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MRI techniques to assess collaterals are rapidly being developed, and may provide insight into collateral perfusion. The combination of collateral images derived from pretreatment MRP source data and reperfusion status is a robust predictor of outcomes in acute ischemic stroke.

We prospectively recruited patients >18 years of age with MMD admitted to the tertiary, university stroke center between January 2008 and Background and Purpose-Moyamoya disease (MMD) is a unique cerebrovascular disease characterized by the progressive stenosis of large intracranial arteries and a hazy network of basal collaterals, called moyamoya vessels. Although hemodynamic studies have been applied in MMD patients, the mechanisms of stroke in MMD are still unclear. The present study evaluated the infarct pattern and collateral status using multimodal magnetic resonance imaging in MMD patients. Methods-Adult MMD patients with acute ischemic stroke were prospectively recruited, and infarct pattern on diffusionweighted imaging was evaluated. A collateral flow map, derived from magnetic resonance perfusion-weighted imaging data, was generated through automatic postprocessing, and collateral status was assigned into 3 grades. Transcranial Doppler monitoring was performed to detect microembolic signals in selected patients. Results-A total of 67 hemispheres (31 patients with bilateral and 5 patients with unilateral MMD) were analyzed. Most patients (83.7%) showed embolic pattern and rarely deep (9.3%) or hemodynamic infarct pattern (7.0%) on diffusionweighted imaging. Most cases (86%) showed good collateral status, and few patients with acute infarcts of embolic pattern showed poor collateral status (n=7). One third (31.6%) of patients who underwent transcranial Doppler monitoring showed microembolic signals. Conclusions-In the studied population of adult MMD patients, embolic phenomenon played an important role in ischemic stroke. Therapeutic strategies against thromboembolism, as well as collateral enhancing strategies targeting improvement of hemodynamic status or increased washout of emboli, are warranted.

SE-BOLD fMRI improves spatial specificity to microvessels compared to GE-BOLD at both fields. BOLD sensitivity is similar at the both fields and can be improved at ultrahigh fields only for thermal-noise-dominant ultrahigh-resolution fMRI.

Stroke induces complex and dynamic, local and systemic changes including inflammatory reactions, immune responses, and repair and recovery processes. Mesenchymal stem cells (MSCs) have been shown to enhance neurological recovery after stroke. We hypothesized that serum factors play a critical role in the activation of bone marrow (BM) MSCs after stroke such as by increasing proliferation, paracrine effects, and rejuvenation. Human MSCs (hMSCs) were grown in fetal bovine serum (FBS), normal healthy control serum (NS), or stroke patient serum (SS). MSCs cultured in growth medium with 10% SS or NS exhibited higher proliferation indices than those cultured with FBS (P < 0.01). FBS-, NS-, and SS-hMSCs showed differences in the expression of trophic factors; vascular endothelial growth factor, glial cell–derived neurotrophic factor, and fibroblast growth factor were densely expressed in samples cultured with SS (P < 0.01). In addition, SS-MSCs revealed different cell cycle– or aging-associated messenger RNA expression in a later passage, and β-galactosidase staining showed the senescence of MSCs observed during culture expansion was lower in MSCs cultured with SS than those cultured with NS or FBS (P < 0.01). Several proteins related to the activity of receptors, growth factors, and cytokines were more prevalent in the serum of stroke patients than in that of normal subjects. Neurogenesis and angiogenesis were markedly increased in rats that had received SS-MSCs (P < 0.05), and these rats showed significant behavioral improvements (P < 0.01). Our results indicate that stroke induces a process of recovery via the activation of MSCs. Culture methods for MSCs using SS obtained during the acute phase of a stroke could constitute a novel MSC activation method that is feasible and efficient for the neurorestoration of stroke.

Background and Purpose-Good collateral flow is an important predictor for favorable responses to recanalization therapy and successful outcomes after acute ischemic stroke. Magnetic resonance perfusion-weighted imaging (MRP) is widely used in patients with stroke. However, it is unclear whether the perfusion parameters and thresholds would predict collateral status. The present study evaluated the relationship between hypoperfusion severity and collateral status to develop a predictive model for good collaterals using MRP parameters. Methods-Patients who were eligible for recanalization therapy that underwent both serial diffusion-weighted imaging and serial MRP were enrolled into the study. A collateral flow map derived from MRP source data was generated through automatic postprocessing. Hypoperfusion severity, presented as proportions of every 2-s Tmax strata to the entire hypoperfusion volume (Tmax≥2 s), was compared between patients with good and poor collaterals. Prediction models for good collaterals were developed with each Tmax strata proportion and cerebral blood volumes. Results-Among

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Revascularization therapies have been established as the treatment mainstay for acute ischemic stroke. However, a substantial number of patients are either ineligible for revascularization therapy, or the treatment fails or is futile. At present, non-contrast computed tomography is the first-line neuroimaging modality for patients with acute stroke. The use of magnetic resonance imaging (MRI) to predict the response to early revascularization therapy and to identify patients for delayed treatment is desirable. MRI could provide information on stroke pathophysiologies, including the ischemic core, perfusion, collaterals, clot, and blood–brain barrier status. During the past 20 years, there have been significant advances in neuroimaging as well as in revascularization strategies for treating patients with acute ischemic stroke. In this review, we discuss the role of MRI and post-processing, including machine-learning techniques, and recent advances in MRI-based triage for revascularization therapies in acute ischemic stroke.