Extracranial-intracranial Bypass Surgery Research Articles

The use and abuse of survival analysis and Kaplan-Meier curves in surgical trials

BackgroundSurvival analysis based on Cox regression and Kaplan-Meier curves, initially devised for oncology trials, have frequently been used in other contexts where fundamental statistical assumptions (such as a constant hazard ratio) are not satisfied. This is almost always the case in trials that compare surgery with medical management. MethodsWe review a trial that compared extracranial-intracranial bypass surgery (EC-IC bypass) with medical management (MM) of patients with symptomatic occlusion of the carotid or middle cerebral artery, where it was claimed that surgery was of no benefit. We discuss a hypothetical study and review other neurovascular trials which have also used survival analysis to compare results. ResultsThe trial comparing EC-IC bypass and MM did not satisfy the fundamental proportional hazard assumption necessary for valid analyses. This was also the case for two prior EC-IC bypass trials, as well as for other landmark neurovascular studies, such as the trials comparing endarterectomy with MM for carotid stenoses, or for the trial that compared intervention and MM for unruptured brain arteriovenous malformations. While minor deviations may have little effect on large trials, it may be impossible to show the benefits of surgery when trial size is small and deviations large. ConclusionSurvival analyses are inappropriate in RCTs comparing surgery with conservative management, unless survival is calculated after the postoperative period. Alternative ways to compare final clinical outcomes, using for example a fixed follow-up period, should be planned for preventive surgical trials that compare intervention with conservative management.

Surgical and endovascular cerebral revascularization for cerebral vasculitis with inflammatory vessel stenosis: a case series

Autoimmune vasculitides affect the cerebral vasculature significantly in a considerable number of cases. When immunosuppressive treatments fail to prevent stenosis in cerebral vessels, treatment options for affected patients become limited. In this case series, we present four cases of pharmacoresistant vasculitis with recurrent transient ischemic attacks (TIAs) or stroke successfully treated with either extracranial-intracranial (EC-IC) bypass surgery or endovascular stenting. Both rescue treatments were effective and safe in the selected cases. Our experience suggests that cases of pharmacoresistant cerebral vasculitis with recurrent stroke may benefit from rescue revascularization in combination with maximum medical management.

Abstract TMP71: The Association Between Improvement of Headache and Cerebrovascular Reactivity After Revascularization Surgery in Moyamoya Arteriopathy

Background and aim: Significant headache is often reported by patients with moyamoya arteriopathy (MMA) but has a poorly understood pathophysiology. To decide on management, physicians often focus on stroke-like symptoms while the impact on quality of life and economic burden of chronic headache is often overlooked. We aimed to investigate the effect of revascularization surgery on headache in MMA and potential association with cerebrovascular reactivity (CVR). Methods: This was a single-center retrospective study in adult patients with MMA, who underwent extracranial-intracranial (EC-IC) bypass surgery between Jan 2010 - Sept 2022 and had CVR-MRI performed. Clinical and imaging data were collected through systematic chart review complemented by structured headache questionnaires. We assessed the association between headache and CVR before and after revascularization surgery along with potential predictors using logistic regression analysis. Results: Fifty-nine patients were included (mean age 44±13 years, 42 women (71%)). Thirty-seven patients (63%) had bilateral MMA of whom 19 (51%) had bilateral EC-IC bypass surgery. Thirty-eight patients (64%) reported headache pre-surgery with mostly migraine-like features. More than a third of patients (37%) lost workdays or quit their job because of headache. Headache improved in 26/38 (68%) patients post-surgery with a reduction in pain severity (median VAS 6 to 3; p = 0.005) and sick leave (37% to 8%; p<0.001). CVR improved in 33/43 (77%) patients who had pre- and post-surgery CVR-MRI, which was associated with headache improvement (OR:14; 95% CI:1.4-131). Pre-operative headache severity (VAS-score) was an independent predictor for headache improvement post-surgery (OR:1.7; 95% CI:1.2-2.5). Conclusions: Results of this study showed improvement of headache in most patients with MMA after revascularization surgery and association with improvement in CVR, supporting the hypothesis of a vascular origin. Future larger cohort studies should confirm this hypothesis, improve understanding of underlying pathophysiology and identify potential future treatment targets to guide management for this underappreciated yet disabling aspect of MMA.

Abstract WP127: Diagnostic Value of the Ivy Sign Compared to MR With Cerebrovascular Reactivity in Decompensated Moyamoya Arteriopathy

Introduction: MR cerebrovascular reactivity (CVR) mapping during rapid manipulation of end-tidal pCO2 is used to assess hemodynamic compromise in patients with Moyamoya arteriopathy (MMA). Leptomeningeal ivy sign on MRI FLAIR sequence may indicate regions of decreased perfusion, which would be an inexpensive and easy way to screen for hemodynamic compromise. The purpose of this study was to examine the diagnostic value of the ivy sign compared to MR CVR. Methods: For this retrospective cross-sectional study, we included consecutive patients with uncompensated MMA who were eligible for extracranial-intracranial bypass surgery and completed a preoperative MRI FLAIR with CVR study. Patients with incomplete or artefact degraded imaging were excluded. Two neuroradiologists who were blinded for the CVR result independently assessed the degree of ivy sign on axial 2D FLAIR imaging as grade 0, 1 or 2 in 8 predefined brain regions. Two different readers, blinded for ivy sign, independently assessed the presence or absence of steal in the same regions on MR CVR. Consensus was reached for discordant findings. We assessed interrater agreement using weighted kappa followed by diagnostic accuracy measures for the ivy sign using MR CVR as a reference. Results: We enrolled 73 patients (41/73 (56.1%) female; mean age 43). 47/73 (64%) patients had bilateral MMA with on average 3 brain regions with abnormal CVR. Interrater agreement was good for ivy sign (weighted kappa 0.63 (95%CI 0.54-0.71)) and excellent for CVR (kappa 0.95 (95% CI 0.87-1.00)). For a total of 156/584 (26.7%) brain regions, there was agreement between a positive ivy sign and the presence of steal on CVR and 240/584 (41%) brain regions had no ivy sign and normal CVR. The sensitivity of the ivy sign was 64.5%, specificity 70.2%, positive predictive value 60.5% and negative predictive value 73.6% with an AUC of 0.68 (95% CI 0.64-0.72) Conclusions: In this preselected cohort with high pretest probability for hemodynamic compromise, the diagnostic accuracy of the ivy sign compared to MR CVR was limited and needs to be used with caution to determine haemodynamic status in MMA.

Spontaneous development and involution of a de novo pseudoaneurysm at the superficial temporal artery-middle cerebral artery bypass anastomotic site in a patient with moyamoya disease: illustrative case.

De novo pseudoaneurysm formation is a rare complication of extracranial-intracranial bypass surgery. The authors report the case of a 28-year-old male who presented with new-onset right temporal and occipital ischemia who was found to have bilateral proximal internal carotid artery occlusion with collateral vasculature formation consistent with moyamoya disease. The patient underwent bilateral superficial temporal artery-middle cerebral artery bypasses. A de novo pseudoaneurysm was found at the left-sided bypass distal anastomotic site recipient vessel 1 month after the surgery. The pseudoaneurysm demonstrated a progressive reduction in size and eventual complete involution at 6 months after surgery. Limited literature reports extracranial-intracranial bypass-associated aneurysms treated primarily with either clipping or resection and reanastomosis. The authors demonstrate, for the first time, a progressively benign natural history course of an extracranial-intracranial bypass distal anastomotic site pseudoaneurysm.

Extracranial-Intracranial Bypass and Risk of Stroke and Death in Patients With Symptomatic Artery Occlusion

Prior trials of extracranial-intracranial (EC-IC) bypass surgery showed no benefit for stroke prevention in patients with atherosclerotic occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA), but there have been subsequent improvements in surgical techniques and patient selection. To evaluate EC-IC bypass surgery in symptomatic patients with atherosclerotic occlusion of the ICA or MCA, using refined patient and operator selection. This was a randomized, open-label, outcome assessor-blinded trial conducted at 13 centers in China. A total of 324 patients with ICA or MCA occlusion with transient ischemic attack or nondisabling ischemic stroke attributed to hemodynamic insufficiency based on computed tomography perfusion imaging were recruited between June 2013 and March 2018 (final follow-up: March 18, 2020). EC-IC bypass surgery plus medical therapy (surgical group; n = 161) or medical therapy alone (medical group; n = 163). Medical therapy included antiplatelet therapy and stroke risk factor control. The primary outcome was a composite of stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years after randomization. There were 9 secondary outcomes, including any stroke or death within 2 years and fatal stroke within 2 years. Among 330 patients who were enrolled, 324 patients were confirmed eligible (median age, 52.7 years; 257 men [79.3%]) and 309 (95.4%) completed the trial. For the surgical group vs medical group, no significant difference was found for the composite primary outcome (8.6% [13/151] vs 12.3% [19/155]; incidence difference, -3.6% [95% CI, -10.1% to 2.9%]; hazard ratio [HR], 0.71 [95% CI, 0.33-1.54]; P = .39). The 30-day risk of stroke or death was 6.2% (10/161) in the surgical group and 1.8% (3/163) in the medical group, and the risk of ipsilateral ischemic stroke beyond 30 days through 2 years was 2.0% (3/151) and 10.3% (16/155), respectively. Of the 9 prespecified secondary end points, none showed a significant difference including any stroke or death within 2 years (9.9% [15/152] vs 15.3% [24/157]; incidence difference, -5.4% [95% CI, -12.5% to 1.7%]; HR, 0.69 [95% CI, 0.34-1.39]; P = .30) and fatal stroke within 2 years (2.0% [3/150] vs 0% [0/153]; incidence difference, 1.9% [95% CI, -0.2% to 4.0%]; P = .08). Among patients with symptomatic ICA or MCA occlusion and hemodynamic insufficiency, the addition of bypass surgery to medical therapy did not significantly change the risk of the composite outcome of stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years. ClinicalTrials.gov Identifier: NCT01758614.

Extracranial-Intracranial Bypass Surgery for Stroke Prevention

Extracranial-Intracranial Bypass Surgery for Stroke Prevention

Maxillary Nerve as Landmark for Exposure of the Internal Maxillary Artery in Extracranial-Intracranial Bypass Surgery

To establish a new method for fast exposure of the internal maxillary artery (IMA) during extracranial-intracranial bypass surgery. To explore the positional relationship between the IMA and the maxillary nerve and pterygomaxillary fissure, 11 formalin-fixed cadaveric specimens were dissected. Three bone windows of the middle fossa were created for further analysis. Then the IMA length that could be pulled up above the middle fossa was measured after different degrees of removal of bony structure. The IMA branches under each bone window were also explored in detail. The top of the pterygomaxillary fissure was located 11.50 mm anterolateral to the foramen rotundum. The IMA could be identified just inferior to the infratemporal segment maxillary nerve in all specimens. After drilling of the first bone window, the IMA length that could be pulled above the middle fossa bone was 6.85 mm. After drilling of the second bone window and further mobilization, the IMA length that could be harvested was significantly longer (9.04 mm vs. 6.85 mm; P < 0.001). Removal of the third bone window did not significantly improve the IMA length that could be harvested. The maxillary nerve could be used as a reliable landmark for the exposure of the IMA in the pterygopalatine fossa. With our technique, the IMA could be easily exposed and sufficiently dissected without zygomatic osteotomy and extensive middle fossa floor removal.

623 Improving Access to Extracranial-Intracranial Bypass Surgery in Border Hispanic Communities Utilizing Collaborative Approach Between Plastics and Neurological Surgery

INTRODUCTION: Hispanic patients such as those with Moyamoya disease are less likely to receive surgical revascularization therapy due to inequities in access (1). Our institution is a located in the Southern Texas-Mexico border region serving a largely Hispanic population. We previously referred patients for EC-IC bypass to other quaternary-care centers in Texas. While referrals were already challenging due to distance, mixed immigration status, and poor socioeconomic background of many patients; COVID-19 further exacerbated this problem with restriction of elective surgical volume. METHODS: A consecutive series of EC-IC bypasses performed by authors (SKD and MDLG) were retrospectively reviewed. Baseline clinical, perioperative radiographic, and post-operative outcomes were studied. All patients were offered option of a referral to a quaternary-care centers and also given local option for performing bypass surgery. Further, patients met preoperatively with both the plastic and neurological surgeon. Ultimately, decision was made by patient. RESULTS: A total of 6 craniotomies for EC-IC bypass were performed during the study period. The diagnoses included Moyamoya in 5 cases and symptomatic intracranial atherosclerosis in one. All patients were Hispanic, female, and nonsmokers with mean age of 35.6 years. Mean preoperative HBa1c was 7.9, preoperative LDL was 82, and mean preoperative hemoglobin was 11.3. Direct bypass was performed in 40% of cases. Mean OR time was 3 hours and 7 minutes. CONCLUSIONS: We have found collaboration between plastic and neurological surgery for surgical revascularization is feasible and improved access to care for Hispanic Moyamoya disease patients residing in a border community. References 1) Chiu R, Chaker A, McGuire LS, et al. “Socioeconomic Inequities in the Surgical Management of Moyamoya Disease.” World Neurosurg. 2021 Nov; 155: e188-e195.

393 Sonolucent Cranioplasty for Real-Time Ultrasound Monitoring of Extra-to-Intracranial Bypass: Early Multicenter Experience of 44 Cases

INTRODUCTION: The new sonolucent cranioplasty implant (clear polymethyl methacrylate, PMMA) adds functionality besides reconstruction during and after surgery. One possible application uses transcranioplasty ultrasound (TCUS) technique after PMMA cranioplasty to assess graft patency of extracranial-intracranial (EC-IC) bypass procedures. METHODS: Multicenter analysis of consecutive EC-IC bypass patients from 5 US centers between 2019-2022 with closure post bypass using the translucent PMMA cranioplasty implant. RESULTS: Forty-four patients (median-age 53, 68.2% females) were included. The most common indication for bypass was Moyamoya disease/syndrome (77.3%) and superficial temporal artery to middle cerebral artery (STA-MCA) bypass was the most common procedure (79.5%). Pre-treatment modified Rankin Scale of 0 and 1-2 was noted in 11.4% and 59.1% of the patients, respectively, with hypertension being the most common comorbidity (72.7%). Intraoperative imaging for bypass patency involved utilizing combination of modalities in all patients, with intraoperative doppler being the most commonly utilized monitoring modality (90.9%) followed by indocyanine green (ICG) and catheter angiography (86.4% and 61.4%, respectively). Qualitative TCUS assessment of the graft patency was feasible in all cases without technical difficulties. Post-operative inpatient TCUS confirmation of the bypass patency was recorded in 56.8% of the cases, and outpatient TCUS surveillance for monitoring bypass patency through the implant was recorded in 22.7% of the patients. There were no cases of bypass failure noted in this cohort necessitating retreatment. Similarly, no implant-related complications were encountered in the cohort. Major complications requiring additional surgery occurred in 2 patients (4.6%) including epidural hematoma requiring surgical evacuation (2.3%) and post-operative surgical site infection (2.3%) that was unrelated to the implant. CONCLUSIONS: This multicenter study supports the safety and feasibility of using the sonolucent PMMA implant in the setting of EC-IC bypass surgery with the goal to monitor bypass patency using TCUS.

Sonolucent Cranioplasty in Extracranial to Intracranial Bypass Surgery: Early Multicenter Experience of 44 Cases.

The new sonolucent cranioplasty implant (clear polymethyl methacrylate, PMMA) adds functionality besides surgical reconstruction. One possible application uses the transcranioplasty ultrasound (TCUS) technique after PMMA cranioplasty to assess graft patency of extracranial-intracranial (EC-IC) bypass procedures. To report our early multicenter experience. This is a multicenter analysis of consecutive EC-IC bypass patients from 5 US centers (2019-2022) with closure postbypass using PMMA implant. Forty-four patients (median age 53 years, 68.2% females) were included. The most common indication for bypass was Moyamoya disease/syndrome (77.3%), and superficial temporal artery to middle cerebral artery bypass was the most common procedure (79.5%). Pretreatment modified Rankin Scales of 0 and 1 to 2 were noted in 11.4% and 59.1% of patients, respectively. Intraoperative imaging for bypass patency involved a combination of modalities; Doppler was the most used modality (90.9%) followed by indocyanine green and catheter angiography (86.4% and 61.4%, respectively). Qualitative TCUS assessment of graft patency was feasible in all cases. Postoperative inpatient TCUS confirmation of bypass patency was recorded in 56.8% of the cases, and outpatient TCUS surveillance was recorded in 47.7%. There were no cases of bypass failure necessitating retreatment. Similarly, no implant-related complications were encountered in the cohort. Major complications requiring additional surgery occurred in 2 patients (4.6%) including epidural hematoma requiring evacuation (2.3%) and postoperative surgical site infection (2.3%) that was believed to be unrelated to the implant. This multicenter study supports safety and feasibility of using sonolucent PMMA implant in EC-IC bypass surgery with the goal of monitoring bypass patency using TCUS.

MR vessel-encoded arterial spin labeling with the placement of metallic items to visualize the territorial blood flow after extracranial-intracranial bypass surgery: a proof-of-concept study.

Depiction of bypass blood flow in patients who received extracranial-intracranial (EC-IC) bypass surgery is important for patient care. To develop a vessel-encoded arterial spin labeling (VE-ASL) method using surgical staples as a magnetic resonance (MR)-conditional product in patients who received EC-IC bypass surgery. Pseudo-continuous labeling was used for VE-ASL acquisition with a 3-T MR unit. First, an experimental study was conducted to determine the appropriate number of surgical staples to obtain a spatially sufficient saturation effect. Thereafter, four healthy normal volunteers underwent a VE-ASL study to confirm the sufficiency of the saturation effect to the right or left common carotid artery. Finally, VE-ASL scanning was performed in seven patients after EC-IC bypass surgery to confirm the ability of VE-ASL to visualize the territorial bypass perfusion. All qualitative evaluation was performed by two neuroradiologists using a 3-point grading system (2 = good, 1 = moderate, 0 = poor). A quantity of 200 staples was found to be appropriate for VE-ASL scanning. In healthy volunteers, one neuroradiologist rated the images of all four cases as good, while the other rated three cases as good and one case as moderate. For the seven patients after EC-IC bypass surgery, one neuroradiologist rated all seven cases as good, and the other rated six cases as good and one case as moderate. VE-ASL using surgical staples might be useful for the evaluation of territorial bypass perfusion in patients after EC-IC bypass surgery.

True superficial temporal artery aneurysm: A case after extracranial-intracranial bypass surgery and a systematic review.

Nontraumatic true superficial temporal artery aneurysm (STAA) is rare, and its characteristics and pathogenesis are unclear. We report a case of STAA and performed a systematic review of PubMed, Scopus, and Web of Science using the keyword "superficial temporal artery aneurysm" to include studies on STAA reported through July 2022. We excluded studies on STAA associated with trauma, arterial dissection, infection, or vasculitis. A 63-year-old woman who underwent left superficial temporal artery (STA)-middle cerebral artery bypass surgery 8 years previously was diagnosed with an aneurysm located at the left STA. The blood flow volume estimated by ultrasonography was higher in the left STA than in the contralateral counterpart (114 mL/min vs. 32 mL/min). She underwent clipping surgery to prevent aneurysmal rupture without sequela. The lesion was diagnosed as a true aneurysm by histology. The systematic review identified 63 cases (including the present case) of nontraumatic true STAA. The median age of the patients was 57 (interquartile range [IQR]: 41-70) years. Most (90.5%) cases were detected as a palpable mass. Aneurysmal rupture occurred in only 1 (1.6%) case, despite the large size of aneurysms (median size: 13 [IQR: 8-20] mm) and the high frequency (33.3%) of aneurysmal growth during observation. Most (93.7%) patients underwent surgical resection of STAA without sequela. Our findings suggest that the pathogenesis of true STAA is promoted by hemodynamic stress. The systematic review clarified patients' and aneurysmal characteristics and treatment outcomes, providing further insight into the pathogenesis of nontraumatic true STAA.

Evidence of STA-MCA Bypass-History and Overseas Articles

The superficial temporal artery to middle cerebral artery(STA-MCA)bypass technique developed by M. Gazi Yaşargil and Raymond M. P. Donaghy in the 1960s was rapidly adopted throughout the world as a procedure for surgical flow augmentation for ischemic cerebrovascular disease(CVD). However, the effectiveness of STA-MCA bypass for atherosclerotic occlusive CVD has not been proven in the extracranial-intracranial(EC-IC)bypass and carotid occlusion surgery studies(COSS), both conducted in the United States. Subsequently, the number of STA-MCA bypasses performed for atherosclerotic CVD decreased globally. In contrast, the Japanese EC-IC Bypass Trial demonstrated the efficacy of STA-MCA bypass for occlusive CVD. The number of research articles reassessing bypass surgery with appropriate indications and high quality of care has recently increased, and carotid and middle cerebral artery occlusion surgery studies designed with careful consideration for several criticisms against COSS are now being conducted in China. This article reviews foreign papers related to STA-MCA bypass for atherosclerotic CVD and describes the current consensus regarding both surgical and medical treatment.

Pseudo-continuous arterial spin labeling with short post-labeling delay time sensitively reflects the hemodynamics of symptomatic patients with permanent large vessel occlusion before and after revascularization.

This study evaluated the feasibility of arterial spin labeling (ASL) for diagnosing hemodynamic stroke due to permanent anterior circulation large vessel occlusion. Three-dimensional pseudo-continuous ASL data at two post-labeling delay (PLD) times (1.5 and 2.5s) in patients with unilateral permanent middle cerebral artery (MCA) segment 1 (M1) or internal cerebral artery (ICA) occlusion were acquired during routine magnetic resonance angiography. Sixty-one patients with symptomatic occlusion (M1, 24; ICA, 37) and 69 patients with asymptomatic occlusion (M1, 21; ICA, 48) were enrolled. Regions of interest were automatically placed in the MCA region using a template. The respective scans were compared with asymptomatic M1 or ICA occlusion scans. The ratio of signal intensity (occlusion side/non-occlusion side) in the perfusion area of MCA (asymmetry index [AI]) was compared between both groups. In both PLD groups, AI was significantly lower in symptomatic patients than in asymptomatic patients. The receiver operating characteristic curve showed moderate capacity for the prediction of symptomatic AI in both groups (area under the curve, 0.739 and 0.712, respectively). As a result of extracranial-intracranial bypass operation in 28 symptomatic (M1, eight; ICA, 20) patients, AI was significantly higher postoperatively in the PLD 1.5s group than in the PLD 2.5s group. In symptomatic patients with permanent large vessel occlusion, the signal intensity ratio of pseudo-continuous ASL with short PLD sensitively reflects the hemodynamics before and after revascularization; therefore, this technique may be an alternative method in situations where PET or SPECT cannot be performed.

Bypass Surgery Management of Complex Proximal and Distal Posterior Inferior Cerebellar Artery Aneurysms.

For the complex posterior inferior cerebellar artery (PICA) aneurysms, standard microsurgical or endovascular technical options were not feasible. To determine the efficacy and outcomes of bypass surgery for complex PICA aneurysms, the authors herein review our recent surgical experience for complex PICA aneurysms. The authors retrospectively reviewed our experience of extracranial-intracranial bypass and intracranial-intracranial bypass surgery in treatment of proximal and distal complex PICA aneurysms at our institution from 2016 to 2020. Twelve patients harboring 12 complex PICA aneurysms received bypass surgery at our institution. Seven (58.3%) patients with proximal PICA aneurysms underwent extracranial-intracranial bypass. Five (41.7%) patients with distal PICA aneurysms accepted intracranial-intracranial bypass. The postoperative symptom improvement: Of the 6 patients with preoperative hypoperfusion or ischemic of the cerebellar hemisphere, the symptom resolved in 5 patients, improved in 1 patient, of 5 patients with preoperative mass effect, the symptom resolved in 5 patients. During the follow-up period, ten patients had a modified Rankin scale (mRS) score of 0 to 1, and 1 patient had an mRS score of 2. One patient had an mRS score of 3. The long-term graft patency rate was 91.7%. All patients had no recurrence of intracranial aneurysm. Base on the complexity of anatomy structure and the vascular architecture, an individualized strategy was proposed for each patient. The use of different types of bypass procedures (occipital artery-PICA end-to-end bypass, PICA-PICA end-to-end anastomosis, and/or occipital artery graft) can safely and effectively manage these complex PICA aneurysms.

Ischemic Stroke Revascularization.

Extracranial-intracranial (EC-IC) bypass is one of the most fundamental techniques for ischemic cerebrovascular disease (CVD). We describe the standard surgical strategies, advanced techniques, and controversies concerning revascularization of ischemic stroke. The standard surgical strategies and techniques emphasize how to determine surgical indication, which should be decided for symptomatic internal carotid artery or middle cerebral artery (MCA) occlusive disease with misery perfusion detected by quantitative single photon emission computed tomography. Advanced techniques are available for complex situations such as posterior circulation revascularization, Bonnet bypass for common carotid artery obstruction, and various EC-IC bypasses for ischemia in the MCA and/or anterior cerebral artery territories using inter-grafts such as femoral veins and radial arteries, illustrated by our surgical results and experiences. Controversies include endovascular treatment complementary to EC-IC bypass. Finally, we advocate emergent EC-IC bypass for progressive ischemic CVD, particularly for contraindication or unsuccessful treatment after intravenous tissue plasminogen activator administration and/or endovascular thrombolysis. EC-IC bypass surgery can be reliable for ischemic CVD under strict optimal surgical indications using safe and reliable surgical techniques.

Horizontal stent deployment via extracranial-intracranial bypass in coil embolization of basilar apex aneurysms: technical report.

The endovascular treatment of large, wide-necked basilar apex aneurysms (BAAs) remains challenging. Although horizontal stent deployment across both P1 segments of the posterior cerebral arteries (PCAs) would be an optimal strategy in coil embolization of wide-necked BAAs, this is only feasible in cases with anatomically favorable access. In rare circumstances, large-diameter conduits of extracranial-intracranial (EC-IC) bypass can also provide a good access route for endovascular treatment of complex intracranial aneurysms. We describe the technique of accessing the PCA via EC-IC bypass grafts and deploying a stent horizontally across the neck of BAA and its coil embolization. We provide a detailed technical review and describe some pitfalls of the procedure. Two patients underwent EC-IC bypass surgery prior to the treatment of a large, wide-necked BAA. The radial artery and saphenous vein were used as grafts, respectively. To facilitate coil embolization for a large BAA, a PCA-to-PCA horizontal stent was deployed via the bypass graft. Trans-cell and jailing techniques were used, respectively. Both aneurysms were completely occluded, and the patients were discharged without any neurological deficit. Horizontal stent deployment via EC-IC bypass grafts can be performed safely, providing proper closure of the aneurysmal neck and apposition to both PCAs, facilitating complete coil embolization.

Evaluation of Revascularization in Different Suzuki Stages of Ischemic Moyamoya Disease by Whole-Brain CT Perfusion.

Objective: This study compared the clinical features and hemodynamic characteristics of patients in different Suzuki stages of ischemic moyamoya disease (iMMD) before and after treatment with extracranial-intracranial (EC-IC) bypass surgery combined with encephalo-duro-myo-synangiosis and whole-brain computed tomography perfusion (WB-CTP).Methods: A total of 126 patients in different Suzuki stages (II, III, IV, and V) of iMMD who underwent bypass surgery from April 2013 to August 2020 were included in this retrospective study. MIStar automatic analysis of Whole brain CT perfusion imaging software (WB-CTP, Apollo Medical Imaging Technology, Melbourne, Australia) was used. The patients also underwent WB-CTP 1 day before and 1 week and 3 months after the surgery. The relationships between hemodynamic parameters in WB-CTP including delay time (DT) > 3 s, relative cerebral blood flow (rCBF) < 30%, mismatch and mismatch ratio, and clinical outcomes were evaluated for different Suzuki stages, with comparisons between early (II and III) and late (IV and V) stages.Results: Combined bypass surgery was performed in 161 hemispheres of 126 patients with iMMD. Brain volume with DT > 3 s was decreased 1 week (51.5 ± 11.8 ml, P < 0.05) and 3 months (41.5 ± 10.7 ml, P < 0.05) after bypass compared to 1 day before bypass (104.7 ± 15.1 ml) in early-stage patients. In late-stage patients, the volume was increased 1 week after bypass compared to the preoperative value (154.3 ± 14.7 vs. 118.3 ± 19.1 ml, P < 0.05). Preoperative brain volume with rCBF < 30% was lower (9.8 ± 3.9 vs. 33.5 ± 11.0 ml) whereas preoperative mismatch ratio was higher (11.2 ± 2.8 vs. 3.6 ± 1.6) in early-stage as compared to late-stage patients (both P < 0.05). A higher modified Rankin scale score (0–1) was achieved by early-stage patients than by those in the late stage (93.8 vs. 80.4%, P < 0.05) at the 3-month follow-up.Conclusions: WB-CTP is useful for assessing the effectiveness of combined bypass/revascularization in different Suzuki stages of iMMD. Patients in the early stage of disease with higher preoperative brain volume with DT > 3 s and mismatch ratio show greater improvements in hemodynamic parameters and fewer postoperative complications associated with hemodynamic disturbance following bypass than patients in the late stage. Preoperative mismatch ratio can serve as a marker for assessing the status of collateral circulation in different Suzuki stages of iMMD.

Efficacy and Safety of Emergency Extracranial–Intracranial Bypass for Revascularization within 24 Hours in Resolving Large Artery Occlusion with Intracranial Stenosis

Endovascular treatment (EVT) is less effective for intracranial atherosclerosis-induced emergent large vessel occlusion. Extracranial-intracranial (EC-IC) bypass surgery is a possible treatment option to augment cerebral blood flow in the perfusion defect area. We compared the efficacy and safety of EC-IC bypass surgery with those of EVT and maximal medical treatment for acute ischemic stroke. The data from 39 patients, for whom vessel revascularization had failed despite mechanical thrombectomy, were retrospectively analyzed. Of the 39 patients, 22 had undergone percutaneous transluminal angioplasty or intracranial stenting (PTA/S), 10 had undergone emergency EC-IC bypass surgery within 24 hours of symptom onset, and 7 had received maximal medical treatment (MMT) only. The patency, perfusion status, and postoperative infarct volume were evaluated. The clinical outcomes were assessed at 6 months postoperatively using the modified Rankin scale. The mean reperfusion time was significantly longer for the EC-IC bypass group (14.9 hours) compared with that in the PTA/S group (4.1 hours) and MMT group (7.5 hours; P < 0.05). The postoperative infarct volume on diffusion-weighted magnetic resonance imaging was significantly lower in the emergency EC-IC bypass group (11.3 cm3) than in the MMT group (68.0 cm3) but was not significantly different from that of the PTA/S group (14.0 cm3; P < 0.05). The proportion of patients with a modified Rankin scale score of 0-2 at 6 months after surgery was significantly higher in the EC-IC bypass group (80%) than in the PTA/S (59%) and MMT (14%) groups (P < 0.05). Emergency EC-IC bypass surgery is an effective and safe treatment option for intracranial atherosclerosis-induced acute ischemic stroke for which EVT is inadequate.