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OBJECTIVE: Preoperative embolization of brain arteriovenous malformations (AVMs) is performed to facilitate resection, although its impact on surgical performance has not been clearly defined. The authors tested for associations between embolization and surgical performance metrics. METHODS: The authors analyzed AVM cases resected by one neurosurgeon from 2006 to 2017. They tested whether cases with and without embolization differed from one another with respect to patient and AVM characteristics using t-tests for continuous variables and Fisher’s exact tests for categorical variables. They used simple and multivariable regression models to test whether surgical outcomes (blood loss, resection time, surgical clip usage, and modified Rankin Scale [mRS] score) were associated with embolization. Additional regression analyses integrated the peak arterial afferent contrast normalized for the size of the region of interest (C(max)/ROI) into models as an additional predictor. RESULTS: The authors included 319 patients, of whom 151 (47%) had preoperative embolization. Embolized AVMs tended to be larger (38% with diameter > 3 cm vs 19%, p = 0.001), less likely to have hemorrhaged (48% vs 63%, p = 0.013), or be diffuse (19% vs 29%, p = 0.045). Embolized AVMs were more likely to have both superficial and deep venous drainage and less likely to have exclusively deep drainage (32% vs 17% and 12% vs 23%, respectively; p = 0.002). In multivariable analysis, embolization was not a significant predictor of blood loss or mRS score changes, but did predict longer operating times (+29 minutes, 95% CI 2–56 minutes; p = 0.034) and increased clip usage (OR 2.61, 95% CI 1.45–4.71; p = 0.001). C(max)/ROI was not a significant predictor, although cases with large C(max)/ROI tended to have longer procedure times (+25 minutes per doubling of C(max)/ROI, 95% CI 0–50 minutes; p = 0.051). CONCLUSIONS: In this series, preoperative embolization was associated with longer median resection times and had no association with intraoperative blood loss or mRS score changes.

Object The resection of glomus jugulare tumors can be challenging because of their inherent vascularity. Preoperative embolization has been advocated as a means of reducing operative times, blood loss, and surgical complications. However, the incidence of cranial neuropathy associated with the embolization of these tumors has not been established. The authors of this study describe their experience with cranial neuropathy following transarterial embolization of glomus jugulare tumors using ethylene vinyl alcohol (Onyx, eV3 Inc.). Methods The authors retrospectively reviewed all cases of glomus jugulare tumors that had been treated with preoperative embolization using Onyx at their institution in the period from 2006 to 2012. Patient demographics, clinical presentation, grade and amount of Onyx used, degree of angiographic devascularization, and procedural complications were recorded. Results Over a 6-year period, 11 patients with glomus jugulare tumors underwent preoperative embolization with Onyx. All embolization procedures were completed in one session. The overall mean percent of tumor devascularization was 90.7%. No evidence of nontarget embolization was seen on postembolization angiograms. There were 2 cases (18%) of permanent cranial neuropathy attributed to the embolization procedures (facial nerve paralysis and lower cranial nerve dysfunction). Conclusions Embolizing glomus jugulare tumors with Onyx can produce a dramatic reduction in tumor vascularity. However, the intimate anatomical relationship and overlapping blood supply between these tumors and cranial nerves may contribute to a high incidence of cranial neuropathy following Onyx embolization.

Object As endovascular techniques have become more advanced, preoperative embolization has become an increasingly used intervention in the management of meningiomas. To date, however, no consensus has been reached on the use of this technique. To clarify the role of preoperative embolization in the management of meningiomas, the authors conducted a systematic review of case reports, case series, and prospective studies to increase the current understanding of the management options for these common lesions and complications associated with preoperative embolization. Methods A PubMed search was performed to include all relevant studies in which the management of intracranial meningiomas with preoperative embolization was reported. Immediate complications of embolization were reported as major (sustained) or minor (transient) deficits, death, or no neurological deficits. Results A total of 36 studies comprising 459 patients were included in the review. Among patients receiving preoperative embolization for meningiomas, 4.6% (n = 21) sustained complications as a direct result of embolization. Of the 21 patients with embolization-induced complications, the incidence of major complications was 4.8% (n = 1) and the mortality rate was 9.5% (n = 2). Conclusions Preoperative embolization is associated with an added risk for morbidity and mortality. Preoperative embolization may be associated with significant complications, but careful selection of ideal cases for embolization may help reduce any added morbidity with this procedure. Although not analyzed in the authors' study, embolization may still reduce rates of surgical morbidity and mortality and therefore may still have a potential benefit for selected patients. Future prospective studies involving the use of preoperative embolization in certain cases of meningiomas may further elucidate its potential benefit and risks.

including those related to preoperative embolization, that resulted in an mRS score > 1 at last follow-up. The authors then performed an interesting sensitivity analysis to estimate the true risk of surgery for all AVM grades and not only those selected based on a perceived favorable risk-benefit ratio. The authors included patients who were eligible for surgery but did not undergo resection because of perceived excess surgical morbidity with those who actually underwent resection. Patients were considered eligible for surgery if they were younger than 65 years and did not have significant comorbidities. These added unoperated cases were assumed to have an adverse outcome for the purpose of the sensitivity analysis. For patients with Spetzler-Ponce Class A lesions treated by surgery (n = 190), the risk of a new permanent deficit resulting in an mRS score > 1 or mRS score > 2 was 1.6% and 0.5%, respectively. None of the eligible patients with Spetzler-Ponce Class A lesions were excluded because of perceived excessive surgical risk and thus a sensitivity analysis was not performed. For patients with Spetzler-Ponce Class B lesions treated by surgery (n = 107), the risk of a new permanent deficit resulting in an mRS score> 1 was 14% and mRS score > 2 was 2.8%. Two eligible patients with Spetzler-Ponce Class B lesions were excluded because of perceived excessive surgical risk. The sensitivity analysis showed that if these cases had been included the risk of a new permanent neurological deficit resulting in an mRS score > 1 or mRS score > 2 would have been as high as 15.6% and 4.6%, respectively. For patients with Spetzler-Ponce Class C lesions treated by surgery (n = 44), the risk of a new permanent deficit re sulting in an mRS score > 1 was 38.6% and an mRS score >2 was 15.9%. Twenty-five eligible patients were denied surgery due to perceived excessive surgical morbidity. The sensitivity analysis showed that if these cases had been included the risk of a new permanent neurological deficit resulting in an mRS score > 1 or mRS score > 2 would have been as high as 60.9% and 46.4%, respectively. The authors then superimposed the risk of surgery resulting in an mRS score > 1 upon the Kaplan-Meier curve of the risk of hemorrhage and found that the crossover occurred before 5 months for Spetzler-Ponce Class A lesions and between 8 and 9 years for Spetzler-Ponce Class B lesions but did not occur for Spetzler-Ponce Class C lesions. When surgical outcomes resulting in an mRS score > 2 were superimposed, the crossover occurred before 5 months, between 6 and 8 months, and beyond 8 years for Spetzler-Ponce Class A, B, and C lesions, respectively. The authors concluded that surgery for Spetzler-Ponce

✓ The authors present two cases of giant cerebellar hemispheric arteriovenous malformation (AVM) managed with staged preoperative embolization and surgical resection. A new embolization technique is described, combining injection of estrogen alcohol and polyvinyl acetate into AVM's by superselective catheterization of feeding arteries. Polyvinyl acetate proved to be an ideal liquid embolic material; because it polymerizes quickly and remains in a gelatinous state after injection, there was no difficulty in cutting and retracting the obliterated AVM during surgery. Intraoperative digital subtraction angiography was useful for confirming complete excision of the large and complex AVM.

✓ Two patients with large vascular carotid body tumors underwent preoperative intravascular embolization of the major arterial feeders. The tumor vascularity was reduced markedly, and complete surgical extirpation was accomplished without difficulty. The literature on carotid body tumors is briefly reviewed. The role of preoperative embolization in the treatment of these difficult tumors is emphasized.

✓ Seven cases of giant posterior hemisphere arteriovenous malformations are described. The significance of meningeal feeding vessels from the external carotid artery in addition to the primary cerebral supply through the internal carotid and vertebral arteries to these malformations is discussed. The necessity of bilateral selective external carotid arteriography is stressed, and the value of preoperative embolization is questioned.

✓ Vertebral hemangiomas have usually been treated by resection following preoperative arterial embolization. A case is presented in which no feeding tumor vessels were demonstrable angiographically. The tumor was resected by an arterolateral transthoracic approach without preoperative embolization. There was progressive postoperative improvement of the myelopathy.

✓ Preoperative arterial embolization of a vertebral hemangioma allowed surgical excision of the vertebral body, restoration of normal anatomic continuity of the spinal canal, and improvement in myelopathy.