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Type 2 diabetes mellitus (T2DM) is associated with poor outcome after stroke. Peripheral monocytes play a critical role in the secondary injury and recovery of damaged brain tissue after stroke, but the underlying mechanisms are largely unclear. To investigate transcriptome changes and molecular networks across monocyte subsets in response to T2DM and stroke, we performed single-cell RNA-sequencing (scRNAseq) from peripheral blood mononuclear cells and bulk RNA-sequencing from blood monocytes from four groups of adult mice, consisting of T2DM model db/db and normoglycemic control db/+ mice with or without ischemic stroke. Via scRNAseq we found that T2DM expands the monocyte population at the expense of lymphocytes, which was validated by flow cytometry. Among the monocytes, T2DM also disproportionally increased the inflammatory subsets with Ly6C+ and negative MHC class II expression (MO.6C+II-). Conversely, monocytes from control mice without stroke are enriched with steady-state classical monocyte subset of MO.6C+II+ but with the least percentage of MO.6C+II- subtype. Apart from enhancing inflammation and coagulation, enrichment analysis from both scRNAseq and bulk RNAseq revealed that T2DM specifically suppressed type-1 and type-2 interferon signaling pathways crucial for antigen presentation and the induction of ischemia tolerance. Preconditioning by lipopolysaccharide conferred neuroprotection against ischemic brain injury in db/+ but not in db/db mice and coincided with a lesser induction of brain Interferon-regulatory-factor-3 in the brains of the latter mice. Our results suggest that the increased diversity and altered transcriptome in the monocytes of T2DM mice underlie the worse stroke outcome by exacerbating secondary injury and potentiating stroke-induced immunosuppression. Significance Statement: The mechanisms involved in the detrimental diabetic effect on stroke are largely unclear. We show here, for the first time, that peripheral monocytes have disproportionally altered the subsets and changed transcriptome under diabetes and/or stroke conditions. Moreover, genes in the IFN-related signaling pathways are suppressed in the diabetic monocytes, which underscores the immunosuppression and impaired ischemic tolerance under the T2DM condition. Our data raise a possibility that malfunctioned monocytes may systemically and focally affect the host, leading to the poor outcome of diabetes in the setting of stroke. The results yield important clues to molecular mechanisms involved in the detrimental diabetic effect on stroke outcome.

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Introduction: Clazosentan, a selective endothelin receptor subtype A antagonist, reduces vasospasm-related morbidity and all-cause mortality following aneurysmal subarachnoid hemorrhage (SAH) in the Japanese population, as demonstrated by a recent randomized phase 3 trial. However, evidence to suggest clazosentan should be prioritized over the current standard of care to prevent cerebral vasospasm is still lacking. Therefore, we investigated the efficacy and safety of clazosentan in comparison with conventional postoperative management in real-world clinical practice. Methods: We conducted a single-center, retrospective, observational cohort study using prospectively collected data from consecutive patients with aneurysmal SAH. After clazosentan was approved for use in Japan, the conventional postoperative management protocol, composed of intravenous fasudil chloride and oral cilostazol (control group, April 2021 to March 2022), was changed to the clazosentan protocol (clazosentan group, April 2022 to March 2023). The primary endpoint was the incidence of vasospasm-related symptomatic infarction. The secondary endpoints were favorable functional outcomes (modified Rankin scale score < 3) at discharge, angiographic vasospasm, and the need for rescue therapy for delayed cerebral ischemia. Results: The analysis included 100 and 81 patients in the control and clazosentan groups, respectively. The incidence of vasospasm-related symptomatic infarction was significantly lower in the clazosentan group than in the control group (6.2% vs. 16%, p = 0.032). Multiple logistic analyses demonstrated that the use of clazosentan was independently associated with fewer incidence of vasospasm-related symptomatic infarct (23.8% vs. 47.5%, odds ratio 0.34 [0.12-0.97], p = 0.032). Clazosentan was significantly associated with favorable outcomes at discharge (79% vs. 66%, p = 0.037). Moreover, both the incidence of angiographic vasospasm (25.9% vs. 44%, p = 0.013) and the need for rescue therapy (16.1% vs. 34%, p = 0.006) was lower in the clazosentan group. The occurrence of pulmonary edema was significantly higher with clazosentan use (19.8% vs. 5%, p = 0.002), which did not result in morbidity. Conclusion: A postoperative management protocol centering on clazosentan was associated with the reduced vasospasm-related symptomatic infarction and improved clinical outcomes compared to the conventional management protocol in Japanese clinical practice. Clazosentan might be a promising treatment option for counteracting cerebral vasospasm after aneurysmal SAH.

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BACKGROUND: Postoperative hyperperfusion syndrome (PHS) is a well-known complication following superficial temporal artery (STA)-middle cerebral artery (MCA) bypass for moyamoya disease (MMD). The early detection of postoperative radiological hyperperfusion (PRH), characterized by a transient increase in local cerebral blood flow (CBF), is crucial for the early diagnosis of PHS. This study aimed to investigate the effectiveness of waveform analysis for early PRH detection. METHODS: We reviewed 52 consecutive patients who underwent STA-MCA bypass for MMD. Patients were divided into PRH and non-PRH groups based on the postoperative/preoperative CBF ratio. We collected the intraoperative bypass graft waveform and bypass flow data using a flowmeter. The pulsatile index (PI), an indicator of peripheral vascular resistance (PVR), was calculated from bypass flow data. Next, the newly proposed index of PVR, the ratio of the time from peak to 50% decay and to 100% decay (RT50), was calculated through waveform analysis. The values were then compared between the PRH and non-PRH groups. RESULTS: Twenty-seven of the 52 patients met the inclusion criteria. Fourteen of these 27 patients showed PRH. The RT50, but not the PI, was significantly higher in the PRH group. Linear regression analysis revealed a significant correlation between the RT50 and PI. In the receiver operating characteristic for predicting PRH, the area under the curve of RT50 was 0.750, with a cutoff value of 0.255, a sensitivity of 0.928, and a specificity of 0.500. CONCLUSIONS: The RT50 obtained from waveform analysis is associated with PVR and can be useful for the early detection of PRH in patients with MMD.

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Experimental rat models of stroke and hemorrhage are important tools to investigate cerebrovascular disease pathophysiology mechanisms, yet how significant patterns of functional impairment induced in various models of stroke are related to changes in connectivity at the level of neuronal populations and mesoscopic parcellations of rat brains remain unresolved. To address this gap in knowledge, we employed two middle cerebral artery occlusion models and one intracerebral hemorrhage model with variant extent and location of neuronal dysfunction. Motor and spatial memory function was assessed and the level of hippocampal activation via Fos immunohistochemistry. Contribution of connectivity change to functional impairment was analyzed for connection similarities, graph distances and spatial distances as well as the importance of regions in terms of network architecture based on the neuroVIISAS rat connectome. We found that functional impairment correlated with not only the extent but also the locations of the injury among the models. In addition, via coactivation analysis in dynamic rat brain models, we found that lesioned regions led to stronger coactivations with motor function and spatial learning regions than with other unaffected regions of the connectome. Dynamic modeling with the weighted bilateral connectome detected changes in signal propagation in the remote hippocampus in all 3 stroke types, predicting the extent of hippocampal hypoactivation and impairment in spatial learning and memory function. Our study provides a comprehensive analytical framework in predictive identification of remote regions not directly altered by stroke events and their functional implication.

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BACKGROUND: Hemifacial spasms (HFSs) complicated by intracranial aneurysms are rare. Recently, endovascular treatment has been widely used for this disease entity and can allow the cessation of intracranial aneurysm arterial pulsation, leading to recovery from the HFS. Here, the authors present a case of HFS associated with an ipsilateral posterior inferior cerebellar artery (PICA) aneurysm successfully treated with open surgery. OBSERVATIONS: A 68-year-old woman was annually followed-up for an incidentally found right PICA aneurysm. Over 3 years, the PICA aneurysm gradually increased in size, which eventually led to right HFS. An axial fast spoiled gradient-recalled echo sequence with gadolinium enhancement showed the PICA aneurysm compressing the root exit zone (REZ), which was attributed as the cause of the HFS. However, a fusion image of the three-dimensional T1-weighted fast spin-echo sequence and magnetic resonance angiogram clearly showed a direct contact between the REZ and the anterior inferior cerebellar artery (AICA), which was located at the apex of the PICA aneurysm. Intraoperatively, the AICA was found compressing the REZ; hence, microvascular decompression with aneurysmal clipping was performed. The HFS resolved immediately after surgery. LESSONS: In cases of HFS associated with an ipsilateral intracranial aneurysm, a detailed neuroradiological assessment to identify the responsible lesion is important to use the most optimal treatment of choice.

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BACKGROUND: Moyamoya disease (MMD) is linked to the formation of intracranial aneurysms. The authors recently observed an effective use of magnetic resonance vessel wall imaging (MR-VWI) to detect de novo unruptured MMD-associated microaneurysms. OBSERVATIONS: The authors describe a 57-year-old female who was diagnosed with MMD 6 years ago after suffering a left putaminal hemorrhage. MR-VWI revealed point-like enhancement in the right posterior paraventricular region during the annual follow-up. On the T2-weighted image, this lesion was surrounded by high intensity. Angiography revealed a microaneurysm in the periventricular anastomosis. Right combined revascularization surgery was performed to prevent future hemorrhagic events. Another de novo circumferential enhanced lesion on MR-VWI appeared in the left posterior periventricular region 3 months after surgery. Angiography revealed that the enhanced lesion was a de novo microaneurysm on the periventricular anastomosis. The left combined revascularization surgery went well. The bilateral microaneurysms vanished on follow-up angiography. LESSONS: Unruptured MMD-associated microaneurysms on the periventricular anastomosis can be detected using MR-VWI. Revascularization surgery can eliminate microaneurysms by reducing hemodynamic stress on the periventricular anastomosis.

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BACKGROUND: Posterior cerebral artery (PCA) dissecting aneurysms commonly occur in the proximal PCA and are considered rare. The treatment of proximal PCA dissecting aneurysms is challenging because of the existence of perforators supplying the vital neural structures. Recently, endovascular intervention has been used; however, concerns for ischemic or hemorrhagic complications exist. OBSERVATIONS: A 54-year-old woman presented with subarachnoid hemorrhage due to dissecting aneurysm rupture at the P1-P2 junction of the PCA. The thalamoperforating artery (TPA) and medial posterior choroidal artery (MPchA) originated from the proximal end and the distal end of the aneurysm, respectively. Additionally, the posterior communicating artery (PcomA) connected with the dissected segment. To preserve these perforators, we performed surgical trapping combined with superficial temporal artery (STA) PCA anastomosis. Clips were applied for trapping the proximal and distal end of the aneurysm, with preservation of the TPA and MPchA origin. PcomA was left open for blood flow preservation to the perforators directly arising from the aneurysm. The postoperative course was uneventful, and the patient was discharged. LESSONS: Surgical trapping using STA-PCA bypass could be a treatment of choice for proximal PCA dissecting aneurysms, considering its potential for cure and prevention of ischemic complications.

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Infectious intracranial aneurysms(IIAs)are rare cerebrovascular complications of systemic infections induced by microbial infiltration and degradation of the arterial vessel wall. Prospective or population-wide studies of the epidemiology, natural history, or management of IIAs have not been conducted. In this study, we present the epidemiological and angiographical features, management, and outcomes of IIAs based on published case series and retrospective studies. Most IIAs were small in size(< 5 mm), with aneurysms located in the middle cerebral artery followed by the posterior cerebral artery. Endovascular interventions for IIAs have increased since coils, liquid embolic materials, and microcatheter became more sophisticated, allowing them to reach more distal branches. Open surgery is still required in cases with large clots or in cases involving branches feeding the eloquent areas, which cannot be sacrificed. These multimodal approaches for managing IIAs have achieved satisfactory results. Septic cavernous sinus thrombosis is also a rare, life-threatening complication of head and neck infections. Several antibiotics and antivirals are used in combination with anticoagulants. However, no consensus has been reached because of a lack of randomized controlled trials and large population-based studies.

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INTRODUCTION: Surgical revascularization prevents cerebral ischemic attack by improving cerebral blood flow (CBF) in both adult and pediatric patients with moyamoya disease (MMD). Uneven hemodynamic changes, including local cerebral hyperperfusion and remote ischemia, can cause delayed intracerebral hemorrhage and perioperative infarctions in adult MMD patients, but the characteristic hemodynamic pattern among pediatric MMD patients after revascularization surgery is poorly understood. METHODS: This study included 16 consecutive pediatric MMD patients (age, 6-16 years; mean age, 11.3) undergoing superficial temporal artery-middle cerebral artery anastomosis combined with encephalo-duro-myo-synangiosis on 21 affected hemispheres. Perioperative management was conducted by aspirin administration and strict blood pressure control (110-130 mm Hg). We prospectively performed N-isopropyl-p-[123I] iodoamphetamine single-photon emission computed tomography on postoperative days (POD) 1 and 7 and analyzed the temporal changes in perioperative hemodynamics. RESULTS: Four patients (19.0%, 4/21) exhibited immediate CBF improvement from POD 1, which was classified as "immediate redistribution pattern." In contrast, 9 (42.9%, 9/21) demonstrated transient hemispheric global hypoperfusion at POD 1 and subsequent CBF improvement at POD 7, which was defined as "transient hypoperfusion pattern." Although 8 patients, including 4 with "transient hypoperfusion pattern" (44.4, 4/9), developed mild transient neurological deterioration in the acute stage, it resolved in all 21 patients, and there were no permanent neurological deficits. DISCUSSION/CONCLUSIONS: This study revealed that the "transient hypoperfusion pattern" after revascularization surgery is relatively common among pediatric MMD patients, and its outcome is favorable under strict perioperative management.

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Intracranial aneurysm rupture is the main fatal complication of coil embolization for an intracranial aneurysm performed in conjunction with systemic heparinization. We answered five clinical questions about anesthesia, systemic heparinization, intraoperative aneurysmal rupture, the balloon-assisted technique, and the next step of initial response in case of aneurysmal rupture. It is crucial to understand when and why intraoperative aneurysmal rupture occurs to reduce its mortality rate. In cases of intraoperative problems, never pull the microcatheter or coil when perforating an aneurysm; lowering blood pressure, administering protamine for the reversal of heparin, and occluding blood flow into an aneurysm by inflating balloon(s) will help in the treatment. It is our pleasure that this chapter will help in your daily care.

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OBJECTIVE: Coil embolization with Y stenting is recognized as a suitable treatment for complex wide-necked aneurysms. Y stenting comprises crossing-Y stenting, in which a stent is passed through the interstices of another stent, and kissing-Y stenting, in which 2 stents are arranged in parallel. The purpose of this study was to elucidate how to distinguish between use of the 2 Y-stenting techniques. METHODS: Clinical and angiographic data of patients who underwent coil embolization with Y stenting at our department from 2015 to 2019 were retrospectively analyzed. Basic characteristics, endovascular procedure, complications, and outcomes were compared between kissing-Y and crossing-Y stenting groups. RESULTS: Thirty-eight intracranial aneurysms in 38 consecutive patients were included in this study. Nineteen patients (50%) were treated with coil embolization with kissing-Y stenting and 19 (50%) with crossing-Y. Endovascular procedures were successfully performed in all but 1 patient, in the kissing-Y group, who had stent migration. One hemorrhage (2.6%) recurred 12 months after coiling with kissing-Y stenting. Angiographic follow-up (mean, 15.8 months) was available in 35 patients. Adequate occlusion was shown in 14 patients (77.8%) and 13 patients (76.5%) in the kissing-Y and crossing-Y groups, respectively. Larger, wider-necked, and more proximal aneurysms were treated with kissing-Y stenting than with crossing-Y stenting, although there were no significant differences between the groups in complication rates or clinical outcomes. CONCLUSIONS: Kissing-Y and crossing-Y stenting of intracranial aneurysms were both feasible and yielded reasonable angiographic and clinical results. The choice between the kissing-Y or crossing-Y-stenting technique should be decided according to the angioarchitecture of targeted aneurysms.

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We investigated whether type 2 diabetes mellitus (T2DM), a risk factor of stroke, affects the level of scavenger receptor CD36 and the uptake of its ligand, oxidized LDL (oxLDL); and whether pioglitazone, a drug that enhances CD36, promotes oxLDL uptake. Compared to normoglycemic db/+ mice, adult db/db mice showed a pronounced reduction in surface CD36 expression on myeloid cells from the blood, brain, and bone marrow as detected by flow cytometry, which correlated with elevated plasma soluble-CD36 as determined by ELISA. Increased CD36 expression was found in brain macrophages and microglia of both genotypes 7 days after ischemic stroke. In juvenile db/db mice, prior to obesity and hyperglycemia, only a mild reduction of surface CD36 was found in blood neutrophils, while all other myeloid cells showed no difference relative to the db/+ strain. In vivo, oral pioglitazone treatment for four weeks increased CD36 levels on myeloid cells in db/db mice. In vitro, uptake of oxLDL by bone marrow derived macrophages (BMDMs) of db/db mice was reduced relative to db/+ mice in normal glucose medium. OxLDL uptake inversely correlated with glucose levels in the medium in db/+ BMDMs. Furthermore, pioglitazone restored oxLDL uptake by BMDMs from db/db mice cultured in high glucose. Our data suggest that T2DM is associated with reduced CD36 on adult myeloid cells, and pioglitazone enhances CD36 expression in db/db cells. T2DM or high glucose reduces oxLDL uptake while pioglitazone enhances oxLDL uptake. Our findings provide new insight into the mechanism by which pioglitazone may be beneficial in the treatment of insulin resistance.

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The leptomeningeal collateral status is an independent predictor of stroke outcome. By means of optical coherent tomography angiography to compare two mouse strains with different extent of native leptomeningeal collateralization, we determined the spatiotemporal dynamics of collateral flow and downstream hemodynamics following ischemic stroke. A robust recruitment of leptomeningeal collateral flow was detected immediately after middle cerebral artery (MCA) occlusion in C57BL/6 mice, with continued expansion over the course of seven days. In contrast, little collateral recruitment was seen in Balb/C mice during- and one day after MCAO, which coincided with a greater infarct size and worse functional outcome compared to C57BL/6, despite a slight improvement of cortical perfusion seven days after MCAO. Both strains of mice experienced a reduction of blood flow in the penetrating arterioles (PA) by more than 90% 30-min after dMCAO, although the decrease of PA flow was greater and the recovery was less in the Balb/C mice. Further, Balb/C mice also displayed a prolonged greater heterogeneity of capillary transit time after dMCAO in the MCA territory compared to C57BL/6 mice. Our data suggest that the extent of native leptomeningeal collaterals affects downstream hemodynamics with a long lasting impact in the microvascular bed after cortical stroke.

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Cranial bone defects are a major issue in the field of neurosurgery, and improper management of such defects can cause cosmetic issues as well as more serious infections and inflammation. Several strategies exist to manage these defects clinically, but most rely on synthetic materials that are prone to complications; thus, a bone regenerative approach would be superior. We tested a material (octacalcium phosphate collagen composite [OCP/Col]) that is known to enhance bone regeneration in a skull defect model in rats. Using a critical-sized rat skull defect model, OCP/Col was implanted in rats with an intact dura or with a partial defect of the dura. The results were compared with those in a no-treatment group over the course of 12 weeks using computed tomographic and histological analysis. OCP/Col enhanced bone regeneration, regardless of whether there was a defect of the dura. OCP/Col can be used to treat skull defects, even when the dura is injured or removed surgically, via bone regeneration with enhanced resorption of OCP/Col, thus limiting the risk of infection greatly.

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We report an adult moyamoya disease (MMD) patient who developed persistent local vasogenic edema with dynamic change in the regional cerebral blood flow after left superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. A 49-year-old woman with ischemic-onset MMD underwent left STA-MCA anastomosis. Magnetic resonance (MR) imaging of fluid-attenuated inversion recovery 1 day after surgery revealed an asymptomatic local high-signal-intensity lesion at the site of anastomosis, and MR angiography demonstrated apparently patent STA-MCA bypass. Due to the increased apparent diffusion coefficient value, we diagnosed the lesion as vasogenic edema. A significant increase in focal cerebral blood flow (CBF) at the site of the anastomosis was observed on N-isopropyl-p-[123I] iodoamphetamine single-photon emission computed tomography (123I-IMP-SPECT) (139.8%; compared with the preoperative value). Under strict blood pressure control (systolic blood pressure under 130 mmHg), the patient remained asymptomatic during the entire peri-operative period, but the 123I-IMP-SPECT 7 days after surgery suggested paradoxical CBF decrease (72.9%). Based on this finding, we allow the patient to be maintained under normotensive condition (∼160 mmHg), which recovered the CBF (115.0%) 14 days after surgery. Vasogenic edema remained during the entire peri-operative period, but completely disappeared 83 days after surgery. Local vasogenic edema formation due to cerebral hyperperfusion is not uncommon after STA-MCA anastomosis for adult MMD, but dynamic CBF change at the site of persistent local vasogenic edema after STA-MCA anastomosis is extremely rare. We recommend serial CBF measurement in the acute stage after revascularization surgery for MMD, especially when MR imaging demonstrates local signal intensity change.

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BACKGROUND: Perioperative embolic stroke is one of the most serious complications during carotid artery stenting (CAS). Proprotein convertase subtilisin/kexin type 9 inhibitor (PCSK9i) is a low-density lipoprotein-lowering drug that inhibits proprotein convertase subtilisin/kexin type 9, which normally binds to the low-density lipoprotein cholesterol (LDL-C) receptor. Its combination with statin significantly decreases LDL-C levels. PCSK9i is expected to achieve lower LDL-C levels than single use of statin. This study aimed to investigate whether perioperative PCSK9i administration stabilizes carotid artery plaque and reduces perioperative complications of CAS. METHODS: Nine patients with symptomatic stenosis (North American Symptomatic Carotid Endarterectomy Trial [NASCET] 50%) or asymptomatic stenosis (NASCET ≥ 80%) were included. PCSK9i was administered at least twice (once in 2 weeks) in the outpatient clinic before CAS. Perioperative complications; results from blood tests, magnetic resonance imaging (MRI), magnetic resonance angiography, and carotid ultrasonography (US); and modified Rankin scale score at discharge were assessed. RESULTS: High intensity on diffusion-weighted imaging was not observed in 8 patients. Changes in carotid plaque characteristics were found with MRI and/or carotid US in 7 patients. The plaque to muscle ratio decreased in 3 patients. The carotid plaque became hyperechoic in 2 patients, and the fibrous cap was seen more clearly on carotid US. Two patients had findings of stabilized plaque on MRI and carotid US, which indicates that plaque transformation was more stable. CONCLUSIONS: Lowering LDL-C level could reduce ischemic complications, and low LDL-C level affects plaque stability and antithrombus formation. PCSK9i can possibly stabilize carotid plaque and reduce perioperative complications of CAS.

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BACKGROUND: Circumferential enhancement along the aneurysm wall (CEAW) by magnetic resonance (MR) vessel wall imaging has been reported to be a useful indicator for the biological activity of intracranial aneurysms such as growth and rupture. However, the significance of CEAW in vertebral artery dissection (VAD) has not been examined in detail. We quantitatively analyzed CEAW on VAD focusing on the differences in the clinical onset type. METHODS: The subjects were 37 patients diagnosed with VAD who were evaluated by MR imaging in the acute phase of onset between January 2014 and May 2019. The clinical onset of VAD was categorized into 3 subtypes: (1) incidentally detected (incidental group), (2) sudden headache without cerebral ischemia and/or intracranial hemorrhage (headache group), and (3) hemorrhagic onset (hemorrhage group). Three-dimensional T1-weighted fast spin echo sequences were obtained before and after contrast material injection, and the contrast ratio (CR) of the aneurysm wall against the pituitary stalk was calculated as the indicator of CEAW. RESULTS: The CR values of VAD in the hemorrhage group were significantly higher than those in the headache group (0.95 vs. 0.65, p < 0.05), and the headache group had significantly higher CR values than the incidental group (0.65 vs. 0.56, p < 0.05). On receiver operating characteristic curve analysis, the optimal cutoff value of CR to distinguish the hemorrhage group from the headache group was 0.83 and that to distinguish the headache group from the incidental group was 0.61. CONCLUSION: The extent of CEAW precisely reflected the deleterious impact of VAD in the acute stage, including hemorrhagic presentation. The predictive value of CEAW for the prognosis of unruptured VAD should be evaluated in future studies.

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Triggering receptor expressed on myeloid cells-2 (TREM2) is an innate immune receptor that promotes phagocytosis by myeloid cells such as microglia and macrophages. We previously showed that TREM2 deficiency worsened outcomes from experimental stroke and impeded phagocytosis. However, myeloid cells participating in stroke pathology include both brain resident microglia and circulating macrophages. We now clarify whether TREM2 on brain microglia or circulating macrophages contribute to its beneficial role in ischemic stroke by generating bone marrow (BM) chimeric mice. BM chimera mice from TREM2 knockout (KO) or wild type (Wt) mice were used as donor and recipient mice. Mice were subjected to experimental stroke, and neurological function and infarct volume were assessed. Mice with intact TREM2 in brain microglia showed better neurological recovery and reduced infarct volumes, compared with mice lacking microglial TREM2. Myeloid cell activation and numbers of phagocytes were decreased in mice lacking brain TREM2, compared with mice with intact brain TREM2. These results suggest that TREM2 expression is important for post-stroke recovery, and that TREM2 expression on brain resident microglia is more essential to this recovery, than that of circulating macrophages. These findings might suggest a new therapeutic target for cerebrovascular diseases.

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We performed metabolomic analyses of mouse brain using a transient middle cerebral artery occlusion (tMCAO) model with Matrix Assisted Laser Desorption/Ionization (MALDI)-mass spectrometry imaging (MSI) to reveal metabolite changes after cerebral ischemia. We selected and analyzed three metabolites, namely creatine (Cr), phosphocreatine (P-Cr), and ceramides (Cer), because these metabolites contribute to cell life and death. Eight-week-old male C57BL/6J mice were subjected to tMCAO via the intraluminal blockade of the middle cerebral artery (MCA) and reperfusion 60 min after the induction of ischemia. Each mouse was randomly assigned to one of the three groups; the groups were defined by the survival period after reperfusion: control, 1 h, and 24 h. Corrected samples were analyzed using MALDI-MSI. Results of MSI analysis showed the presence of several ionized substances and revealed spatial changes in some metabolites identified as precise substances, including Cr, P-Cr, Cer d18:1/18:0, phosphatidylcholine, L-glutamine, and L-histidine. Cr, P-Cr, and Cer d18:1/18:0 were changed after tMCAO, and P-Cr and Cer d18:1/18:0 accumulated over time in ischemic cores and surrounding areas following ischemia onset. The upregulation of P-Cr and Cer d18:1/18:0 was detected 1 h after tMCAO when no changes were evident on hematoxylin and eosin staining and immunofluorescence assay. P-Cr and Cer d18:1/18:0 can serve as neuroprotective therapies because they are biomarker candidates for cerebral ischemia.

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Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with an unknown etiology and is characterized by an abnormal vascular network at the base of the brain. Recent studies identified the RNF213 gene (RNF213) as an important susceptibility gene for MMD; however, the mechanisms underlying the RNF213 abnormality related to MMD have not yet been elucidated. We previously reported that Rnf213-deficient mice and Rnf213 p. R4828K knock-in mice did not spontaneously develop MMD, indicating the importance of secondary insults in addition to genetic factors in the pathogenesis of MMD. The most influential secondary insult is considered to be an immunological reaction because RNF213 is predominantly expressed in immunological tissues. Therefore, we herein attempted to evaluate the role of an immunological stimulation as a supplementary insult to the target disruption of RNF213 in the pathophysiology of MMD. Rnf213-deficient mice were treated with strong immunological adjuvants including muramyl dipeptide (MDP)-Lys (L18), and then underwent time-sequential magnetic resonance angiography (MRA) up to 40 weeks of age. The results obtained did not reveal any characteristic finding of MMD, and no significant difference was observed in MRA findings or the anatomy of the circle of Willis between Rnf213-deficient mice and wild-type mice after the administration of MDP-Lys (L18). The ratio of regulatory T cells after the administration of MDP-Lys (L18) was significantly decreased in Rnf213-deficient mice (p<0.01), suggesting the potential role of the RNF213 abnormality in the differentiation of regulatory T cells. Although the mechanisms underlying the development of MMD currently remain unclear, the RNF213 abnormality may compromise immunological self-tolerance, thereby contributing to the development of MMD.

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