Revascularizing the upper basilar circulation with saphenous vein grafts: operative technique and lessons learned

Anatomical Assessment of the Temporopolar Artery for Revascularization of Deep Recipients

BACKGROUND

Intracranial-intracranial and extracranial-intracranial bypass options for revascularization of deep cerebral recipients are limited and technically demanding.

OBJECTIVE

To assess the anatomical feasibility of using the temporopolar artery (TPA) for revascularization of the anterior cerebral artery (ACA), posterior cerebral artery (PCA), and superior cerebellar arteries (SCA).

METHODS

Orbitozygomatic craniotomy was performed bilaterally on 8 cadaveric heads. The cisternal segment of the TPA was dissected. The TPA was cut at M3-M4 junction with its proximal and distal calibers and the length of the cisternal segment measured. Feasibility of the TPA-A1-ACA, TPA-A2-ACA, TPA-SCA, and TPA-PCA bypasses were assessed.

RESULTS

A total of 17 TPAs were identified in 16 specimens. The average distal TPA caliber was 1.0 ± 0.2 mm, and the average cisternal length was 37.5 ± 9.4 mm. TPA caliber was ≥ 1.0 mm in 12 specimens (70%). The TPA-A1-ACA bypass was feasible in all specimens, whereas the TPA reached the A2-ACA, SCA, and PCA in 94% of specimens (16/17). At the point of anastomosis, the average recipient caliber was 2.5 ± 0.5 mm for A1-ACA, and 2.3 ± 0.7 mm for A2-ACA. The calibers of the SCA and PCA at the anastomosis points were 2.0 ± 0.6 mm, and 2.7 ± 0.8 mm, respectively.

CONCLUSION

The TPA-ACA, TPA-PCA, and TPA-SCA bypasses are anatomically feasible and may be used when the distal caliber of the TPA stump is optimal to provide adequate blood flow. This study lays foundations for clinical use of the TPA for ACA revascularization in well-selected cases.

The Identification of Factors That Influence the Quality of Bypass Anastomosis and an Evaluation of the Usefulness of an Experimental Practical Scale in This Regard

BACKGROUND

Several factors associated with interrupted and continuous suturing techniques affect the quality of bypass anastomosis. It is difficult to determine the impact of these factors during surgery. The primary objective of this study was to evaluate factors with the potential to influence the quality of bypass anastomosis using either interrupted or continuous suturing. A secondary objective was to evaluate the usefulness of a practical scale when comparing interrupted and continuous suturing techniques to improve bypass anastomosis.

METHODS

Interrupted (n = 100) and continuous (n = 100) suturing techniques were used in 200 end-to-side bypasses to a depth of 3 cm and were assessed by 5 neurosurgeons.

RESULTS

Vessel closing time (P < 0.001), stitch distribution (P < 0.001), intima-intima attachment (P < 0.001), and size of the orifice (P < 0.001) had a significant impact on the quality of the bypass regardless of the suturing technique used. The suturing technique used (interrupted or continuous) and positioning of the recipient vessel (vertical or horizontal) did not significantly influence the quality of anastomosis. Using multivariate analysis, the highest statistical significance with regard to bypass quality was attributed to the large size of the orifice and intimal attachment.

CONCLUSIONS

There were advantages and disadvantages to both suturing techniques. The scale was a practical way to measure and improve performance.

Thrombectomy for late occlusion of high flow extracranial-intracranial saphenous vein bypass graft after 27 years of patency

High flow extracranial-intracranial (EC-IC) bypass with a saphenous vein graft (SVG) has been used for more than 40 years in patients with giant aneurysms of the posterior circulation refractory to medical management, and has demonstrated high long term patency rates. We report the case of a patient treated with external carotid artery (ECA)-posterior cerebral artery SVG bypass in 1989 who presented 27 years later with paresthesias and confusion, and was found to have partial occlusion of her SVG bypass graft and a basilar occlusion. She was treated with mechanical thrombectomy of the basilar occlusion via the partially thrombosed graft, the first report of such a procedure through a high flow posterior circulation EC-IC SVG, resulting in improvement of the patient's neurologic examination. At 27 years, this is the longest reported delay in thrombosis of a high flow SVG bypass graft, highlighting the long term patency of these grafts and the feasibility of thrombectomy through occluded bypass grafts.

Thrombectomy for late occlusion of high flow extracranial-intracranial saphenous vein bypass graft after 27 years of patency

High flow extracranial-intracranial (EC-IC) bypass with a saphenous vein graft (SVG) has been used for more than 40 years in patients with giant aneurysms of the posterior circulation refractory to medical management, and has demonstrated high long term patency rates. We report the case of a patient treated with external carotid artery (ECA)-posterior cerebral artery SVG bypass in 1989 who presented 27 years later with paresthesias and confusion, and was found to have partial occlusion of her SVG bypass graft and a basilar occlusion. She was treated with mechanical thrombectomy of the basilar occlusion via the partially thrombosed graft, the first report of such a procedure through a high flow posterior circulation EC-IC SVG, resulting in improvement of the patient's neurologic examination. At 27 years, this is the longest reported delay in thrombosis of a high flow SVG bypass graft, highlighting the long term patency of these grafts and the feasibility of thrombectomy through occluded bypass grafts.

Simple training tricks for mastering and taming bypass procedures in neurosurgery

Background:

Neurosurgeons devoted to bypass neurosurgery or revascularization neurosurgery are becoming scarcer. From a practical point of view, “bypass neurosurgeons” are anastomosis makers, vessels technicians, and time-racing repairers of vessel walls. This requires understanding the key features and hidden tricks of bypass surgery. The goal of this paper is to provide simple and inexpensive tricks for taming the art of bypass neurosurgery. Most of these tricks and materials described can be borrowed, donated, or purchased inexpensively.

Methods:

We performed a review of relevant training materials and recorded videos for training bypass procedures for 3 years between June 2014 and July 2017. In total, 1,300 training bypass procedures were performed, of which 200 procedures were chosen for this paper.

Results:

A training laboratory bypass procedures is required to enable a neurosurgeon to develop the necessary skills. The important skills for training bypass procedures gained through meticulous practice to be as reflexes are coordination, speed, agility, flexibility, and reaction time. Bypassing requires synchronization between the surgeon's gross movements, fine motoric skills, and mental strength. The suturing rhythm must be timed in a brain–body–hand fashion.

Conclusion:

Bypass-training is a critical part of neurosurgical training and not for a selected few. Diligent and meticulous training can enable every neurosurgeon to tame the art of bypass neurosurgery. This requires understanding the key features and hidden tricks of bypass surgery, as well as uncountable hours of training. In bypass neurosurgery, quality and time goes hand in hand.

Exposure of the External Carotid Artery Through the Posterior Triangle of the Neck: A Novel Approach to Facilitate Bypass Procedures to the Posterior Cerebral Circulation

BACKGROUND: The external carotid artery (ECA) is the main high-flow donor for extracranial–intracranial revascularization procedures. However, anatomic restraints limit the availability of ECA in posterior exposures of the craniocervical junction aimed for bypass to distal vertebral artery segments.

OBJECTIVE: To examine the feasibility and safety of exposure of the ECA through the posterior triangle of the neck.

METHODS: A preliminary feasibility study on the posterior neck exposure of the ECA was performed in 1 cadaveric head (2 sides) followed by a morphometric study on 9 cadaveric heads (18 sides). Through an extension of the muscular stage of the far-lateral approach, the fascial plane between the posterior belly of the digastric muscle and the capsule of the parotid gland was dissected inferior to the C1. Topographic anatomy of the exposed distal segment of the ECA was defined in detail, including bony landmarks and the facial nerve.

RESULTS: ECA was found successfully using the proposed technique in all specimens. In 90% of the specimens, ECA was exposed without transgression of the capsule of the parotid gland. The facial nerve was not encountered during the surgical exposures.

CONCLUSION: ECA can be safely and effectively exposed through the posterior triangle of the neck using the proposed approach. This method can facilitate extracranial–intracranial bypass procedures to V3/V4 vertebral artery. Advantages of this novel approach are shortening the graft length and surgical timing, less invasiveness, and optimizing surgical trajectories for completion of both donor and recipient bypass anastomosis.

Bypass Surgery for the Treatment of Dolichoectatic Basilar Trunk Aneurysms: A Work in Progress

BACKGROUND

The treatment of dolichoectatic basilar trunk aneurysms has been ineffectual or morbid due to nonsaccular morphology, deep location, and involvement of brainstem perforators. Treatment with bypass surgery has been advocated to eliminate malignant hemodynamics and to stabilize aneurysm growth.

OBJECTIVE

To validate that flow alteration with bypass and parent artery occlusion favorably impacts aneurysm progression.

METHODS

Surgical management evolved in 3 phases, each with different hemodynamic alterations.

RESULTS

During a 17-year period, 37 patients with dolichoectatic basilar trunk aneurysms were retrospectively identified, of whom 21 patients were observed, 12 treated immediately, and 4 selected for treatment after clinical progression. In phase 1, flow reversal was overly thrombogenic, despite heparin (N = 5, final mortality, 100%). In phase 2, flow reduction with intracranial-to-intracranial bypass was safer than flow reversal, but did not prevent progressive aneurysm enlargement (N = 3, final mortality 67%). In phase 3, distal clip occlusion of the basilar trunk aneurysm preserved anterograde flow in the aneurysm without rupture, but reduced flow threatened perforator patency, despite treatment with clopidogrel (N = 8, final mortality 62%).

CONCLUSION

Shifting treatment strategy for dolichoectatic basilar trunk aneurysms improved surgical (80% to 50%) and final mortalities (100% to 62%), with stabilization of aneurysms in the phase 3 survivors. Good outcomes are determined by perforator preservation and mitigating aneurysm thrombosis. Occlusion techniques with increased distal run-off seem to benefit perforators. The treatment of dolichoectatic basilar trunk aneurysms can advance through concentrated management in dedicated centers, concerted efforts to study morphology and hemodynamics with computational methods, and widespread collection of registry data.

ABBREVIATIONS

4D PC-MRI, time-resolved phase-contrast MRIAICA, anterior inferior cerebellar arteryCE-MRA, high-resolution contrast-enhanced MR angiographyEC-IC, extracranial-to-intracranial bypassMCA, middle cerebral arteryMR, magnetic resonancemRS, modified Rankin ScalePCA, posterior cerebral arteryPICA, posterior inferior cerebellar arterySCA, superior cerebellar arterySTA, superficial temporal arteryVA, vertebral artery.

Flow diversion radial artery bypass graft coupled with terminal basilar artery occlusion for the treatment of complex basilar apex aneurysms: operative nuances

BACKGROUND

A subset of basilar apex aneurysms are unsuitable for either primary microsurgical clipping or endovascular coiling. These complex aneurysms can be treated by terminal basilar artery occlusion, but only if collateral circulation is adequate. To circumvent these complications, a high-flow vertebral artery-posterior cerebral artery or middle cerebral artery-posterior cerebral artery bypass may be performed to create an adequate collateral circulation to allow treatment of the aneurysm by basilar artery occlusion and/or clipping.

OBJECTIVE

To discuss the operative nuances of this approach in the case of a 47-year-old man with progressive hemiparesis resulting from brainstem compression from a giant, unruptured basilar apex aneurysm with absent posterior communicating artery collaterals and incorporation of bilateral superior cerebellar arteries and posterior cerebral arteries within the aneurysm neck.

METHODS

The patient underwent a staged bypass from V3 to P2 coupled with terminal basilar artery occlusion.

RESULTS

The patient initially presented as modified Rankin Scale score 2 with right hemiparesis. The aneurysm ruptured after the first stage of the operation, and the patient underwent a V3 to P2 bypass the next day. His postprocedural neurologic decline improved at the 14-month follow-up to modified Rankin Scale score 2, with substantial reduction in aneurysm size observed at 9 months. The outcomes for 3 other bypass cases for basilar apex aneurysms are also summarized.

CONCLUSION

: We discuss the indications, preoperative diagnostic workup, operative management, and postoperative outcomes in managing challenging basilar apex aneurysms. In our experience, high-flow bypass procedures with or without hunterian ligation in the treatment of these aneurysms are well tolerated with good long-term results.

Distal superficial temporal artery to proximal posterior cerebral artery bypass by posterior oblique transzygomatic subtemporal approach

This article investigates the possibility for the distal superficial temporal artery (STA) to proximal posterior cerebral artery (PCA) direct bypass by subtemporal oblique posterior transzygomatic approach. Five adult cadaveric specimens were dissected. Cadeveric dissection protocol was approved by the Research Ethics Committee. A preauricular vertical skin incision was made, the trunk of STA was identified, and bifurcation, frontal, and parietal branches of the STA were followed distally. Posterior zygomatic arch osteotomy and microcraniotomy were then performed, and the dura was opened. The temporal lobe was retracted, interpeduncular and ambient cisterns were opened, and the P2 segment of the PCA was exposed. Parietal branch of STA and P2 segment of the PCA was anastomosed. The average length of the transected STA from the bifurcation and the zygomatic arch were 47.3 ± 2.1 mm and 71.4 ± 2.3 mm, respectively. The mean calibers of the parietal and frontal branch of the STA at this distance were 1.6 ± 0.1 and 1.4 ± 0.2, respectively. The mean diameter of the P2 was 2.1 ± 0.2 mm. Because of the calibers of the parietal branch of the STA and proximal PCA are over 1.5 mm and 2.0 mm, respectively, this direct end-to-side bypass technique may be a reasonable alternative in suitable cases.

Novel technique to improve vessel mismatch when using saphenous vein bypass grafts for intracranial revascularization procedures

Cerebral bypass procedures in the posterior circulation are difficult to perform and are considered to be high-risk surgery. Venous grafts, like that formed using the saphenous vein (SV), are simple to obtain without posing a high risk of morbidity. The main disadvantage of these high-flow grafts is the mismatch in vessel diameter between donor and recipient vessels in the posterior circulation. The authors performed a retrospective case study based of data from intraoperative video, patient charts, axial images, and cerebral angiograms. They treated a 66-year-old man who presented with a giant aneurysm of the vertebrobasilar junction and another large aneurysm of the basilar tip. They chose to create a vertebral artery (VA)-superior cerebellar artery anastomosis with a tapered-down SV graft. It was necessary to reengineer the SV graft to include a gentle taper that would allow for this anastomosis. The vein was incised for a distance of 2.5 cm. A triangular section of the vein, 2 mm at the base and 20 mm high, was then excised from the opened end of the SV. The 2.5-cm-long venotomy was then closed with interrupted 9-0 Prolene sutures creating a gentle taper to the vein down to ~ 2.5 mm in diameter. Thereafter, the authors created a standard end-to-side anastomosis of the VA to the SV with 8-0 Prolene. Postoperatively both VAs were obliterated with coils just proximal to the vertebrobasilar aneurysm. The bypass was patent; after a prolonged stay in the intensive care unit, the patient recovered gradually. This technique of linear venotomy along the distal 2.5 cm of the vein and subsequent tapering down of the diameter diminishes the circumference of the distal end of the graft, facilitating bypass to smaller vessels. This is a novel and feasible technique to eliminate vessel mismatch in cerebral bypass procedures in the difficult accessible vessels of the posterior circulation.

Deep Bypasses to the Distal Posterior Circulation

OBJECTIVE

The subtemporal approach for a superficial temporal artery–to–superior cerebellar artery bypass requires significant superior retraction that can injure the temporal lobe, compromise veins, and cause edema postoperatively. In contrast, the pretemporal approach requires posterolateral retraction that seems to be less injurious to the temporal lobe and better tolerated clinically. We hypothesized that the pretemporal approach provides ample exposure, more gentle retraction, and better clinical results than the subtemporal approach.

METHODS

Standard orbitozygomatic-pterional and subtemporal approaches were performed on both sides of 4 formalin-fixed cadaver heads for morphometric measurements. Temporal lobe retraction was quantified for each approach in terms of brain shift and retraction pressure by using both sides of 3 fresh, unfixed cadaver heads. Similar morphometric measurements were made in 14 patients in whom bypasses to the distal posterior circulation were performed. The effect of temporal lobe retraction was assessed with edema volumes on postoperative computed tomography scans.

RESULTS

In cadaver heads and in patients, the pretemporal approach optimized exposure of the P2A segment of the posterior cerebral artery (PCA) and the subtemporal approach optimized exposure of the lateral pontomesencephalic segment of the superior cerebellar artery (SCA). Working depths and lengths of exposed artery were similar with these 2 approaches, but the PCA was a larger recipient than the SCA. Brain shift was 42% less with pretemporal than with subtemporal retraction, and retraction pressure was 43% less with pretemporal than with subtemporal retraction. The volume of temporal lobe edema was 56% less in patients with bypasses performed with the pretemporal approach as compared with the subtemporal approach.

CONCLUSION

Pretemporal exposure of the PCA is equivalent to subtemporal exposure of the SCA, but the pretemporal approach is facilitated by a larger recipient artery. Posterolateral temporal lobe retraction associated with the pretemporal approach is gentler than superior retraction with the subtemporal approach. These results validate our preference for the pretemporal approach over the subtemporal approach when performing deep bypasses to the posterior circulation.