Validation of biomarkers in subcortical ischaemic vascular disease of the Binswanger type: approach to targeted treatment trials.

OBJECTIVES: Vascular cognitive impairment (VCI) is a heterogeneous group of cerebrovascular diseases secondary to large and small vessel disease. We hypothesised that biomarkers obtained early in the disease could identify a homogeneous subpopulation with small vessel disease. METHODS: We obtained disease markers in 62 patients with VCI that included neurological findings, neuropsychological tests, multimodal MR and cerebrospinal fluid measurements of albumin ratio, matrix metalloproteinases (MMPs), amyloid-ß1-42 and phosphorylated-τ181. Proton MR spectroscopic imaging showed ischaemic white matter and permeability of the blood-brain barrier (BBB) was measured with dynamic contrast-enhanced MRI. We constructed a 10-point Binswanger disease score (BDS) with subjective and objective disease markers. In addition, an objective set of biomarkers was used for an exploratory factor analysis (EFA) to select patients with BD. Patients were followed for an average of 2 years to obtain clinical consensus diagnoses. RESULTS: An initial BDS of 6 or greater was significantly correlated with a final diagnosis of BD (p<0.05; area under the curve (AUC)=0.79). EFA reduced nine objective biomarkers to four factors. The most predictive of BD was the factor containing the inflammatory biomarkers of increased BBB permeability, elevated albumin index and reduced MMP-2 index (factor 2; AUC=0.78). Both measures independently predicted a diagnosis of BD, and combining them improved the diagnostic accuracy. CONCLUSIONS: Biomarkers predicted the diagnosis of the BD type of subcortical ischaemic vascular disease. Using pathophysiological biomarkers to select homogeneous groups of patients needs to be tested in targeted treatment trials.

NFL and GFAP in (pre)symptomatic RVCL-S carriers: a monogenic cerebral small vessel disease.

BACKGROUND: Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) have emerged as biomarkers for cerebral small vessel disease (SVD). We investigated their role in a hereditary SVD model, retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S). METHODS: NfL and GFAP levels of 17 pre-symptomatic, 22 symptomatic RVCL-S mutation carriers and 69 controls were measured using a Simoa assay. We assessed the association of serum and cerebrospinal fluid (CSF) levels of NfL and GFAP with RVCL-S symptomatology and neuropsychological functioning. RESULTS: Serum and CSF NfL levels were higher in symptomatic RVCL-S compared to controls ≥ 45 years (33.5 pg/mL vs. 9.2 pg/mL, p < 0.01; 8.5*102 pg/mL vs. 3.9*102 pg/mL, p < 0.01, respectively). Serum NfL levels were higher in symptomatic RVCL-S than pre-symptomatic carriers (33.5 pg/mL vs. 5.9 pg/mL, p = 0.02). Pre-symptomatic RVCL-S carriers had increased CSF NfL levels compared to controls < 45 years (5.2*102 pg/mL vs. 1.9*102 pg/mL, p < 0.01). No differences were found in GFAP levels across groups, but in RVCL-S carriers higher serum levels of both NfL and GFAP were linked to poorer global cognitive functioning (ß[95%CI] = - 2.86 [- 5.58 to - 0.13], p = 0.04 and ß[95%CI] = - 6.85 [- 11.54 to - 2.15], p = 0.01, respectively) and prolonged psychomotor test times (ß[95%CI] = 6.71 [0.78-12.65], p = 0.03 and ß[95%CI] = 13.84 [3.09-24.60], p = 0.01). DISCUSSION: Higher levels of serum NfL and GFAP are associated with worse cognitive functioning in RVCL-S carriers and may serve as marker for disease progression. CSF NfL levels may serve as early marker as pre-symptomatic RVCL-S patients already show differences compared to young controls.

Association of Enlarged Perivascular Spaces and Measures of Small Vessel and Alzheimer Disease.

OBJECTIVE: To investigate the relationship between enlarged perivascular spaces (EPVS) and measures of Alzheimer disease (AD), small vessel disease (SVD), cognition, vascular risk factors, and neuroinflammation, we tested associations between EPVS and different relevant neuroimaging, biochemical, and cognitive variables in 778 study participants. METHODS: Four hundred ninety-nine cognitively unimpaired (CU) individuals, 240 patients with mild cognitive impairment, and 39 patients with AD from the Swedish Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study were included. EPVS with diameter >1 mm in centrum semiovale (CSO), basal ganglia (BG), and hippocampus (HP); hippocampal volume; white matter lesions (WML); and other SVD markers were determined from MRI. CSF levels of ß-amyloid42 (Aß42), phosphorylated tau, total tau, and neuroinflammatory markers; amyloid accumulation determined with [18F]-flutemetamol PET; and vascular risk factors and results from cognitive tests were determined and collected. RESULTS: EPVS in CSO, BG, and HP were associated with WML volume and Fazekas score in individuals without dementia. No associations were found between EPVS and CSF Aß42, total tau and phosphorylated tau, neuroinflammatory markers, vascular risk factors, and cognitive tests. EPVS in HP were associated with hippocampal atrophy. In a matched group of individuals with AD and CU, EPVS in HP were associated with AD diagnosis. CONCLUSIONS: EPVS are related to SVD, also in early disease stages, but the lack of correlation with cognition suggests that their importance is limited. Our data do not support a role for EPVS in early AD pathogenesis.

Cerebrospinal Fluid Metals and the Association with Cerebral Small Vessel Disease.

BACKGROUND: Brain metal homeostasis is essential for brain health, and deregulation can result in oxidative stress on the brain parenchyma. OBJECTIVE: Our objective in this study was to focus on two hemorrhagic MRI manifestations of small vessel disease [cerebral microbleeds (CMBs) and cortical superficial siderosis (cSS)] and associations with cerebrospinal fluid (CSF) iron levels. In addition, we aimed to analyze CSF biomarkers for dementia and associations with CSF metal levels. METHODS: This is a cross-sectional study of 196 patients who underwent memory clinic investigation, including brain MRI. CSF was collected and analyzed for metals, amyloid-ß (Aß) 42, total tau (T-tau), and phosphorylated tau (P-tau), and CSF/serum albumin ratios. Statistical analyses were performed using generalized linear models. RESULTS: No significant difference was found between CSF metal levels across diagnostic groups. Higher iron and copper levels were associated with higher CSF levels of Aß42, T-tau, P-tau, and CSF/serum albumin ratios (p < 0.05). Zinc was associated with higher CSF/serum albumin ratios. There was no significant association between CMBs or cSS and CSF iron levels. An increase in CSF iron with the number of CMBs was seen in APOEɛ4 carriers. CONCLUSION: CSF iron levels are elevated with cerebral microbleeds in APOEɛ4 carriers, with no other association seen with hemorrhagic markers of small vessel disease. The association of elevated CSF iron and copper with tau could represent findings of increased neurodegeneration in these patients.

[The role of arterial, venous blood and cerebrospinal fluid flow disturbances in forming cognitive impairment types in age-related cerebral microangiophathy]. / Rol' narushenii arterial'nogo, venoznogo krovotoka i likvorotoka v formirovanii kognitivnykh rasstroistv pri vozrastzavisimoi tserebral'noi mikroangiopatii.

BACKGROUND: Age-related cerebral microangiopathy (small vessel disease, SVD) is the main cause of vascular and mixed cognitive impairment (CI) with a complex neuropsychological profile. AIM: To investigate the role of arterial and venous blood flow and cerebrospinal fluid (CSF) flow, as well as their interrelation, in the forming of CI types in patients with SVD. MATERIAL AND METHODS: Fifty patients (31 f., mean age 61.2±6,2) with SVD (STRIVE, 2013), including 37 with mild CI and 13 with dementia, were examined. A type of CI was determined based on combination of standard deviations from normal results on memory and executive function tests: isolated dysexecutive (13) and predominantly dysexecutive (6), predominantly amnestic (12), mixed, equal impairment of EF and memory, (19). In the statistical analysis, groups of the isolated and predominantly dysexecutive types were merged according to the dominance of deviations in the EF into the dysexecutive type of CI (19). Phase contrast MRI (PhC-MRI) was used to assess characteristics of arterial and venous blood flow and CSF flow on different levels. Indexes of pulse and intracranial compliance and surface of the cerebral aqueduct were calculated. RESULTS: Patients with all CI types had a CSF flow systolic peak delay at the cervical level. Mixed and dysexecutive CI types as compared with predominantly amnestic type and control were defined by blood flow reduction in the sinus rectus, and mixed type by the additional decrease in its pulse wave width, blood flow reduction in an internal jugular artery and maximal blood flow velocity in the inner carotid artery, the increase in the intracranial compliance index and surface of the cerebral aqueduct. CONCLUSION: The neuropsychological CI type in SVD is defined by features of pathophysiological mechanisms conditioned on differences in blood flow and CSF flow impairment severity and formed hydrodynamic interaction between them. Differential features of CI types in SVD defined by PhC-MRI might become important predictive indicators of potential interaction between SVD and degeneration, improve understanding of risk factors, pathogenesis, prevention and treatment of age-related brain damage.

The contribution of small vessel disease to subtypes of Alzheimer's disease: a study on cerebrospinal fluid and imaging biomarkers.

We investigated whether subtypes of Alzheimer's disease (AD), that is, typical, limbic-predominant, hippocampal-sparing, and minimal atrophy AD, had a specific signature of small vessel disease and neurodegeneration. Four hundred twenty-three clinically diagnosed AD patients were included (161 typical, 121 limbic-predominant, 70 hippocampal-sparing, 71 minimal atrophy). One hundred fifty-six fulfilled a biomarkers-based AD diagnosis. White matter hyperintensities and cerebral microbleeds (CMB) had the highest prevalence in limbic-predominant AD, and the lowest prevalence in minimal atrophy AD. CMB existed evenly in lobar and deep brain areas in limbic-predominant, typical, and hippocampal-sparing AD. In minimal atrophy AD, CMB were mainly located in brain lobar areas. Perivascular spaces in the centrum semiovale were more prevalent in typical AD. Small vessel disease contributed to the prediction of Mini-Mental State Examination. Minimal atrophy AD showed highly pathological levels of cerebrospinal fluid Aß1-42, total tau, and phosphorylated tau, in the absence of overt brain atrophy. Cerebral amyloid angiopathy seems to have a stronger contribution to hippocampal-sparing and minimal atrophy AD, whereas hypertensive arteriopathy may have a stronger contribution to typical and limbic-predominant AD.

White Matter Hyperintensities Potentiate Hippocampal Volume Reduction in Non-Demented Older Individuals with Abnormal Amyloid-ß.

Cerebral small vessel disease (cSVD) and amyloid-ß (Aß) deposition often co-exist in (prodromal) dementia, and both types of pathology have been associated with neurodegeneration. We examined whether cSVD and Aß have independent or interactive effects on hippocampal volume (HV) in a memory clinic population. We included 87 individuals with clinical diagnoses of Alzheimer's disease (AD) (n = 24), mild cognitive impairment (MCI) (n = 26), and subjective cognitive complaints (SCC) (n = 37). cSVD magnetic resonance imaging markers included white matter hyperintensity (WMH) volume, lacunar infarct presence, and microbleed presence. Aß pathology was assessed as cerebrospinal fluid-derived Aß1 - 42 levels and dichotomized into normal or abnormal, and HV was determined by manual volumetric measurements. A linear hierarchical regression approach was applied for the detection of additive or interaction effects between cSVD and Aß on HV in the total participant group (n = 87) and in the non-demented group (including SCC and MCI individuals only, n = 63). The results revealed that abnormal Aß and lacunar infarct presence were independently associated with lower HV in the non-demented individuals. Interestingly, Aß and WMH pathology interacted in the non-demented individuals, such that WMH had a negative effect on HV in individuals with abnormal CSF Aß42 levels, but not in individuals with normal CSF Aß42 levels. These associations were not present when individuals with AD were included in the analyses. Our observations suggest that relatively early on in the disease process older individuals with abnormal Aß levels are at an increased risk of accelerated disease progression when concomitant cSVD is present.

Topography and Determinants of Magnetic Resonance Imaging (MRI)-Visible Perivascular Spaces in a Large Memory Clinic Cohort.

BACKGROUND: Magnetic resonance imaging-visible perivascular spaces (PVS) are related to interstitial fluid clearance pathways (including amyloid-ß) in the brain and are suggested to be a marker of cerebral small vessel disease. We investigated the role, topography, and possible implications of PVS in cognitive impairment. METHODS AND RESULTS: A total of 1504 patients undergoing memory clinic investigation and an associated brain magnetic resonance imaging scan were included in this cross-sectional study. Magnetic resonance images were assessed for markers of small vessel disease. Additionally, 1039 patients had cerebrospinal fluid analysis of amyloid-ß 42, total tau (T-tau), and phosphorylated tau (P-tau); 520 patients had apoE genotyping done. Results were analyzed with generalized linear models. A total of 289 (19%; 95% confidence interval, 17-21) had a high-grade PVS in the centrum semiovale (CSO) and 65 (4%; 95% confidence interval: 3%-5%) in the basal ganglia (BG). Centrum semiovale- and BG-PVS were both associated with high age (P<0.001), hypertension (P<0.001), probable cerebral amyloid angiopathy (P<0.05), moderate-to-severe white matter hyperintensities (P<0.001), cortical superficial siderosis (P<0.001), cerebral microbleeds (P<0.001), and PVS. centrum semiovale-PVS was separately associated with strictly lobar cerebral microbleeds (P=0.057). BG-PVS was associated with strictly deep cerebral microbleeds (P<0.001), lacunes (P<0.001), and vascular dementia (P=0.04). BG-PVS showed a tendency to be associated with high cerebrospinal fluid tau (B=0.002, P=0.04) in the whole cohort and in Alzheimer's disease (B=0.005; P=0.02). No other associations with cerebrospinal fluid or the apoE e4 allele was observed. CONCLUSIONS: Centrum semiovale-PVS and BG-PVS have different underlying etiology, being associated with cerebral amyloid angiopathy and hypertensive vasculopathy, respectively, although a significant overlap between these pathologies is likely to exist.

CSF biomarkers and neuropsychological profiles in patients with cerebral small-vessel disease.

Despite existing criteria, differential diagnosis of Vascular Dementia (VD) and Alzheimer's disease (AD) remains difficult. The aim of this study is to figure out cognitive and biomarker profiles that may help to distinguish between VD, AD and AD + Cerebral Small Vessel Disease (CSVD). We examined a cohort of patients with CSVD (n = 92). After stratification of cognitive impaired patients (n = 59) using the standard CSF beta-amyloid 42/40 ratio cut-off point of 0.975, we obtained two groups which differed with respect to several features: 32 patients with normal beta-amyloid 42/40 ratio (>0.975) showed markedly impaired blood-brain-barrier function as indicated by an elevated albumin ratio (median 8.35). They also differed in cognitive profiles when compared to 27 patients with AD typical beta-amyloid ratio and normal albumin ratio. We also enrolled an additional group of patients with AD (no significant CSVD on MRI, n = 27) which showed no impairment of the blood-brain-barrier. We showed a negative correlation between the albumin ratio and executive cognitive function (p = 0.016) and a negative correlation between memory function and typical AD markers like Tau (p = 0.004) and p181-Tau (p = 0.023) in our cohort. We suppose that the group of patients with normal beta-amyloid ratio represents VD while patients in the other groups represent AD+CSVD and pure AD. Our results support the idea that a dysfunction of the blood-brain-barrier might be contributing factor in the development of cognitive decline in CSVD as it seems to be of more importance than the severity of white matter lesions.

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.

Characteristic clinical presentation and CSF biomarker pattern in cerebral small vessel disease.

To be able to live a good, independent life cognitive functions need to be intact. Dementia, stroke and neuropsychiatric disorders are the major disorders underlying disability. Stroke is usually a consequence of an underlying vessel wall disease that has lasted for a longer period. This vessel wall disease is commonly silent or without prominent symptoms. Damage to the small penetrating arterioles of the brain, arteriolosclerosis, induced by aging and hypertension, as well as other factors such as diabetes and genetic vulnerability, plays an important role in the origin of white matter changes. The pathological vascular wall process leads to lumen constriction, impaired ability to change lumen diameter according to metabolic needs and possible ischemic-hypoxic tissue damage in the vulnerable vascular architectural terminal areas of the long penetrating arteries. The arteriolosclerotic blood vessels are associated with inflammation and remodelling of the extracellular matrix. Enzymes connected to this process have also been found to be involved in demyelination and blood brain barrier opening but also in the repair process of angiogenesis and neurogenesis. Biochemical changes reflecting these processes might be early indicators of small vessel disease and hence increase the knowledge about the disease characteristic mechanisms. Moreover, monitoring disease modifying treatment effects can be an important application for small vessel disease specific biochemical markers.