White Matter Rarefaction Research Articles

Neuropathological Correlates of White Matter Hyperintensities in Cerebral Amyloid Angiopathy.

White matter hyperintensities (WMHs) are frequently observed on magnetic resonance imaging (MRI) in patients with cerebral amyloid angiopathy (CAA). The neuropathological substrates that underlie WMHs in CAA are unclear, and it remains largely unexplored whether the different WMH distribution patterns associated with CAA (posterior confluent and subcortical multispot) reflect alternative pathophysiological mechanisms. We performed a combined invivo MRI-ex vivo MRI-neuropathological study in patients with definite CAA. Formalin-fixed hemispheres from 19 patients with CAA, most of whom also had invivo MRI available, underwent 3T MRI, followed by standard neuropathological examination of the hemispheres and targeted neuropathological assessment of WMH patterns. Exvivo WMH volume was independently associated with CAA severity (P=0.046) but not with arteriolosclerosis (P=0.743). In targeted neuropathological examination, compared with normal-appearing white matter, posterior confluent WMHs were associated with activated microglia (P=0.043) and clasmatodendrosis (P=0.031), a form of astrocytic injury. Trends were found for an association with white matter rarefaction (P=0.074) and arteriolosclerosis (P=0.094). An exploratory descriptive analysis suggested that the histopathological correlates of WMH multispots were similar to those underlying posterior confluent WMHs. This study confirmed that vascular amyloid β severity in the cortex is significantly associated with WMH volume in patients with definite CAA. The histopathological substrates of both posterior confluent and WMH multispots were comparable, suggesting overlapping pathophysiological mechanisms, although these exploratory observations require confirmation in larger studies.

Hope for vascular cognitive impairment: Ac-YVAD-cmk as a novel treatment against white matter rarefaction.

Vascular cognitive impairment (VCI) is the second leading cause of dementia with limited treatment options, characterised by cerebral hypoperfusion-induced white matter rarefaction (WMR). Subcortical VCI is the most common form of VCI, but the underlying reasons for region susceptibility remain elusive. Recent studies employing the bilateral cortical artery stenosis (BCAS) method demonstrate that various inflammasomes regulate white matter injury and blood-brain barrier dysfunction but whether caspase-1 inhibition will be beneficial remains unclear. To address this, we performed BCAS on C57/BL6 mice to study the effects of Ac-YVAD-cmk, a caspase-1 inhibitor, on the subcortical and cortical regions. Cerebral blood flow (CBF), WMR, neuroinflammation and the expression of tight junction-related proteins associated with blood-brain barrier integrity were assessed 15 days post BCAS. We observed that Ac-YVAD-cmk restored CBF, attenuated BCAS-induced WMR and restored subcortical myelin expression. Within the subcortical region, BCAS activated the NLRP3/caspase-1/interleukin-1beta axis only within the subcortical region, which was attenuated by Ac-YVAD-cmk. Although we observed that BCAS induced significant increases in VCAM-1 expression in both brain regions that were attenuated with Ac-YVAD-cmk, only ZO-1 and occludin were observed to be significantly altered in the subcortical region. Here we show that caspase-1 may contribute to subcortical regional susceptibility in a mouse model of VCI. In addition, our results support further investigations into the potential of Ac-YVAD-cmk as a novel treatment strategy against subcortical VCI and other conditions exhibiting cerebral hypoperfusion-induced WMR.

Characterizing Cerebrovascular Pathologies in Brain Donors Exposed to Repetitive Head Impacts

AbstractBackgroundRepetitive head impacts (RHI) from American style football (ASF) and other contact sports are a known risk factor for the neurodegenerative disease chronic traumatic encephalopathy (CTE). RHI can also lead to mixed neuropathologies that uniquely contribute to clinical symptoms. Here, we compared various types of vascular and white matter pathologies between brain donors with and without exposure to RHI from different types of contact and collision sports (CCS).MethodsThe sample included 79 deceased male ASF players (RHI‐ASF) and 49 deceased male non‐ASF CCS athletes (RHI‐CCS) from the UNITE brain bank. Each RHI group had a comparison group that included similar aged (+/‐ 5 years) male brain donors without RHI from the Boston University Alzheimer’s Disease Research Center and Framingham Heart Study brain banks. The modified Ischemic Injury Scale (mIIS) served as a global indicator of vascular and white matter pathologies and is a sum of hippocampal sclerosis, infarct/lacune, microinfarct, microbleeds, laminar necrosis, arteriolosclerosis, atherosclerosis of Circle of Willis, cerebral amyloid angiopathy, and white matter rarefaction. Dementia diagnoses were made during consensus conferences. Linear or logistic regression compared the RHI vs non‐RHI groups on the mIIS and its subcomponents. Logistic regression models examined the association between mIIS and dementia. Models were adjusted for age.Results Table 1 shows sample characteristics. The RHI‐CCS group was comprised of boxers, amateur wrestlers, and ice hockey, soccer, rugby, and lacrosse players. 94 decedents had CTE, all of whom were in an RHI exposed group. Of the mIIS components, arteriolosclerosis was the most common across all groups. White matter rarefaction was also the most frequent mIIS component for both RHI groups, but not for non‐RHI groups. Compared to their respective controls, RHI‐ASF and RHI‐CCS were associated with higher mIIS scores (Table 2). Higher mIIS scores corresponded to increased odds for having dementia in both the RHI‐ASF and RHI‐CCS groups (Table 2). White matter rarefaction best discriminated both RHI groups from non‐RHI; atherosclerosis also discriminated RHI‐CCS group (Table 3).ConclusionThese results support vascular and white matter pathologies, specifically white matter rarefaction, as prominent and clinically relevant sequelae of RHI from CCS.

Antemortem visit‐to‐visit blood pressure variability and postmortem cerebrovascular disease lesion burden in older adults without dementia

AbstractBackgroundBlood pressure management is an accessible therapeutic target for dementia prevention. Beyond the current focus of managing mean levels, there is a burgeoning interest in understanding the variability in blood pressure levels. Emerging research suggests elevated blood pressure variability is associated with increased risk for Alzheimer’s dementia and cerebrovascular disease, including white matter hyperintensities on MRI (e.g., Fazekas score), but relationships with white matter lesions and overall cerebrovascular pathology at autopsy remain understudied. The aim of the current study was to determine whether antemortem blood pressure variability predicts cerebrovascular pathology in older adults without clinical dementia.Method1866 older adults from the National Alzheimer’s Coordinating Center study underwent repeated approximately annual blood pressure measurement and autopsy and were free of clinical dementia at study baseline. Visit‐to‐visit blood pressure variability was calculated as variability independent of mean using at least 3 (median 5, range 3 ‐ 15) annual blood pressure measurements. White matter rarefaction was scored as none vs mild/moderate vs severe. An index of overall cerebrovascular lesion burden (range 0‐7) was calculated as the sum of severity (0‐2) of atherosclerosis in the Circle of Willis and arteriolosclerosis, and the presence/absence (0‐1) of microinfarcts, infarcts and lacunes, and microbleeds and hemorrhages. Linear and multinomial logistic regression models examined relationships between blood pressure variability, white matter rarefaction severity, and overall cerebrovascular lesion burden, controlling for age, sex, mean blood pressure, antihypertensive use, and Hachinski Ischemic Score, among other variables.ResultElevated blood pressure variability predicted increased severity of white matter rarefaction (OR of mild/moderate [vs none] = 1.21 [1.06, 1.33], p = .004; OR of severe [vs none] = 1.30 [1.07, 1.46], p = .008), and greater overall cerebrovascular lesion burden (ß = .12 [.11, .42]; p < .0001).ConclusionElevated blood pressure variability is related to postmortem cerebrovascular lesion burden, including increased severity of white matter rarefaction, in older adults without clinical dementia, independent of mean blood pressure. Findings are consistent with studies using MRI‐based markers of cerebrovascular disease and may help improve blood pressure as a risk indicator for dementia and cerebrovascular disease.

In vivo cortical diffusion imaging relates to Alzheimer’s disease neuropathology

BackgroundThere has been increasing interest in cortical microstructure as a complementary and earlier measure of neurodegeneration than macrostructural atrophy, but few papers have related cortical diffusion imaging to post-mortem neuropathology.This study aimed to characterise the associations between the main Alzheimer’s disease (AD) neuropathological hallmarks and multiple cortical microstructural measures from in vivo diffusion MRI. Comorbidities and co-pathologies were also investigated.MethodsForty-three autopsy cases (8 cognitively normal, 9 mild cognitive impairment, 26 AD) from the National Alzheimer’s Coordinating Center and Alzheimer’s Disease Neuroimaging Initiative databases were included. Structural and diffusion MRI scans were analysed to calculate cortical minicolumn-related measures (AngleR, PerpPD+, and ParlPD) and mean diffusivity (MD). Neuropathological hallmarks comprised Thal phase, Braak stage, neuritic plaques, and combined AD neuropathological changes (ADNC—the “ABC score” from NIA-AA recommendations).Regarding comorbidities, relationships between cortical microstructure and severity of white matter rarefaction (WMr), cerebral amyloid angiopathy (CAA), atherosclerosis of the circle of Willis (ACW), and locus coeruleus hypopigmentation (LCh) were investigated.Finally, the effect of coexistent pathologies—Lewy body disease and TAR DNA-binding protein 43 (TDP-43)—on cortical microstructure was assessed.ResultsCortical diffusivity measures were significantly associated with Thal phase, Braak stage, ADNC, and LCh. Thal phase was associated with AngleR in temporal areas, while Braak stage was associated with PerpPD+ in a wide cortical pattern, involving mainly temporal and limbic areas. A similar association was found between ADNC (ABC score) and PerpPD+.LCh was associated with PerpPD+, ParlPD, and MD.Co-existent neuropathologies of Lewy body disease and TDP-43 exhibited significantly reduced AngleR and MD compared to ADNC cases without co-pathology.ConclusionsCortical microstructural diffusion MRI is sensitive to AD neuropathology. The associations with the LCh suggest that cortical diffusion measures may indirectly reflect the severity of locus coeruleus neuron loss, perhaps mediated by the severity of microglial activation and tau spreading across the brain.Recognizing the impact of co-pathologies is important for diagnostic and therapeutic decision-making.Microstructural markers of neurodegeneration, sensitive to the range of histopathological features of amyloid, tau, and monoamine pathology, offer a more complete picture of cortical changes across AD than conventional structural atrophy.

Interactions between vascular burden and amyloid-β pathology on trajectories of tau accumulation.

Cerebrovascular pathology often co-exists with Alzheimer's disease pathology and can contribute to Alzheimer's disease-related clinical progression. However, the degree to which vascular burden contributes to Alzheimer's disease pathological progression is still unclear. This study aimed to investigate interactions between vascular burden and amyloid-β pathology on both baseline tau tangle load and longitudinal tau accumulation. We included 1229 participants from the Swedish BioFINDER-2 Study, including cognitively unimpaired and impaired participants with and without biomarker-confirmed amyloid-β pathology. All underwent baseline tau-PET (18F-RO948), and a subset (n = 677) underwent longitudinal tau-PET after 2.5 ± 1.0 years. Tau-PET uptake was computed for a temporal meta-region-of-interest. We focused on four main vascular imaging features and risk factors: microbleeds; white matter lesion volume; stroke-related events (infarcts, lacunes and haemorrhages); and the Framingham Heart Study Cardiovascular Disease risk score. To validate our in vivo results, we examined 1610 autopsy cases from an Arizona-based neuropathology cohort on three main vascular pathological features: cerebral amyloid angiopathy; white matter rarefaction; and infarcts. For the in vivo cohort, primary analyses included age-, sex- and APOE ɛ4-corrected linear mixed models between tau-PET (outcome) and interactions between time, amyloid-β and each vascular feature (predictors). For the neuropathology cohort, age-, sex- and APOE ɛ4-corrected linear models between tau tangle density (outcome) and an interaction between plaque density and each vascular feature (predictors) were performed. In cognitively unimpaired individuals, we observed a significant interaction between microbleeds and amyloid-β pathology on greater baseline tau load (β = 0.68, P < 0.001) and longitudinal tau accumulation (β = 0.11, P < 0.001). For white matter lesion volume, we did not observe a significant independent interaction effect with amyloid-β on tau after accounting for microbleeds. In cognitively unimpaired individuals, we further found that stroke-related events showed a significant negative interaction with amyloid-β on longitudinal tau (β = -0.08, P < 0.001). In cognitively impaired individuals, there were no significant interaction effects between cerebrovascular and amyloid-β pathology at all. In the neuropathology dataset, the in vivo observed interaction effects between cerebral amyloid angiopathy and plaque density (β = 0.38, P < 0.001) and between infarcts and plaque density (β = -0.11, P = 0.005) on tau tangle density were replicated. To conclude, we demonstrated that cerebrovascular pathology-in the presence of amyloid-β pathology-modifies tau accumulation in early stages of Alzheimer's disease. More specifically, the co-occurrence of microbleeds and amyloid-β pathology was associated with greater accumulation of tau aggregates during early disease stages. This opens the possibility that interventions targeting microbleeds may attenuate the rate of tau accumulation in Alzheimer's disease.

Leukoencephalopathy with vanishing white matter disease: a case report study.

The authors report two cases of VWM disease. In the first case, an 8-month-old female child, brought to the pediatric clinic with seizure and loss of consciousness. The second case was a 24-month-old girl, presented with weakness, a disability to walk and swallow, and poor feeding. Her brain MRI demonstrated cystic changes (white matter rarefaction) in supratentorial peri-ventricular white matter and genetic testing result showed an EIF2B3 gene mutation. Leukoencephalopathy with VWM, also known as Cree encephalopathy is caused by mutations in the EIF2B gene. The disease is inherited in an autosomal recessive fashion. There are various agents leading to symptoms and signs of VWM disease. Physical stress like head trauma even in a mild degree, infections, and febrile diseases can be mentioned as causes of VWM. The eIF2B complex, plays a role as an important factor in the regulation of protein synthesis in cells under different conditions. As a conclusion, genetic counseling could be recommended to all individuals with VWM disease and their family members for next pregnancies and possible precautions for consanguineous marriages.

Past antihypertensive medication use is associated with lower levels of small vessel disease and lower Aβ plaque stage in the brains of older individuals.

This study assesses the association of antihypertensive medication use on the severities of neuropathological cerebrovascular disease (CVD excluding lobar infarction) in older individuals. Clinical and neuropathological data were retrieved for 149 autopsy cases >75 years old with or without CVD or Alzheimer's disease and no other neuropathological diagnoses. Clinical data included hypertension status, hypertension diagnosis, antihypertensive medication use, antihypertensive medication dose (where available) and clinical dementia rating (CDR). Neuropathological CVD severity was evaluated for differences with anti-hypertensive medication usage. Antihypertensive medication use was associated with less severe white matter small vessel disease (SVD, mainly perivascular dilatation and rarefaction), with a 5.6-14.4 times greater likelihood of less severe SVD if medicated. No significant relationship was detected between infarction (presence, type, number and size), lacunes or cerebral amyloid angiopathy and antihypertensive medication use. Only increased white matter rarefaction/oedema and not perivascular dilation was associated with Alzheimer's pathology, with a 4.3 times greater likelihood of reduced Aβ progression through the brain if white matter rarefaction severity was none or mild. Antihypertensive medication use was associated with reduced Aβ progression but only in those with moderate to severe white matter SVD. This histopathological study provides further evidence that antihypertensive medication use in older individuals is associated with white matter SVD and not with other CVD pathologies. This is mainly due to a reduction in white matter perivascular dilation and rarefaction/oedema. Even in those with moderate to severe white matter SVD, antihypertensive medication use reduced rarefaction and Aβ propagation through the brain.

Adult-onset leukodystrophy with vanishing white matter: a case series of 19 patients.

Leukodystrophy with vanishing white matter (LVWM) is an autosomal recessive disease with typical pediatric-onset caused by mutations in one of the five EIF2B genes. Adult-onset (AO) cases are rare. In this observational study, we reviewed clinical and laboratory information of the patients with AO-LVWM assessed at two referral centers in Italy and Portugal from Jan-2007 to Dec-2019. We identified 18 patients (13 females) with AO-LVWM caused by EIF2B5 or EIF2B3 mutations. Age of neurological onset ranged from 16 to 60years, with follow-ups occurring from 2 to 37years. Crucial symptoms were cognitive and motor decline. In three patients, stroke-like events were the first manifestation; in another, bladder dysfunction remained the main complaint across decades. Brain MRI showed white matter (WM) rarefaction in all cases, except two. Diffusion-weighted imaging documented focal hyperintensity in the acute stage of stroke-like events. 1H-spectroscopy primarily showed N-acetyl-aspartate reduction; 18fluorodeoxyglucose-PET revealed predominant frontoparietal hypometabolism; evoked potential studies demonstrated normal-to-reduced amplitudes; neuro-ophthalmological assessment showed neuroretinal thinning, and b-wave reduction on full-field electroretinogram. Interestingly, we found an additional patient with LVWM-compatible phenotype and monoallelic variants in two distinct eIF2B genes, EIF2B1 and EIF2B2. AO-LVWM presents varying clinical manifestations at onset, including stroke-like events. WM rarefaction is the most consistent diagnostic clue even in the latest onset cases. Spectroscopy and electrophysiological features are compatible with axon, rather than myelin, damage. Cerebral glucose metabolic abnormalities and retinal alterations can be present. LVWM might also be caused by a digenic inheritance affecting the eIF2B complex.

Cerebral white matter rarefaction has both neurodegenerative and vascular causes and may primarily be a distal axonopathy.

Cerebral white matter rarefaction (CWMR) was considered by Binswanger and Alzheimer to be due to cerebral arteriolosclerosis. Renewed attention came with CT and MR brain imaging, and neuropathological studies finding a high rate of CWMR in Alzheimer disease (AD). The relative contributions of cerebrovascular disease and AD to CWMR are still uncertain. In 1181 autopsies by the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND), large-format brain sections were used to grade CWMR and determine its vascular and neurodegenerative correlates. Almost all neurodegenerative diseases had more severe CWMR than the normal control group. Multivariable logistic regression models indicated that Braak neurofibrillary stage was the strongest predictor of CWMR, with additional independently significant predictors including age, cortical and diencephalic lacunar and microinfarcts, body mass index, and female sex. It appears that while AD and cerebrovascular pathology may be additive in causing CWMR, both may be solely capable of this. The typical periventricular pattern suggests that CWMR is primarily a distal axonopathy caused by dysfunction of the cell bodies of long-association corticocortical projection neurons. A consequence of these findings is that CWMR should not be viewed simply as "small vessel disease" or as a pathognomonic indicator of vascular cognitive impairment or vascular dementia.

Secretomics Alterations and Astrocyte Dysfunction in Human iPSC of Leukoencephalopathy with Vanishing White Matter.

Leukoencephalopathy with vanishing white matter (VWM) is an inherited leukoencephalopathy characterized by progressive rarefaction of cerebral white matter. Dysfunction of patient astrocyte plays a central role in the pathogenesis, while the immaturity of oligodendrocyte is probably secondary. How eIF2B mutant astrocytes affect the maturation and myelination of oligodendrocyte precursor cells (OPCs) is unclear yet. We used induced pluripotent stem cells (iPSCs) derived from our patient with EIF2B5 mutations to differentiate into astrocytes (AS) and OPCs, and aimed to verify that patient astrocytes inhibited the differentiation of OPCs by abnormalities of secreted proteins. eIF2B mutant astrocytes and astrocyte-conditioned medium (ACM) both inhibited the maturation of OPCs. It was revealed that 13 promising proteins exhibited a similar up- or downregulation by the PRM method correlated well with TMT results. eIF2B mutant astrocytes may secrete abnormal extracellular matrix (HA, LAMA4, BGN, FBN1, VASN, PCOLCE, MFAP4), cytokines (IL-6, CRABP1, ISG15), growth factors (PDGF-AA, CNTF, IGF-II, sFRP1, SERPINF1) and increased FABP7, which might lead to the differentiation and maturation disorder of OPCs. We analyzed the astrocyte-conditioned medium to find the key secretory molecules affecting the differentiation and maturation of OPCs, which provides potential clues for further research on the mechanism of VWM.

The Underlying Role of the Glymphatic System and Meningeal Lymphatic Vessels in Cerebral Small Vessel Disease.

There is a growing prevalence of vascular cognitive impairment (VCI) worldwide, and most research has suggested that cerebral small vessel disease (CSVD) is the main contributor to VCI. Several potential physiopathologic mechanisms have been proven to be involved in the process of CSVD, such as blood-brain barrier damage, small vessels stiffening, venous collagenosis, cerebral blood flow reduction, white matter rarefaction, chronic ischaemia, neuroinflammation, myelin damage, and subsequent neurodegeneration. However, there still is a limited overall understanding of the sequence and the relative importance of these mechanisms. The glymphatic system (GS) and meningeal lymphatic vessels (mLVs) are the analogs of the lymphatic system in the central nervous system (CNS). As such, these systems play critical roles in regulating cerebrospinal fluid (CSF) and interstitial fluid (ISF) transport, waste clearance, and, potentially, neuroinflammation. Accumulating evidence has suggested that the glymphatic and meningeal lymphatic vessels played vital roles in animal models of CSVD and patients with CSVD. Given the complexity of CSVD, it was significant to understand the underlying interaction between glymphatic and meningeal lymphatic transport with CSVD. Here, we provide a novel framework based on new advances in main four aspects, including vascular risk factors, potential mechanisms, clinical subtypes, and cognition, which aims to explain how the glymphatic system and meningeal lymphatic vessels contribute to the progression of CSVD and proposes a comprehensive insight into the novel therapeutic strategy of CSVD.

Association Between Antemortem FLAIR White Matter Hyperintensities and Neuropathology in Brain Donors Exposed to Repetitive Head Impacts.

Late neuropathologies of repetitive head impacts from contact sports can include chronic traumatic encephalopathy (CTE) and white matter degeneration. White matter hyperintensities (WMH) on fluid-attenuated inversion recovery (FLAIR) MRI scans are often viewed as microvascular disease from vascular risk, but might have unique underlying pathologies and risk factors in the setting of repetitive head impacts. We investigated the neuropathologic correlates of antemortem WMH in brain donors exposed to repetitive head impacts. The association between WMH and repetitive head impact exposure and informant-reported cognitive and daily function were tested. This imaging-pathologic correlation study included symptomatic male decedents exposed to repetitive head impacts. Donors had antemortem FLAIR scans from medical records and were without evidence of CNS neoplasm, large vessel infarcts, hemorrhage, or encephalomalacia. WMH were quantified using log-transformed values for total lesion volume (TLV), calculated using the lesion prediction algorithm from the Lesion Segmentation Toolbox. Neuropathologic assessments included semiquantitative ratings of white matter rarefaction, cerebrovascular disease, hyperphosphorylated tau (p-tau) severity (CTE stage, dorsolateral frontal cortex), and β-amyloid (Aβ). Among football players, years of play was a proxy for repetitive head impact exposure. Retrospective informant-reported cognitive and daily function were assessed using the Cognitive Difficulties Scale (CDS) and Functional Activities Questionnaire (FAQ). Regression models controlled for demographics, diabetes, hypertension, and MRI resolution. Statistical significance was defined as p ≤ 0.05. The sample included 75 donors: 67 football players and 8 nonfootball contact sport athletes or military veterans. Dementia was the most common MRI indication (64%). Fifty-three (70.7%) had CTE at autopsy. Log TLV was associated with white matter rarefaction (odds ratio [OR] 2.32, 95% confidence interval [CI] 1.03, 5.24; p = 0.04), arteriolosclerosis (OR 2.38, 95% CI 1.02, 5.52; p = 0.04), CTE stage (OR 2.58, 95% CI 1.17, 5.71; p = 0.02), and dorsolateral frontal p-tau severity (OR 3.03, 95% CI 1.32, 6.97; p = 0.01). There was no association with Aβ. More years of football play was associated with log TLV (unstandardized β 0.04, 95% CI 0.01, 0.06; p = 0.01). Greater log TLV correlated with higher FAQ (unstandardized β 4.94, 95% CI 0.42, 8.57; p = 0.03) and CDS scores (unstandardized β 15.35, 95% CI -0.27, 30.97; p = 0.05). WMH might capture long-term white matter pathologies from repetitive head impacts, including those from white matter rarefaction and p-tau, in addition to microvascular disease. Prospective imaging-pathologic correlation studies are needed. This study provides Class IV evidence of associations between FLAIR white matter hyperintensities and neuropathologic changes (white matter rarefaction, arteriolosclerosis, p-tau accumulation), years of American football play, and reported cognitive symptoms in symptomatic brain donors exposed to repetitive head impacts.

MRI Natural History of the Leukodystrophy Vanishing White Matter.

Background In vanishing white matter (VWM), a form of leukodystrophy, earlier onset is associated with faster clinical progression. MRI typically shows rarefaction and cystic destruction of the cerebral white matter. Information on the evolution of VWM according to age at onset is lacking. Purpose To determine whether nature and progression of cerebral white matter abnormalities in VWM differ according to age at onset. Materials and Methods Patients with genetically confirmed VWM were stratified into six groups according to age at onset: younger than 1 year, 1 year to younger than 2 years, 2 years to younger than 4 years, 4 years to younger than 8 years, 8 years to younger than 18 years, and 18 years or older. With institutional review board approval, all available MRI scans obtained between 1985 and 2019 were retrospectively analyzed with three methods: (a) ratio of the width of the lateral ventricles over the skull (ventricle-to-skull ratio [VSR]) was measured to estimate brain atrophy; (b) cerebral white matter was visually scored as percentage normal, hyperintense, rarefied, or cystic on fluid-attenuated inversion recovery (FLAIR) images and converted into a white matter decay score; and (c) the intracranial volume was segmented into normal-appearing white and gray matter, abnormal but structurally present (FLAIR-hyperintense) and rarefied or cystic (FLAIR-hypointense) white matter, and ventricular and extracerebral cerebrospinal fluid (CSF). Multilevel regression analyses with patient as a clustering variable were performed to account for the nested data structure. Results A total of 461 examinations in 270 patients (median age, 7 years [interquartile range, 3-18 years]; 144 female patients) were evaluated; 112 patients had undergone serial imaging. Patients with later onset had higher VSR [F(5) = 8.42; P < .001] and CSF volume [F(5) = 21.7; P < .001] and lower white matter decay score [F(5) = 4.68; P < .001] and rarefied or cystic white matter volume [F(5) = 13.3; P < .001]. Rate of progression of white matter decay scores [b = -1.6, t(109) = -3.9; P < .001] and VSRs [b = -0.05, t (109) = -3.7; P < .001] were lower with later onset. Conclusion A radiologic spectrum based on age at onset exists in vanishing white matter. The earlier the onset, the faster and more cystic the white matter decay, whereas with later onset, white matter atrophy and gliosis predominate. © RSNA, 2021.

Altered oligodendroglia and astroglia in chronic traumatic encephalopathy

Chronic traumatic encephalopathy (CTE) is a progressive tauopathy found in contact sport athletes, military veterans, and others exposed to repetitive head impacts. White matter rarefaction and axonal loss have been reported in CTE but have not been characterized on a molecular or cellular level. Here, we present RNA sequencing profiles of cell nuclei from postmortem dorsolateral frontal white matter from eight individuals with neuropathologically confirmed CTE and eight age- and sex-matched controls. Analyzing these profiles using unbiased clustering approaches, we identified eighteen transcriptomically distinct cell groups (clusters), reflecting cell types and/or cell states, of which a subset showed differences between CTE and control tissue. Independent in situ methods applied on tissue sections adjacent to that used in the single-nucleus RNA-seq work yielded similar findings. Oligodendrocytes were found to be most severely affected in the CTE white matter samples; they were diminished in number and altered in relative proportions across subtype clusters. Further, the CTE-enriched oligodendrocyte population showed greater abundance of transcripts relevant to iron metabolism and cellular stress response. CTE tissue also demonstrated excessive iron accumulation histologically. In astrocytes, total cell numbers were indistinguishable between CTE and control samples, but transcripts associated with neuroinflammation were elevated in the CTE astrocyte groups compared to controls. These results demonstrate specific molecular and cellular differences in CTE oligodendrocytes and astrocytes and suggest that white matter alterations are a critical aspect of CTE neurodegeneration.

Imaging Patterns Characterizing Mitochondrial Leukodystrophies.

Achieving a specific diagnosis in leukodystrophies is often difficult due to clinical and genetic heterogeneity. Mitochondrial defects cause 5%-10% of leukodystrophies. Our objective was to define MR imaging features commonly shared by mitochondrial leukodystrophies and to distinguish MR imaging patterns related to specific genetic defects. One hundred thirty-two patients with a mitochondrial leukodystrophy with known genetic defects were identified in the data base of the Amsterdam Leukodystrophy Center. Numerous anatomic structures were systematically assessed on brain MR imaging. Additionally, lesion characteristics were scored. Statistical group analysis was performed for 57 MR imaging features by hierarchic testing on clustered genetic subgroups. MR imaging features indicative of mitochondrial disease that were frequently found included white matter rarefaction (n = 50 patients), well-delineated cysts (n = 20 patients), T2 hyperintensity of the middle blade of the corpus callosum (n = 85 patients), and symmetric abnormalities in deep gray matter structures (n = 42 patients). Several disorders or clusters of disorders had characteristic features. The combination of T2 hyperintensity in the brain stem, middle cerebellar peduncles, and thalami was associated with complex 2 deficiency. Predominantly periventricular localization of T2 hyperintensities and cystic lesions with a distinct border was associated with defects in complexes 3 and 4. T2-hyperintense signal of the cerebellar cortex was specifically associated with variants in the gene NUBPL. T2 hyperintensities predominantly affecting the directly subcortical cerebral white matter, globus pallidus, and substantia nigra were associated with Kearns-Sayre syndrome. In a large group of patients with a mitochondrial leukodystrophy, general MR imaging features suggestive of mitochondrial disease were found. Additionally, we identified several MR imaging patterns correlating with specific genotypes. Recognition of these patterns facilitates the diagnosis in future patients.

Vascular Lesions, APOE ε4, and Tau Pathology in Alzheimer Disease.

We sought to determine the associations among cerebral amyloid angiopathy (CAA), white matter rarefaction (WMR), circle of Willis atherosclerosis (CWA), and total microinfarct number with Braak neurofibrillary stage in postmortem individuals with and without Alzheimer disease (AD). Data from 355 cases of autopsied individuals with Braak stage I-VI who had antemortem consensus diagnoses of cognitively unimpaired (n = 183), amnestic mild cognitive impairment (n = 31), and AD dementia (n = 141) were used. The association between Braak stage and vascular lesions were individually assessed using multivariable linear regression that adjusted for age at death, APOE ε4 carrier status, sex, education, and neuritic plaque density. CAA (p = 0.007) and WMR (p < 0.001) were associated with Braak stage, independent of amyloid load; microinfarct number and CWA showed no association. Analyses of the interactions between APOE ε4 carrier status and vascular lesions found that greater WMR and positive ε4 carrier status were associated with higher Braak stages. These results suggest that CAA and WMR are statistically linked to the severity of AD-related NFT pathology. The statistical link between WMR and NFT load may be strengthened by the presence of APOE ε4 carrier status. An additional finding was that Lewy body pathology was most prevalent in higher Braak stages.

Brain Ischemia as a Prelude to Alzheimer's Disease.

Transient ischemic brain injury causes massive neuronal death in the hippocampus of both humans and animals. This was accompanied by progressive atrophy of the hippocampus, brain cortex, and white matter lesions. Furthermore, it has been noted that neurodegenerative processes after an episode of ischemia-reperfusion in the brain can continue well-beyond the acute stage. Rarefaction of white matter was significantly increased in animals at 2 years following ischemia. Some rats that survived 2 years after ischemia developed severe brain atrophy with dementia. The profile of post-ischemic brain neurodegeneration shares a commonality with neurodegeneration in Alzheimer's disease. Furthermore, post-ischemic brain injury is associated with the deposition of folding proteins, such as amyloid and tau protein, in the intracellular and extracellular space. Recent studies on post-ischemic brain neurodegeneration have revealed the dysregulation of Alzheimer's disease-associated genes such as amyloid protein precursor, α-secretase, β-secretase, presenilin 1, presenilin 2, and tau protein. The latest data demonstrate that Alzheimer's disease-related proteins and their genes play a key role in the development of post-ischemic brain neurodegeneration with full-blown dementia in disease types such as Alzheimer's. Ongoing interest in the study of brain ischemia has provided evidence showing that ischemia may be involved in the development of the genotype and phenotype of Alzheimer's disease, suggesting that brain ischemia can be considered as a useful model for understanding the mechanisms responsible for the initiation of Alzheimer's disease.

Increased serum QUIN/KYNA is a reliable biomarker of post-stroke cognitive decline

BackgroundStrokes are becoming less severe due to increased numbers of intensive care units and improved treatments. As patients survive longer, post-stroke cognitive impairment (PSCI) has become a major health public issue. Diabetes has been identified as an independent predictive factor for PSCI. Here, we characterized a clinically relevant mouse model of PSCI, induced by permanent cerebral artery occlusion in diabetic mice, and investigated whether a reliable biomarker of PSCI may emerge from the kynurenine pathway which has been linked to inflammatory processes.MethodsCortical infarct was induced by permanent middle cerebral artery occlusion in male diabetic mice (streptozotocin IP). Six weeks later, cognitive assessment was performed using the Barnes maze, hippocampi long-term potentiation using microelectrodes array recordings, and neuronal death, white matter rarefaction and microglia/macrophages density assessed in both hemispheres using imunohistochemistry. Brain and serum metabolites of the kynurenin pathway were measured using HPLC and mass fragmentography. At last, these same metabolites were measured in the patient’s serum, at the acute phase of stroke, to determine if they could predict PSCI 3 months later.ResultsWe found long-term spatial memory was impaired in diabetic mice 6 weeks after stroke induction. Synaptic plasticity was completely suppressed in both hippocampi along with increased neuronal death, white matter rarefaction in both striatum, and increased microglial/macrophage density in the ipsilateral hemisphere. Brain and serum quinolinic acid concentrations and quinolinic acid over kynurenic acid ratios were significantly increased compared to control, diabetic and non-diabetic ischemic mice, where PSCI was absent. These putative serum biomarkers were strongly correlated with degradation of long-term memory, neuronal death, microglia/macrophage infiltration and white matter rarefaction. Moreover, we identified these same serum biomarkers as potential predictors of PSCI in a pilot study of stroke patients.Conclusionswe have established and characterized a new model of PSCI, functionally and structurally, and we have shown that the QUIN/KYNA ratio could be used as a surrogate biomarker of PSCI, which may now be tested in large prospective studies of stroke patients.

The Contribution of Cerebral Vascular Neuropathology to Mild Stage of Alzheimer's Dementia Using the NACC Database.

The interaction between cerebral vessel disease (CVD) pathology and Alzheimer's disease (AD) pathology in the development of dementia is controversial. We examined the association of cerebral vascular neuropathology and cerebrovascular risk factors with the mild stage of Alzheimer's dementia and cognitive function. This cross-sectional study included men and women aged 60 years or over who had yearly clinical assessments and had agreed to brain autopsy at the time of death, and who contributed to data stored at the National Alzheimer's Coordinating Center (NACC) in the USA. Cognitively normal and impaired subjects with presumptive aetiology of AD, including mild cognitive impairment (ADMCI) and dementia (Alzheimer's dementia), and with complete neuropathological data, were included in our analyses. We used neuropsychological data proximate to death to create summary measures of global cognition and cognitive domains. Systematic neuropathological assessments documenting the severity of cerebral vascular pathology were included. Logistic and linear regression analyses corrected for age at death, sex and Lewy body pathology were used to examine associations of vessel disease with the severity of Alzheimer's disease dementia, and cognitive function, respectively. No significant relationship was observed between late-life risk factors and Alzheimer's dementia. The severity of arteriosclerosis and presence of global infarcts/lacunes were related to mild Alzheimer's dementia (B=0.423, p<0.001; B=0.366, p=0.026), and the effects were significant after adjusting for neuritic plaques and neurofibrillary tangles (B=0.385, p<0.001; B=0.63, p=0.001). When vascular brain injuries were subdivided into old and acute/subacute types, we found that old microinfarcts and old microbleeds were associated with mild Alzheimer's dementia (B=0.754, p=0.007; B=2.331, p=0.032). The old microinfarcts remained significantly associated with mild Alzheimer's dementia after correcting AD pathologies (B=1.31, p<0.001). In addition, the number of microinfarcts in the cerebral cortex had a significant relation with mild Alzheimer's dementia, whether or not the data were corrected for AD pathologies (B=0.616, p=0.016; B=0.884, p=0.005). Atherosclerosis, arteriosclerosis and white matter rarefaction were found to be significantly associated with faster progression of Alzheimer's dementia (B=0.068, p=0.001; B=0.046, p=0.016, B=0.081, p=0.037), but white matter rarefaction no longer had a significant effect after adjusting for AD pathologies. We also found that the severity of atherosclerosis was related to impairment in processing speed (β=-0.112, p=0.006) and executive function (β=-0.092, p=0.023). Arteriosclerosis was significantly associated with language (β=-0.103, p=0.011) and global cognition (β=-0.098, p=0.016) deficits. Our study found the significant relation of global, old, acute/subacute and regional cerebral vascular pathologies, but not white matter rarefaction, to the onset and severity of Alzheimer's dementia. We also showed that late-life risk factors were found to have no relation with Alzheimer's dementia, and the increased risk of dementia with APOE ε4 is not mediated by CVD. The best interpretation of these findings is that CVD has a potential additive effect with AD pathologies in the development and progression of what is clinically diagnosed as Alzheimer's dementia.