Cortical phase changes measured using 7-T MRI in subjects with subjective cognitive impairment, and their association with cognitive function.

Studies have suggested that, in subjects with subjective cognitive impairment (SCI), Alzheimer's disease (AD)-like changes may occur in the brain. Recently, an in vivo study has indicated the potential of ultra-high-field MRI to visualize amyloid-beta (Aß)-associated changes in the cortex in patients with AD, manifested by a phase shift on T2 *-weighted MRI scans. The main aim of this study was to investigate whether cortical phase shifts on T2 *-weighted images at 7 T in subjects with SCI can be detected, possibly implicating the deposition of Aß plaques and associated iron. Cognitive tests and T2 *-weighted scans using a 7-T MRI system were performed in 28 patients with AD, 18 subjects with SCI and 27 healthy controls (HCs). Cortical phase shifts were measured. Univariate general linear modeling and linear regression analysis were used to assess the association between diagnosis and cortical phase shift, and between cortical phase shift and the different neuropsychological tests, adjusted for age and gender. The phase shift (mean, 1.19; range, 1.00-1.35) of the entire cortex in AD was higher than in both SCI (mean, 0.85; range, 0.73-0.99; p < 0.001) and HC (mean, 0.94; range, 0.79-1.10; p < 0.001). No AD-like changes, e.g. increased cortical phase shifts, were found in subjects with SCI compared with HCs. In SCI, a significant association was found between memory function (Wechsler Memory Scale, WMS) and cortical phase shift (ß = -0.544, p = 0.007). The major finding of this study is that, in subjects with SCI, an increased cortical phase shift measured at high field is associated with a poorer memory performance, although, as a group, subjects with SCI do not show an increased phase shift compared with HCs. This increased cortical phase shift related to memory performance may contribute to the understanding of SCI as it is still unclear whether SCI is a sign of pre-clinical AD. Copyright © 2014 John Wiley & Sons, Ltd.

Microbleeds, Mortality, and Stroke in Alzheimer Disease: The MISTRAL Study.

IMPORTANCE: Microbleeds are more prevalent in patients with Alzheimer disease (AD) compared with the general elderly population. In addition, microbleeds have been found to predict mortality in AD. OBJECTIVE: To investigate whether microbleeds in AD increase the risk for mortality, stroke (including intracerebral hemorrhage), and cardiovascular events. DESIGN, SETTING AND PARTICIPANTS: The MISTRAL (do MIcrobleeds predict STRoke in ALzheimer's disease) Study is a longitudinal cohort study within the memory clinic-based Amsterdam Dementia Cohort. We selected all patients with AD with a baseline visit between January 2, 2002, and December 16, 2009, and microbleeds (n = 111) and matched those (1:2) for age, sex, and magnetic resonance imaging scanner to 222 patients with AD without microbleeds. After a minimal follow-up of 3 years, information on all-cause mortality, stroke-related mortality, and cardiovascular mortality was obtained between November 1, 2012, and May 1, 2014. In addition, we obtained information on the occurrence of incident stroke or transient ischemic attack, cardiovascular events, and nursing home admittance. MAIN OUTCOMES AND MEASURES: Stroke-related mortality, incident stroke, and intracerebral hemorrhage. RESULTS: Patients had a mean (SD) age of 71.2 (7.8) years and 127 (42%) were female. Compared with having no microbleeds, microbleeds in lobar locations were associated with an increased risk for stroke-related mortality (hazard ratio [HR], 33.9; 95% CI, 2.5-461.7), whereas nonlobar microbleeds were associated with an increased risk for cardiovascular mortality (HR, 12.0; 95% CI, 3.2-44.7). In addition, lobar microbleeds were associated with an increased risk for incident stroke (HR, 3.8; 95% CI, 1.5-10.1) and nonlobar microbleeds with an increased risk for cardiovascular events (HR, 6.2; 95% CI, 1.5-25.0). Even higher risks for incident stroke and cardiovascular events were found in patients using antithrombotic medication. All 5 patients with an intracerebral hemorrhage had lobar microbleeds at baseline; 4 of them used antithrombotics. CONCLUSIONS AND RELEVANCE: In patients with AD, the presence of nonlobar microbleeds was associated with an increased risk for cardiovascular events and cardiovascular mortality. Patients with lobar microbleeds had an increased risk for stroke and stroke-related mortality, indicating that these patients should be treated with the utmost care.

7T T2*-weighted magnetic resonance imaging reveals cortical phase differences between early- and late-onset Alzheimer's disease.

The aim of this study is to explore regional iron-related differences in the cerebral cortex, indicative of Alzheimer's disease pathology, between early- and late-onset Alzheimer's disease (EOAD, LOAD, respectively) patients using 7T magnetic resonance phase images. High-resolution T2(∗)-weighted scans were acquired in 12 EOAD patients and 17 LOAD patients with mild to moderate disease and 27 healthy elderly control subjects. Lobar peak-to-peak phase shifts and regional mean phase contrasts were computed. An increased peak-to-peak phase shift was found for all lobar regions in EOAD patients compared with LOAD patients (p < 0.05). Regional mean phase contrast in EOAD patients was higher than in LOAD patients in the superior medial and middle frontal gyrus, anterior and middle cingulate gyrus, postcentral gyrus, superior and inferior parietal gyrus, and precuneus (p ≤ 0.042). These data suggest that EOAD patients have an increased iron accumulation, possibly related to an increased amyloid deposition, in specific cortical regions as compared with LOAD patients.

Associations between cerebral small-vessel disease and Alzheimer disease pathology as measured by cerebrospinal fluid biomarkers.

IMPORTANCE: It remains unclear if and how associations between cerebral small-vessel disease and Alzheimer disease (AD) pathology lead to cognitive decline and dementia. OBJECTIVE: To determine associations between small-vessel disease and AD pathology. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study from January 2002 to December 2012 using the memory clinic-based Amsterdam Dementia Cohort. The study included 914 consecutive patients with available cerebrospinal fluid (CSF) and magnetic resonance imaging; 547 were patients diagnosed as having AD (54% female, mean [SD], 67 [8]; Mini-Mental State Examination score, mean [SD], 21 [5]), 30 were patients diagnosed as having vascular dementia (37% female, mean [SD], 76 [9]; Mini-Mental State Examination score, mean [SD], 24 [4]), and 337 were control participants with subjective memory complaints (42% female, mean [SD], 59 [59]; Mini-Mental State Examination score, mean [SD], 28 [2]). Linear regressions were performed with CSF biomarkers (log transformed) as dependent variables and magnetic resonance imaging measures (dichotomized) as independent, adjusted for sex, age, mediotemporal lobe atrophy, and diagnosis. An interaction term for diagnosis by magnetic resonance imaging measures was used for estimates per diagnostic group. MAIN OUTCOMES AND MEASURES: We examined the associations of magnetic resonance imaging white matter hyperintensities (WMH), lacunes, microbleeds with CSF ß-amyloid 42 (Aß42), total tau, and tau phosphorylated at threonine 181 (P-tau181) as well as for a subset of apolipoprotein E (APOE) ε4 carriers and noncarriers. RESULTS: Microbleed presence was associated with lower CSF Aß42 in AD and vascular dementia (standardized beta = -0.09, P = .003; standardized beta = -0.30, P = .01), and higher CSF tau in controls (standardized beta = 0.10, P = .03). There were no effects for P-tau181. The presence of WMH was associated with lower Aß42 in control participants and patients with vascular dementia (standardized beta = -0.18, P = .002; standardized beta = -0.32, P = .02) but not in patients with AD. There were no effects for tau or P-tau181. The presence of lacunes was associated with higher Aß42 in vascular dementia (standardized beta = 0.17, P = .07) and lower tau in AD (standardized beta = -0.07, P = .05) but there were no effects for Aß42 or P-tau181. Stratification for apolipoprotein E genotype revealed that these effects were mostly attributable to ε4 carriers. CONCLUSIONS AND RELEVANCE: Deposition of amyloid appears aggravated in patients with cerebral small-vessel disease, especially in apolipoprotein E ε4 carriers, providing evidence for pathophysiological synergy between these 3 biological factors.

Prevalence of cortical superficial siderosis in a memory clinic population.

OBJECTIVE: To determine prevalence, topography, and severity of cortical superficial siderosis (SS), a recently recognized manifestation of cerebral amyloid angiopathy, and its possible association with Alzheimer disease (AD) in a memory clinic patient cohort. METHODS: We included 809 patients (56% men, aged 66 ± 10 years) from the Amsterdam Dementia Cohort between November 2010 and November 2012 scanned on a 3-tesla MRI system. We analyzed prevalence and topography of cortical SS according to demographic, clinical, and MRI data. Agreement for SS detection between 2 neuroradiologists was calculated by using Cohen κ. RESULTS: Agreement for detection of SS was excellent (unweighted κ of 0.81). In 17 patients (2.1%), cortical SS was found without a known cause. The prevalence of idiopathic SS differed according to diagnostic groups (p < 0.001): nearly 5% (95% confidence interval [CI] 2.8%-8.2%) in patients with AD (n = 168) vs 2% (95% CI 0.7%-6.0%) in patients with mild cognitive impairment (n = 143) and 2.5% (95% CI 0.7%-8.7%) in other types of dementia (n = 80). By contrast, SS was not found in patients with subjective complaints (n = 168) or in those with other disorders (n = 157). Presence of SS was associated with APOE ε4, microbleeds, and white matter hyperintensities (all p < 0.05) independent of diagnosis. CONCLUSION: The prevalence of cortical SS in a memory clinic setting is higher than reported in the general population but lower than reported in cerebral amyloid angiopathy. The relatively high prevalence of SS in AD suggests that SS is a relevant radiologic manifestation of amyloid pathology in AD. Presence of SS does not seem to predict severity of AD. Further longitudinal research is needed to investigate clinical relevance.

Increased number of microinfarcts in Alzheimer disease at 7-T MR imaging.

PURPOSE: To assess the prevalence and number of cortical microinfarcts in patients with Alzheimer disease (AD) by using a 7-T magnetic resonance (MR) imaging system, to assess the independent association of cortical microinfarcts with cognitive dysfunction, and to investigate potential confounding effects of the coexisting presence of cerebral amyloid angiopathy (CAA). MATERIALS AND METHODS: The local institutional review board approved this study. In all cases, informed consent was obtained. High-spatial-resolution fluid-attenuated inversion recovery and T2*-weighted images were acquired in 14 AD patients and 18 control subjects to assess the presence of microinfarcts and microbleeds. Presence of CAA was assessed according to the Boston criteria. Image analysis was performed independently by two reviewers. Mann-Whitney U test was performed to assess differences in number of microinfarcts between groups. Negative binomial regression models were used to assess the association between diagnosis of AD and diagnosis of CAA and number of microinfarcts, between diagnosis of AD and number of microbleeds and number of microinfarcts, and between cognitive function and number of microinfarcts, all corrected for age and sex. RESULTS: Interobserver agreement was excellent for detecting microinfarcts (κ = 0.91) (P < .001). Patients with AD demonstrated higher number (P = .005) of microinfarcts (mean, 7.2) compared with control subjects (mean, 1.8). Negative binomial regression models showed an independent association between AD and number of microinfarcts (P = .006) and a trend for CAA and microinfarcts (P = .052). A negative correlation was found between cognitive function and the number of microinfarcts (P = .009). CONCLUSION: Patients with AD show more microinfarcts than do control subjects, the number of microinfarcts correlates with global cognitive performance, and the presence of microinfarcts was mainly AD rather than CAA related.

Specific risk factors for microbleeds and white matter hyperintensities in Alzheimer's disease.

We investigated whether microbleeds and white matter hyperintensities (WMH) in Alzheimer's disease (AD) associate more with conventional vascular risk factors or with risk factors that reflect amyloid burden. A total of 371 patients with probable AD were included. WMH (Fazekas 2 or 3) were present in 107 (29%) patients and microbleeds were seen in 98 (26%). Patients with both microbleeds and WMH were older and presented more frequently with lacunes and multiple microbleeds than patients with microbleeds in isolation (all p < 0.05). Using multivariate regression models, we found that WMH presence showed independent associations with age, hypertension, current smoking, and lacune presence. Microbleeds were independently associated with male gender, higher blood pressure, lower cerebrospinal fluid Aß42, and apolipoprotein E ε4 homozygosity. Separate analyses for microbleeds according to their location showed that these associations were driven by microbleeds in lobar locations. Our results suggest that, unlike WMH, microbleeds in AD are particularly associated with additional amyloid burden, and as such, may relate to cerebral amyloid angiopathy.

Microbleeds do not affect rate of cognitive decline in Alzheimer disease.

OBJECTIVE: To investigate the relationship between brain microbleeds (MBs) and the rate of cognitive decline in Alzheimer disease (AD). METHODS: In this cohort study, we studied 221 patients with AD with available baseline MRI scans (1.0 or 1.5 T) and at least 2 Mini-Mental State Examinations (MMSE) scores obtained more than 1 year apart from our memory clinic. Mean ± SD follow-up time was 3 ± 1 years, and patients had a median of 4 MMSE scores (range 2-17). We used linear mixed models with sex and age as covariates to investigate whether MBs influenced the rate of cognitive decline. RESULTS: Mean age was 68 ± 9 years, 109 (49%) patients were female, and the baseline MMSE score was 22 ± 4. There were 39 patients (18%) with MBs (median 2, range 1-27) and 182 without. Linear mixed models showed that overall patients declined 2 MMSE points per year. We found no association of the presence of MBs with baseline MMSE or change in MMSE. Adjustment for atrophy, white matter hyperintensities, lacunes, and vascular risk factors did not change the results nor did stratification for MB location, APOE ε4 carriership, or age at onset (≤65 years vs >65 years). Repeating the analyses with number of MBs as predictor rendered similar results. CONCLUSION: MBs did not influence the rate of cognitive decline in patients with AD. The formerly reported increased risk of mortality in patients with MBs seems not to be attributable to a steeper rate of decline per se but might be due to vascular events, including (hemorrhagic) stroke.

No evidence for additional blood-brain barrier P-glycoprotein dysfunction in Alzheimer's disease patients with microbleeds.

Decreased blood-brain barrier P-glycoprotein (Pgp) function has been shown in Alzheimer's disease (AD) patients using positron emission tomography (PET) with the radiotracer (R)-[(11)C]verapamil. Decreased Pgp function has also been hypothesized to promote cerebral amyloid angiopathy (CAA) development. Here, we used PET and (R)-[(11)C]verapamil to assess Pgp function in eighteen AD patients, of which six had microbleeds (MBs), presumably reflecting underlying CAA. No differences were found in binding potential and nonspecific volume of distribution of (R)-[(11)C]verapamil between patient groups. These results provide no evidence for additional Pgp dysfunction in AD patients with MBs.

Microbleeds relate to altered amyloid-ß metabolism in Alzheimer's disease.

Cerebral microbleeds (MBs) may relate to amyloid in dementia. We selected 26 probable Alzheimer's disease (AD) patients with MBs, 26 age- and sex-matched AD patients without MBs, 11 vascular dementia (VaD) patients, and 22 patients with subjective complaints. We measured amyloid beta 1-42 (Aß42) and 1-40 (Aß40) in cerebrospinal fluid (CSF) and plasma, and blood-brain barrier (BBB) function using albumin ratios. CSF Aß42 was lowest in AD with MBs, whereas Aß40 was selectively decreased in VaD. In plasma, amyloid-beta was nonsignificantly elevated in VaD compared with controls. Higher albumin ratios in VaD suggested blood-brain barrier dysfunction. A MB pattern suggestive of cerebral amyloid angiopathy (CAA) related to lower CSF Aß42, while a non-cerebral amyloid angiopathy specific MB distribution related to higher plasma Aß40. Amyloid-beta is differentially implicated in AD with MBs and VaD. MB distribution related to different amyloid profiles, supporting distinct etiologies. Our results suggest that Aß42 is retained in cerebrovasculature of AD patients with MBs, while in contrast, VaD patients may possibly drain amyloid.

Clinical relevance of improved microbleed detection by susceptibility-weighted magnetic resonance imaging.

BACKGROUND AND PURPOSE: Susceptibility-weighted imaging (SWI) has been shown to be more sensitive in detecting cerebral microbleeds (MBs) than is conventional T2*-weighted gradient-recalled echo imaging (GRE). However, the clinical relevance of this improved detection in terms of associations with clinical measures and risk factors is unclear. We sought to determine whether associations of MBs with clinical characteristics, risk factors, white-matter hyperintensities, and lacunes were different on GRE versus SWI in memory clinic patients. METHODS: One hundred forty-one patients presenting at our memory clinic were included and underwent clinical evaluation and a magnetic resonance imaging protocol including both GRE and SWI. Images were analyzed for numbers and locations of MBs and white-matter hyperintensities. In a subset of patients, apolipoprotein E status was determined. Negative binomial regression was used to assess clinical and radiologic associations with MB number. RESULTS: MB prevalence was 23% on GRE and 40% on SWI. A total of 219 and 284 MBs were detected on GRE and SWI, respectively. Within groups with MBs, the median MB count was 1 (range, 1 to 144) on GRE and 2 (range, 1 to 129) on SWI (P<0.001). The increase in the number of MBs on SWI was equally distributed among brain regions. Strengths of the associations with age, sex, white-matter hyperintensities, and presence of lacunes with higher MB numbers were comparable for GRE and SWI (all P<0.05); no differential independent associations were detected. CONCLUSIONS: SWI detected more MBs in more patients, irrespective of MB location. However, this enhanced detection had no improved clinical relevance in terms of associations with vascular risk factors or radiologic markers of small-vessel disease.

Patients with Alzheimer disease with multiple microbleeds: relation with cerebrospinal fluid biomarkers and cognition.

BACKGROUND AND PURPOSE: Microbleeds (MBs) are commonly observed in Alzheimer disease. A minority of patients has multiple MBs. We aimed to investigate associations of multiple MBs in Alzheimer disease with clinical and MRI characteristics and cerebrospinal fluid biomarkers. METHODS: Patients with Alzheimer disease with multiple (>or=8) MBs on T2*-weighted MRI were matched for age, sex, and field strength with patients with Alzheimer disease without MBs on a 1:2 basis. We included 21 patients with multiple MBs (73+/-7 years, 33% female) and 42 patients without MBs (72+/-7 years, 38% female). Mini-Mental State Examination was used to assess dementia severity. Cognitive functions were assessed using neuropsychological tests. Medial temporal lobe atrophy (0 to 4), global cortical atrophy (0 to 3), and white matter hyperintensities (0 to 30) were assessed using visual rating scales. In a subset, apolipoprotein E genotype and cerebrospinal fluid amyloid beta 1-42, total tau and tau phosphorylated at threonine 181 were determined. RESULTS: Patients with multiple MBs performed worse on Mini-Mental State Examination (multiple MB: 17+/-7; no MB: 22+/-4, P<0.05) despite similar disease duration. Atrophy was not related to presence of MBs, but patients with multiple MBs had more white matter hyperintensities (multiple MB: 8.8+/-4.8; no MB: 3.2+/-3.6, P<0.05). Adjusted for age, sex, white matter hyperintensities, and medial temporal lobe atrophy, the multiple MB group additionally performed worse on Visual Association Test object naming and animal fluency. Patients with multiple MBs had lower cerebrospinal fluid amyloid beta 1-42 levels (307+/-61) than patients without MBs (505+/-201, P<0.05). Adjusted for the same covariates, total tau, and tau phosphorylated at threonine 181 were higher in the multiple MB group. CONCLUSIONS: Microbleeds are associated with the clinical manifestation and biochemical hallmarks of Alzheimer disease, suggesting possible involvement of MBs in the pathogenesis of Alzheimer disease.