Preoperative embolization of brain arteriovenous malformation and efficacy in intraoperative blood loss reduction: a quantitative study

BACKGROUND

Embolization of brain arteriovenous malformations (bAVMs) is often used as adjuvant therapy to microsurgical resection to reduce the high-risk features of bAVMs such as large size and high flow. However, the effect of preoperative embolization on surgical performance and patient outcome has shown mixed results. Heterogeneity in treatment goals, selection criteria, and unpredictable changes in bAVM hemodynamics after partial embolization may account for these uncertain findings. In this study we use an objective quantitative technique to assess the impact of preoperative embolization on intraoperative blood loss (IBL).

METHODS

Patients with bAVM treated with microsurgical resection only or in combination with preoperative embolization from 2012 to 2022 were retrospectively reviewed. Patients were included if quantitative magnetic resonance angiography was performed prior to any treatment. Correlation of baseline bAVM flow, volume, and IBL was evaluated between the two groups. Additionally, bAVM flow prior to and after embolization was compared.

RESULTS

Forty-three patients were included, 31 of whom required preoperative embolization (20 had more than one session). Mean bAVM initial flow (362.3 mL/min vs 89.6 mL/min, p=0.001) and volume (9.6 mL vs 2.8 mL, p=0.001) were significantly higher in the preoperative embolization group; flow decreased significantly after embolization (408.0 mL/min vs 139.5 mL/min, p<0.001). IBL was comparable between the two groups (258.6 mL vs 141.3 mL, p=0.17). Linear regression continued to show a significant difference in initial bAVM flow (p=0.03) but no significant difference in IBL (p=0.53).

CONCLUSION

Patients with larger bAVMs who underwent preoperative embolization had comparable IBL to those with smaller bAVMs undergoing only surgical treatment. Preoperative embolization of high-flow bAVMs facilitates surgical resection, reducing the risk of IBL.

Occipital artery to vertebral artery bypass for treatment of bilateral vertebral artery occlusion with QMRA as an adjunct to diagnostic assessment

PURPOSE

Stroke, the second leading cause of death globally, often involves ischemia in the vertebrobasilar territory. This condition is underexplored, despite significant morbidity and mortality risks. The purpose of this study is to present a case of occipital artery to V3 segment vertebral artery bypass, emphasizing the role of quantitative magnetic resonance angiography (qMRA) in assessing flow and guiding surgical intervention.

METHODS

A 66-year-old man with bilateral vertebral artery occlusion presented acute symptoms. qMRA was employed to evaluate flow dynamics and determine the feasibility of a flow augmentation bypass surgery. The occipital artery to left vertebral artery bypass (OA-to-VA) was performed, utilizing an inverted hockey-stick incision and an antegrade inside-out technique. The patency of the bypass was confirmed using both Doppler probe and Indocyanine green.

RESULTS

Postoperative assessments, including computed tomography angiography (CTA) and qMRA, demonstrated the patency of the bypass with improved flow in the basilar artery and left vertebral artery. The patient's condition remained stable postoperatively, with residual peripheral palsy of the left facial nerve.

CONCLUSION

In conclusion, the presented case illustrates the efficacy of the OA-to-VA bypass in addressing symptomatic bilateral vertebral artery occlusion. The study underscores the pivotal role of qMRA in pre- and postoperative assessments, providing noninvasive flow quantification for diagnostic considerations and long-term follow-up in patients with vertebrobasilar insufficiency.

A narrative review of techniques for surgical revascularization of the extracranial vertebral artery in vertebrobasilar insufficiency

Vertebrobasilar insufficiency is a condition characterized by poor blood flow through the posterior circulation of the brain, which supplies the brainstem, thalamus, hippocampus, cerebellum, occipital lobes, and medial temporal lobes. Narrowing or occlusion of the vertebral arteries may be result in a range of neurological symptoms, including dizziness, imbalance, dysarthria, and even stroke. If symptomatic patients fail medical management, revascularization of the vertebral artery should be considered. Restoration of blood flow may involve transluminal balloon angioplasty or stent placement; however, certain cases may still require surgical intervention. The complexity of surgical revascularization of the vertebral artery requires careful consideration of skull base and neck anatomy. This review article will focus on bypass of the vertebral artery in the setting of ischemic pathology, describing the technique, anatomical nuances, steps involved in preoperative planning, and postoperative management.

Most Promising Approaches to Improve Brain AVM Management: ARISE I Consensus Recommendations

Brain arteriovenous malformations (bAVMs) are complex, and rare arteriovenous shunts that present with a wide range of signs and symptoms, with intracerebral hemorrhage being the most severe. Despite prior societal position statements, there is no consensus on the management of these lesions. ARISE (Aneurysm/bAVM/cSDH Roundtable Discussion With Industry and Stroke Experts) was convened to discuss evidence-based approaches and enhance our understanding of these complex lesions. ARISE identified the need to develop scales to predict the risk of rupture of bAVMs, and the use of common data elements to perform prospective registries and clinical studies. Additionally, the group underscored the need for comprehensive patient management with specialized centers with expertise in cranial and spinal microsurgery, neurological endovascular surgery, and stereotactic radiosurgery. The collection of prospective multicenter data and gross specimens was deemed essential for improving bAVM characterization, genetic evaluation, and phenotyping. Finally, bAVMs should be managed within a multidisciplinary framework, with clinical studies and research conducted collaboratively across multiple centers, harnessing the collective expertise and centralization of resources.

Comapping Cellular Content and Extracellular Matrix with Hemodynamics in Intact Arterial Tissues Using Scanning Immunofluorescent Multiphoton Microscopy

Deviation of blood flow from an optimal range is known to be associated with the initiation and progression of vascular pathologies. Important open questions remain about how the abnormal flow drives specific wall changes in pathologies such as cerebral aneurysms where the flow is highly heterogeneous and complex. This knowledge gap precludes the clinical use of readily available flow data to predict outcomes and improve treatment of these diseases. As both flow and the pathological wall changes are spatially heterogeneous, a crucial requirement for progress in this area is a methodology for acquiring and comapping local vascular wall biology data with local hemodynamic data. Here, we developed an imaging pipeline to address this pressing need. A protocol that employs scanning multiphoton microscopy was developed to obtain three-dimensional (3D) datasets for smooth muscle actin, collagen, and elastin in intact vascular specimens. A cluster analysis was introduced to objectively categorize the smooth muscle cells (SMC) across the vascular specimen based on SMC actin density. Finally, direct quantitative comparison of local flow and wall biology in 3D intact specimens was achieved by comapping both heterogeneous SMC data and wall thickness to patient-specific hemodynamic results.

A patient-specific circle of Willis blood flow model in predicting outcomes of balloon test occlusion

BACKGROUND AND PURPOSE

Balloon test occlusion (BTO) evaluates cerebral ischemic tolerance before internal carotid artery (ICA) sacrifice but carries risks like dissection and thrombosis. This study introduces a new approach using a patient-specific circle of Willis (COW) blood flow model, based on non-invasive quantitative MR angiography (qMRA) measurements, to predict the outcomes of BTO.

METHODS

We developed individualized COW blood flow models for 43 patients undergoing BTO. These models simulated blood flow and pressure under normal conditions and with the ICA occlusion. We then compared the model's predictions of blood flow changes due to the simulated ICA occlusion to actual qMRA measurements before the BTO.

RESULTS

For all 31 BTO failures, the ipsilateral hemisphere showed an average flow decrease of 15 ± 10% (mean ± standard deviation), compared to 3 ± 2% in the contralateral hemisphere. In all 12 BTO passes, these figures were 6 ± 3% and 1 ± 0.8%, respectively. Notably, all BTO passes had less than a 10% reduction in the ipsilateral hemisphere. In contrast, 65% of BTO failures and 67% single-photon emission computed tomography (SPECT) failures exhibited a decrease of 10% or more in the same region.

CONCLUSION

Blood flow reduction exceeding 10% in the ipsilateral hemisphere during BTO is a strong predictor of failure in both BTO and SPECT. Our patient-specific COW blood flow models, incorporating detailed flow and arterial geometry data, offered valuable insights for predicting BTO outcomes. These models are especially beneficial for situations where conducting BTO or SPECT is clinically impractical.

The correlation of cerebral arteriovenous malformation flow measured by quantitative MR angiography on MR-detected arteriovenous malformation microhemorrhage

OBJECTIVE

The objective of this study was to assess the relationship of arteriovenous malformation (AVM) blood flow measured by quantitative MR angiography (QMRA) in nonruptured AVMs with MR-detected microhemorrhage.

METHODS

All patients with unruptured AVMs who received baseline QMRA and gradient echo or susceptibility-weighted MRI were retrospectively reviewed (2004-2022). Imaging data, clinical history, and AVM angioarchitectural and flow features were collected and assessed. AVM flow was calculated from the difference of flow within primary arterial feeders from their contralateral counterparts. A review of the MR images determined the presence of microhemorrhages. Analysis of descriptive statistics, chi-square test, and binomial logistic regression were performed.

RESULTS

Of 634 patients with cerebral AVMs at a single center, 89 patients met the inclusion criteria (54 with microhemorrhage and 35 without microhemorrhage). The calculated AVM flow was significantly higher in the group with a microhemorrhage (447.9 ± 193.1 ml/min vs 287.6 ± 235.7 ml/min, p = 0.009). In addition, the presence of venous anomaly, arterial ectasia, and diffuse nidus was significantly associated with microhemorrhage (p = 0.017, p = 0.041, and p = 0.041, respectively). Binary logistic regression found that higher flow predicted the presence of microhemorrhage (OR 1.002, 95% CI 1.000-1.004; p = 0.031). The highest AVM flow quartile significantly predicted the presence of venous anomaly (OR 3.840, 95% CI 1.037-14.213; p = 0.044), diffuse nidus (OR 6.800, 95% CI 1.766-25.181; p = 0.005), and arterial ectasia (OR 13.846, 95% CI 1.905-122.584; p = 0.018).

CONCLUSIONS

This study represents the first to examine the association between flow measurements on QMRA with microhemorrhage in unruptured AVMs. Higher AVM flow, venous anomaly, arterial ectasia, and diffuse AVM nidus were related to a higher likelihood of AVM microhemorrhage. Higher AVM flow was present in AVMs with venous anomalies, a diffuse nidus, and arterial ectasia, indicating a possible interaction between these angioarchitectural findings, AVM flow, and microhemorrhage. These findings suggest a relationship between higher AVM flow and the risk of microhemorrhage.

Vertebral Artery to Middle Cerebral Artery Bypass for Flow Augmentation

BACKGROUND AND IMPORTANCE

Extracranial-intracranial bypass remains an enduring procedure for a select group of patients suffering from steno-occlusive cerebrovascular disease. Although the superficial temporal artery (STA) to middle cerebral artery (MCA) bypass is most familiar among neurosurgeons, particular circumstances preclude the use of an STA donor. In such cases, alternative revascularization strategies must be pursued.

CLINICAL PRESENTATION

A 63-year-old female presented with symptoms of hemodynamic insufficiency and was found to have left common carotid artery occlusion at the origin. She experienced progressive watershed ischemia and pressure-dependent fluctuations in her neurological examination despite maximum medical therapy. The ipsilateral STA was unsuitable for use as a donor vessel. We performed an extracranial vertebral artery (VA) to MCA bypass with a radial artery interposition graft.

CONCLUSION

This technical case description and accompanying surgical video review the relevant anatomy and surgical technique for a VA-MCA bypass. The patient was ultimately discharged home at her preoperative neurological baseline with patency of the bypass. The VA can serve as a useful donor vessel for cerebral revascularization procedures in pathologies ranging from malignancies of the head and neck to cerebral aneurysms and cerebrovascular steno-occlusive disease.

WITHDRAWN: A narrative review of techniques for surgical revascularization of the extracranial vertebral artery in vertebrobasilar insufficiency

The Publisher regrets that this article is an accidental duplication of an article that has already been published in Neurochirurgie, volume 70. https://doi.org/10.1016/j.neuchi.2023.101516. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/policies/article-withdrawal.

Quantitative Blood Flow Reduction in Selective Embolization of Intranidal Fistula of Cerebral Arteriovenous Malformations: Case Series

BACKGROUND AND OBJECTIVES

Arteriovenous malformations (AVMs) are often associated with high-flow intranidal fistulas (INFs). Although INF embolization has been suggested to provide higher reduction of total AVM flow compared with regular pedicle embolization, this effect has not previously been quantified. The aim of this study was to characterize the effect of AVM INF embolization on total AVM flow.

METHODS

This study is an Institutional Review Board-approved, retrospective case series of patients from 2010 to 2022 with AVMs, both with and without INFs, who underwent quantitative magnetic resonance angiography and endovascular embolization.

RESULTS

Twenty patients accounted for 35 separate embolization sessions: 13 patients with INFs underwent a total 21 embolizations and 12 patients without INFs had 14 embolizations. No significant differences were found between groups on age, sex, laterality, drainage pattern, and Spetzler-Martin grade. However, AVMs with INFs were larger than the control group (12.7 vs 8.37 cm 3 , P = .049). Baseline pre-embolization AVM flow significantly differed between AVM with INF vs control groups (522 vs 320 cc/min, P = .005). Similarly, postembolization AVM flow also differed between AVM with INF and control groups (392 vs 224 cc/min, P = .008), with a larger decrease in flow per vessel per embolization session within the AVM INF group compared with controls (101.5 vs 33.2 cc/min, P < .001). Repeated measure analysis of variance showed significant differences pre-embolization and postembolization AVM flow between those with INFs vs controls ( P < .001).

CONCLUSION

This study represents the first to examine the effect of INF embolization on total AVM flow. AVMs with INFs showed higher baseline flow, and targeted embolization toward INFs significantly lowered AVM flow in comparison with controls without INFs. The results of this study emphasize the importance of recognizing the presence of INFs within AVMs and their embolization to reduce AVM flow as part of a multistep management paradigm.

Transfontanelle photoacoustic imaging of intraventricular brain hemorrhages in live sheep

Intraventricular (IVH) and periventricular (PVH) hemorrhages in preterm neonates are common because the periventricular blood vessels are still developing up to 36 weeks and are fragile. Currently, transfontanelle ultrasound (US) imaging is utilized for screening for IVH and PVH, largely through the anterior fontanelle. However for mild hemorrhages, inconclusive diagnoses are common, leading to failure to detect IVH/PVH or, when other clinical symptoms are present, use of second stage neuroimaging modalities requiring transport of vulnerable patients. Yet even mild IVH/PVH increases the risk of moderate-severe neurodevelopmental impairment. Here, we demonstrate the capability of transfontanelle photoacoustic imaging (TFPAI) to detect IVH and PVH in-vivo in a large animal model. TFPAI was able to detect IVH/PVH as small as 0.3 mL in volume in the brain (p < 0.05). By contrast, US was able to detect hemorrhages as small as 0.5 mL. These preliminary results suggest TFPAI could be translated into a portable bedside imaging probe for improved diagnosis of clinically relevant brain hemorrhages in neonates.

Risk Factors and Management of Incisional Cerebrospinal Fluid Leakage After Craniotomy: A Retrospective International Multicenter Study

BACKGROUND

Incisional cerebrospinal fluid (iCSF) leakage is a serious complication after intradural cranial surgery.

OBJECTIVE

To determine the incidence and risk factors of iCSF leakage after craniotomy. Secondarily, the complications after iCSF leakage and the success rate of iCSF leakage treatment was studied.

METHODS

All patients who underwent an intradural cranial surgery from 2017 to 2018 at 5 neurosurgical centers were retrospectively included. Data were retrieved from medical records with 2 months of follow-up. First, univariate regression analyses were performed. Subsequently, identified risk factors were evaluated in a multivariate regression analysis.

RESULTS

In total 2310 consecutive patients were included. Total iCSF leakage rate was 7.1% (n = 165). Younger age, male, higher body mass index, smoking, infratentorial surgery, and use of a dural substitute were associated with increased iCSF leakage risk, and use of a sealant reduced that risk. The odds for developing a wound infection and/or meningitis were 15 times higher in patients with iCSF leakage compared with patients without leakage. Initial conservative iCSF leakage treatment failed in 48% of patients. In 80% of cases, external cerebrospinal fluid drainage ceased the iCSF leakage. A total of 32% of patients with iCSF leakage required wound revision surgery.

CONCLUSION

iCSF leakage risk increases by younger age, higher body mass index, smoking, infratentorial craniotomy, and dural substitute use, whereas sealant use reduced the risk for iCSF leakage. The leak increases the risk of postoperative infections. When iCSF leakage occurs, immediate external cerebrospinal fluid drainage or wound revision should be considered.

Ultra-widefield and high-speed spiral laser scanning OR-PAM: System development and characterization

Photoacoustic microscopy (PAM) is a high-resolution imaging modality that has been mainly implemented with small field of view applications. Here, we developed a fast PAM system that utilizes a unique spiral laser scanning mechanism and a wide acoustic detection unit. The developed system can image an area of 12.5 cm² in 6.4 s. The system has been characterized using highly detailed phantoms. Finally, the imaging capabilities of the system were further demonstrated by imaging a sheep brain ex vivo and a rat brain in vivo.

Acute Subdural Hematoma Associated with Aneurysmal Rupture: A Case Series and Review of Literature

BACKGROUND

Ruptured cerebral aneurysms represent a neurosurgical emergency with characteristic clinical presentation and imaging findings. However, atypical presentations may occur in association with acute subdural hematomas (SDHs).

METHODS

A retrospective review was conducted at our institution between 2013 and 2021 to identify patients with aneurysmal rupture presenting with SDH. Cases were reviewed for clinical presentation, imaging findings, management, and outcome.

RESULTS

A total of 8 patients were included in this review with an average age of 48.5 years. Six patients were women. The average Glasgow coma scale upon arrival was 6.3, and the Hunt-Hess average grade was 4.6. Aneurysm locations included posterior communicating artery (n = 3), anterior communicating artery (n = 2), middle cerebral artery (n = 2), and internal carotid artery terminus (n = 1). The size of aneurysm varied between 3 and 11 mm. Seven patients required surgical intervention, either craniotomy or craniectomy for hematoma evacuation, and aneurysms were treated by coiling (n = 2) or clipping (n = 6).

CONCLUSIONS

Ruptured aneurysms may present with SDH with or without significant subarachnoid hemorrhage. This illustrative case series highlights this challenging presentation and the importance of early recognition and appropriate management.

Ruptured isolated spinal artery aneurysms: Case series of five patients and a review of the literature on management strategies

BACKGROUND

Aneurysms of the spinal arteries are rare entities, the majority of which are associated with other vascular lesions, such as spinal vascular malformations. Isolated spinal artery aneurysms (SAAs) are even less frequently encountered, and their incidence is largely unknown, as the literature is limited to case reports and small series. The optimal management strategy for SAAs is not well defined.

OBJECTIVE

To review the institutional experience of five patients with isolated SAAs.

METHODS

Five cases of isolated SAAs were identified at our institution, including two cases with multiple simultaneous SAAs. Clinical presentation, imaging, and management strategies for each case were reviewed. A literature review of all SAAs reported between 1950 and 2020 was performed.

RESULTS

A total of five patients with eight isolated SAAs presented to our institution: one aneurysm was lumbar in location, while the remaining seven were thoracic. Two patients were treated with glue embolization followed by laminectomy for hematoma evacuation; one was treated with only surgery; and the other two, which both had multiple lesions, were managed conservatively with interval complete regression of their aneurysms. All five patients had good neurological outcomes. Literature review found 124 patients with at least 137 isolated SAAs and revealed treatment strategies including conservative management, glue or coil embolization, muslin wrapping, and surgical resection or clipping.

CONCLUSION

Multiple management strategies exist for SAAs, and clinical consideration of patient presentation and lesion morphology determine appropriate strategy. Our case series demonstrates three of these treatment paradigms.

Vessel wall imaging and quantitative flow assessment in arteriovenous malformations: A feasibility study

INTRODUCTION

Cerebral arteriovenous malformations (AVMs) carry a rupture rate of 2-3% per year. Several architectural factors may influence rupture rate, and a recently theorized model of AVMs describes the influence of vessel wall inflammation. A novel imaging modality, vessel wall imaging (VWI), has been developed to view inflammatory processes in vessel wall foci but has not yet been examined in AVMs, which is the aim of this study.

METHODS

This retrospective review studies prospectively collected data on patients with ruptured and unruptured AVMs between 2019 and 2021. Inclusion criteria included adult patients (≥18 years) with radiographically diagnosed AVM who underwent VWI. Charts were reviewed for medical history, clinical presentation, hospital course, discharge condition, and follow-up. Angioarchitectural features, blood flow, and VWI were compared in patients with and without hemorrhagic patients.

RESULTS

Nine patients underwent VWI, mean age 37.7 ± 9.9 years. Four presented with hemorrhage (44.4%). Seven (77.7%) received glue embolization and 6 (66.7%) underwent surgical resection. All patients (4/4) with a history of hypertension presented with hemorrhage (p = 0.0027). Size and Spetzler-Martin grade were not associated with hemorrhage (p = 0.47, p = 0.59). Net AVM flow was higher in patients presenting with hemorrhage, although nonsignificant (p = 0.19). With VWI, 3 (75%) hemorrhagic AVMs showed visible nidus and draining veins, and all three demonstrated positive post-contrast wall enhancement in at least one of their draining veins; conversely, of fivenonhemorrhagic AVMs, only 2 (40%) demonstrated post-contrast wall enhancement in any draining vein (p = 0.090).

CONCLUSION

This pilot study successfully demonstrated capture of venous walls in AVMs using VWI. In this study, draining vein enhancement occurred more often in hemorrhagic AVM and in those with higher venous volumetric flow.

Intracranial-Intracranial Bypass for Aneurysms: Quantitative Intraoperative Assessment of Flow Preservation

BACKGROUND

Intraoperative flow measurement has proven utility in extracranial-intracranial bypass, particularly in assessing the adequacy of donors by measurement of cut flow. The nature of intracranial-intracranial (IC-IC) bypass precludes cut flow measurement, but quantitative intraoperative flow measurements may evaluate augment assessment of the bypass.

OBJECTIVE

To retrospectively evaluate flow measurements performed in IC-IC bypass to determine the adequacy of the constructs in preserving flow.

METHODS

With institutional review board approval, we performed a retrospective review of our bypass database from 2001 to 2021 for aneurysms treated with IC-IC bypass and with intraoperative flow measurements. Patients' preoperative characteristics, bypass indications, prebypass and postbypass intraoperative flow measurements, and patient outcomes were recorded.

RESULTS

Of 346 bypasses, 21 cases using 22 IC-IC bypasses were included. The median age was 55 years; 13 of 21 cases were ruptured aneurysms. Aneurysms involved posterior inferior cerebellar artery (n = 7), middle cerebral artery (n = 6), distal anterior cerebral artery (n = 5), and anterior communicating artery (n = 3). Six bypasses were end-to-side (ETS), 10 were side-to-side (STS), and 6 were excisional with reanastomosis (end-to-end, ETE). Intraoperatively, 21 of the bypasses were patent; the postbypass/prebypass flow index averaged 1.15 (±0.32): ETE (n = 6) 1.22 ± 0.34 and ETS/STS bypasses (n = 15) 1.11 ± 0.32. All intraoperatively patent bypasses were patent on postoperative angiography. One occluded on delayed angiography without clinical sequelae.

CONCLUSION

Despite advances in endovascular therapy, IC-IC bypass remains essential to the treatment of large and fusiform aneurysms. We demonstrate quantitatively that IC-IC donors provide adequate direct (ETE) and redistributed (STS ETS) flow to the recipient territory. Flow measurement provides valuable information regarding the patency and adequacy of IC-IC bypass for flow preservation.

Abstract WMP62: Assessment Of Cerebral Hemodynamic Patterns In Cervical Arterial Dissection Using Quantitative Magnetic Resonance Angiography

Background: Cervical arterial dissection accounts for 2-3% of all ischemic strokes. The pathophysiologic mechanism of the ensuing neurological sequelae is largely attributed to embolic phenomenon. The degree to which the dissection may limit cerebral blood flow and its relationship to symptoms is currently not well characterized. This study is the first to evaluate and quantify blood flow using quantitative magnetic resonance angiography (QMRA) in this patient population.

Methods: A retrospective chart review was completed in patients at this institution with cervical arterial dissection between August 31, 2009, to September 1, 2019. Inclusion criteria were adults (≥18 years) with diagnosis of dissection of the common carotid artery, internal carotid artery, or vertebral artery, who received QMRA neuroimaging. The cases were reviewed for clinical presentation, diagnosis, management strategy, and radiologic imaging finding. Flow index was calculated using the ipsilateral vessel flow divided by the contralateral flow. Statistical analyses were completed using SPSS software (Version 27, IBM Corporation, Armonk, NY).

Results: A total of 41 patients were included in this study, 53.7% male and 46.3% female, with mean age 46.0 +/- 11.9 years. Twenty-one patients (51.2%) had ICA dissections while 19 patients (46.3%) had VA dissections, and 1 patient had both ICA and VA vessels affected. Patients with ischemia on MRI demonstrated lower flow in the ipsilateral vessel when compared to those patients without ischemia on MRI at diagnosis and follow-up (p=0.003). Although flow improved over time, patients continued to remain stratified: patients with the lowest index on presentation tended to continue to have low flow in the ipsilateral vessel (p=0.000). Using the flow index in ROC analysis to predict ischemia on MRI yielded an area under the curve of 0.833 (p=0.002); ROC analysis of the percent of total flow for ischemia on MRI found an AUC of 0.895 (p=0.000).

Conclusion: This study represents the first to assess vessel flow in patients with cervical arterial dissection using QMRA. Patients with lower flow as a result of dissection appear to be at higher risk of ischemia on presentation, emphasizing the role of hemodynamics in the underlying pathophysiology.

External carotid artery to internal carotid artery transposition to augment flow for a superficial temporal artery to middle cerebral artery bypass associated with severe external carotid artery stenosis

BACKGROUND

Donor vessel quality can impact the outcome of extracranial-intracranial (EC-IC) bypass. External carotid artery (ECA) disease may produce embolism into the anastomosis and cerebral territory and possibly reduce flow in the superficial temporal artery (STA). Previously reported remedies to ECA stenosis include ECA endarterectomy, stenting, and angioplasty. Clinical presentation A middle-aged patient with chronic left MCA occlusion, progressive ischemic symptoms on maximal medical therapy, and imaging confirmation of compromised hemodynamic reserve was evaluated for EC-IC bypass. Angiography demonstrated severe ECA origin stenosis. An ECA-ICA transposition was performed, primarily to eliminate the risk of emboli and secondarily to possibly improve the STA flow. The patient sustained an excellent radiological and clinical outcome, and the STA donor cut-flow was increased modestly by 22% (45 to 55 mL/min).

CONCLUSION

This case is the first report of an ECA to internal carotid artery transposition as an option in the management of ECA stenosis in preparation for an STA-MCA bypass for the purpose of flow augmentation.

Prediction of bleb formation in intracranial aneurysms using machine learning models based on aneurysm hemodynamics, geometry, location, and patient population

BACKGROUND

Bleb presence in intracranial aneurysms (IAs) is a known indication of instability and vulnerability.

OBJECTIVE

To develop and evaluate predictive models of bleb development in IAs based on hemodynamics, geometry, anatomical location, and patient population.

METHODS

Cross-sectional data (one time point) of 2395 IAs were used for training bleb formation models using machine learning (random forest, support vector machine, logistic regression, k-nearest neighbor, and bagging). Aneurysm hemodynamics and geometry were characterized using image-based computational fluid dynamics. A separate dataset with 266 aneurysms was used for model evaluation. Model performance was quantified by the area under the receiving operating characteristic curve (AUC), true positive rate (TPR), false positive rate (FPR), precision, and balanced accuracy.

RESULTS

The final model retained 18 variables, including hemodynamic, geometrical, location, multiplicity, and morphology parameters, and patient population. Generally, strong and concentrated inflow jets, high speed, complex and unstable flow patterns, and concentrated, oscillatory, and heterogeneous wall shear stress patterns together with larger, more elongated, and more distorted shapes were associated with bleb formation. The best performance on the validation set was achieved by the random forest model (AUC=0.82, TPR=91%, FPR=36%, misclassification error=27%).

CONCLUSIONS

Based on the premise that aneurysm characteristics prior to bleb formation resemble those derived from vascular reconstructions with their blebs virtually removed, machine learning models can identify aneurysms prone to bleb development with good accuracy. Pending further validation with longitudinal data, these models may prove valuable for assessing the propensity of IAs to progress to vulnerable states and potentially rupturing.

Socioeconomic Inequities in the Surgical Management of Moyamoya Disease

BACKGROUND

Given the vasculopathic nature of moyamoya disease (MMD) and high susceptibility to ischemic events, patients with MMD often require surgical revascularization via an indirect or direct bypass, and analysis of disparities in receipt of appropriate management is critical.

METHODS

The 2012-2016 Nationwide Inpatient Sample was queried for patients admitted with a diagnosis of MMD using International Classification of Diseases codes. Patient baseline demographics, hospital characteristics, and associated symptoms were collected. Patients were grouped by receipt of bypass procedure, and propensity score matching was performed to identify socioeconomic disparities between operative and nonoperative groups.

RESULTS

Inclusion criteria were met by 4474 patients (827 pediatric patients and 3647 adult patients). Mean (SD) age for pediatric patients was 10.4 (4.6) years and for adult patients was 40.5 (14.4) years. Among pediatric patients, Black and Hispanic/Latino patients were less likely to undergo revascularization surgery (odds ratio [OR] 0.49, 95% confidence interval [CI] 0.21-0.78, P ≤ 0.01; OR 0.47, 95% CI 0.26-0.84, P = < 0.01, respectively); among adult patients, Black and Hispanic/Latino patients were similarly less likely to undergo bypass procedures (OR 0.60, 95% CI 0.49-0.72, P ≤ 0.01; OR 0.73, 95% CI 0.55-0.96, P = 0.01, respectively). Pediatric and adult patients in the lowest and next to lowest income quartiles were also less likely to receive operative treatment (pediatric patients: OR 0.61, 95% CI 0.40-0.94, P = 0.02; OR 0.64, 95% CI 0.42-0.98, P = 0.04, respectively; adult patients: OR 0.82, 95% CI 0.88-0.98, P = 0.03).

CONCLUSIONS

Further investigation into socioeconomic disparities in adult and pediatric patients with MMD is warranted given the potential for inequities in access to appropriate intervention.

Comparative efficacy of autologous versus cadaveric saphenous vein grafts in cerebral revascularization surgery

OBJECTIVE

Cerebral bypasses are performed for the purpose of either flow augmentation for ischemic cerebrovascular disease or flow replacement for vessel sacrifice during complex aneurysm or tumor surgery. Saphenous vein grafts (SVGs) are commonly used interposition grafts. The authors of this study sought to compare the efficacy of autologous versus cadaveric SVGs in a large series of cerebral bypasses using interposition vein grafts with long-term angiographic follow-up.

METHODS

All intracranial bypass procedures performed between 2001 and 2018 were reviewed. Demographic, clinical, angiographic, and operative data were recorded and then analyzed according to SVG type.

RESULTS

A total of 308 consecutive intracranial bypasses were performed during the study period, 53 (17.2%) of which were bypasses with an interposition SVG (38 autologous, 15 cadaveric). At a median follow-up of 2.2 months (IQR 0.2–29.1), 39 (73.6%) bypasses were patent (26 [68.4%] autologous, 13 [86.7%] cadaveric, p = 0.30). Comparing autologous and cadaveric SVG recipients, there were no statistically significant differences in age (p = 0.50), sex (p > 0.99), history of smoking (p = 0.75), hypertension (p > 0.99), diabetes mellitus (p = 0.13), indication for bypass (p = 0.27), or SVG diameter (p = 0.65). While there were higher intraoperative (autologous, 100.0 ml/min, IQR 84.3–147.5; cadaveric, 80.0 ml/min, IQR 47.3–107.8; p = 0.11) and postoperative (autologous, 142.2 ml/min, IQR 76.8–160.8; cadaveric, 92.0 ml/min, IQR 69.2–132.2; p = 0.42) volumetric flow rates in the autologous SVGs compared to those in the cadaveric SVGs, the difference between the two groups did not reach statistical significance. In addition, the blood flow index, or ratio of postoperative to intraoperative blood flow, for each bypass was similar between the groups (autologous, 1.3, IQR 0.9–1.6; cadaveric, 1.5, IQR 1.0–2.3; p = 0.37). Kaplan-Meier estimates showed no difference in bypass patency rates over time between autologous and cadaveric SVGs (p = 0.58).

CONCLUSIONS

Cadaveric SVGs are a reasonable interposition graft option in cerebral revascularization surgery when autologous grafts are not available.

Bypass for flow-augmentation in atherosclerotic carotid occlusion: a review of the literature and career experience

Atherosclerosis of the internal carotid artery and intracranial vessels can compromise cerebral hemodynamics and cause stroke. Cerebral bypass has a half-century history in augmenting or replacing blood flow the brain. Several trials have investigated various applications of cerebral bypass in flow augmentation for atherosclerotic disease. This review discusses the clinical science of cerebrovascular atherosclerosis to provide the context in which cerebral bypass is currently applied. This includes prior clinical trials, ongoing clinical trials, and consensus guidelines, and is complemented by studies in the physiologic science of cerebrovascular flow. The scientific background is supplemented by the description of the technical art of bypass surgery based on a three-decade experience. Successful application of cerebral bypass to augment flow in atherosclerotic cerebrovascular disease requires correct diagnosis of compromised hemodynamic reserve refractory to medical optimization and an appropriate matching of bypass flow with cerebral demand.

Onyx embolization for dural arteriovenous fistulas: a multi-institutional study

BACKGROUND

Although the liquid embolic agent, Onyx, is often the preferred embolic treatment for cerebral dural arteriovenous fistulas (DAVFs), there have only been a limited number of single-center studies to evaluate its performance.

OBJECTIVE

To carry out a multicenter study to determine the predictors of complications, obliteration, and functional outcomes associated with primary Onyx embolization of DAVFs.

METHODS

From the Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR) database, we identified patients who were treated for DAVF with Onyx-only embolization as the primary treatment between 2000 and 2013. Obliteration rate after initial embolization was determined based on the final angiographic run. Factors predictive of complete obliteration, complications, and functional independence were evaluated with multivariate logistic regression models.

RESULTS

A total 146 patients with DAVFs were primarily embolized with Onyx. Mean follow-up was 29 months (range 0-129 months). Complete obliteration was achieved in 80 (55%) patients after initial embolization. Major cerebral complications occurred in six patients (4.1%). At last follow-up, 84% patients were functionally independent. Presence of flow symptoms, age over 65, presence of an occipital artery feeder, and preprocedural home anticoagulation use were predictive of non-obliteration. The transverse-sigmoid sinus junction location was associated with fewer complications, whereas the tentorial location was predictive of poor functional outcomes.

CONCLUSIONS

In this multicenter study, we report satisfactory performance of Onyx as a primary DAVF embolic agent. The tentorium remains a more challenging location for DAVF embolization, whereas DAVFs located at the transverse-sigmoid sinus junction are associated with fewer complications.

Perfusion-MRI is a Poor Indicator of Hemodynamic Compromise in Vertebrobasilar Disease in the VERiTAS Study

BACKGROUND AND PURPOSE

Dynamic susceptibility perfusion MR imaging (DSC MRP) has been used to assess changes in cerebral perfusion attributable to vascular stenosis or occlusion that may predict stroke risk. However, DSC MRP is not validated for identifying hemodynamic compromise in the posterior circulation. We investigated the clinical utility of DSC MRP in vertebrobasilar (VB) atherosclerotic disease in the observational VERiTAS study.

METHODS

VERiTAS enrolled patients with symptomatic ≥50% VB stenosis/occlusion. Posterior circulation hemodynamic status was designated as low or normal based on large vessel flow measured using quantitative magnetic resonance angiography (QMRA) and was predictive of future stroke risk. In this study, DSC MRP conducted concurrently with QMRA was used to evaluate posterior circulation perfusion. The primary outcome was the mean transit time (MTT) and relative cerebral blood volume (rCBV) in the posterior circulation normalized to the anterior circulation, compared between patients with low and normal blood flow as determined on QMRA.

RESULTS

Twenty-six subjects had 47 DSC MRP studies for review. There was no statistically or clinically significant difference in the rCBV ratio (1.02 vs. .96 P = .89), or MTT ratio (1.04 vs. 1.04 P = .96) relative to normal or low VB territory flow.

CONCLUSIONS

In this study, we did not find that DSC MRP adequately distinguished between patients with low or normal flow status based on large-vessel flow measurements.

Natural History of Hemodynamics in Vertebrobasilar Disease: Temporal Changes in the VERiTAS Study Cohort

BACKGROUND AND PURPOSE

The role of regional hypoperfusion as a contributor to stroke risk in atherosclerotic vertebrobasilar disease has recently been confirmed by the observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) Study. We examined the stability of hemodynamic status over time and its relationship to stroke risk in patients from this prospective cohort.

METHODS

VERiTAS enrolled patients with recently symptomatic ≥50% atherosclerotic stenosis/occlusion of vertebral and/or basilar arteries. Large vessel flow in the vertebrobasilar territory was assessed using quantitative magnetic resonance angiography, and patients were designated as low or normal flow based on distal territory regional flow, incorporating collateral capacity. Patients underwent standard medical management and follow-up for primary outcome event of vertebrobasilar territory stroke. Quantitative magnetic resonance angiography imaging was repeated at 6, 12, and 24 months. Flow status over time was examined relative to baseline and relative to subsequent stroke risk using a cause-specific proportional hazard model, with flow status treated as a time-varying covariate. Mean blood pressure was examined to assess for association with changes in flow status.

RESULTS

Over 19±8 months of follow-up, 132 follow-up quantitative magnetic resonance angiography studies were performed in 58 of the 72 enrolled patients. Of the 13 patients with serial imaging who had low flow at baseline, 7 (54%) had improvement to normal flow at the last follow-up. Of the 45 patients who had normal flow at baseline, 3 (7%) converted to low flow at the last follow-up. The mean blood pressure did not differ in patients with or without changes in flow status. The time-varying flow status remained a strong predictor of subsequent stroke (hazard ratio, 10.3 [95% CI, 2.2-48.7]).

CONCLUSIONS

There is potential both for improvement and worsening of hemodynamics in patients with atherosclerotic vertebrobasilar disease. Flow status, both at baseline and over time, is a risk factor for subsequent stroke, thus serving as an important prognostic marker. Registration: URL: https://clinicaltrials.gov. Unique identifier: NCT00590980.

Hemodynamics in aneurysm blebs with different wall characteristics

BACKGROUND

Blebs are important secondary structures of intracranial aneurysms associated with increased rupture risk and can affect local wall stress and hemodynamics. Mechanisms of bleb development and evolution are not clearly understood. We investigate the relationship between blebs with different wall characteristics and local hemodynamics and rupture sites.

METHODS

Blebs with different wall appearances in intra-operative videos were analyzed with image-based computational fluid dynamics. Thin red blebs were compared against thick atherosclerotic/hyperplastic white/yellow blebs. Rupture points were identified in videos of ruptured aneurysms harboring blebs.

RESULTS

Thin blebs tended to be closer to the inflow than atherosclerotic blebs of the same aneurysm (P=0.0234). Blebs near the inflow had higher velocity (P=0.0213), vorticity (P=0.0057), shear strain rate (P=0.0084), wall shear stress (WSS) (P=0.0085), and WSS gradient (P=0.0151) than blebs far from the inflow. In a subset of 12 ruptured aneurysms harboring blebs, rupture points were associated with thin blebs in 42% of aneurysms, atherosclerotic blebs in 25%, and were away from blebs in the remaining 33%.

CONCLUSIONS

Not all blebs are equal; some have thin translucent walls while others have thick atherosclerotic walls. Thin blebs tend to be located closer to the inflow than atherosclerotic blebs. Blebs near the inflow are exposed to stronger flows with higher and spatially variable WSS than blebs far from the inflow which tend to have uniformly lower WSS. Aneurysms can rupture at thin blebs, atherosclerotic blebs, and even away from blebs. Further study of wall failure in aneurysms with different bleb types is needed.

Final Results of the Prospective Multicenter Excimer Laser-Assisted High-Flow Bypass Study on the Treatment of Giant Anterior Circulation Aneurysms

BACKGROUND

Both conventional bypass utilizing temporary recipient vessel occlusion and the excimer laser-assisted nonocclusive anastomosis (ELANA) bypass technique are possible strategies in the treatment of giant aneurysms. These treatments have only been studied in single institutional retrospective studies. The potential advantage of the ELANA technique is the absence of temporary occlusion of major arteries, decreasing the risk of intraoperative ischemia.

OBJECTIVE

To investigate the risks and potential benefits of high-flow bypass surgery for giant and complex aneurysms of the anterior cerebral circulation. In addition, the effectiveness of the ELANA bypass procedure in the treatment of these aneurysms is determined.

METHODS

A total of 37 patients were included in 8 vascular neurosurgical centers in the United States, Canada, and Europe. A 30-d postoperative bypass follow-up was studied by using digital subtraction angiography and/or magnetic resonance angiography and computed tomography angiography to assess patency as well as by clinical monitoring in all patients.

RESULTS

In 35 patients, an ELANA high-flow bypass was performed and the aneurysm treated. Four patients had remaining neurological deficits after 30 d caused by stroke (11.4%). These strokes were not related to the ELANA anastomosis device.

CONCLUSION

This study does not prove that the ELANA technique has an advantage over conventional bypass techniques, but it appears to be an acceptable alternative to conventional transplanted high-flow bypass in this very-difficult-to-treat patient group, especially in select patients whom cannot be bypassed using conventional means in which temporary occlusion is considered to be not recommended.

Morbidity and mortality associated with sequential flow reduction embolization technique of cerebral arteriovenous malformations using n-butyl cyanoacrylate

BACKGROUND

Endovascular embolization of cerebral arteriovenous malformations (AVM) with liquid n-butyl cyanoacrylate (n-BCA) serves multiple purposes including AVM occlusion and flow reduction in preparation for other treatment modalities. The objective was to study the clinical, structural, and angiographic factors affecting complications associated with AVM treatment by sequential n-BCA embolizations for nidal occlusion versus quantitative flow reduction in preparation for surgical resection or radiosurgery.

METHODS

We performed a retrospective review of all patients who underwent endovascular embolization of cerebral AVM at our institution between 1998 and 2019, during which time the technique of traditional embolization evolved to a strategy of targeted sequential flow reduction guided by serial flow imaging based on quantitative magnetic resonance angiography, in conjunction with a shift away from nidal penetration.

RESULTS

Among 251 patients, 47.8% of patients presented with ruptured AVM. On average, each patient underwent 2.4 embolizations, for a total of 613 sessions. Major morbidity related to embolization occurred in 18 (7.2%) patients, but this occurred disproportionately in the traditional embolization strategy (n=16, 8%) in contrast with the flow-targeting strategy (n=2, 3.8%). Four patients (1.6%) died in the overall group, and these all occurred with the traditional embolization strategy (2% of 199 patients); no deaths occurred in the flow-targeting strategy (n=52).

CONCLUSION

Embolization with n-BCA targeted to sequential flow reduction and feeder occlusion with limited nidal penetration prior to definitive surgical or radiosurgical treatment can be safely performed with low overall morbidity and mortality.

Blebs in intracranial aneurysms: prevalence and general characteristics

BACKGROUND

Blebs are rupture risk factors in intracranial aneurysms (IAs), but their prevalence, distribution, and associations with clinical factors as well as their causes and effects on aneurysm vulnerability remain unclear.

METHODS

A total of 122 blebs in 270 IAs selected for surgery were studied using patient-specific vascular reconstructions from 3D angiographic images. Bleb geometry, location on the aneurysm, and frequency of occurrence in aneurysms at different locations were analyzed. Associations between gender, age, smoking, hypertension, hormone therapy, dental infection, and presence of blebs were investigated.

RESULTS

Of all aneurysms with blebs, 77% had a single bleb and 23% had multiple blebs. Only 6% of blebs were at the neck, while 46% were in the body and 48% in the dome. Aneurysms with blebs were larger (p<0.0001), more elongated (p=0.0002), and with wider necks than aneurysms without blebs. Bleb presence was associated with dental infection (p=0.0426) and negatively associated with hormone therapy (p=0.0426) in women. Anterior and posterior communicating arteries had larger percentages of aneurysms with blebs than internal carotid arteries. Patients with a history of hypertension tended to have a larger percentage of aneurysms with blebs. However, these trends did not reach significance in this sample.

CONCLUSIONS

Blebs are common in IAs, and most aneurysms harboring blebs have a single bleb. Blebs in the aneurysm neck are rare, but they are equally common in the body and dome. The presence of blebs in IAs was associated with dental infection, and negatively associated with hormone replacement therapy.

A New Scoring System for Prediction of Underlying Vascular Pathology in Patients with Intracerebral Hemorrhage: The Modified Secondary Intracerebral Hemorrhage Score

BACKGROUND

Secondary intracerebral hemorrhage (SICH) score is used to predict risk of intracranial hemorrhage (ICH) associated vascular lesions. However, it has low clinical utility in identifying patients without need for neurovascular imaging. This study aims to develop a modified scoring system to capture patients with low risk of underlying vascular pathology, thereby decreasing need for vascular imaging and its associated morbidity.

METHODS

A retrospective analysis of 994 patients with atraumatic ICH over 8 years was conducted, excluding known underlying pathology, subarachnoid hemorrhage, or lack of vascular imaging. Using a multivariate logistic regression model, independent predictors of vascular pathology were identified and utilized toward developing a modified Secondary Intracerebral Hemorrhage (mSICH) score.

RESULTS

Of 575 patients identified, 60 (10.4%) had underlying vascular etiology. Statistically significant predictors of vascular pathology included age; female sex; admission systolic blood pressure <160 mm Hg; locations other than basal ganglia, thalamus, pons, or midbrain; presence of high-risk imaging features; and proximity to large vessel-containing cisterns. The mSICH score correlated with an increasing incidence of vascular pathology [0-1 (0%), 9 (4.3%), 12 (9.7%), 21 (40.4%), 6 (33.3%), 8 (88.9%), and 4 (100%)] and had a significantly higher number of patients receiving scores with 0% incidence of vascular lesions compared with the SICH score [159 (27.6%) versus 12 (2.1%); P < 0.001)].

CONCLUSIONS

The mSICH score can more accurately predict risk of underlying vascular pathology of ICH and identify patients with lowest risk of vascular pathology. This may minimize the cost and associated risks of invasive cerebrovascular imaging.

Optimized Hemodynamic Assessment to Predict Stroke Risk in Vertebrobasilar Disease: Analysis From the VERiTAS Study

Background Atherosclerotic vertebrobasilar disease is a significant etiology of posterior circulation stroke. The prospective observational VERiTAS (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke) study demonstrated that distal hemodynamic status is a robust predictor of subsequent vertebrobasilar stroke risk. We sought to compare predictive models using thresholds for posterior circulation vessel flows standardized to age and vascular anatomy to optimize risk prediction. Methods and Results VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis/occlusion in vertebral and/or basilar arteries. Quantitative magnetic resonance angiography measured large-vessel vertebrobasilar territory flow, and patients were designated as low or normal flow based on a prespecified empiric algorithm considering distal territory regional flow and collateral capacity. For the present study, post hoc analysis was performed to generate additional predictive models using age-specific normalized flow measurements. Sensitivity, specificity, and time-to-event analyses were compared between the algorithms. The original prespecified algorithm had 50% sensitivity and 79% specificity for future stroke risk prediction; using a predictive model based on age-normalized flows in the basilar and posterior cerebral arteries, standardized to vascular anatomy, optimized flow status thresholds were identified. The optimized algorithm maintained sensitivity and increased specificity to 84%, while demonstrating a larger and more significant hazard ratio for stroke on time-to-event analysis. Conclusions These results indicate that flow remains a strong predictor of stroke across different predictive models, and suggest that prediction of future stroke risk can be optimized by use of vascular anatomy and age-specific normalized flows.

Occlusion of Extracranial-Intracranial Bypass Anastomosis-Associated Aneurysms Following Contralateral High-Flow Extracranial-Intracranial Bypass in a Patient with Impaired Cerebrovascular Reserve

BACKGROUND AND IMPORTANCE

Extracranial-intracranial (EC-IC) bypass anastomosis-associated aneurysms are rare sequelae of cerebral revascularization surgery. Although treatment paradigms are not well defined, clipping, trapping with revision bypass, and donor vessel ligation represent the most common microsurgical approaches.

CLINICAL PRESENTATION

A 53-yr-old male presented with cognitive decline, left extremity weakness, and left visual field blurriness. Computed tomographic angiography of head/neck demonstrated bilateral cervical internal carotid artery occlusion and magnetic resonance imaging of brain showed a small right parieto-occipital lobe infarct. The patient's symptoms worsened despite aggressive medical management. Therefore, a right superficial temporal artery to middle cerebral artery (STA-MCA) bypass was performed for flow augmentation. Follow-up digital subtraction angiography (DSA) approximately 1 yr after surgery noted 2 new aneurysms adjacent to the patent STA-MCA anastomosis. Perfusion imaging at that time showed persistently reduced blood flow in the left cerebral hemisphere. A left STA-MCA bypass was performed, and intraoperative blood flow measurements showed this to be a high-flow bypass. Follow-up DSA 4 mo later demonstrated involution of the right STA-MCA bypass and occlusion of the anastomosis-associated aneurysms with increased perfusion of the right cerebral hemisphere via collateral blood flow from the patent high-flow left STA-MCA bypass. At 7 mo following left STA-MCA bypass, the patient's neurological examination remained stable and perfusion imaging showed improved blood flow in the left cerebral hemisphere.

CONCLUSION

We present a unique case in which a high-flow left EC-IC bypass with robust contralateral collateral blood flow was associated with subsequent occlusion of a right EC-IC bypass and 2 anastomosis-associated aneurysms in a patient with bilateral impaired cerebrovascular reserve.

Submaximal Angioplasty for Symptomatic Intracranial Atherosclerotic Disease: A Meta-Analysis of Peri-Procedural and Long-Term Risk

BACKGROUND

Symptomatic intracranial atherosclerotic disease (ICAD) is an important cause of stroke. Although the high periprocedural risk of intracranial stenting from recent randomized studies has dampened enthusiasm for such interventions, submaximal angioplasty without stenting may represent a safer endovascular treatment option.

OBJECTIVE

To examine the periprocedural and long-term risks associated with submaximal angioplasty for ICAD based on the available literature.

METHODS

All English language studies of intracranial angioplasty for ICAD were screened. Inclusion criteria were as follows: ≥ 5 patients, intervention with submaximal angioplasty alone, and identifiable periprocedural (30-d) outcomes. Analysis was co-nducted to identify the following: 1) periprocedural risk of any stroke (ischemic or hemorrh-agic) or death, and 2) stroke in the territory of the target vessel and fatal stroke beyond 30 d. Mixed effects logistic regression was used to summarize event rates. Funnel plot and rank correlation tests were employed to detect publication bias. The relative risk of periprocedural events from anterior vs posterior circulation disease intervention was also examined.

RESULTS

A total of 9 studies with 408 interventions in 395 patients met inclusion criteria. Six of these studies included 113 posterior circulation interventions. The estimated pooled rate for 30-d stroke or death following submaximal angioplasty was 4.9% (95% CI: 3.2%-7.5%), whereas the estimated pooled rate beyond 30 d was 3.7% (95% CI: 2.2%-6.0%). There was no statistical difference in estimated pooled rate for 30-d stroke or death between patients with anterior (4.8%, 95% CI: 2.8%-7.9%) vs posterior (5.3%, 95% CI: 2.4%-11.3%) circulation disease (P > .99).

CONCLUSION

Submaximal angioplasty represents a potentially promising intervention for symptomatic ICAD.

Quantification of blood flow patterns in the cerebral arterial circulation of individual (human) subjects

There is a growing research interest in quantifying blood flow distribution for the entire cerebral circulation to sharpen diagnosis and improve treatment options for cerebrovascular disease of individual patients. We present a methodology to reconstruct subject-specific cerebral blood flow patterns in accordance with physiological and fluid mechanical principles and optimally informed by in vivo neuroimage data of cerebrovascular anatomy and arterial blood flow rates. We propose an inverse problem to infer blood flow distribution across the visible portion of the arterial network that best matches subject-specific anatomy and a given set of volumetric flow measurements. The optimization technique also mitigates the effect of uncertainties by reconciling incomplete flow data and by dissipating unavoidable acquisition errors associated with medical imaging data.

Infarct Patterns in Patients with Atherosclerotic Vertebrobasilar Disease in Relation to Hemodynamics

Introduction

Distal territory blood flow is independently associated with subsequent strokes in symptomatic vertebrobasilar atherosclerotic disease. We aimed to assess infarct patterns in relation to hemodynamic status in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study.

Methods

Distal territory blood flow was measured using quantitative magnetic resonance angiography (MRA) in 72 patients with symptomatic atherosclerotic vertebrobasilar disease, and then dichotomized into normal (n = 54) and low (n = 18) flow. Patients were followed longitudinally on standard medical management. Two observers blinded to flow status independently reviewed the imaging performed at the time of subsequent strokes, in order to adjudicate the likely mechanism based on infarct patterns. The frequency of stroke mechanisms was qualitatively compared based on flow status.

Results

During a median follow-up period of 23 months, 10/72 patients had a subsequent stroke; 5 of these had low distal flow. Infarct patterns were adjudicated to be consistent with hemodynamic (n = 2), embolic (n = 4), and junctional plaque/perforator (n = 4) infarcts. Hemodynamic infarcts were seen in 40% (2/5) low-flow patients, in comparison to 0% (0/5) normal-flow patients.

Conclusion

In contrast to normal-flow patients, those with low distal flow seem to be uniquely susceptible to hemodynamic infarctions, although other patterns of infarction can also be seen in these hemodynamically impaired patients.

Hypoperfusion Symptoms Poorly Predict Hemodynamic Compromise and Stroke Risk in Vertebrobasilar Disease

Background and Purpose- Cerebral hypoperfusion symptoms (defined as symptoms related to change in position, effort or exertion, or recent change in antihypertensive medication) have been used in stroke studies as a surrogate for detecting hemodynamic compromise. However, the validity of these symptoms in identifying flow compromise in patients has not been well established. We examined whether hypoperfusion symptoms correlated with quantitative measurements of flow compromise in the prospective, observational VERiTAS study (Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke). Methods- VERiTAS enrolled patients with recent vertebrobasilar transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion in vertebral or basilar arteries. Hemodynamic status using vertebrobasilar large vessel flow was measured using quantitative magnetic resonance angiography, and patients were designated as low, borderline, or normal flow based on distal territory regional flow, incorporating collateral capacity. The presence of qualifying event hypoperfusion symptoms was assessed relative to the quantitatively determined flow status (normal versus borderline/low) and also examined as a predictor of subsequent stroke risk. Results- Of the 72 enrolled subjects, 66 had data on hypoperfusion symptoms available. On initial quantitative magnetic resonance angiography designation, 43 subjects were designated as normal flow versus 23 subjects designated as low flow (n=16) or borderline flow (n=7). Of these, 5 (11.6%) normal flow and 3 (13.0%) low/borderline flow subjects reported at least one qualifying event hypoperfusion symptom ( P=0.99, Fisher exact test). Hypoperfusion symptoms had a positive predictive value of 37.5% and negative predictive value of 65.5% for low/borderline flow status. Compared with flow status, which strongly predicted subsequent stroke risk, hypoperfusion symptoms were not associated with stroke outcome ( P=0.87, log-rank test). Conclusions- These results suggest that hypoperfusion symptoms alone correlate poorly with actual hemodynamic compromise as assessed by quantitative magnetic resonance angiography and subsequent stroke risk in vertebrobasilar disease, and are not a reliable surrogate for flow measurement. Clinical Trial Registration- URL: https://www.clinicaltrials.gov . Unique identifier: NCT00590980.

Contrast Time-Density Time on Digital Subtraction Angiography Correlates With Cerebral Arteriovenous Malformation Flow Measured by Quantitative Magnetic Resonance Angiography, Angioarchitecture, and Hemorrhage

BACKGROUND

Digital subtraction angiography (DSA) currently provides angioarchitectural features of cerebral arteriovenous malformations (AVMs) but its role in the hemodynamic evaluation of AVMs is poorly understood.

OBJECTIVE

To assess contrast time-density time (TT) on DSA relative to AVM flow measured using quantitative magnetic resonance angiography (QMRA).

METHODS

Patients seen at our institution between 2007 and 2014 with a supratentorial AVM and DSA and QMRA obtained prior to any treatment were retrospectively reviewed. Regions of interest were selected on the draining veins at the point closest to the nidus. TT on DSA was defined as time needed for contrast to change image intensity from 10% to 100%, 100% to 10%, and 25% to 25%. TT was correlated to AVM total flow, angioarchitectural features, and hemorrhage.

RESULTS

Twenty-eight patients (mean age 35.6 yr) were included. Six patients presented with hemorrhage. Mean AVM volume was 11.42 mL (range 0.3-57.7 mL). Higher total AVM flow significantly correlated with shorter TT100%-10% and TT25%-25% (P = .02, .02, respectively). Presence of venous stenosis correlated significantly with shorter TT100%-10% (P = .04) and TT25%-25% (P = .04). AVMs with a single draining vein exhibited longer TT25%-25% compared to those with multiple draining veins (P = .04). Ruptured AVMs had significantly shorter TT10%-100% compared to unruptured AVMs (P = .05).

CONCLUSION

TT on DSA correlates with cerebral AVM flow measured using QMRA and with AVM angioarchitecture and hemorrhagic presentation. Thus, TT may be used to indirectly estimate AVM flow during angiography in real-time and may also be an indicator of important AVM characteristics associated with outflow resistance and increased rupture risk, such as venous stenosis.

The cut flow index revisited: utility of intraoperative blood flow measurements in extracranial-intracranial bypass surgery for ischemic cerebrovascular disease

OBJECTIVE

In extracranial-intracranial (EC-IC) bypass surgery, the cut flow index (CFI) is the ratio of bypass flow (ml/min) to donor vessel cut flow (ml/min), and a CFI ≥ 0.5 has been shown to correlate with bypass patency. The authors sought to validate this observation in a large cohort of EC-IC bypasses for ischemic cerebrovascular disease with long-term angiographic follow-up.

METHODS

All intracranial bypass procedures performed at a single institution between 2003 and 2018 were reviewed. Demographic, clinical, angiographic, and operative data were recorded and analyzed according to bypass patency with univariate and multivariate statistical analyses.

RESULTS

A total of 278 consecutive intracranial bypasses were performed during the study period, of which 157 (56.5%) were EC-IC bypasses for ischemic cerebrovascular disease. Intraoperative blood flow measurements were available in 146 patients, and angiographic follow-up was available at a mean of 2.1 ± 2.6 years after bypass. The mean CFI was significantly higher in patients with patent bypasses (0.92 vs 0.64, p = 0.003). The bypass patency rate was 83.1% in cases with a CFI ≥ 0.5 compared with 46.4% in cases with a CFI < 0.5 (p < 0.0001). Adjusting for age, sex, diagnosis, and single versus double anastomosis, the CFI remained a significant predictor of bypass patency (p = 0.001; OR 5.8, 95% CI 2.0-19.0). A low CFI was also associated with early versus late bypass nonpatency (p = 0.008).

CONCLUSIONS

A favorable CFI portends long-term EC-IC bypass patency, while a poor CFI predicts eventual bypass nonpatency and can alert surgeons to potential problems with the donor vessel, anastomosis, or recipient bed during surgery.

Calcification in Human Intracranial Aneurysms Is Highly Prevalent and Displays Both Atherosclerotic and Nonatherosclerotic Types

OBJECTIVE

Although the clinical and biological importance of calcification is well recognized for the extracerebral vasculature, its role in cerebral vascular disease, particularly, intracranial aneurysms (IAs), remains poorly understood. Extracerebrally, 2 distinct mechanisms drive calcification, a nonatherosclerotic, rapid mineralization in the media and a slower, inflammation driven, atherosclerotic mechanism in the intima. This study aims to determine the prevalence, distribution, and type (atherosclerotic, nonatherosclerotic) of calcification in IAs and assess differences in occurrence between ruptured and unruptured IAs. Approach and Results: Sixty-five 65 IA specimens (48 unruptured, 17 ruptured) were resected perioperatively. Calcification and lipid pools were analyzed nondestructively in intact samples using high resolution (0.35 μm) microcomputed tomography. Calcification is highly prevalent (78%) appearing as micro (<500 µm), meso (500 µm-1 mm), and macro (>1 mm) calcifications. Calcification manifests in IAs as both nonatherosclerotic (calcification distinct from lipid pools) and atherosclerotic (calcification in the presence of lipid pools) with 3 wall types: Type I-only calcification, no lipid pools (20/51, 39%), Type II-calcification and lipid pools, not colocalized (19/51, 37%), Type III-calcification colocalized with lipid pools (12/51, 24%). Ruptured IAs either had no calcifications or had nonatherosclerotic micro- or meso-calcifications (Type I or II), without macro-calcifications.

CONCLUSIONS

Calcification in IAs is substantially more prevalent than previously reported and presents as both nonatherosclerotic and atherosclerotic types. Notably, ruptured aneurysms had only nonatherosclerotic calcification, had significantly lower calcification fraction, and did not contain macrocalcifications. Improved understanding of the role of calcification in IA pathology should lead to new therapeutic targets.

Role of Resistivity Index Analysis in the Prediction of Hemodynamically Significant Venous Sinus Stenosis in Patient With Idiopathic Intracranial Hypertension

BACKGROUND

The resistivity index (RI) in cerebral venous sinus stenosis (VSS) has not been studied in patients with idiopathic intracranial hypertension (IIH).

OBJECTIVE

To evaluate the role of RI measured by quantitative magnetic resonance venogram (QMRV) as a noninvasive tool in the diagnosis of venous hypertension associated with VSS in IIH.

METHODS

Retrospective evaluation of 13 consecutive IIH patients who underwent venous sinus stenting at our institution between 2013 and 2018.

Patients’ demographics, clinical presentation, cerebral mean venous sinus pressure (MVP), and RI both pre- and poststenting were recorded. The baseline RI was also compared to a control group.

RESULTS

Among 13 patients of IIH, 11 had unilateral VSS in dominant sinus, whereas 2 had bilateral VSS. RI was significantly higher in IIH patients compared to the control group in the superior sagittal (SSS) and transverse sinuses (TS) (0.21 vs 0.11, P = .01 and 0.22 vs 0.13, P = .03, respectively). The MVP (in mm Hg) decreased significantly after venous sinus stenting in the SSS (41.9 to 22.5, P &lt; .001) and TS (39.4 to 19.5, P &lt; .001), which was also associated with a significant reduction of the RI (0.22 vs 0.17, P &lt; .01 in SSS and 0.23 vs 0.17, P = .03 in TS) poststenting.

CONCLUSION

RI calculated using QMRV can serve as a noninvasive tool to aid in the diagnosis of hemodynamically significant VSS. The study had a small sample size, and larger multicenter studies would be required to validate the results further.

Ratio of Arteriovenous Malformation Draining Vein to Adjacent Venous Sinus Diameter Is Associated with Increased Risk of Venous Stenosis

BACKGROUND

The development of venous outflow stenosis in cerebral arteriovenous malformation (AVM) is poorly understood. The location of stenosis within the AVM draining vein in relation to the adjacent venous sinus and the hypothesis that the ratio of draining vein to adjacent sinus diameter might predict the development of venous stenosis were explored.

METHODS

Patients with supratentorial AVMs (1997-2018) were reviewed (N = 290). AVM draining vein and adjacent venous sinus diameters, degree of draining vein stenosis, and distance from the maximal stenotic point to the junction of the adjacent draining sinus were recorded. Correlation between percentage of AVM draining vein stenosis and the ratio of AVM draining vein to venous sinus diameters was analyzed.

RESULTS

A total of 360 draining veins in 243 AVMs with complete angiographic data were measured. Venous stenosis (in 131 draining veins) was observed within 20 mm of the junction to the adjacent draining sinus in 85% of our sample. The ratio of draining vein to adjacent sinus diameter correlated positively with the percentage of venous stenosis (P < 0.01, r = 0.21). The ratio between 0.51-1.0 and >1.0 showed significant tighter stenosis compared with the ratio ≤0.5 (25.9% and 28.9% vs. 10.0%, respectively; P < 0.01).

CONCLUSIONS

AVM venous outflow stenosis is observed close to the adjacent venous sinus junction. The degree of venous stenosis is greater when the ratio of AVM draining vein/adjacent venous sinus diameter is >0.5. This may be related to more turbulent flow at the junction of the draining vein and venous sinus, especially in larger draining veins, which causes venous stenosis to develop over time.