Petrous carotid-to-intradural carotid saphenous vein graft for intracavernous giant aneurysm, tumor, and occlusive cerebrovascular disease

C2-P2 Bypass: Technical Assessment of Petrous Carotid Artery to Posterior Cerebral Artery Interpositional Bypass Through the Combined Transcochlear-Subtemporal Approach as a Part of Microsurgical Treatment for Dolichoectatic Vertebrobasilar Artery Aneurysms

BACKGROUND AND OBJECTIVES

Managing dolichoectatic vertebrobasilar artery aneurysms requires a multifaceted approach. Revascularization of the posterior circulation with a high-flow bypass is part of the flow reversal paradigm. Performing a robust high-flow bypass and addressing the aneurysm through the same approach smooths the operative intervention. This study assessed the anatomic feasibility of accessing the basilar trunk and aneurysm simultaneously to revascularize the posterior circulation using a petrous internal carotid artery (pICA)-posterior cerebral artery (PCA) interpositional bypass through a complete petrosectomy.

METHODS

Six embalmed cadaveric heads (12 sides) underwent a combined extended transcochlear-subtemporal approach to expose the pICA and P2 PCA. A pICA (side-to-end) graft (end-to-side) PCA bypass was attempted. The lengths of the vessels relevant to the bypass and the graft length were measured.

RESULTS

The bypass was successfully completed in all specimens. The mean exposed lengths of the pICA and PCA were 21.3 and 20.0 mm, respectively. The mean length of the perforator-free zone on PCA was 11.2 mm. The mean length of the interposition graft was 36.6 mm.

CONCLUSION

The transcochlear approach can be used to expose the pICA as a donor for a high-flow bypass to the PCA as part of the treatment paradigm for dolichoectatic vertebrobasilar artery aneurysms. Careful patient selection and extensive knowledge of skull base anatomy are mandatory for this strategy.

Application of surgical revascularization technique in giant aneurysm of the extracranial internal carotid artery: technical report

PURPOSE

The purpose of this study is to illustrate the diagnostic and therapeutic value and clinical significance of surgical revascularization in giant aneurysms of the extracranial internal carotid artery.

METHODS

The research team screened a group of cases of giant aneurysms of the extracranial internal carotid artery and analyzed the detailed information of the enrolled patients in terms of their basic clinical characteristics, surgical approaches and clinical prognosis.

RESULTS

All patients had a good prognosis, except for one patient who was left with only mild facial nerve palsy (grade II facial paralysis). The results demonstrate that surgical revascularization is effective and safe in the treatment of giant aneurysms of the extracranial internal carotid artery.

CONCLUSION

The significant conclusion of this study is to provide an ideal alternative treatment for the treatment of giant aneurysms of the extracranial internal carotid artery. The surgical revascularization technique is a powerful tool for vascular neurosurgeons in the management of complex cerebrovascular diseases when traditional surgical clipping or endovascular interventions encounter bottlenecks.

Petrous Carotid to Upper Posterior Circulation Bypass for the Treatment of Basilar Trunk Aneurysm: A Novel High-Flow Intracranial-Intracranial Skull Base Bypass for Posterior Circulation

BACKGROUND

Basilar trunk aneurysms are the most surgically challenging, and the spectrum covers small fusiform to dolichoectatic aneurysms and may lead to rupture, brain ischemia, or direct brainstem compression. The current strategy remains cerebral revascularization coupled with aneurysm trapping. Available bypass options for upper posterior circulation (UPC) are based on (1) different flow volumes from diverse blood supplies and (2) distinct modulation purposes for cerebral revascularization; however, the potential compromise of eloquent perforators of the basilar trunk and the occurrence of fatal brainstem infarcts remain unacceptable.

OBJECTIVE

To innovate a high-flow intracranial-intracranial skull base bypass for posterior circulation to afford robust retrograde flow and shorten the graft length.

METHODS

We retrospectively reviewed our experience in the treatment of a patient with basilar trunk aneurysm and reported a novel bypass alternative supplied by petrous internal carotid artery to augment blood flow to the UPC by a pretemporal approach.

RESULTS

The postoperative course was uneventful, and there was no pons or midbrain ischemia or other complications. Postoperative computed tomography angiogram revealed the patency of bypass. There was no further development or rerupture observed during follow-up.

CONCLUSION

Petrous internal carotid artery as a donor site is a reliable bypass modality for UPC. This approach provides the utmost retrograde flow to alleviate the development of dissecting aneurysms, preserves eloquent perforators of the basilar trunk, maintains bypass patency, and shortens the graft course. Therefore, this novel therapeutic alternative could be beneficial for improving the prognosis of basilar trunk aneurysms.

Fresh Cadaver Simulation Model with Continuous Extracorporeal Circulation as a Training Platform for Intracranial High-Flow Bypass: Technical Note and Rheologic Feasibility Evaluation

Introduction As endovascular techniques evolve toward replacing open surgery, several clinical scenarios still require surgical revascularization. Characterizing this era are decreasing surgical volumes and lack of realistic training models. In an effort to develop lifelike simulation models, we developed a platform for surgical training on high-flow bypass in a fresh cadaver model. Our technique incorporated an extracorporeal circulating system that resembled clinical conditions and confirmed anastomosis efficacy by clinical parameters.

Methods On three fresh cadaveric heads, the subtemporal approach exposed the petrous internal carotid artery (ICA) (C2) as the donor vessel for an interposition radial artery graft. Using a continuous extracorporeal circulation system, the bypass model was tested in three fresh heads and verified using clinical technologies.

Results Successful C2 ICA to M2 anastomosis was completed in all three fresh heads, confirmed with qualitative and quantitative Doppler, and indocyanine green angiography. Antegrade distribution through graft and revascularized territory was documented on postoperative computed tomography (CT) scan with radiopaque silicone injected through the ipsilateral carotid.

Conclusion This study confirmed the feasibility of a totally intracranial high-flow bypass in a fresh cadaver model that achieved hemodynamic features aligned with those of normal middle cerebral artery flow in the clinical setting.

Extra-intracranial bypass surgery using the orifice of maxillary artery in a patient with middle cerebral artery aneurysm. Case report and literature review

OBJECTIVE

To present the technique of extra-intracranial bypass surgery using the orifice of maxillary artery bypass, to evaluate the advantages and disadvantages of this and alternative revascularization options.

MATERIAL AND METHODS

Radial artery graft harvesting was performed at the 1st stage. Simultaneously, the second team of surgeons performed a combined (submandibular and anterior) access to the donor artery (mandibular segment of maxillary artery behind the ramus of the mandible). Craniotomy and mobilization of potential recipient arteries (M2-M3 segments of the middle cerebral artery) were performed at the 2nd stage. Distal anastomosis in end-to-side fashion was formed with M3 segment of the middle cerebral artery. At the 3rd stage, radial artery was passed through a subcutaneous tunnel in zygomatic region. The orifice of maxillary artery was resected together with distal external carotid artery (ECA) and orifice of superficial temporal artery. After transposition of ECA and orifice of maxillary artery, proximal end-to-end anastomosis was performed with radial artery. After that, the main surgical stage was performed, i.e. exclusion of M3 segment of the middle cerebral artery together with aneurysm.

RESULTS

Harvesting of mandibular segment of the maxillary artery as a donor vessel reduces the length of bypass graft to 12-14 cm since this branch is localized close to the skull base. You can also form optimal proximal end-to-end anastomosis for intracranial redirecting blood flow maxillary artery.

CONCLUSION

The described method makes it possible to form anastomosis with a short bypass graft and reduce the risk of thrombosis. This procedure is effective for cerebral bypass in patients with skull base tumors, complex aneurysms, and occlusive-stenotic lesions of carotid arteries.

An endovascular assisted, nonocclusive cerebral bypass: a technical feasibility study in a rabbit model

OBJECTIVE

Temporary parent vessel occlusion performed to establish a high-flow interpositional bypass carries the risk of infarcts. The authors investigated the feasibility of a novel technique to establish a high-flow bypass without temporary parent vessel occlusion in order to lower the risk of ischemic complications.

METHODS

In 10 New Zealand white rabbits, a carotid artery side-to-end anastomosis was performed under parent artery patency with a novel endovascular balloon device. Intraoperative angiography, postoperative neurological assessments, and postoperative MRI/MRA were performed to evaluate the feasibility and safety of the novel technique.

RESULTS

A patent anastomosis was established in 10 of 10 animals; 3 procedure-related complications occurred. No postoperative focal neurological deficits were observed. The MRI/MRA findings include no infarcts and bypass patency in 50% of the animals.

CONCLUSIONS

The authors demonstrated the feasibility of an endovascular assisted, nonocclusive high-flow bypass. Future refinement of the device and technique in an animal model is necessary to lower the complication rate and increase patency rates.

Multimodal management of giant cerebral aneurysms: review of literature and case presentation

The pathophysiology of giant cerebral aneurysms renders them difficult to treat. Advances in technology have attempted to address any shortcomings associated with open surgery or endovascular therapies. Since the introduction of the flow diversion technique, the endovascular approach with flow diversion has become the first-line modality chosen to treat giant aneurysms. A subset of these giant aneurysms may persistent despite any treatment modality. Perhaps the best option for these recurrent and/or persistent giant aneurysms is to employ a multimodal approach-both surgical and endovascular-rather than any single technique to provide a curative result with favourable patient outcomes. This paper provides a review of the histopathology and treatment options for giant cerebral aneurysms. Additionally, an illustrative case is presented to highlight the unique challenges of a curative solution for giant cerebral aneurysms that persist despite initial treatment.

Clinical utility and versatility of the petrous segment of the internal carotid artery in revascularization

Direct approaches to high cervical lesions, including tumors and aneurysms, carry significant risks. This renders alternative approaches desirable, with vascular disease amenable to exclusion and revascularization to the intracranial circulation, including the petrous or supraclinoid segments of the internal carotid artery (ICA). The cervicopetrous ICA bypass via saphenous venous grafting has proven an effective strategy for treating and excluding these lesions. In current practice, this is performed via an extradural subtemporal approach to access the petrous segment of the ICA and a cervical incision for access to the cervical ICA. The venous graft is alternately tunneled subcutaneously or in situ through the cervical ICA, with the latter eschewing external compression, kinking, and torsion, which increases risk of graft thrombosis with the former. Maxillary or middle meningeal arteries may also serve as donors to the petrous ICA. Moreover, the petrous ICA may be used as a donor in revascularization procedures, to the supraclinoid segment of the ICA and the middle cerebral artery, with petrous supraclinoid and petrous-MCA bypasses described. Clinical utility and operative approaches bypassing to or from the petrous ICA in revascularization procedures are reviewed and discussed.

Flow Diversion for the Treatment of Petrous Internal Carotid Artery Aneurysms

Petrous internal carotid artery (ICA) aneurysms are rare and pose a unique management dilemma. They are most commonly fusiform. They are difficult to treat surgically and typically not amenable to selective aneurysmal obliteration. The advent of flow diverters, such as the Pipeline endovascular device, has offered a new approach to these historically challenging lesions. The unique utility of flow diversion in treatment of petrous ICA aneurysms is reviewed and discussed.

EC-IC bypass for cerebral revascularization following skull base tumor resection: Current practices and innovations

Complex skull base tumors can involve critical vessels of the head and neck. To achieve a gross total resection, vessel sacrifice may be necessary. In cases where vessel sacrifice will cause symptomatic cerebral ischemia, surgical revascularization is required. The purpose of this paper is to review cerebral revascularization for skull base tumors, the indications for these procedures, outcomes, advances, and future directions.

Management of Cavernous Sinus Involvement in Sinonasal and Ventral Skull Base Malignancies

Cavernous sinus (CS) involvement by sinonasal and ventral skull base malignancies is infrequently encountered in neurosurgical practice. Despite advancements in skull base microneurosurgery and endoscopic techniques, detailed knowledge and experience of the surgical management of these lesions are limited. This article elaborates on surgical strategies and approaches for CS involvement of malignant ventral skull base tumors. The article discusses the indications, techniques, nuances, advantages, limitations, and complications of minimally invasive CS biopsy, transcranial microscopic, and transfacial endoscopic approaches to the CS using illustrative diagrams and operative videos. The principles and nuances of a high-flow cerebral revascularization procedure are mentioned.

Proposed clinical internal carotid artery classification system

INTRODUCTION

Numerical classification systems for the internal carotid artery (ICA) are available, but modifications have added confusion to the numerical systems. Furthermore, previous classifications may not be applicable uniformly to microsurgical and endoscopic procedures. The purpose of this study was to develop a clinically useful classification system.

MATERIALS AND METHODS

We performed cadaver dissections of the ICA in 5 heads (10 sides) and evaluated 648 internal carotid arteries with computed tomography angiography. We identified specific anatomic landmarks to define the beginning and end of each ICA segment.

RESULTS

The ICA was classified into eight segments based on the cadaver and imaging findings: (1) Cervical segment; (2) cochlear segment (ascending segment of the ICA in the temporal bone) (relation of the start of this segment to the base of the styloid process: Above, 425 sides [80%]; below, 2 sides [0.4%]; at same level, 107 sides [20%]; P < 0.0001) (relation of cochlea to ICA: Posterior, 501 sides [85%]; posteromedial, 84 sides [14%]; P < 0.0001); (3) petrous segment (horizontal segment of ICA in the temporal bone) starting at the crossing of the eustachian tube superolateral to the ICA turn in all 10 samples; (4) Gasserian-Clival segment (ascending segment of ICA in the cavernous sinus) starting at the petrolingual ligament (PLL) (relation to vidian canal on imaging: At same level, 360 sides [63%]; below, 154 sides [27%]; above, 53 sides [9%]; P < 0.0001); in this segment, the ICA projected medially toward the clivus in 275 sides (52%) or parallel to the clivus with no deviation in 256 sides (48%; P < 0.0001); (5) sellar segment (medial loop of ICA in the cavernous sinus) starting at the takeoff of the meningeal hypophyseal trunk (ICA was medial into the sella in 271 cases [46%], lateral without touching the sella in 127 cases [23%], and abutting the sella in 182 cases [31%]; P < 0.0001); (6) sphenoid segment (lateral loop of ICA within the cavernous sinus) starting at the crossing of the fourth cranial nerve on the lateral aspect of the cavernous ICA and located directly lateral to the sphenoid sinus; (7) ring segment (ICA between the 2 dural rings) starting at the crossing of the third cranial nerve on the lateral aspect of the ICA; (8) cisternal segment starting at the distal dural ring.

CONCLUSIONS

The classification may be applied uniformly to all skull base surgical approaches including lateral microsurgical and ventral endoscopic approaches, obviating the need for 2 separate classification systems. The classification allows extrapolation of relevant clinical information because each named segment may indicate potential surgical risk to specific structures.

Bypass of the maxillary artery to proximal middle cerebral artery

OBJECTIVE

The objective of this work was to explore the feasibility of bypass between the maxillary artery (MA) and proximity of middle cerebral artery (MCA).

METHODS

Ten fixed and perfused adult cadaver heads were dissected bilaterally, 20 sides in total. The superficial temporal artery and its 2 branches were dissected, and outer diameters were measured. The MA and its branch were exposed as well as deep temporal artery; outer diameter of MA was measured. The lengths between the external carotid artery, internal carotid artery, maxillary artery, and proximal middle cerebral artery were measured. Ten healthy adults as targets (20 sides), inner diameter and blood flow dynamic parameters of the common carotid artery, external carotid artery, internal carotid artery, maxillary artery, superficial temporal artery, and its 2 branches were done with ultrasound examination.

RESULTS

The mean outer diameter of MA (2.60 ± 0.20 mm) was larger than that of the temporal artery trunk (1.70 ± 0.30 mm). The mean lengths of graft vessels between the internal carotid artery, external carotid artery, and the bifurcation section of MCA (171.00 ± 2.70 and 162.40 ± 2.60 mm) were longer than the mean lengths of graft vessels between MA and MCA bifurcation section (61.70 ± 1.50 mm). In adults, the mean blood flow of the second part of MA (62.70 ± 13.30 mL/min) was more than that of the 2 branches of the superficial temporal artery (15.90 ± 3.70 mL/min and 17.70 ± 4.10 ml/min).

CONCLUSION

Bypass between the maxillary artery and proximity of middle cerebral artery is feasible. It is a kind of effective high flow bypass with which the graft vessel is shorter and straighter than the bypass between internal carotid artery or external carotid artery and proximity of middle cerebral artery.

Usefulness of continuous suture using short-thread double-armed micro-suture for cerebral vascular anastomosis

Background:

When microvascular anastomosis is performed in a deep, narrow operating field, securing space to throw knots is difficult. To simplify the procedure and avoid obstruction of the anastomosis, we use a continuous suturing with short-thread double-armed micro-suture.

Methods:

Sixty-four patients (38 cerebral revasculazation, 16 moyamoya disease, and 10 aneurysm surgery) undergoing microvaucular anastomosis were included. During anastomosis, a continuous suture was placed with short-thread double-armed micro-suture.

Results:

During 64 microanastomosis procedures, 64 consecutive continuous sutures were performed with 1-year follow up. All patients showed patency of anastomosis with long-term follow up.

Conclusions:

This technique is especially useful for anastomosis in a deep, narrow surgical field, such as in superior cerebellar artery anastomosis.

Multimodality treatment of complex unruptured cavernous and paraclinoid aneurysms

BACKGROUND

Unruptured aneurysms of the cavernous and paraclinoid internal carotid artery can be approached via microsurgical and endovascular approaches. Trends in treatment reflect a steady shift toward endovascular techniques.

OBJECTIVE

To analyze our results with multimodal treatment.

METHODS

We reviewed patients with unruptured cavernous and paraclinoid internal carotid artery aneurysms proximal to the posterior communicating artery treated at a single center from 2007 to 2012. Treatment included 4 groups: (1) stent-assisted coiling, (2) pipeline endovascular device (PED) flow diverter, (3) clipping, and (4) trapping/bypass. Follow-up was 2 to 60 months.

RESULTS

The 109 aneurysms in 102 patients were studied with the following treatment groupings: 41 were done with stent-assisted coiling, 24 with Pipeline endovascular device, 24 by microsurgical clipping, and 20 by trap/bypass. Group: (1) two percent had delayed significant intraparenchymal hemorrhage; (2) thirteen percent had central nerve palsies, 8% had small asymptomatic infarcts, and 4% had small, asymptomatic remote-site hemorrhages; (3) twenty-nine percent of patients suffered from transient central nerve palsies, 4% experienced major stroke, and 8% had small intracerebral hemorrhages; (4) thirty-five percent had transient central nerve palsies, 10% had strokes, and 10% had intracerebral hemorrhages. In terms of follow-up obliteration, 83% had complete/nearly complete obliteration at last follow-up, 17% had residual aneurysms, and 10% required retreatment. Ninety-six percent of group 1 (35/38), 100% of group 2 (23/23), 100% of group 3 (21/21), and 95% of group 4 had modified Rankin Scale scores of 0 to 1.

CONCLUSION

Treatment of these aneurysms can be carried out with acceptable rates of morbidity. Careful patient selection is crucial for optimal outcome. Endovascular treatment volumes likely will continue to predominate over microsurgical techniques as changing skill sets evolve in neurosurgery, but individualized application of all available treatment options will continue.

Pediatric bypasses for aneurysms and skull base tumors: short- and long-term outcomes

OBJECT

Cerebral bypass is a useful microsurgical technique for the treatment of unclippable aneurysms and invasive skull base tumors. The authors present the largest reported series of cerebrovascular bypasses in the pediatric population. They describe the short- and long-term clinical and radiographic outcomes of extracranial-intracranial and local bypasses performed for complex cerebral aneurysms and recurrent, invasive, and malignant skull base tumors in pediatric patients.

METHODS

A consecutive series of 17 pediatric patients who underwent revascularization were analyzed retrospectively for indications, graft patency, and neurological outcomes.

RESULTS

The mean age was 12 years (median 11 years, range 4-17 years), and there were 7 boys (41%) and 10 girls (59%). A total of 18 bypasses were performed in 17 patients and included 10 aneurysm cases (55.5%) and 8 tumor cases (45%). Of these 18 bypasses, there were 11 (61.1%) extracranial-intracranial bypasses (10 saphenous vein grafts [90%] and 1 radial artery graft [10%]), 1 side-to-side anastomosis (5.5%), 2 intracranial reimplants (11.1%), and 4 interposition bypass grafts (22.2%; 2 radial artery grafts, 1 saphenous vein graft, and 1 lingual artery graft). The mean clinical follow-up was 40.5 months (median 24 months, range 3-197 months). The mean radiographic follow-up was 40 months (median 15 months, range 9-197 months). Eighty-two percent of patients (14 of 17) achieved a modified Rankin Scale score between 0 and 2; however, 2 patients died of disease progression during long-term follow-up. The short-term (0- to 3-month) graft patency rate was 100%. Two patients had graft stenosis (11.7%) and underwent graft revisions. Two patients (11.1%) with giant middle cerebral artery aneurysms (> 25 mm) had strokes postoperatively but recovered without a persistent neurological deficit. One patient observed for 197 months showed a stable dysplastic change at the end of the graft. The long-term graft patency was 100% with a mean follow-up of 40 months. There were 2 deaths in the cohort during follow-up; both patients died of malignant tumors (osteogenic sarcoma and chondrosarcoma).

CONCLUSIONS

The authors conclude that in properly selected cases, bypasses can be safely performed in patients with aneurysms and skull base tumors. The bypasses remained patent over long periods of time despite the growth of the patients.

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.

Endovascular stenting of an extracranial-intracranial saphenous vein high-flow bypass graft: Technical case report

Background:

The authors describe a case of endovascular stenting of an extracranial–intracranial saphenous vein high-flow bypass graft in the management of a complex bilateral carotid aneurysm case.

Case Description:

A 43-year-old woman was admitted with progressive visual field restriction and headache. Imaging studies revealed bilateral supraclinoid carotid aneurysms. The right carotid aneurysm was clipped and the left one was treated by an endovascular procedure, after performing an internal carotid artery–middle cerebral artery (ICA-MCA) saphenous vein bypass graft. A few months following the bypass procedure, a 70–80% stenosis of the graft was discovered and treated endovascularly with a stenting procedure. Follow-up at 36 months after the first operation showed the patency of the venous graft and no neurological deficits.

Conclusions:

Endovascular stenting of the extracranial–intracranial saphenous vein high-flow bypass graft is technically feasible when postoperative graft occlusion is discovered.

The evolution of cerebral revascularization surgery

Among the relatively few surgeons to be awarded the Nobel Prize was Alexis Carrel, a French surgeon and pioneer in revascularization surgery at the turn of the 20th century. The authors trace the humble beginnings of cerebral revascularization surgery through to the major developments that helped shape the modern practice of cerebral bypass surgery. They discuss the cornerstone studies in the development of this technique, including the Extracranial/Intracranial Bypass Study initiated in 1977. Recent innovations, including modern techniques to monitor cerebral blood flow, microanastomosis techniques, and ongoing trials that play an important role in the evolution of this field are also evaluated.

Extracranial-intracranial bypass to reduce the risk of ischemic stroke in intracranial aneurysms of the anterior cerebral circulation: a systematic review

BACKGROUND AND PURPOSE

If clip application or coil placement for treatment of intracranial (IC) aneurysms is not feasible, the parent vessel can be occluded to induce thrombosis of the aneurysm. In the case that such an occlusion cannot be tolerated without subsequent sequel, the additional construction of an extracranial (EC)-IC bypass is needed for sufficient ipsilateral revascularization. Hitherto, the effectiveness of this combined treatment option was not investigated in a controlled randomized trial or in a review. The aim of the current report was to analyze clinical effectiveness of EC-IC bypass for cerebral revascularization in patients with Hunterian ligation in case of otherwise untreatable aneurysm of the anterior cerebral circulation. Special reference was given to different hemodynamic subgroups.

METHODS

A computerized database search was conducted from November 1985 to November 2002 using MEDLINE, relevant Internet sources, and full-text journal articles using appropriate indexed terms. Journal of Neurosurgery, Neurosurgery, Acta Neurochirurgica, and Stroke were manually searched for the period November 1985 to November 2002 and checked reference lists of all relevant articles for additional eligible studies. Language restriction was done for English, French, and German. Reports dealing with EC-IC bypass surgery for cerebral revascularization in case of aneurysm of the anterior cerebral circulation were reviewed when appropriate. Studies were included that contained evaluable data on clinical state, preoperative and postoperative hemodynamic state, surgical outcome, and follow-up. A statistical analysis was performed for different outcome parameters and clinical effectiveness in the included studies.

RESULTS

Overall, 20 studies were included, each with a study quality of 0-1. The postoperative outcome related to death or stroke depended mainly on preoperative hemodynamic subgroups (cerebral blood flow [CBF]/cerebral blood volume [CBV]; oxygen extraction fraction [OEF]). The final functional status was worse the more CBF/CBV ratio and OEF increased. Perioperative risk for death (0.8%) or stroke (1.5%) during the first month after operation was similar to the death or stroke rate during the following 2 to 12 months after operation. Neurologic function was improved over the preoperative state in 74% of the patients and was unchanged in 9%. The modified Rankin scale score was postoperatively 0 to 1 in 81% and 2 in 6% of the patients. Long-term patency was excellent, with 2.3% failure rate per year after the first year after surgery. There was no de novo aneurysm formation in the follow-up.

CONCLUSION

Neurologic function and subsequent stroke attributable to hemodynamic insufficiency in patients with otherwise untreatable IC aneurysm improves significantly by EC-IC bypass surgery if the brain area corresponding to the impaired neurologic function remains viable. The hemodynamic parameters observed for patients who experience improved neurologic function or diminished stroke risk profile after EC-IC bypass surgery contain both significantly elevated OEF and CBF/CBV. Therefore, hemodynamic state represents an important indicator for EC-IC bypass surgery. The large amount of data leads to narrow stroke with no significant heterogeneity, and the overall results are, therefore, likely to be statistically robust.

Cerebral revascularization for ischemia, aneurysms, and cranial base tumors

This article extensively reviews the history, indications for bypass, choice of grafts, techniques, complications, and results after cerebral revascularization. The current role and future perspectives of cerebral revascularization are discussed. The results of 295 direct revascularization procedures in 285 patients (130 tumors and 115 aneurysms from 1988 to 2006; 40 cases of ischemia from 1994 to 2006) and 26 pial synangiosis procedures (for moyamoya syndrome in children from 1997 to 2007) have been summarized. Current operative techniques are illustrated with drawings and video clips.

How to set up a microsurgical laboratory on small animal models: organization, techniques, and impact on residency training

Microsurgical training is mandatory for the optimal education of modern neurosurgeons. Even though this is a widely acknowledged statement and a lot of institutions around the world practice training in laboratory, the recent literature lacks tip and tricks on how to start a laboratory from scratch, what would be a convenient anesthesia, and what kind of exercises are appropriate. We present our experience in 16 microsurgical training courses settled up at our institutions. Two hundred eleven rodents were dissected. We will describe the organization of the laboratory and of the training courses and we will discuss its practical impact on the residency program.

Self-closing surgical clips for use in pericallosal artery–pericallosal artery side-to-side bypass

The authors demonstrate the feasibility of a new procedure to create intracranial interrupted microvascular anastomosis. Self-closing nitinol surgical clips were used for a pericallosal artery–pericallosal artery side-to-side bypass in a 52-year-old man harboring an unruptured large aneurysm located on the right A2 segment. The outflow artery was found to arise from the dome of the aneurysm, which was considered unsuitable for stand-alone clip ligation or coil occlusion. After bypass patency was intraoperatively confirmed using near-infrared indocyanine green videoangiography, the aneurysm and feeding artery were embolized with coils and safely occluded. Both postoperative courses were uneventful. The patient was discharged neurologically intact on the 5th postembolization day. Postprocedure angiography demonstrated no ipsilateral aneurysm filling and excellent bilateral distal outflow from the left anterior cerebral artery.

Cerebral bypass surgery for skull base lesions: technical notes incorporating lessons learned over two decades

Object

Despite advancements in endovascular neurosurgery, there remains an important role for cerebral bypass surgery in the treatment of skull base lesions. The authors describe their replacement cerebral bypass surgery techniques incorporating lessons learned over 2 decades.

Methods

The authors performed a retrospective review of cerebral bypass surgery performed by the senior author for skull base lesions between 1986 and 2006. One hundred patients had adjunct bypass surgery for skull base lesions.

Results

The bypass surgeries performed are conceptually divided into Skull Base Bypass I, II, and III. The majority of lesions requiring bypass surgery were giant cavernous carotid artery aneurysms or skull base meningiomas. There were no deaths in this case series. There was a 7% morbidity rate.

Conclusions

The ability to perform this surgery is an important adjunct in the armamentarium of skull base/cerebrovascular neurosurgeons.

Emergency extra-intracranial bypass surgery in the treatment of cerebral aneurysms

The need of an emergency bypass in hazardous situations during treatment of intracranial aneurysms has rarely been addressed in the literature. We report our 10 year experience with emergency bypass for aneurysm treatment. We retrospectively analyzed the data of patients who underwent emergency bypass surgery for the treatment of an intracranial aneurysm and compared the results with patients treated with bypass as a planned procedure during the same time period. Three groups were formed: group I, emergency bypass during clipping procedure; group II, emergency bypass for therapy refractory vasospasm; group III, planned bypass surgery. Sixteen patients (35%) out of 46 were treated with emergency bypass. In group I (11 patients) mortality was 37% and a good outcome (GOS 4 & 5) was achieved in 36%. In group II (5 patients) mortality was 20% and good outcome was reached in 60%. In group III (30 patients) mortality was 10% and good outcome was achieved in 86.6%. Outcome was worse in patients with additional SAH. An emergency bypass procedure as part of the aneurysm treatment should be considered in risky situations. Accurate timely decision-making is crucial combined with a fast and secure bypass technique. Treatment of refractory vasospasm with emergency bypasses may help to improve outcome in selected patients.

Increasing exposure of the petrous internal carotid artery for revascularization using the transzygomatic extended middle fossa approach: a cadaveric morphometric study

OBJECTIVE

When internal carotid artery (ICA) sacrifice is planned in the management of difficult tumors or aneurysms at the cranial base, the petrous ICA may be a useful site for anastomosis for interpositional vascular bypass. However, exposure of the artery and performing an anastomosis in this region may be technically challenging because of the narrow working corridor. The authors describe a transzygomatic extended middle fossa approach that maximizes the exposure of the petrous ICA for performing the difficult anastomosis.

METHODS

Bilateral dissections were performed on eight silicone-injected cadaveric head specimens. Exposure of the entire petrous ICA (horizontal segment, genu, and vertical segment) using the transzygomatic extended middle fossa approach was performed by the following steps. A frontotemporal craniotomy was performed followed by a zygomatic osteotomy. The temporal lobe dura was elevated extradurally to expose the posterior cavernous sinus and floor of the middle fossa. The middle fossa rhomboid was identified, which is bordered by V3 anteriorly, the GSPN laterally, the arcuate eminence posteriorly, and the petrous edge medially. Bone drilling was performed in the middle fossa rhomboid and Glasscock's triangle with care not to violate the cochlea. The horizontal and vertical segments of the petrous ICA were skeletonized entirely and mobilized from carotid canal. The V3 segment of the trigeminal nerve was retracted anteriorly to obtain more distal exposure of the ICA. An osteoplastic bone flap of the middle fossa floor lateral to the ICA was removed to increase the working space. A morphometric analysis was performed, quantifying the petrous ICA exposure, the surgical working corridor, and the angles of exposure.

RESULTS

On average, the length of the horizontal petrous ICA exposed was 9.2 +/- 1.0 mm (range, 8.0-11.0 mm). Anterior retraction of V3 provided an additional 4.3 +/- 0.4 mm of carotid exposure (46.7% increase; P < 0.05). The length of the genu was on average 3.6 +/- 0.4 mm (range, 3.0-4.0 mm), and the length of the vertical segment of the petrous ICA was 13.1 +/- 2.0 mm (range, 10.0-15.0 mm). The average depth of the petrous ICA from the outer surface of the temporal bone was 30.6 +/- 1.1 mm (range, 30.0-33.0 mm) at the V3-ICA junction and 27.2 +/- 0.7 mm (range, 26.0-28.0 mm) at the ICA genu. The average diameter of the inner working corridor was 24.2 +/- 3.0 mm (range, 21.5-30.0 mm). Removal of the zygoma increased the outer working corridor from an average distance of 24.4 +/- 3.8 mm to 33.4 +/- 3.4 mm (36.9% increase in exposure; P < 0.05). The average angle of exposure was 66.5% greater (P < 0.05) with zygomatic arch removal (39.3 +/- 4.9 degrees) than without zygomatic arch removal (23.6 +/- 2.7 degrees).

CONCLUSION

The transzygomatic extended middle fossa approach provides a wide surgical corridor for maximal exposure of the petrous ICA with minimized temporal lobe retraction. This large exposure facilitates vascular anastomoses at the petrous ICA and provides working room to maneuver instruments. The middle fossa rhomboid is a key landmark to identify the petrous ICA and to avoid neuro-otologic structures.

SELF-CLOSING U-CLIPS FOR INTRACRANIAL MICROANASTOMOSES IN HIGH-FLOW ARTERIAL BYPASS

OBJECTIVE

Self-closing nitinol U-clips (Medtronic, Inc., Minneapolis, MN) have been used to create vascular microanastomoses by vascular surgeons. This device eliminates the need for suture management and knot tying. Therefore, a high-quality interrupted microvascular anastomosis can be obtained in a shorter period of time. This is the first report of a U-clip intracranial arterial microanastomosis for a high-flow extracranial-intracranial bypass using a radial artery graft.

CLINICAL PRESENTATION

A 24-year-old woman with a history of chronic headache was admitted to the National Neurological Institute Carlo Besta after a brain computed tomographic scan revealed a giant serpentine aneurysm of her right middle cerebral artery. Magnetic resonance angiography and four-vessel angiography confirmed the diagnosis and ruled out other lesions.

INTERVENTION

A radial artery graft was used to create a high-flow bypass between the external carotid artery and the postaneurysmal M2 segment of the right middle cerebral artery. Nitinol self-closing U-clips were used for the interrupted intracranial microanastomosis. After intraoperative near-infrared indocyanine green video angiography confirmed the bypass patency, the aneurysm could be trapped.

CONCLUSION

The postoperative course was uneventful. The patient was discharged on the seventh postoperative day and was neurologically intact. Postoperative angiography documented the successful exclusion of the aneurysm and the presence of revascularization of the distal branches of the right middle cerebral artery through the bypass. This case demonstrates the efficacy of U-clips for intracranial microanastomoses.

Extracranial-intracranial bypass for the treatment of cavernous sinus aneurysms

The optimal management of symptomatic cavernous sinus aneurysms remains controversial. Carotid occlusion is a simple procedure, but carries an ongoing risk of early and late stroke. Cerebral revascularisation is technically demanding and carries a risk of morbidity and mortality of around 10%. Eight patients treated with an extracranial-intracranial vascular bypass graft over a period of 44 months for symptomatic cavernous sinus aneurysms are reviewed. At a mean follow-up of 20 months, seven patients (87.5%) had an excellent outcome (Glasgow Outcome Score 5) while one patient suffered a perioperative stroke. In only one case, where the radial artery had been used, the graft became occluded. The results of this series seem to indicate that cerebral revascularisation is an effective treatment for patients with symptomatic cavernous sinus aneurysms.

Submandibular-Infratemporal Interpositional Carotid Artery Bypass for Cranial Base Tumors and Giant Aneurysms

OBJECTIVE:

Cerebral revascularization is an important strategy in the surgical management of some complex cranial base tumors and unclippable aneurysms. A high-flow bypass may be necessary in planned carotid occlusion or sacrifice. The cervical-to-supraclinoid internal carotid artery bypass or cervical carotid-to-middle cerebral artery bypass are useful procedures to bypass lesions at the base of the cranium. We describe technical modifications of the submandibular-infratemporal interpositional saphenous vein (or radial artery) graft bypass technique specifically designed to avoid removal of the zygoma.

METHODS:

The saphenous vein or radial artery interpositional graft is tunneled through a burr hole created in the floor of the middle fossa via a submandibular-infratemporal route avoiding removal of zygoma and attachments of the masseter or temporalis muscles.

RESULTS:

The technique is demonstrated in one patient with removal of a malignant cavernous sinus tumor and in another patient with an unclippable giant carotid bifurcation aneurysm.

CONCLUSION:

The advantages of this approach include preservation of the facial anatomy and creation of a short and safe route for passage of the saphenous vein or radial artery graft.

Microsurgical anatomy and approaches to the cavernous sinus

OBJECTIVE

The aim of this article is to describe the anatomy of the cavernous sinus and to provide a guide for use when performing surgery in this complex area. Clinical cases are used to illustrate routes to the cavernous sinus and its contents and to demonstrate how the cavernous sinus can be used as a pathway for exposure of deeper structures.

METHODS

Thirty cadaveric cavernous sinuses were examined using x3 to x40 magnification after the arteries and veins were injected with colored silicone. Distances between the entrance of the oculomotor and trochlear nerves and the posterior clinoid process were recorded. Stepwise dissections of the cavernous sinuses, performed to demonstrate the intradural and extradural routes, are accompanied by intraoperative photographs of those approaches.

RESULTS

The anatomy of the cavernous sinus is complex because of the high density of critically important neural and vascular structures. Selective cases demonstrate how a detailed knowledge of cavernous sinus anatomy can provide for safer surgery with low morbidity.

CONCLUSION

A precise understanding of the bony relationships and neurovascular contents of the cavernous sinus, together with the use of cranial base and microsurgical techniques, has allowed neurosurgeons to approach the cavernous sinus with reduced morbidity and mortality, changing the natural history of selected lesions in this region. Complete resection of cavernous sinus meningiomas has proven to be difficult and, in many cases, impossible without causing significant morbidity. However, surgical reduction of such lesions enhances the chances for success of subsequent therapy.

Dumbbell-shaped middle cranial fossa meningioma with interdural cavernous sinus extension: report of two cases with complete removal

BACKGROUND

Surgery for meningiomas involving the cavernous sinus remains controversial. Interdural cavernous sinus is called the lateral dural wall in the cavernous sinus, which is composed of two layers, the outer dural layer and the inner membranous layer. We encountered two cases of dumbbell-shaped middle cranial fossa meningioma with interdural cavernous sinus extension, which were successfully removed by surgical means.

CASE DESCRIPTION

A 57-year-old woman presented with headache and decreased visual acuity. Neurological assessment was normal. Computed tomography and magnetic resonance imaging showed the presence of a dumbbell-shaped, smooth-contoured, well-enhanced mass in the right mesial temporal area. The lateral wall of the cavernous sinus was exposed via frontotemporal craniotomy and the tumor originating in the lateral wall was totally removed. A 41-year-old man presented with seizure attacks and drowsy mental status. Magnetic resonance imaging showed the presence of a multilobulated, well-enhanced mass in the left parasellar area. The tumor was totally resected via a transsylvian temporopolar approach. The mass originated from tentorial edge and extended into the cavernous sinus by dural penetration.

CONCLUSION

Middle cranial fossa meningioma with interdural cavernous sinus extension can be removed more easily than other tumors with intracavernous sinus extension and, consequently, can be safely resected without any resulting cranial nerve deficit.

Long term evaluation of brain perfusion with magnetic resonance in high flow extracranial-intracranial saphenous graft bypass

Assessment was made of the cerebral vascular haemodynamic parameters in patients with a high-flow extra-intracranial (EC-IC) bypass performed for therapeutic occlusion of the internal carotid artery (ICA). Sixteen patients with ICA occlusion and EC-IC bypass (time interval from surgery 1-6 years) underwent MRI. Perfusion-weighted magnetic resonance imaging (PW-MRI) sequences were performed without the use of an arterial input function. The relative cerebral blood volume (rCBV), mean transit time (MTT) and relative cerebral blood flow (rCBF) were evaluated in all patients at the level of the basal ganglia, centrum semiovale and cortex in both hemispheres. Statistically significant differences (P<0.005) were observed in the haemodynamic parameters, indicating increased rCBV in the basal ganglia and decreased rCBF and rCBV in the cortex of the hemisphere supplied by the graft with respect to the contralateral. Patients with occlusion of the ICA and high flow EC-IC bypass do have altered vascular haemodynamic status between the hemispheres. In particular, rCBF is impaired in the surgical hemisphere at the level of the cortex. These patients should be followed-up to rule out chronic ischemia.

Double Reimplantation Technique to Reconstruct Arterial Bifurcations with Giant Aneurysms

Objective:

To introduce the double implantation technique, a variation of standard radial artery or saphenous vein bypass that can be used to reconstruct arterial bifurcations in the management of giant aneurysms with complex branch arteries.

Methods:

This technique was applied in two patients with giant aneurysms. A 74-year-old woman presented with a ruptured thrombotic middle cerebral artery aneurysm, and a 24-year-old man presented with an enlarging infectious aneurysm of the distal anterior cerebral artery (ACA).

Results:

In the first case, a saphenous vein graft was anastomosed end-to-end to the external carotid artery. The temporal M2 middle cerebral artery trunk was disconnected from the aneurysm and reimplanted onto the graft with an end-to-side anastomosis. The graft was anastomosed end-to-side to the frontal M2 middle cerebral artery trunk, and the aneurysm was trapped. Similarly, in the second case, a radial artery graft was connected to a proximal ACA branch (anterior internal frontal artery) and to the distal pericallosal artery, with reimplantation of the callosomarginal artery onto the graft. The aneurysm was occluded proximally with a clip.

Conclusion:

The combination of two arterial reimplantations onto a bypass graft connected to a proximal donor artery (3 anastomoses overall) reconstructs an arterial bifurcation and enables the exclusion of a giant aneurysm. Ischemia times are minimized by completing the proximal anastomosis first, successively reimplanting efferent arterial trunks distally, and restoring cerebral perfusion to reimplanted arteries while other anastomoses are performed. This technique may be indicated when critical efferent arteries require revascularization, conventional donor arteries are diminutive, the aneurysm has ruptured, or intraluminal thrombus requires debulking.

Revascularization with saphenous vein bypasses for complex intracranial aneurysms

Most intracranial aneurysms can be managed with either microsurgical clipping or endovascular coiling. A subset of complex aneurysms with aberrant anatomy or fusiform/dolichoectatic morphology may require revascularization as part of a strategy that occludes the aneurysm or parent artery or both. Bypass techniques have been invented to revascularize nearly every intracranial artery. An aneurysm that will require a saphenous vein bypass is one that cannot be treated with conventional microsurgical clipping or endovascular coiling and also requires deliberate sacrifice of a major intracranial artery as part of the alternative treatment strategy. In the past 7 years the senior author (MTL) has performed a total of 110 bypasses, of which 46 were for aneurysms. Twenty-two of these patients received high-flow extracranial-to-intracranial bypasses using saphenous vein grafts, of which 16 had aneurysms that were giant in size. We review the indications for saphenous vein bypasses for complex intracranial aneurysms, surgical techniques, and clinical management strategies.

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.

Graft harvesting for revascularization in the head and neck

The techniques for revascularization in the neurocranium, skull base, and neck continue to evolve at an exciting pace. In this body of literature, however, techniques for harvesting radial artery and saphenous vein grafts are mainly reported using traditional open techniques. Minimally invasive procedures are fast becoming an alternative to open techniques in many fields and have the potential to become the standard of care. The cardiovascular literature is replete with reports of endoscopically harvested vascular grafts. This article reviews both methods, since the current state of the art involves knowledge of open and endoscopic harvesting techniques.

Extracranial-to-intracranial bypass using radial artery grafting for complex skull base tumors: technical note

The management of complex skull base tumors that incorporate large intracranial vessels poses challenging questions. Patients who fail initial surgical resection and adjunctive therapies (i.e., radiosurgery) who present with tumor regrowth may be candidates for parent vessel occlusion and total tumor resection in combination with extracranial-to-intracranial (EC-IC) bypass to augment the sacrificed vessel territory. In this technical report, we delineate the surgical technique of performing an EC-IC bypass using a radial artery graft. Our protocol of simultaneous cranial, neck, and forearm dissections by the surgical team to perform this procedure is described in detail.

Superficial temporal artery graft for bypass of the maxillary to proximal middle cerebral artery using a transantral approach: an anatomical and technical study

CONCLUSION

Using a transantral approach, we examined a new bypass of the maxillary artery (MA) to proximal middle cerebral artery (MCA). The caliber of the MA was suitable to provide sufficient blood flow. The length of the graft was shorter and it had a straighter course in the new technique than in previously described techniques.

OBJECTIVE

To examine a new bypass of the MA to proximal MCA using a transantral approach as an alternative to other forms of anterior circulation bypass surgery.

MATERIAL AND METHODS

The method was applied to five adult cadavers bilaterally. The MA and its branches were easily found after removal of the posterior sinus wall using a transantral approach. Then, a hole was created in the sphenoid bone 5-6 mm lateral to the posteroinferior edge of the superior orbital fissure extradurally. After the carotid and sylvian cisternae had been opened, the M2 segment of the MCA was exposed. The MA was transected just before the origin of the descending palatine artery branch. After opening the dura over the hole, the MA was passed through the hole to reach the intracranial cavity. The proximal side of the superficial temporal artery graft was anastomosed end-to-end with the MA and the distal side was anastomosed end-to-side with the M2 segment of the MCA.

RESULTS

The mean caliber of the MA was 2.4+/-0.3 mm before the origin of the descending palatine artery branch. The mean caliber of the largest trunk of the M2 segment of the MCA was 2.3+/-0.3 mm. The average length of the graft was 24+/-3 mm.

Use of side branch in saphenous vein interposition graft for high-flow EC/IC bypass procedures

✓ Saphenous vein (SV) interposition grafts are often used for high-flow extracranial—intracranial bypass procedures. During these procedures, it is essential to remove air and debris from the graft and to evaluate blood flow through the graft after it has been anastomosed to other cortical vessels.

In this paper, the authors describe the preservation of a large side branch on the proximal end of the SV. This side branch can be used to flush out air and debris from the graft and to evaluate blood flow during revascularization.