Indocyanine green videoangiography for assessment of postoperative hyperperfusion in moyamoya disease

Advances in moyamoya disease: pathogenesis, diagnosis, and therapeutic interventions

Moyamoya disease (MMD) is a type of cerebrovascular disease characterized by occlusion of the distal end of the internal carotid artery and the formation of collateral blood vessels. Over the past 20 years, the landscape of research on MMD has significantly transformed. In this review, we provide insights into the pathogenesis, diagnosis, and therapeutic interventions in MMD. The development of high-throughput sequencing technology has expanded our understanding of genetic susceptibility, identifying MMD-related genes beyond RNF213, such as ACTA2, DIAPH1, HLA, and others. The genetic susceptibility of MMD to its pathological mechanism was summarized and discussed. Based on the second-hit theory, the influences of inflammation, immunity, and environmental factors on MMD were also appropriately summarized. Despite these advancements, revascularization surgery remains the primary treatment for MMD largely because of the lack of effective in vivo and in vitro models. In this study, 16 imaging diagnostic methods for MMD were summarized. Regarding therapeutic intervention, the influences of drugs, endovascular procedures, and revascularization surgeries on patients with MMD were discussed. Future research on the central MMD vascular abnormalities and peripheral circulating factors will provide a more comprehensive understanding of the pathogenic mechanisms of MMD.

Clinical Consensus Statement on the Use of Indocyanine Green Fluorescence-guided Surgery in Pediatric Patients

BACKGROUND AND AIMS

Indocyanine Green Fluorescence (ICG-F)- guided surgery is becoming an increasingly helpful tool in pediatric surgical care. This consensus statement investigates the utility of ICG-F in various pediatric surgical applications, primarily focusing on its evidence base, safety, indications, use across different surgical specialties and dosing strategies. The aim is to establish an international consensus for ICG-F use in pediatric surgery.

METHODS

An international panel of 15 pediatric surgeons from 9 countries was assembled. The structured process consisted of a rapid scoping review, iterative discussion sessions, mixed-methods studies with key stakeholders, and voting rounds on individual statements to create draft consensus statements.

RESULTS

100 articles were identified during the review and summarized by application. Based on this condensed evidence, consensus statements were generated after 3 iterative rounds of anonymous voting. Key areas of agreement were quality of evidence, the safety of ICG, pediatric surgical indications, utilization per surgical specialty, and dosing of ICG.

CONCLUSION

This consensus statement aims to guide healthcare professionals in managing ICG-F use in pediatric surgical cases based on the best available evidence, key stakeholder consultation, and expert opinions. Despite ICG-F's promising potential, the need for higher-quality evidence, prospective trials, and safety studies is underscored. The consensus also provides a framework for pediatric surgeons to utilize ICG-F effectively.

LEVEL OF EVIDENCE

III.

The value of indocyanine green-FLOW800 in microvasculature for predicting cerebral hyperperfusion syndrome in moyamoya disease patients

Among the notable complications of direct hemodynamic reconstruction for moyamoya disease (MMD) is cerebral hyperperfusion syndrome (CHS). In this study, we evaluated hemodynamic changes in small regional microvasculature (SRMV) around the anastomosis site by using indocyanine green (ICG)-FLOW800 video angiography and verified that it better predicted the onset of CHS. Intraoperative ICG-FLOW800 analysis was performed on 31 patients (36 cerebral hemispheres) with MMD who underwent superficial temporal artery-middle cerebral artery (MCA) bypass grafting at our institution. The regions of interest were established in the SRMV and thicker MCA around the anastomosis. Calculations were made for half-peak to time (TTP1/2), cerebral blood volume (CBV), and cerebral blood flow (CBF). According to the presence or absence of CHS after surgery, CHS and non-CHS groups of patients were separated. The results showed that ΔCBV and ΔCBF were substantially greater in SRMV than in MCA (p < 0.001). Compared with the non-CHS group, ΔCBF and ΔCBV of SRMV and MCA were considerably greater in the CHS group (p < 0.001). ΔCBF and ΔCBV on the ROC curve for both SRMV and MCA had high sensitivity and specificity (SRMV: ΔCBF, AUC = 0.8586; ΔCBV, AUC = 0.8158. MCA: ΔCBF, AUC = 0.7993; ΔCBV, AUC = 0.8684). ICG-FLOW800 video angiography verified the differential hemodynamic changes in the peri-anastomotic MCA and SRMV before and after bypass surgery in patients with MMD.

Fluorescence-guided surgery: National trends in adoption and application in pediatric surgery

BACKGROUND

Fluorescence-guided surgery (FGS) with indocyanine green (ICG) is a rapidly diffusing surgical innovation, but its utilization in pediatrics remains unknown. We present a cross-sectional descriptive analysis of trends from a national database.

METHODS

The Pediatric Health Information System (PHIS) database was queried for patient encounters between January 2016 and July 2021 with an associated ICG administration within 3 days prior to surgery. All procedure codes from each encounter were reviewed by two surgeons to determine the most likely associated FGS procedure and assign an operative category.

RESULTS

1270 encounters were identified from 38 participating hospitals. The mean patient age (SD) was 8.3 (6.4) years, 54.5% were male, 63.8% were white, and 30.1% were Hispanic. The most common categories for ICG use were neurosurgery (21.3%), biliary (18.3%), perfusion (14.8%), urology (12.5%), gastrointestinal (10.8%), ophthalmology (8.8%), and thoracic (5.6%). Utilization over time increased for some categories (thoracic, visceral perfusion, and neurological procedures) or remained stable for other categories. Overall ICG utilization has increased in 2020 (n = 314) compared to 2016 (N = 83). The number of centers utilizing ICG has also increased from 14 hospitals in 2016 to 29 hospitals in 2020 though adoption remains unevenly distributed, with 5 high-utilization hospitals accounting for 56.8% of all ICG FGS cases.

CONCLUSION

ICG is being used across a wide variety of pediatric surgical disciplines. Trends over time show increasingly frequent adoption across the country, with a few high-volume centers driving the innovation. Fluorescence-guided surgery is commercially available and is becoming more commonplace for pediatric surgeons. Dedicated efforts will now be needed to assess outcomes using this promising technology.

LEVEL OF EVIDENCE

Level IV.

STUDY TYPE

Retrospective study.

Effectiveness of pharmacologic interventions for prevention of cerebral hyperperfusion syndrome following bypass surgery

BACKGROUND

Cerebral hyperperfusion syndrome (CHS) following bypass surgery is a major cause of neurological morbidity and mortality. However, data regarding its prevention have not been assorted until date.

OBJECTIVE

The objective of this study was to review the literature and evaluate whether any conclusion can be drawn regarding the effectiveness of any measure on preventing bypass-related CHS.

METHODS

We systematically reviewed PubMed and Cochrane Library from September 2008 to September 2018 to collect data regarding the effectiveness of pharmacologic interventions on the refers to pretreatment (PRE) of bypass-related CHS. We categorized interventions regarding their class of drugs and their combinations and calculated overall pooled estimates of proportions of CHS development through random-effects meta-analysis of proportions.

RESULTS

Our search yielded 649 studies, of which 23 fulfilled inclusion criteria. Meta-analysis included 23 studies/2,041 cases. In Group A (blood pressure [BP] control), 202 out of 1,174 pretreated cases developed CHS (23.3% pooled estimate; 95% confidence interval [CI]: 9.9-39.4), Group B (BP control + free radical scavenger [FRS]) 10/263 (0.3%; 95% CI: 0.0-14.1), Group C (BP control + antiplatelet) 22/204 (10.3%; 95% CI: 5.1-16.7), and Group D (BP control + postoperative sedation) 29/400 (6.8%; 95% CI: 4.4-9.6)].

CONCLUSIONS

BP control alone has not been proven effective in preventing CHS. However, BP control along with either a FRS or an antiplatelet agent or postoperative sedation seems to reduce the incidence of CHS.

Complementary Tools in Cerebral Bypass Surgery

Cerebral revascularization surgery has been advanced by the refinement of several adjunctive tools. These tools include perioperative blood thinners, intraoperative spasmolytic agents, electrophysiological monitoring, and methods for assessing bypass patency or marking arteriotomies. Despite the array of options, the proper usage and comparative advantages of different complements in cerebral bypass have not been well-cataloged elsewhere. In this literature review, we describe the appropriate usage, benefits, and limitations of various bypass adjuncts. Understanding these adjuncts can help surgeons ensure that they receive reliable intraoperative information about bypass function and minimize the risk of serious complications. Overall, this review provides a succinct reference for neurosurgeons on various cerebrovascular bypass adjuncts.

Pseudo-residual nidus after arteriovenous malformation surgery: illustrative case

BACKGROUND

Intraoperative indocyanine green video angiography (ICG-VA) is useful for determining the extent of lesion removal during cerebral arteriovenous malformation (AVM) surgery. The authors described a case of surgical removal of an AVM presenting with early venous filling mimicking a residual nidus on intraoperative ICG-VA.

OBSERVATIONS

A 7-year-old girl experienced a sudden disturbance of consciousness. Computed tomography revealed right frontal intracerebral hemorrhage. Digital subtraction angiography showed a Spetzler-Martin grade 1 AVM in the right frontal lobe. The patient received surgical removal of the AVM after endovascular embolization. After removal of the nidus, the first intraoperative ICG-VA revealed early venous filling of the cortex around the excision cavity. Additional resection of the cortex around this area was performed. Histopathological examination of the lesion revealed a dilated normal vascular structure without an AVM.

LESSONS

Early venous filling in the surrounding brain tissue after AVM removal does not necessarily indicate a residual nidus. The need for additional resection of the lesion depends on the eloquence of the area.

Moyamoya Disease-Standards and Advances in Revascularization Procedure and Peri-operative Management

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with unknown etiology characterized by progressive stenosis at the terminal portion of the internal carotid artery and the abnormal vascular network formation at the base of the brain. Superficial temporal artery-middle cerebral artery (STA-MCA) bypass is a preferred surgical procedure for ischemic-onset MMD patients by improving cerebral blood flow. Recent evidence further indicates that flow-augmentation bypass has a potential role for preventing re-bleeding in hemorrhagic-onset MMD patients. Based on such cumulative evidence, there is a worldwide increase in the number of MMD patients undergoing bypass surgery, thus thorough understanding of the basic pathology of MMD including peri-operative hemodynamics is critical for avoiding surgical complications. The author sought to demonstrate the standard surgical procedure of STA-MCA bypass with indirect pial synangiosis for adult MMD patients and its pitfall in the early postoperative period, introducing the characteristic peri-operative hemodynamic condition of adult MMD after surgery, such as local cerebral hyperperfusion and intrinsic hemodynamic ischemia caused by watershed shift phenomenon.

Intraoperative cerebral blood flow monitoring in neurosurgery: A review of contemporary technologies and emerging perspectives

Intraoperative monitoring of cerebral blood flow (CBF) has become an invaluable adjunct to vascular and oncological neurosurgery, reducing the risk of postoperative morbidity and mortality. Several technologies have been developed during the last two decades, including laser-based techniques, videomicroscopy, intraoperative MRI, indocyanine green angiography, and thermography. Although these technologies have been thoroughly studied and clinically applied outside the operative room, current practice lacks an optimal technology that perfectly fits the workflow within the neurosurgical operative room. The different available technologies have specific strengths but suffer several drawbacks, mainly including limited spatial and/or temporal resolution. An optimal CBF monitoring technology should meet particular criteria for intraoperative use: excellent spatial and temporal resolution, integration in the operative workflow, real-time quantitative monitoring, ease of use, and non-contact technique. We here review the main contemporary technologies for intraoperative CBF monitoring and their current and potential future applications in neurosurgery.

Imaging methods for surgical revascularization in patients with moyamoya disease: an updated review

Neuroimaging is crucial in moyamoya disease (MMD) for neurosurgeons, during pre-surgical planning and intraoperative navigation not only to maximize the success rate of surgery, but also to minimize postsurgical neurological deficits in patients. This is a review of recent literatures which updates the clinical use of imaging methods in the morphological and hemodynamic assessment of surgical revascularization in patients with MMD. We aimed to assist surgeons in assessing the status of moyamoya vessels, selecting bypass arteries, and monitoring postoperative cerebral perfusion through the latest imaging technology.

Focused Ultrasound-Augmented Cancer Phototheranostics Using Albumin-Indocyanine Green Nanoparticles

The purpose of this study was to develop a nanoparticle (NP) drug-loading system that enhances the efficiency of indocyanine green (ICG) entry into the tissue under focused ultrasound optimization and, in turn, enables more efficient identification and photothermal therapy (PTT) of the tumor. The new NPs were prepared by assembling intermolecular disulfide bonds to form human serum albumin (HSA) NPs and then conjugating those with ICG dye. The NP material was used to test the sensitivity of near-infrared fluorescence imaging and photoacoustic tumor imaging in vitro and in vivo. In addition, the combination of HSA-ICG NPs, focused ultrasound, and microbubbles was used to test PTT on the tumor. HSA-ICG NPs had good biocompatibility and were only a little toxic to cells and mice. In addition, they obviously enhanced tumor near-infrared fluorescence and photoacoustic bimodal imaging. Combined with HSA-ICG NPs, the depth of photoacoustic imaging was increased. Moreover, ICG that was absorbed in the HSA NPs promoted optical absorption in the near-infrared region, which greatly enhanced the PTT treatment's efficiency. This new bimodal tumor-imaging agent enhances the therapeutic effect of PTT and improves the detection of tumors in vivo, thus presenting great potential for use in clinical studies.

The Use of Indocyanine Green Fluorescence Angiography in Pediatric Surgery: A Systematic Review and Narrative Analysis

Purpose: Indocyanine green fluorescence angiography (ICG-FA) is a validated non-invasive imaging technique used to assess tissue vascularization and guide intraoperative decisions in many surgical fields including plastic surgery, neurosurgery, and general surgery. While this technology is well-established in adult surgery, it remains sparsely used in pediatric surgery. Our aim was to systematically review and provide an overview of all available evidence on the perioperative use of indocyanine green fluorescence angiography in pediatric surgical patients. Methods: We conducted a systematic review with narrative synthesis in conformity with the PRISMA guidelines using PubMed, Medline, All EBM Reviews, EMBASE, PsycINFO, and CINAHL COMPLETE databases to identify articles describing the perioperative use of ICG-FA in pediatric patients. Two independent authors screened all included articles for eligibility and inclusion criteria. We extracted data on study design, demographics, surgical indications, indocyanine green dose, and perioperative outcomes. We developed a risk of bias assessment tool to evaluate the methodological quality of included studies. Results: Of 1,031 articles retrieved, a total of 64 articles published between 2003 and 2020 were included reporting on 664 pediatric patients. Most articles were case reports and case series (n = 36; 56%). No adverse events related to ICG-FA were reported in the included articles. Risk of bias was high. We did not conduct a meta-analysis given the heterogeneous nature of the populations, interventions, and outcome measures. A narrative synthesis is presented. Conclusion: Indocyanine green fluorescence angiography is a safe imaging technology and its use is increasing rapidly in pediatric surgical specialties. However, the quality of evidence supporting this trend currently appears low. Case-control and randomized trials are needed to determine the adequate pediatric dose and to confirm the potential benefits of ICG-FA in pediatric surgical patients. Systematic Review Registration: This study was registered on Prospero a priori, identifier: CRD42020151981.

Flow-augmentation bypass for moyamoya disease

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease with unknown etiology, which is characterized by progressive steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network formation at the base of the brain. MMD has an intrinsic temporal nature to attempt a gradual conversion of the vascular supply for the brain from intracranial/internal carotid (IC) system to extracranial/external carotid (EC) system, so called "IC-EC conversion." Compatible cerebrovascular angio-architecture could be found in association with a variety of conditions such as neuro-fibromatosis type-1, Down's syndrome and cranial irradiation, which is called as moyamoya syndrome, akin/quasi MMD, or secondary MMD. Diagnosis of moyamoya vasculopathy, either idiopathic or secondary, is clinically important because flow-augmentation bypass is markedly beneficial for this entity to prevent cerebral ischemic attack by improving cerebral blood flow. Moreover, recent evidence indicated that flow-augmentation bypass could prevent re-bleeding in hemorrhagic MMD patients. Based on these backgrounds, there is a worldwide increase in the number of MMD patients undergoing bypass surgery. We sought to demonstrate our standard surgical procedure of superficial temporal artery-middle cerebral artery bypass with indirect pial synangiosis for MMD and its technical pitfall. We also discuss the intrinsic peri-operative hemodynamics of MMD after bypass surgery, including local cerebral hyper-perfusion and characteristic hemodynamic ischemia caused by watershed shift phenomenon. The aim of this review article is to understand the basic pathology of MMD, which is essential for complication avoidance while conducting flow-augmentation bypass for MMD.

Quantitative Analysis of Near-Infrared Indocyanine Green Videoangiography for Predicting Functional Outcomes After Spinal Intramedullary Ependymoma Resection

BACKGROUND

One of the most critical steps in surgery for spinal intramedullary ependymomas is the resection of small feeding arteries from the anterior spinal artery with anatomical preservation of the normal circulation of the ventral spinal cord.

OBJECTIVE

To quantitatively analyze the microcirculation of the ventral spinal cord by near-infrared indocyanine green videoangiography (ICG-VA) after the spinal intramedullary ependymoma resection.

METHODS

This retrospective study included 12 patients (7 male and 5 female; average age 55.2 years, range 36-79 years). Patients' neurological conditions were assessed based on the modified McCormick functional schema of grade 1 (neurologically normal) to 5 (severe deficit). Postoperative functional assessment was conducted at least 3 months after surgery. Quantitative analysis of vascular flow dynamics was carried out following spinal intramedullary ependymoma resection. Fluorescence intensities were measured and the indocyanine green (ICG) intensity-time curves were analyzed and compared with the functional outcomes after surgery.

RESULTS

Microscopically total or subtotal resection of the intramedullary ependymoma was achieved in all cases. Average peak time on ICG-VA was significantly shorter in the postoperative functional grade 1 to 2 group than in the postoperative functional grade 3 to 5 group, but there was no significant difference in average peak intensity between the 2 groups. Postoperative functional grade and the peak time of ICG, but not peak intensity, appeared correlated.

CONCLUSION

To the best of our knowledge, this is the first report showing that quantitative analysis of ICG-VA may predict functional outcomes after spinal intramedullary ependymoma resection.

Matching Selection of Donor-Recipient Vessels in Revascularization Surgery Effectively Reduce the Incidence of Postoperative Hyperperfusion Syndrome in Adult Moyamoya Disease: A Retrospective Comparison Study

INTRODUCTION

Cerebral hyperperfusion syndrome (CHS) is one of the most serious complications after revascularization surgery in patients with moyamoya disease (MMD). However, there are few effective measures to prevent the occurrence of CHS.

OBJECTIVE

The present study aims to examine the effect of the method about matching selection of donor-recipient vessels during revascularization surgery on the incidence of postoperative CHS in adult MMD patients.

METHODS

216 Chinese adult patients with MMD received surgery treatment between January 2018 and December 2019 in our hospital were enrolled in this study. 191 out of 216 patients were included in this study. Matching selection method was defined as follows: (1) blood flow: the direction of blood flow and speed of the donor artery and potential receptor arteries were measured by flow 800 indocyanine green video angiography; (2) vascular diameter: the diameters of the donor artery and potential receptor arteries by a miniature ruler. Only the artery with antegrade flow and with smallest difference in flow speed and diameter with the donor artery will be selected as the receptor artery to perform anastomosis. Matching selection was performed from January 2019. Digital subtraction angiography was performed in all patients for initial MMD diagnosis. Perioperative cerebral perfusion and related clinical symptoms were monitored. Clinical characteristics, contralateral progression, and risk factors were reviewed. The incidence of CHS and the correlation of CHS with baseline characteristics or clinical conditions were analyzed.

RESULTS

Of these 191 patients, 82 patients received matching selection of donor-recipient vessels during revascularization surgery and 109 patients without. The postoperative CHS incidence in the matching group was 3.66%, which was much lower than that in the nonmatching group (15.60%). Multivariate analysis did not reveal a significant risk factor between the progression group and the nonprogression group. Correlation analysis revealed only the matching selection method was significantly associated with the reduced postoperative CHS incidence in MMD patients.

CONCLUSIONS

The matching selection of donor-recipient vessels during revascularization surgery effectively reduces the incidence of postoperative CHS in adult patients with MMD.

Whole-Field Indocyanine Green Intensity Analysis to Intraoperatively Predict Cerebral Hyperperfusion Syndrome Following Superficial Temporal Artery-Middle Cerebral Artery Bypass: A Retrospective Case-Control Study in 7-Year Experience With 112 Cases

BACKGROUND

Intraoperative prediction of postoperative cerebral hyperperfusion syndrome (CHS) after cerebrovascular bypass surgery is challenging.

OBJECTIVE

To conduct a retrospective case-control study with indocyanine green (ICG) intensity analysis of the superficial temporal artery-middle cerebral artery (STA-MCA) bypass and investigate whether its washout pattern might be a marker for intraoperative prediction of CHS.

METHODS

Between 2012 and 2018, 6 of 112 patients (5.4%) that underwent STA-MCA bypass exhibited CHS. We selected 5 patients with CHS (3 with atherosclerotic cerebrovascular disease [ASCVD] and 2 with moyamoya) and 15 patients without CHS (60% ASCVD and 40% moyamoya) as a matched control group. During prebypass and postbypass, washout times (WTs) for the first 10%, 25%, 50%, and 75% of maximum ICG intensity measured in the whole-camera field were compared between groups. The changes in WT (ΔWT) from prebypass to postbypass for each ICG intensity level were compared between groups. The cutoff ΔWTs, sensitivities, and specificities were also calculated.

RESULTS

Postbypass WTs were significantly longer in the CHS group than the control group at all ICG intensities (P < .05). ΔWT was significantly greater in the CHS group than the control group for the first 10%, 25%, and 50% ICG intensities (P < .001). A cutoff ΔWT of ≥2.66 s for the first 50% ICG intensity showed a sensitivity of 100% and specificity of 100%.

CONCLUSION

We found that a ΔWT ≥2.66 s for the first 50% ICG intensity could be an intraoperative predictive factor for CHS.

Applications of Microscope-Integrated Indocyanine Green Videoangiography in Cerebral Revascularization Procedures

Indocyanine green videoangiography (ICG-VA) is a near-infrared range fluorescent marker used for intraoperative real-time assessment of flow in cerebrovascular surgery. Given its high spatial and temporal resolution, ICG-VA has been widely established as a useful technique to perform a qualitative analysis of the graft patency during revascularization procedures. In addition, this fluorescent modality can also provide valuable qualitative and quantitative information regarding the cerebral blood flow within the bypass graft and in the territories supplied. Digital subtraction angiography (DSA) is considered to be the gold standard diagnostic modality for postoperative bypass graft patency assessment. However, this technique is time and labor intensive and an expensive interventional procedure. In contrast, ICG-VA can be performed intraoperatively with no significant addition to the total operative time and, when used correctly, can accurately show acute occlusion. Such time-sensitive ischemic injury detection is critical for flow reestablishment through direct surgical management. In addition, ICG has an excellent safety profile, with few adverse events reported in the literature. This review outlines the chemical behavior, technical aspects, and clinical implications of this tool as an intraoperative adjunct in revascularization procedures.

Multispectrum Indocyanine Green Videography for Visualizing Brain Vascular Pathology

OBJECTIVE

Currently, neurosurgical vascular surgery frequently uses indocyanine green (ICG)-videography (VG) to evaluate the blood flow in brain vessels. Although ICG-VG delineates intravascular ICG fluorescence as a high-intensity signal in gray-scale with dark background, it is hard to identify anatomical structures, including vasculature or surgical devices simultaneously. This report developed combination of a near-infrared (NIR) camera with particular sensitivity and an optical filter to observe the blood-flow conditions and anatomical structures.

METHODS

To overcome the specific issues of ICG-VG, we applied a high-sensitivity camera with a 980-nm NIR component to delineate anatomical and fluorescence images, detecting signals between 830 and 1000 nm simultaneously during operation. We used a diluted ICG phantom to evaluate fluorescence signal changes by changing wavelength of the emission light. For clinical use, we used a high-sensitivity NIR camera with a high-pass filter on a surgical microscope. The new NIR system detected signals between 770 and 1000 nm, and the lighting system illuminated objects mainly at 980-nm wavelength. Both images with the blood flow and anatomical structures were projected to the smart glasses in real time.

RESULTS

In the phantom experiment, we found that the emission light with wide band widths (575-800 nm) evoked various intensities of ICG fluorescence. This new NIR system allowed us to observe ICG fluorescence and anatomical structures without image fusion or time-delay. The both information of anatomy and fluorescence was projected on wearable smart glasses. Furthermore, the new NIR system detected ICG-fluorescence signals for a longer duration than the original camera, which allowed us to achieve careful and detailed observation of more vasculature and fine vessels.

CONCLUSIONS

This study proposes a new NIR system and emphasizes simultaneous observation of anatomy and fluorescence signals during operation. It paves the way for further possibilities in the development of optical systems. To understand the natural phenomena and combination of different scientific and clinical fields, it might be important to understand and combine not only fluorescence, but also natural science, optics, and background pathology. This simple system would be available for neuroendoscope and robotic surgery.

Intraoperative evaluation of local cerebral hemodynamic change by indocyanine green videoangiography: prediction of incidence and duration of postoperative transient neurological events in patients with moyamoya disease

OBJECTIVE

Transient neurological events (TNEs) occur frequently in the acute phase after direct bypass surgery for moyamoya disease (MMD), but there is currently no way to predict them. FlowInsight is a specialized software for analyzing indocyanine green (ICG) videoangiography taken with a surgical microscope. The purpose of this study was to investigate whether intraoperative evaluation of local hemodynamic changes around anastomotic sites using FlowInsight could predict the incidence and duration of TNEs.

METHODS

From patients who were diagnosed with MMD in our hospital between August 2014 and March 2017 and who underwent superficial temporal artery-middle cerebral artery bypass surgery, we investigated 25 hemispheres (in 22 patients) in which intraoperative ICG analysis was performed using FlowInsight. To evaluate the local cerebral hemodynamics before and after anastomosis, regions of interest were set at 3 locations on the brain surface around the anastomotic site, and the mean cerebral blood flow (CBF), mean gradation (Grad), mean transit time (MTT), and mean time to peak (TTP) were calculated from the 3 regions of interest. Furthermore, the change rate in CBF (ΔCBF [%]) was calculated using the formula (postanastomosis mean CBF - preanastomosis mean CBF)/preanastomosis mean CBF. ΔGrad (%), ΔMTT (%), and ΔTTP (%) were similarly calculated.

RESULTS

Postoperative stroke without TNE occurred in 2 of the 25 hemispheres. These 2 hemispheres (in 2 patients) were excluded from the study, and data from the remaining 23 hemispheres (in 20 patients) were analyzed. For each parameter (ΔCBF, ΔGrad, ΔMTT, and ΔTTP) calculated by FlowInsight, the difference between the groups with and without TNEs was significant. The median values for ΔCBF and ΔGrad were significantly higher in the TNE group than in the no-TNE group (ΔCBF 30.13 vs 3.54, p = 0.0106; ΔGrad 62.05 vs 10.78, p = 0.00435), whereas the median values for ΔMTT and ΔTTP were significantly lower in the TNE group (ΔMTT -16.90 vs -7.393, p = 0.023; ΔTTP -29.07 vs -7.02, p = 0.00342). Comparison of the area under the curve (AUC) for each parameter showed that ΔTTP had the highest AUC and was the parameter with the highest diagnostic accuracy (AUC 0.857). The Youden index revealed that the optimal cutoff value of ΔTTP was -11.61 (sensitivity 77.8%, specificity 71.4%) as a predictor of TNEs. In addition, Spearman's rank correlation coefficients were calculated, and ΔCBF, ΔGrad, ΔMTT, and ΔTTP each showed a strong correlation with the duration of TNEs. The larger the change in each parameter, the longer the TNEs persisted.

CONCLUSIONS

Intraoperative ICG videoangiography findings were correlated with the occurrence and duration of TNEs after direct bypass surgery for MMD. Screening for cases at high risk of TNEs can be achieved by ICG analysis using FlowInsight.

Quantitative Blood Flow Assessment by Multiparameter Analysis of Indocyanine Green Video Angiography

BACKGROUND

Measurements of quantitative blood flow are crucial during brain vascular surgery. Indocyanine green video angiography (ICG-VAG) is an accepted method of blood flow visualization; however, quantitative techniques have not yet been established. Thus, the aim of this study was to further develop ICG analysis for visualizing intraoperative flow changes.

METHODS

We conducted basic experiments and clinical investigations to establish a relationship between ICG-VAG and measured blood flow. We evaluated several parameters and identified optimal indicators that precisely reflect blood (or fluid) flow. Both in vitro and in vivo studies were performed to calculate the interval between baseline and the intensity peak (Grad) and to measure actual flow rate.

RESULTS

Grad and actual flow rate showed good exponential correlation, with R² values of 0.90 in vitro and 0.82 in vivo. In a representative patient (case 3), we performed intraoperative flow analysis using FlowInsight, which identified a marked elevation in Grad on the brain surface. Because this observation is predictive of brain hyperperfusion, we used these data to carefully manage blood pressure postoperatively.

CONCLUSIONS

Grad is the optimum parameter for estimating flow conditions. Although ICG-VAG provides only visual profiles of blood circulation in the brain, this procedure has the potential to be widely used in clinical situations. ICG-based flow measurement can be used to identify normal and abnormal blood flow conditions, such as graft flow and vascular pathology. The novelty of this technique is that the fluorescence intensity of Grad enables surgeons to quantitatively measure real blood flow.

Correlation between reduction in microvascular transit time after superficial temporal artery-middle cerebral artery bypass surgery for moyamoya disease and the development of postoperative hyperperfusion syndrome

OBJECTIVE Hyperperfusion syndrome (HPS) is a notable complication that causes various neurological symptoms after superficial temporal artery (STA)-middle cerebral artery (MCA) bypass surgery for moyamoya disease (MMD). The authors used intraoperative indocyanine green (ICG) videoangiography to measure the change in microvascular transit time (MVTT) after bypass surgery. An analysis was then conducted to identify the correlation between change in MVTT and presence of postoperative HPS. METHODS This study included 105 hemispheres of 81 patients with MMD who underwent STA-MCA single bypass surgery between January 2010 and January 2015. Intraoperative ICG videoangiography was performed before and after bypass surgery. The MVTT was calculated from the ICG time intensity curve recorded in the pial arterioles and venules. Multivariate logistic regression analysis was conducted to test the effect of multiple variables, including the change in MVTT after bypass surgery, on postoperative HPS. RESULTS Postoperative HPS developed in 28 (26.7%) of the 105 hemispheres operated on. MVTT was reduced significantly after bypass surgery (prebypass 5.34 ± 2.00 sec vs postbypass 4.12 ± 1.60 sec; p < 0.001). The difference between prebypass and postbypass MVTT values, defined as ΔMVTT, was significantly greater in the HPS group than in the non-HPS group (2.55 ± 2.66 sec vs 0.75 ± 1.78 sec; p < 0.001). Receiver operating characteristic curve analysis revealed that the optimal cutoff point of ΔMVTT was 2.6 seconds (sensitivity 46.4% and specificity 85.7% as a predictor of postoperative HPS). A ΔMVTT > 2.6 seconds was an independent predictor of HPS in multivariate analysis (hazard ratio 4.88, 95% CI 1.76-13.57; p = 0.002). CONCLUSIONS MVTT in patients with MMD was reduced significantly after bypass surgery. Patients with a ΔMVTT > 2.6 seconds tended to develop postoperative HPS. Because ΔMVTT can be easily measured during surgery, it is a useful diagnostic tool for identifying patients at high risk for HPS after STA-MCA bypass surgery for MMD.

Significance of Cerebral Blood Flow Analysis in the Acute Stage after Revascularization Surgery for Moyamoya Disease

Moyamoya disease is a chronic, occlusive cerebrovascular disease with unknown etiology characterized by steno-occlusive changes at the terminal portion of the internal carotid artery, either bilaterally or unilaterally, and an abnormal vascular network at the base of the brain. Surgical revascularization such as extracranial-intracranial (EC-IC) bypass is the preferred procedure for moyamoya disease. Despite the favorable long-term outcome, cerebral infarction and hyperperfusion syndrome are potential complications of this procedure, which can lead to neurological deterioration in the acute stage. In light of the similar clinical presentations between perioperative ischemia and hyperperfusion, it is essential to attempt a prompt cerebral blood flow (CBF) measurement in the acute stage after EC-IC bypass for moyamoya disease to differentiate these distinct pathologies, because the management of cerebral ischemia and hyperperfusion is contradictory to each other. Routine CBF analysis by single-photon emission computed tomography and/or magnetic resonance imaging not only facilitated a safer perioperative management but also provided important information about dynamic pathology of the hemodynamic conversion in the acute stage after revascularization surgery for moyamoya disease. We represent the current status of CBF analysis during the perioperative period of revascularization surgery for moyamoya disease, and sought to discuss its significance and efficacy to avoid surgical complications.

Radial Artery Grafts as Rescue Strategy for Patients with Moyamoya Disease for Whom Conventional Revascularization Failed

BACKGROUND

Failure of direct revascularization with superficial temporal artery (STA)-middle cerebral artery (MCA) bypass for Moyamoya disease (MMD) is comparatively rare. However, for those cases where a bypass fails to prevent further ischemic attacks, safe and efficient rescue strategies are needed. We present our experience with radial artery grafts for secondary revascularization of MMD.

METHODS

Between April 2007 and April 2014, we have performed STA-MCA bypass in 182 patients diagnosed with Moyamoya vasculopathy. Four patients with typical MMD who had an unsuccessful STA-MCA bypass required additional revascularization because they remained symptomatic. Digital subtraction angiography revealed delayed STA graft failure in these patients, who continued to have transient ischemic attacks after the initial surgery. Cerebral blood flow studies confirmed persistent impairment of cerebrovascular reserve capacity. As an escape strategy, we performed radial artery graft bypass surgery from the external carotid artery to the M2 or M3 portion of the MCA.

RESULTS

The median duration between the 2 surgeries was 10 months. The mean follow-up period after rescue revascularization was 8.5 ± 3.3 months. Revascularization with the radial artery graft was successful in all cases without perioperative complications. Postoperatively, none of the patients experienced further cerebrovascular events. After 3 months, digital subtraction angiography revealed patent radial artery grafts and adequate revascularization in 3 patients; 1 patient presented with bypass graft failure but had developed transdural collateral vessels contributing to the filling of the cerebral vasculature.

CONCLUSIONS

Rescue bypass with a radial artery graft provides a useful function. Although delayed graft failure may occur, this procedure is successful if the patients remain symptom free with the development of collateral flow.

Quantitative assessment of hemodynamic changes during spinal dural arteriovenous fistula surgery

We aimed to evaluate the efficacy of FLOW 800 (Carl Zeiss Meditec, Jena, Thuringia, Germany) with indocyanine green (ICG) videoangiography for the quantitative assessment of flow dynamics in spinal dural arteriovenous fistula (dAVF) surgeries. We prospectively enrolled nine patients with spinal dAVF diagnosed within the past year and performed FLOW 800 analyses using ICG videoangiography before and after surgical obliteration of the fistula. A color-coded map was semi-automatically generated by FLOW 800 and used for high-resolution visualization of the vasculature and instant interpretation of the dynamic flow changes. The FLOW 800-specific hemodynamic parameters were employed for real-time measurements of parenchymal perfusion alterations. Overall, 18 intraoperative FLOW 800 analyses using ICG videoangiography were performed in nine patients. The color-coded map aided the detection and complete obliteration of the fistulas in all patients and the results were verified by postoperative spinal digital subtraction angiography. The transit time parameter was significantly shorter in the preobliteration phase than in the postobliteration phase (p < 0.01), the rise time parameter exhibited the same pattern (p = 0.08) and maximum intensity and blood flow index were not significantly different between these phases. FLOW 800 with ICG videoangiography provided an intuitive and objective understanding of blood flow dynamics intraoperatively and enabled easy and confident identification and treatment of this pathology. The FLOW 800-specific hemodynamic analyses provided additional perfusion information that enabled real-time measurements of parenchymal perfusion alterations. FLOW 800 with ICG videoangiography is useful for intraoperative quantitative assessment of flow dynamics, facilitating safety and confidence in the treatment of spinal dAVF.

Novel techniques of real-time blood flow and functional mapping: technical note

There are two main approaches to intraoperative monitoring in neurosurgery. One approach is related to fluorescent phenomena and the other is related to oscillatory neuronal activity. We developed novel techniques to visualize blood flow (BF) conditions in real time, based on indocyanine green videography (ICG-VG) and the electrophysiological phenomenon of high gamma activity (HGA). We investigated the use of ICG-VG in four patients with moyamoya disease and two with arteriovenous malformation (AVM), and we investigated the use of real-time HGA mapping in four patients with brain tumors who underwent lesion resection with awake craniotomy. Real-time data processing of ICG-VG was based on perfusion imaging, which generated parameters including arrival time (AT), mean transit time (MTT), and BF of brain surface vessels. During awake craniotomy, we analyzed the frequency components of brain oscillation and performed real-time HGA mapping to identify functional areas. Processed results were projected on a wireless monitor linked to the operating microscope. After revascularization for moyamoya disease, AT and BF were significantly shortened and increased, respectively, suggesting hyperperfusion. Real-time fusion images on the wireless monitor provided anatomical, BF, and functional information simultaneously, and allowed the resection of AVMs under the microscope. Real-time HGA mapping during awake craniotomy rapidly indicated the eloquent areas of motor and language function and significantly shortened the operation time. These novel techniques, which we introduced might improve the reliability of intraoperative monitoring and enable the development of rational and objective surgical strategies.

Intraoperative assessment of cortical perfusion by indocyanine green videoangiography in surgical revascularization for moyamoya disease

BACKGROUND

Postoperative hyperperfusion is a potential complication of the direct bypass procedure for moyamoya disease (MMD). However, no reliable modality is available yet for the prediction of postoperative hyperperfusion during surgery for MMD. This study aimed to investigate whether semiquantitative analysis of indocyanine green (ICG) videoangiography could contribute to the prediction of postoperative hyperperfusion in MMD.

METHODS

This study included 12 hemispheres from 10 patients who underwent surgical revascularization for MMD. Intraoperative ICG videoangiography was performed before and after a direct bypass procedure. The ICG intensity-time curves were semiquantitatively analyzed to evaluate cortical perfusion by calculating the blood flow index (BFI). Using single-photon emission computed tomography (SPECT), postoperative cerebral blood flow measurements were performed thrice: immediately, and 2 and 7 days after surgery.

RESULTS

BFI significantly increased from 21.3 ± 10.5 to 38.4 ± 20.0 after bypass procedures in all the hemispheres (p < 0.01). The ratio of BFI before and after the bypass procedure was 2.4 ± 2.0, ranging from 0.5 to 8.0. Postoperative hyperperfusion was observed in nine of the 12 operated hemispheres within 7 days after surgery. Of these, three hemispheres developed hyperperfusion immediately after surgery. In the adult cases, the increase in the ratio of BFI after bypass was significantly greater in those who developed hyperperfusion immediately after surgery than in those who did not (6.5 ± 0.5 vs. 1.8 ± 2.1, p < 0.01). In contrast, no significant increase in BFI was observed in the pediatric MMD patients who experienced immediate hyperperfusion. No correlation between the changes in BFI and the occurrence of delayed hyperperfusion was observed.

CONCLUSIONS

Our results suggest that semiquantitative analysis of BFI by intraoperative ICG videoangiography is useful in evaluating changes in cortical perfusion after bypass procedures for MMD and can predict the occurrence of early-onset hyperperfusion in MMD patients after direct bypass.