In vivo demonstration of blood-brain barrier impairment in Moyamoya disease

Fluorescein videoangiography (FL-VAG) as a predictor of cerebral bypass patency

Background

The fluorescein videoangiography (FL-VAG) has become a valuable adjunct tool in vascular neurosurgery. This work describes using the FL-VAG during bypass surgery and proposes a classification method for evaluating surgical results.

Methods

We analyzed 26 patients with 50 cerebral bypasses from September 2018 to September 2022. We used a three grades classification method based on the pass of intravenous fluorescein through the anastomosis. Grade 1 represents the synchronous and total filling of the "T" shape ("green T″) formed by the donor and recipient vessel, Grade 2, the asynchronous filling of the anastomosis (incomplete/asynchronous "green T″), and Grade 3, a non-patent anastomosis (absence of "green T″).

Results

Of the 26 patients, 8 underwent one bypass, 14 underwent double bypass, 2 underwent three bypasses, and 2 underwent four bypasses in two different interventions. The type of bypass was end-to-side anastomosis in 47 (94%) cases, internal maxillary artery to middle cerebral artery bypass with a radial artery graft (IMax-MCA anastomosis) in 2 (4%), and PICA-VA transposition in one (2%). We made 24 (48%) bypasses on the right side and 26 (52%) on the left side. After the initial surgery, thirty-nine (78%) bypasses were considered as Grade 1, 5 (10%) as Grade 2, and 6 (12%) as Grade 3. After intraoperative bypass patency assessment (IBPA), 45 (90%) of the bypasses were considered Grade 1 and remained patent on CTA.

Conclusions

Using FL-VAG and a three-tier classification method is a reliable tool to predict bypass patency. It is safe, low-risk, and available worldwide.

RNF213 variant and autophagic impairment: A pivotal link to endothelial dysfunction in moyamoya disease

Moyamoya disease (MMD) is closely associated with the Ring Finger Protein 213 (RNF213), a susceptibility gene for MMD. However, its biological function remains unclear. We aimed to elucidate the role of RNF213 in the damage incurred by human endothelial cells under oxygen-glucose deprivation (OGD). We analyzed autophagy in peripheral blood mononuclear cells (PBMCs) derived from patients carrying either RNF213 wildtype (WT) or variant (p.R4810K). Subsequently, human umbilical vein endothelial cells (HUVECs) were transfected with RNF213 WT (HUVECWT) or p.R4810K (HUVECR4810K) and exposed to OGD for 2 h. Immunoblotting was used to analyze autophagy marker proteins, and endothelial function was analyzed by tube formation assay. Autophagic vesicles were observed using transmission electron microscopy. Post-OGD exposure, we administered rapamycin and cilostazol as potential autophagy inducers. The RNF213 variant group during post-OGD exposure (vs. pre-OGD) showed autophagy inhibition, increased protein expression of SQSTM1/p62 (p < 0.0001) and LC3-II (p = 0.0039), and impaired endothelial function (p = 0.0252). HUVECR4810K during post-OGD exposure (versus pre-OGD) showed a remarkable increase in autophagic vesicles. Administration of rapamycin and cilostazol notably restored the function of HUVECR4810K and autophagy. Our findings support the pivotal role of autophagy impaired by the RNF213 variant in MMD-induced endothelial cell dysfunction.

Blood-brain barrier disruption imaging in postoperative cerebral hyperperfusion syndrome using DCE-MRI

Little has been reported about the association between cerebral hyperperfusion syndrome (CHS) and blood-brain barrier (BBB) disruption in human. We aimed to investigate the changes in permeability after bypass surgery in cerebrovascular steno-occlusive diseases using dynamic contrast-enhanced MRI (DCE-MRI) and to demonstrate the association between CHS and BBB disruption. This retrospective study included 36 patients (21 hemispheres in 18 CHS patients and 20 hemispheres in 18 controls) who underwent combined bypass surgery for moyamoya and atherosclerotic steno-occlusive diseases. DCE-MRI and arterial spin labeling perfusion-weighted imaging (ASL-PWI) were obtained at the baseline, postoperative state, and discharge. Perfusion and permeability parameters were calculated at the MCA territory (CBF(territorial), Ktrans(territorial), Vp(territorial)) and focal perianastomotic area (CBF(focal), Ktrans(focal), Vp(focal)) of operated hemispheres. As compared with the baseline, both CBF(territorial) and CBF(focal) increased in the postoperative period and decreased at discharge, corresponding well to symptoms in the CHS group. Vp(focal) was lower in the postoperative period and at discharge, as compared with the baseline. In the control group, no parameters significantly differed among the three points. In conclusion, Vp at the focal perianastomotic area significantly decreased in patients with CHS during the postoperative period. BBB disruption may be implicated in the development of CHS after bypass surgery.

Dilated perivascular spaces and steno-occlusive changes in children and adults with moyamoya disease

BACKGROUND

Dilated perivascular spaces (DPVS), known as one of imaging markers in cerebral small vessel disease, may be found in patients with moyamoya disease (MMD). However, little is known about DPVS in MMD. The purpose of this study was to investigate the distribution pattern of dPVS in children and adults with MMD and determine whether it is related to steno-occlusive changes of MMD.

METHODS

DPVS was scored in basal ganglia (BG) and white matter (WM) on T2-weighted imaging, using a validated 4-point semi-quantitative score. The degree of dPVS was classified as high (score > 2) or low (score ≤ 2) grade. The steno-occlusive changes on MR angiography (MRA) was scored using a validated MRA grading. Asymmetry of DPVS and MRA grading was defined as a difference of 1 grade or higher between hemispheres.

RESULTS

Fifty-one patients with MMD (mean age 24.9 ± 21.1 years) were included. Forty-five (88.2%) patients had high WM-DPVS grade (degree 3 or 4). BG-DPVS was found in 72.5% of all patients and all were low grade (degree 1 or 2). The distribution patterns of DPVS degree in BG (P = 1.000) and WM (P = 0.767) were not different between child and adult groups. The asymmetry of WM-DPVS (26%) and MRA grade (42%) were significantly correlated to each other (Kendall's tau-b = 0.604, P < 0.001).

CONCLUSIONS

DPVS of high grade in MMD is predominantly found in WM, which was not different between children and adults. The correlation between asymmetry of WM-DPVS degree and MRA grade suggests that weak cerebral artery pulsation due to steno-occlusive changes may affect WM-DPVS in MMD.

Inhalational Anesthesia Reduced Transient Neurological Events After Revascularization Surgery for Moyamoya Disease

BACKGROUND AND OBJECTIVES

The choice between inhalational and total intravenous anesthesia (TIVA) in revascularization surgery for Moyamoya disease (MMD) remains a topic of debate. Anesthesia methods have changed with the advent of new anesthetics. This study investigated whether modern anesthesia methods affected the development of neurological symptoms after revascularization surgery for MMD.

METHODS

This single-center retrospective study included 63 adult patients (82 hemispheres) with MMD treated with direct and indirect bypass surgeries at our hospital between 2013 and 2022. Patients were divided into inhalational anesthesia (IA) and TIVA groups based on the anesthesia maintenance method. Baseline patient characteristics; postoperative neurological symptoms, including hyperperfusion syndrome, cerebral infarction, and transient neurological events (TNEs); and cortical hyperintensity belt (CHB) sign scores (5-point scale from 0 to 4) on postoperative magnetic resonance imaging were compared between the two groups. The operation methods, anesthetics, and intraoperative hemodynamic and ventilatory parameters were compared between patients with and without TNEs.

RESULTS

The IA and TIVA groups comprised 39 and 43 hemispheres, respectively. The frequency of postoperative hyperperfusion syndrome and cerebral infarction did not differ between the groups, but the number of TNEs in the IA group (5/39; 13%) was significantly lower than that in the TIVA group (16/43; 37%). Multivariate logistic regression analysis revealed that TNEs were associated with TIVA (odds ratio, 3.91; 95% CI, 1.24-12.35; P = .02). The median [IQR] postoperative CHB sign score in the IA group (2 [1-3]) was significantly lower than that in the TIVA group (4 [3-4]).

CONCLUSION

The IA group had fewer postoperative TNEs and lower CHB sign scores than the TIVA group. Although further studies are needed, this study provides insights into the prevention of TNEs with IA and reconsideration of the optimal anesthesia for MMD.

Bradykinin-bradykinin receptor (B1R) signalling is involved in the blood-brain barrier disruption in moyamoya disease

Moyamoya disease (MMD) is a rare disorder of the cerebrovascular system. It is a steno-occlusive disease that involves angiogenesis and blood-brain barrier (BBB) disruption. Bradykinin (BK), its metabolite des-Arg9-BK, and receptor (B1R) affect angiogenesis and BBB integrity. In this study, we aimed to investigate the changes in BK, B1R and des-Arg9-BK levels in the serum and brain tissues of patients with MMD and explore the underlying mechanism of these markers in MMD. We obtained the serum samples and superficial temporal artery (STA) tissue of patients with MMD from the Department of Neurosurgery of the Jining First People's Hospital. First, we measured BK, des-Arg9-BK and B1R levels in the serum of patients by means of ELISA. Next, we performed immunofluorescence to determine B1R expression in STA tissues. Finally, we determined the underlying mechanism through Western blot, angiogenesis assay, immunofluorescence, transendothelial electrical resistance and transcytosis assays. Our results demonstrated a significant increase in the BK, des-Arg9-BK and B1R levels in the serum of patients with MMD compared to healthy controls. Furthermore, an increase in the B1R expression level was observed in the STA tissues of patients with MMD. BK and des-Arg9-BK could promote the migratory and proliferative abilities of bEnd.3 cells and inhibited the formation of bEnd.3 cell tubes. In vitro BBB model showed that BK and des-Arg9-BK could reduce claudin-5, ZO-1 and occluding expression and BBB disruption. To the best of our knowledge, our results show an increase in BK and B1R levels in the serum and STA tissues of patients with MMD. BK and Des-Arg9-BK could inhibit angiogenesis, promote migratory and proliferative capacities of cells, and disrupt BBB integrity. Therefore, regulating BK, des-Arg9-BK and B1R levels in the serum and the brain could be potential strategies for treating patients with MMD.

Rnf-213 Knockout Induces Pericyte Reduction and Blood-Brain Barrier Impairment in Mouse

Moyamoya disease (MMD) is a rare cerebrovascular disorder characterized by progressive occlusion of the internal carotid artery and the formation of an abnormal compensatory capillary network at the base of the brain. Genomics studies identified Ring finger protein 213 (RNF213) as a common genetic factor that increases the susceptibility to MMD in East Asian people. However, the function of RNF213 and its roles in pathogenesis of MMD is unclear. Here, we showed that genetic knockout of Rnf213 in mice causes significant pericyte reduction and blood-brain barrier impairment in the cortex. These phenotypes are accompanied with microglia activation and elevated level of proinflammatory cytokines. Additionally, Rnf213-deficient mice showed reduced expression of tight junction proteins, including Occludin, Claudin-5, and ZO-1. Together, these data suggested that RNF213 might contribute to the pathogenesis of MMD through disruption of pericyte homeostasis and blood-brain barrier integrity by dysregulation of inflammatory responses and tight junction formation.

Association of RNF213 polymorphism and cortical hyperintensity sign on fluid-attenuated inversion recovery images after revascularization surgery for moyamoya disease: possible involvement of intrinsic vascular vulnerability

A cortical hyperintensity on fluid-attenuated inversion recovery images (FLAIR cortical hyperintensity (FCH)) is an abnormal finding after revascularization surgery for moyamoya disease. This study aimed to investigate the pathophysiology of FCH through genetic analyses of RNF213 p.R4810K polymorphism and perioperative hemodynamic studies using single-photon emission computed tomography. We studied 96 hemispheres in 65 adults and 47 hemispheres in 27 children, who underwent combined direct and indirect revascularization. Early or late FCH was defined when it was observed on postoperative days 0-2 and 6-9, respectively. FCH scores (range: 0-6) were evaluated according to the extent of FCH in the operated hemisphere. FCHs were significantly more prevalent in adult patients than pediatric patients (early: 94% vs. 78%; late: 97% vs. 59%). In pediatric patients, FCH scores were significantly improved from the early to late phase regardless of the RNF213 genotype (mutant median [IQR]: 2 [1-5] vs. 1 [0-2]; wild-type median: 4 [0.5-6] vs. 0.5 [0-1.75]). In adults, FCH scores were significantly improved in patients with the wild-type RNF213 allele (median: 4 [2-5.25] vs. 2 [2, 3]); however, they showed no significant improvement in patients with the RNF213 mutation. FCH scores were significantly higher in patients with symptomatic cerebral hyperperfusion than those without it (early median: 5 [4, 5] vs. 4 [2-5]; late median: 4 [3-5] vs. 3 [2-4]). In conclusion, the RNF213 p.R4810K polymorphism was associated with prolonged FCH, and extensive FCH was associated with symptomatic cerebral hyperperfusion in adult patients with moyamoya disease.

Serum Kynurenic Acid and Kynurenine Are Negatively Associated with the Risk of Adult Moyamoya Disease

Background and aim. Kynurenine (KYN) and kynurenic acid (KYNA) are key intermediate metabolites associated with inflammation and immune responses in the kynurenine pathway. It remains unknown whether KYN or KYNA is associated with the risk of adult moyamoya disease (MMD). The aim of this study was to prospectively investigate the association between serum KYN or KYNA and the risk of adult MMD. Methods. The study was conducted from July 2020 to December 2021. We measured serum KYN and KYNA levels for 360 adult MMD patients (259 cases of ischemic MMD, 101 cases of hemorrhagic MMD) and 89 age-sex-matched healthy controls. Clinical and laboratory characteristics were collected from the medical record. Results. After multivariate adjustment, decreased serum KYNA (OR, 0.085; 95% CI, 0.035−0.206; p = 0.000) or KYN (OR, 0.430; 95% CI, 0.225−0.820; p = 0.010) levels were associated with increased risk of MMD when upper and lower tertiles were compared. In addition, a higher trend of hemorrhagic MMD was found in MMD patients in KYNA tertile 1 compared with those in tertile 2 to 3 (OR, 0.584; 95% CI, 0.345−0.987; p = 0.044). Addition of serum KYNA (net reclassification improvement: 73.24%, p = 0.000; integrated discrimination improvement: 9.60%, p = 0.000) or KYN (integrated discrimination improvement: 1.70%, p = 0.037) to conventional risk factors significantly improved the risk prediction of MMD. In the exploratory analysis, we observed an interaction between KYN and age (≥40 versus <40 years) or homocysteine levels (≥13.0 versus <13.0 μmol/L) on the risk of MMD. Conclusions. Decreased serum KYNA or KYN levels were associated with an increased risk of adult MMD, suggesting that serum KYNA or KYN may be a valuable predictive biomarker for adult MMD.

An unusual contrast-induced encephalopathy following percutaneous coronary intervention in patients with cerebrovascular abnormalities: A case report

Introduction

Contrast-induced encephalopathy (CIE) is a complication associated with the administration of iodinated contrast, which usually happens minutes to hours after contact with contrast, and fully recovers within 72 h. The clinical manifestations of CIE are diverse, and the pathological mechanism is not explicit.

Methods

We report the case of a 66-year-old female who suffered from a delayed CIE following the administration of iodinated contrast agent. Symptoms were severe. Imaging examination, biochemical and etiological detection were performed timely. The course of neurological symptoms was atypical. Her complex complications of hypothyroidism and cerebrovascular abnormalities contributed to more challenges, which were also clues to the diagnosis. With prompt and active treatment, the patient recovered fully over 10 days.

Discussion

The diagnosis standard of CIE highly depends on the association with the contact of contrast and the exclusion of other nervous system diseases. Complicated clinical circumstances and individual specificity can lead to different clinical manifestations of CIE, making it even more difficult to diagnose and treat. Prompt and dynamic imaging examination would provide great value in the diagnosis and evaluation of CIE. Timely diagnosis and intervention may be the key to its satisfying prognosis.

CT perfusion-based delta-radiomics models to identify collateral vessel formation after revascularization in patients with moyamoya disease

Purpose

To build CT perfusion (CTP)-based delta-radiomics models to identify collateral vessel formation after revascularization in patients with moyamoya disease (MMD).

Methods

Fifty-three MMD patients who underwent CTP and digital subtraction angiography (DSA) examination were retrospectively enrolled. Patients were divided into good and poor groups based on postoperative DSA. CTP parameters, such as mean transit time (MTT), time to drain (TTD), time to maximal plasma concentration (Tmax), and flow extraction product (FE), were obtained. CTP efficacy in evaluating surgical treatment were compared between the good and poor groups. The changes in the relative CTP parameters (ΔrMTT, ΔrTTD, ΔrTmax, and ΔrFE) were calculated to evaluate the differences between pre- and postoperative CTP values. CTP parameters were selected to build delta-radiomics models for identifying collateral vessel formation. The identification performance of machine learning classifiers was assessed using area under the receiver operating characteristic curve (AUC).

Results

Of the 53 patients, 36 (67.9%) and 17 (32.1%) were divided into the good and poor groups, respectively. The postoperative changes of ΔrMTT, ΔrTTD, ΔrTmax, and ΔrFE in the good group were significantly better than the poor group (p < 0.05). Among all CTP parameters in the perfusion improvement evaluation, the ΔrTTD had the largest AUC (0.873). Eleven features were selected from the TTD parameter to build the delta-radiomics model. The classifiers of the support vector machine and k-nearest neighbors showed good diagnostic performance with AUC values of 0.933 and 0.867, respectively.

Conclusion

The TTD-based delta-radiomics model has the potential to identify collateral vessel formation after the operation.

Delayed development of cerebral atrophy after cerebral hyperperfusion following arterial bypass for adult patients with ischemic moyamoya disease: supplementary analysis of a 5-year prospective cohort

BACKGROUND

Adult patients with moyamoya disease (MMD) occasionally exhibit cerebral hyperperfusion after arterial bypass surgery, leading to persistent cognitive decline. The present supplementary analysis of a prospective 5-year cohort study aimed to determine whether cerebral hyperperfusion after arterial bypass surgery for adult patients with misery perfusion due to ischemic MMD causes cerebral atrophy, and whether the development of cerebral atrophy is related to persistent cognitive decline.

METHODS

In total, 31 patients who underwent arterial bypass surgery also underwent fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and neuropsychological testing before surgery and at the end of a 5-year follow-up. The development of cerebral hyperperfusion and hyperperfusion syndrome after surgery was defined based on brain perfusion single-photon emission computed tomography (SPECT) findings and clinical symptoms. Univariate and multivariate logistic regression analyses of factors related to the development of cerebral atrophy on FLAIR MRI or cognitive decline on neuropsychological testing at the end of the 5-year follow-up were performed.

RESULTS

Eleven patients (35%) developed cerebral atrophy in the frontal lobe where the superficial temporal artery was anastomosed. Cerebral hyperperfusion on brain perfusion SPECT (odds ratio [OR], 50.6; p = 0.0008) or cerebral hyperperfusion syndrome (OR, 41.8; p = 0.0026) was independently associated with the development of cerebral atrophy, and cerebral atrophy development was significantly associated with cognitive decline (OR, 47.7; p = 0.0010).

CONCLUSIONS

Cerebral hyperperfusion after arterial bypass surgery for adult patients with misery perfusion due to ischemic MMD can cause cerebral atrophy related to persistent cognitive decline.

Intraoperative Early Venous Filling Phenomenon as an Intrinsic Sign of the Local Hemodynamic Change after Revascularization Surgery in a Patient with Adult Moyamoya Disease: Implications of a Potential Arteriovenous Shunt

After revascularization surgery for patients with moyamoya disease (MMD), local and global hemodynamic changes occur intraoperatively and in the early postoperative period. Local cerebral hyperperfusion and watershed shift ischemia are well-known perioperative pathologies after revascularization for MMD, but early venous filling phenomenon is markedly rare. We report the case of a 19-year-old woman with hemorrhagic-onset MMD who presented with grand mal seizure and subarachnoid hemorrhage. She underwent superficial temporal artery (STA)–middle cerebral artery (MCA) anastomosis combined with indirect pial synangiosis on the affected hemisphere. Intraoperatively, notable early arterial blood filling in the fine cortical vein was observed around the site of anastomosis right after the STA–MCA anastomosis under the surgical microscope and fluorescence indocyanine green video angiography. Recovery of consciousness after general anesthesia was normal, although she exhibited a focal seizure 1 hour later. Postoperative magnetic resonance imaging was not remarkable, and cerebral hemodynamics significantly improved in the acute stage after surgical revascularization. Considering the intrinsic vulnerability of the microvascular anatomy of MMD, the present case is notable because early venous filling was observed intraoperatively. This phenomenon suggests the existence of a potential arteriovenous shunt as an underlying pathology of MMD, but its implications in the early postoperative course should be further verified in a larger number of MMD patients undergoing surgical revascularization.

Moyamoya Disease Susceptibility Gene RNF213 Regulates Endothelial Barrier Function

BACKGROUND

Variants in the ring finger protein 213 (RNF213) gene are known to be associated with increased predisposition to cerebrovascular diseases development. Genomic studies have identified RNF213 as a major risk factor of Moyamoya disease in East Asian descendants. However, little is known about the RNF213 (ring finger protein 213) biological functions or its associated pathogenic mechanisms underlying Moyamoya disease.

METHODS

To investigate RNF213 loss-of-function effect in endothelial cell, stable RNF213-deficient human cerebral endothelial cells were generated using the CRISPR-Cas9 genome editing technology.

RESULTS

In vitro assays, using RNF213 knockout brain endothelial cells, showed clear morphological changes and increased blood-brain barrier permeability. Downregulation and delocalization of essential interendothelial junction proteins involved in the blood-brain barrier maintenance, such as PECAM-1 (platelet endothelial cell adhesion molecule-1), was also observed. Brain endothelial RNF213-deficient cells also showed an abnormal potential to transmigration of leukocytes and secreted high amounts of proinflammatory cytokines.

CONCLUSIONS

Taken together, these results indicate that RNF213 could be a key regulator of cerebral endothelium integrity, whose disruption could be an early pathological mechanism leading to Moyamoya disease. This study also further reinforces the importance of blood-brain barrier integrity in the development of Moyamoya disease and other RNF213-associated diseases.

MMP-9 as a Biomarker for Predicting Hemorrhagic Strokes in Moyamoya Disease

Objective: This study was conducted in order to investigate the association of matrix metalloproteinase (MMP)-9 levels with phenotypes of moyamoya disease (MMD).

Methods: This study included plasma samples from 84 MMD patients. The clinical variables of these patients were reviewed from the medical record. The serum concentration of tight junction, adherens junction proteins, and MMPs (MMP-2 and MMP-9) was determined using the ELISA method. Patients with hemorrhagic-onset MMD were compared with those with ischemic-onset MMD.

Results: Compared with pediatric patients, the expression of MMP-9 was significantly higher, while the MMP-2 and vascular endothelial-cadherin were lower in adult patients. In adult subgroup analysis, hemorrhagic MMD patients exhibited significantly higher serum concentrations of MMP-9 compared with ischemic MMD patients. The ROC curve identified that a baseline serum MMP-9 level >1,011 ng/ml may be associated with spontaneous hemorrhage in adult MMD patients with 70.37% sensitivity and 71.88% specificity [area under curve (AUC), 0.73; 95% CI 0.597–0.864; P = 0.003]. A late Suzuki stage (>4) (OR 4.565, 95% CI 1.028–20.280, P = 0.046) and serum concentrations of MMP-9 >1,011 ng/ml (OR 7.218, 95% CI 1.826–28.533, P = 0.005) are risk predictors of hemorrhages in MMD patients. Hemorrhagic-type MMD patients had higher serum levels of MMP-9 and BBB permeability compared with ischemic-type MMD patients. Adult MMD patients had higher serum levels of MMP-9 and BBB permeability compared with pediatric patients.

Conclusions: MMP-9 might serve as a biomarker for hemorrhage prediction in MMD. Serum MMP-9 level >1,011 ng/ml is an independent risk factor of MMD hemorrhagic strokes.

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Linking cortical astrocytic neogenin deficiency to the development of Moyamoya disease-like vasculopathy

Moyamoya-like vasculopathy, the "puff of smoke"-like small vessels in the brain, is initially identified in patients with Moyamoya disease (MMD), a rare cerebrovascular disease, and later found in patients with various types of neurological conditions, including Down syndrome, Stroke, and vascular dementia. It is thus of interest to understand how this vasculopathy is developed. Here, we provided evidence for cortical astrocytic neogenin (NEO1) deficiency to be a risk factor for its development. NEO1, a member of deleted in colorectal cancer (DCC) family netrin receptors, was reduced in brain samples of patients with MMD. Astrocytic Neo1-loss resulted in an increase of small blood vessels (BVs) selectively in the cortex. These BVs were dysfunctional, with leaky blood-brain barrier (BBB), thin arteries, and accelerated hyperplasia in veins and capillaries, resembled to the features of moyamoya-like vasculopathy. Additionally, we found that both MMD patient and Neo1 mutant mice exhibited altered gene expression in their cortex in proteins critical for not only angiogenesis [e.g., an increase in vascular endothelial growth factor (VEGFa)], but also axon guidance (e.g., netrin family proteins) and inflammation. In aggregates, these results suggest a critical role of astrocytic NEO1-loss in the development of Moyamoya-like vasculopathy, providing a mouse model for investigating mechanisms of Moyamoya-like vasculopathy.

Visualization of brain microvasculature and blood flow in vivo: Feasibility study using confocal laser endomicroscopy

OBJECTIVE

Qualitative and quantitative analyses of blood flow in normal and pathologic brain and spinal cord microvasculature were performed using confocal laser endomicroscopy (CLE).

METHODS

Blood flow in cortical, dural, and spinal cord microvasculature was assessed in vivo in swine. We assessed microvasculature under normal conditions and after vessel occlusion, brain injury due to cold or surgical trauma, and cardiac arrest. Tumor-associated microvasculature was assessed in vivo and ex vivo in 20 patients with gliomas.

RESULTS

We observed erythrocyte flow in vessels 5-500 µm in diameter. Thrombosis, flow arrest and redistribution, flow velocity changes, agglutination, and cells rolling were assessed in normal and injured brain tissue. Microvasculature in in vivo CLE images of gliomas was classified as normal in 68% and abnormal in 32% of vessels on the basis of morphological appearance. Dural lymphatic channels were discriminated from blood vessels. Microvasculature CLE imaging was possible for up to 30 minutes after a 1 mg/kg intravenous dose of fluorescein.

CONCLUSIONS

CLE imaging allows assessment of cerebral and tumor microvasculature and blood flow alterations with subcellular resolution intraoperative imaging demonstrating precise details of real-time cell movements. Research and clinical scenarios may benefit from this novel intraoperative in vivo microscopic fluorescence imaging modality.

Preliminary Study on the Application of Ultrahigh Field Magnetic Resonance in Moyamoya Disease

Magnetic resonance imaging (MRI) is widely used for the evaluation of moyamoya disease (MMD). In this paper, we describe the features of time-of-flight magnetic resonance angiography (TOF-MRA) and susceptibility-weighted imaging (SWI) at 7 T in a series of MMD patients. In this prospective pilot study, 7 patients (median age: 45.6 years; range: 30-52 years) with MMD and no contraindications for MRI underwent T2-weighted, SWI, and TOF-MRA sequences using a research 7 T head-only scanner. We show that such sequences at ultrahigh field (UHF) represent new and valuable approaches to unravel and characterize MMD. While SWI reveals more remarkable imaging signs related to an improved magnitude and phase contrast imaging, the collateral network pathways in MMD could be excellently delineated using 7 T TOF-MRA. In particular, using SWI and MRA fusion images in UHF MRI helps to improve the detection of bleeding points in hemorrhagic MMD. Our findings indicate that ultrahigh field MRI is very promising to access the severity of the disease and may facilitate revascularization surgery of MMD patients.

Circulating sortilin levels are associated with inflammation in patients with moyamoya disease

BACKGROUND

Systemic inflammation has been implicated in the pathogenesis of moyamoya disease (MMD). Sortilin is a critical regulator of proinflammatory cytokine secretion in several cell types. The present study investigated the association between circulating sortilin and proinflammatory cytokine levels and the occurrence of MMD.

METHODS

Forty-two MMD cases and 76 age- and sex-matched controls were enrolled in this study between January 2018 and June 2019 at the Affiliated Hospital of Jining Medical University. The demographic and clinical characteristics were evaluated, and the circulating serum and cerebrospinal fluid (CSF) levels of sortilin, sortilin-related receptor with A-type repeats (SorLA), and proinflammatory cytokines including C-reactive protein (CRP), interleukin (IL)-6, interferon (IFN)-γ were measured by enzyme-linked immunosorbent assay. Linear regression and correlation analyses were used to estimate the associations between sortilin, SorLA, and proinflammatory cytokine levels.

RESULTS

MMD patients had higher serum levels of sortilin (P = 0.012), CRP (P = 0.013), IL-6 (P = 0.004), and IFN-γ (P = 0.033) than healthy controls. In MMD patients, serum sortilin was positively correlated with serum proinflammatory cytokines (CRP: r = 0.459, P = 0.0022; IL-6: r = 0.445, P = 0.0032; and IFN-γ: r = 0.448, P = 0.0029) and CSF sortilin (r = 0.440, P = 0.0035); the latter was positively correlated with CSF levels of CRP (r = 0.542, P = 0.0002), IL-6 (r = 0.440, P = 0.0036), and IFN-γ (r = 0.443, P = 0.0033).

CONCLUSIONS

Elevated sortilin level is associated MMD onset and may be a clinically useful biomarker along with proinflammatory cytokine levels.

Brain vascular biology

The complex development of the brain vascular system can be broken down by embryonic stages and anatomic locations, which are tightly regulated by different factors and pathways in time and spatially. The adult brain is relatively quiescent in angiogenesis. However, under disease conditions, such as trauma, stroke, or tumor, angiogenesis can be activated in the adult brain. Disruption of any of the factors or pathways may lead to malformed vessel development. In this chapter, we will discuss factors and pathways involved in normal brain vasculogenesis and vascular maturation, and the pathogenesis of several brain vascular malformations.

Flow-augmentation bypass for moyamoya disease

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with unknown etiology, which is characterized by progressive steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network formation at the base of the brain. MMD has an intrinsic temporal nature to attempt a gradual conversion of the vascular supply for the brain from intracranial/internal carotid (IC) system to extracranial/external carotid (EC) system, so called "IC-EC conversion." Compatible cerebrovascular angio-architecture could be found in association with a variety of conditions such as neuro-fibromatosis type-1, Down's syndrome and cranial irradiation, which is called as moyamoya syndrome, akin/quasi MMD, or secondary MMD. Diagnosis of moyamoya vasculopathy, either idiopathic or secondary, is clinically important because flow-augmentation bypass is markedly beneficial for this entity to prevent cerebral ischemic attack by improving cerebral blood flow. Moreover, recent evidence indicated that flow-augmentation bypass could prevent re-bleeding in hemorrhagic MMD patients. Based on these backgrounds, there is a worldwide increase in the number of MMD patients undergoing bypass surgery. We sought to demonstrate our standard surgical procedure of superficial temporal artery-middle cerebral artery bypass with indirect pial synangiosis for MMD and its technical pitfall. We also discuss the intrinsic peri-operative hemodynamics of MMD after bypass surgery, including local cerebral hyper-perfusion and characteristic hemodynamic ischemia caused by watershed shift phenomenon. The aim of this review article is to understand the basic pathology of MMD, which is essential for complication avoidance while conducting flow-augmentation bypass for MMD.

Prolonged/delayed cerebral hyperperfusion in adult patients with moyamoya disease with RNF213 gene polymorphism c.14576G>A (rs112735431) after superficial temporal artery-middle cerebral artery anastomosis

OBJECTIVE

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis is the standard surgical management for moyamoya disease (MMD), whereas cerebral hyperperfusion (CHP) is one of the potential complications of this procedure that can result in delayed intracerebral hemorrhage and/or neurological deterioration. Recent advances in perioperative management in the early postoperative period have significantly reduced the risk of CHP syndrome, but delayed intracerebral hemorrhage and prolonged/delayed CHP are still major clinical issues. The clinical implication of RNF213 gene polymorphism c.14576G>A (rs112735431), a susceptibility variant for MMD, includes early disease onset and a more severe form of MMD, but its significance in perioperative pathology is unknown. Thus, the authors investigated the role of RNF213 polymorphism in perioperative hemodynamics after STA-MCA anastomosis for MMD.

METHODS

Among 96 consecutive adult patients with MMD comprising 105 hemispheres who underwent serial quantitative cerebral blood flow (CBF) analysis by N-isopropyl-p-[123I]iodoamphetamine SPECT after STA-MCA anastomosis, 66 patients consented to genetic analysis of RNF213. Patients were routinely maintained under strict blood pressure control during and after surgery. The local CBF values were quantified at the vascular territory supplied by the bypass on postoperative days (PODs) 1 and 7. The authors defined the radiological CHP phenomenon as a local CBF increase of more than 150% compared with the preoperative values, and then they investigated the correlation between RNF213 polymorphism and the development of CHP.

RESULTS

CHP at POD 1 was observed in 23 hemispheres (23/73 hemispheres [31.5%]), and its incidence was not statistically different between groups (15/41 [36.6%] in RNF213-mutant group vs 8/32 [25.0%] in RNF213-wild type (WT) group; p = 0.321). CHP on POD 7, which is a relatively late period of the CHP phenomenon in MMD, was evident in 9 patients (9/73 hemispheres [12.3%]) after STA-MCA anastomosis. This prolonged/delayed CHP was exclusively observed in the RNF213-mutant group (9/41 [22.0%] in the RNF213-mutant group vs 0/32 [0.0%] in the RNF213-WT group; p = 0.004). Multivariate analysis revealed that RNF213 polymorphism was significantly associated with CBF increase on POD 7 (OR 5.47, 95% CI 1.06-28.35; p = 0.043).

CONCLUSIONS

Prolonged/delayed CHP after revascularization surgery was exclusively found in the RNF213-mutant group. Although the exact mechanism underlying the contribution of RNF213 polymorphism to the prolonged/delayed CBF increase in patients with MMD is unclear, the current study suggests that genetic analysis of RNF213 is useful for predicting the perioperative pathology of patients with MMD.

Decreased cortical perfusion in areas with blood-brain barrier dysfunction in Moyamoya disease

BACKGROUND

Recently, several studies have focused on the relationship between blood-brain barrier (BBB) impairment and the etiology of Moyamoya disease (MMD). However, in vivo studies investigating about BBB impairment and cortical perfusion in MMD patients were really rare.

METHODS

This study included 16 patients diagnosed with MMD and 9 patients with atherosclerotic cerebrovascular disease (ACVD); all of who were treated with superficial temporal artery-middle cerebral artery (STA-MCA) bypass. Cortical perfusion was assessed using intraoperative indocyanine green (ICG) videoangiography by calculating the blood flow index (BFI). In addition, we used sodium fluorescein (NaFl) to evaluate the permeability of BBB in vivo during operation.

RESULTS

The results showed that BBB impairment in MMD patients was more significant than that in ACVD patients, whereas, the cortical perfusion was comparable between two groups. BFI was significantly improved after STA-MCA bypass both in the MMD group (post-operation vs pre-operation: 109.2 ± 67.7 vs 64.3 ± 35.0, p = 0.004) and the ACVD group (post-operation vs pre-operation: 137.6 ± 89.6 vs 90.8 ± 58.3, p = 0.015). Moreover, BFI was significantly decreased in the cortex with BBB impairment as compared with that in the cortex with intact BBB (impaired BBB vs intact BBB: 55.7 ± 26.5 vs 87.6 ± 55.1, p = 0.025). Following bypass, the cortical perfusion significantly improved in the area of BBB impairment (post-operation vs pre-operation: 93.8 ± 75.2 vs 55.7 ± 26.5, p = 0.004), which was not observed in the BBB intact area (post-operation vs pre-operation: 92.4 ± 50.4 vs 87.6 ± 55.1, p = 0.58).

CONCLUSION

In summary, we observed that BBB impairment in MMD patients was more significant than that in ACVD patients. This study also demonstrated for the first time that cortical perfusion was significantly decreased in the cortex with BBB impairment as compared with that in the cortex with intact BBB in MMD patients. We also observed that After STA-MCA bypass, the cortical perfusion was significantly improved in the cortex with BBB impairment. These results may provide a new insight for BBB impairment and cortical perfusion in the etiology of MMD.

Pre-operative higher hematocrit and lower total protein levels are independent risk factors for cerebral hyperperfusion syndrome after superficial temporal artery-middle cerebral artery anastomosis with pial synangiosis in adult moyamoya disease patients-case-control study

Superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis is a standard treatment for adult moyamoya disease (MMD) patients. Cerebral hyperperfusion (CHP) syndrome is one of the most serious complications of this procedure that can result in deleterious outcomes, but predicting CHP before revascularization surgery remains challenging. Furthermore, the hematological/serological factors associated with CHP syndrome are unknown. To investigate the correlation between pre-operative hematological/serological factors and the development of CHP syndrome after STA-MCA anastomosis with encephalo-duro-myo-synangiosis (EDMS) for MMD., a pre-operative peripheral blood test was performed within 5 days before surgery. Local cerebral blood flow (CBF) at the site of anastomosis was quantified by N-isopropyl-p-[¹²³I] iodoamphetamine single-photon emission computed tomography 1 and 7 days after surgery, and the pre-operative CBF value at the corresponding area was measured. We defined CHP syndrome as a local CBF increase over 150% compared with the pre-operative value, which was responsible for delayed intracranial hemorrhage, transient focal neurological deterioration, and/or seizure. Then, we retrospectively investigated the correlation between peripheral blood test results and the development of CHP syndrome. CHP syndrome 1 day after STA-MCA anastomosis with EDMS was observed in nine patients (9/114 hemispheres; 7.9%). Multivariate analysis with multiple imputation revealed that higher hematocrit value and lower total protein level were significantly associated with the development of CHP syndrome (p value: 0.028 and 0.043, respectively). Higher pre-operative hematocrit levels and lower pre-operative total protein levels are novel risk factors for CHP syndrome after direct revascularization surgery in adult MMD patients.

Significance of Serum Angiopoietin-2 in Patients with Hemorrhage in Adult-Onset Moyamoya Disease

Background

Moyamoya disease (MMD) is a progressive occlusive cerebrovascular disease that is characterized by abnormal angiogenesis at the base of the brain. This pathological abnormal angiogenesis is susceptible to disturbances, including spontaneous hemorrhage and vasogenic edema. However, the underlying mechanisms of pathological angiogenesis and occurrence of hemorrhage are unclear. Angiopoietins play a fundamental role in the pathophysiology of central nervous system disorders in angiogenesis. This study was aimed at examining whether angiopoietins are associated with formation of abnormal collateral vessels and the occurrence of hemorrhage in adult-onset moyamoya disease (HMMD).

Methods

A total of 27 consecutive adult patients with HMMD were enrolled from June 2011 to May 2017. Serum levels of angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) were examined by enzyme-linked immunosorbent assay. Patients with HMMD were compared with those with spontaneous hemorrhage (controls) and nonhemorrhagic-onset MMD (NHMMD).

Results

Serum Ang-2 levels were significantly higher in patients with adult HMMD than in those with spontaneous hemorrhage and NHMMD. The ROC curve identified that a baseline serum Ang-2 level > 1230 ng/ml may be associated with adult HMMD with 88.39% sensitivity and 70.37% specificity (area under the curve (AUC), 0.89; 95% CI, 0.808-0.973; P < 0.001). Moreover, serum Ang-2 levels were significantly elevated in stages II, III, and IV. In subgroup analysis of a high and low degree of moyamoya vessels, serum Ang-2 levels were significantly higher in the high moyamoya vessel group than in the low moyamoya vessel group. Serum Ang-2 levels were also significantly higher in the low moyamoya vessel group compared with the control group. Serum Ang-1 levels were not significantly different among the groups.

Conclusion

Increased serum Ang-2 levels may contribute to pathological abnormal angiogenesis and/or to the instability of vascular structure and function, thus causing brain hemorrhage in adult HMMD.

Association of Brain-Gut Peptides with Inflammatory Cytokines in Moyamoya Disease

Systemic inflammation has been shown to play a pivotal role in the pathogenesis of moyamoya disease (MMD). Brain-gut peptides exhibit regulatory effects in the secretion of proinflammatory cytokines. To investigate the association between brain-gut peptides and inflammation in the occurrence of MMD, 41 patients with MMD, as well as 74 age- and sex-matched healthy individuals were enrolled. The levels of four brain-gut peptides (vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), somatostatin (SST), substance P (SP)) and three proinflammatory cytokines (interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-12) in the serum and cerebrospinal fluid (CSF) were measured using the enzyme-linked immunosorbent assay. The associations between brain-gut peptides and proinflammatory cytokines were estimated according to the multiple linear regression and correlation analyses. MMD patients exhibited significantly lower levels of VIP, CCK, and SST and higher levels of IL-1β, TNF-α, and IL-12 in the serum compared with healthy controls. Multiple logistic regression analysis showed that decreased VIP, CCK, and SST levels were independent predictors of the occurrence of MMD. Negative correlations were observed between the VIP and proinflammatory cytokines, including IL-1β, TNF-α, and IL-12 (serum vs. CSF). Significant negative correlations were also found between CCK and IL-1β, as well as IL-12 (serum vs. CSF). SST was negatively correlated with IL-1β and TNF-α in the serum and IL-1β only in the CSF. In addition, the levels of VIP, CCK, SST, and proinflammatory cytokines IL-1β and TNF-α in the serum were correlated with those measured in the CSF. Collectively, lower levels of VIP, CCK, and SST may be associated with the pathogenesis of MMD and act as clinically useful biomarkers along with the levels of proinflammatory cytokines.

Revascularization Surgery in Childhood Associated with a Low Incidence of Microbleeds in Adult Patients with Moyamoya

BACKGROUND

The clinical significance of asymptomatic microbleeds in moyamoya disease remains unclear. The purpose of this study was to clarify the relationship between bypass surgery and the incidence of asymptomatic microbleeds.

METHODS

This retrospective study included 142 adult patients (mean age, 37.7 ± 13.5 years) with moyamoya disease, 36 of whom (25.3%) underwent bypass surgery in childhood. Hemorrhagic onset was diagnosed in 31 patients (21.8%). The incidence of microbleeds was evaluated on T2*-weighted or susceptibility-weighted imaging from 3-T magnetic resonance imaging. The patients were subsequently categorized into MBs (microbleeds) or non-MBs groups. Because previous microbleeds potentially lead to hemorrhage, the MBs group was defined as patients with radiographic evidence of bleeding, including asymptomatic microbleeds and/or hemorrhagic onset. The association of baseline characteristics was evaluated.

RESULTS

Asymptomatic microbleeds were detected in 38 patients (26.8%). Of 31 patients with hemorrhagic onset, 18 had microbleeds, whereas 13 had no microbleeds. Therefore, 51 patients (35.9%) were classified into the MBs group. Bypass surgery in childhood (MBs, 7.8% vs. non-MBs, 35.2%; P < 0.01) and age (MBs, 42.9 ± 1.8 years vs. non-MBs, 34.7 ± 1.4 years; P < 0.01) were statistically significant factors associated with microbleeds, but only bypass surgery in childhood remained statistically significant after multivariable adjustment (odds ratio, 0.25; 95% confidence interval, 0.07-0.87; P = 0.03).

CONCLUSIONS

This study shows the clinical significance of revascularization surgery in childhood associated with a low incidence of asymptomatic microbleeds in adult patients with moyamoya disease. This finding indicates that a newly established bypass can reduce hemodynamic overstress.