Defective sphingosine 1-phosphate receptor 1 (S1P1) phosphorylation exacerbates TH17-mediated autoimmune neuroinflammation.

Sphingosine 1-phosphate (S1P) signaling regulates lymphocyte egress from lymphoid organs into systemic circulation. The sphingosine phosphate receptor 1 (S1P1) agonist FTY-720 (Gilenya) arrests immune trafficking and prevents multiple sclerosis (MS) relapses. However, alternative mechanisms of S1P-S1P1 signaling have been reported. Phosphoproteomic analysis of MS brain lesions revealed S1P1 phosphorylation on S351, a residue crucial for receptor internalization. Mutant mice harboring an S1pr1 gene encoding phosphorylation-deficient receptors (S1P1(S5A)) developed severe experimental autoimmune encephalomyelitis (EAE) due to autoimmunity mediated by interleukin 17 (IL-17)-producing helper T cells (TH17 cells) in the peripheral immune and nervous system. S1P1 directly activated the Jak-STAT3 signal-transduction pathway via IL-6. Impaired S1P1 phosphorylation enhances TH17 polarization and exacerbates autoimmune neuroinflammation. These mechanisms may be pathogenic in MS.

Incidence and Outcomes of Posterior Circulation Involvement in Moyamoya Disease.

BACKGROUND: Moyamoya disease (MMD) is a progressive, occlusive disease of the internal carotid arteries and their proximal branches, with the subsequent development of an abnormal vascular network that is rupture-prone. Steno-occlusive changes in the posterior cerebral arteries (PCAs) may contribute to worsened outcomes in patients with MMD; however, there is little information on the incidence and natural history of posterior circulation MMD (PCMMD). We describe clinical PCMMD characteristics in a large cohort of patients with MMD. METHODS: We retrospectively reviewed patients with MMD treated between 1991 and 2019 at a large academic medical center. Demographics, perioperative outcomes, and radiological phenotypes were recorded for 770 patients. PCA disease was graded as either 0 (no disease), 1 (mild), 2 (moderate), or 3 (severe or occluded) based on cerebral angiography. Patients with angiographically confirmed MMD diagnosis with at least 6 months follow-up and completion of revascularization surgery were included; patients with intracranial atherosclerosis, intracranial dissection, vasculitis, and undefined inflammatory processes were excluded. The presence of stenosis/occlusion was graded radiographically to assess for disease progression and the prevalence of risk factors related to reduced progression-free survival. RESULTS: In all, 686 patients met the inclusion criteria, with PCA disease identified in 282 (41.1%) patients. Of those 282 patients with PCMMD, disease severity ranged from 99 (35.1%) with mild, 72 (25.5%) with moderate, and 111 (39.4%) with severe. The total number of postoperative complications was significantly associated with PCMMD severity (P=0.0067). Additionally, PCMMD severity correlated with worse postoperative modified Rankin Scale scores (P<0.0001). At a mean follow-up of 6.0±3.9 (range, 0.1-25.0) years, a total of 60 (12.6%) patients showed new/worsening PCMMD. The overall postoperative, progression-free survival in patients with PCMMD was 95.4% at 1 year, 82.4% at 3 years, 68.8% at 5 years, and 28.3% at 10 years, with prognostic factors for progression including preoperative PCMMD status, history of tobacco use, and hypertension (P<0.0001, P<0.001, and P<0.0001, respectively). CONCLUSIONS: PCA disease involvement in MMD is associated with higher rates of ischemic perioperative complications and worsened functional outcomes, likely due to reduced collateral flow. Ten-year progression of PCA disease is highly likely and should be monitored throughout follow-up; future studies will assess the impact of PCA disease progression on long-term outcomes.

Short- and Long-Term MRI Assessed Hemodynamic Changes in Pediatric Moyamoya Patients After Revascularization.

BACKGROUND: Cerebrovascular reserve (CVR) reflects the capacity of cerebral blood flow (CBF) to change following a vasodilation challenge. Decreased CVR is associated with a higher stroke risk in patients with cerebrovascular diseases. While revascularization can improve CVR and reduce this risk in adult patients with vasculopathy such as those with Moyamoya disease, its impact on hemodynamics in pediatric patients remains to be elucidated. Arterial spin labeling (ASL) is a quantitative MRI technique that can measure CBF, CVR, and arterial transit time (ATT) non-invasively. PURPOSE: To investigate the short- and long-term changes in hemodynamics after bypass surgeries in patients with Moyamoya disease. STUDY TYPE: Longitudinal. POPULATION: Forty-six patients (11 months-18 years, 28 females) with Moyamoya disease. FIELD STRENGTH/SEQUENCE: 3-T, single- and multi-delay ASL, T1-weighted, T2-FLAIR, 3D MRA. ASSESSMENT: Imaging was performed 2 weeks before and 1 week and 6 months after surgical intervention. Acetazolamide was employed to induce vasodilation during the imaging procedure. CBF and ATT were measured by fitting the ASL data to the general kinetic model. CVR was computed as the percentage change in CBF. The mean CBF, ATT, and CVR values were measured in the regions affected by vasculopathy. STATISTICAL TESTS: Pre- and post-revascularization CVR, CBF, and ATT were compared for different regions of the brain. P-values <0.05 were considered statistically significant. RESULTS: ASL-derived CBF in flow territories affected by vasculopathy significantly increased after bypass by 41 ± 31% within a week. At 6 months, CBF significantly increased by 51 ± 34%, CVR increased by 68 ± 33%, and ATT was significantly reduced by 6.6 ± 2.9%. DATA CONCLUSION: There may be short- and long-term improvement in the hemodynamic parameters of pediatric Moyamoya patients after bypass surgery. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 2.

Pediatric Moyamoya Revascularization Perioperative Care: A Modified Delphi Study.

BACKGROUND: Surgical revascularization decreases the long-term risk of stroke in children with moyamoya arteriopathy but can be associated with an increased risk of stroke during the perioperative period. Evidence-based approaches to optimize perioperative management are limited and practice varies widely. Using a modified Delphi process, we sought to establish expert consensus on key components of the perioperative care of children with moyamoya undergoing indirect revascularization surgery and identify areas of equipoise to define future research priorities. METHODS: Thirty neurologists, neurosurgeons, and intensivists practicing in North America with expertise in the management of pediatric moyamoya were invited to participate in a three-round, modified Delphi process consisting of a 138-item practice patterns survey, anonymous electronic evaluation of 88 consensus statements on a 5-point Likert scale, and a virtual group meeting during which statements were discussed, revised, and reassessed. Consensus was defined as ≥ 80% agreement or disagreement. RESULTS: Thirty-nine statements regarding perioperative pediatric moyamoya care for indirect revascularization surgery reached consensus. Salient areas of consensus included the following: (1) children at a high risk for stroke and those with sickle cell disease should be preadmitted prior to indirect revascularization; (2) intravenous isotonic fluids should be administered in all patients for at least 4 h before and 24 h after surgery; (3) aspirin should not be discontinued in the immediate preoperative and postoperative periods; (4) arterial lines for blood pressure monitoring should be continued for at least 24 h after surgery and until active interventions to achieve blood pressure goals are not needed; (5) postoperative care should include hourly vital signs for at least 24 h, hourly neurologic assessments for at least 12 h, adequate pain control, maintaining normoxia and normothermia, and avoiding hypotension; and (6) intravenous fluid bolus administration should be considered the first-line intervention for new focal neurologic deficits following indirect revascularization surgery. CONCLUSIONS: In the absence of data supporting specific care practices before and after indirect revascularization surgery in children with moyamoya, this Delphi process defined areas of consensus among neurosurgeons, neurologists, and intensivists with moyamoya expertise. Research priorities identified include determining the role of continuous electroencephalography in postoperative moyamoya care, optimal perioperative blood pressure and hemoglobin targets, and the role of supplemental oxygen for treatment of suspected postoperative ischemia.

Acetazolamide-Challenged Arterial Spin Labeling Detects Augmented Cerebrovascular Reserve After Surgery for Moyamoya.

BACKGROUND: Cerebrovascular reserve (CVR) inversely correlates with stroke risk in children with Moyamoya disease and may be improved by revascularization surgery. We hypothesized that acetazolamide-challenged arterial spin labeling MR perfusion quantifies augmentation of CVR achieved by revascularization and correlates with currently accepted angiographic scoring criteria. METHODS: We retrospectively identified pediatric patients with Moyamoya disease or syndrome who received cerebral revascularization at ≤18 years of age between 2012 and 2019 at our institution. Using acetazolamide-challenged arterial spin labeling, we compared postoperative CVR to corresponding preoperative values and to postoperative perfusion outcomes classified by Matsushima grading. RESULTS: In this cohort, 32 patients (17 males) with Moyamoya underwent 29 direct and 16 indirect extracranial-intracranial bypasses at a median 9.7 years of age (interquartile range, 7.6-15.7). Following revascularization, median CVR increased within the ipsilateral middle cerebral artery territory (6.9 mL/100 g per minute preoperatively versus 16.5 mL/100 g per minute postoperatively, P<0.01). No differences were observed in the ipsilateral anterior cerebral artery (P=0.13) and posterior cerebral artery (P=0.48) territories. Postoperative CVR was higher in the ipsilateral middle cerebral artery territories of patients who achieved Matsushima grade A perfusion, in comparison to those with grades B or C (25.8 versus 17.5 mL, P=0.02). The method of bypass (direct or indirect) did not alter relative increases in CVR (8 versus 3.8 mL/100 g per minute, P=0.7). CONCLUSIONS: Acetazolamide-challenged arterial spin labeling noninvasively quantifies augmentation of CVR following surgery for Moyamoya disease and syndrome.

Unique Subtype of Microglia in Degenerative Thalamus After Cortical Stroke.

BACKGROUND AND PURPOSE: Stroke disrupts neuronal functions in both local and remotely connected regions, leading to network-wide deficits that can hinder recovery. The thalamus is particularly affected, with progressive development of neurodegeneration accompanied by inflammatory responses. However, the complexity of the involved inflammatory responses is poorly understood. Herein we investigated the spatiotemporal changes in the secondary degenerative thalamus after cortical stroke, using targeted transcriptome approach in conjunction with histology and flow cytometry. METHODS: Cortical ischemic stroke was generated by permanent occlusion of the left middle cerebral artery in male C57BL6J mice. Neurodegeneration, neuroinflammatory responses, and microglial activation were examined in naive and stroke mice at from poststroke days (PD) 1 to 84, in both ipsilesional somatosensory cortex and ipsilesional thalamus. NanoString neuropathology panel (780 genes) was used to examine transcriptome changes at PD7 and PD28. Fluorescence activated cell sorting was used to collect CD11c+ microglia from ipsilesional thalamus, and gene expressions were validated by quantitative real-time polymerase chain reaction. RESULTS: Neurodegeneration in the thalamus was detected at PD7 and progressively worsened by PD28. This was accompanied by rapid microglial activation detected as early as PD1, which preceded the neurodegenerative changes. Transcriptome analysis showed higher number of differentially expressed genes in ipsilesional thalamus at PD28. Notably, neuroinflammation was the top activated pathway, and microglia was the most enriched cell type. Itgax (CD11c) was the most significantly increased gene, and its expression was highly detected in microglia. Flow-sorted CD11c+ microglia from degenerative thalamus indicated molecular signatures similar to neurodegenerative disease-associated microglia; these included downregulated Tmem119 and CX3CR1 and upregulated ApoE, Axl, LpL, CSF1, and Cst7. CONCLUSIONS: Our findings demonstrate the dynamic changes of microglia after stroke and highlight the importance of investigating stroke network-wide deficits. Importantly, we report the existence of a unique subtype of microglia (CD11c+) with neurodegenerative disease-associated microglia features in the degenerative thalamus after stroke.

Arteriovenous Malformations-Current Understanding of the Pathogenesis with Implications for Treatment.

Arteriovenous malformations are a vascular anomaly typically present at birth, characterized by an abnormal connection between an artery and a vein (bypassing the capillaries). These high flow lesions can vary in size and location. Therapeutic approaches are limited, and AVMs can cause significant morbidity and mortality. Here, we describe our current understanding of the pathogenesis of arteriovenous malformations based on preclinical and clinical findings. We discuss past and present accomplishments and challenges in the field and identify research gaps that need to be filled for the successful development of therapeutic strategies in the future.

Predicting PET Cerebrovascular Reserve with Deep Learning by Using Baseline MRI: A Pilot Investigation of a Drug-Free Brain Stress Test.

Background Cerebrovascular reserve (CVR) may be measured by using an acetazolamide test to clinically evaluate patients with cerebrovascular disease. However, acetazolamide use may be contraindicated and/or undesirable in certain clinical settings. Purpose To predict CVR images generated from acetazolamide vasodilation with a deep learning network by using only images before acetazolamide administration. Materials and Methods Simultaneous oxygen 15 (15O)-labeled water PET/MRI before and after acetazolamide injection were retrospectively analyzed for patients with Moyamoya disease and healthy control participants from April 2017 to May 2019. Inputs to deep learning models were perfusion-based images (arterial spin labeling [ASL]), structural scans (T2 fluid-attenuated inversion-recovery, T1), and brain location. Two models, that is, 15O-labeled water PET cerebral blood flow (CBF) and MRI (PET-plus-MRI model) before acetazolamide administration and only MRI (MRI-only model) before acetazolamide administration, were trained and tested with sixfold cross-validation. The models learned to predict a voxelwise relative CBF change (rΔCBF) map by using rΔCBF measured with PET due to acetazolamide as ground truth. Quantitative analysis included image quality metrics (peak signal-to-noise ratio, root mean square error, and structural similarity index), as well as comparison between the various methods by using correlation and Bland-Altman analyses. Identification of vascular territories with impaired rΔCBF was evaluated by using receiver operating characteristic metrics. Results Thirty-six participants were included: 24 patients with Moyamoya disease (mean age ± standard deviation, 41 years ± 12; 17 women) and 12 age-matched healthy control participants (mean age, 39 years ± 16; nine women). The rΔCBF maps predicted by both deep learning models demonstrated better image quality metrics than did ASL (all P < .001 in patients) and higher correlation coefficient with PET than with ASL (PET-plus-MRI model, 0.704; MRI-only model, 0.690 vs ASL, 0.432; both P < .001 in patients). Both models also achieved high diagnostic performance in identifying territories with impaired rΔCBF (area under receiver operating characteristic curve, 0.95 for PET-plus-MRI model [95% confidence interval: 0.90, 0.99] and 0.95 for MRI-only model [95% confidence interval: 0.91, 0.98]). Conclusion By using only images before acetazolamide administration, PET-plus-MRI and MRI-only deep learning models predicted cerebrovascular reserve images without the need for vasodilator injection. © RSNA, 2020 Online supplemental material is available for this article.

Simultaneous phase-contrast MRI and PET for noninvasive quantification of cerebral blood flow and reactivity in healthy subjects and patients with cerebrovascular disease.

BACKGROUND: H215 O-positron emission tomography (PET) is considered the reference standard for absolute cerebral blood flow (CBF). However, this technique requires an arterial input function measured through continuous sampling of arterial blood, which is invasive and has limitations with tracer delay and dispersion. PURPOSE: To demonstrate a new noninvasive method to quantify absolute CBF with a PET/MRI hybrid scanner. This blood-free approach, called PC-PET, takes the spatial CBF distribution from a static H215 O-PET scan, and scales it to the whole-brain average CBF value measured by simultaneous phase-contrast MRI. STUDY TYPE: Observational. SUBJECTS: Twelve healthy controls (HC) and 13 patients with Moyamoya disease (MM) as a model of chronic ischemic disease. FIELD STRENGTH/SEQUENCES: 3T/2D cardiac-gated phase-contrast MRI and H215 O-PET. ASSESSMENT: PC-PET CBF values from whole brain (WB), gray matter (GM), and white matter (WM) in HCs were compared with literature values since 2000. CBF and cerebrovascular reactivity (CVR), which is defined as the percent CBF change between baseline and post-acetazolamide (vasodilator) scans, were measured by PC-PET in MM patients and HCs within cortical regions corresponding to major vascular territories. Statistical Tests: Linear, mixed effects models were created to compare CBF and CVR, respectively, between patients and controls, and between different degrees of stenosis. RESULTS: The mean CBF values in WB, GM, and WM in HC were 42 ± 7 ml/100 g/min, 50 ± 7 ml/100 g/min, and 23 ± 3 ml/100 g/min, respectively, which agree well with literature values. Compared with normal regions (57 ± 23%), patients showed significantly decreased CVR in areas with mild/moderate stenosis (47 ± 17%, P = 0.011) and in severe/occluded areas (40 ± 16%, P = 0.016). Data Conclusion: PC-PET identifies differences in cerebrovascular reactivity between healthy controls and cerebrovascular patients. PC-PET is suitable for CBF measurement when arterial blood sampling is not accessible, and warrants comparison to fully quantitative H215 O-PET in future studies. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;51:183-194.

Arterial-spin labeling MRI identifies residual cerebral arteriovenous malformation following stereotactic radiosurgery treatment.

BACKGROUND AND PURPOSE: Brain arteriovenous malformation (AVM) treatment by stereotactic radiosurgery (SRS) is effective, but AVM obliteration following SRS may take two years or longer. MRI with arterial-spin labeling (ASL) may detect brain AVMs with high sensitivity. We determined whether brain MRI with ASL may accurately detect residual AVM following SRS treatment. MATERIALS AND METHODS: We performed a retrospective cohort study of patients who underwent brain AVM evaluation by DSA between June 2010 and June 2015. Inclusion criteria were: (1) AVM treatment by SRS, (2) follow-up MRI with ASL at least 30 months after SRS, (3) DSA within 3 months of the follow-up MRI with ASL, and (4) no intervening AVM treatment between the MRI and DSA. Four neuroradiologists blindly and independently reviewed follow-up MRIs. Primary outcome measure was residual AVM indicated by abnormal venous ASL signal. RESULTS: 15 patients (12 females, mean age 29 years) met inclusion criteria. There were three posterior fossa AVMs and 12 supratentorial AVMs. Spetzler-Martin (SM) Grades were: SM1 (8%), SM2 (33%), SM3 (17%), SM4 (25%), and SM5 (17%). DSA demonstrated residual AVM in 10 patients. The pooled sensitivity, specificity, positive predictive value, and negative predictive value of venous ASL signal for predicting residual AVM were 100% (95% CI: 0.9-1.0), 95% (95% CI: 0.7-1.0), 98% (95% CI: 0.9-1.0), and 100% (95% CI: 0.8-1.0), respectively. High inter-reader agreement as found by Fleiss' Kappa analysis (k = 0.92; 95% CI: 0.8-1.0; P < 0.0001). CONCLUSIONS: ASL is highly sensitive and specific in the detection of residual cerebral AVM following SRS treatment.

Identifying Hypoperfusion in Moyamoya Disease With Arterial Spin Labeling and an [15O]-Water Positron Emission Tomography/Magnetic Resonance Imaging Normative Database.

Background and Purpose- Noninvasive imaging of brain perfusion has the potential to elucidate pathophysiological mechanisms underlying Moyamoya disease and enable clinical imaging of cerebral blood flow (CBF) to select revascularization therapies for patients. We used hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) technology to characterize the distribution of hypoperfusion in Moyamoya disease and its relationship to vessel stenosis severity, through comparisons with a normative perfusion database of healthy controls. Methods- To image CBF, we acquired [15O]-water PET as a reference and simultaneously acquired arterial spin labeling (ASL) MRI scans in 20 Moyamoya patients and 15 age-matched, healthy controls on a PET/MRI scanner. The ASL MRI scans included a standard single-delay ASL scan with postlabel delay of 2.0 s and a multidelay scan with 5 postlabel delays (0.7-3.0s) to estimate and account for arterial transit time in CBF quantification. The percent volume of hypoperfusion in patients (determined as the fifth percentile of CBF values in the healthy control database) was the outcome measure in a logistic regression model that included stenosis grade and location. Results- Logistic regression showed that anterior ( P<0.0001) and middle cerebral artery territory regions ( P=0.003) in Moyamoya patients were susceptible to hypoperfusion, whereas posterior regions were not. Cortical regions supplied by arteries with stenosis on MR angiography showed more hypoperfusion than normal arteries ( P=0.001), but the extent of hypoperfusion was not different between mild-moderate versus severe stenosis. Multidelay ASL did not perform differently from [15O]-water PET in detecting perfusion abnormalities, but standard ASL overestimated the extent of hypoperfusion in patients ( P=0.003). Conclusions- This simultaneous PET/MRI study supports the use of multidelay ASL MRI in clinical evaluation of Moyamoya disease in settings where nuclear medicine imaging is not available and application of a normative perfusion database to automatically identify abnormal CBF in patients.

Consensus Paper: Experimental Neurostimulation of the Cerebellum.

The cerebellum is best known for its role in controlling motor behaviors. However, recent work supports the view that it also influences non-motor behaviors. The contribution of the cerebellum towards different brain functions is underscored by its involvement in a diverse and increasing number of neurological and neuropsychiatric conditions including ataxia, dystonia, essential tremor, Parkinson's disease (PD), epilepsy, stroke, multiple sclerosis, autism spectrum disorders, dyslexia, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Although there are no cures for these conditions, cerebellar stimulation is quickly gaining attention for symptomatic alleviation, as cerebellar circuitry has arisen as a promising target for invasive and non-invasive neuromodulation. This consensus paper brings together experts from the fields of neurophysiology, neurology, and neurosurgery to discuss recent efforts in using the cerebellum as a therapeutic intervention. We report on the most advanced techniques for manipulating cerebellar circuits in humans and animal models and define key hurdles and questions for moving forward.

RNA-Sequencing Analysis Revealed a Distinct Motor Cortex Transcriptome in Spontaneously Recovered Mice After Stroke.

Background and Purpose- Many restorative therapies have been used to study brain repair after stroke. These therapeutic-induced changes have revealed important insights on brain repair and recovery mechanisms; however, the intrinsic changes that occur in spontaneously recovery after stroke is less clear. The goal of this study is to elucidate the intrinsic changes in spontaneous recovery after stroke, by directly investigating the transcriptome of primary motor cortex in mice that naturally recovered after stroke. Methods- Male C57BL/6J mice were subjected to transient middle cerebral artery occlusion. Functional recovery was evaluated using the horizontal rotating beam test. A novel in-depth lesion mapping analysis was used to evaluate infarct size and locations. Ipsilesional and contralesional primary motor cortices (iM1 and cM1) were processed for RNA-sequencing transcriptome analysis. Results- Cluster analysis of the stroke mice behavior performance revealed 2 distinct recovery groups: a spontaneously recovered and a nonrecovered group. Both groups showed similar lesion profile, despite their differential recovery outcome. RNA-sequencing transcriptome analysis revealed distinct biological pathways in the spontaneously recovered stroke mice, in both iM1 and cM1. Correlation analysis revealed that 38 genes in the iM1 were significantly correlated with improved recovery, whereas 74 genes were correlated in the cM1. In particular, ingenuity pathway analysis highlighted the involvement of cAMP signaling in the cM1, with selective reduction of Adora2a (adenosine receptor A2A), Drd2 (dopamine receptor D2), and Pde10a (phosphodiesterase 10A) expression in recovered mice. Interestingly, the expressions of these genes in cM1 were negatively correlated with behavioral recovery. Conclusions- Our RNA-sequencing data revealed a panel of recovery-related genes in the motor cortex of spontaneously recovered stroke mice and highlighted the involvement of contralesional cortex in spontaneous recovery, particularly Adora2a, Drd2, and Pde10a-mediated cAMP signaling pathway. Developing drugs targeting these candidates after stroke may provide beneficial recovery outcome.

Reduced Intravoxel Incoherent Motion Microvascular Perfusion Predicts Delayed Cerebral Ischemia and Vasospasm After Aneurysm Rupture.

BACKGROUND AND PURPOSE: Proximal artery vasospasm and delayed cerebral ischemia (DCI) after cerebral aneurysm rupture result in reduced cerebral perfusion and microperfusion and significant morbidity and mortality. Intravoxel incoherent motion (IVIM) magnetic resonance imaging extracts microvascular perfusion information from a multi-b value diffusion-weighted sequence. We determined whether decreased IVIM perfusion may identify patients with proximal artery vasospasm and DCI. METHODS: We performed a pilot retrospective cohort study of patients with ruptured cerebral aneurysms. Consecutive patients who underwent a brain magnetic resonance imaging with IVIM after ruptured aneurysm treatment were included. Patient demographic, treatment, imaging, and outcome data were determined by electronic medical record review. Primary outcome was DCI development with proximal artery vasospasm that required endovascular treatment. Secondary outcomes included mortality and clinical outcomes at 6 months. RESULTS: Sixteen patients (11 females, 69%; P=0.9) were included. There were no differences in age, neurological status, or comorbidities between patients who subsequently underwent endovascular treatment of DCI (10 patients; DCI+ group) and those who did not (6 patients; DCI- group). Compared with DCI- patients, DCI+ patients had decreased IVIM perfusion fraction f (0.09±0.03 versus 0.13±0.01; P=0.03), reduced diffusion coefficient D (0.82±0.05 versus 0.92±0.07×10-3 mm2/s; P=0.003), and reduced blood flow-related parameter fD* (1.18±0.40 versus 1.83±0.40×10-3 mm2/s; P=0.009). IVIM pseudodiffusion coefficient D* did not differ between DCI- (0.011±0.002) and DCI+ (0.013±0.005 mm2/s; P=0.4) patients. No differences in mortality or clinical outcome were identified. CONCLUSIONS: Decreased IVIM perfusion fraction f and blood flow-related parameter fD* correlate with DCI and proximal artery vasospasm development after cerebral aneurysm rupture.

Neurocognitive Performance After Cerebral Revascularization in Adult Moyamoya Disease.

BACKGROUND AND PURPOSE: Cerebral revascularization using EC-IC bypass is widely used to treat moyamoya disease, but the effects of surgery on cognition are unknown. We compared performance on formal neurocognitive testing in adults with moyamoya disease before and after undergoing direct EC-IC bypass. METHODS: We performed a structured battery of 13 neurocognitive tests on 84 adults with moyamoya disease before and 6 months after EC-IC bypass. The results were analyzed using reliable change indices for each test, to minimize test-retest variability and practice effects. RESULTS: Twelve patients (14%) showed significant decline postoperatively, 9 patients (11%) improved, and 63 patients (75%) were unchanged. Similar results were obtained when the analysis was confined to those who underwent unilateral (33) or bilateral (51) revascularization. CONCLUSIONS: The majority of patients showed neither significant decline nor improvement in neurocognitive performance after EC-IC bypass surgery. Uncomplicated EC-IC bypass seems not to be a risk factor for cognitive decline in this patient population.

Long-Delay Arterial Spin Labeling Provides More Accurate Cerebral Blood Flow Measurements in Moyamoya Patients: A Simultaneous Positron Emission Tomography/MRI Study.

BACKGROUND AND PURPOSE: Arterial spin labeling (ASL) MRI is a promising, noninvasive technique to image cerebral blood flow (CBF) but is difficult to use in cerebrovascular patients with abnormal, long arterial transit times through collateral pathways. To be clinically adopted, ASL must first be optimized and validated against a reference standard in these challenging patient cases. METHODS: We compared standard-delay ASL (post-label delay=2.025 seconds), multidelay ASL (post-label delay=0.7-3.0 seconds), and long-label long-delay ASL acquisitions (post-label delay=4.0 seconds) against simultaneous [15O]-positron emission tomography (PET) CBF maps in 15 Moyamoya patients on a hybrid PET/MRI scanner. Dynamic susceptibility contrast was performed in each patient to identify areas of mild, moderate, and severe time-to-maximum (Tmax) delays. Relative CBF measurements by each ASL scan in 20 cortical regions were compared with the PET reference standard, and correlations were calculated for areas with moderate and severe Tmax delays. RESULTS: Standard-delay ASL underestimated relative CBF by 20% in areas of severe Tmax delays, particularly in anterior and middle territories commonly affected by Moyamoya disease (P<0.001). Arterial transit times correction by multidelay acquisitions led to improved consistency with PET, but still underestimated CBF in the presence of long transit delays (P=0.02). Long-label long-delay ASL scans showed the strongest correlation relative to PET, and there was no difference in mean relative CBF between the modalities, even in areas of severe delays. CONCLUSIONS: Post-label delay times of ≥4 seconds are needed and may be combined with multidelay strategies for robust ASL assessment of CBF in Moyamoya disease.

Multiple Subsets of Brain Tumor Initiating Cells Coexist in Glioblastoma.

Brain tumor-initiating cells (BTICs) are self-renewing multipotent cells critical for tumor maintenance and growth. Using single-cell microfluidic profiling, we identified multiple subpopulations of BTICs coexisting in human glioblastoma, characterized by distinct surface marker expression and single-cell molecular profiles relating to divergent bulk tissue molecular subtypes. These data suggest BTIC subpopulation heterogeneity as an underlying source of intra-tumoral bulk tissue molecular heterogeneity, and will support future studies into BTIC subpopulation-specific therapies. Stem Cells 2016;34:1702-1707.

Enhanced phasic GABA inhibition during the repair phase of stroke: a novel therapeutic target.

Ischaemic stroke is the leading cause of severe long-term disability yet lacks drug therapies that promote the repair phase of recovery. This repair phase of stroke occurs days to months after stroke onset and involves brain remapping and plasticity within the peri-infarct zone. Elucidating mechanisms that promote this plasticity is critical for the development of new therapeutics with a broad treatment window. Inhibiting tonic (extrasynaptic) GABA signalling during the repair phase was reported to enhance functional recovery in mice suggesting that GABA plays an important function in modulating brain repair. While tonic GABA appears to suppress brain repair after stroke, less is known about the role of phasic (synaptic) GABA during the repair phase. We observed an increase in postsynaptic phasic GABA signalling in mice within the peri-infarct cortex specific to layer 5; we found increased numbers of α1 receptor subunit-containing GABAergic synapses detected using array tomography, and an associated increased efficacy of spontaneous and miniature inhibitory postsynaptic currents in pyramidal neurons. Furthermore, we demonstrate that enhancing phasic GABA signalling using zolpidem, a Food and Drug Administration (FDA)-approved GABA-positive allosteric modulator, during the repair phase improved behavioural recovery. These data identify potentiation of phasic GABA signalling as a novel therapeutic strategy, indicate zolpidem's potential to improve recovery, and underscore the necessity to distinguish the role of tonic and phasic GABA signalling in stroke recovery.

Optogenetic neuronal stimulation promotes functional recovery after stroke.

Clinical and research efforts have focused on promoting functional recovery after stroke. Brain stimulation strategies are particularly promising because they allow direct manipulation of the target area's excitability. However, elucidating the cell type and mechanisms mediating recovery has been difficult because existing stimulation techniques nonspecifically target all cell types near the stimulated site. To circumvent these barriers, we used optogenetics to selectively activate neurons that express channelrhodopsin 2 and demonstrated that selective neuronal stimulations in the ipsilesional primary motor cortex (iM1) can promote functional recovery. Stroke mice that received repeated neuronal stimulations exhibited significant improvement in cerebral blood flow and the neurovascular coupling response, as well as increased expression of activity-dependent neurotrophins in the contralesional cortex, including brain-derived neurotrophic factor, nerve growth factor, and neurotrophin 3. Western analysis also indicated that stimulated mice exhibited a significant increase in the expression of a plasticity marker growth-associated protein 43. Moreover, iM1 neuronal stimulations promoted functional recovery, as stimulated stroke mice showed faster weight gain and performed significantly better in sensory-motor behavior tests. Interestingly, stimulations in normal nonstroke mice did not alter motor behavior or neurotrophin expression, suggesting that the prorecovery effect of selective neuronal stimulations is dependent on the poststroke environment. These results demonstrate that stimulation of neurons in the stroke hemisphere is sufficient to promote recovery.

Impaired Arm Function and Finger Dexterity in a Nonhuman Primate Model of Stroke: Motor and Cognitive Assessments.

BACKGROUND AND PURPOSE: Ischemic stroke is the leading cause of upper extremity motor impairments. Although several well-characterized experimental stroke models exist, modeling of upper extremity motor impairments, which are unique to primates, is not well established. Cortical representation of dexterous movements in nonhuman primates is functionally and topographically similar to that in humans. In this study, we characterize the African green monkey model of focal ischemia reperfusion with a defined syndrome, impaired dexterous movements. METHODS: Cerebral ischemia was induced by transient occlusion of the M3 segment of the left middle cerebral artery. Motor and cognitive functions after stroke were evaluated using the object retrieval task with barrier-detour. Postmortem magnetic resonance imaging and histopathology were performed to map and characterize the infarct. RESULTS: The middle cerebral artery occlusion consistently produced a necrotic infarct localized in the sensorimotor cortex in the middle cerebral artery territory. The infarction was reproducible and resulted in significant loss of fine motor function characterized by impaired dexterity. No significant cognitive impairment was detected. Magnetic resonance imaging and histopathology demonstrated consistent and significant loss of tissue on the left parietal cortex by the central sulcus covering the sensorimotor area. The results suggest that this species has less collateralization, which closely resembles humans. CONCLUSIONS: The reported nonhuman primate model produces a defined and reproducible syndrome relevant to our understanding of ischemic stroke, cortical representation, and sensorimotor integration controlling dexterous movements. This model will be useful in basic and translational research addressing loss of arm function and dexterity.