Clinical assessment of cerebral hemodynamics in Moyamoya disease via multiple inversion time arterial spin labeling and dynamic susceptibility contrast-magnetic resonance imaging: A comparative study

Multi-delay arterial spin labeling using a variable repetition time scheme in Moyamoya disease: Comparison with single-delay arterial spin labeling

PURPOSE

To present a multi-delay arterial spin labeling (ASL) protocol that obtains the cerebral blood flow (CBF) considering the arterial transit time (ATT), and to assess the correlations with an iodine-123-N-isopropyl-p-iodoamphetamine single-photon emission computed tomography (123I-IMP SPECT) reference standard between multi-delay ASL and single-delay ASL in patients with Moyamoya disease.

METHOD

We retrospectively analyzed the images of 23 patients with Moyamoya disease (4-73 years, 5 men, 18 women), each of whom was imaged with 10-delay ASL using the variable repetition time (TR) scheme, single-delay ASL, and SPECT. Pearson correlation coefficients were calculated between the CBF values of each ASL and SPECT in the three divisions of the ATT, which we categorized as fast, normal, and slow regions. The threshold for statistical significance was set atP<0.05.

RESULTS

The CBF measured by multi-delay ASL and single-delay ASL were positively correlated with that measured by SPECT, with correlation coefficients of 0.6701 and 0.5637, respectively (P < 0.001). In the fast, normal, and slow ATT divisions, the correlation coefficients between the CBF measured by multi-delay ASL and that measured by SPECT were 0.6745, 0.7055, and 0.6746, respectively. Similarly, the correlations between the CBF measured by single-delay ASL and that measured by SPECT were 0.3811, 0.5090 and 0.6178, respectively.

CONCLUSIONS

Multi-delay ASL using the variable TR scheme showed a higher correlation with 123I-IMP SPECT than single-delay ASL for measuring the CBF. The variable TR scheme potentially improved the quantification of CBF on ASL imaging.

A Prospective Study on Hemodynamics of Combined Bypass Surgery in the Treatment of Moyamoya Disease

OBJECTIVE

The study investigates the clinical effectiveness and prognosis of selecting recipient vessels for moyamoya disease (MMD) treatment during combined bypass surgery, focusing on hemodynamic criteria.

METHODS

Ninety-six MMD patients were randomly assigned to 3 groups (A, B, C) of 32 each, undergoing combined bypass surgery. Group A selected the vessel with the fastest fluorescing in the surgical field, group B the slowest, and group C used traditional methods. The authors monitored intraoperative recipient vessel pressure, cerebral blood flow (CBF), and modified Rankin scale (mRS) scores pre-surgery and post-surgery, and compared clinical symptom improvement, stroke recurrence, CBF, and mRS during a 6-month follow-up.

RESULTS

Postoperatively, groups A and B had significantly higher recipient vessel pressures than group C, with group B showing the highest (P<0.05). CBF increased significantly in all groups at 7 days post-surgery and at 6 months, with groups A and B outperforming C, and group B showing the highest increase at 7 days (P<0.05). mRS scores decreased significantly, with groups A and B showing lower scores than C at 6 months (P<0.05). However, group B had a higher incidence of clinical symptoms post-surgery compared with A and C (P<0.05).

CONCLUSION

The study demonstrates that hemodynamic-based recipient vessel selection significantly improves clinical outcomes in MMD patients undergoing combined bypass surgery. Although group B showed the best hemodynamic results, it also had a higher incidence of immediate postoperative symptoms, suggesting a need for a balanced approach to optimize both short-term and long-term patient outcomes.

Treatment for moyamoya disease with hyperhomocysteinemia

This study aimed to investigate the impact of controlling serum homocysteine on improving surgical outcomes in patients with moyamoya disease (MMD) and hyperhomocysteinemia. In this prospective observational cohort study, 477 patients with MMD post-encephaloduroarteriosynangiosis are divided into the HHcy-MMD post-control group (n = 193), HHcy-MMD uncontrolled group (n = 91), and MMD group (n = 193), with the HHcy-MMD post-control group further subdivided into good (homocysteine 0-10 μmol/L, n = 121) and general (homocysteine 10-15 μmol/L, n = 72) control groups. The differences in imaging and long-term clinical prognosis among the three groups were compared. No significant differences were noted in the Matsushima grade after encephaloduroarteriosynangiosis between the MMD group and HHcy-MMD post-control group (P > 0.05); however, there was a significant difference between the HHcy-MMD post-control group and HHcy-MMD uncontrolled group (P < 0.001). A significant difference was noted between the good and general control groups in the Matsushima grade (P = 0.025) and long-term follow-up clinical outcomes (P = 0.035). The area under the curve of homocysteine levels for predicting adverse clinical outcomes was 85.48% (95% confidence interval: 80.31-90.65%). Effective control of serum Hcy level after EDAS surgery in Moyamoya disease patients with HHcy may lead to better prognosis.Clinical Trial Registration: This study was registered at ClinicalTrials.gov (NCT03613701).

Three-Dimensional Arterial Spin Labeling for the Evaluation of the Cerebral Hemodynamics in Ischemic and Hemorrhagic Moyamoya Disease

INTRODUCTION

Moyamoya disease (MMD) is a vascular disease with significant risk of mortality due to ischemia or hemorrhage in the brain. The goal of the study was to explore three-dimensional arterial spin labeling (3D-ASL) to improve evaluation of cerebral hemodynamics in patients with MMD.

METHODS

Our study included 54 cases of ischemic MMD and 42 cases of hemorrhagic MMD. Dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI) and 3D-ASL were performed at 3.0 T. Based on these scans, cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP) were calculated and compared between patients with different disease subtypes. Receiver operating characteristics analysis was used to assess the diagnostic sensitivity and specificity of different imaging procedures and parameters.

RESULTS

Our data suggested that CBF in the lesion area was more severely reduced in patients with hemorrhagic MMD than in those with ischemic MMD. The CBF parameter in 3D-ASL diagnosed hemorrhagic and ischemic MMD with a significant sensitivity and specificity of 80.59% and 57.41%, respectively, with an area under the curve (AUC) of 0.75. We also found that the relative CBF of 3D-ASL was more pronounced decreased and the relative MTT and TTP of DSC-PWI were significantly increased in patients with hemorrhagic MMD than those with ischemic MMD. Specificity and sensitivity and AUC of 3D-ASL were better than the comparison of absolute values from DSC-PWI scans.

CONCLUSION

Our study indicated that 3D-ASL is powerful in differentiating patients with cerebral ischemic or hemorrhagic MMD, providing another diagnostic tool that could potentially improve precision medicine to monitoring MMD patients.

Surgical outcomes following encephaloduroarteriosynangiosis in moyamoya disease associated with hyperhomocysteinemia

INTRODUCTION

This study investigated the effect of indirect revascularization surgery in adult patients with moyamoya disease (MMD) complicated with hyperhomocysteinemia (HHcy), and the effect of HHcy on the progression of adult MMD.

METHODS

A retrospective case-control study was conducted in patients with MMD, with or without HHcy (n = 123). Postoperative collateral angiogenesis was evaluated using the Matsushima grading system and disease progression using the Suzuki staging system. Cerebral blood flow was evaluated before and after surgery using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) and neurological function prognosis using the improved Rankin score (mRS). Univariate and multivariate logistic regression analyses were performed to determine risk factors for the clinical outcomes.

RESULTS

There was no significant difference in the Suzuki stage composition ratios between the HHcy group and the non-HHcy group before and after surgery. Non-HHcy patients were more likely to grow new collateral circulating vessels after encephaloduroarteriosynangiosis (EDAS). Moreover, postoperative DSC-MRI indicated that the time to peak significantly improved.

CONCLUSIONS

HHcy level may be a specific predictor of adverse clinical outcomes after EDAS in patients with MMD and a risk factor for poor collateral circulation and poor prognosis. Patients with MMD complicated with HHcy need to strictly control homocysteine levels before EDAS surgery.

White and Gray Matter Perfusion in Children with Moyamoya Angiopathy after Revascularization Surgery

INTRODUCTION

Surgical revascularization is very effective in patients with moyamoya angiopathy (MMA) and leads to improvements in cortical perfusion parameters. However, changes in white matter hemodynamics are still underestimated. To date, only a few studies have examined brain perfusion changes within deep white matter after bypass surgery in patients with MMA.

METHODS

Ten children with MMA were evaluated using the CT perfusion technique before and after revascularization surgery. Brain perfusion parameters within gray and white matter were compared before and after surgery. The correlations between the perfusion parameters before surgery and the Suzuki stage, as well as between the perfusion parameters and the cognitive scores, were also evaluated.

RESULTS

Brain perfusion parameters improved significantly in both gray matter (predominantly due to cerebral blood flow within the anterior circulation, p < 0.01) and white matter (predominantly due to cerebral blood volume within the semiovale centrum, p < 0.001). We revealed that the pattern of improvement in perfusion in white matter differed from the pattern of improvement in perfusion in gray matter. Significant correlations were revealed between the Suzuki stage before surgery and the perfusion parameters within the posterior cerebral artery circulation (adjusted p < 0.05). There were also significant correlations between cognitive scores and brain perfusion parameters in gray matter and white matter (adjusted p < 0.05).

CONCLUSIONS

The perfusion parameters of gray matter and white matter in the brain improve differently after bypass surgery in patients with MMA. Different hemodynamics within these compartments could explain this.

T1w/T2w ratio is associated with the brush sign and perfusion delay in watershed regions in patients with moyamoya angiopathy

BACKGROUND

It has been shown recently using the T1w/T2w mapping technique that white matter microstructural integrity impairments exist in watershed regions patients with moyamoya angiopathy (MMA). We hypothesized that these changes could be associated with the prominence of other neuroimaging markers of chronic brain ischemia, such as perfusion delay and the brush sign.

METHODS

Thirteen adult patients with MMA (24 affected hemispheres) were evaluated using brain MRI and CT perfusion. The T1w/T2w signal intensity ratio, which reflects white matter integrity, was calculated in watershed regions (centrum semiovale and middle frontal gyrus). Brush sign prominence was evaluated with susceptibility-weighted MRI. Additionally, brain perfusion parameters such as cerebral blood flow (CBF), cerebral blood volume (CBF), and mean transit time (MTT) were assessed. Correlations between white matter integrity and perfusion changes in watershed regions, as well as the prominence of the brush sign, were evaluated.

RESULTS

Statistically significant negative correlations between the prominence of the brush sign and the T1w/T2w ratio values from the centrum semiovale and middle frontal white matter were found (R = -0.62 to 0.71, adjusted p < 0.05). Furthermore, there was a positive correlation between the T1w/T2w ratio values and the MTT values from the centrum semiovale (R = 0.65, adjusted p < 0.05).

CONCLUSIONS

We revealed that T1w/T2w ratio changes are associated with the prominence of the brush sign as well as white matter hypoperfusion in watershed regions in patients with MMA. This could be explained by chronic ischemia due to venous congestion in the deep medullary vein territory.

To explore the effectiveness of atorvastatin in the postoperative formation of collateral blood vessels after encephaloduroarteriosynangiosis in patients with moyamoya disease: a prospective double-blind randomized controlled study

Introduction

The aim of this large, prospective, double-blind randomized controlled trial is to investigate the effect of atorvastatin on the formation of collateral blood vessels in patients after encephaloduroarteriosynangiosis (EDAS) and to provide a theoretical basis for clinical drug intervention. Specifically, we will determine whether atorvastatin has an effect on the development of collateral vascularization and on cerebral blood perfusion after revasculoplasty in patients with moyamoya disease (MMD).

Methods and analysis

Overall, 180 patients with moyamoya disease will be recruited and randomly assigned to the atorvastatin treatment group or the placebo control group in a 1:1 ratio. Before revascularization surgery, magnetic resonance imaging (MRI) scanning and digital subangiography (DSA) examination will be routinely performed on the enrolled patients. All patients will receive intervention via EDAS. According to the randomization results, patients in the experimental group will be treated with atorvastatin (20 mg/day, once a day, for 8 weeks) and patients in the control group will be treated with placebo (20 mg/day, once a day, for 8 weeks). All participants will return to the hospital for MRI scan and DSA examination 6 months after EDAS surgery. The primary outcome of this trial will be the difference in the formation of collateral blood vessels revealed by DSA examination at 6 months after EDAS surgery between the two groups. The secondary outcome will be an improvement in the dynamic susceptibility contrast sequence cerebral perfusion on MRI at 6 months after EDAS, compared to the preoperative baseline.

Ethics and dissemination

This study was approved by the Ethics Committee of the First Medical Center of the PLA General Hospital. All participates will voluntary provide written informed consent before participating in the trial.

Clinical trial registration

ClinicalTrials.gov, ChiCTR2200064976.

Physiological and pathophysiological mechanisms of the molecular and cellular biology of angiogenesis and inflammation in moyamoya angiopathy and related vascular diseases

Rationale

The etiology and pathophysiological mechanisms of moyamoya angiopathy (MMA) remain largely unknown. MMA is a progressive, occlusive cerebrovascular disorder characterized by recurrent ischemic and hemorrhagic strokes; with compensatory formation of an abnormal network of perforating blood vessels that creates a collateral circulation; and by aberrant angiogenesis at the base of the brain. Imbalance of angiogenic and vasculogenic mechanisms has been proposed as a potential cause of MMA. Moyamoya vessels suggest that aberrant angiogenic, arteriogenic, and vasculogenic processes may be involved in the pathophysiology of MMA. Circulating endothelial progenitor cells have been hypothesized to contribute to vascular remodeling in MMA. MMA is associated with increased expression of angiogenic factors and proinflammatory molecules. Systemic inflammation may be related to MMA pathogenesis.

Objective

This literature review describes the molecular mechanisms associated with cerebrovascular dysfunction, aberrant angiogenesis, and inflammation in MMA and related cerebrovascular diseases along with treatment strategies and future research perspectives.

Methods and results

References were identified through a systematic computerized search of the medical literature from January 1, 1983, through July 29, 2022, using the PubMed, EMBASE, BIOSIS Previews, CNKI, ISI web of science, and Medline databases and various combinations of the keywords "moyamoya," "angiogenesis," "anastomotic network," "molecular mechanism," "physiology," "pathophysiology," "pathogenesis," "biomarker," "genetics," "signaling pathway," "blood-brain barrier," "endothelial progenitor cells," "endothelial function," "inflammation," "intracranial hemorrhage," and "stroke." Relevant articles and supplemental basic science articles almost exclusively published in English were included. Review of the reference lists of relevant publications for additional sources resulted in 350 publications which met the study inclusion criteria. Detection of growth factors, chemokines, and cytokines in MMA patients suggests the hypothesis of aberrant angiogenesis being involved in MMA pathogenesis. It remains to be ascertained whether these findings are consequences of MMA or are etiological factors of MMA.

Conclusions

MMA is a heterogeneous disorder, comprising various genotypes and phenotypes, with a complex pathophysiology. Additional research may advance our understanding of the pathophysiology involved in aberrant angiogenesis, arterial stenosis, and the formation of moyamoya collaterals and anastomotic networks. Future research will benefit from researching molecular pathophysiologic mechanisms and the correlation of clinical and basic research results.

Association of cognitive function and hypoperfusion in Moyamoya disease patients without stroke

The influence of hypoperfusion on cognition in patients with Moyamoya disease (MMD) is unclear. This study investigated cognitive function changes in MMD patients without stroke and illustrated the relationship between cognitive impairment and hypoperfusion. We prospectively performed a structured battery of seven neurocognitive tests on 115 adult MMD patients without stroke and 82 healthy controls. Hemodynamic assessment was performed using dynamic susceptibility contrast-enhanced MRI. The best subset regression (BSR) strategy was used to identify risk factors. Global cognition (MoCA), speed of information processing (TMT-A), executive function (TMT-B), visuospatial function (CDT), and verbal memory (CAVLT) were significantly poorer in MMD patients without stroke than in healthy controls. The TMT-B score significantly correlated with cerebral blood flow (CBF) in the bilateral lateral frontal lobes, centrum semiovale, and temporal lobes. The TMT-A and CAVLT scores significantly correlated with CBF in the left centrum semiovale (L-CSO) and temporal lobes. According to the BSR results, age, education, white matter lesions, and hypoperfusion of the L-CSO were risk factors for cognitive impairment. Hypoperfusion leads to multiple cognitive impairments in MMD patients without stroke. The perfusion of particular areas may help evaluate the cognitive function of MMD patients and guide therapeutic strategies.

DSC MRI in the human brain using deoxyhemoglobin and gadolinium-Simulations and validations at 3T

INTRODUCTION

Dynamic susceptibility contrast (DSC) MRI allows clinicians to determine perfusion parameters in the brain, such as cerebral blood flow, cerebral blood volume, and mean transit time. To enable quantification, susceptibility changes can be induced using gadolinium (Gd) or deoxyhemoglobin (dOHb), the latter just recently introduced as a contrast agent in DSC. Previous investigations found that experimental parameters and analysis choices, such as the susceptibility amplitude and partial volume, affect perfusion quantification. However, the accuracy and precision of DSC MRI has not been systematically investigated, particularly in the lower susceptibility range.

METHODS

In this study, we compared perfusion values determined using Gd with values determined using a contrast agent with a lower susceptibility-dOHb-under different physiological conditions, such as varying the baseline blood oxygenation and/or magnitude of hypoxic bolus, by utilizing numerical simulations and conducting experiments on healthy subjects at 3T. The simulation framework we developed for DSC incorporates MRI signal contributions from intravascular and extravascular proton spins in arterial, venous, and cerebral tissue voxels. This framework allowed us to model the MRI signal in response to both Gd and dOHb.

RESULTS AND DISCUSSION

We found, both in the experimental results and simulations, that a reduced intravascular volume of the selected arterial voxel, reduced baseline oxygen saturation, greater susceptibility of applied contrast agent (Gd vs. dOHb), and/or larger magnitude of applied hypoxic bolus reduces the overestimation and increases precision of cerebral blood volume and flow. As well, we found that normalizing tissue to venous rather than arterial signal increases the accuracy of perfusion quantification across experimental paradigms. Furthermore, we found that shortening the bolus duration increases the accuracy and reduces the calculated values of mean transit time. In summary, we experimentally uncovered an array of perfusion quantification dependencies, which agreed with the simulation framework predictions, using a wider range of susceptibility values than previously investigated. We argue for caution when comparing absolute and relative perfusion values within and across subjects obtained from a standard DSC MRI analysis, particularly when employing different experimental paradigms and contrast agents.

The value of 3D pseudo-continuousarterial spin labeling perfusion imaging in moyamoya disease—Comparison with dynamic susceptibility contrast perfusion imaging

Background and purpose

3D pseudo-continuous arterial spin labeling (3D pCASL) is commonly used to measure arterial cerebral blood flow (CBF). The aim of this study was to assess the clinical feasibility and accuracy of 3D pCASL in comparison with dynamic susceptibility contrast (DSC) perfusion imaging in moyamoya disease (MMD).

Materials and methods

A total of 174 MMD patients underwent 3D pCASL and DSC-MRI for evaluating cerebral blood perfusion. 3D-pCASL with two single post-labeling delay (PLD) times (1,500 and 2,500 ms) was used to measure CBF. The values of DSC-CBF and ASL-CBF were calculated for major arterial territories including the anterior, middle, and posterior cerebral arteries as well as the areas based on the Alberta Stroke Program Early CT Score (ASPECTS) template. The correlation between DSC-CBF and ASL-CBF was analyzed. The consistency and accuracy between the two methods in assessing the cerebral ischemic state before and after surgery were analyzed.

Results

The correlation between ASL (2,500 ms) and DSC-MRI was slightly better than the correlation between ASL (1,500 ms) and DSC-MRI in major vascular territories before revascularization. Significant correlations were observed between ASL (2,500 ms) and DSC-MRI and between ASL (1,500 ms) and DSC-MRI in major vascular territories after revascularization. For 44 surgically treated patients, the scores of ASPECTS for CBF on the operated side were significantly different before and after revascularization (p < 0.05) and showed good consistency on all the examination methods. A comparison of the scores of ASPECTS of the three parameters before and after revascularization showed that there was no statistical difference between them (p > 0.05).

Conclusion

Compared to DSC-MRI, 3D pCASL can assess the cerebral blood perfusion in MMD before and after revascularization effectively. 3D pCASL showed the feasibility and clinical utility value in patients with MMD.

The Potential Mechanism Behind Native and Therapeutic Collaterals in Moyamoya

Background and Purpose

To explore the genetic basis and molecular mechanism of native arteriogenesis and therapeutic synangiosis in moyamoya disease (MMD).

Methods

An angiography-based study using patients from a prospective trial of encephaloduroarteriosynangiosis (EDAS) surgery was performed. The spontaneous collaterals grades were evaluated according to the system described by a new grading system. Blood samples were collected from all the recruited patients before EDAS and during the second hospitalization 3 months post-EDAS. We performed Boolean analysis using a combination of specific cell surface markers of CD34^briCD133⁺CD45^dimKDR⁺. Genotyping of p.R4810K was also performed. The correlation of age, sex, initial symptoms at diagnosis, collateral grade, Suzuki stages, the RNF213 genotype, time to peak (TTP), and endothelial progenitor cell (EPC) count with good collateral circulation was evaluated.

Results

Eighty-five patients with MMD were included in this study. The mutation rate of RNF213 p.R4810K in our study was 25.9% (22/85). The heterozygous mutations were occurred significantly more frequently in the cases that were presented with infarction, worse neurological status, severe posterior cerebral artery (PCA) stenosis, and longer TTP delay. Further, the heterozygous mutations occurred significantly more frequently in the poor collateral stage group. Lower grades were significantly correlated with severe ischemia symptoms, worse neurological status, and a longer TTP delay. The post-operative angiographic findings showed that a good Matsushima grade was correlated with heterozygous mutations, a lower collateral stage, and a longer TTP delay. The CD34^briCD133⁺CD45^dimKDR⁺ cell count in patients 3 months post-EDAS was significantly higher as compared to the count before EDAS in the good Matsushima grade group. However, this change was not observed in the poor Matsushima grade group.

Conclusions

These data imply that mutations of RNF213 p.R4810K affect the establishment of spontaneous collateral circulation, and EPCs are involved in the process of formation of new EDAS collaterals.

Arterial spin labeling as an ancillary assessment to postoperative conventional angiogram in pediatric moyamoya disease

OBJECTIVE

Digital subtraction angiography (DSA) is commonly performed after pial synangiosis surgery for pediatric moyamoya disease to assess the degree of neovascularization. However, angiography is invasive, and the risk of ionizing radiation is a concern in children. In this study, the authors aimed to identify whether arterial spin labeling (ASL) can predict postoperative angiogram grading. In addition, they sought to determine whether patients who underwent ASL imaging without DSA had similar postoperative outcomes when compared with patients who received ASL imaging and postoperative DSA.

METHODS

The medical records of pediatric patients who underwent pial synangiosis for moyamoya disease at a quaternary children's hospital were reviewed during a 10-year period. ASL-only and ASL+DSA cohorts were analyzed. The frequency of preoperative and postoperative symptoms was analyzed within each cohort. Three neuroradiologists assigned a visual ASL grade for each patient indicating the change from the preoperative to postoperative ASL perfusion sequences. A postoperative neovascularization grade was also assigned for patients who underwent DSA.

RESULTS

Overall, 21 hemispheres of 14 patients with ASL only and 14 hemispheres of 8 patients with ASL+DSA were analyzed. The groups had similar rates of MRI evidence of acute or chronic stroke preoperatively (61.9% in the ASL-only group and 64.3% in the ASL+DSA group). In the entire cohort, transient ischemic attack (TIA) (p = 0.027), TIA composite (TIA or unexplained neurological symptoms; p = 0.0006), chronic headaches (p = 0.035), aphasia (p = 0.019), and weakness (p = 0.001) all had decreased frequency after intervention. The authors found a positive association between revascularization observed on DSA and the visual ASL grading (p = 0.048). The visual ASL grades in patients with an angiogram indicating robust neovascularization demonstrated improved perfusion when compared with the ASL grades of patients with a poor neovascularization.

CONCLUSIONS

Noninvasive ASL perfusion imaging had an association with postoperative DSA neoangiogenesis following pial synangiosis surgery in children. There were no significant postoperative stroke differences between the ASL-only and ASL+DSA cohorts. Both cohorts demonstrated significant improvement in preoperative symptoms after surgery. Further study in larger cohorts is necessary to determine whether the results of this study are validated in order to circumvent the invasive catheter angiogram.

Imaging methods for surgical revascularization in patients with moyamoya disease: an updated review

Neuroimaging is crucial in moyamoya disease (MMD) for neurosurgeons, during pre-surgical planning and intraoperative navigation not only to maximize the success rate of surgery, but also to minimize postsurgical neurological deficits in patients. This is a review of recent literatures which updates the clinical use of imaging methods in the morphological and hemodynamic assessment of surgical revascularization in patients with MMD. We aimed to assist surgeons in assessing the status of moyamoya vessels, selecting bypass arteries, and monitoring postoperative cerebral perfusion through the latest imaging technology.

Clinical utility of arterial spin labeling imaging in disorders of the nervous system

Neuroimaging is an indispensable tool in the workup and management of patients with neurological disorders. Arterial spin labeling (ASL) is an imaging modality that permits the examination of blood flow and perfusion without the need for contrast injection. Noninvasive in nature, ASL provides a feasible alternative to existing vascular imaging techniques, including angiography and perfusion imaging. While promising, ASL has yet to be fully incorporated into the diagnosis and management of neurological disorders. This article presents a review of the most recent literature on ASL, with a special focus on its use in moyamoya disease, brain neoplasms, seizures, and migraines and a commentary on recent advances in ASL that make the imaging technique more attractive as a clinically useful tool.

Decreased Relative Cerebral Blood Flow in Unmedicated Heroin-Dependent Individuals

Understanding the brain mechanisms of heroin dependence is invaluable for developing effective treatment. Measurement of regional cerebral blood flow (CBF) provides a method to visualize brain circuits that are functionally impaired by heroin dependence. This study examined regional CBF alterations and their clinical associations in unmedicated heroin-dependent individuals (HDIs) using a relatively large sample. Sixty-eight (42 males, 26 females; age: 40.9 ± 7.3 years) HDIs and forty-seven (34 males, 13 females; age: 39.3 ± 9.2 years) matched healthy controls (HCs) underwent high-resolution T1 and whole-brain arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) scans. Additionally, clinical characteristics were collected for neurocognitive assessments. HDIs showed worse neuropsychological performance than HCs and had decreased relative CBF (rCBF) in the bilateral middle frontal gyrus (MFG), inferior temporal gyrus, precuneus, posterior cerebellar lobe, cerebellar vermis, and the midbrain adjacent to the ventral tegmental area; right posterior cingulate gyrus, thalamus, and calcarine. rCBF in the bilateral MFG was negatively correlated with Trail Making Test time in HDIs. HDIs had limbic, frontal, and parietal hypoperfusion areas. Low CBF in the MFG indicated cognitive impairment in HDIs. Together, these findings suggest the MFG as a critical region in HDIs and suggest ASL-derived CBF as a potential marker for use in heroin addiction studies.

Progress in moyamoya disease

Moyamoya disease is characterized by progressive stenosis or occlusion of the intracranial portion of the internal carotid artery and their proximal branches, resulting in ischemic or hemorrhagic stroke with high rate of disability and even death. So far, available treatment strategies are quite limited, and novel intervention method is being explored. This review encapsulates current advances of moyamoya disease on the aspects of epidemiology, etiology, clinical features, imaging diagnosis and treatment. In addition, we also bring forward our conjecture, which needs to be testified by future research.

Collateral Circulation in Moyamoya Disease: A New Grading System

Background and Purpose- Predicting the risk of stroke and determining intervention indications are highly important for patients with Moyamoya disease (MMD). Here, we evaluated a novel MMD grading system based on collateral circulation and Suzuki stage to evaluate symptoms and predict prognosis. Methods- In total, 301 idiopathic MMD patients were retrospectively analyzed between 2014 and 2016. A collateral circulation grading system with scores ranging from 1 to 12 was established: the anatomic extent of pial collateral blood flow from posterior cerebral artery to middle cerebral artery and anterior cerebral artery was scored from 1 to 6; perforator collateral and internal cerebral artery flow were scored as 6 to 1, which corresponded to Suzuki stages 1 to 6. Dynamic susceptibility contrast-magnetic resonance imaging was used to evaluate hemodynamic status. We assessed the association between the grading system and clinical characteristics. Results- We analyzed 364 symptomatic hemispheres of 301 patients (146 males, 28±16 years). Ischemic patients who presented with infarction were more likely to score <8 points (P<0.001), whereas those with ischemia symptoms (transient ischemic attack and headache) were more likely to score >8 points. Hemorrhagic patients who presented with intraparenchymal hemorrhage were more likely to score <8 points, whereas those who presented with intraventricular hemorrhage were more likely to score >8 points (P<0.001). According to dynamic susceptibility contrast-magnetic resonance imaging, lower scores were correlated with more severe time to peak delay (P<0.001) and worse relative cerebral blood volume ratio (P=0.016) and cerebral flow ratio (P=0.002). Encephaloduroarteriosynangiosis was performed in 348 symptomatic hemispheres. Patients who had collateral scores <4 points were more likely to have a postoperative stroke and a worse prognosis during the follow-up. Conclusions- This new MMD collateral grading system correlated well with clinical symptoms, hemodynamic status, and therapeutic prognosis and may facilitate risk stratification and prognosis predictions in patients with MMD.

Arterial spin-labeling cerebral perfusion changes after revascularization surgery in pediatric moyamoya disease and syndrome

OBJECTIVE

Moyamoya disease is a dynamic cerebrovascular condition that often requires vascular surveillance. Arterial spin labeling (ASL) is an MR perfusion method that is increasingly used for stroke and other various neurovascular pathologies. Unlike perfusion-weighted MRI, ASL uses endogenous water molecules for signal and therefore obviates gadolinium use; and provides direct, not relative, quantitative cerebral blood flow (CBF) measures. Presently, the potential role of ASL for evaluating postoperative pediatric moyamoya patients is relatively unexplored. This study investigated the role for ASL in evaluating cerebral hemodynamic changes in children who underwent revascularization surgery.

METHODS

This retrospective study examined 15 consecutive pediatric patients with moyamoya disease (n = 7) or moyamoya syndrome (n = 8) presenting between 2010 and 2014 who underwent revascularization and in whom 3T ASL was performed pre- and postoperatively. Postoperative MRI at least 3 months after revascularization procedure was used for analysis. Quantitative CBF in various vascular territories was interrogated: anterior, middle, and posterior cerebral arteries, and basal ganglia supplied by the lenticulostriate collaterals, resulting in evaluation of 20 brain regions.

RESULTS

After revascularization, CBF in the high middle cerebral artery territory significantly increased (p = 0.0059), accompanied by a decrease in CBF to the ipsilateral lenticulostriate-supplied basal ganglia (p = 0.0053). No perfusion changes occurred in the remaining cerebral vascular territories after surgery.

CONCLUSIONS

ASL-based quantitative CBF showed improved cerebral perfusion to the middle cerebral artery territory after revascularization in children with both moyamoya syndrome and disease. Reduced perfusion to the basal ganglia might reflect pruning of the lenticulostriate collaterals, potentially from effects of revascularization. ASL can quantitatively evaluate hemodynamic changes in children with moyamoya after revascularization, and it may be a useful adjunct to routine clinical MRI surveillance.

Comparative study of MR mTI-ASL and DSC-PWI in evaluating cerebral hemodynamics of patients with Moyamoya disease

The aim of this study was to explore the correlation between multi-inversion time arterial spin labeling (mTI-ASL) and dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI) in assessment of hemodynamics of patients with Moyamoya disease (MMD).In this study, 24 MMD patients and 21 healthy subjects were enrolled between June 2017 and December 2017. The images of mTI-ASL and DSC-PWI in the week before revascularization surgery were retrospectively analyzed. The parameters of cerebral blood flow (CBF), time to peak (TTP), and bolus arrival time (BAT) were measured in regions of interest (ROIs) of lateral middle cerebral artery (MCA) territories, basal ganglia (BG), and cerebellum, and relative perfusion parameters (rCBF-ASL, rBAT-ASL, rCBF-DSC, and rTTP-DSC) were calculated by dividing by cerebellum value. One-way analysis of variance and Student-Newman-Keuls tests were performed to compare rCBF-ASL and rCBF-DSC in the MMD group and the control group. Unpaired t test was used to compare rBAT-ASL and rTTP-DSC in the MMD group and the control group. And we assessed the correlation between rCBF-ASL and rCBF-DSC and between rBAT-ASL and rTTP-DSC using Pearson correlation analysis.All the relative parameters were significantly different between the MMD group and the control group (all P<.05). Meanwhile, there was significant difference between rCBF-ASL and rCBF-DSC (P<.05), and there was strong correlation between rCBF-ASL and rCBF-DSC (r = 0.839, P<.001), and moderate correlation between rBAT-ASL and rTTP-DSC (r = 0.519, P<.001).Both mTI-ASL and DSC-PWI could be used to assess perfusion state in MMD patients before revascularization surgery effectively. As a noninvasive imaging technique, mTI-ASL could provide perfusion parameters without contrast medium injection, and the results were quite correlative with DSC-PWI.

Monitoring Cerebral Perfusion Changes after Revascularization in Patients with Moyamoya Disease by Using Arterial Spin-labeling MR Imaging

Purpose To determine whether arterial spin-labeling (ASL) magnetic resonance (MR) imaging could be used to identify changes in cerebral blood flow (CBF), collateral blood flow, and anastomosis site patency after revascularization in patients with moyamoya disease. Materials and Methods This retrospective study was conducted in 145 patients with moyamoya disease who underwent middle cerebral artery (MCA)-superficial temporal artery anastomosis. Preoperative, early postoperative, and late postoperative ASL and digital subtraction angiography images were analyzed. In the MCA territory, absolute CBF (hereafter, CBF_MCA) and normalized CBF values adjusted to nonanastomosis side (hereafter, nCBF_MCA) and to cerebellum (hereafter, nCBF_Cbll) were calculated. Collateral grading in the MCA territory was assessed according to Alberta Stroke Program Early CT Score methodology, and anastomosis site patency were also assessed. Changes in CBF were compared by using one-way analysis of variance with Bonferroni correction for multiple comparisons. Intermodality agreement was determined by κ statistics. Results Significant increases in CBF_MCA, nCBF_MCA, and nCBF_Cbll were found after revascularization (preoperative and postoperative values of CBF_MCA, 35.2 mL/100 g per minute ± 7.8 [mean ± standard deviation] and 51.5 mL/100 g per minute ± 12.0; nCBF_MCA, 0.73 mL/100 g per minute ± 0.14 and 1.01 mL/100 g per minute ± 0.18; nCBF_Cbll, 0.74 mL/100 g per minute ± 0.12 and 1.12 mL/100 g per minute ± 0.16; all P < .001). Agreements for collateral grading and anastomosis patency between ASL MR imaging and digital subtraction angiography were moderate to good, with weighted κ values of 0.77 (95% confidence interval: 0.73, 0.81) and 0.57 (95% confidence interval: 0.37, 0.76), respectively. Conclusion ASL MR imaging can be used to identify perfusion changes in patients with moyamoya disease after revascularization as a noninvasive monitoring tool.