Hybrid treatment of common carotid artery occlusion with ring-stripper endarterectomy plus stenting

Comparison of the treatment strategies for symptomatic chronic internal carotid artery occlusion

OBJECTIVE

The best management of symptomatic chronic internal carotid artery occlusion (CICAO) has been controversial. This systematic review and meta-analysis were to compare the outcomes of different treatment strategies for symptomatic CICAO.

METHODS

Two independent researchers conducted a search of articles on the treatment of CICAO published between January 2000 and October 2023 in PubMed, Web of Science, Embase, and The Cochrane Library. Twenty-two articles were eligible for meta-analysis using a random effects model to combine and analyze the data for the pooled rates of stroke and death, and the rates of procedural success and significant restenosis/occlusion.

RESULTS

A total of 1193 patients from 22 publications were included in this study. Six of them had bilateral internal carotid artery occlusion. The 30-day stroke and death rates were 1.1% (95% confidence interval [CI], 0%-4.4%) in the best medical treatment (BMT) group, 4.1% (95% CI, 0.7%-9.3%; I2 = 71.4%) in the extracranial-intracranial (EC-IC) bypass group, 4.4% (95% CI, 2.4%-6.8%; I2 = 0%) in the carotid artery stenting (CAS) group, and 1.2% (95% CI, 0%-3.4%; I2 = 0%) in the combined carotid endarterectomy (CEA) and stenting (CEA + CAS) group. During follow-up of 16.5 (±16.3) months, the stroke and death rates were 19.5%, 1.2%, 6.6%, and 2.4% in the BMT, EC-IC, CAS, and CEA + CAS groups respectively. The surgical success rate was 99.7% (95% CI, 98.5%-100%; I2 = 0%) in the EC-IC group, 70.1% (95% CI, 62.3%-77.5%; I2 = 64%) in the CAS group, and 86.4% (95% CI, 78.8%-92.7%; I2 = 60%) in the CEA + CAS group. The rate of post-procedural significant restenosis or occlusion was 3.6% in the EC-IC group, 18.7% in the CAS group, and 5.7% in the CEA + CSA group. The surgical success rate was negatively associated by the length of internal carotid artery (ICA) occlusion. Surgical success rate was significantly higher in the patients with occlusive lesion within C1 to C4 segments, compared with those with occlusion distal to C4 segment (odds ratio, 11.3; 95% CI, 5.0-25.53; P < .001). A proximal stump of ICA is a favorable sign for CAS. The success rate of CAS was significantly higher in the patients with an ICA stump than that in the patients without (odds ratio, 11.36; 95% CI, 4.84-26.64; P < .01). However, the success rate of CEA + CAS was not affected by the proximal ICA stump.

CONCLUSIONS

For the management of symptomatic CICAO, BMT alone is associated with the highest risk of mid- and long-term stroke and death. EC-IC bypass surgery and CEA + CAS should be considered as the choice of treatment based on operator's expertise and patient's anatomy. CAS may be employed as an alternative option in high surgical risk patients, especially when proximal ICA stump exists.

Combined Endovascular Antegrade and Direct Retrograde Carotid Artery Stenting for Chronic and Long Segment Common Carotid Artery Occlusion: Technical Note and Review of Literature

Common carotid artery (CCA) occlusion (CCAO) is a rare cause of ischemic stroke and bypass surgery is the common treatment approach. However, safer alternatives should be developed to treat CCAO. A 68-year-old male was diagnosed with left-sided CCAO with decreased left visual acuity due to neck radiation therapy for laryngeal cancer. Recanalization therapy using a pull-through technique was initiated because cerebral blood flow progressively decreased during the follow-up period. First, after a short sheath was inserted into the CCA, the occluded CCA was retrogradely penetrated through the sheath. Second, a micro-guidewire was guided to the aorta from the femoral sheath where it was caught using a snare wire guided from the cervical sheath. Subsequently, the micro-guidewire was gently pulled out from the cervical sheath, penetrated the occluded lesion, and was secured to the femoral and cervical sheaths. Finally, the occluded lesion was dilated using a balloon, and the stent was placed. Five days postprocedure, the patient was discharged uneventfully and exhibited improved left visual acuity. In terms of reliable penetration of obstructive lesions and reduction of embolic and hemorrhagic complications, combined endovascular antegrade and direct retrograde carotid artery stenting is a versatile and minimally invasive treatment option for CCAO.

Hybrid surgery recanalization for high-level chronic internal carotid artery occlusion

Objective

Although endovascular recanalization is considered a more effective treatment for chronic internal carotid artery occlusion (CICAO), the success rate of complex CICAO remains inadequate. We present hybrid surgery (carotid endarterectomy combined with carotid stenting) for complex CICAO and explore the influential factors and effects of hybrid surgery recanalization.

Methods

We retrospectively analyzed the clinical, imaging, and follow-up data of 22 patients with complex CICAO treated by hybrid surgery at the Zhongnan Hospital of Wuhan University from December 2016 to December 2020. We also summarize the technical points related to hybrid surgery recanalization.

Results

A total of 22 patients with complex CICAO underwent hybrid surgery recanalization. There were no postoperative deaths in all patients after hybrid surgery recanalization. Nineteen patients successfully underwent recanalization with a success rate of 86.4% and three cases with a failure rate of 13.6%. Patients were divided into success and failure groups. Significantly different radiographic classification of lesions was observed between the success group and the failure group (P = 0.019). The rates of CICAO with reverse ophthalmic artery blood flow in the internal carotid artery (ICA) preoperatively were 94.7% in the success group and 33.3% in the failure group (P = 0.038). Three cases of hybrid surgery recanalization failure were transferred for EC-IC bypass and had good neurological recovery. Postoperative average KPS scores of the 19 patients were improved compared to the preoperative ones (P < 0.001).

Conclusion

Hybrid surgery for complex CICAO is safe and effective with a high recanalization rate. The recanalization rate is related to whether the occluded segment surpasses the ophthalmic artery.

Short jump vein graft for the treatment of symptomatic Riles type 1A occlusion of common carotid artery: case report and review of literature

A 62-year-old man was presented with transient ischemic attack 1 day after percutaneous coronary intervention. Magnetic resonance imaging demonstrated fresh cerebral infarction in the left hemisphere. Digital subtraction angiography showed left Riles type 1A common carotid artery occlusion (CCAO). Blood flow in the internal carotid artery (ICA) was derived from the external carotid artery, which came through the anastomosis between the left occipital artery and a muscular branch of left vertebral artery. We performed short jump graft from CCA to ICA using saphenous vein, followed by ligation of CCA. The graft remained patent at the 1-year follow-up.

Segmented carotid endarterectomy for treatment of Riles type 1A common carotid artery occlusion

OBJECTIVE

Common carotid artery occlusion (CCAO) is a rare cause of cerebrovascular events. Symptomatic lesions are resistant to medical treatment and revascularization is often required, but there is no consensus on the treatment of CCAO at present. Riles type 1A CCAO is most likely to benefit from revascularization because it has patent outflow tract (internal carotid artery) which was supplied by patent external carotid artery (ECA) from collateral circulation. We described a novel surgical technique improved on the basis of the carotid endarterectomy (CEA) for treatment of Riles type 1A CCAO.

METHODS

We rigorously screened ten patients with symptomatic Riles type1A CCAO for surgery from January 2017 to May 2019 and performed a full preoperative assessment of the inadequate collateral circulation compensation. Moreover, we retrospectively reviewed our experience of the segmented CEA in the treatment of them in our single center.

RESULTS

Segmented CEA was performed on the left side in four cases and on the right side in six cases. The technical success rate of the procedure was 100%. Primary suture was used in nine cases. Only one patient (right CCAO) who had a history of neck radiotherapy was treated by the patch CEA. The mean temporary blocking time during surgery was 52.8 ± 9.15 min. The mean temporary blocking time for treating the upper segment of the common carotid artery (CCA) was 11.1 ± 2.64 min. In the postoperative period, cerebral perfusion on the ipsilateral site improved in all patients, myocardial infarction occurred in one patient, and recurrent laryngeal nerve damage occurred in another. No ischemic events or re-occlusion or restenosis (> 50%) of the treated CCA occurred during the mean follow-up of 32.6 ± 9.3 months. The preoperative mean modified Rankin Scale (mRS) score was 1.9 (range, 1-3; median, 2). At last follow-up for all patients, the mRS score was 1 (range, 0-3; median, 1).

CONCLUSION

Segmented CEA, which utilizes the compensatory effect of collateral circulation, is an effective and safe technique to treat patients suffering from Riles type 1A CCAO with hemodynamic cerebrovascular compromise.

Disobliteration of an Occluded Common Carotid Artery with Patent Bifurcation via Antegrade Ring Stripping

There is a lack of guidelines concerning common carotid artery (CCA) occlusive disease in the presence of a patent internal carotid artery (ICA). A novel surgical technique that disobliterates an occluded CCA was successfully performed in three cases. The detailed surgical steps are presented herein. After proximal division of the CCA behind the sternoclavicular junction, the occluded CCA was endarterectomized via antegrade ring stripping. After removal of the atheromatous core, the CCA was everted, and the wall remnants were cleaned under direct vision. Simultaneous eversion endarterectomy of the ICA was performed when necessary. After reversion of the CCA, it was transposed and anastomosed to the ipsilateral subclavian artery distal to the orifice of the vertebral artery. This novel technique can be used in selected cases by experienced surgeons.

Two cases of symptomatic common carotid artery occlusion treated by carotid endarterectomy with L-shaped ministernotomy

BACKGROUND

Common carotid artery occlusion (CCAO) is rare. Symptomatic lesions are resistant to medical treatment and revascularization are often required, but there is no consensus on the treatment of CCAO. In this paper, two cases of symptomatic CCAO treated by carotid endarterectomy (CEA) with L-shaped ministernotomy, in which the lesions extended to the beginning part of the CCA, are reported.

CASE DESCRIPTION

Case 1 involved a 74-year-old man who presented with transient left limb numbness and an abnormal right visual field. Cerebrovascular angiography showed that the right CCA was occluded immediately after its origin and blood was supplied from the posterior circulation. CEA was performed with an L-shaped ministernotomy that allowed exposure of the CCA origin with minimal invasion. There were no complications associated with the sternal incision and he was discharged with a modified Rankin Scale (mRS) score of 0. Case 2 involved a 70-year-old man who presented with left half-blindness. Magnetic resonance imaging showed infarction in the right posterior cerebral artery region and neck echo showed CCA pseudo occlusion just before the carotid bulb. A new infarction in the right middle cerebral artery region developed during hospitalization. CEA with partial sternotomy was performed. The patient was rehabilitated with no deterioration of neurological findings and transferred with an mRS score of 3.

CONCLUSION

There were no complications resulting from partial sternotomy in the two cases presented. CEA with partial sternotomy could be an effective treatment option for CCAO in which the internal carotid artery is patent and thrombus extends to the proximal CCA.

Dissection-related carotid-cavernous fistula (CCF) following surgical revascularization of chronic internal carotid artery occlusion: a new subtype of CCF and proposed management

BACKGROUND

The development of carotid-cavernous fistulas (CCFs) during surgical recanalization of chronic internal carotid artery occlusion (ICAO) may be secondary to severe ICA dissection rather than a focal tear of the cavernous ICA seen in typical traumatic CCFs. The purpose of this study is to investigate the causal relationship between the CCFs and severe ICA dissections and to characterize technical outcomes after treatment with stenting.

METHODS

Five patients underwent treatment with self-expanding stents due to intraprocedural CCF and ICA dissection following surgical removal of ICAO plaque. The stents were telescopically placed via true channel of the dissection. Safety of the procedure was evaluated with 30-day stroke and death rate. Procedural success was determined by the efficacy of CCF obliteration and ICAO recanalization with angiography.

RESULTS

All CCFs were associated with spiral and long segmental dissection from the cervical to cavernous ICA. After stenting, successful dissection reconstruction with TICI 3 was achieved in all patients, with complete (n = 4) or partial CCF (n = 1) obliteration. No patient had CCF syndrome, stroke, or death during follow-up of 6 to 37 months; but one patient had pulsatile tinnitus, which resolved 1 year later. Angiography at 6 to 24 months demonstrated CCF obliteration in all 5 patients and durable ICA patency in 4 patients.

CONCLUSIONS

Intraprocedural CCFs with spiral and cervical-to-cavernous ICA dissection during ICAO surgery are dissection-related because of successful obliteration after stenting for dissection reconstruction. Self-expanding stenting through true channel of the dissection, serving as implanting stent-autograft, may be an optimal therapy for the atypical CCF complication from ICAO surgery.

Interventional recanalization as a treatment of carotid stump syndrome caused by right internal carotid artery occlusion: A case report

RATIONALE

Carotid stump syndrome is a cerebral infarction caused by an embolus formed subsequent to the vortex of blood flow from the occluded stump, which then moves through the collateral vessels into the brain. The covered stent and stent-assisted coil embolization stump are the effective interventions for the carotid artery stump.

PATIENT CONCERNS

A 71-year-old man twice experienced left limb weakness; diffusion weighted imaging confirmed the diagnosis of cerebral infarction. Cervical computed tomography angiography, intracranial magnetic resonance angiography, and digital subtraction angiography were conducted to evaluate collateral circulation, intraluminal composition, and shape of the carotid stump.

DIAGNOSES

The patient was diagnosed with cerebral infarction and right carotid stump syndrome.

INTERVENTION

The patient underwent interventional recanalization of the occluded internal carotid artery, which relieved his symptoms and led to satisfactory therapeutic outcomes during the clinical follow-up.

OUTCOMES

A 9-month clinical follow-up revealed no stroke recurrence.

LESSONS

Interventional recanalization for the carotid artery stump syndrome is feasible. Accurate preoperative evaluation including collateral circulation, intraluminal composition, and shape of the carotid stump can assure a successful vascularization and guided management.

Ring-Stripping Retrograde Endarterectomy for Treatment of Common Carotid Artery Occlusion: A Minimally Invasive, Effective Procedure

BACKGROUND

To evaluate the efficacy and safety of in situ ring-stripping retrograde carotid endarterectomy (IS-RRCEA) in long-segment, symptomatic, chronic common carotid artery occlusion (CCAO).

METHODS

Thirty-nine patients (24 men; 15 women) with symptomatic chronic CCAO who underwent IS-RRCEA in our center were included retrospectively. The mean age of the men was significantly less than that of the women (59.6 ± 5.8 vs. 67.8 ± 6.3 years; P < 0.001). Risk factors, clinical characteristics, and CCAO classification of patients and effectiveness and safety of IS-RRCEA were analyzed.

RESULTS

Patients presented with the following symptoms: dizziness (6; 15.4%), transient ischemic attack (TIA; 33; 84.6%), and decreased vision (15; 38.5%). IS-RRCEA was performed on the left side in 25 (64.1%) cases and on the right side in 14 (35.9%) cases. The technical success rate of the procedure was 100%. Cerebral perfusion on the ipsilateral site improved in all patients. In the postoperative period, stroke and myocardial infarction occurred in one patient, and recurrent laryngeal nerve damage occurred in another; these patients' symptoms mostly resolved except for residual paresis in the stroke patient. Thirty-eight patients (97.4%) were followed for a mean of 29 ± 13.3 months after the IS-RRCEA; in 1-year follow-up, 31 patients (31/33; 93.9%) with preoperative TIA have had no TIAs; 2 patients (2/33; 6.1%) have fewer TIAs. Two patients (2/6; 33.3%) with preoperative dizziness have had no dizziness, and 4 (4/6; 66.7%) have had fewer episode of dizziness, no recurrent stenosis (>50%), or recognized occlusion.

CONCLUSIONS

Our single-center experience indicates that IS-RRCEA is an effective treatment for selected types of CCAO. Studies of the operation in larger populations with longer term follow-up should be conducted.

The working road map in a neurosurgical Hybrid Angio-Surgical suite------ development and practice of a neurosurgical Hybrid Angio-Surgical suite

Background

The concept of a Hybrid Angio-Surgical Suite (HASS) has emerged as a solution to the complexity of cerebrovascular surgery and the need for immediate intraoperative feedback. When to use it, what cases are suitable for its use, who can use it and how to use it remain debatable.

Objective

Provide the information regarding the application of the HASS for hospital, neurosurgeon and interventionalist.

Methods

We review the literatures of case reports and studies on the use of the hybrid angio-sugical suite along with application of HASS in our own practice.

Results

Indications for using HASS on different types of cerebral vascular disease, including cerebral aneurysm, AVM, DAVF, carotid and vertebral stenosis/occlusion, are addressed. The application of HASS for other non-cerebral vascular diseases, such as trauma, spine and skullbase cases, is reviewed and discussed.

Conclusion

HASS has made many surgical procedures safer and many difficult or previously untreatable conditions much more tractable and cost-effective. Other than used in cerebral vascular disease, HASS has much more applications, such as trauma, spine and other neurosurgical diseases.

Current understanding of chronic total occlusion of the internal carotid artery

At present, there is limited understanding of chronic total occlusion (CTO) of the internal carotid artery (ICA). Therefore, the present report collected related cases from PubMed and reviewed the literature. Cerebral vessels may form collateral circulation immediately or gradually following CTO of the ICA. The natural history of CTO of the ICA includes a variety of outcomes, all of which are biased toward a non-benign progressive process and are characterized by insufficient cerebral perfusion, embolus detachment and cognitive dysfunction. The majority of cases of CTO of the ICA require treatment. In early studies, the results of external-ICA bypass were unsatisfactory, while recanalization is now considered the only viable option. The current treatment indications mainly depend on the degree of injury to the cerebrovascular reserve and the extent to which the oxygen extraction fraction is increased. The length, height and duration of ICA occlusion are also relevant, though more frequently, the condition depends on multiple factors. Endovascular interventional recanalization, carotid endarterectomy (CEA) and hybrid surgery may be conducted in a select group of patients. As novel materials are developed, the success rate of simple recanalization may gradually increase; however, hybrid surgery may be more representative of the current trend, as advanced CEA can remove carotid atherosclerosis plaques, thus reducing the technological demands of the subsequent interventional recanalization. There are many complications that may result from recanalization following CTO of the ICA, including hyperperfusion and technical errors; therefore, the operation must be conducted carefully. If the recanalization is successful, it typically results in a stable improvement of patient condition in the long term. However, despite these conclusions, more studies are required in the future to further improve current understanding of CTO of the ICA.

Carotid-Carotid Artery Crossover Bypass with a Synthetic Vascular Graft for Symptomatic Type 1A Common Carotid Artery Occlusion

OBJECTIVE

To investigate the effect of carotid-carotid artery crossover bypass with a synthetic vascular graft for symptomatic type 1A common carotid artery occlusion (CCAO).

METHODS

A retrospective analysis was conducted of patients with symptomatic type 1A CCAO who underwent carotid-carotid artery crossover bypass surgery via a retropharyngeal route with a synthetic vascular graft in the Department of Neurosurgery at our hospital. Preoperative demographic data, surgical complications, incidence of stroke during follow-up, and other clinical data were summarized.

RESULTS

Between 2011 and 2016, carotid-carotid artery crossover bypass was performed with a synthetic vascular graft in 4 patients with type 1A CCAO. The mean patient age was 63.3 years (range, 49-69 years). Clinical symptoms included dizziness, amaurosis fugax, persistent limb numbness, and transient ischemic attack. In all 4 patients, postoperative computed tomography angiography showed internal carotid artery thickening due to successful bypass, whereas computed tomography perfusion showed improved postoperative cerebral perfusion on the side of the lesion. The sole perioperative complication was a complaint of foreign body sensation on swallowing in 1 patient. The mean duration of follow-up was 40.3 months (range, 14-77 months), during which no newly occurred cerebral ischemia or synthetic vascular graft occlusion was observed.

CONCLUSIONS

Carotid-carotid artery crossover bypass with a synthetic vascular graft is a safe and effective therapeutic approach for patients with symptomatic type 1A CCAO. However, studies with larger series are needed to enable more precise conclusions.

Endovascular Revascularization of a Symptomatic Common Carotid Artery Occlusion

Although the common carotid artery is the second most common site for extracranial carotid artery stenosis, complete symptomatic occlusion in the absence of devastating stroke is rare. We present a case of complete common carotid artery occlusion failing medical management and requiring endovascular intervention. The clinical presentation, diagnostic investigations, and management of complete carotid artery occlusions are discussed.

Common Carotid Artery Occlusion: A Single-Center Experience in 40 Cases

The incidence of common carotid artery occlusion (CCAO) is approximately 3% in patients who undergo angiography for symptomatic cerebrovascular disease; however, few studies have reported on management of this condition. The objective of this article was to analyze risk factors, therapeutic options, and clinical benefits of surgical treatment at a hospital in the city of São Paulo, Brazil. Data were collected from medical records of 40 patients with CCAO who were treated from June 2002 to October 2013. Results were analyzed retrospectively. Most of the patients were men (63.0%), who were significantly younger than women. Most of the participants had hypertension (90.0%), and more than half had a history of smoking (52.5%). The mean number of coexisting comorbidities/risk factors was 2.9 ± 1.0. Half of our sample had ipsilateral patent internal and external carotid artery, and 32.5% presented with an occluded internal carotid artery and a patent external artery. Patients with both an internal and an external occluded carotid artery (12.5%) were significantly older. Contralateral arteriosclerosis was observed in 65% of the patients, mainly represented by 50 to 90% stenosis. Most patients were symptomatic (67.5%), and hemiparesis was the most common symptom (55.0%) found. Most (77.5%) of the patients underwent the medical treatment; one out of three endovascular approaches failed. During the mean follow-up of 55 ± 43 months (range, 2-136 months), 17.5% of the patients died within 4 days after surgical repair and after along 123 months of clinical follow-up. Coexisting comorbidities/risk factors were significantly associated with fatal outcomes, such as acute myocardial infarction. This study provides scientific evidences on treatment and outcomes of CCAO.

Hybrid treatment of symptomatic chronic isolated carotid bifurcation

Total chronic occlusion of the common carotid artery with patent internal and external carotid arteries can induce cerebral embolism and hypoperfusion. We report a hybrid approach that was used to treat 2 patients presented with symptomatic chronic occlusion of the common carotid artery and ipsilateral internal carotid stenosis. Antegrade recanalization and retrograde stenting of the common carotid artery was performed in both patients associated to carotid bulb endarterectomy. Fresh thrombus observed in the distal common carotid stump was responsible for the embolic cerebral lesions and patients' previous symptoms. Patients remain asymptomatic at the 23rd- and 18th-month follow-up, respectively.

Common carotid artery occlusion: a case series

Subjects and Methods. We analysed 5000 cerebrovascular ultrasound records. A total of 0.4% of the patients had common carotid artery occlusion (CCAO). Results. The mean age was 59.8 ± 14.2 years, and the male/female ratio was 2.33. The most frequent risk factors were hypertension, ischaemic heart disease, dyslipidemia, diabetes mellitus, and smoking. Right-sided and left-sided CCAO occurred in 65% and 30% of the cases, respectively, and bilateral occlusion was detected in one case (5%). Patent bifurcation was observed in 10 cases of CCAO in which the anterograde flow in the ICA was maintained from the external carotid artery with reversed flow. In two of the cases, the occluded CCA was hypoplastic. The aetiology of CCAO in the majority of cases was the atherosclerosis (15 cases). The male/female ratio was higher in the patients with occluded distal vessels, and the short-term outcome was poorer. Only two cases from this series underwent revascularisation surgery. Spontaneous recanalisation was observed in one case. Conclusions. The most frequent cause of CCAO was atherosclerosis. The outcome is improved in the cases with patent distal vessels, and spontaneous recanalisation is possible. Treatment methods have not been standardised. Surgical revascularisation is possible in cases of patent distal vessels, but the indications are debatable.

Common carotid artery occlusion treatment: revealing a gap in the current guidelines

OBJECTIVE

To review the literature on the management of common carotid artery occlusion (CCAO).

METHODS

A review of English-language medical literature from 1965 to 2012 was conducted using the PubMed and EMBASE databases to find all studies involving management of CCAO. The search identified 21 articles encompassing 146 patients/arteries (73.2% men; mean age 65 ± 6.9 years).

RESULTS

The majority of the patients (93.8%) were symptomatic. Most of the patients (61.5%) had ipsilateral internal carotid artery (ICA) and external carotid artery (ECA) patent, while an occluded ICA and a patent ECA were found in 26.6% of the patients. Eighty per cent of the patients treated underwent a surgical bypass procedure, with the subclavian artery as the most common inflow vessel (64.1%). During the first 30 days of the procedure two strokes (1.5%) were reported. During a follow-up period spanning an average of 25.6 ± 11.2 months nine patients (6.6%) experienced a clinical cerebrovascular event. Seven restenoses (5.1%) and two reocclusions (1.5%) also occurred-eight after open surgical and one after endovascular repair.

CONCLUSION

The necessity to intervene to a CCAO remains controversial. This review shows that open surgical management of symptomatic CCA occlusive disease is a safe, durable, and effective therapeutic strategy with low perioperative cerebrovascular morbidity.