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Background: Flow-diverting devices (FDDs), such as the Pipeline Embolization Device, have been gaining traction for treating challenging posterior circulation aneurysms. Few previous studies have focused on using FDDs to treat aneurysms of the basilar quadrifurcation., Methods: We retrospectively reviewed the use of FDDs to treat patients with basilar quadrifurcation aneurysms. Patients were assessed for aneurysm type, previous aneurysm treatment, technical success, periprocedural complications, and long-term aneurysm occlusion., Results: 34 patients were assessed; aneurysms of the basilar apex (n=23) or superior cerebellar artery (SCA) (n=7), or both (n=1), and posterior cerebral artery (PCA) (n=3). The mean (SD) largest aneurysm dimension was 8.7 (6.1) mm (range 1.9-30.8 mm). 14 aneurysms were previously surgically clipped or endovascularly coiled. All aneurysms had a saccular morphology. Complete or near-complete occlusion was achieved in 30 of 34 patients (88%) at final angiographic follow-up, a mean (SD) of 6.6 (5.4) months (range 0-19 months) postoperatively. No patient experienced postoperative symptomatic occlusions of the SCA or PCA; 4 patients developed asymptomatic posterior communicating artery occlusions; 28 patients (82%) experienced no complications; whereas 3 (9%) experienced major complications and 3 (9%) experienced minor complications; and 1 patient died as a result of subarachnoid hemorrhage., Conclusion: Flow diversion may be a safe and effective option to treat basilar quadrifurcation aneurysms. Previously treated basilar quadrifurcation aneurysms with recurrence or residual lesion may benefit from additional treatment with an FDD. Further prospective studies should be directed toward validating these findings., Competing Interests: Competing interests: Dr Ducruet is a consultant for Penumbra, Medtronic, Stryker, Cerenovus, and Koswire. Drs Ducruet and Albuquerque serve on the editorial board of the Journal of NeuroInterventional Surgery. Content included in this article was presented as a digital poster at the American Association of Neurological Surgeons Annual Meeting, April 29–May 1, 2022, in Philadelphia, PA., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Basilar artery (BA) fenestration aneurysm (BAFA) is a rare phenomenon commonly accompanying other aneurysms. Treatment is challenging, and few cases have been reported. This review investigated the management outcomes of BAFAs., Methods: Publication databases were searched to identify studies evaluating outcomes of endovascular treatment (EVT) and microsurgical treatment of BAFAs from inception through 2021. Outcomes (clinical, angiographic, postoperative complications, and retreatment rates) were collected and analyzed. The authors present their case of a patient treated for a BAFA., Results: Including the authors' case, 184 patients with 209 BAFAs were reported in 68 studies. Most patients (130/175; 74.3%) presented with ruptured aneurysms, most commonly involving the proximal segment of the BA. Most BAFAs were small (52/103, 50.5%) and saccular (119/143, 83.2%). Most patients underwent EVT (143/184, 77.7%); the rest underwent microsurgery. Postoperative complications after EVT occurred in 10 (8.3%) of 120 patients, with 4 of the 10 experiencing strokes. At clinical follow-up, most EVT patients (74/86, 86.0%) showed good outcomes; 3.9% (2/51) had died. Most aneurysms managed with EVT (56/73, 76.7%) showed complete occlusion at follow-up; 7.3% (8/109) were retreated. Postoperative complications occurred in 62.2% (23/37) of microsurgical patients; 5 (21.7%) of the 23 experienced strokes. All patients showed good clinical outcomes at follow-up. Most aneurysms (22/28, 78.6%) treated microsurgically showed complete occlusion at angiographic follow-up, with no retreatment required., Conclusion: BAFAs are often symptomatic; thus, treatment is challenging. By the 2000s, treatment had moved from microsurgical to endovascular modalities, with good clinical and angiographic outcomes., Competing Interests: Competing interests: FCA and AFD are on the editorial board for Journal of NeuroInterventional Surgery. No prior submissions or presentations., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: This study aims to define the proportion of Medicare neuroendovascular procedures performed by different specialists from 2013 to 2019, map the geographic distribution of these specialists, and trend reimbursement for these procedures., Methods: The Medicare Provider Utilization Database was queried for recognized neuroendovascular procedures. Data on specialists and their geographic distribution were tabulated. Reimbursement data were gathered using the Physician Fee Schedule Look-Up Tool and adjusted for inflation using the United States Bureau of Labor Statistics' Consumer Price Index Inflation calculator., Results: The neuroendovascular workforce in 2013 and 2019, respectively, was as follows: radiologists (46% vs 44%), neurosurgeons (45% vs 35%), and neurologists (9% vs 21%). Neurologists increased proportionally (p=0.03). Overall procedure numbers increased across each specialty: radiology (360%; p=0.02), neurosurgery (270%; p<0.01), and neurology (1070%; p=0.03). Neuroendovascular revascularization (CPT 61645) increased in all fields: radiology (170%; p<0.01), neurosurgery (280%; p<0.01), neurology (240%; p<0.01); central nervous system (CNS) permanent occlusion/embolization (CPT61624) in neurosurgery (67%; p=0.03); endovascular temporary balloon artery occlusion (CPT61623) in neurology (29%; p=0.04). In 2019, radiologists were the most common neuroendovascular specialists everywhere except in the Northeast where neurosurgeons predominated. Inflation adjusted reimbursement decreased for endovascular temporary balloon occlusion (CPT61623, -13%; p=0.01), CNS transcatheter permanent occlusion or embolization (CPT61624, -13%; p=0.02), non-CNS transcatheter permanent occlusion or embolization (CPT61626, -12%; p<0.01), and intracranial stent placement (CPT61635, -12%; p=0.05)., Conclusions: The number of neuroendovascular procedures and specialists increased, with neurologists becoming more predominant. Reimbursement decreased. Coordination among neuroendovascular specialists in terms of training and practice location may maximize access to acute care., Competing Interests: Competing interests: YME receives a grant from the National Institutes of Health for a study in neurology: Expanding insights into FTD disease mechanisms (R35NS097273-01). JFM is chair of the NeuroNEXT Data Safety Monitoring Board and receives grants from the National Institutes of Health for several studies related to stroke: CREST-2 Clinical Coordinating Center (U01NS080168), CREST-2 Long-term Observational Extension (U01NS119169), and DISCOVERY Recruitment and Retention Core (U19NS115388). SS is a stockholder and board member of StrokeDx., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Ruptured anterior communicating artery (ACoA) aneurysms can be challenging to treat via an endovascular procedure. This study analyzed retreatment rates and neurological outcomes associated with ruptured ACoA aneurysms treated via endovascular coiling., Methods: All patients with a ruptured ACoA aneurysm treated with endovascular coiling from 2003 to 2019 were retrospectively analyzed at a single center. Two comparisons were performed: no retreatment versus retreatment and coil embolization versus balloon-assisted coil embolization. Outcomes included retreatment and neurological outcome assessed via modified Rankin Scale (mRS)., Results: During the study period, 186 patients with ruptured ACoA aneurysms underwent coil embolization. Treatment included standard coil embolization (68.3%, n=127), balloon-assisted coiling (28.5%, n=53), and stent-assisted embolization (2.7%, n=5). Angiographic outcomes were as follows: class I, 65.1% (n=121); class II, 28.5% (n=53); and class III, 6.5% (n=12). There were no aneurysm reruptures after the index procedure. The mean (SD) mRS score was 2.7 (2.0) at last follow-up (mortality, 19 (10%)). Retreatment occurred in 9.7% (n=18). Patients with retreatment were younger with lower-grade subarachnoid hemorrhage and more favorable functional status at discharge. Patients with aneurysms >7 mm (n=36) were significantly more likely to have recurrence (22.2% vs 6.7%, P=0.005)., Conclusions: Endovascular treatment of ruptured ACoA aneurysms is safe and is associated with low mortality and retreatment rates. Younger patients with favorable functional status and larger aneurysm size are more likely to be retreated. Ruptured aneurysms <4 mm, although prevalent in the study (29%), never required retreatment., Competing Interests: Competing interests: AFD and FCA serve on the editorial board of Journal of NeuroInterventional Surgery. The other authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this manuscript., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: In specialized neurosurgical centers, open microsurgery is routinely performed for aneurysmal subarachnoid hemorrhage (aSAH)., Objective: To compare the cost of endovascular vs microsurgical treatment for aSAH at a single quaternary center., Methods: All patients undergoing aSAH treatment from July 1, 2014, to July 31, 2019, were retrospectively reviewed. Patients were grouped based on primary treatment (microsurgery vs endovascular treatment). The primary outcome was the difference in total cost (including hospital, discharge facility, and all follow-up) using a propensity-adjusted analysis., Results: Of 384 patients treated for an aSAH, 234 (61%) were microsurgically treated and 150 (39%) were endovascularly treated. The mean cost of index hospitalization for these patients was marginally higher ($9504) for endovascularly treated patients ($103 980) than for microsurgically treated patients ($94 476) ( P = .047). For the subset of patients with follow-up data available, the mean total cost was $45 040 higher for endovascularly treated patients ($159 406, n = 59) than that for microsurgically treated patients ($114 366, n = 105) ( P < .001). After propensity scoring (adjusted for age, sex, comorbidities, Glasgow Coma Scale score, Hunt and Hess grade, Fisher grade, aneurysms, and type/size/location), linear regression analysis of patients with follow-up data available revealed that microsurgery was independently associated with healthcare costs that were $37 244 less than endovascular treatment costs ( P < .001). An itemized cost analysis suggested that this discrepancy was due to differences in the rates of aneurysm retreatment and long-term surveillance., Conclusion: Microsurgical treatment for aSAH is associated with lower total healthcare costs than endovascular therapy. Aneurysm surveillance after endovascular treatments, retreatment, and device costs warrants attention in future studies., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: The Woven EndoBridge (WEB) device (Terumno Corp. [parent company of Microvention]) was approved by the U.S. Food and Drug Administration as the first intrasaccular device for intracranial aneurysm treatment in December 2018. Its use has become more common since then, but both trial results and postmarket experiences have raised questions about the efficacy in achieving complete aneurysm obliteration. Retreatment after WEB embolization has not been extensively discussed., Objective: To discuss the incidence and retreatment of aneurysms after initial WEB embolization., Methods: Retrospective review across 13 institutions identified all occurrences of WEB retreatment within neurovascular databases. Details regarding demographics, aneurysm characteristics, treatment considerations, clinical outcomes, and aneurysm occlusion were obtained and analyzed., Results: Thirty aneurysms were retreated in 30 patients in a cohort of 342 WEB-treated aneurysms. The retreatment rate was 8.8%. Endovascular methods were used for 23 cases, and 7 were treated surgically. Two aneurysms presented with rehemorrhage after initial WEB embolization. Endovascular treatments included stent-assisted coiling (12), flow diversion (7), coiling (2), PulseRider (Johnson & Johnson)-assisted coiling (1), and additional WEB placement (1). Surgical treatments included primary clipping (6) and Hunterian ligation (1). There were no major complications within the study group., Conclusion: WEB retreatments were successfully performed by a variety of techniques, including stent-assisted coiling, clipping, and flow diversion as the most common. These procedures were performed safely with subsequent obliteration of most aneurysms. The potential need for retreatment of aneurysms should be considered during primary WEB treatments., (Copyright © Congress of Neurological Surgeons 2022. All rights reserved.)

Background: The ideal treatment for unruptured vertebral artery dissecting aneurysms (VADAs) and ruptured dominant VADAs remains controversial. We report our experience in the management and endovascular treatment of patients with VADAs., Methods: Patients treated endovascularly for intradural VADAs at a single institution from January 1, 1999, to December 31, 2019, were retrospectively reviewed. Primary neurological outcomes were assessed using modified Rankin Scale (mRS) scores, with mRS >2 considered a poor neurological outcome. Additionally, any worsening (increase) in the mRS score from the preoperative neurological examination was considered a poor outcome., Results: Ninety-one patients of mean (SD) age 53 (11.6) years (48 (53%) men) underwent endovascular treatment for VADAs. Fifty-four patients (59%) presented with ruptured VADAs and 44 VADAs (48%) involved the dominant vertebral artery. Forty-seven patients (51%) were treated with vessel sacrifice of the parent artery, 29 (32%) with flow diversion devices (FDDs), and 15 (17%) with stent-assisted coil embolization (stent/coil). Rates of procedural complications and retreatment were significantly higher with stent/coil treatment (complications 4/15; retreatment 6/15) than with vessel sacrifice (complications 1/47; retreatment 2/47) or FDD (complications 2/29; retreatment 4/29) (p=0.008 and p=0.002, respectively). Of 37 patients with unruptured VADAs treated, only two (5%) had mRS scores >2 on follow-up., Conclusion: Endovascular FDD treatment of VADAs appears to be associated with lower retreatment and complication rates than stenting/coiling, although further study is required for confirmation. Endovascular treatment of unruptured VADAs was safe and was associated with favorable angiographic and neurological outcomes., Competing Interests: Competing interests: AFD is a consultant for Cerenovus, Penumbra, Stryker, Medtronic, and Koswire. FCA is the editor of the Journal of NeuroInterventional Surgery., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Despite advances in endovascular techniques, microsurgery continues to play an important role in the treatment of cerebral aneurysms. This article reviews the history of surgical treatment of intracranial aneurysms and the evolving role of microsurgery in the endovascular era. Although endovascular tools and techniques have changed significantly since the placement of the first Guglielmi coils in 1990, with the development of endoluminal flow-diverting stents and now endosaccular flow-diverting devices, microsurgical treatment of aneurysms has also continued to evolve. Since the first treatment with Hunterian ligation by Horsley in the 1800s, surgical treatment of intracranial aneurysms has advanced significantly beginning with the introduction of the microscope and microsurgical techniques in the 1950s. More recent advances in microsurgical treatment of aneurysms include microsurgical adjuncts, such as indocyanine green angiography, adenosine, and the exoscope, as well as tailored craniotomies, retractorless surgery, and novel bypass constructs for complex aneurysms. Microsurgery continues to play an important role in the endovascular era., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Transradial artery (TRA) access for neuroendovascular procedures is associated with fewer complications than transfemoral artery (TFA) access. This study compares hospital costs associated with TRA access to those associated with TFA access for neurointerventions., Methods: Elective neuroendovascular procedures at a single center were retrospectively analyzed from October 1, 2018 to May 31, 2019. Hospital costs for each procedure were obtained from the hospital financial department. The primary outcome was the difference in the mean hospital costs after propensity adjustment between patients who underwent TRA compared with TFA access., Results: Of the 338 elective procedures included, 63 (19%) were performed through TRA versus 275 (81%) through TFA access. Diagnostic procedures were more common in the TRA cohort (51 of 63, 81%) compared with the TFA cohort (197 of 275, 72%), but the difference was not significant (p=0.48). The TRA cohort had a shorter length of hospital stay (mean (SD) 0.3 (0.5) days) compared with the TFA cohort (mean 0.7 (1.3) days; p=0.02) and lower hospital costs (mean $12 968 ($6518) compared with the TFA cohort (mean $17 150 ($10 946); p=0.004). After propensity adjustment for age, sex, symptoms, angiographic findings, procedure type, sheath size, and catheter size, TRA access was associated with a mean hospital cost of $2514 less than that for TFA access (95% CI -$4931 to -$97; p=0.04)., Conclusion: Neuroendovascular procedures performed through TRA access are associated with lower hospital costs than TFA procedures. The lower cost is likely due to a decreased length of hospital stay for TRA., Competing Interests: Competing interests: AFD is a consultant for Penumbra, Stryker, Medtronic, Cerenovus, and Koswire, and has ownership interest in Aneuvas, Inc., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Transradial artery (TRA) catheterization for neuroendovascular procedures is associated with a lower risk of complications than transfemoral artery (TFA) procedures. However, the majority of literature on TRA access pertains to diagnostic procedures rather than interventional treatments., Objective: To compare TRA and TFA approaches for cerebrovascular interventions., Methods: All patients with an endovascular intervention performed at a single center from October 1, 2018 to December 31, 2019 were retrospectively analyzed. Patients were grouped into 2 cohorts on the basis of whether TRA or TFA access was used. Outcomes included complications, fluoroscopy times, and total contrast administered., Results: A total 579 interventional treatments were performed during the 15-mo study period. TFA procedures (n = 417) were associated with a significantly higher complication rate than TRA (n = 162) procedures (43 cases [10%] vs 5 cases [3%]; P = .008). After excluding patients who underwent thrombectomy and performing a propensity adjustment (including age, sex, pathology, procedure, sheath size, and catheter size), TRA catheterization was associated with decreased odds of a complication (odds ratio, 0.25; 95% CI 0.085-0.72; P = .01), but no significant difference in the amount of contrast administered (6.7-mL increase; 95% CI, -7.2 to 20.6; P = .34) or duration of fluoroscopy (2.1-min increase; 95% CI, -2.5 to 6.7; P = .37) compared with TFA catheterization., Conclusion: Neurointerventional procedures and treatments for a variety of pathologies can be performed successfully using the TRA approach, which is associated with a lower risk of complications and no difference in fluoroscopy duration compared with the TFA approach., (© Congress of Neurological Surgeons 2021.)

Objective: Older patients have a higher risk for poor neurological outcomes following aneurysmal subarachnoid hemorrhage (aSAH). This study compared functional independence in older versus younger patients with aSAH and compared endovascular coiling with microsurgical clipping in the older cohort., Methods: Patients enrolled in the Barrow Ruptured Aneurysm Trial (BRAT) with confirmed aSAH were analyzed. Patients were grouped by age: older (≥65 years old) or younger (<65 years old). The primary outcome analyzed was functional independence at long-term follow-up, defined as Barthel index >80 at 6-year follow-up. A second analysis was performed comparing functional independence in older patients treated with endovascular coiling versus microsurgical clipping., Results: Of 405 patients with aSAH enrolled in BRAT, 77 (19%) were ≥65 years old, and 328 (81%) were <65 years old. A lower percentage of older versus younger patients was functionally independent (Barthel index >80) at 6-year follow-up (42.0% [29/69] vs. 82.2% [217/264]; P < 0.001). A higher percentage of younger patients (69.7% [184/264]) had good neurological outcomes (modified Rankin Scale score <3) at 6-year follow-up compared with older patients (31.9% [22/69]; P < 0.001). A greater percentage of older patients treated with microsurgical clipping (51.0% [18/47]) versus endovascular coiling (22.7% [5/22]) had functional independence at 6-year follow-up (P < 0.04)., Conclusions: Patients ≥65 years old with aSAH are at increased risk for poor neurological outcomes compared with younger patients. Greater independence was observed in older patients after microsurgical clipping than after endovascular coiling at long-term follow-up., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Treatment of small ruptured aneurysms (SRAs) remains controversial, with literature reporting difficulty with endovascular versus microsurgical approaches. This paper analyzes outcomes after endovascular coiling and microsurgical clipping among patients with SRAs prospectively enrolled in the Barrow Ruptured Aneurysm Trial (BRAT)., Method: All BRAT patients were included in this study. Patient demographics, aneurysm size, aneurysm characteristics, procedure-related complications, and outcomes at discharge and at 1-year and 6-year follow-up were evaluated. A modified Rankin scale (mRS) score > 2 was considered a poor outcome., Results: Of 73 patients with SRAs, 40 were initially randomly assigned to endovascular coiling and 33 to microsurgical clipping. The rate of treatment crossover was significantly different between coiling and clipping; 25 patients who were assigned to coiling crossed over to clipping, and no clipping patients crossed over to coiling (P < 0.001). Among SRA patients, 15 underwent coiling and 58 underwent clipping; groups did not differ significantly in demographic characteristics or aneurysm type (P ≥ 0.11). Mean aneurysm diameter was significantly greater in the endovascular group (3.0 ± 0.3 vs 2.6 ± 0.6; P = 0.02). The incidence of procedure-related complications was similar for endovascular and microsurgical treatments (odds ratio [95% confidence interval], 1.0 [0.1-10.0], P = 0.98). Both groups had comparable overall outcome (mRS score > 2) at discharge and 1-year and 6-year follow-up (P = 0.48 and 0.73, respectively)., Conclusions: Most SRA patients in the BRAT underwent surgical clipping, with a high rate of crossover from endovascular approaches. Endovascular treatment was equivalent to surgical clipping with regard to procedure-related complications and neurologic outcomes.

Background: The transradial artery (TRA) approach for neuroendovascular procedures continues to gain popularity, but neurointerventionalists still lag behind interventional cardiologists in the adoption of a TRA-first approach. This study compares the complications and efficiency of the TRA approach to the standard transfemoral artery (TFA) approach at our institution during our initial phase of adopting a TRA-first approach., Methods: A retrospective analysis was performed on all consecutive neuroangiographic procedures performed at a large cerebrovascular center from October 1, 2018 to June 30, 2019. The standard TFA approach was compared with TRA access, with the primary outcome of complications analyzed via a propensity-adjusted analysis., Results: A total of 1050 consecutive procedures were performed on 877 patients during this 9-month period; 206 (20%) procedures were performed via TRA and 844 (80%) via TFA. The overall complication rate was significantly higher with the TFA procedures than with the TRA procedures (7% (60/844) vs 2% (4/206), respectively; p=0.003). A propensity-adjusted analysis showed that the TFA approach was a significant risk factor for a complication (OR 3.6, 95% CI 1.3 to 10.2, p=0.01). However, the propensity analysis showed that fluoroscopy times were on average 4 min less for TFA procedures than for TRA procedures (p=0.003)., Conclusion: The TRA approach for neuroendovascular procedures appears to be safer than the TFA approach. Although a steep learning curve is initially encountered when adopting the TRA approach, the transition to a TRA-first practice can be performed safely for neurointerventional procedures and may reduce complications., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Direct carotid-cavernous sinus fistulas (dCCFs) are high flow arteriovenous shunts between the internal carotid artery and the cavernous sinus. Recently, we have used the pipeline embolization device (PED) to treat dCCFs., Methods: We describe our experience treating patients with dCCFs in whom the PED was placed as the primary treatment modality., Results: Five patients with dCCFs were treated with PEDs deployed in the ipsilateral internal carotid artery spanning the fistula. All patients also underwent either adjunctive transvenous or transarterial embolization. The PED served both as the primary treatment modality and as a scaffold that facilitated safe and efficacious transvenous embolysate administration by altering the flow dynamics through the fistula and providing a physical barrier that protected the internal carotid artery. No intraoperative or perioperative complications occurred. One of the five patients exhibited complete angiographic resolution of the fistula immediately after the procedure. The remaining four patients experienced complete obliteration of the fistula without additional treatment, which suggests that the PED induced alteration promoted thrombosis of the fistula. Therefore, 100% of patients in this series exhibited complete and durable obliteration of the fistula and complete resolution of symptoms following treatment., Conclusions: We believe that use of the PED to treat dCCFs may be a safe and efficacious strategy that facilitates parent vessel protection during transvenous embolization. Furthermore, the flow alterations induced by the PED may promote thrombosis of incompletely occluded fistulas. This is the largest reported series of non-iatrogenic dCCFs treated with use of the PED as the primary initial treatment strategy., Competing Interests: Competing interests: AD: Consulting agreement with Medtronic (pipeline embolization device certification proctor)., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Preoperative embolization of meningiomas to reduce tumor vascularity and intraoperative blood loss remains controversial. Incomplete devascularization on angiography is not significantly correlated with intraoperative estimated blood loss (EBL). Magnetic resonance imaging (MRI) may provide a better assessment of devascularization and prediction of EBL. We retrospectively analyzed patients undergoing preoperative embolization for intracranial meningiomas. Cohorts based on postembolization devascularization (>50% vs. ≤50%) were compared. Of 84 patients with meningioma undergoing preoperative embolization, 35 (42%) had a postembolization MRI before resection and met study inclusion criteria. The mean tumor diameter was 4.9 ± 1.3 cm, and mean intraoperative EBL was 576 ± 341 mL. Compared with MRI, angiography overestimated devascularization in 22 patients (63%). Using pre- versus postembolization MRIs, 17 (49%) patients had a >50% decrease in enhancement, which was associated with lower mean intraoperative blood loss (444 ± 255 mL) compared with 17 patients with ≤50% devascularization (700 ± 374 mL) (P = 0.03). On angiography, the 22 (63%) patients who demonstrated >50% devascularization during embolization did not statistically differ in intraoperative EBL when compared with 13 (37%) patients with <50% angiographic devascularization. Patients with a ≤50% decrease in contrast enhancement on postembolization MRI were 9 times more likely to lose >500 mL blood intraoperatively during resection (95% confidence interval 1.6–54, P = 0.01). Postembolization contrast-enhanced MRI is a better predictor of intraoperative blood loss during meningioma resection than postembolization angiography, which overestimates the degree of embolic devascularization. Postembolization preoperative MRI is warranted for optimal patient management. [ABSTRACT FROM AUTHOR]