Anatomical heterogeneity of Alzheimer disease: based on cortical thickness on MRIs

OBJECTIVE

Because the signs associated with dementia due to Alzheimer disease (AD) can be heterogeneous, the goal of this study was to use 3-dimensional MRI to examine the various patterns of cortical atrophy that can be associated with dementia of AD type, and to investigate whether AD dementia can be categorized into anatomical subtypes.

METHODS

High-resolution T1-weighted volumetric MRIs were taken of 152 patients in their earlier stages of AD dementia. The images were processed to measure cortical thickness, and hierarchical agglomerative cluster analysis was performed using Ward's clustering linkage. The identified clusters of patients were compared with an age- and sex-matched control group using a general linear model.

RESULTS

There were several distinct patterns of cortical atrophy and the number of patterns varied according to the level of cluster analyses. At the 3-cluster level, patients were divided into (1) bilateral medial temporal-dominant atrophy subtype (n = 52, ∼ 34.2%), (2) parietal-dominant subtype (n = 28, ∼ 18.4%) in which the bilateral parietal lobes, the precuneus, along with bilateral dorsolateral frontal lobes, were atrophic, and (3) diffuse atrophy subtype (n = 72, ∼ 47.4%) in which nearly all association cortices revealed atrophy. These 3 subtypes also differed in their demographic and clinical features.

CONCLUSIONS

This cluster analysis of cortical thickness of the entire brain showed that AD dementia in the earlier stages can be categorized into various anatomical subtypes, with distinct clinical features.

Amyloid burden, cerebrovascular disease, brain atrophy, and cognition in cognitively impaired patients

BACKGROUND

We investigated the independent effects of Alzheimer's disease (AD) and cerebrovascular disease (CVD) pathologies on brain structural changes and cognition.

METHODS

Amyloid burden (Pittsburgh compound B [PiB] retention ratio), CVD markers (volume of white matter hyperintensities [WMH] and number of lacunae), and structural changes (cortical thickness and hippocampal shape) were measured in 251 cognitively impaired patients. Path analyses were utilized to assess the effects of these markers on cognition.

RESULTS

PiB retention ratio was associated with hippocampal atrophy, which was associated with memory impairment. WMH were associated with frontal thinning, which was associated with executive and memory dysfunctions. PiB retention ratio and lacunae were also associated with memory and executive dysfunction without the mediation of hippocampal or frontal atrophy.

CONCLUSIONS

Our results suggest that the impacts of AD and CVD pathologies on cognition are mediated by specific brain regions.

Renal function, attributes and coagulation treatment in atrial fibrillation (R-FACT Study): retrospective, observational, longitudinal cohort study of renal function and antithrombotic treatment patterns in atrial fibrillation patients with documented eGFR in real-world clinical practices in Germany

AIMS

This retrospective, observational, longitudinal study aimed to document the distribution, changes in renal function [measured by estimated glomerular filtration (eGFR)] and antithrombotic treatment pattern in atrial fibrillation (AF) patients in real-world settings managed by general practitioners in Germany.

METHODS AND RESULTS

Data were extracted from the German Longitudinal Patient Database. A total of 15,900 patients with AF were identified. Among 1660 having eGFR available at baseline, 3.4% had severely impaired eGFR, 9.7% and 25.6% had moderate severe decrease and moderate decrease in eGFR, respectively, and 61.3% had mildly decreased/normal eGFR. Patients with moderately and severely decreased eGFR tended to be older. The proportion of patients with a CHADS2 score ≥ 2 was 92.9% in those with severely decreased eGFR, and 87.0% and 79.1% in those with moderately severe and moderately decreased eGFR. During follow up, 52.1% of patients with severely decreased eGFR, and 26.3% to 23.7% of patients with moderately decreased eGFR were not treated by antithrombotic. When comparing baseline with follow-up eGFR, 55.0% of patients showed decreased eGFR. Age, diabetes, dyslipidaemia and history of myocardial infarction were identified as significant predictors for renal function deterioration based on results from multivariate Cox regression model.

CONCLUSIONS

Moderate-to-severe renal dysfunction is prevalent (~38%) in German AF patients with documented eGFR managed in actual clinical practices. The risk of stroke, as measured by the CHADS2 score, was associated with decreased renal function. Treatment with anticoagulation therapies decreased with decreasing renal function, despite increasing risk of stroke. Anticoagulation treatments remain suboptimal during the 12-month follow up in patients with moderate or severe renal impairment.

Synergistic effects of ischemia and β-amyloid burden on cognitive decline in patients with subcortical vascular mild cognitive impairment

IMPORTANCE

Cerebrovascular disease (CVD) and Alzheimer disease are significant causes of cognitive impairment in the elderly. However, few studies have evaluated the relationship between CVD and β-amyloid burden in living humans or their synergistic effects on cognition. Thus, there is a need for better understanding of mild cognitive impairment (MCI) before clinical deterioration begins.

OBJECTIVE

To determine the synergistic effects of β-amyloid burden and CVD on cognition in patients with subcortical vascular MCI (svMCI).

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study was conducted using a hospital-based sample at a tertiary referral center. We prospectively recruited 95 patients with svMCI; 67 of these individuals participated in the study. Forty-five patients with amnestic MCI (aMCI) were group matched with those with svMCI by the Clinical Dementia Rating Scale Sum of Boxes.

MAIN OUTCOMES AND MEASURES

We measured β-amyloid burden using positron emission tomography with carbon 11-labeled Pittsburgh Compound B (PiB). Cerebrovascular disease was quantified as white matter hyperintensity volume detected by magnetic resonance imaging fluid-attenuated inversion recovery. Detailed neuropsychological tests were performed to determine the level of patients' cognitive impairment.

RESULTS

On evaluation, 22 of the svMCI group (33%) and 28 of the aMCI group (62%) were found to be PiB positive. The mean PiB retention ratio was lower in patients with svMCI than in those with aMCI. In svMCI, the PiB retention ratio was associated with cognitive impairments in multiple domains, including language, visuospatial, memory, and frontal executive functions, but was associated only with memory dysfunction in aMCI. A significant interaction between PiB retention ratio and white matter hyperintensity volume was found to affect visuospatial function in patients with svMCI.

CONCLUSIONS AND RELEVANCE

Most patients with svMCI do not exhibit substantial amyloid burden, and CVD does not increase β-amyloid burden as measured by amyloid imaging. However, in patients with svMCI, amyloid burden and white matter hyperintensity act synergistically to impair visuospatial function. Therefore, our findings highlight the need for accurate biomarkers, including neuroimaging tools, for early diagnosis and the need to relate these biomarkers to cognitive measurements for effective use in the clinical setting.

Automated radiosynthesis of N-succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) for peptides and proteins radiolabeling for positron emission tomography

Recently, silicon fluoride building blocks (SiFA) have emerged as valuable and promising tools to overcome challenges in the labeling of peptides and proteins for positron emission tomography (PET). Herein, we report a fully automated synthesis of N-succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) by a commercially available Scintomics Hot Box 3 synthesis module, to be used as a prosthetic group for peptide and protein labeling. The drying of K2.2.2./K (18)F complex was performed according to the Munich method modified by our group (avoiding azeotropic drying) using oxalic acid to neutralize the base from the (18)F(-) containing QMA eluent. This K2.2.2./K (18)F complex was then used for SiFA (18)F-(19)F isotopic exchange followed by a fast purification by a solid-phase-extraction (SPE) to afford [(18)F]SiFB with an average preparative radiochemical yield (RCY) of 24±1% (non-decay corrected (NDC)) within a synthesis time of 30 min. The [(18)F]SiFB produced by automated synthesis was then used for the (18)F-labeling of rat serum albumin (RSA) as a proof of applicability.

Cortical thickness and hippocampal shape in pure vascular mild cognitive impairment and dementia of subcortical type

BACKGROUND AND PURPOSE

The progression pattern of brain structural changes in patients with isolated cerebrovascular disease (CVD) remains unclear. To investigate the role of isolated CVD in cognitive impairment patients, patterns of cortical thinning and hippocampal atrophy in pure subcortical vascular mild cognitive impairment (svMCI) and pure subcortical vascular dementia (SVaD) patients were characterized.

METHODS

Forty-five patients with svMCI and 46 patients with SVaD who were negative on Pittsburgh compound B (PiB) positron emission tomography imaging and 75 individuals with normal cognition (NC) were recruited.

RESULTS

Compared with NC, patients with PiB(-) svMCI exhibited frontal, language and retrieval type memory dysfunctions, which in patients with PiB(-) SVaD were further impaired and accompanied by visuospatial and recognition memory dysfunctions. Compared with NC, patients with PiB(-) svMCI exhibited cortical thinning in the frontal, perisylvian, basal temporal and posterior cingulate regions. This atrophy was more prominent and extended further toward the lateral parietal and medial temporal regions in patients with PiB(-) SVaD. Compared with NC subjects, patients with PiB(-) svMCI exhibited hippocampal shape deformities in the lateral body, whilst patients with PiB(-) SVaD exhibited additional deformities within the lateral head and inferior body.

CONCLUSIONS

Our findings suggest that patients with CVD in the absence of Alzheimer's disease pathology can be demented, showing cognitive impairment in multiple domains, which is consistent with the topography of cortical thinning and hippocampal shape deformity.

Amyloid deposition in early onset versus late onset Alzheimer's disease

BACKGROUND

Patients with early-onset Alzheimer's disease (EOAD) may differ from those with late-onset Alzheimer's disease (LOAD) in cognitive impairment profiles and clinical course. Postmortem studies also reported that EOAD has a greater pathologic burden than LOAD. We examined the effects of age at onset on the burden and distribution of amyloid plaques in patients with AD, using a statistical parametric mapping (SPM) and regions of interest (ROIs) analyses of the Pittsburgh compound B (PiB)-PET.

METHODS

We initially recruited 72 patients with AD who had completed the [11C] PiB-PET scan, but four patients were excluded due to familial AD or incomplete MRI data. Of the 68 patients, 61 were classified as PiB-positive (PiB+) and seven as PiB-negative (PiB-) using the measured global PiB uptake ratio values. Of the 61 patients with PiB+ AD, in order to maximize the effect of onset age, we excluded 20 patients in their 60 s. Thus among the remaining 41 patients, the amyloid deposition of only 17 patients with EOAD (age onset <60 years) and 24 patients with LOAD (onset age ≥70 years) were compared.

RESULTS

There were no significant differences in the global mean PiB index between EOAD and LOAD patients, whereas SPM and ROIs analyses showed that those with EOAD retained higher levels of PiB in the bilateral basal ganglia, bilateral thalamus, left superior temporal cortex, and left cuneus compared to those with LOAD.

CONCLUSION

Our findings demonstrated that EOAD patients differed from those with LOAD in the topography of amyloid deposition, which may partly account for the findings from previous studies that extrapyramidal symptoms and frontal dysfunction are more common in EOAD than in LOAD patients.

Survival of Alzheimer's disease patients in Korea

BACKGROUND/AIMS

The natural history of Alzheimer's disease (AD) has rarely been studied in the Korean population. Our study on survival analyses in Korean AD patients potentially provides a basis for cross-cultural comparisons.

METHODS

We studied 724 consecutive patients from a memory disorder clinic in a tertiary hospital in Seoul, who were diagnosed as having AD between April 1995 and December 2005. Deaths were identified by the Statistics Korea database. The Kaplan-Meier method was used for survival analysis, and a Cox proportional hazard model was used to assess factors related to patient survival.

RESULTS

The overall median survival from the onset of first symptoms and from the time of diagnosis was 12.6 years (95% confidence interval 11.7-13.4) and 9.3 years (95% confidence interval 8.7-9.9), respectively. The age of onset, male gender, history of diabetes mellitus, lower Mini-Mental State Examination score, and higher Clinical Dementia Rating score were negatively associated with survival. There was a reversal of risk of AD between early-onset and later-onset AD, 9.1 years after onset.

CONCLUSIONS

The results of our study show a different pattern of survival compared to those studies carried out with western AD populations. Mortality risk of early-onset AD varied depending on the duration of follow-up.

Clinical staging of semantic dementia in an FDG-PET study using FTLD-CDR

BACKGROUND

The frontotemporal lobar degeneration-specific clinical dementia rating (FTLD-CDR), which was recently developed to measure frontotemporal dementia (FTD) severity, includes 2 items that assess language and behavior in addition to the 6 items of the conventional CDR.

METHODS

To investigate which of the 3 ratings, i.e. the global score of the CDR (GCDR), the behavioral domain score of the FTLD-CDR (BCDR), or the language domain score of the FTLD-CDR (LCDR), is most suitable for monitoring the progression of semantic dementia (SD), the number of hypometabolic voxels was calculated by comparing 28 SD patients in each stage of the 3 ratings with 63 age/sex-matched controls using voxel-based statistical parametric mapping.

RESULTS

The hypometabolic areas increased as a function of the LCDR score in SD patients. However, hypometabolic areas associated with the GCDR did not increase gradually as the stage increased. Furthermore, those associated with the BCDR showed the reverse pattern.

CONCLUSION

Our findings suggest that the severity and patterning of glucose hypometabolism measured by the LCDR correspond well with the natural course of SD reported in previous clinical and neuroimaging studies, whereas the BCDR and GCDR did not reflect disease progression in SD.

Changes in subcortical structures in early- versus late-onset Alzheimer's disease

Patients with early-onset Alzheimer's disease (EOAD) are reported to be different from those with late-onset Alzheimer's disease (LOAD) in terms of neuropsychological and neuroimaging findings. In this study, we aimed to compare the longitudinal volume changes of 6 subcortical structures (the amygdala, hippocampus, thalamus, putamen, globus pallidus, and caudate nucleus) between patients with EOAD and LOAD for 3 years. We prospectively recruited 36 patients with probable Alzheimer's disease (14 EOAD, 22 LOAD) and 14 normal control subjects. We analyzed the volume of subcortical structures using an automatic surface-based method. At baseline, there were no differences in the volumes of subcortical structures between patients with EOAD and LOAD. However, over 3 years of longitudinal follow-up, patients with EOAD showed more rapid volumetric decline in the caudate, putamen, and thalamus than patients with LOAD, which is consistent with neuropsychological results. Our findings suggested that the cognitive reserve theory might be applicable to explain different decline rates of the volumes of the basal ganglia and thalamus according to onset age.

The optimization of ELISA for methamphetamine determination: the effect of immunogen, tracer and antibody purification method on the sensitivity

To obtain more sensitive immunoassay for methamphetamine (MA) determination, the optimum condition of enzyme-linked immunosorbent assay (ELISA) was investigated in regard to immunogens, antibody purification methods and coating tracers. Activated MA, N-(4-aminobutyl)methamphetamine (4-ABMA), was conjugated with bovine serum albumin (BSA) or keyhole limpet hemocyanin (KLH) and used as immunogen. The antibodies were purified by protein G chromatography or various immunoaffinity chromatography-linked MA-protein ligands, such as MA-BSA, MA-KLH or MA-ovalbumin (OVA). Each purified antibody was characterized by means of sensitivity and cross-reactivity using the three MA-protein coating tracers, MA-BSA, MA-KLH and MA-OVA. The best sensitivity of each antibody was acquired with the MA-OVA tracer although the tracer concentration and the antibody titer level at optimum condition were varied. The antibody with high titer level did not always yield good sensitivity. At optimum condition, immunoaffinity chromatography-purified antibodies were better for sensitivity and for specificity than protein G-purified antibodies. The cross-reactivity of the purified antibodies seemed to be affected by immunogen structure and showed somewhat different patterns according to the immunoaffinity ligand utilized. These data show that the antibody purification method as well as choice of coating tracer and immunogen is essential for the sensitivity and specificity of EIA; the optimum condition for assay should be discovered using various methods and combinations.

A case of myelopathy, myopathy, peripheral neuropathy and subcortical grey matter degeneration associated with recessive compound heterozygous POLG1 mutations

This 54year old woman presented with symptoms of sensory ataxic neuropathy, with cerebellar features. She developed further weakness, visual disturbances with diplopia, dysarthria and dysphasia. After her death at 66years, she was found to have compound heterozygous mutations of POLG1 gene in muscle, and Southern blot showed low levels of multiple deletions of mitochondrial DNA. Neuropathological examination showed profound dorsal column and dorsal spinocerebellar tract degeneration, degeneration of dorsal root ganglia and Clarke's nucleus in spinal cord and severe predominantly sensory peripheral neuropathy. The brain showed severe neuronal loss and gliosis in substantia nigra, medial posterior thalamus and head of caudate. Excess numbers of COX-negative fibres and "ragged-red" fibres were found in five skeletal muscles sampled.

Neurobehavioral dysfunction in patients with subcortical vascular mild cognitive impairment and subcortical vascular dementia

Amnestic mild cognitive impairment (MCI) is considered to be a prodromal stage of Alzheimer's disease. Likewise, subcortical vascular MCI (svMCI) is considered as a prodromal stage of subcortical vascular dementia (SVaD). The objective of this study was to investigate neuropsychiatric features in patients with svMCI compared to healthy controls and patients with SVaD. We evaluated 31 patients with svMCI, 42 with SVaD, and 28 healthy controls who underwent neuropsychiatric assessments using the Neuropsychiatric Inventory (NPI) and the Frontal Behavioral Inventory (FBI). On both the NPI and FBI, SVaD patients had the most severe neuropsychiatric symptoms, followed by svMCI patients and then healthy controls, suggesting that svMCI might be a prodromal stage of SVaD in terms of neuropsychiatric abnormalities. When we compared the differences of mean scores between negative and positive symptoms in FBI, negative symptoms tended to be more predominant than positive symptoms in both svMCI and SVaD patients, but the tendency was stronger in SVaD patients than in svMCI patients. These results suggest that vascular cognitive impairment with small vessel disease would start with both negative and positive neuropsychiatric symptoms and progress to present more severe negative symptoms. These behavioral ratings may be useful for early detection of vascular cognitive impairment associated with small vessel disease.