and occipital cortex, whereas FTLD patients had selective atrophy in anterior cingulate, frontal insula, subcallosal gyrus, and striatum (P < .001, uncorrected). These findings suggest that AD and FTLD are anatomically distinct, with degeneration of a posterior parietal network in AD and degeneration of a paralimbic fronto-insular-striatal network in FTLD.

Rate of progression differs in frontotemporal dementia and Alzheimer disease.

OBJECTIVE: To compare survival and rates of cognitive and functional decline in patients with autopsy-confirmed frontotemporal dementia (FTD) and Alzheimer disease (AD) in a large multicenter study. BACKGROUND: Despite advances in the clinical characterization of FTD, little is known about its rate of progression. Characterizing survival and rate of decline in FTD is important because it can provide prognostic guidelines and benchmarks to use in the evaluation of disease-modifying drugs. METHODS: Seventy patients with FTD and 70 patients with AD who were followed by seven Alzheimer disease research centers until confirmation of diagnosis at autopsy were matched for overall age, education, and Mini-Mental State Examination (MMSE) score at initial evaluation. Survival and rates of cognitive and functional decline were compared. RESULTS: Patients with FTD had significantly shorter survival from initial evaluation to death than patients with AD (FTD = 4.2 years, AD = 6.0 years; log-rank test = 5.17, p < 0.05), and they declined significantly faster over one year on the MMSE (mean annual rate of change: -6.7 points for FTD vs -2.3 points for AD). A significantly greater proportion of patients with FTD were impaired in basic activities of daily living (ADLs) at initial evaluation, and lost the capacity for independent or minimally-assisted ADLs over the subsequent year. CONCLUSIONS: The results are consistent with shorter survival and faster rates of cognitive and functional decline in patients with frontotemporal dementia (FTD) compared to those with Alzheimer disease (AD). This suggests that FTD follows a more malignant disease course than AD once dementia is clinically recognized.

Cognitive profiles differ in autopsy-confirmed frontotemporal dementia and AD.

BACKGROUND: Frontotemporal dementia (FTD) is currently distinguished from AD primarily on the basis of behavioral features because studies of cognition have shown negligible or inconsistent differences. However, the poor discriminability of cognitive measures may relate to reliance on imprecise clinically diagnosed groups. Therefore, a retrospective examination of neuropsychological test performance in autopsy-confirmed patients is warranted. OBJECTIVE: To compare the pattern of cognitive deficits exhibited by patients with autopsy-confirmed FTD and AD. METHODS: The profiles of cognitive deficits exhibited by patients with neuropathologic diagnosis of FTD (n = 14) or AD (n = 28) were compared. The Mattis Dementia Rating Scale (MDRS), letter and category fluency tests, Wechsler Intelligence Scale for Children-Revised block design test, Boston naming test, and clock drawing test were administered. RESULTS: Multivariate analysis of covariance controlling for age, education, and level of dementia revealed that patients with FTD performed significantly worse than patients with AD on letter and category fluency tests but significantly better on the MDRS memory subscale, block design test, and clock drawing test. A logistic regression model, validated in an independent clinical sample, used letter fluency, MDRS memory, and block design scores to correctly classify 91% of AD patients and 77% of FTD patients. CONCLUSIONS: A double dissociation in the pattern of cognitive deficits exhibited by FTD and AD patients was demonstrated. The FTD patients were more impaired than AD patients on word generation tasks (i.e., verbal fluency) that are sensitive to frontal lobe dysfunction but less impaired on tests of memory and visuospatial abilities sensitive to dysfunction of medial temporal and parietal association cortices.