Venous and arterial bypass grafts for difficult tumors, aneurysms, and occlusive vascular lesions: evolution of surgical treatment and improved graft results

A novel, reusable, realistic neurosurgical training simulator for cerebrovascular bypass surgery: Iatrotek® bypass simulator validation study and literature review

Background

Microanastomosis is a challenging technique requiring continuous training to be mastered. Several models have been proposed, but few effectively reflect a real bypass surgery; even fewer are reusable, most are not easily accessible, and the setting is often quite long. We aim to validate a simplified, ready-to-use, reusable, ergonomic bypass simulator.

Methods

Twelve novice and two expert neurosurgeons completed eight End-to-End (EE), eight End-to-Side (ES), and eight Side-to-Side (SS) microanastomoses using 2-mm synthetic vessels. Data on time to perform bypass (TPB), number of sutures and time required to stop potential leaks were collected. After the last training, participants completed a Likert Like Survey for bypass simulator evaluation. Each participant was assessed using the Northwestern Objective Microanastomosis Assessment Tool (NOMAT).

Results

When comparing the first and last attempts, an improvement of the mean TPB was registered in both groups for the three types of microanastomosis. The improvement was always statistically significant in the novice group, while in the expert group, it was only significant for ES bypass. The NOMAT score improved in both groups, displaying statistical significance in the novices for EE bypass. The mean number of leakages, and the relative time for their resolution, also tended to progressively reduce in both groups by increasing the attempts. The Likert score expressed by the experts was slightly higher (25 vs. 24.58 by the novices).

Conclusions

Our proposed bypass training model may represent a simplified, ready-to-use, reusable, ergonomic, and efficient system to improve eye-hand coordination and dexterity in performing microanastomoses.

Spotlight on clinical strategies of Chronic Internal Carotid Artery Occlusion: Endovascular interventions and external-intracarotid bypasses compared to conservative treatment

Chronic internal carotid artery occlusion (CICAO) has high prevalence and incidence rates, and patients with CICAO can be completely asymptomatic, experience a devastating stroke or die. It is important to note that CICAO causes cerebrovascular accidents. Currently, the external carotid-internal carotid (EC-IC) bypass technique is used to treat CICAO. However, many clinical studies showed that EC-IC bypass was not beneficial for many patients with CICAO. Meanwhile, endovascular intervention treatment options for CICAO are evolving, and an increasing number of patients are undergoing endovascular intervention therapy. Accordingly, a review comparing both techniques is warranted. For this review, we searched PubMed and collected relevant case study reports comparing endovascular interventional therapy and internal and external cervical bypass surgeries to provide strategies for clinical treatment.

Safety and effectiveness of high flow extracranial to intracranial saphenous vein bypass grafting in the treatment of complex intracranial aneurysms: a single-centre long-term retrospective study

Background

To summarize the safety and effectiveness of high flow extracranial to intracranial saphenous vein bypass grafting in the treatment of complex intracranial aneurysms.

Methods

The data of complex intracranial aneurysms patients for high flow extracranial to intracranial saphenous vein bypass grafting from January 2008 to January 2020 were retrospectively collected and analyzed. Eighty-two patients (31 men and 51 women) with 89 aneurysms underwent 82 saphenous vein bypass grafts followed by immediate parent vessel occlusion. The aneurysm was located at the internal carotid artery, middle cerebral artery, and basilar artery in 75, 11, and 3 cases, respectively.

Results

The patency rate of bypass grafting was 100, 100, 96.3 and 92.4% on intraoperation, on the first postoperative day, at discharge and 6 months follow-up, respectively. At discharge and 6 months follow-up, 3 and 6 patients had graft occlusions. The main postoperative complications were transient hemiparesis and hemianopsia. 3 patients died due to bypass complications and poor physical condition.

Conclusions

High flow extracranial to intracranial saphenous vein bypass grafting is safe and effective in the treatment of complex intracranial aneurysms and the saphenous vein can meet the requirements of brain blood supply. A high rate of graft patency and adequate cerebral blood flow can be achieved.

Highlights

A single-centre long-term retrospective study was conducted to assess the safety and effectiveness of high flow EC-IC saphenous vein bypass grafting in the treatment of complex intracranial aneurysms. The data of 82 patients from January 2008 to January 2020 were retrospectively collected and analysed.

We found the patency rate of bypass grafting was 100, 100, 96.3 and 92.4% on intraoperation, on the first postoperative day, at discharge and 6 months follow-up, respectively. At discharge and 6 months follow-up, 3 and 6 patients had graft occlusions.

Finally, we conclude that high flow extracranial to intracranial saphenous vein bypass grafting is safe and effective in the treatment of complex intracranial aneurysms and the selected blood supply vessels can meet the requirements of blood supply.

As far as we know, this study is one of the maximum number of cases in the treatment of complex intracranial aneurysms with saphenous vein bypass.

Does Universal Bypass before Carotid Artery Occlusion Obviate the Need for Balloon Test Occlusion: Personal Experience with Extracranial-Intracranial Bypass in 23 Patients

Aim

Carotid artery ligation carries a potential risk of ischemic complications even in patients with good collaterals and adequate cross-circulation. Preoperative assessment through balloon test occlusion (BTO) is technically challenging and not feasible in all patients. We analyze our experience with universal bypass without performing detailed cerebrovascular reserve (CVR) studies in 23 patients before carotid artery ligation.

Patients and Methods

This was a retrospective analysis of the case records of 23 patients who underwent cervical carotid artery ligation for various indications since January 2009.

Results

The study included 21 patients with cavernous carotid aneurysms, one patient with a large fusiform petrous carotid aneurysm, and one patient with recurrent glomus jugulare encasing the cervical internal carotid artery. The initial 12 patients underwent preoperative BTO with hypotensive challenge. All patients underwent a bypass procedure followed by carotid artery ligation irrespective of the BTO findings. Patients who successfully completed a BTO underwent a low-flow superficial temporal artery to middle cerebral artery bypass. A high-flow extracranial-intracranial bypass using a saphenous vein graft from external carotid artery to middle cerebral artery was done in all patients who either failed the BTO or did not undergo BTO. We had two operative mortalities and one poor outcome. All the other patients had a good recovery with a Glasgow outcome score of 5 at the last follow-up. Graft patency rates were 81.1% in both the low-flow and high-flow groups.

Conclusion

Universal high-flow bypass is safe, effective, and should be preferred in all patients before carotid artery ligation. It obviates the need for detailed CVR assessment, especially in centers with limited resources.

Orthopaedic tumors: What problems are we solving, and are universities and major medical centers doing enough?

Little has been published about the complexity of orthopaedic tumors compared to others tumors. The current study in the literature treated this problem in terms of classification, surgical intervention and impact on the patient. In this article, factors risks of tumors will be we identified. A strategy based on three dimensional simulations will be explained in order to improve the clinical trials.

Low-flow and high-flow neurosurgical bypass and anastomosis training models using human and bovine placental vessels: a histological analysis and validation study

OBJECTIVE

Microvascular anastomosis is a basic neurosurgical technique that should be mastered in the laboratory. Human and bovine placentas have been proposed as convenient surgical practice models; however, the histologic characteristics of these tissues have not been compared with human cerebral vessels, and the models have not been validated as simulation training models. In this study, the authors assessed the construct, face, and content validities of microvascular bypass simulation models that used human and bovine placental vessels.

METHODS

The characteristics of vessel segments from 30 human and 10 bovine placentas were assessed anatomically and histologically. Microvascular bypasses were performed on the placenta models according to a delineated training module by “trained” participants (10 practicing neurosurgeons and 7 residents with microsurgical experience) and “untrained” participants (10 medical students and 3 residents without experience). Anastomosis performance and impressions of the model were assessed using the Northwestern Objective Microanastomosis Assessment Tool (NOMAT) scale and a posttraining survey.

RESULTS

Human placental arteries were found to approximate the M2–M4 cerebral and superficial temporal arteries, and bovine placental veins were found to approximate the internal carotid and radial arteries. The mean NOMAT performance score was 37.2 ± 7.0 in the untrained group versus 62.7 ± 6.1 in the trained group (p < 0.01; construct validity). A 50% probability of allocation to either group corresponded to 50 NOMAT points. In the posttraining survey, 16 of 17 of the trained participants (94%) scored the model's replication of real bypass surgery as high, and 16 of 17 (94%) scored the difficulty as “the same” (face validity). All participants, 30 of 30 (100%), answered positively to questions regarding the ability of the model to improve microsurgical technique (content validity).

CONCLUSIONS

Human placental arteries and bovine placental veins are convenient, anatomically relevant, and beneficial models for microneurosurgical training. Microanastomosis simulation using these models has high face, content, and construct validities. A NOMAT score of more than 50 indicated successful performance of the microanastomosis tasks.

Risk factors for neurological worsening and symptomatic watershed infarction in internal carotid artery aneurysm treated by extracranial-intracranial bypass using radial artery graft

OBJECT

The revascularization technique, including bypass created using the external carotid artery (ECA), radial artery (RA), and M2 portion of middle cerebral artery (MCA), has remained indispensable for treatment of complex aneurysms. To date, it remains unknown whether diameters of the RA, superficial temporal artery (STA), and C2 portion of the internal carotid artery (ICA) and intraoperative MCA blood pressure have influences on the outcome and the symptomatic watershed infarction (WI). The aim of the present study was to evaluate the factors for the symptomatic WI and neurological worsening in patients treated by ECA-RA-M2 bypass for complex ICA aneurysm with therapeutic ICA occlusion.

METHODS

The authors measured the sizes of vessels (RA, C2, M2, and STA) and intraoperative MCA blood pressure (initial, after ICA occlusion, and after releasing the RA graft bypass) in 37 patients. Symptomatic WI was defined as presence of the following: postoperative new neurological deficits, WI on postoperative diffusion-weighted imaging, and ipsilateral cerebral blood flow reduction on SPECT. Neurological worsening was defined as the increase in 1 or more modified Rankin Scale scores. First, the authors performed receiver operating characteristic curve analysis for continuous variables and the binary end point of the symptomatic WI. The clinical, radiological, and physiological characteristics of patients with and without the symptomatic WI were compared using the log-rank test. Then, the authors compared the variables between patients with and without neurological worsening at discharge and at the 12-month follow-up examination or last hospital visit.

RESULTS

Symptomatic WI was observed in 2 (5.4%) patients. The mean MCA pressure after releasing the RA graft (< 55 mm Hg; p = 0.017), mean (MCA pressure after releasing the RA graft)/(initial MCA pressure) (< 0.70 mm Hg; p = 0.032), and mean cross-sectional area ratio ([RA/C2 diameter]2 < 0.40 mm [p < 0.0001] and [STA/C2 diameter]2 < 0.044 mm [p < 0.0001]) were related to the symptomatic WI. All preoperatively independent patients remained independent (modified Rankin Scale score < 3). After adjusting for age and sex, left operative side (p = 0.0090 and 0.038) and perforating artery ischemia (p = 0.0050 and 0.022) were related to neurological worsening at discharge (11 [29%] patients) and at the 12-month follow-up or last hospital visit (8 [22%] patients).

CONCLUSIONS

Results of the present study showed that the vessel diameter and intraoperative MCA pressure had impacts on the symptomatic WI and that operative side and perforating artery ischemia were related to neurological worsening in patients with complex ICA aneurysms treated by ECA-RA-M2 bypass.

Urgent treatment of severe symptomatic direct carotid cavernous fistula caused by ruptured cavernous internal carotid artery aneurysm using high-flow bypass, proximal ligation, and direct distal clipping: Technical case report

Background:

Direct carotid cavernous fistula (CCF) secondary to ruptured carotid cavernous aneurysms (CCAs) is rare, but patients with this condition who develop acutely worsening and severe neuro-ophthalmic symptoms require urgent treatment. Endovascular methods are the first-line option, but this modality may not be available on an urgent basis.

Case Description:

In this article, we report a 45-year-old female with severe direct CCF due to rupture of the CCA. She presented with intractable headache and acute worsening of double vision and visual acuity. Emergent radiographic study revealed high-flow fistula tracked from the CCA toward the contralateral cavernous sinus and drained into the engorged left superior orbital vein. To prevent permanent devastating neuro-ophthalmic damages, urgent high-flow bypass with placement of a radial artery graft was performed followed by right cervical internal carotid artery (ICA) ligation and the clipping of the ICA at the C3 portion, proximal to the ophthalmic artery. In the immediate postoperative period, her symptoms resolved and angiography confirmed patency of the high-flow bypass and complete occlusion of the CCF.

Conclusion:

With due consideration of strategy and techniques to secure safety, open surgical intervention with trapping and bypass is a good treatment option for direct severe CCF when the endovascular method is not available, not possible, or is unsuccessful.

EC-IC bypass for cavernous carotid aneurysms: An initial experience with twelve patients

AIMS

Need for performing a bypass procedure prior to parent artery occlusion in patients with good cerebral vascular reserve is controversial. We analyze our experience of 12 giant internal carotid artery aneurysms treated with extracranial-intracranial (EC-IC) bypass and proximal artery occlusion.

MATERIALS AND METHODS

Retrospective analysis of the case records of all complex carotid aneurysms operated in our institute since January 2009.

RESULTS

The study included eleven cavernous carotid aneurysms and one large fusiform cervical carotid aneurysm reaching the skull base. Preoperative assessment of cerebral vascular reserve was limited to Balloon test occlusion with hypotensive challenge. Eleven patients who successfully completed a Balloon test occlusion (BTO) underwent low flow superficial temporal artery to middle cerebral artery (STA-MCA) bypass, while one patient with a failed BTO underwent a high flow bypass using a saphenous vein graft. Parent artery ligation was performed in all patients following the bypass procedure. Check angiogram revealed thrombosis of the aneurysm in all patients with a graft patency rate of 81.8%. We had one operative mortality, probably related to a leak from the anastomotic site. The only patient who had a high flow bypass developed contralateral hemispheric infarcts and remained vegetative. All the other patients had a good recovery and with a Glasgow outcome score of 5 at last follow-up.

CONCLUSION

We feel that combining EC-IC bypass prior to parent vessel occlusion helps in reducing the risk of post operative ischemic complications especially in situations where a complete mandated cerebral blood flow studies are not feasible.

Cerebral revascularization and carotid artery resection at the skull base for treatment of advanced head and neck malignancies

Object

Resection of cancer and the involved artery in the neck has been applied with some success, but the indications for such an aggressive approach at the skull base are less well defined. The authors therefore evaluated the outcomes of advanced skull base malignancies in patients who were treated with bypass and resection of the internal carotid artery (ICA).

Methods

The authors retrospectively reviewed the charts of all patients with advanced head and neck cancers who underwent ICA sacrifice with revascularization in which an extracranial-intracranial bypass was used between 1995 and 2010 at the Barrow Neurological Institute.

Results

Eighteen patients (11 male and 7 female patients; mean age 46 years, range 7–69 years) were identified. There were 4 sarcomas and 14 carcinomas that involved the ICA at the skull base. All patients underwent ICA sacrifice with revascularization. One patient died of a stroke after revascularization. A second patient died of the effects of a fistula between the oral and cranial cavities (surgery-related mortality rate 11.1%). Eight months after the operation, 1 patient developed occlusion of the bypass and died. Complications associated with the bypass surgery included 1 case of subdural hematoma (SDH) with blindness, 1 case of status epilepticus, and 1 case of asymptomatic bypass occlusion (bypass-related morbidity 16.7%). Complications associated with tumor resection included 3 cases of CSF leakage requiring repair and shunting, 1 case of hydrocephalus requiring shunting, 1 case of SDH, and 1 case of contralateral ICA injury requiring a bypass (tumor resection morbidity rate 33.3%). In 1 patient treated with adjuvant therapy before surgery, the authors identified only a radiation effect and no tumor on resection. In a second patient the bypass was occluded, and her tumor was not resected. The other 16 patients underwent gross-total resection of their tumor. Excluding the surgery-related deaths, the mean and median lengths of survival in this series were 13.2 and 8.3 months, respectively (range 1.5–48 months). Including the surgery-related deaths, the mean and median lengths of survival were 11.8 and 8 months, respectively (range 17 days–48 months). At last follow-up all patients had died of cancer or cancer-related causes.

Conclusions

Despite maximal surgical intervention, including ICA sacrifice at the skull base with revascularization, patient survival was dismal, and the complication rate was significant. The authors no longer advocate such an aggressive approach in this patient population. On rare occasions, however, such an approach may be considered for low-grade malignancies.

Petrous carotid exposure with eustachian tube preservation: a morphometric elucidation

Inadvertent injury to eustachian tube leading to cerebrospinal fluid rhinorrhea is a known complication associated with drilling of Glasscock's triangle to expose the horizontal petrous internal carotid artery (ICA) for management of difficult tumors (especially malignant) or aneurysms at the cranial base. Contrary to the usual approach, we hypothesize that a "medial-to-lateral" approach to Glasscock's triangle drilling will minimize eustachian tube injury. Four formalin-fixed human cadaveric heads were dissected, and underwent appropriate morphometric analysis; yielding a total of eight datasets. The diameter of the horizontal petrous ICA exposed was 4.7 ± 0.9 mm (range, 3.8 to 5.6 mm).The mean distance from the medial carotid wall midpoint to the medial-most point on the eustachian tube was 6.35 ± 0.58 mm (range, 5.4 to 7.1 mm), yielding a "safety zone" for eustachian tube, ranging 0.2 to 1.9 mm lateral to the lateral carotid wall. With the medial-to-lateral approach, the eustachian tube remained preserved in all the specimens. The results of our study provide a practical, consistent, and safe method of maximizing horizontal petrous carotid artery exposure while minimizing the eustachian tube injury.

Extracranial-intracranial bypass surgery using a radial artery interposition graft for cerebrovascular diseases

OBJECTIVE

To investigate the efficacy of extracranial-intracranial (EC-IC) bypass surgery using a radial artery interposition graft (RAIG) for surgical management of cerebrovascular diseases.

METHODS

The study involved a retrospective analysis of 13 patients who underwent EC-IC bypass surgery using RAIG at a single neurosurgical institute between 2003 and 2009. The diseases comprised intracranial aneurysm (n=10), carotid artery occlusive disease (n=2), and delayed stenosis in the donor superficial temporal artery (STA) following previous STA-middle cerebral artery bypass surgery (n=1). Patients were followed clinically and radiographically.

RESULTS

Bypass surgery was successful in all patients. At a mean follow-up of 53.4 months, the short-term patency rate was 100%, and the long-term rate was 92.3%. Twelve patients had an excellent clinical outcome of Glasgow Outcome Scale (GOS) 5, and one case had GOS 3. Procedure-related complications were a temporary dysthesia on the graft harvest hand (n=1) and a hematoma at the graft harvest site (n=1), and these were treated successfully with no permanent sequelae. In one case, spasm occurred which was relieved with the introduction of mechanical dilators.

CONCLUSION

EC-IC bypass using a RAIG appears to be an effective treatment for a variety of cerebrovascular diseases requiring proximal occlusion or trapping of the parent artery.

Graft selection in cerebral revascularization

Cerebral revascularization constitutes an important treatment modality in the management of complex aneurysms, carotid occlusion, tumor, and moyamoya disease. Graft selection is a critical step in the planning of revascularization surgery, and depends on an understanding of graft and regional hemodynamics, accessibility, and patency rates. The goal of this review is to highlight some of these properties.

Predictors of patency of excimer laser–assisted nonocclusive extracranial-to-intracranial bypasses

Object

Excimer laser–assisted nonocclusive anastomosis (ELANA) is a technique that can be used for extracranial-to-intracranial (EC-IC) bypasses, without the necessity of temporary occlusion of the donor or recipient artery. Information on predictors of patency of EC-IC bypasses in general and the ELANA bypass in particular is sparse. The authors studied 159 ELANA EC-IC bypasses to find predictors of patency.

Methods

From a prospective database of patients who underwent EC-IC bypass surgery, 143 consecutive patients who underwent a total of 159 ELANA bypasses were studied. The associations of patient characteristics, surgical aspects, and technical aspects specific to the ELANA technique with intraoperative and postoperative bypass patency were studied using logistic regression analysis.

Results

At the end of the operation, 146 (92%) of the 159 bypasses were patent. A first attempt to create a bypass was almost 8 times more likely (OR 7.6, 95% CI 2.1–27.5; p = 0.02) to result in a patent bypass than a second attempt. Administration of a small amount of heparin during the operation was also associated with bypass patency (OR 5.2, 95% CI 1.1–24.9; p = 0.04). One hundred twenty-three (77%) of the 159 bypasses were functional at patency assessments during the 1st month after the operation. Older age (OR 1.043 for every year of increase in age, 95% CI 1.010–1.076; p = 0.01), male sex (OR 2.9, 95% CI 1.3–6.5; p = 0.01), and high intraoperative bypass flow (OR 1.017 for every milliliter per minute increase in flow, 95% CI 1.004–1.030; p = 0.01) were associated with postoperative bypass patency.

Conclusions

Attempts to create a second EC-IC ELANA bypass after the first one are more likely to fail, whereas administration of heparin to the patient during the procedure increases the intraoperative bypass patency rate. Postoperative patency results are better in male and in older patients. Intraoperative bypass flow measurements are essential because high bypass flow is an important determinant of postoperative patency.

Result of extracranial-intracranial bypass surgery in the treatment of complex intracranial aneurysms : outcomes in 15 cases

OBJECTIVE

The standard treatment strategy of intracranial aneurysms includes either endovascular coiling or microsurgical clipping. In certain situations such as in giant or dissecting aneurysms, bypass surgery followed by proximal occlusion or trapping of parent artery is required.

METHODS

The authors assessed the result of extracranial-intracranial (EC-IC) bypass surgery in the treatment of complex intracranial aneurysms in one institute between 2003 and 2007 retrospectively to propose its role as treatment modality. The outcomes of 15 patients with complex aneurysms treated during the last 5 years were reviewed. Six male and 9 female patients, aged 14 to 76 years, presented with symptoms related to hemorrhage in 6 cases, transient ischemic attack (TIA) in 2 unruptured cases, and permanent infarction in one, and compressive symptoms in 3 cases. Aneurysms were mainly in the internal carotid artery (ICA) in 11 cases, middle cerebral artery (MCA) in 2, posterior cerebral artery (PCA) in one and posterior inferior cerebellar artery (PICA) in one case.

RESULTS

The types of aneurysms were 8 cases of large to giant size aneurysms, 5 cases of ICA blood blister-like aneurysms, one dissecting aneurysm, and one pseudoaneurysm related to trauma. High-flow bypass surgery was done in 6 cases with radial artery graft (RAG) in five and saphenous vein graft (SVG) in one. Low-flow bypass was done in nine cases using superficial temporal artery (STA) in eight and occipital artery (OA) in one case. Parent artery occlusion was performed with clipping in 9 patients, with coiling in 4, and with balloon plus coil in 1. Direct aneurysm clip was done in one case. The follow up period ranged from 2 to 48 months (mean 15.0 months). There was no mortality case. The long-term clinical outcome measured by Glasgow outcome scale (GOS) showed good or excellent outcome in 13/15. The overall surgery related morbidity was 20% (3/15) including 2 emergency bypass surgeries due to unexpected parent artery occlusion during direct clipping procedure. The short-term postoperative bypass graft patency rates were 100% but the long-term bypass patency rates were 86.7% (13/15). Nonetheless, there was no bypass surgery related morbidity due to occlusion of the graft.

CONCLUSION

Revascularization technique is a pivotal armament in managing complex aneurysms and scrupulous prior planning is essential to successful outcomes.

Use of radial artery grafts in extracranial-intracranial revascularization procedures

Cerebral revascularization procedures have been used in the clinical management of actual or threatened cerebral ischemic states and unclippable cerebral aneurysms. An alternative to a low-flow bypass graft (for example, with the superficial temporal artery) is the use of high-flow grafts created using the saphenous vein (SV) or radial artery (RA). These high-flow grafts are particularly useful when otherwise adequate collateral flow is insufficient to enable sacrifice of the parent vessel without the risk of cerebral ischemia. In their clinical series of 13 patients who underwent high-flow bypass with an RA graft, the authors describe 8 women and 5 men whose ages ranged from 44 to 69 years (mean 57.84 +/- 9.05 years). Indications for RA graft bypass were unclippable aneurysms in 10 patients and occlusive cerebrovascular disease in 3 patients. The authors review the properties of the 2 most common conduits, the SV and RA grafts. They present the technique of high-flow extracranial-intracranial bypass produced using RA grafts in the management of occlusive atherosclerotic disease and complex intracranial aneurysms that are not otherwise amenable to either clip ligation or coil occlusion.

Revascularization for complex intracranial aneurysms

The modern management of intracranial aneurysms includes both constructive and deconstructive strategies to eliminate the aneurysm from the circulation. Both microsurgical and endovascular techniques are used to achieve this goal. Although most aneurysms can be eliminated from the circulation with simple clip reconstruction and/or coil insertion, some require revascularization techniques to enhance tolerance of temporary arterial occlusion during clipping of the aneurysm neck or to enable proximal occlusion or trapping. In fact, the importance of revascularization techniques has grown because of the need for complex reconstructions when endovascular therapies fail. Moreover, the safety and feasibility of bypass have progressed due to advances in neuroanesthesia, technological innovations, and ~ 5 decades of accumulating wisdom by bypass practitioners. Cerebral revascularization strategies become necessary in select patients who possess challenging vascular aneurysms due to size, shape, location, intramural thrombus, atherosclerotic plaques, aneurysm type (for example, dissecting aneurysms), vessels arising from the dome, or poor collateral vascularization when parent artery or branch occlusion is required. These techniques are used to prevent cerebral ischemia and subsequent clinical sequelae. Bypass techniques should be considered in cases in which balloon test occlusion demonstrates inadequate cerebral blood flow and in which there is a need for Hunterian ligation, trapping, or prolonged temporary occlusion. This review article will focus on decision making in bypass surgery for complex aneurysms. Specifically, the authors will review graft options, the utility of balloon test occlusion in decision making, and bypass strategies for various aneurysm types.

Giant fusiform aneurysm in an adolescent with PHACES syndrome treated with a high-flow external carotid artery-M3 bypass. Case report and review of the literature

The acronym PHACES describes a rare neurocutaneous syndrome that comprises posterior fossa malformations, facial hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternal defects. Facial hemangiomas constitute the hallmark of this disorder. Giant intracranial aneurysms have not been previously reported in the literature as manifestations of PHACES syndrome and can present difficult therapeutic challenges. The authors describe a unique case of a 13-year-old adolescent boy with an incomplete phenotypic expression of PHACES syndrome who harbored diffuse cerebral angiodysplasia and a giant fusiform internal carotid artery (ICA) aneurysm extending from the distal cavernous segment to the supraclinoid segment. The aneurysm was successfully treated with a high-flow saphenous vein graft bypass from the external carotid artery to the distal middle cerebral artery followed by proximal ICA occlusion. This case represents a unique vascular manifestation of PHACES syndrome that required a complex management strategy. The authors review the literature on this rare disorder and emphasize the importance of considering the diagnosis of PHACES syndrome in child with a facial hemangioma.

Cerebral revascularization in skull base tumors

Skull base tumors involving the carotid artery pose a difficult surgical challenge. The potential for bypass grafting for cerebral revascularization carries inherent risks but may aid in tumor resection and control in those who warrant carotid sacrifice but have inappropriate natural cerebrovascular reserve. We include a review of the literature discussing the indications for carotid resection as part of skull base tumor surgery, indications for cerebral revascularization, balloon test occlusion, graft types and operative technique, complications, and results.

Revascularization for complex skull base tumors

We discuss revascularization techniques for complex skull base lesions utilizing high-flow arterial bypass. At present, the radial artery is the donor graft utilized in most circumstances at our institution. The knowledge of revascularization techniques is very important to achieve radical resection in lesions where arterial compromise is documented.

ELANA: Excimer Laser-Assisted Nonocclusive Anastomosis for extracranial-to-intracranial and intracranial-to-intracranial bypass: a review

ELANA, excimer laser-assisted nonocclusive anastomosis, is a technique using an excimer laser/catheter system for intracranial bypass surgery of the brain. The technique has been developed over the past 12 years by Tulleken and colleagues at UMC Utrecht in The Netherlands for treatment of primarily untreatable giant aneurysms. We review here the emergence of transplanted conduit bypass as a valuable technique for managing these lesions and the subsequent development of ELANA bypass. The ELANA technique allows the operating surgeon to perform an extracranial-to-intracranial or intracranial-to-intracranial bypass using a transplanted large caliber conduit without occlusion of the recipient artery, thus eliminating intraoperative ischemic insult related to temporary occlusion time. We describe the ELANA technique, illustrate it with intraoperative photos, and review the relevant literature. ELANA is shown to be safe; we discuss its advantages over conventional techniques.

Revascularization of the posterior circulation

The primary objective of revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke. Specific anatomical and neurophysiologic characteristics such as posterior communicating artery size affect the susceptibility to ischemia. Current indications for revascularization include symptomatic vertebrobasilar ischemia refractory to medical therapy and ischemia caused by parent vessel occlusion as treatment for complex aneurysms. Treatment options include endovascular angioplasty and stenting, surgical endarterectomy, arterial reimplantation, extracranial-to-intracranial anastomosis, and indirect bypasses. Pretreatment studies including cerebral blood flow measurements with assessment of hemodynamic reserve can affect treatment decisions. Careful blood pressure regulation, neurophysiologic monitoring, and neuroprotective measures such as mild brain hypothermia can help minimize the risks of intervention. Microscope, microinstruments and intraoperative Doppler are routinely used. The superficial temporal artery, occipital artery, and external carotid artery can be used to augment blood flow to the superior cerebellar artery, posterior cerebral artery, posterior inferior cerebellar artery, or anterior inferior cerebellar artery. Interposition venous or arterial grafts can be used to increase length. Several published series report improvement or relief of symptoms in 60 to 100% of patients with a reduction of risk of future stroke and low complication rates.

Selective cerebral revascularization as an adjunct in the treatment of giant anterior circulation aneurysms

Cerebral revascularization, an indispensable component of neurovascular surgery, has been performed in the treatment of cranial base tumors, complex cerebral aneurysms, and occlusive cerebrovascular disease. The goal of a revascularization procedure is to augment blood flow distally. It can therefore be used as an adjunctive measure in the treatment of complex neurosurgical disease processes that require parent artery sacrifice for definitive treatment. In the treatment of giant anterior circulation aneurysms, for instance, a cerebral revascularization procedure may be considered in patients in whom the collateral circulation is marginal and in whom lesions may be treated either using a Hunterian-based strategy or clip-assisted reconstruction requiring a prolonged period of temporary occlusion. To date, there is no entirely effective method known to produce long-term tolerance to carotid artery (CA) sacrifice and, largely for that reason, some neurovascular surgeons advocate universal revascularization. The authors of this report, however, prefer to perform revascularization only in the limited subset of patients in whom preoperative assessment has revealed risk factors for cerebral ischemia due to hypoperfusion. In this paper, the authors introduce their protocol for assessing cerebrovascular reserve capacity, indications for cerebral revascularization in the treatment of complex anterior circulation aneurysms, and discuss their rationale for choosing to practice selective, rather than universal, revascularization.

Conduits for cerebrovascular bypass and lessons learned from the cardiovascular experience

Direct cerebral revascularization is an important procedure in the treatment of certain complex aneurysms and skull base tumors when acute sacrifice of the internal carotid artery is required. It likely remains an appropriate treatment in a small subgroup of patients with cerebral ischemia refractory to maximal medical management. Similar to cardiovascular surgery, the choice of a graft conduit is critical for a successful outcome. The standard conduits are interposition vein grafts (usually the greater saphenous vein), free arterial grafts (radial artery), and pedicled arterial grafts (superficial temporal artery). The goal of this review is to summarize the conduits commonly used in cerebral revascularization with emphasis on their patency rates and flow characteristics. Comparisons are made with similar data available in the cardiovascular literature.

Interpositional carotid artery bypass strategies in the surgical management of aneurysms and tumors of the skull base

Cerebral revascularization is an important component in the surgical management of complex skull base tumors and aneurysms. Patients who harbor complex aneurysms that cannot be clipped directly and in whom parent vessel occlusion cannot be tolerated may require cerebrovascular bypass surgery. In cases in which skull base tumors encase the carotid artery (CA) and a resection is desired, a cerebrovascular bypass may be necessary in planned CA occlusion or sacrifice. In this review the authors discuss options for performing high-flow anterograde interposition CA bypass for lesions of the skull base. The authors review three important bypass techniques involving saphenous vein grafts: the cervical-to-petrous internal carotid artery (ICA), petrous-to-supraclinoid ICA, and cervical-to-supraclinoid ICA bypass. These revascularization techniques are important tools in the surgical treatment of complex aneurysms and tumors of the skull base and cavernous sinus.