Emergency Extracranial-Intracranial Bypass to Revascularize Salvageable Brain Tissue in Acute Ischemic Stroke Patients

FDA-approved machine learning algorithms in neuroradiology: A systematic review of the current evidence for approval

Over the past decade, machine learning (ML) and artificial intelligence (AI) have become increasingly prevalent in the medical field. In the United States, the Food and Drug Administration (FDA) is responsible for regulating AI algorithms as "medical devices" to ensure patient safety. However, recent work has shown that the FDA approval process may be deficient. In this study, we evaluate the evidence supporting FDA-approved neuroalgorithms, the subset of machine learning algorithms with applications in the central nervous system (CNS), through a systematic review of the primary literature. Articles covering the 53 FDA-approved algorithms with applications in the CNS published in PubMed, EMBASE, Google Scholar and Scopus between database inception and January 25, 2022 were queried. Initial searches identified 1505 studies, of which 92 articles met the criteria for extraction and inclusion. Studies were identified for 26 of the 53 neuroalgorithms, of which 10 algorithms had only a single peer-reviewed publication. Performance metrics were available for 15 algorithms, external validation studies were available for 24 algorithms, and studies exploring the use of algorithms in clinical practice were available for 7 algorithms. Papers studying the clinical utility of these algorithms focused on three domains: workflow efficiency, cost savings, and clinical outcomes. Our analysis suggests that there is a meaningful gap between the FDA approval of machine learning algorithms and their clinical utilization. There appears to be room for process improvement by implementation of the following recommendations: the provision of compelling evidence that algorithms perform as intended, mandating minimum sample sizes, reporting of a predefined set of performance metrics for all algorithms and clinical application of algorithms prior to widespread use. This work will serve as a baseline for future research into the ideal regulatory framework for AI applications worldwide.

Long-term outcomes and quantitative radiologic analysis of extracranial-intracranial bypass for hemodynamically compromised chronic large artery occlusive disease

This study aimed to demonstrate the effectiveness of nonemergent extracranial-to-intracranial bypass (EIB) in symptomatic chronic large artery atherosclerotic stenosis or occlusive disease (LAA) through quantitative analysis of computed tomography perfusion (CTP) parameters using RAPID software. We retrospectively analyzed 86 patients who underwent nonemergent EIB due to symptomatic chronic LAA. CTP data obtained preoperatively, immediately postoperatively (PostOp0), and 6 months postoperatively (PostOp6M) after EIB were quantitatively analyzed through RAPID software, and their association with intraoperative bypass flow (BF) was assessed. The clinical outcomes, including neurologic state, incidence of recurrent infarction and complications, were also analyzed. The time-to-maximum (Tmax) > 8 s, > 6 s and > 4 s volumes decreased significantly at PostOp0 and up through PostOp6M (preoperative, 5, 51, and 223 ml (median), respectively; PostOp0, 0, 20.25, and 143 ml, respectively; PostOp6M, 0, 7.5, and 148.5 ml, respectively; p < 0.001, p < 0.001, and p < 0.001, respectively). The postoperative improvement in the Tmax > 6 s and > 4 s volumes was significantly correlated with the BF at PostOp0 and PostOp6M (PostOp0, r = 0.367 (p = 0.001) and r = 0.275 (p = 0.015), respectively; PostOp6M r = 0.511 (p < 0.001) and r = 0.391 (p = 0.001), respectively). The incidence of recurrent cerebral infarction was 4.7%, and there were no major complications that produced permanent neurological impairment. Nonemergent EIB under strict operation indications can be a feasible treatment for symptomatic, hemodynamically compromised LAA patients.

Reperfusion injury in acute ischemic stroke: Tackling the irony of revascularization

Reperfusion injury is an unfortunate consequence of restoring blood flow to tissue after a period of ischemia. This phenomenon can occur in any organ, although it has been best studied in cardiac cells. Based on cardiovascular studies, neuroprotective strategies have been developed. The molecular biology of reperfusion injury remains to be fully elucidated involving several mechanisms, however these mechanisms all converge on a similar final common pathway: blood brain barrier disruption. This results in an inflammatory cascade that ultimately leads to a loss of cerebral autoregulation and clinical worsening. In this article, the authors present an overview of these mechanisms and the current strategies being employed to minimize injury after restoration of blood flow to compromised cerebral territories.

Diagnosis and treatment of acute isolated proximal internal carotid artery occlusions: a narrative review

The clinical manifestations of proximal (extracranial) internal carotid artery occlusions (pICAOs) may range from asymptomatic to acute, large, and devastating ischemic strokes. The etiology and pathophysiology of the occlusion, intracranial collateral status and patient's premorbid status are among the factors determining the clinical presentation and outcome of pICAOs. Rapid and accurate diagnosis is crucial and may be assisted by the combination of carotid and transcranial duplex sonography, or a computed tomography/magnetic resonance angiography (CTA/MRA). It should be noted that with either imaging modalities, the discrimination of a pseudo-occlusion of the extracranial internal carotid artery (ICA) from a true pICAO may not be straightforward. In the absence of randomized data, the management of acute, symptomatic pICAOs remains individualized and relies largely on expert opinion. Administration of intravenous thrombolysis is reasonable and probably beneficial in the settings of acute ischemic stroke with early presentation. Unfortunately, rates of recanalization are rather low and acute interventional reperfusion therapies emerge as a potentially powerful therapeutic option for patients with persistent and severe symptoms. However, none of the pivotal clinical trials on mechanical thrombectomy for acute ischemic stroke randomized patients with isolated extracranial large vessel occlusions. On the contrary, several lines of evidence from non-randomized studies have shown that acute carotid endarterectomy, or endovascular thrombectomy/stenting of the ICA are feasible and safe, and pοtentially beneficial. The heterogeneity in the pathophysiology and clinical presentation of acute pICAOs renders patient selection for an acute interventional treatment a complicated decision-making process. The present narrative review will outline the pathophysiology, clinical presentation, diagnostic challenges, and possible treatment options for pICAOs.

Flow augmentation STA-MCA bypass evaluation for patients with acute stroke and unilateral large vessel occlusion: a proposal for an urgent bypass flowchart

OBJECTIVE

Endovascular recanalization trials have shown a positive impact on the preservation of ischemic penumbra in patients with acute large vessel occlusion (LVO). The concept of penumbra salvation can be extended to surgical revascularization with bypass in highly selected patients. For selecting these patients, the authors propose a flowchart based on multimodal MRI.

METHODS

All patients with acute stroke and persisting internal carotid artery (ICA) or M1 occlusion after intravenous lysis or mechanical thrombectomy undergo advanced neuroimaging in a time window of 72 hours after stroke onset including perfusion MRI, blood oxygenation level-dependent functional MRI to evaluate cerebrovascular reactivity (BOLD-CVR), and noninvasive optimal vessel analysis (NOVA) quantitative MRA to assess collateral circulation.

RESULTS

Symptomatic patients exhibiting persistent hemodynamic impairment and insufficient collateral circulation could benefit from bypass surgery. According to the flowchart, a bypass is considered for patients 1) with low or moderate neurological impairment (National Institutes of Health Stroke Scale score 1-15, modified Rankin Scale score ≤ 3), 2) without large or malignant stroke, 3) without intracranial hemorrhage, 4) with MR perfusion/diffusion mismatch > 120%, 5) with paradoxical BOLD-CVR in the occluded vascular territory, and 6) with insufficient collateral circulation.

CONCLUSIONS

The proposed flowchart is based on the patient's clinical condition and multimodal MR neuroimaging and aims to select patients with acute stroke due to LVO and persistent inadequate collateral flow, who could benefit from urgent bypass.

Quantitative radiological analysis and clinical outcomes of urgent EC-IC bypass for hemodynamic compromised patients with acute ischemic stroke

This study aimed to demonstrate the effectiveness of urgent extracranial-to-intracranial bypass (EIB) in acute ischemic stroke (AIS) through quantitative analysis of computed tomography perfusion (CTP) results using RAPID software. We retrospectively analyzed 41 patients who underwent urgent EIB for AIS under strict operation criteria. The quantitative data from CTP images were reconstructed to analyze changes in pre- and postoperative perfusion status in terms of objective numerical values using RAPID software. Short- and long-term clinical outcomes, including complications and neurological status, were also analyzed. Postoperatively, the volume of time-to-max (Tmax) > 6 s decreased significantly; it continued to improve significantly until 6 months postoperatively (preoperative, 78 ml (median); immediate postoperative, 23 ml; postoperative 6 months, 7 ml; p = 0.000). Ischemic core-penumbra mismatch volumes were also significantly improved until 6 months postoperatively (preoperative, 72 ml (median); immediate postoperative, 23 ml; postoperative 6 months, 5 ml; p = 0.000). In addition, the patients' neurological condition improved significantly (p < 0.001). Only one patient (2.3%) showed progression of infarction. Urgent EIB using strict indications can be a feasible treatment for IAT-ineligible patients with AIS due to large vessel occlusion or stenosis.

Trends in Literature on Cerebral Bypass Surgery: A Systematic Review

INTRODUCTION

Ever since the beginning of cerebral bypass surgery, the role of the bypass has been debated and indications have changed over the last 5 decades. This systematic literature research analysed all clinical studies on cerebral bypass that have been published from January 1959 to January 2020 for their year of publication, country of origin, citation index, role of and indication for bypass, bypass technique, revascularized territory, flow capacity, and title (for word cloud analysis per decade).

METHODS

A systematic literature research was conducted using PubMed, Web of Science, EMBASE, and SCOPUS databases. All studies that have been published until January 1, 2020, were included.

RESULTS

Of 6,013 identified studies, 2,585 were included in the analysis. Of these, n = 1,734 (67%) studies addressed flow-augmentation bypass and n = 701 (27%) addressed flow-preservation bypass. The most common indication reported for flow augmentation is moyamoya (n = 877, 51%), followed by atherosclerotic steno-occlusive disease (n = 753, 43%). For flow preservation, the most common indication is studies reporting on cerebral aneurysm surgery (n = 659, 94%). The increasing popularity of reporting on these bypass operations almost came to an end with the FDA approval of flow diverters for aneurysm treatment in 2011. Japan is the country with the most bypass studies (cumulatively published 933 articles), followed by the USA (630 articles) and China (232 articles).

DISCUSSION/CONCLUSION

Clinical studies on cerebral bypass surgery have become increasingly popular in the past decades. Since the introduction of moyamoya as a distinct pathologic entity, Asian countries in particular have a very active community regarding this disease, with an increasing number of articles published every year. Studies on bypass for chronic steno-occlusive disease peaked in the 1980s but have remained the main focus of bypass research, particularly in many European departments. The number of reports published on these bypass operations significantly decreased after the FDA approval of flow diverters for aneurysm treatment in 2011.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

Emergency EC-IC bypass surgery is an effective and safe treatment option for intracranial atherosclerosis-induced acute ischemic stroke for which EVT is inadequate.

Agreement of novel hemodynamic imaging parameters for the acute and chronic stages of ischemic stroke: a matched-pair cohort study

OBJECTIVE

In symptomatic patients with cerebrovascular steno-occlusive disease, impaired blood oxygenation level-dependent cerebrovascular reactivity (BOLD-CVR) and increased flow velocity of the P2 segment of the posterior cerebral artery (PCA-P2) on transcranial Doppler (TCD) ultrasonography have been introduced as emerging clinical imaging parameters to identify patients at high risk for recurrent ischemic events. Since hemodynamic physiology differs between the acute and chronic stages of ischemic stroke, the authors sought to investigate whether those parameters have merit for both the acute and chronic stages of ischemic stroke.

METHODS

From a prospective database, patients who underwent BOLD-CVR and TCD examinations in the acute stroke stage (< 10 days) were matched to patients in the chronic stroke stage (> 3 months). A linear regression analysis for both groups was performed between ipsilateral PCA-P2 systolic flow velocity and BOLD-CVR of the ipsilateral (affected) hemisphere, the ipsilateral middle cerebral artery (MCA) territory, and the ipsilateral steal volume (i.e., paradoxical BOLD-CVR response). The resulting slopes and intercepts were statistically compared to evaluate differences between groups.

RESULTS

Forty matched patient pairs were included. Regression analysis showed no significant difference for either the intercept (p = 0.84) or the slope (p = 0.85) between PCA-P2 flow velocity and BOLD-CVR as measured for the ipsilateral (affected) hemisphere. Similarly, no significant difference was seen between PCA-P2 flow velocity and BOLD-CVR of the ipsilateral MCA territory (intercept, p = 0.72; slope, p = 0.36) or between PCA-P2 flow velocity and steal volume (intercept, p = 0.59; slope, p = 0.34).

CONCLUSIONS

The study results indicated that the relationship between ipsilateral PCA-P2 systolic flow velocity and BOLD-CVR remains the same during the acute and chronic stages of ischemic stroke. This provides further support that these novel hemodynamic imaging parameters may have merit to assess the risk for recurrent ischemic events for a wide ischemic stroke population. PCA-P2 systolic flow velocity, in particular, may be a highly practical screening tool, independent of ischemic stroke stage.

A 1-Donor 2-Recipient Superficial Temporal Artery-Middle Cerebral Artery Bypass for Moyamoya Syndrome: 2-Dimensional Operative Video

We present the case of a 34-yr-old male who suffered repeated ischemic events resulting in right-sided weakness. He was found to have left M1 segment near occlusion on angiography with a large area of uncompensated hypoperfusion. The patient underwent a direct superficial temporal artery-middle cerebral artery (STA-MCA) bypass. Direct bypass in the acute setting of ischemia has been previously described.1-5 Moyamoya ischemic disease can be treated with either direct or indirect surgical revascularization. There have been several techniques developed for direct bypasses in moyamoya ischemic disease. These include the standard 1-donor 1-recipient (1D1R) end-to-side (ES) bypass, the "double-barrel" 2-donor 2-recipient (2D2R) ES bypass, and the more recently developed 1-donor 2-recipient (1D2R)6,7 utilizing both an ES and a side-to-side (SS) bypass with a 1-donor vessel. The case presentation, surgical anatomy, decision-making, operative nuances, and postoperative course and outcome are reviewed. The patient gave verbal consent for participating in the procedure and surgical video.

Efficacy and Safety of Timely Urgent Superficial Temporal Artery-to-Middle Cerebral Artery Bypass Surgery in Patients with Acute Ischemic Stroke: A Single-Institutional Prospective Study and a Pooled Analysis

BACKGROUND

Clinical outcome in patients with acute ischemic stroke (AIS) caused by large vessel occlusion (LVO) is not satisfactory if reperfusion treatment fails or is not tried.

AIMS

We aimed to assess the efficacy and safety of urgent superficial temporal-to-middle cerebral artery (STA-MCA) bypass surgery in selected patients.

METHODS

Patients who were diagnosed with LVO-induced AIS in the anterior circulation but had a failed intra-arterial thrombectomy (IAT) or were not tried due to IAT contraindications were prospectively enrolled. Timely urgent STA-MCA bypass surgery was performed if they showed perfusion-diffusion mismatch or symptom-diffusion mismatch in the acute phase of disease. Clinical and radiological data of these patients were assessed to demonstrate the safety and efficacy of urgent bypass procedures. A pooled analysis of published data on urgent bypass surgery in acute stroke patients was conducted and analyzed.

RESULTS

In 18 patients who underwent timely bypass, the National Institutes of Health Stroke Scale (NIHSS) score improved from 12.11 ± 4.84 to 9.89 ± 6.52, 1 week after surgery. Three-month and long-term (9.72 ± 5.00 months) favorable outcomes (modified Rankin Scale [mRS] scores 0-2) were achieved in 50 and 75% of the patients, respectively. The pooled analysis (117 patients from 10 articles, including ours) identified favorable mRS scores in 71.79% patients at 3 months. A significant NIHSS score improvement from 11.51 ± 4.89 to 7.59 ± 5.50 was observed after surgery with significance. Major complications occurred in 3 patients (2.6%, 3/117) without mortality.

CONCLUSIONS

Urgent STA-MCA bypass surgery can be regarded as a safe optional treatment to prevent cerebral infarct expansion and to improve clinical and radiological outcomes in highly selected patients.

Flow-augmentation bypass in the treatment of acute ischemic stroke

INTRODUCTION

Results of two randomized trials did not show benefit of revascularization with extracranial-intracranial (EC-IC) flow augmentation bypass in patients with symptomatic occlusion of internal carotid artery (ICA). However, patients with acute stroke were not included in these studies. Herein, we systematically analyze and discuss the literature about flow augmentation bypass for treatment of acute ischemic stroke.

EVIDENCE ACQUISITION

This systematic review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. MEDLINE, Web of Science and EMBASE were independently searched by two reviewers for published series to identify literature relating to EC-IC bypass in the surgical management of acute ischemic stroke up to June 2020. Studies were categorized according to their level of evidence.

EVIDENCE SYNTHESIS

Nineteen studies met the inclusion criteria for the systematic literature review, including 16 level IV studies (ten case series and six6 case reports) and three level III studies (retrospective cohort case-control studies). Occurrence of fatal or non-fatal ischemic or hemorrhagic postoperative stroke, as well as clinical functional outcome at follow-up were considered as primary and secondary endpoints, respectively.

CONCLUSIONS

The literature about flow augmentation bypass for treatment of acute ischemic stroke is scarce and heterogenous, with only 19 studies. The results of the present systematic review encourage further study to explore and validate the use of EC-IC bypass in the treatment of anterior circulation acute ischemic stroke in highly selected patients (symptomatic and with persistent penumbra despite best medical/endovascular treatment).

Safety and clinical outcomes of urgent superficial temporal artery-middle cerebral artery bypass-a single-institution retrospective analysis

BACKGROUND

Intravenous recombinant tissue-type plasminogen activator (rt-PA) with/without endovascular treatment is sometimes not ideally effective for the treatment of acute hemodynamic stroke due to atherosclerotic major artery steno-occlusive disease, and some patients show fluctuation in or progression of symptoms despite intensive medical therapy. Urgent superficial temporal artery-middle cerebral artery (STA-MCA) bypass has been reported to be effective in patients with progressing stroke.

OBJECTIVE

To investigate the efficacy of urgent STA-MCA bypass performed at a single institution for progressing stroke due to hemodynamic compromise caused by atherosclerosis.

METHOD

We retrospectively reviewed clinical and operative records. Neurological outcomes were assessed with the modified Rankin Scale (mRS) with consideration of patient age: more than 2 points on the mRS was regarded as a poor outcome in patients under 80 years old, and more than 3 points was considered a poor outcome in those over 80 years old. The risk factors contributing to poor outcomes were evaluated.

RESULTS

From 2008 to 2017, 35 patients underwent urgent STA-MCA bypass for progressing stroke. The average patient age was 70.4 years (range 49-96 years). The mean National Institutes of Health Stroke Scale (NIHSS) score was 5.1 (range 0-24 points) on admission and 7.8 before surgery. After 3 months, 25 patients showed good outcomes. The preoperative NIHSS score contributed to a poor outcome (odds ratio 1.65 (95% confidence interval 1.12-2.90)).

CONCLUSIONS

Urgent STA-MCA bypass is a treatment option for patients with progressing stroke. The operation should be performed while the NIHSS score is low.

When the fat hits the brain-salvage STA-MCA bypass for an intracranial ICA occlusion due to a fat embolus

BACKGROUND

Large fat embolus is a rare but potential reversible cause of ischaemic stroke.

METHODS AND RESULTS

We describe the neurosurgical management of a complete right internal carotid artery occlusion due to a large fat embolus, caused by a mitral valve replacement.

CONCLUSION

Knowledge of acute cerebral ischaemia due to large fat embolism and its hallmark 'hypodense artery' is mandatory. Extracranial to intracranial bypass is a feasible rescue treatment after failure of endovascular embolectomy.

Endovascular stenting for rescue of a failed donor graft during superficial temporal artery to middle cerebral artery bypass surgery: case report

Direct bypass has been used to salvage failed endovascular treatment; however, little is known of the reversed role of endovascular management for failed bypass.The authors report the case of a 7-year-old patient who underwent a superficial temporal artery to middle cerebral artery (STA-MCA) bypass for treatment of a giant MCA aneurysm and describe the role of endovascular rescue in this case. Post-bypass catheter angiogram showed occlusion of the proximal extracranial STA donor with patent anastomosis, possibly due to STA dissection. A self-expanding Neuroform Atlas stent was deployed across the dissection flap, and follow-up images showed revascularization of the STA with good MCA runoff.This case demonstrates that direct extracranial-intracranial bypass failure can infrequently originate from the STA donor vessel and that superselective angiogram can be useful for identification and treatment in such cases. With more advanced endovascular techniques the tide has turned in the treatment of complex cerebrovascular cases, with this case being an early example of successful rescue stenting for endovascular management of a failed donor after STA-MCA bypass.

Endovascular "Boost": External Carotid Angioplasty to Augment Flow Before Superficial Temporal-Middle Cerebral Artery Bypass

BACKGROUND

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass may be used to augment cerebral blood flow in patients with select cerebrovascular pathologies or after failed attempts at revascularization. In this article we describe the use of balloon angioplasty to boost the flow of the external carotid artery (ECA) including the STA to be later used as a donor artery for a STA-MCA bypass procedure.

CASE DESCRIPTION

A 67-year-old male with bilateral carotid artery stenosis presented 2 days after a right middle cerebral artery (MCA) stroke and was admitted for medical management. Over the next 4 days his examination worsened; magnetic resonance imaging and computed tomography perfusion confirmed a right MCA stroke with penumbra and angiography revealed complete occlusion of the right internal carotid artery within a prior carotid stent. There was also a right ECA stenosis at its origin, thus limiting options for traditional extracranial-intracranial bypass. Therefore the patient underwent balloon angioplasty of the right ECA by traversing the carotid stent followed by right STA-MCA bypass, resulting in increased flow, clinical stability, and improved cerebral perfusion.

CONCLUSIONS

This case highlights a unique strategy for the management of internal carotid artery occlusion in combination with an ipsilateral ECA stenosis. We also demonstrate the utility of endovascular adjuncts to open vascular surgery when complex patterns of stenosis or occlusion exist.

Emergent Rescue Extracranial-Intracranial Bypass for Acute Carotid Stent Thrombosis Report

BACKGROUND

Acute stent thrombosis is a rare adverse event following endovascular treatment of carotid artery. Experience on the topic is scarce, making the therapeutic approach a clinical challenge. In cases of intraprocedural acute carotid stent thrombosis, thromboaspiration, thrombectomy, and thrombolysis have been used as successful modalities for achieving recanalization.

CASE DESCRIPTION

We describe a case of carotid artery dissection treated endovascularly and complicated by intraprocedural stent thrombosis, which was ultimately managed by emergent extracranial-intracranial bypass with radial artery graft connecting the external carotid artery to the ipsilateral middle cerebral artery.

CONCLUSIONS

Neurosurgical management may represent a rescue option for otherwise unmanageable acute carotid stent thrombosis.

Local in situ fibrinolysis for recanalization of an occluded extracranial-intracranial bypass: Technical note

Extracranial-intracranial (EC-IC) bypass is a versatile technique to augment or preserve blood flow when treating cerebrovascular pathologies to prevent ischemic complications. Technical success and good patient outcomes rely on the successful establishment and maintenance of a patent bypass graft. Multiple modalities have been developed to confirm intraoperative graft patency. However, techniques and strategies to manage an occluded bypass are sparsely reported. The authors describe a novel technique for the in situ fibrinolysis utilizing recombinant tissue plasminogen activator (r-tPA) to recanalize an occluded EC-IC bypass following thrombus formation. This technique is feasible and effective in restoring long term EC-IC graft patency without requirement of additional vessel harvest or added ischemia time which may be tailored for use with other pharmacologic agents based on the acuity of an in-graft thrombosis.

Clinical importance of the superficial temporal artery in neurovascular diseases: A PRISMA-compliant systematic review

The superficial temporal artery (STA) plays a very important role in neurovascular diseases and procedures. However, until now, no comprehensive review of the role of STA in neurovascular diseases from a neurosurgical perspective has ever been published. To review research on the clinical importance of STA in neurovascular diseases, a literature search was performed using the PubMed database. Articles were screened for suitability and data relevance. This paper was organized following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. According to the literature, STA is one of the terminal branches of the external carotid artery and can give off scalp, muscle, and transosseous branches. STA-middle cerebral artery (MCA) bypass is very useful for intracranial ischemic diseases, including moyamoya disease, chronic ICA and MCA insufficiency, and even acute ischemic stroke. For intracranial complex aneurysms, STA bypass remains a major option that can serve as flow replacement bypass during aneurysmal trapping or insurance bypass during temporary parent artery occlusion. Occasionally, the STA can also be involved in dural AVFs (DAVFs) via to its transosseous branches. In addition, the STA can be used as an intraoperative angiography path and the path to provide endovascular treatments. Therefore, STA is a very important artery in neurovascular diseases.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Usefulness of intraoperative Indocyanine green video angiography to select the recipient artery for bypass surgery in arteriosclerotic occlusion of the middle cerebral artery: a technical case report

BACKGROUND

In superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass surgery, indocyanine green video angiography (ICG-VA) is usually used to verify bypass patency. Less-commonly reported is the ability to use this technique to evaluate candidate recipient vessels based on either collateral flow or identification of the distal branch of interest.

CASE PRESENTATION

An 82-year-old man presented with progressive cerebral infarction due to infarction of the M2 inferior trunk of the right middle cerebral artery. He underwent superficial temporal artery-middle cerebral artery bypass to prevent further ischemia 1 week after the initial stroke. In the surgery, M4 cortical arteries fed by the inferior trunk could not be identified as recipient arteries. Intraoperative ICG-VA showed delayed luminescence of some M4 arteries. Because the M4 arteries fed by the inferior trunk showed delayed retrograde flows from the anterior cerebral artery on preoperative digital subtraction angiography, the M4 arteries with delayed luminescence on ICG-VA were considered to be M4 arteries fed by the inferior trunk and selected as the recipient arteries.

CONCLUSIONS

ICG-VA shows differences in flow speed as delayed luminescence. This finding may be useful for detecting target vessels.

Microvascular anastomosis under 3D exoscope or endoscope magnification: A proof-of-concept study

Background:

Extracranial–intracranial bypass is a challenging procedure that requires special microsurgical skills and an operative microscope. The exoscope is a tool for neurosurgical visualization that provides view on a heads-up display similar to an endoscope, but positioned external to the operating field, like a microscope. The authors carried out a proof-of-concept study evaluating the feasibility and effectiveness of performing microvascular bypass using various new exoscopic tools.

Methods:

We evaluated microsurgical procedures using a three-dimensional (3D) endoscope, hands-free robotic automated positioning two-dimensional (2D) exoscope, and an ocular-free 3D exoscope, including surgical gauze knot tying, surgical glove cutting, placental vessel anastomoses, and rat vessel anastomoses. Image quality, effectiveness, and feasibility of each technique were compared among different visualization tools and to a standard operative microscope.

Results:

3D endoscopy produced relatively unsatisfactory resolution imaging. It was shown to be sufficient for knot tying and anastomosis of a placental artery, but was not suitable for anastomosis in rats. The 2D exoscope provided higher resolution imaging, but was not adequate for all maneuvers because of lack of depth perception. The 3D exoscope was shown to be functional to complete all maneuvers because of its depth perception and higher resolution.

Conclusion:

Depth perception and high resolution at highest magnification are required for microvascular bypass procedures. Execution of standard microanastomosis techniques was unsuccessful using 2D imaging modalities because of depth-perception-related constraints. Microvascular anastomosis is feasible under 3D exoscopic visualization; however, at highest magnification, the depth perception is inferior to that provided by a standard operative microscope, which impedes the procedure.