Cerebral revascularization after the Carotid Occlusion Surgery Study: what candidates remain, and can we do better?

Individualised evaluation based on pathophysiology for moyamoya vasculopathy: application in surgical revascularisation

BACKGROUND

Although bypass surgery is an effective treatment for moyamoya vasculopathy (MMV), the incidence of postoperative complications is still high. This study aims to introduce a novel evaluating system based on individualised pathophysiology of MMV, and to assess its clinical significance.

METHODS

This multicentre, prospective study enrolled adult patients with MMV from Huashan Hospital, Fudan University and National Center for Neurological Disorders, China between March 2021 and February 2022. Multimodal neuroimages containing structural and functional information were used to evaluate personalised disease severity and fused to localise the surgical field, avoid invalid regions and propose alternative recipient arteries. The recipient artery was further selected intraoperatively by assessing regional haemodynamic and electrophysiological information. The preanastomosis and postanastomosis data were compared with assist with the postoperative management. Patients who received such tailored revascularisations were included in the novel group and the others were included in the traditional group. The 30-day surgical outcomes and intermediate long-term follow-up were compared.

RESULTS

Totally 375 patients (145 patients in the novel group and 230 patients in the traditional group) were included. The overall complication rate was significantly lower in the novel group (p˂0.001). In detail, both the rates of postoperative infarction (p=0.009) and hyperperfusion syndrome (p=0.010) were significantly lower. The functional outcomes trended to be more favourable in the novel group, though not significantly (p=0.260). Notably, the proportion of good functional status was higher in the novel group (p=0.009). Interestingly, the preoperative statuses of perfusion and metabolism around the bypass area were significantly correlated with the occurrence of postoperative complications (P˂0.0001).

CONCLUSIONS

This novel evaluating system helps to identify appropriate surgical field and recipient arteries during bypass surgery for MMV to achieve better haemodynamic remodelling and pathophysiological improvement, which results in more favourable clinical outcomes.

Comparison of IMD and ICG videoangiography in combined bypass surgery: a single-center study

BACKGROUND

Superficial temporal artery-middle cerebral artery (STA-MCA) bypass combined with an encephaloduromyosynangiosis (EDMS) had gained significant role in treating chronic cerebral ischemia. Invasiveness and costs of intraoperative digital subtraction angiography (DSA) limited its application in operations.

OBJECTIVE

To find the reliable parameters for determining bypass patency with intraoperative micro-Doppler (IMD) sonography and compare the diagnostic accuracy of indocyanine green (ICG) videoangiography with IMD in combined bypass.

METHOD

One hundred fifty bypass procedures were included and divided into patent and non-patent groups according to postoperative computed tomography angiography (CTA) within 72 h. The surgical process was divided into four phases in the following order: preparation phase (phase 1), anastomosis phase (phase 2), the temporalis muscle closure phase (phase 3), and the bone flap closure phase (phase 4). The IMD parameters were compared between patent and non-patent groups, and then compared with the patency on CTA by statistical analyses. IMD with CTA, ICG videoangiography with CTA, IMD with ICG videoangiography were performed to assess bypass patency. The agreement between methods was evaluated using kappa statistics.

RESULTS

No significant differences of baseline characteristics were found between patent and non-patent group. Parameters in the STA were different between patent and non-patent groups in phases 2, 3, and 4. In patent group, Vm was apparently higher and PI was lower in phases 2, 3, and 4 compared with phase 1 (P < .001). In non-patent group, no differences of Vm and PI were found within inter-group. The best cutoff value of IMD in the STA to distinguish patent from non-patent bypasses was Vm in phase 4 > 17.5 cm/s (sensitivity 94.2%, specificity 100%). In addition, the agreement for accessing bypass patency was moderate between ICG videoangiography and CTA (kappa = 0.67), IMD and ICG videoangiography (kappa = 0.73), and good between IMD and CTA (kappa = 0.86).

CONCLUSION

ICG videoangiography could directly display morphology changes of bypass. IMD could be used for providing half-quantitative parameters to assess bypass patency. Vm in phase 4 > 17.5 cm/s suggesting the patency of bypass on CTA would be good. Also, compared with ICG videoangiography, IMD had more accuracy.

Hyperperfusion syndrome after superficial temporal artery-middle cerebral artery bypass for non-moyamoya steno-occlusive disease

BACKGROUND AND OBJECTIVES

Stroke is a major cause of morbidity and mortality worldwide, and intracranial stenoses increase the risk for stroke. Superficial temporal artery to middle cerebral artery bypass can be beneficial in selected patients with non-moyamoya steno-occlusive disease, however data is limited regarding the postoperative occurrence of hyperperfusion syndrome in this population. This case series describes the outcomes and complications, including hyperperfusion, in these patients who underwent bypass.

METHODS

This is a retrospective review of bypass procedures done for medically refractory intracranial stenosis at a single institution by a single surgeon between 2014 and 2021.

RESULTS

30 patients underwent 33 bypass procedures for unequivocal non-moyamoya steno-occlusive disease. All patients had immediate bypass patency on post-operative day one. Major perioperative complications (9%) included one stroke and two cases of hyperperfusion syndrome. Minor perioperative complications (12%) included two seizures, one superficial wound infection and one deep vein thrombosis. Modified Rankin Score improved in 20 patients (74%), worsened in one patient (4%), and remained stable in seven patients (22%) at the last follow up. Twenty-three patients (85%) had scores ≤ 2. The recurrent stroke rate was 3% at 30 days and 7% at two years. The bypass patency rate at one year was 87.5%.

CONCLUSION

In this series, bypass for patients with medically refractory non-moyamoya steno-occlusive disease was well tolerated and effective, with overall favorable outcomes. The occurrence of hyperperfusion syndrome is rare but significant and should be considered in post-operative management of this population.

Influence of Patient and Technical Variables on Combined Direct and Indirect Cerebral Revascularization: Case Series

BACKGROUND

Cerebral bypass for flow augmentation is an important technique for selected neurosurgical patients, with multiple techniques used (direct, indirect, or combined).

OBJECTIVE

To assess the impact of patient and technical variables on direct and indirect bypass flow after combined revascularization.

METHODS

This was a retrospective, single-institution review of patients undergoing direct superficial temporal artery-to-middle cerebral artery bypass with indirect encephaloduro-myosynangiosis for moyamoya disease and steno-occlusive cerebrovascular disease over a 2-year period. We evaluated the effect of baseline patient characteristics, preoperative imaging characteristics, and operative variables on direct and indirect patency grades.

RESULTS

Twenty-six hemispheres (8 moyamoya disease and 18 steno-occlusive cerebrovascular disease) in 23 patients were treated with combined revascularization. The mean patient age was 53.4 ± 19.1 years. Direct bypass patency was 96%. Over a mean follow-up of 8.3 ± 5.4 months, there were 3 strokes in the treated hemispheres (11.5%). The mean modified Rankin Scale score improved from 1.3 ± 1.1 preoperatively to 0.7 ± 0.8 postoperatively. Preservation of the nondonor superficial temporal artery branch was associated with a lower direct bypass grade ( P < .01), whereas greater mean time to maximum perfusion (Tmax)> 4 and >6 seconds and mismatch volumes were associated with higher direct bypass grades ( P < .05). Tmax >4-second volume inversely predicted indirect bypass patency.

CONCLUSION

Patient and technical variables may influence the relative contributions of the direct and indirect components of combined revascularizations.

Extracranial-Intracranial Cerebral Revascularization for Atherosclerotic Vessel Occlusion: An Updated Systematic Review of the Literature

BACKGROUND

Atherosclerotic steno-occlusive cerebrovascular disease includes extracranial carotid occlusive and intracranial atherosclerotic disease. Despite the negative findings in Carotid Occlusion Surgery Study (COSS), many large centers continue to report favorable results for revascularization surgery in select groups of patients. The aim of our study was to perform an updated systematic review to investigate the role of revascularization surgery for atherosclerotic steno-occlusive patients in the modern era.

METHODS

Five independent reviewers performed Preferred Reporting Items for Systematic Reviews and Meta-Analyses-guided literature searches in October 2022 to identify articles reporting clinical outcomes in adult patients undergoing bypass for atherosclerotic steno-occlusive disease. Primary endpoints used were perioperative and long-term ischemic strokes, intracerebral hemorrhage, bypass patency, and favorable clinical outcomes. Study quality was evaluated with Newcastle-Ottawa, JADAD, and the Oxford Center for Evidence-Based Medicine scales.

RESULTS

A total of 6709 articles were identified in the initial search. Of these articles, 50 met the inclusion criteria and were included in the systematic review. A notable increase in the proportion of articles published over the past 10 years was observed. There were 6046 total patients with 4447 bypasses performed over the period from 1978 to 2022. The average length of follow-up was 2.75 ± 2.71 years. The average Newcastle-Ottawa was 6.23 out of 9 stars. There was a significant difference in perioperative stroke (odds ratio [OR], 0.65 [0.48-0.87]; P = 0.004), long-term ischemia (OR, 0.32 [0.23-0.44]; P < 0.0001), overall ischemia (OR, 0.36 [0.28-0.44]; P < 0.0001), and favorable outcomes (OR, 3.63 [2.84-4.64]; P < 0.0001) when comparing pre-COSS to post-COSS time frames in favor of post-COSS.

CONCLUSIONS

Based on a systematic review of 50 articles, the existing literature indicates that long-term stroke rates and favorable outcomes for surgical revascularization for steno-occlusive disease have improved over time and are lower than previously reported. Improved patient selection, perioperative care, and surgical techniques may contribute to improved outcomes.

Revisiting flow augmentation bypass for cerebrovascular atherosclerotic vaso-occlusive disease: Single-surgeon series and review of the literature

OBJECTIVE

Despite advances in the nonsurgical management of cerebrovascular atherosclerotic steno-occlusive disease, approximately 15-20% of patients remain at high risk for recurrent ischemia. The benefit of revascularization with flow augmentation bypass has been demonstrated in studies of Moyamoya vasculopathy. Unfortunately, there are mixed results for the use of flow augmentation in atherosclerotic cerebrovascular disease. We conducted a study to examine the efficacy and long term outcomes of superficial temporal artery to middle cerebral artery (STA-MCA) bypass in patients with recurrent ischemia despite optimal medical management.

METHODS

A single-institution retrospective review of patients receiving flow augmentation bypass from 2013-2021 was conducted. Patients with non-Moyamoya vaso-occlusive disease (VOD) who had continued ischemic symptoms or strokes despite best medical management were included. The primary outcome was time to post-operative stroke. Time from cerebrovascular accident to surgery, complications, imaging results, and modified Rankin Scale (mRS) scores were aggregated.

RESULTS

Twenty patients met inclusion criteria. The median time from cerebrovascular accident to surgery was 87 (28-105.0) days. Only one patient (5%) had a stroke at 66 days post-op. One (5%) patient had a post-operative scalp infection, while 3 (15%) developed post-operative seizures. All 20 (100%) bypasses remained patent at follow-up. The median mRS score at follow up was significantly improved from presentation from 2.5 (1-3) to 1 (0-2), P = .013.

CONCLUSIONS

For patients with high-risk non-Moyamoya VOD who have failed optimal medical therapy, contemporary approaches to flow augmentation with STA-MCA bypass may prevent future ischemic events with a low complication rate.

Double-Barrel (2-Donor-2-Recipient) Bypass as Rescue Treatment for Patient with Occluded Middle Cerebral Artery Intracranial Stent and Recurrent Ischemia

Stent occlusion is a challenging complication following endovascular interventions that require intracranial stenting.1-4 Although there are small series describing revascularization for stenoocclusive disease failing best medical management,5-14 there are few reports in the literature regarding surgical bypass as a treatment for stent occlusion.5 We present the case of a 37-year-old man who presented with right-sided weakness, numbness, and difficulty with speech and ambulation. His history is notable for a left M1 (segment of middle cerebral artery) occlusion 6 months prior that was treated with mechanical thrombectomy requiring repeat thrombectomy and rescue acute middle cerebral artery (MCA) stent placement given vessel reocclusion. Diagnostic cerebral angiography demonstrated stent occlusion. Given his continued ischemic symptoms despite best medical management, the patient underwent a double-barrel superficial temporal artery-MCA direct bypass to revascularize the MCA territory. To our knowledge, there is no literature to date describing a 2-donor-2-recipient direct bypass for the rescue treatment of symptomatic intracranial stent occlusion with recurrent ischemia. We review the case presentation, angiographic findings, surgical nuances, and postoperative course with imaging. The patient provided informed consent for the procedure and verbal support for publishing his image and inclusion in this submission.

Controversies and Advances in Adult Intracranial Bypass Surgery in 2020

Cerebral revascularization utilizing a variety of bypass techniques can provide either flow augmentation or flow replacement in the treatment of a range of intracranial pathologies, including moyamoya disease, intracranial atherosclerotic disease, and complex aneurysms that are not amenable to endovascular or simple surgical techniques. Though once routine, the publication of high-quality prospective evidence, along with the development of flow-diverting stents, has limited the indications for extracranial-to-intracranial (EC-IC) bypass. Nevertheless, advances in imaging, assessment of cerebral hemodynamics, and surgical technique have changed the risk-benefit calculus for EC-IC bypass. New variations of revascularization surgery involving multiple anastomoses, flow preserving solutions, IC-IC constructs, and posterior circulation bypasses have been pioneered for otherwise difficult to treat pathology including giant aneurysms, dolichoectasia, and medically refractory intracranial atherosclerosis. This review provides a practical update on recent advances in adult intracranial bypass surgery.

Superficial Temporal Artery to Middle Cerebral Artery Cranial Bypass for Nonmoyamoya Steno-Occlusive Disease in Patients Who Failed Optimal Medical Treatment: A Case Series

BACKGROUND

In the post-Carotid Occlusion Surgery Study (COSS) era, multiple reviews suggested subset groups of patients as potential candidates for superficial temporal artery to middle cerebral artery (STA-MCA) bypass. Among them are patients with recurrent strokes despite optimal medical therapy. There is a paucity of data on the outcome of bypass in these specific patients.

OBJECTIVE

To examine the safety and efficacy of direct STA-MCA bypass in patients with nonmoyamoya, symptomatic steno-occlusive disease with impaired distal perfusion, who failed optimal medical management or endovascular treatment.

METHODS

A retrospective review was performed to identify patients with cerebrovascular steno-occlusive disease who underwent bypass after symptomatic recurrent or rapidly progressive strokes, despite optimal conservative or endovascular treatment.

RESULTS

A total of 8 patients (mean age 60 ± 6 yr) underwent direct or combined direct/indirect STA-MCA bypass between 2016 and 2019. All anastomoses were patent. One bypass carried slow flow. There were no procedure-related permanent deficits. One patient developed seizures which were controlled by medications. A total of 7 out of 8 patients were stable or improved clinically at last follow-up (mean 27.3 ± 13.8 mo) without recurrent strokes. One patient did not recover from their presenting stroke, experienced severe bilateral strokes 4 mo postoperatively, and subsequently expired. Modified Rankin Scale (mRS) improved in 6 patients (75%), remained stable in 1 patient (12.5%), and deteriorated in 1 (12.5%). Good long-term functional outcome was achieved in 5 patients (63%, mRS ≤ 2).

CONCLUSION

Patients with symptomatic, hypoperfused steno-occlusive disease who fail optimal medical or endovascular treatment may benefit from cerebral revascularization. Direct or combined STA-MCA bypass was safe and provided favorable outcomes in this small series.

The cut flow index revisited: utility of intraoperative blood flow measurements in extracranial-intracranial bypass surgery for ischemic cerebrovascular disease

OBJECTIVE

In extracranial-intracranial (EC-IC) bypass surgery, the cut flow index (CFI) is the ratio of bypass flow (ml/min) to donor vessel cut flow (ml/min), and a CFI ≥ 0.5 has been shown to correlate with bypass patency. The authors sought to validate this observation in a large cohort of EC-IC bypasses for ischemic cerebrovascular disease with long-term angiographic follow-up.

METHODS

All intracranial bypass procedures performed at a single institution between 2003 and 2018 were reviewed. Demographic, clinical, angiographic, and operative data were recorded and analyzed according to bypass patency with univariate and multivariate statistical analyses.

RESULTS

A total of 278 consecutive intracranial bypasses were performed during the study period, of which 157 (56.5%) were EC-IC bypasses for ischemic cerebrovascular disease. Intraoperative blood flow measurements were available in 146 patients, and angiographic follow-up was available at a mean of 2.1 ± 2.6 years after bypass. The mean CFI was significantly higher in patients with patent bypasses (0.92 vs 0.64, p = 0.003). The bypass patency rate was 83.1% in cases with a CFI ≥ 0.5 compared with 46.4% in cases with a CFI < 0.5 (p < 0.0001). Adjusting for age, sex, diagnosis, and single versus double anastomosis, the CFI remained a significant predictor of bypass patency (p = 0.001; OR 5.8, 95% CI 2.0-19.0). A low CFI was also associated with early versus late bypass nonpatency (p = 0.008).

CONCLUSIONS

A favorable CFI portends long-term EC-IC bypass patency, while a poor CFI predicts eventual bypass nonpatency and can alert surgeons to potential problems with the donor vessel, anastomosis, or recipient bed during surgery.

Basal and Acetazolamide Brain Perfusion SPECT in Internal Carotid Artery Stenosis

Internal carotid artery (ICA) stenosis including Moyamoya disease needs revascularization when hemodynamic insufficiency is validated. Vascular reserve impairment was the key to find the indication for endarterectomy/bypass surgery in the atherosclerotic ICA stenosis and to determine the indication, treatment effect, and prognosis in Moyamoya diseases. Vascular reserve was quantitatively assessed by 1-day split-dose I-123 IMP basal/acetazolamide SPECT in Japan or by Tc-99m HMPAO SPECT in other countries using qualitative or semi-quantitative method. We summarized the development of 1-day basal/ acetazolamide brain perfusion SPECT for ICA stenosis, both quantitative and qualitative methods, and their methodological issues regarding (1) acquisition protocol; (2) qualitative assessment, either visual or deep learning-based; (3) clinical use for atherosclerotic ICA steno-occlusive diseases and mostly Moyamoya diseases; and (4) their impact on the choice of treatment options. Trials to use CT perfusion or perfusion MRI using contrast materials or arterial spin labeling were briefly discussed in their endeavor to use basal studies alone to replace acetazolamide-challenge SPECT. Theoretical and practical issues imply that basal perfusion evaluation, no matter how much sophisticated, will not disclose vascular reserve. Acetazolamide rarely causes serious adverse reactions but included fatality, and now, we need to monitor patients closely in acetazolamide-challenge studies.

Deep learning-based interpretation of basal/acetazolamide brain perfusion SPECT leveraging unstructured reading reports

PURPOSE

Basal/acetazolamide brain perfusion single-photon emission computed tomography (SPECT) has been used to evaluate functional hemodynamics in patients with carotid artery stenosis. We aimed to develop a deep learning model as a support system for interpreting brain perfusion SPECT leveraging unstructured text reports.

METHODS

In total, 7345 basal/acetazolamide brain perfusion SPECT images and their text reports were retrospectively collected. A long short-term memory (LSTM) network was trained using 500 randomly selected text reports to predict manually labeled structured information, including abnormalities of basal perfusion and vascular reserve for each vascular territory. Using this trained LSTM model, we extracted structured information from the remaining 6845 text reports to develop a deep learning model for interpreting SPECT images. The model was based on a 3D convolutional neural network (CNN), and the performance was tested on the other 500 cases by measuring the area under the receiver-operating characteristic curve (AUC). We then applied the model to patients who underwent revascularization (n = 33) to compare the estimated output of the CNN model for pre- and post-revascularization SPECT and clinical outcomes.

RESULTS

The AUC of the LSTM model for extracting structured labels was 1.00 for basal perfusion and 0.99 for vascular reserve for all 9 brain regions. The AUC of the CNN model designed to identify abnormal perfusion was 0.83 for basal perfusion and 0.89 for vascular reserve. The output of the CNN model was significantly improved according to the revascularization in the target vascular territory, and its changes in brain territories were concordant with clinical outcomes.

CONCLUSION

We developed a deep learning model to support the interpretation of brain perfusion SPECT by converting unstructured text reports into structured labels. This model can be used as a support system not only to identify perfusion abnormalities but also to provide quantitative scores of abnormalities, particularly for patients who require revascularization.

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.