Bypass using V2-V3 segment of the vertebral artery as donor or recipient: technical nuances and results

Efficacy and Safety of Extracranial-Intracranial Bypass Surgery for Posterior Circulation Aneurysms: A Systematic Review and Single-Arm Meta-Analysis

OBJECTIVE

Treating complex posterior circulation aneurysms poses challenges, and extracranial to intracranial (EC-IC) bypass techniques are potential therapeutic options. However, the safety and efficacy of this approach for posterior circulation aneurysms remain unclear. The study's objective was to assess the safety and efficacy of EC-IC bypass in these aneurysms.

METHODS

Adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we conducted a systematic review on EC-IC revascularization for posterior circulation aneurysms. Included studies had at least 4 patients and reported data on mortality, patency, complications, or clinical outcomes. Favorable clinical outcomes were defined as modified Rankin Scale below 3 or Glasgow Outcome Scale above 3, and complications were any issues related to the bypass procedure.

RESULTS

From 3036 articles reviewed, 22 studies involving 196 patients who underwent 210 EC-IC bypass procedures for posterior circulation aneurysms were selected. The median follow-up period of 14 studies was 31.66 months (6-61 months). Final follow-up indicated a high bypass patency rate of 96% [95% confidence interval [CI]: 91%-100%; I2 = 12%], with a mortality rate of 5% [95% CI: 1%-9%; I2 = 0%]. Additionally, 83% [95% CI: 70%-96%; I2 = 77%] of patients showed good outcomes at the last follow-up. Complications were observed in 40% [95% CI: 26%-55%; I2 = 80%]. Heterogeneity was associated with specific studies.

CONCLUSIONS

EC-IC bypass procedures are a viable treatment option for posterior circulation aneurysms, with high bypass patency rates and favorable clinical outcomes. However, complications, especially neurological deficits, exist. Open revascularization remains essential for neurovascular surgeons dealing with complex aneurysms.

Vertebral Artery to Middle Cerebral Artery Bypass for Flow Augmentation

BACKGROUND AND IMPORTANCE

Extracranial-intracranial bypass remains an enduring procedure for a select group of patients suffering from steno-occlusive cerebrovascular disease. Although the superficial temporal artery (STA) to middle cerebral artery (MCA) bypass is most familiar among neurosurgeons, particular circumstances preclude the use of an STA donor. In such cases, alternative revascularization strategies must be pursued.

CLINICAL PRESENTATION

A 63-year-old female presented with symptoms of hemodynamic insufficiency and was found to have left common carotid artery occlusion at the origin. She experienced progressive watershed ischemia and pressure-dependent fluctuations in her neurological examination despite maximum medical therapy. The ipsilateral STA was unsuitable for use as a donor vessel. We performed an extracranial vertebral artery (VA) to MCA bypass with a radial artery interposition graft.

CONCLUSION

This technical case description and accompanying surgical video review the relevant anatomy and surgical technique for a VA-MCA bypass. The patient was ultimately discharged home at her preoperative neurological baseline with patency of the bypass. The VA can serve as a useful donor vessel for cerebral revascularization procedures in pathologies ranging from malignancies of the head and neck to cerebral aneurysms and cerebrovascular steno-occlusive disease.

Alternative Bypass Technique Using Radial Artery Graft between V3 Segment of Vertebral Artery and Middle Cerebral Artery: Technical Note

BACKGROUND

 There are some cases where a radial artery (RA) graft is needed for a high-flow extracranial to intracranial (EC-IC) bypass as the external carotid artery (ECA) cannot be utilized as a donor artery. In this report, we describe two cases of extracranial vertebral artery (VA) to middle cerebral artery (MCA) high-flow bypass using an RA graft with an artificial vessel as an alternative bypass technique.

METHODS

 The patient was placed supine with a head rotation of 80 degrees. After frontotemporal craniotomy, another C: -shaped skin incision was made at the retroauricular region and the V3 portion of the VA was exposed at the suboccipital triangle. Prior to attempting the high-flow bypass, the superficial temporal artery (STA) was anastomosed to the M4 portion of the MCA as an insurance bypass. The RA graft was anastomosed to the V3 portion of the VA that traveled under the periosteum at the supra-auricular region through an artificial vessel. After RA-M2 anastomosis, an alternative EC-IC bypass, the V3-RA-M2 bypass, was achieved.

RESULTS

 Postoperative angiography demonstrated successful graft patency and no perioperative complications were observed in both cases.

CONCLUSIONS

 In the cases where a high-flow bypass is required, the V3 portion of the VA is a suitable alternative proximal anastomosis site when the ECA is not a candidate donor. Furthermore, an artificial vessel shows satisfactory protection against graft complications.

Vascular reconstruction related to the extracranial vertebral artery: the presentation of the concept and the basis for the establishment of the bypass system

The intracranial vertebrobasilar artery system has a unique hemodynamic pattern (vessel trunk converged bilateral flow with three groups of perforators directly arising from it), is embedded within intense osseous constraints, and is located far from conventional donor vessels. Two major traditional modalities of posterior circulation revascularization encompass the superficial temporal artery to the superior cerebellar artery and the occipital artery to the posteroinferior cerebellar artery anastomosis, which are extracranial-intracranial low-flow bypass with donor arteries belonging to the anterior circulation and mainly supply focal perforators and distal vascular territories. As our understanding of flow hemodynamics has improved, the extracranial vertebral artery-related bypass has further evolved to improve the cerebral revascularization system. In this article, we propose the concept of "vascular reconstruction related to the extracranial vertebral artery" and review the design philosophy of the available innovative modalities in the respective segments. V1 transposition overcomes the issue of high rates of in-stent restenosis and provides a durable complementary alternative to endovascular treatment. V2 bypass serves as an extracranial communication pathway between the anterior and posterior circulation, providing the advantages of high-flow, short interposition grafts, orthograde flow in the vertebrobasilar system, and avoiding complex skull base manipulation. V3 bypass is characterized by profound and simultaneous vascular reconstruction of the posterior circulation, which is achieved by intracranial-intracranial or multiple bypasses in conjunction with skull base techniques. These posterior circulation vessels not only play a pivotal role in the bypass modalities designed for vertebrobasilar lesions but can also be implemented to revascularize the anterior circulation, thereby becoming a systematic methodology.

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.

Sequential Extradural Release of the V3 Vertebral Artery to Facilitate Intradural V4 Vertebral Artery Reanastomosis: Feasibility of a Novel Revascularization Technique

BACKGROUND

Revascularization of the intradural vertebral artery (VA) usually involves V3-V4 bypass using an interposition graft. The interposition of a graft increases surgical time, adds risks, and requires 2 suture lines.

OBJECTIVE

To assess the feasibility of an excision-reanastomosis of V4 by sequentially releasing V3.

METHODS

Twenty specimens were prepared for surgical simulation of a far-lateral approach. The third and fourth segments of the VA were exposed through the far-lateral approach bilaterally. The V3 segment was divided into three subsegments: (1) V3 f : from entry to C1 transverse foramen to the point of exit from C1 transverse foramen; (2) V3 s : from V3 f to the distal point of V3 within the sulcus arteriosus; and (3) V3 d : from point V3 leaves the sulcus arteriosus to its dural entrance. After transecting the VA 2 mm proximal to the posterior inferior cerebellar artery origin, each subsegment was released sequentially. We measured the lengths obtained before and after releasing each segment by pulling the VA along its main axis to recreate a V3-V4 excision-reanastomosis.

RESULTS

The V3 could not be effectively mobilized without release. When totally released, an average length of 13.15 mm was available for completing V3-V4 reanastomosis.

CONCLUSION

Complete release of V3 from all its adhesions in its extracranial course can provide an average length of 13.15 mm for excision-reanastomosis. The present study shows the anatomic feasibility of the use of V3 segment in primary anastomosis after excision of a diseased segment of the intradural VA, laying the basis for future clinical application.

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.

The subatlantic triangle: gateway to early localization of the atlantoaxial vertebral artery

OBJECTIVE Exposure of the vertebral artery (VA) between C-1 and C-2 vertebrae (atlantoaxial VA) may be necessary in a variety of pathologies of the craniovertebral junction. Current methods to expose this segment of the VA entail sharp dissection of muscles close to the internal jugular vein and the spinal accessory nerve. The present study assesses the technique of exposing the atlantoaxial VA through a newly defined muscular triangle at the craniovertebral junction. METHODS Five cadaveric heads were prepared for surgical simulation in prone position, turned 30°-45° toward the side of exposure. The atlantoaxial VA was exposed through the subatlantic triangle after reflecting the sternocleidomastoid and splenius capitis muscles inferiorly. The subatlantic triangle was formed by 3 groups of muscles: 1) the levator scapulae and splenius cervicis muscles inferiorly and laterally, 2) the longissimus capitis muscle inferiorly and medially, and 3) the inferior oblique capitis superiorly. The lengths of the VA exposed through the triangle before and after unroofing the C-2 transverse foramen were measured. RESULTS The subatlantic triangle consistently provided access to the whole length of atlantoaxial VA. The average length of the VA exposed via the subatlantic triangle was 19.5 mm. This average increased to 31.5 mm after the VA was released at the C-2 transverse foramen. CONCLUSIONS The subatlantic triangle provides a simple and straightforward pathway to expose the atlantoaxial VA. The proposed method may be useful during posterior approaches to the craniovertebral junction should early exposure and control of the atlantoaxial VA become necessary.

The V3 segment of the vertebral artery as a robust donor for intracranial-to-intracranial interpositional bypasses: technique and application in 5 patients

The V₃ segment of the vertebral artery (VA) has been studied in various clinical scenarios, such as in tumors of the craniovertebral junction and dissecting aneurysms. However, its use as a donor artery in cerebral revascularization procedures has not been extensively studied. In this report, the authors summarize their clinical experience in cerebral revascularization procedures using the V₃ segment as a donor. A brief anatomical description of the relevant techniques is also provided.

The Infrazygomatic Segment of the Superficial Temporal Artery: Anatomy and Technique for Harvesting a Better Interposition Graft

BACKGROUND

The superficial temporal artery (STA) is underutilized as an interposition graft because current techniques expose and harvest STA above the level of the zygoma. This technique yields a diminutive arterial segment in both length and diameter, which limits its use for extracranial-intracranial bypass.

OBJECTIVE

To introduce a safe and efficient technique for harvesting of the infrazygomatic segment of the STA.

METHODS

Scalp layers, STA, and the facial nerve were studied in 18 specimens. The length of the STA segment harvested below the superior border of the zygomatic arch was measured. Safety of this technique was assessed by measuring the distance between the facial nerve and the STA.

RESULTS

The galea and subgaleal fat pad were the only anatomical planes found between the facial nerve and the STA below the zygomatic arch. A dense subcutaneous band of galea contained the STA and allowed proximal dissection of the artery without exposing the facial nerve. The average length of the artery harvested between the zygomatic arch and the parotid gland was 20 mm.

CONCLUSION

Subcutaneous dissection within the galea below the level of the zygomatic arch and preservation of the dense subcutaneous band surrounding the STA avoids transecting the facial nerve branches while providing increased STA exposure. This anatomical knowledge may increase the use of STA as an interposition graft in cerebrovascular bypass procedures and reduce the need to harvest grafts through additional incisions at remote sites.

Early Localization of the Third Segment of the Vertebral Artery: The Atlanto-Mastoid Line

Supplemental Digital Content is Available in the Text.

BACKGROUND

The third segment of the vertebral artery (V3) is vulnerable to injury during surgical approaches to the posterolateral craniovertebral junction. Despite numerous efforts, a roadmap to localize this segment of the artery is still lacking.

OBJECTIVE

To delineate the topographic anatomy of the V3 and to facilitate a safe and fast exposure during transcranial surgical approaches to the posterior craniovertebral junction.

METHODS

The distances between the most posteriorly prominent point (bulge) of the vertebral artery and the surrounding bony and muscular landmarks were measured in 10 cadaveric heads bilaterally (20 sides). The relative position of the vertebral artery bulge projected on the atlanto-mastoid line was calculated using trigonometric equations. Two clinical vignettes were reported to provide examples of clinical application of the described technique.

RESULTS

The vertebral artery bulge was found within 10.8 mm of the atlanto-mastoid line. The projected position of the vertebral artery bulge on the atlanto-mastoid line lay within 40th and 50th percentiles of its length measured from the mastoid process in 16 (89%) specimens. The close relationship between the V3 segment and superior oblique capitis muscle makes this muscle another useful guide for localization of the V3 segment.

CONCLUSION

The atlanto-mastoid line is a reliable guide for fast and safe exposure of the vertebral artery in the suboccipital triangle. Using this clue together with the belly of the superior oblique capitis muscle can lead the surgeon to the V3 segment safely, as illustrated in the clinical vignettes.

Tailored PICA Revascularization for Unusual Ruptured Fusiform Vertebro-PICA Origin Aneurysms: Rationale and Case Illustrations

Ruptured fusiform aneurysms of the vertebral artery involving posterior inferior cerebellar artery (PICA) origin are difficult to manage without sacrificing PICA. In this report, two very unusual cases are described which highlight different revascularization strategies that may be required. The first case initially appeared to be a small saccular PICA origin aneurysm, but detailed angiography showed a serpentine recanalization of a fusiform aneurysm. This was treated with PICA-PICA anastomosis and trapping of the aneurysm. The second case is a dissecting vertebral aneurysm with both PICA and the anterior spinal artery originating from the dome. PICA was found to be a bihemispheric variant, so no in situ bypass was available, and an occipital artery to PICA bypass was performed. The vertebral artery was occluded proximally only and follow-up angiography showed remodeling of the distal vertebral artery with the anterior spinal artery filling by retrograde flow from the distal vertebral artery. These cases illustrate both the anatomic variability of this region as well as the need to be familiar with multiple treatment strategies including revascularization techniques to be able to successfully treat these aneurysms.