Decreased emotion recognition and reduced focus on facial hallmarks in behavioral variant frontotemporal dementia compared to primary psychiatric disorders and controls.

BACKGROUND AND PURPOSE: Early diagnosis of behavioral variant frontotemporal dementia (bvFTD) is challenging due to symptomatic overlap with primary psychiatric disorders (PPD). As emotion recognition deficits are early and key features of bvFTD, the aim was to explore processes driving social cognition deficits that may aid in the differentiation between bvFTD and PPD. METHODS: The total sample (N = 51) included 18 patients with bvFTD, 11 patients with PPD (mood, autism spectrum and psychotic disorders) and 22 controls from the Alzheimer Center Amsterdam of the Amsterdam UMC. Emotion recognition was assessed with the Ekman 60 Faces test, during which eye tracking metrics were collected in the first 5 s a face was presented. Group differences in dwell time on the total image as well as the circumscribed eyes area and mouth area were analysed using ANOVA, with post hoc comparisons. RESULTS: Patients with bvFTD scored lowest, patients with PPD scored intermediate and controls scored highest on emotion recognition. During facial processing, patients with bvFTD spent less dwell time on the total image than controls (mean difference 11.3%, F(2, 48) = 6.095, p = 0.004; bvFTD-controls p = 0.001, 95% confidence interval [CI] -892.64, -239.70). Dwell time on the eyes area did not differ between diagnostic groups, whilst patients with bvFTD spent less dwell time on the mouth area than PPD patients (mean difference 10.7%; F(2, 48) = 3.423, p = 0.041; bvFTD-PPD p = 0.022, 95% CI -986.38, -79.47) and controls (mean difference 7.8%; bvFTD-controls p = 0.043, 95% CI -765.91, -12.76). CONCLUSIONS: In bvFTD, decreased emotion recognition may be related to reduced focus on facial hallmarks. These findings suggest a valuable role for biometrics in social cognition assessment and the differentiation between bvFTD and PPD.

Four subgroups based on tau levels in Alzheimer's disease observed in two independent cohorts.

BACKGROUND: As Alzheimer's disease (AD) pathology presents decades before dementia manifests, unbiased biomarker cut-points may more closely reflect presence of pathology than clinically defined cut-points. Currently, unbiased cerebrospinal fluid (CSF) tau cut-points are lacking. METHODS: We investigated CSF t-tau and p-tau cut-points across the clinical spectrum using Gaussian mixture modelling, in two independent cohorts (Amsterdam Dementia Cohort and ADNI). RESULTS: Individuals with normal cognition (NC) (total n = 1111), mild cognitive impairment (MCI) (total n = 1213) and Alzheimer's disease dementia (AD) (total n = 1524) were included. In both cohorts, four CSF t- and p-tau distributions and three corresponding cut-points were identified. Increasingly high tau subgroups were characterized by steeper MMSE decline and higher progression risk to AD (cohort/platform-dependent HR, t-tau 1.9-21.3; p-tau 2.2-9.5). LIMITATIONS: The number of subjects in some subgroups and subanalyses was small, especially in the highest tau subgroup and in tau PET analyses. CONCLUSIONS: In two independent cohorts, t-tau and p-tau levels showed four subgroups. Increasingly high tau subgroups were associated with faster clinical decline, suggesting our approach may aid in more precise prognoses.

Synaptic proteins in CSF as potential novel biomarkers for prognosis in prodromal Alzheimer's disease.

BACKGROUND: We investigated whether a panel of 12 potential novel biomarkers consisting of proteins involved in synapse functioning and immunity would be able to distinguish patients with Alzheimer's disease (AD) and patients with mild cognitive impairment (MCI) from control subjects. METHODS: We included 40 control subjects, 40 subjects with MCI, and 40 subjects with AD from the Amsterdam Dementia Cohort who were matched for age and sex (age 65 ± 5 years, 19 [48%] women). The mean follow-up of patients with MCI was 3 years. Two or three tryptic peptides per protein were analyzed in cerebrospinal fluid using parallel reaction monitoring mass spectrometry. Corresponding stable isotope-labeled peptides were added and used as reference peptides. Multilevel generalized estimating equations (GEEs) with peptides clustered per subject and per protein (as within-subject variables) were used to assess differences between diagnostic groups. To assess differential effects of individual proteins, we included the diagnosis × protein interaction in the model. Separate GEE analyses were performed to assess differences between stable patients and patients with progressive MCI (MCI-AD). RESULTS: There was a main effect for diagnosis (p < 0.01) and an interaction between diagnosis and protein (p < 0.01). Analysis stratified according to protein showed higher levels in patients with MCI for most proteins, especially in patients with MCI-AD. Chromogranin A, secretogranin II, neurexin 3, and neuropentraxin 1 showed the largest effect sizes; ß values ranged from 0.53 to 0.78 for patients with MCI versus control subjects or patients with AD, and from 0.67 to 0.98 for patients with MCI-AD versus patients with stable MCI. In contrast, neurosecretory protein VGF was lower in patients with AD than in patients with MCI (ß = -0.93 [SE 0.22]) and control subjects (ß = 0.46 [SE 0.19]). CONCLUSIONS: Our results suggest that several proteins involved in vesicular transport and synaptic stability are elevated in patients with MCI, especially in patients with MCI progressing to AD dementia. This may reflect early events in the AD pathophysiological cascade. These proteins may be valuable as disease stage or prognostic markers in an early symptomatic stage of the disease.

Nutrients required for phospholipid synthesis are lower in blood and cerebrospinal fluid in mild cognitive impairment and Alzheimer's disease dementia.

INTRODUCTION: Synaptic membrane formation depends on nutrients that fuel metabolic pathways for the synthesis of constituent phospholipids. Consequently, insufficient availability of such nutrients may restrict membrane formation and contribute to synaptic dysfunction in Alzheimer's disease (AD). We assessed whether blood and cerebrospinal fluid (CSF) concentrations of nutrients related to phospholipid synthesis differ among patients with AD, mild cognitive impairment (MCI), and control subjects. METHODS: Concentrations of uridine, choline, folate, homocysteine, and other related metabolites were analyzed in paired blood and CSF samples from subjects selected from the Amsterdam Dementia Cohort with AD (n = 150; age, 66 ± 7 years; 37% female), MCI (n = 148; age, 66 ± 8 years; 37% female), and control subjects (n = 148; age, 59 ± 8 years; 38% female). RESULTS: Age- and gender-adjusted analysis of variance revealed different concentrations of circulating uridine, choline, and folate and CSF uridine, folate, and homocysteine (all P < .05) among the three diagnostic groups. Post hoc pairwise comparison showed that subjects with AD had lower CSF uridine, plasma choline and higher CSF homocysteine concentrations, whereas subjects with MCI had lower plasma and CSF uridine, serum and CSF folate, and higher CSF homocysteine concentrations compared with control subjects (all P < .05), with differences ranging from -11 to +22%. DISCUSSION: AD and MCI patients have lower levels of nutrients involved in phospholipid synthesis. The current observations warrant exploration of the application of nutritional strategies in the early stages of AD.

Performance and complications of lumbar puncture in memory clinics: Results of the multicenter lumbar puncture feasibility study.

INTRODUCTION: Lumbar puncture (LP) is increasingly performed in memory clinics. We investigated patient-acceptance of LP, incidence of and risk factors for post-LP complications in memory clinic populations. METHODS: We prospectively enrolled 3868 patients (50% women, age 66 ± 11 years, mini mental state examination 25 ± 5) at 23 memory clinics. We used logistic regression analysis using generalized estimated equations to investigate risk factors for post-LP complications, such as typical postlumbar puncture headache (PLPH) and back pain. RESULTS: A total of 1065 patients (31%) reported post-LP complaints; 589 patients (17%) reported back pain, 649 (19%) headache, of which 296 (9%) reported typical PLPH. Only few patients needed medical intervention: 11 (0.3%) received a blood patch, 23 (0.7%) were hospitalized. The most important risk factor for PLPH was medical history of headache. An atraumatic needle and age >65 years were preventive. Gender, rest after LP, or volume of cerebrospinal fluid had no effect. DISCUSSIONS: The overall risk of complications is relatively low. If risk factors shown in this study are taken into account, LPs can be safely performed in memory clinics.

Matrix Metalloproteinases in Alzheimer's Disease and Concurrent Cerebral Microbleeds.

Matrix metalloproteinases (MMPs) are a family of enzymes able to degrade components of the extracellular matrix, which is important for normal blood-brain barrier function. Their function is regulated by tissue inhibitors of matrix metalloproteinases (TIMPs). We investigated whether MMPs and TIMPs in cerebrospinal fluid (CSF) and plasma were altered in Alzheimer's disease (AD) and vascular dementia (VaD), and whether this effect was modified by presence of cerebral micro-bleeds in AD patients. In addition, we assessed associations of MMPs and TIMPs with CSF amyloid-ß(1-42) (Aß42), tau, and tau phosphorylated at threonine-181 (p-tau). We measured MMP2, MMP9, and MMP10, and TIMP1 and TIMP2 in CSF and plasma of 52 AD patients, 26 matched controls, and 24 VaD patients. AD patients showed higher plasma MMP2 levels compared to VaD patients (p <  0.05), and higher CSF MMP10 levels compared to controls (p <  0.05). Microbleeds in AD were associated with lower CSF TIMP1, TIMP2 and MMP9 in a dose-response relation. In addition, CSF MMP2 was associated with p-tau (St.B 0.23, p <  0.05), and CSF MMP10 with tau (St.B 0.38, p <  0.001) and p-tau (St.B 0.40, p <  0.001). Our findings suggest involvement of MMP2 and MMP10 in AD pathology. Lower levels of TIMPs in AD patients with microbleeds suggest less MMP inhibition in patients with concurrent cerebral microbleeds, which may hypothetically lead to a more vulnerable blood-brain barrier in these patients.

Correcting for the Absence of a Gold Standard Improves Diagnostic Accuracy of Biomarkers in Alzheimer's Disease.

BACKGROUND: Studies investigating the diagnostic accuracy of biomarkers for Alzheimer's disease (AD) are typically performed using the clinical diagnosis or amyloid-ß positron emission tomography as the reference test. However, neither can be considered a gold standard or a perfect reference test for AD. Not accounting for errors in the reference test is known to cause bias in the diagnostic accuracy of biomarkers. OBJECTIVE: To determine the diagnostic accuracy of AD biomarkers while taking the imperfectness of the reference test into account. METHODS: To determine the diagnostic accuracy of AD biomarkers and taking the imperfectness of the reference test into account, we have developed a Bayesian method. This method establishes the biomarkers' true value in predicting the AD-pathology status by combining the reference test and the biomarker data with available information on the reliability of the reference test. The new methodology was applied to two clinical datasets to establish the joint accuracy of three cerebrospinal fluid biomarkers (amyloid-ß 1 - 42, Total tau, and P-tau181p) by including the clinical diagnosis as imperfect reference test into the analysis. RESULTS: The area under the receiver-operating-characteristics curve to discriminate between AD and controls, increases from 0.949 (with 95% credible interval [0.935,0.960]) to 0.990 ([0.985,0.995]) and from 0.870 ([0.817,0.912]) to 0.975 ([0.943,0.990]) for the cohorts, respectively. CONCLUSIONS: Use of the Bayesian methodology enables an improved estimate of the exact diagnostic value of AD biomarkers and overcomes the lack of a gold standard for AD. Using the new method will increase the diagnostic confidence for early stages of AD.

Diagnostic impact of CSF biomarkers for Alzheimer's disease in a tertiary memory clinic.

BACKGROUND: We aimed to assess the impact of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease on decision making and patient management in a tertiary memory clinic. METHODS: We included all patients, for 1 year, visiting the VUmc Alzheimer Center for cognitive screening. Neurologists completed questionnaires before and after CSF disclosure. We assessed the change of diagnosis, diagnostic confidence, and impact on patient management. RESULTS: A total of 438 patients (age 63 ± 8 years, 39% women) were included, of whom 351 (80%) underwent lumbar puncture. After the disclosure of CSF 23/351 diagnoses (7%) were changed. Diagnostic confidence increased from 84% to 89% (P < .001). There were consequences for management in 44/351 patients (13%) with CSF, and 13/87 patients (15%) because of unavailable CSF. There was no effect of age on these results. CONCLUSIONS: CSF biomarkers aid clinicians with decision making during diagnostic work-up of cognitive disorders. This study may be useful for developing guidelines for the implementation of CSF biomarkers in daily practice.

Cerebrospinal fluid levels of the synaptic protein neurogranin correlates with cognitive decline in prodromal Alzheimer's disease.

INTRODUCTION: Synaptic dysfunction is an early event in Alzheimer's disease (AD) pathogenesis and directly related to cognitive impairment. Consequently, synaptic biomarkers may be valuable tools for both early diagnosis and disease stage. Neurogranin (Ng) is a postsynaptic protein involved in memory consolidation. METHODS: We developed three monoclonal anti-Ng antibodies. Mass spectrometry and a novel enzyme-linked immunosorbent assay were used to analyze cerebrospinal fluid (CSF) Ng in three independent clinical cohorts including patients with AD dementia (n = 100 in total), mild cognitive impairment patients (MCI), (n = 40) and controls (n = 80 in total). RESULTS: We show in three independent clinical cohorts a marked increase in CSF Ng levels in AD dementia (P < .001 in all studies). In addition, high CSF Ng levels at the MCI stage predicted progression to dementia due to AD with a hazard ratio of 12.8 (95% confidence interval 1.6-103.0, P = .02). In amyloid-positive MCI patients, high CSF Ng correlated with a more rapid change in cognition during clinical follow-up (P = .03). DISCUSSION: These results suggest that CSF Ng is a novel AD biomarker that may be used to monitor synaptic degeneration, and correlates with the rate of cognitive decline in prodromal AD.

The cerebrospinal fluid "Alzheimer profile": easily said, but what does it mean?

BACKGROUND: We aimed to identify the most useful definition of the "cerebrospinal fluid Alzheimer profile," based on amyloid-ß1-42 (Aß42), total tau, and phosphorylated tau (p-tau), for diagnosis and prognosis of Alzheimer's disease (AD). METHODS: We constructed eight Alzheimer profiles with previously published combinations, including regression formulas and simple ratios. We compared their diagnostic accuracy and ability to predict dementia due to AD in 1385 patients from the Amsterdam Dementia Cohort. Results were validated in an independent cohort (n = 1442). RESULTS: Combinations outperformed individual biomarkers. Based on the sensitivity of the best performing regression formulas, cutoffs were chosen at 0.52 for the tau/Aß42 ratio and 0.08 for the p-tau/Aß42 ratio. Ratios performed similar to formulas (sensitivity, 91%-93%; specificity, 81%-84%). The same combinations best predicted cognitive decline in mild cognitive impairment patients. Validation confirmed these results, especially regarding the tau/Aß42 ratio. CONCLUSIONS: A tau/Aß42 ratio of >0.52 constitutes a robust cerebrospinal fluid Alzheimer profile. We recommend using this ratio to combine biomarkers.

Increase in cerebrospinal fluid F2-isoprostanes is related to cognitive decline in APOE ε4 carriers.

In this longitudinal study we investigated the effect of apolipoprotein E (APOE) genotype on the relation between cognitive decline and cerebrospinal fluid (CSF) F2-isoprostanes, the reference marker for oxidative stress. Twenty non-demented subjects, 58 mild cognitive impairment (MCI) patients, and 63 Alzheimer's disease (AD) patients with measurements of CSF F2-isoprostanes at two time points (with a mean interval of 2.0 ± 1.1 years) and known APOE genotype were included. Mean clinical follow-up time was 3.9 ± 2.4 years. For change in F2-isoprostanes over time and associations with Mini-Mental State Examination scores, age- and gender-adjusted linear mixed models were used. Analyses were done for APOE ε4 carriers and non-carriers separately. In APOE ε4 carriers, annual change in F2-isoprostane levels appeared larger than in APOE ε4 non-carriers (ß[SE] 2.5[0.5], p < 0.001 versus 1.8[0.5], p < 0.01). In addition, increase in F2-isoprostanes was associated with further cognitive decline in APOE ε4 carriers (p < 0.05), but not in non-carriers (p = 0.28). Our results reiterate the importance of oxidative stress in neurodegeneration, especially in APOE ε4 carrying patients. Future studies should focus on the possibility of increased vulnerability to oxidative damage in APOE ε4 carriers.