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Tarek Rayan and Sepideh Amin-Hanjani

With large or giant aneurysms, the use of multiple tandem clips can be essential for complete obliteration of the aneurysm. One potential disadvantage, however, is the considerable cumulative weight of these clips, which may lead to kinking of the underlying parent vessels and obstruction of flow. The authors describe a simple technique to address this problem, guided by intraoperative blood flow measurements, in a patient with a ruptured near-giant 2.2 × 1.7–cm middle cerebral artery bifurcation aneurysm that was treated with the tandem clipping technique. A total of 11 clips were applied in a vertical stacked fashion. The cumulative weight of the clips caused kinking of the temporal M2 branch of the bifurcation with reduction of flow. A 4-0 Nurolon suture tie was applied to the hub of one of the clips and was tethered to the dura of the sphenoid ridge by a small mini-clip and reinforced by application of tissue sealant. The patient underwent intraoperative indocyanine green videoangiography as well as catheter angiography, which demonstrated complete aneurysmal obliteration and preservation of vessel branches. Postoperative angiography confirmed patency of the bifurcation vessels with mild vasospasm. The patient had a full recovery with no postoperative complications and was neurologically intact at her 6-month follow-up. The suture retraction technique allows a simple solution to parent vessel obstruction following aneurysm tandem clipping, in conjunction with the essential guidance provided by intraoperative flow measurements.

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E. Sander Connolly Jr.

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L. Fernando Gonzalez, Sepideh Amin-Hanjani, Nicholas C. Bambakidis and Robert F. Spetzler

Posterior circulation lesions constitute approximately 10% of all intracranial aneurysms. Their distribution includes the basilar artery (BA) bifurcation, superior cerebellar artery, posterior inferior cerebellar artery, and anterior inferior cerebellar artery. The specific features of a patient's aneurysm and superb anatomical knowledge help the surgeon to choose the most appropriate approach and to tailor it to the patient's situation. The main principle that must be applied is maximization of bone resection. This allows the surgeon to work within a wider corridor, which facilitates the use of surgical instruments and minimizes retraction of the brain.

The management of aneurysms within the posterior circulation requires expertise in skull base and vascular surgery. Endovascular treatments have become increasingly important, but in this paper the authors focus on the surgical management of these difficult aneurysms. The paper is divided into three parts: the first section is a brief review of the anatomy of the BA; the second part is a review of the techniques associated with the management of posterior fossa aneurysms; and in the third section the authors describe the different approaches, their nuances and indications based on the location of the aneurysm, and its relationship to the surrounding bone (especially the clivus, dorsum sellae, and the free edge of the petrous apex).

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Christopher J. Stapleton, Gursant S. Atwal, Ahmed E. Hussein, Sepideh Amin-Hanjani and Fady T. Charbel

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.

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William W. Ashley Jr., Sepideh Amin-Hanjani, Ali Alaraj, John H. Shin and Fady T. Charbel

✓Extracranial–intracranial bypass surgery has advanced from a mere technical feat to a procedure requiring careful patient selection and a justifiable decision-making paradigm. Currently available technologies for flow measurement in the perioperative and intraoperative setting allow a more structured and analytical approach to decision making. The purpose of this report is to review the use of flow measurement in cerebral revascularization, presenting algorithms for flow-assisted surgical planning, technique, and surveillance.

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Ali Alaraj, William W. Ashley Jr., Fady T. Charbel and Sepideh Amin-Hanjani

Object

The superficial temporal artery (STA) is the mainstay of donor vessels for extracranial–intracranial bypass in cerebral revascularization. However, the typically used STA anterior or posterior branch is not always adequate in its flow-carrying capacity. In this report the authors describe the use of the STA trunk at the level of the zygoma as an alternative donor and highlight the benefits and pitfalls of this revascularization option.

Methods

The authors reviewed the cases of 4 patients in whom the STA trunk was used as a donor site for anastomosis of a short interposition vein graft. The graft was implanted into the middle cerebral artery to trap a cartoid aneurysm in 2 patients, and the posterior cerebral artery for vertebrobasilar insufficiency in the other 2. Discrepancies in size between the interposition vein and STA trunk were compensated for by a beveled end-to-end anastomosis or by implanting the STA trunk into the vein graft in an end-to-side fashion.

Results

Intraoperative flow measurements confirmed the significantly higher flow-carrying capacity of the STA trunk (54–100 ml/minute) compared with its branches (10–28 ml/minute). The STA trunk interposition graft has several advantages compared with an interposition graft to the cervical carotid, including a shorter graft and no need for a neck incision. However, in the setting of ruptured aneurysm trapping, with the risk of subsequent vasospasm, it is a poor conduit for endovascular therapies.

Conclusions

The STA trunk is a valuable donor option for cerebral revascularization, but should be avoided in the setting of subarachnoid hemorrhage.

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Sepideh Amin-Hanjani, John H. Shin, Meide Zhao, Xinjian Du and Fady T. Charbel

Object

To date, angiography has been the primary modality for assessing graft patency following extracranial–intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography.

Methods

One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery).

There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean ± standard error of the mean, 37 ± 13 ml/minute compared with 105 ± 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02).

Conclusions

Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.

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Fady T. Charbel, Meide Zhao, Sepideh Amin-Hanjani, William Hoffman, Xinjian Du and Marlyn E. Clark

Object. Balloon occlusion tests (BOTs) are performed to identify patients who are at risk for ischemia and stroke following permanent internal carotid artery (ICA) occlusion. The object of this work was to determine whether patient-specific blood flow modeling can be used to identify patients in whom the BOT would not be tolerated.

Methods. The test was performed in 16 patients who underwent BOT with continuous neurological and electroencephalographic monitoring, followed by a hypotensive challenge. During hypotension a tracer was injected so that single-photon emission tomography (SPECT) scans could be obtained. Each individual brain circulation was modeled using information gained from phase-contrast magnetic resonance (MR) angiography and digital subtraction (DS) angiography, and the predicted effect of the BOT was evaluated.

Six patients did not tolerate the BOT; in these patients, decreases in middle cerebral artery (M1 segment) blood flow of 41 ± 27% (mean ± standard deviation), anterior cerebral artery (A3 segment) flow of 56 ± 33%, and posterior cerebral artery (P2 segment) flow of 4 ± 13% ipsilateral to the site of occlusion were found with modeling; these changes were significantly greater than the percentage of changes measured in the contralateral hemisphere (p < 0.05). Ten patients who tolerated the BOT well had calculated decreases in ipsilateral flows of only 9 ± 6% for the M1 segment, 12 ± 40% for the A3 segment, and 17 ± 21% for the P2 segment during BOT modeling.

Conclusions. A decrease in blood flow in both the ipsilateral M1 and A3 segments that was greater than 20%, calculated by flow modeling of the BOT, was 100% sensitive and 100% specific in identifying patients who could not tolerate the BOT. Blood flow modeling, coupled with DS angiography and noninvasive phase-contrast MR angiography measurements to make calculations patient specific, can be used to identify patients who have an elevated risk of ischemia during the BOT.

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Omar M. Qahwash, Ali Alaraj, Victor Aletich, Fady T. Charbel and Sepideh Amin-Hanjani

Object

The goal of this study was to demonstrate feasibility and evaluate technical aspects of early endovascular access through extracranial-intracranial (EC-IC) bypass grafts.

Methods

Patients undergoing endovascular interventions through the graft in the acute postoperative period following EC-IC bypass are presented. Results, complications, and technical nuances are reviewed.

Results

Fourteen endovascular procedures were performed in 5 patients after EC-IC bypass for ruptured aneurysms in 4 patients and posterior circulation ischemia in 1 patient. In 2 patients, a saphenous vein graft (SVG) was used to bypass the common carotid artery (CCA) to the middle cerebral artery (MCA). One patient underwent a superficial temporal artery (STA)–MCA bypass, and in 2 other patients the STA stump was connected to the intracranial circulation via an interposition SVG. The interval from surgery to endovascular intervention spanned 2–18 days; the indication was intracranial vasospasm in all patients. One case involved angioplasty of the proximal anastomosis on postoperative Day 14. All other interventions entailed proximal access through the bypass conduit for intraarterial infusion of vasodilators. Significant vasospasm of the STA itself was encountered in 2 patients during endovascular manipulation, and it was treated with intraarterial nitroglycerin. There were no cases of anastomotic disruption.

Conclusions

Endovascular catheterization and intervention involving a recent EC-IC bypass is feasible. The main limitation in this series was catheter-induced vasospasm involving the STA. A vein graft may be the more appropriate option in patients with subarachnoid hemorrhage who may require subsequent endovascular intervention for vasospasm.

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Troy A. Munson, Tibor Valyi-Nagy, Manuel Utset, Zachary Lewis and Sepideh Amin-Hanjani

Hemangioendotheliomas have only rarely been encountered in the neuraxis. Here, the authors present a case of an intramedullary hobnail hemangioendothelioma of the spinal cord, the first case described of this particular pathological entity in the neuraxis. The authors discuss their treatment and review the pertinent literature regarding management.