Extracranial-intracranial Bypass Research Articles

The use and abuse of survival analysis and Kaplan-Meier curves in surgical trials

BackgroundSurvival analysis based on Cox regression and Kaplan-Meier curves, initially devised for oncology trials, have frequently been used in other contexts where fundamental statistical assumptions (such as a constant hazard ratio) are not satisfied. This is almost always the case in trials that compare surgery with medical management. MethodsWe review a trial that compared extracranial-intracranial bypass surgery (EC-IC bypass) with medical management (MM) of patients with symptomatic occlusion of the carotid or middle cerebral artery, where it was claimed that surgery was of no benefit. We discuss a hypothetical study and review other neurovascular trials which have also used survival analysis to compare results. ResultsThe trial comparing EC-IC bypass and MM did not satisfy the fundamental proportional hazard assumption necessary for valid analyses. This was also the case for two prior EC-IC bypass trials, as well as for other landmark neurovascular studies, such as the trials comparing endarterectomy with MM for carotid stenoses, or for the trial that compared intervention and MM for unruptured brain arteriovenous malformations. While minor deviations may have little effect on large trials, it may be impossible to show the benefits of surgery when trial size is small and deviations large. ConclusionSurvival analyses are inappropriate in RCTs comparing surgery with conservative management, unless survival is calculated after the postoperative period. Alternative ways to compare final clinical outcomes, using for example a fixed follow-up period, should be planned for preventive surgical trials that compare intervention with conservative management.

Extracranial-Intracranial Microsurgical Bypass Using a Y-Shaped Vein Graft From the Hand

Extracranial-Intracranial Microsurgical Bypass Using a Y-Shaped Vein Graft From the Hand

Concurrent Moyamoya-like Intracranial Steno-Occlusive Disease and Dural Arteriovenous Fistulas.

The simultaneous presentation of intracranial steno-occlusive disease, Moyamoya disease, or Moyamoya-like vasculopathy and dural arteriovenous fistulas (DAVFs) has been documented in very few case reports worldwide. We aimed to better characterize this association by reviewing the clinical and radiologic findings of 4 patients with concurrent intracranial steno-occlusive disease or Moyamoya-like vasculopathy and DAVFs evaluated in our institution. All 4 patients were of Asian descent. One patient presented with ischemic stroke secondary to intracranial stenosis, 2 presented with symptoms related to the DAVF, and the diagnosis was incidental in the fourth patient. Three patients underwent embolization of the DAVF, which was followed by surgical ligation in 2. One patient underwent extracranial-intracranial bypass for Moyamoya-like intracranial steno-occlusive disease. One patient is being managed conservatively with close follow-up. Our case series details findings in 4 patients with associated intracranial steno-occlusive disease and DAVFs. Further studies and reporting of similar cases are necessary to establish whether this is pure coincidence or if there is indeed a relationship between these 2 conditions, especially in certain ethnic groups.

Extracranial-intracranial (EC-IC) Bypass Versus Medical Therapy Alone in Patients with Symptomatic Artery Occlusion: A Systematic Review and Meta-analysis (P8-5.030)

Extracranial-intracranial (EC-IC) Bypass Versus Medical Therapy Alone in Patients with Symptomatic Artery Occlusion: A Systematic Review and Meta-analysis (P8-5.030)

A technique for reconstruction of a giant extracranial internal carotid artery aneurysm: A technical note.

Surgery is effective for extracranial internal carotid artery (EICA) aneurysms. However, the risk of cranial nerve injury associated with surgical repair, such as graft-assisted resection and extracranial-intracranial bypass techniques, is relatively high. Here, we report two cases of surgical treatment for EICA aneurysms and describe the surgical techniques and strategies to avoid cranial nerve injury. Two patients presented to our facility with an increasing cervical pulsatile mass and no neurological symptoms. Angiography showed a large aneurysm in the cervical internal carotid artery. Surgical treatment was performed to prevent rupture of the aneurysm. In both patients, the aneurysm was strongly attached to the vagus nerve. The aneurysm and vagus nerve were carefully dissected using a low-power bipolar (20 Malis; 3 watts), leaving connective tissue on the vagus nerve side. The aneurysm was detached from the vagus nerve without injury. Based on intraoperative findings, one patient underwent clipping, and the other underwent aneurysmectomy and primary closure for aneurysm obliteration and angioplasty. Both patients were discharged without any cranial nerve dysfunction. The selection of a strategy based on intraoperative findings and low-power bipolar cutting is important for the treatment of extracranial carotid artery aneurysms to preserve cranial nerves.

Angiographic measurement of the superficial temporal artery for potential use in cerebral bypass surgery: a combined radiological and cadaveric study.

This study aims to investigate the microsurgical anatomy of the superficial temporal artery (STA), explore the relationship between STA length and lumen diameter, and develop a reliable radiologic method for selecting STA segments for bypass surgery. This study used 10 cadaveric dissections (20 STAs, both sides) and 20 retrospective radiological examinations (40 STAs, both sides), employing curved multiplanar reformation and flow color lookup table (CLUT) DICOM processing. Measurements included vessel lumen diameters and luminal cross-sectional thicknesses 3mm proximal to the STA bifurcation, 3mm distal to the frontal branch, 5cm distal to the frontal branch, 3mm distal to the parietal branch, and 5cm distal to the parietal branch. The distance between the STA bifurcation and the superior zygomatic border (SZB) was also measured. In our analysis, descriptive statistics encompassed mean, standard deviation (SD), standard error, minimum and maximum values, and distributions. Comparative statistics were performed using Student's t-test, with statistical significance set at p < 0.05. There were no statistically significant differences between STA measurements of bifurcation distances (p = 0.88) and lumen diameters (p = 0.46) between cadavers and radiological measures. However, lumen thicknesses were larger in frontal branches than parietal branches at the seventh and eighth centimeter (p = 0.012, p = 0.039). Branches became thinner distally from the zygoma in both cadavers and radiological image measurements. The CLUT DICOM processing radiological measures provided the high-precision required to enable pre-surgical vessel selection for extracranial-intracranial bypass. The results show that STA vessel luminal diameters are sufficient (> 1mm) for bypass surgery in the first 9cm but gradually decrease after that. Also shown is that the choice of frontal versus parietal branches depends on individual anatomical features; therefore, careful preoperative radiological examination is critical.

Surgical and endovascular cerebral revascularization for cerebral vasculitis with inflammatory vessel stenosis: a case series

Autoimmune vasculitides affect the cerebral vasculature significantly in a considerable number of cases. When immunosuppressive treatments fail to prevent stenosis in cerebral vessels, treatment options for affected patients become limited. In this case series, we present four cases of pharmacoresistant vasculitis with recurrent transient ischemic attacks (TIAs) or stroke successfully treated with either extracranial-intracranial (EC-IC) bypass surgery or endovascular stenting. Both rescue treatments were effective and safe in the selected cases. Our experience suggests that cases of pharmacoresistant cerebral vasculitis with recurrent stroke may benefit from rescue revascularization in combination with maximum medical management.

Abstract TMP71: The Association Between Improvement of Headache and Cerebrovascular Reactivity After Revascularization Surgery in Moyamoya Arteriopathy

Background and aim: Significant headache is often reported by patients with moyamoya arteriopathy (MMA) but has a poorly understood pathophysiology. To decide on management, physicians often focus on stroke-like symptoms while the impact on quality of life and economic burden of chronic headache is often overlooked. We aimed to investigate the effect of revascularization surgery on headache in MMA and potential association with cerebrovascular reactivity (CVR). Methods: This was a single-center retrospective study in adult patients with MMA, who underwent extracranial-intracranial (EC-IC) bypass surgery between Jan 2010 - Sept 2022 and had CVR-MRI performed. Clinical and imaging data were collected through systematic chart review complemented by structured headache questionnaires. We assessed the association between headache and CVR before and after revascularization surgery along with potential predictors using logistic regression analysis. Results: Fifty-nine patients were included (mean age 44±13 years, 42 women (71%)). Thirty-seven patients (63%) had bilateral MMA of whom 19 (51%) had bilateral EC-IC bypass surgery. Thirty-eight patients (64%) reported headache pre-surgery with mostly migraine-like features. More than a third of patients (37%) lost workdays or quit their job because of headache. Headache improved in 26/38 (68%) patients post-surgery with a reduction in pain severity (median VAS 6 to 3; p = 0.005) and sick leave (37% to 8%; p&lt;0.001). CVR improved in 33/43 (77%) patients who had pre- and post-surgery CVR-MRI, which was associated with headache improvement (OR:14; 95% CI:1.4-131). Pre-operative headache severity (VAS-score) was an independent predictor for headache improvement post-surgery (OR:1.7; 95% CI:1.2-2.5). Conclusions: Results of this study showed improvement of headache in most patients with MMA after revascularization surgery and association with improvement in CVR, supporting the hypothesis of a vascular origin. Future larger cohort studies should confirm this hypothesis, improve understanding of underlying pathophysiology and identify potential future treatment targets to guide management for this underappreciated yet disabling aspect of MMA.

Abstract WP127: Diagnostic Value of the Ivy Sign Compared to MR With Cerebrovascular Reactivity in Decompensated Moyamoya Arteriopathy

Introduction: MR cerebrovascular reactivity (CVR) mapping during rapid manipulation of end-tidal pCO2 is used to assess hemodynamic compromise in patients with Moyamoya arteriopathy (MMA). Leptomeningeal ivy sign on MRI FLAIR sequence may indicate regions of decreased perfusion, which would be an inexpensive and easy way to screen for hemodynamic compromise. The purpose of this study was to examine the diagnostic value of the ivy sign compared to MR CVR. Methods: For this retrospective cross-sectional study, we included consecutive patients with uncompensated MMA who were eligible for extracranial-intracranial bypass surgery and completed a preoperative MRI FLAIR with CVR study. Patients with incomplete or artefact degraded imaging were excluded. Two neuroradiologists who were blinded for the CVR result independently assessed the degree of ivy sign on axial 2D FLAIR imaging as grade 0, 1 or 2 in 8 predefined brain regions. Two different readers, blinded for ivy sign, independently assessed the presence or absence of steal in the same regions on MR CVR. Consensus was reached for discordant findings. We assessed interrater agreement using weighted kappa followed by diagnostic accuracy measures for the ivy sign using MR CVR as a reference. Results: We enrolled 73 patients (41/73 (56.1%) female; mean age 43). 47/73 (64%) patients had bilateral MMA with on average 3 brain regions with abnormal CVR. Interrater agreement was good for ivy sign (weighted kappa 0.63 (95%CI 0.54-0.71)) and excellent for CVR (kappa 0.95 (95% CI 0.87-1.00)). For a total of 156/584 (26.7%) brain regions, there was agreement between a positive ivy sign and the presence of steal on CVR and 240/584 (41%) brain regions had no ivy sign and normal CVR. The sensitivity of the ivy sign was 64.5%, specificity 70.2%, positive predictive value 60.5% and negative predictive value 73.6% with an AUC of 0.68 (95% CI 0.64-0.72) Conclusions: In this preselected cohort with high pretest probability for hemodynamic compromise, the diagnostic accuracy of the ivy sign compared to MR CVR was limited and needs to be used with caution to determine haemodynamic status in MMA.

Spontaneous development and involution of a de novo pseudoaneurysm at the superficial temporal artery-middle cerebral artery bypass anastomotic site in a patient with moyamoya disease: illustrative case.

De novo pseudoaneurysm formation is a rare complication of extracranial-intracranial bypass surgery. The authors report the case of a 28-year-old male who presented with new-onset right temporal and occipital ischemia who was found to have bilateral proximal internal carotid artery occlusion with collateral vasculature formation consistent with moyamoya disease. The patient underwent bilateral superficial temporal artery-middle cerebral artery bypasses. A de novo pseudoaneurysm was found at the left-sided bypass distal anastomotic site recipient vessel 1 month after the surgery. The pseudoaneurysm demonstrated a progressive reduction in size and eventual complete involution at 6 months after surgery. Limited literature reports extracranial-intracranial bypass-associated aneurysms treated primarily with either clipping or resection and reanastomosis. The authors demonstrate, for the first time, a progressively benign natural history course of an extracranial-intracranial bypass distal anastomotic site pseudoaneurysm.

Extracranial-Intracranial Bypass with Plastic Surgery Using a Y-Shaped Vein Graft from the Hand – a Case Series and Guide to Collaboration

Extracranial-Intracranial Bypass with Plastic Surgery Using a Y-Shaped Vein Graft from the Hand – a Case Series and Guide to Collaboration

Extracranial-Intracranial Bypass for Moyamoya Disease: The Influence of Racial and Socioeconomic Disparities on Outcomes – A National Inpatient Sample Analysis

IntroductionExtracranial-intracranial (EC-IC) bypass is an established therapeutic option for Moyamoya Disease (MMD). However, little is known about the effects of racial and ethnic disparities on outcomes. This study assessed trends in EC-IC bypass outcomes among MMD patients stratified by race and ethnicity. MethodsUtilizing the US National Inpatient Sample, we identified MMD patients undergoing EC-IC bypass between 2002 and 2020. Demographic and hospital-level data were collected. Multivariable analysis was conducted to identify independent factors associated with outcomes. Trend analysis was performed using piecewise joinpoint regression. ResultsOut of 14,062 patients with MMD, 1,771 underwent EC-IC bypass. Of these, 60.59% were White, 17.56% were Black, 12.36% were Asians, 8.47% were Hispanic, and 1.02% were Native Americans. Discharge to non-home was noted in 21.7% of cases, with a 6.7% death and 3.8% postoperative neurologic complications rates. EC-IC bypass was more commonly performed in Native Americans (23.38%) and Asians (17.76%). Hispanics had the longest mean length of stay (8.4 days) and lower odds of non-home discharge compared to Whites (OR: 0.64; 95% CI 0.40-1.03; p=0.04). Patients with Medicaid, private insurance, self-payers, and insurance paid by other governments had lower odds of non-home discharge than those with Medicare. ConclusionThis study highlights racial and socioeconomic disparities in EC-IC bypass for patients with MMD. Despite these disparities, we did not find any significant difference in the quality of care. Addressing these disparities is essential for optimizing MMD outcomes.

Application of hybrid operating room in the surgical treatment for intracranial aneurysm

BackgroundIntracranial aneurysms are associated with a high mortality rate in the event of a rupture and significant morbidity during subsequent treatment. Hybrid treatment approaches for vascular diseases have been incorporated into modern operating rooms as guides for surgical interventions now. The current study evaluates the feasibility and effectiveness of hybrid operating room system and its application in the surgical treatment of intracranial aneurysms. AimsTo evaluate the feasibility and effectiveness of hybrid operating room system and its application in the surgical treatment for aneurysms. Methods76 patients with 84 intracranial aneurysms were surgically treated in Hybrid operating room with intraoperative angiography between March 2018 and March 2021. Aneurysm clipping was performed in 76 (94.7 %) cases; Aneurysm trapping with extracranial-intracranial (EC-IC) bypass in 4 (5.3 %) cases. Patient demographics, aneurysm size, location, Hunt and Hess score, were recorded. 69 (90.8 %) patients were followed up 6–12 months post operation. ResultsIntraoperative angiography demonstrated 5 (6.9%) unexpected aneurysm neck residuals leading to adjustment; 6 (8.3%) parent vessel stenosis in which 5 returned to normal after adjustment. Four giant paraclinoid aneurysms trapping with EC-IC bypass showed total successful vessel reconstruction and complete aneurysm exclusion (100%). The postoperative outcome was evaluated with the modified Rankin Scale (mRS). 53 (76.8%) patients showed good outcome (mRS 0), 11 (15.9%) showed mild neurological defect (mRS 1–2), 3 (4.3%) showed poor outcome (mRS 5), and 2 (2.9%) patients died (mRS 6, Hunt-Hess grade V before surgery). Conclusion: Hybrid operating room provides new concepts in the surgically treatment of intracranial aneurysms, especially valuable for the complex aneurysms. The combination of intraoperative imaging of angiography and clipping surgery may offer the opportunity of radical clipping and reduced complications for aneurysm patients.

Commentary: In Response to Extracranial-Intracranial Bypass in Symptomatic Arterial Occlusion Trial (CMOSS).

Commentary: In Response to Extracranial-Intracranial Bypass in Symptomatic Arterial Occlusion Trial (CMOSS).

Sonolucent Cranial Implants: A Window into the Future of Management of Neurosurgical Patients? A Systematic Review and Cost Analysis

Background and ObjectivesComputerized tomography (CT) is a cornerstone of the identification and management of acute changes in neurosurgery patients. In addition to the monetary expense of CT scans, further costs are incurred due to the time of patient transport and radiation exposure. Ultrasounds (US) offer a safe, inexpensive, and bedside alternative to CT but obstacles remain due to decreased penetrance in the adult skull. Sonolucent Cranial Implants (SCI) offer a window for ultrasounds to view intracranial architectures. MethodsThe authors performed a PRISMA guidelines-based systematic review of the literature. Information was extracted from included articles in regards to illness pathology, ultrasound imaging feasibility, comparison to standard imaging, infections, and revisions. Costs were collected in regards to price of implant and follow-up imaging. Results226 articles resulted of which 5 were included in the study. Ninety non-duplicate patients who received SCIs were analyzed. The pathologies of included patients is as follows: 51 patients were after extracranial-intracranial bypass, 37 after VP shunt placement for hydrocephalus, one after tumor resection, and one after cranioplasty following decompressive hemicraniectomy. All studies noted feasibility of ultrasound and comparability to standard imaging following SCI placement. Follow up imaging with trans-sonolucent cranial implant ultrasound was estimated to save up to $4,000 per patient depending on the procedure. ConclusionInitial studies suggest that ultrasound imaging through SCIs is a safe and efficacious alternative to CT imaging in neurosurgical patients. Cost analysis suggests that SCI and subsequent US can offer a cost savings compared to current treatment.

Proximal Internal Carotid Artery Occlusion and Extracranial-Intracranial Bypass for Treatment of Fusiform and Giant Internal Carotid Artery Aneurysms

To discuss the treatment of intracranial fusiform and giant internal carotid artery (ICA) aneurysms via revascularization based on our institutional experience. An institutional review board-approved retrospective analysis was performed of patients with unruptured fusiform and giant intracranial ICA aneurysms treated from November 1991 to May 2020. All patients were evaluated for extracranial-intracranial (EC-IC) bypass and ICA occlusion. Thirty-eight patients were identified. Initially, patients failing preoperative balloon test occlusion were treated with superficial temporal artery (STA)-middle cerebral artery (MCA) bypass and concurrent proximal ICA ligation. We then treated them with STA-MCA bypass, followed by staged balloon test occlusion, and, if they passed, endovascular ICA coil occlusion. We treat all surgical medically uncomplicated patients with double-barrel STA-MCA bypass and concurrent proximal ICA ligation. The mean length of follow-up was 99 months. Symptom stability or improvement was noted in 85% of patients. Bypass graft patency was 92.1%, and all surviving patients had patent bypasses at their last angiogram. Aneurysm occlusion was complete in 90.9% of patients completing proximal ICA ligation. Three patients experienced ischemic complications and 4 patients experienced hemorrhagic complications. Not all fusiform intracranial ICA aneurysms require intervention, except when life-threatening rupture risk is high or symptomatic management is necessary to preserve function and quality of life. EC-IC bypass can augment the safety of proximal ICA occlusion. The rate of complete aneurysm occlusion with this treatment is 90.9%, and long-term bypass graft-related complications are rare. Perioperative stroke is a major risk, and continued evolution of treatment is required.

Double-barrel STA-MCA bypass for a giant thrombosed supraclinoid ICA aneurysm with gangliocapsular infarct – A case report

Extracranial-intracranial (EC-IC) bypass is an essential tool for cerebral revascularization procedure. Superficial temporal artery–middle cerebral artery (STA-MCA) bypass was usually performed using one stem of the STA only. In an attempt to augment the flow and to direct the flow to different ischemic areas of the brain, a “double-barrel” technique is used, in which both branches of the STA are used to revascularize distinct MCA territories. Though there are many advancements in endovascular procedures, still STA MCA bypass plays a role in selected cases. We report a 50 years old female with giant thrombosed supraclinoid segment internal carotid artery (ICA) aneurysm with gangliocapsular infarct presented with vision loss, and limb weakness. Patient underwent double barrel STA-MCA bypass, post operatively patient improved of symptoms and patient was discharged in a stable condition. Though endovascular techniques have evolved exponentially over the last few years, and most of these complex aneurysms can be treated using flow-diverting techniques.Though the need for microsurgical intervention is diminished iin this endovascular era, still the surgeons should think about these revascularization procedures as it gives life-long durable solution.

Extracranial-Intracranial Bypass and Risk of Stroke and Death in Patients With Symptomatic Artery Occlusion

Prior trials of extracranial-intracranial (EC-IC) bypass surgery showed no benefit for stroke prevention in patients with atherosclerotic occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA), but there have been subsequent improvements in surgical techniques and patient selection. To evaluate EC-IC bypass surgery in symptomatic patients with atherosclerotic occlusion of the ICA or MCA, using refined patient and operator selection. This was a randomized, open-label, outcome assessor-blinded trial conducted at 13 centers in China. A total of 324 patients with ICA or MCA occlusion with transient ischemic attack or nondisabling ischemic stroke attributed to hemodynamic insufficiency based on computed tomography perfusion imaging were recruited between June 2013 and March 2018 (final follow-up: March 18, 2020). EC-IC bypass surgery plus medical therapy (surgical group; n = 161) or medical therapy alone (medical group; n = 163). Medical therapy included antiplatelet therapy and stroke risk factor control. The primary outcome was a composite of stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years after randomization. There were 9 secondary outcomes, including any stroke or death within 2 years and fatal stroke within 2 years. Among 330 patients who were enrolled, 324 patients were confirmed eligible (median age, 52.7 years; 257 men [79.3%]) and 309 (95.4%) completed the trial. For the surgical group vs medical group, no significant difference was found for the composite primary outcome (8.6% [13/151] vs 12.3% [19/155]; incidence difference, -3.6% [95% CI, -10.1% to 2.9%]; hazard ratio [HR], 0.71 [95% CI, 0.33-1.54]; P = .39). The 30-day risk of stroke or death was 6.2% (10/161) in the surgical group and 1.8% (3/163) in the medical group, and the risk of ipsilateral ischemic stroke beyond 30 days through 2 years was 2.0% (3/151) and 10.3% (16/155), respectively. Of the 9 prespecified secondary end points, none showed a significant difference including any stroke or death within 2 years (9.9% [15/152] vs 15.3% [24/157]; incidence difference, -5.4% [95% CI, -12.5% to 1.7%]; HR, 0.69 [95% CI, 0.34-1.39]; P = .30) and fatal stroke within 2 years (2.0% [3/150] vs 0% [0/153]; incidence difference, 1.9% [95% CI, -0.2% to 4.0%]; P = .08). Among patients with symptomatic ICA or MCA occlusion and hemodynamic insufficiency, the addition of bypass surgery to medical therapy did not significantly change the risk of the composite outcome of stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years. ClinicalTrials.gov Identifier: NCT01758614.

Extracranial-Intracranial Bypass Surgery for Stroke Prevention

Extracranial-Intracranial Bypass Surgery for Stroke Prevention

Dolenc approach for clipping of giant C6 and C7 segment aneurysms of the internal carotid artery.

Surgical treatment for giant aneurysms of the ICA-ophthalmic segment (C6) and communicating artery segment (C7) is a challenge for neurosurgeons because of their high risks and poor outcomes. We aim to explore the advantages and disadvantages of the Dolenc approach in the treatment of giant C6-C7 segment aneurysms. We retrospectively reviewed the clinical data of 13 cases with giant C6 aneurysms and 4 cases with giant C7 aneurysms treated with the Dolenc approach. All 17 cases of aneurysms were clipped successfully using the Dolenc approach, of which, 1 case with ipsilateral MCA occlusion underwent extracranial-intracranial artery bypass after the aneurysm clipping. Regarding clinical outcomes, six out of nine cases with preoperative visual impairment improved after surgery, two cases saw no change, and one case deteriorated. Of all the cases, one had new-onset vision loss, four had new-onset oculomotor paralysis, three had surgical side cerebral infarction, and two had diabetes insipidus. DSA or CTA examination within 2 weeks after surgery showed that all aneurysms were completely clipped without residual. After a follow-up of 9-12 months, 17 patients were evaluated based on GOS and CTA examination. A total of 14 cases had GOS 5 scores, 2 cases had GOS 4 scores, 1 case had GOS 2 scores, and no cases had death. None of the patients had recurrence based on CTA examinations. Through the Dolenc approach, we could achieve more operation space and expose clinoid segments for temporary occlusion. Therefore, the Dolenc approach was shown to be a safe, effective, and feasible treatment for giant C6-C7 aneurysms.