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

Impact of Suturing Techniques on Microvascular Anastomosis Maturation

BACKGROUND

 Microvascular anastomosis using interrupted suture is a widely accepted standard technique. Continuous suture is less common due to the presumption that its firmness can negatively affect anastomosis maturation. The purpose of this study was to determine whether the use of continuous suture allows maturation of the microanastomosis site.

METHODS

 A rat common carotid artery (CCA) end-to-end microanastomosis model was utilized, with 19 Long-Evans rats in the interrupted suture group and 13 in the continuous suture group. Immediate blood flow of the operated and contralateral intact CCAs was compared before clamping, at the completion of the anastomosis and after 14 days. Quantitative transit time flowmetry measurement and histologic examination were employed.

RESULTS

 Initial blood flow in both intact CCAs was similar across all animals (p = 0.004). In the interrupted suture group, the median anastomosis blood flow was 88.9% of the contralateral CCA blood flow, with a median suture time of 46 minutes. After 2 weeks, blood flow increased to 96.1%. In the continuous suture group, the median anastomosis blood flow was 88.3% of the contralateral CCA blood flow, with a median suture time of 30 minutes. After 2 weeks, blood flow increased to 100.0%. The reduction in suture time achieved with continuous suture was 34.8% (p < 0.001). Histologic examination confirmed scar maturity.

CONCLUSIONS

 The maturation rates of continuous and interrupted suture microanastomosis were comparable in our study, implying that concerns about the suture restricting maturation may be unwarranted. Additional finding is the potential for a reduction in microanastomosis time when using the continuous suture technique.

Evaluating the Arteriotomy Size of a New Sutureless Coronary Anastomosis Using a Finite Volume Approach

OBJECTIVES

The ELANA® Heart Bypass creates a standardized sutureless anastomosis. Hereby, we investigate the influence of arteriotomy and graft size on coronary hemodynamics.

METHODS

A computational fluid dynamics (CFD) model was developed. Arteriotomy size (standard 1.43 mm2; varied 0.94 - 3.6 mm2) and graft diameter (standard 2.5 mm; varied 1.5 - 5.0 mm) were independent parameters. Outcome parameters were coronary pressure and flow, and fractional flow reserve (FFR).

RESULTS

The current size ELANA (arteriotomy 1.43 mm2) presented an estimated FFR 0.65 (39 mL/min). Enlarging arteriotomy increased FFR, coronary pressure, and flow. All reached a maximum once the arteriotomy (2.80 mm2) surpassed the coronary cross-sectional area (2.69 mm2, i.e. 1.85 mm diameter), presenting an estimated FFR 0.75 (46 mL/min). Increasing graft diameter was positively related to FFR, coronary pressure, and flow.

CONCLUSION

The ratio between the required minimal coronary diameter for application and the ELANA arteriotomy size effectuates a pressure drop that could be clinically relevant. Additional research and eventual lengthening of the anastomosis is advised.

Microsurgery for intracranial aneurysms: A qualitative survey on technical challenges and technological solutions

Introduction

Microsurgery for the clipping of intracranial aneurysms remains a technically challenging and high-risk area of neurosurgery. We aimed to describe the technical challenges of aneurysm surgery, and the scope for technological innovations to overcome these barriers from the perspective of practising neurovascular surgeons.

Materials and Methods

Consultant neurovascular surgeons and members of the British Neurovascular Group (BNVG) were electronically invited to participate in an online survey regarding surgery for both ruptured and unruptured aneurysms. The free text survey asked three questions: what do they consider to be the principal technical barriers to aneurysm clipping? What technological advances have previously contributed to improving the safety and efficacy of aneurysm clipping? What technological advances do they anticipate improving the safety and efficacy of aneurysm clipping in the future? A qualitative synthesis of responses was performed using multi-rater emergent thematic analysis.

Results

The most significant reported historical advances in aneurysm surgery fell into five themes: (1) optimising clip placement, (2) minimising brain retraction, (3) tissue handling, (4) visualisation and orientation, and (5) management of intraoperative rupture. The most frequently reported innovation by far was indocyanine green angiography (84% of respondents). The three most commonly cited future advances were hybrid surgical and endovascular techniques, advances in intraoperative imaging, and patient-specific simulation and planning.

Conclusions

While some surgeons perceive that the rate of innovation in aneurysm clipping has been dwarfed in recent years by endovascular techniques, surgeons surveyed highlighted a broad range of future technologies that have the potential to continue to improve the safety of aneurysm surgery in the future.

The Sutureless Excimer Laser Anastomosis Clip Pilot Study: a feasibility and safety study

BACKGROUND

The excimer laser-assisted non-occlusive anastomosis (ELANA) bypass technique may have the advantage of its non-occlusive design in the treatment of last-resort cases where endovascular treatment or direct clipping is considered to be unsafe. However, the technique remains technically challenging. Therefore, a sutureless ELANA Clip device (SEcl) was developed to simplify the technique avoiding tedious anastomosis stitching in depth. The present study investigates the clinical feasibility and safety of the SEcl technique.

METHODS

Three patients with complex and large aneurysms in the anterior circulation were selected after multidisciplinary consensus that the aneurysms were too complex for endovascular or direct clipping treatment options. Bypass surgery was considered as a last-resort treatment option, and after preoperative evaluation and informed consent, SEcl bypass surgery was performed. Applicability, technical aspects and patient outcomes are assessed.

RESULTS

All aneurysms were excluded from the circulation. The creation of the intracranial anastomosis was easier and faster. No device-related serious adverse events were encountered, and all outcomes were favorable (one patient stable Modified Rankin Scale, two patients improved).

CONCLUSION

The SEcl anastomosis technique is feasible and, considering the severity of the disease, relatively safe. It can be considered a treatment option in very difficult-to treat last-resort aneurysm cases. From this study, further developments in minimizing clip size and application in cardiac surgery are initiated.

Preclinical Comparison of Distal Off-Pump Anastomotic Remodeling: Hand-Sewn Versus ELANA Heart Bypass

Objective: The ELANA Heart Bypass System is a new sutureless technique for coronary anastomoses. A titanium clip connects the graft with the coronary artery, whereafter the arteriotomy is performed by excimer laser. Since this anastomotic construction evidently differs from the standard hand-sewn anastomosis, we aim to evaluate the process of anastomotic healing and remodeling. Methods: Preclinical evaluation of anastomotic remodeling in 42 pigs who underwent off-pump left internal mammary artery to left anterior descending artery anastomosis by either the ELANA Heart Bypass (n = 24) or the hand-sewn (n = 18) technique. Anastomotic remodeling was evaluated by scanning electron microscopy and histology in short-term follow-up intervals up to 3 months. Anastomotic patency is determined by coronary angiography at latest follow-up before termination. Results: The nonendothelial surface of both the ELANA and the hand-sewn anastomoses were covered with neointima from 14 days onwards. Only half the amount of intima hyperplasia was present in the anastomotic surface of the patent ELANA anastomosis, compared with the hand-sewn anastomosis (98 [48–1358] vs 218 [108–296] µm, P = 0.001). Yet patency of the ELANA was inferior to the hand-sewn anastomoses (79% vs 100%, P = 0.06). Conclusions: This study shows the technical perioperative feasibility of the ELANA Heart Bypass System. Although limited intima hyperplasia was observed, hand-sewn anastomoses had superior patency during follow-up. The results of this trial suggest that an additional study with a new prototype is required before clinical implementation.

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.

Final Results of the Prospective Multicenter Excimer Laser-Assisted High-Flow Bypass Study on the Treatment of Giant Anterior Circulation Aneurysms

BACKGROUND

Both conventional bypass utilizing temporary recipient vessel occlusion and the excimer laser-assisted nonocclusive anastomosis (ELANA) bypass technique are possible strategies in the treatment of giant aneurysms. These treatments have only been studied in single institutional retrospective studies. The potential advantage of the ELANA technique is the absence of temporary occlusion of major arteries, decreasing the risk of intraoperative ischemia.

OBJECTIVE

To investigate the risks and potential benefits of high-flow bypass surgery for giant and complex aneurysms of the anterior cerebral circulation. In addition, the effectiveness of the ELANA bypass procedure in the treatment of these aneurysms is determined.

METHODS

A total of 37 patients were included in 8 vascular neurosurgical centers in the United States, Canada, and Europe. A 30-d postoperative bypass follow-up was studied by using digital subtraction angiography and/or magnetic resonance angiography and computed tomography angiography to assess patency as well as by clinical monitoring in all patients.

RESULTS

In 35 patients, an ELANA high-flow bypass was performed and the aneurysm treated. Four patients had remaining neurological deficits after 30 d caused by stroke (11.4%). These strokes were not related to the ELANA anastomosis device.

CONCLUSION

This study does not prove that the ELANA technique has an advantage over conventional bypass techniques, but it appears to be an acceptable alternative to conventional transplanted high-flow bypass in this very-difficult-to-treat patient group, especially in select patients whom cannot be bypassed using conventional means in which temporary occlusion is considered to be not recommended.

Feasibility of the new sutureless excimer laser-assisted non-occlusive anastomosis clip in a rabbit model

BACKGROUND

The excimer laser-assisted non-occlusive anastomosis (ELANA) technique facilitates the construction of anastomoses without temporary occlusion of the recipient artery. Experiments aimed at simplifying the technique eventually resulted in a sutureless ELANA slide (SEsl) anastomosis. After the first clinical use, new insights lead to the application of a clip at the back of the device, the SELANA clip (SEcl). The SEcl offers a distinct advantage over the SEsl since no sealant is necessary. In this study, we determine the feasibility of the SEcl anastomosis in an in vivo rabbit model.

METHODS

15 SEcl anastomoses and 15 conventional ELANA anastomoses were created on the abdominal aorta in 5 rabbits. Mean application times, flap retrieval rates, hemostasis, and burst pressures were assessed.

RESULTS

The mean application time of the SEcl anastomoses was 11.4 min versus 39.0 min for the ELANA anastomoses (mean difference, 27.6 min; 95% CI, 20.6-34.7). The flap retrieval rate of the SEcl anastomoses (14/15) was not inferior to the flap retrieval rate of the ELANA anastomoses (13/15). Direct hemostasis was achieved in 13/15 (87%) SEcl anastomoses and in 14/15 (94%) ELANA anastomoses. All SEcl anastomoses were resistant to provoked pressures until 250 mmHg.

CONCLUSION

The SEcl anastomosis is technically feasible in in vivo experiments. Mean application time, flap retrieval rate, hemostasis, and burst pressure are not inferior to the conventional ELANA anastomosis. Further long term experiments should be performed to assess safety, patency, and reendothelialization.

Intraoperative neurophysiological monitoring of extracranial-intracranial bypass procedures

OBJECT

Intraoperative neurophysiological monitoring (IONM) represents an established tool in neurosurgery to increase patient safety. Its application, however, is controversial. Its use has been described as helpful in avoiding neurological deterioration during intracranial aneurysm surgery. Its impact on extracranial-intracranial (EC-IC) bypass surgery involving parent artery occlusion for the treatment of complex aneurysms has not yet been studied. The authors therefore sought to evaluate the effects of IONM on patient safety, the surgeon's intraoperative strategies, and functional outcome of patients after cerebral bypass surgery. Intraoperative neurophysiological monitoring results were compared with those of intraoperative blood flow monitoring to assess bypass graft perfusion.

METHODS

Compound motor action potentials (CMAPs) were generated using transcranial electrical stimulation in patients undergoing EC-IC bypass surgery. Preoperative and postoperative motor function was analyzed. To assess graft function, intraoperative flowmetry and indocyanine green fluorescence angiography were performed. Special care was taken to compare the relevance of electrophysiological and blood flow monitoring in the detection of critical intraoperative ischemic episodes.

RESULTS

The study included 31 patients with 31 aneurysms and 1 bilateral occlusion of the internal carotid arteries, undergoing 32 EC-IC bypass surgeries in which radial artery or saphenous vein grafts were used. In 11 cases, 15 CMAP events were observed, helping the surgeon to determine the source of deterioration and to react to it: 14 were reversible and only 1 showed no recovery. In all cases, blood flow monitoring showed good perfusion of the bypass grafts. There were no false-negative results in this series. New postoperative motor deficits were transient in 1 case, permanent in 1 case, and not present in all other cases.

CONCLUSIONS

Intraoperative neurophysiological monitoring is a helpful tool for continuous functional monitoring of patients undergoing large-caliber vessel EC-IC bypass surgery. The authors' results suggest that continuous neurophysiological monitoring during EC-IC bypass surgery has relevant advantages over flow-oriented monitoring techniques such as intraoperative flowmetry or indocyanine green-based angiography.

Surgical strategies for aneurysms deemed unclippable and uncoilable

Although most cerebral aneurysms can nowadays be successfully treated either by standard clipping or sole coiling, a subset of aneurysms may not be amenable to standard clipping or coiling and require alternative treatment options. Surgical options, other than clipping and/or endovascular options other than sole coiling, may be the optimal treatment plan for some complex aneurysms. Surgical strategies for such complex aneurysms include parent artery occlusion, revascularization procedures and flow redirection. In this article, we review which factors are predictive of failure of conventional aneurysm treatment options; summarize key information needed to orient treatment decision; and discuss surgical options for unclippable and uncoilable aneurysms.

The acute effect of increased laser energy during the excimer laser-assisted non-occlusive anastomosis procedure on the vessel wall of the recipient artery: a histopathological study

BACKGROUND AND OBJECTIVE

The excimer laser-assisted non-occlusive anastomosis (ELANA) technique is a way of making an anastomosis of vessels without temporal occlusion that is used for cerebral revascularization. Currently, 10 mJ of laser energy is used during the ELANA procedure. We have recently demonstrated that increasing the laser energy may increase flap retrieval rate. The aim of the present study was to study the acute effect of increased laser energy during the ELANA procedure on the recipient vessel wall.

MATERIALS AND METHODS

The ELANA technique was performed on the abdominal aortas of rabbits under anesthesia using three categories of laser energy (two laser episodes of 10, 13, and 15 mJ, respectively). The rabbits were subsequently sacrificed and the anastomoses were removed. A non-lased rabbit aorta was used as control. Recipient arteries were studied using histopathology and transmission electron microscopy.

RESULTS

In all three categories of laser energy and in the control group, the tunica media and adventitia adjacent to the anastomosis were intact, apart from damage caused by sutures. In the control group, the endothelium was fully intact. In the 10 and 13 mJ subgroups, the endothelium was mostly intact [92% (range 85-98) and 87% (range 80-90) for 10 and 13 mJ, respectively]. In the 15 mJ subgroup, most of the endothelium was absent [32% (range 20-40) of endothelium intact], predominantly at the side opposed to the anastomosis.

CONCLUSION

Increasing the laser energy during the ELANA procedure from 10 to 13 mJ does not cause additional acute damage to the vessel wall. Increasing the laser energy from 13 to 15 mJ results in increased acute damage of the endothelium, whereas tunica media and adventitia remain unaffected. Further studies are required to assess the long-term effects of increased laser energy during the ELANA technique.

Extracranial Posterior Communicating Artery Bypass for Revascularization of Patients With Common Carotid Artery Occlusion

BACKGROUND:

Extracranial-intracranial bypass surgery provides blood flow augmentation in patients suffering from intracranial or long-distance conductance artery stenosis or occlusion that otherwise cannot be treated. The standard procedure for these cases is an anastomosis between the superficial temporal and middle cerebral arteries. However, in patients presenting with common carotid artery occlusion, the superficial temporal artery is no longer sufficiently perfused. For these patients, alternative revascularization strategies have to be applied.

OBJECTIVE:

To describe a novel strategy for revascularization of patients with common carotid artery occlusion, ie, the extracranial posterior communicating artery bypass.

METHODS:

Two patients with chronic cerebrovascular compromise resulting in transitory ischemic attacks and/or border-zone infarctions caused by common carotid artery occlusion were referred to our institution. A radial artery bypass was established between the third segment of the vertebral artery and an M3 branch of the middle cerebral artery. The vertebral artery was exposed between the vertebral lamina of C1 and occipital bone via a paramedian incision. The bypass was tunneled subcutaneously, conducted intracranially via a tailored extended burr-hole craniotomy, and anastomosed to a recipient M3 vessel.

RESULTS:

The postoperative course of both patients was uneventful in terms of cerebral ischemia or bleeding complications. In both patients, postoperative angiographic controls revealed an excellent bypass function with markedly improved hemispheric filling of multiple middle cerebral artery branches. The patients were discharged without new neurological symptoms.

CONCLUSION:

Our extracranial posterior communicating artery bypass using a radial artery transplant from the vertebral artery to the middle cerebral artery is a useful tool to treat patients suffering from hemodynamic cerebrovascular compromise caused by common carotid artery occlusion.

Haemodynamic stroke: clinical features, prognosis, and management

Haemodynamic stroke is a type of ischaemic stroke that is caused by hypoperfusion rather than by embolism or local vasculopathy. It can be caused by systemic diseases such as heart failure or hypotension, but also by severe obstruction of the carotid or vertebral arteries. Patients with haemodynamic stroke or transient ischaemic attack might show specific clinical features that distinguish them from patients with embolism or local small-vessel disease. Ancillary investigations of cerebral perfusion can show whether blood flow to the brain is compromised and provide important prognostic information. Management of patients who have hypoperfusion as the major cause of ischaemic stroke or as a contributing factor is hampered by the lack of clinical trials. Treatment aimed at increasing cerebral blood flow might be considered in selected patients on the basis of information from case series. Further research is needed to define criteria for the diagnosis of haemodynamic stroke and to investigate treatment options in controlled studies.

Endoscopic radial artery harvesting for U-clip high-flow EC-IC bypass: technical report

INTRODUCTION

Bypass and aneurysm trapping constitute a well-known surgical solution for aneurysms that are not suitable for clipping or coiling. New techniques are available that make EC-IC bypass procedures easier, safer and, possibly, less invasive. The nitinol self-closing U-Clip device (Medtronic, Inc., Minneapolis) has been designed to facilitate the interrupted suture technique by eliminating the need for suture management, knot tying, and surgical assistance.

MATERIALS AND METHODS

We present two consecutive U-clip bypass procedures in which the radial artery graft was harvested endoscopically.

RESULTS

This novel bypass technique employs endoscopy to minimise arm injury due to radial artery harvesting and self-closing U-clips to simplify the intracranial micro-anastomosis and reduce the temporary occlusion time. Angiography confirmed bypass patency in all patients.

DISCUSSION

Combined with the innovative use of U-clips, these two examples illustrate how new technologies can simplify EC-IC bypass surgery while yielding a better cosmetic and functional outcome.

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

Object

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

Methods

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

Results

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

Conclusions

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

Cerebrovascular insufficiency as the criterion for revascularization procedures in selected patients: a correlation study of xenon contrast-enhanced CT and PWI

In order to identify patients who suffer from hemodynamic cerebral insufficiency and can benefit from cerebral revascularization procedures, xenon-CT scanning has been established to reliably measure the critical cerebrovascular reserve capacity. As a need for alternative quantification methods arises, this study aims to characterize the significance of both time-to-peak (TTP) and mean transit time (MTT) in perfusion-weighted imaging (PWI) in this particular subset of patients. Ten patients in routine preoperative work-up for cerebral revascularization were prospectively enrolled and underwent both XeCT scanning and PWI. Cerebrovascular reserve capacity (CVRC) was calculated for each region of interest (ROI, n = 504) after administration of a vasoactive stimulus. ROIs were anatomically matched with those of PWI after TTP and MTT were calculated. Highly significant negative correlation was found for TTP and CVRC for all ROIs (r = -0.3954, p < 0.0001; symptomatic ROIs: r = -0.4867, p < 0.0001). Correlation was weak for MTT and CVCR (r = -0.1287; p < 0.01). The optimum threshold for TTP to detect impaired cerebrovascular reactivity in our patient group was 4 s (specificity 90.8%, sensitivity 44.4%) for all ROIs (TTP > 4.4 s for symptomatic ROIs, specificity 88.4%, sensitivity 62.7%). An approximative equation to calculate the probability of pathological findings could be derived from the data. The positive predictive value (PPV) was 0.76 (symptomatic 0.78) with a negative predictive value (NPV) of 0.71 (symptomatic 0.78). While PWI currently is not able to replace XeCT in the direct quantification of CVRC, it may serve as a readily available follow-up tool. A TTP threshold of greater than 4 s allows to confirm a cerebrovascular compromise in a selected high-risk subgroup of patients.

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.

Evolution of cerebral revascularization techniques

✓As a leading cause of death and disability in patients across the world, stroke is a problem that plagues both neurosurgeons and neurologists alike. Whether a result of atherosclerosis, moyamoya disease, or a complication in the treatment of a complex intracranial aneurysm, cerebrovascular occlusion can have devastating effects on patients. For nearly half a century neurosurgeons have searched for safer, more effective ways to increase the amount of blood flow to ischemic brain tissue. From the first extracranial–intracranial bypasses to the recent technological advancements seen with endovascular therapy, cerebral revascularization techniques have been constantly evolving. Over the years cerebral ischemia has gone from a condition that was previously considered surgically untreatable, to a condition with several viable options for prevention and treatment. In this paper the authors discuss the historical evolution of treatment for cerebrovascular occlusive disease.

Excimer laser–assisted nonocclusive anastomosis

Excimer laser–assisted nonocclusive anastomosis (ELANA) has been developed over the past 14 years for assistance in the creation of intracranial bypasses. The ELANA technique allows the creation of intracranial–intracranial and extracranial–intracranial bypasses without the need for temporary occlusion of the recipient artery, avoiding the inherent risk associated with occlusion time. In this review the authors discuss the technique and its indications, while reviewing the clinical results of the procedure. The technique itself is explained using cartoon drawings and intraoperative photographs. Advantages and disadvantages of the technique are also discussed.

Sutureless nonocclusive bypass surgery in combination with an expanded polytetrafluoroethylene graft. Laboratory investigation

OBJECT

Cerebral aneurysms that cannot be treated by clip or coil placement can be treated with high-flow bypass surgery using techniques such as the excimer laser-assisted nonocclusive anastomosis (ELANA). To simplify the technique, a sutureless ELANA (SELANA) was developed in combination with an expanded polytetrafluoroethylene (ePTFE) graft.

METHODS

In 18 rabbits a bypass was constructed on the abdominal aorta using the SELANA technique with an ePTFE graft, resulting in 18 bypasses and 36 anastomoses. Short-term effects were analyzed in the first 2 weeks and at 2 and 3 months after the procedure. Patency was evaluated using quantitative ultrasound flowmetry. The anastomotic sites were studied using scanning electron microscopy.

RESULTS

Construction of the bypass using the SELANA technique was easier and faster (15-25 minutes) compared with bypasses made with the ELANA technique (> 90 minutes). At the end of follow-up, 16 of 18 bypasses were patent. Of 36 SELANA anastomoses, 32 could be completed without short temporary occlusion of the recipient vessel. Scanning electron microscopy showed complete coverage of all anastomoses with neointimal repair tissue after 10 days.

CONCLUSIONS

The SELANA technique provides further advantages over the conventional ELANA technique in ease of use and shortening of procedure time. The patency rate in this series was 89% and neointima repair tissue at the anastomosis site was complete after 10 days. Further experimental studies of the long-term patency and safety of this technique are necessary before clinical application.

Treatment of hemodynamic insufficiency in chronic CCA occlusion using a short saphenous vein interposition graft: diagnostic and technical considerations

Extracranial-intracranial bypass surgery has been shown to reverse hemodynamic insufficiency on the basis of steno-occlusive disease of the internal carotid artery (ICA) or middle cerebral artery. In contrast, chronic occlusion of the common carotid artery (CCA) without extracranial donor vessels affords alternative revascularization procedures as well as a more elaborate preoperative workup. This case is intended to illustrate the specific diagnostic approach and considerations as well as a beneficial treatment modality in the setting of pronounced hemodynamic insufficiency as a consequence of a CCA occlusion, in conjunction with contralateral CCA and ICA stenoses. A 61-year-old man complaining of new onset aphasia underwent vascular imaging that revealed a proximal occlusion of the left CCA with a concomitant patent proximal ICA on ultrasound. Functional cerebral blood flow measurement including Xenon-enhanced computer tomography showed corresponding chronic hemodynamic insufficiency of the left hemisphere. The patient received a modified revascularization procedure, where a saphenous vein was used as interposition graft between the subclavian artery and the left proximal ICA. Postoperatively, both clinical and morphological improvement were noted. Successful treatment of hemodynamic insufficiency because of chronic CCA occlusion necessitates a thorough preoperative workup and application of alternative revascularization strategies.

The Use of the Excimer Laser-assisted Anastomosis Technique Alleviates Neuroanesthesia During Cerebral High-flow Revascularization

In patients with complex intracranial aneurysms or skull base tumors, parent vessel occlusion and flow replacement by high-flow bypass surgery is a demanding therapy, both for the neurosurgeon and the neuroanesthesiologist. One reason for this is the need for prolonged temporary occlusion of a major cerebral artery, which carries a high risk of perioperative ischemia and necessitates versatile neuroprotective measures during anesthesia. Recently, a novel excimer laser-assisted nonocclusive anastomosis (ELANA) technique has been introduced, circumventing the need for temporary occlusion of cerebral vessels. We hypothesized that the use of this ELANA technique would facilitate also the neuroanesthesiologic management of these patients. To test this, we reviewed the details of the neuroanesthesiologic management of patients undergoing ELANA high-flow bypass surgery at our institution. Twenty-nine patients with giant aneurysms (n=27) or skull base tumor (n=2) who were undergoing parent vessel occlusion and permanent flow replacement by high-flow bypass surgery using the ELANA technique were investigated retrospectively. The records of the patients were analyzed for induction and maintenance of anesthesia, fluid therapy, transfusion requirements, hemodynamic parameters, and brain protective strategies. Although we are not able to provide a sufficient body of cohort data to compare the neuroanesthesiologic management of patients undergoing the conventional anastomosis technique with management using the ELANA technique, in each of our reported cases the conventional anastomosis technique would have entailed a high probability of prolonged temporary occlusion that would, in turn, have warranted intensive brain-protective strategies. The observation that use of the ELANA technique precluded the necessity of brain-protective strategies without entailing perioperative cerebral infarction suggests that the ELANA technique supports the neurosurgeon in creating difficult permanent intracranial anastomoses and also facilitates neuroanesthesiologic management of patients undergoing cerebral high-flow revascularization procedures.

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.

Challenges in the Endovascular Treatment of Giant Intracranial Aneurysms

OBJECTIVE:

Giant intracranial aneurysms present unique therapeutic intricacies. The purpose of this study was to evaluate the anatomic and hemodynamic characteristics of these lesions and the current endovascular and combined surgical and endovascular techniques available for their treatment.

METHODS:

A review of the literature and the personal experiences of the authors with endovascular treatment of giant aneurysms are presented. This review included anatomic and hemodynamic features and analysis of the diverse endovascular techniques that have been reported for the management of these aneurysms.

RESULTS:

Anatomic features that create particular challenges in the therapeutic approach of giant aneurysms include size, shape (saccular, fusiform, serpentine), neck dimensions, branch involvement, intraluminal thrombosis, and location. Hemodynamic characteristics that affect endovascular treatment are lateral or terminal aneurysm type of flow and embolic material placement (inflow versus outflow aneurysmal region). The current endovascular therapeutic approaches include parent artery occlusion, trapping, endosaccular embolization with or without adjunctive techniques such as balloon-assisted or stent placement, and combined surgical and endovascular approaches, mainly with surgical revascularization and endovascular occlusion.

CONCLUSION:

Although there are a wide variety of endovascular therapeutic options for the treatment of giant intracranial aneurysms, none of the current techniques is completely successful and free of complications in the management of these complex lesions. A detailed and individualized analysis of each case in conjunction with sufficient understanding of the anatomy and hemodynamics of a particular aneurysm should guide the therapeutic decision. Further research advances will assist in elucidating the factors predisposing to genesis, progression, and aggressive clinical manifestations of these giant lesions.