Application of Indocyanine Green During Arteriovenous Malformation Surgery: Evidence, Techniques, and Practical Pearls

5-ALA induced PpIX fluorescence spectroscopy in neurosurgery: a review

The review begins with an overview of the fundamental principles/physics underlying light, fluorescence, and other light-matter interactions in biological tissues. It then focuses on 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence spectroscopy methods used in neurosurgery (e.g., intensity, time-resolved) and in so doing, describe their specific features (e.g., hardware requirements, main processing methods) as well as their strengths and limitations. Finally, we review current clinical applications and future directions of 5-ALA-induced protoporphyrin IX (PpIX) fluorescence spectroscopy in neurosurgery.

Can exoscope improve brain AVMs surgery?

The advantages of the surgical view provided by the exoscope have been described before, although reports of its application to brain arteriovenous malformation (AVM) surgery are lacking. The ampler field of view and magnification up to ×24 allow for enhanced visualization during microsurgical procedures. Furthermore, the live visualization provided by indocyanine green video angiography (ICG-VA) helps emphasize the hemodynamics of AVMs, even allowing the detection of possible residual vein arterialization as an indirect expression of nidal remnants. With this illustrative video showing the resection of a hemorrhagic right frontoinsular Spetzler-Martin grade III AVM, the authors describe the technical implications of exoscope brain AVM surgery using the Olympus ORBEYE 4K-3D, with a final focus on ICG-VA as an asset. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23114.

Pre-operative embolization of a complex systemic to pulmonary vascular malformation

A 38-year-old male patient presenting with mild exertional dyspnea was noted to have a lingular opacity on chest radiograph. CT of the chest demonstrated an unusual complex inferior lingular vascular malformation with branches arising from the left internal thoracic artery and the left inferior diaphragmatic artery via the celiac artery. There was suspected communication with both pulmonary arterial and venous branches. Following thorough assessment and comprehensive clinical investigation, the patient elected to proceed to definitive surgical management due to potential risk of life-threatening hemoptysis. Interventional radiology performed pre-operative diagnostic angiography and embolization of the systemic feeding arteries. The patient proceeded to have an uncomplicated video-assisted thoracoscopic surgery segmentectomy and was discharged the next day. The patient was asymptomatic at follow-up with complete resolution of the malformation on CT at 6 months. We discuss an uncommon pathology which benefited from multidisciplinary management including successful pre-operative endovascular embolization.

New approaches for brain arteriovenous malformations-related epilepsy

BACKGROUND

The purpose of this review is to present the current literature and to highlight the most recent findings in brain arteriovenous malformations (bAVM)-related epilepsy research.

METHODS

We searched Medline, PubMed, Biblioinserm, Cochrane Central to study the latest research reports about the different factors that could be responsible for the genesis of bAVM-related epilepsy. We analyzed if epileptogenesis has any characteristics traits and its relation with the vascular malformation. The results of different treatments on epilepsy were considered. Typical errors that may lead towards incorrect or worse management of the seizures for these patients were also examined.

RESULTS

The development of bAVM results from multifactorial etiologies and bAVM-related epileptogenesis is likely specific for this pathology. Different types of evidence demonstrate a bidirectional relationship between bAVM and epilepsy. Currently, there is not enough published data to determine what may be the right management for these patients.

CONCLUSIONS

A better understanding of epileptogenesis in conjunction with knowledge of the complex alterations of structures and functions following bAVM-related seizures is necessary. Identification of biomarkers that can identify subgroups most likely to benefit from a specific intervention are needed to help guide clinical management. A new concept for the treatment of epilepsy related to an unruptured bAVM that cannot be treated invasively is proposed as well as new therapeutic perspectives. The next necessary step will be to propose additional algorithms to improve the development of future trials.

All fiber-based illumination system for multi-exposure speckle imaging

Monitoring blood flow is critical to treatment efficacy in many surgical settings. Laser speckle contrast imaging (LSCI) is a simple, real-time, label-free optical technique for monitoring blood flow that has emerged as a promising technique but lacks the ability to make repeatable quantitative measurements. Multi-exposure speckle imaging (MESI) is an extension of LSCI that requires increased complexity of instrumentation, which has limited its adoption. In this paper, we design and fabricate a compact, fiber-coupled MESI illumination system (FCMESI) that is substantially smaller and less complex than previous systems. Using microfluidics flow phantoms, we demonstrate that the FCMESI system measures flow with an accuracy and repeatability equivalent to traditional free space MESI illumination systems. With an in vivo stroke model, we also demonstrate the ability of FCMESI to monitor cerebral blood flow changes.

Evaluation of the Utility of Indocyanine Green Video Angiography in Cerebral Arteriovenous Malformation Surgery

OBJECTIVE

To assess the utility of intraoperative indocyanine green video angiography (ICG-VA) during microsurgical resection of arteriovenous malformations (AVMs).

METHODS

Data of the 24 patients, who were surgically treated for AVM using intraoperative ICG-VA, were reviewed retrospectively. Postoperative digital subtraction angiography (DSA) was performed in all patients before they regained consciousness and became fully awake, and the results were compared with those obtained with intraoperative ICG-VA. A scheduled DSA was performed in all patients in the third, sixth, and 12th postoperative months as well.

RESULTS

Authors retrospectively analyzed the records of intraoperative ICG-VA application of all 24 patients. Though the exposures were limited and the image qualities were poor at higher magnification on the surgical microscope within deep surgical fields, the AVM niduses, feeding arteries, draining veins, and their relations to normal vasculature were observed precisely with ICG-VA in all the procedures. Furthermore, the visualization was not qualified enough to identify these pathological vascular structures accurately before evacuating and irrigating the layer of blood clots that obscure the view in patients who presented with hemorrhage. In a patient in our series, a residual nidus in the tail of the caudate nucleus was detected with immediate postoperative DSA which was not revealed by terminal assessment with final intraoperative ICG-VA.

CONCLUSIONS

Intraoperative ICG-VA is particularly effective in the identification of the feeder, nidus, and drainer and in the assessment of the flow dynamics of the nidus in cerebral AVM surgery. It may be a quick and safe technique for intraoperative imaging of the angioarchitecture of superficial AVMs, but it may be less helpful for deep-seated lesions. Furthermore, this method alone may not be useful in the identification of residual disease or improvement of the clinical outcomes. DSA has remained the gold standard for confirming AVM obliteration. Despite the technical limitations associated with ICG-VA, a combination of intraoperative ICG-VA and immediate postoperative DSA may advance the safety and efficacy of AVM surgery.

Spontaneous regression of multiple flow-related aneurysms following treatment of an associated brain arteriovenous malformation: A case report

Introduction

There is no consensus in the treatment strategy of intracranial aneurysms (IAs) associated with brain arteriovenous malformation (BAVM). In particular, it is unknown if a more aggressive approach should be considered in patients harboring a BAVM, in whom multiple aneurysms or a history of aneurysmal subarachnoid hemorrhage (aSAH) is present.

Case presentation

We report on an elderly woman harboring multiple aneurysms with a history of SAH due to rupture of an unrelated IA. On evaluation, she was also found to harbor a contralateral, left parietal convexity BAVM. Following resection of the latter, spontaneous regression of two large flow-related aneurysms was encountered.

Discussion

We discuss the therapeutic decision-making, risk stratification, and functional outcome in this patient with regard to the pertinent literature on the risk of hemorrhage in IAs associated with BAVM.

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.

Role of Indocyanine Green with FLOW 800 in Removal of Hidden Arteriovenous Malformations

OBJECTIVE

Indocyanine green videoangiography (ICG-VA) with FLOW 800 (Carl Zeiss AG) has been used as a visualization tool to guide arteriovenous malformation (AVM) surgery since 2011. We performed a systematic review and evaluated the quality of evidence available on this topic. In addition, we present a series of our own cases demonstrating the unique use of ICG-VA in the localization and removal of deeper seated AVMs.

METHODS

Using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines for systematic reviews, we identified studies related to ICG-VA with FLOW 800 in AVM surgeries using search terms. The studies were screened and reviewed, and the quality of evidence was analyzed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) criteria. We performed a retrospective review of our own cases of AVM removal with ICG-VA and FLOW 800.

RESULTS

Our search revealed 27 relevant studies, 17 of which met our inclusion criteria. The quality of the body of evidence was determined to be "very low" using the GRADE criteria. We used ICG-VA with FLOW 800 analysis for 14 cases of microsurgical AVM removal. This technique provided unique insights into the localization of deep seated AVMs in 8 cases (57%). No residual AVM was found when assessed by the 6-month follow-up angiogram.

CONCLUSIONS

We present cases highlighting the usefulness of this technique for the localization of certain AVMs. We believe the use of ICG-VA can guide the removal of deeper seated AVMs, because it can reveal surface feeders and draining veins that can be followed to a hidden nidus. Larger, registry-based studies are needed to confirm these findings and improve the overall quality of evidence.

Endoluminal Biopsy for Molecular Profiling of Human Brain Vascular Malformations

BACKGROUND AND OBJECTIVES

Ras-mitogen-activated protein kinase (MAPK) signaling abnormalities occur in most brain arteriovenous malformations (bAVMs). No means exist to molecularly profile bAVMs without open surgery, limiting precision medicine approaches to treatment. Here, we report use of endoluminal biopsy of the vessel lumen of bAVMs to characterize gene expression and blood flow-mediated transcriptional changes in living patients.

METHODS

Endoluminal biopsy and computational fluid dynamic modeling (CFD) were performed in adults with unruptured AVMs with cerebral angiography. Each patient underwent surgical resection and cell sampling from a contiguous arterial segment. Fluorescence-assisted cell sorting enriched endothelial cells, which were sequenced on an Illumina HiSeq 4000 sequencer. Gene expression was quantified with RNA sequencing (RNAseq). Differential gene expression, ontology, and correlative analyses were performed. Results were validated with quantitative reverse transcription PCR (RT-qPCR).

RESULTS

Endoluminal biopsy was successful in 4 patients without complication. Endoluminal biopsy yielded 269.0 ± 79.9 cells per biopsy (control 309.2 ± 86.6 cells, bAVM 228.8 ± 133.4 cells). RNAseq identified 106 differentially expressed genes (DEGs) in bAVMs (false discovery rate ≤0.05). DEGs were enriched for bAVM pathogenic cascades, including Ras-MAPK signaling (p < 0.05), and confirmed with RT-qPCR and a panel predictive of MAPK/extracellular signal-regulated kinase inhibitor response. Compared to patient-matched surgically excised tissues, endoluminal biopsy detected 83.3% of genes, and genome-wide expression strongly correlated (Pearson r = 0.77). Wall shear stress measured by CFD correlated with inflammatory pathway upregulation. Comparison of pre-embolization and postembolization samples confirmed flow-mediated gene expression changes.

DISCUSSION

Endoluminal biopsy allows molecular profiling of bAVMs in living patients. Gene expression profiles are similar to those of tissues acquired with open surgery and identify potentially targetable Ras-MAPK signaling abnormalities in bAVMs. Integration with CFD allows determination of flow-mediated transcriptomic alterations. Endoluminal biopsy may help facilitate trials of precision medicine approaches to bAVMs in humans.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

Application of FLOW 800 in extracranial-to-intracranial bypass surgery for moyamoya disease

The surgical treatment of moyamoya disease is heavily reliant upon a real-time understanding of cerebral hemodynamics. The application of FLOW 800 allows the surgeon to semiquantify the degree of perfusion to the cerebral cortex following extracranial-to-intracranial (EC-IC) bypass surgery. The authors present three illustrative cases demonstrating common intraoperative findings prior to and following anastomosis using FLOW 800. All patients were diagnosed by catheter angiogram with moyamoya disease and noninvasive imaging demonstrating hemispheric hypoperfusion. Superficial temporal artery (STA)–to–middle cerebral artery (MCA or M4) bypasses were performed to augment intracranial perfusion. The patients tolerated the procedures well and were discharged without event in stable neurological condition.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21191

Influence of intraoperative vasopressor use on indocyanine green fluorescence angiography: first evaluation in an experimental model

Intraoperative indocyanine green (ICG) fluorescence angiography has gained popularity and acceptance in many surgical fields for the real-time assessment of tissue perfusion. Although vasopressors have the potential to preclude an accurate assessment of tissue perfusion, there is a lack of literature with regards to its effect on ICG fluorescence angiography. An experimental porcine model was used to expose the small bowel for quantitative tissue perfusion assessment. Three increasing doses of norepinephrine infusion (0.1, 0.5, and 1.0 µg/kg/min) were administered intravenously over a 25-min interval. Time-to-peak fluorescence intensity (TTP) was the primary outcome. Secondary outcomes included absolute fluorescence intensity and local capillary lactate (LCL) levels. Five large pigs (mean weight: 40.3 ± 4.24 kg) were included. There was no significant difference in mean TTP (in seconds) at baseline (4.23) as compared to the second (3.90), third (4.41), fourth (4.60), and fifth ICG assessment (5.99). As a result of ICG accumulation, the mean and the maximum absolute fluorescence intensity were significantly different as compared to the baseline assessment. There was no significant difference in LCL levels (in mmol/L) at baseline (0.74) as compared to the second (0.82), third (0.64), fourth (0.60), and fifth assessment (0.62). Increasing doses of norepinephrine infusion have no significant influence on bowel perfusion using ICG fluorescence angiography.

Augmented Reality Fluorescence Imaging in Cerebrovascular Surgery: A Single-Center Experience with Thirty-Nine Cases

BACKGROUND

Several intraoperative imaging methods exist in cerebrovascular surgery to visualize and analyze the vascular anatomy flow. A new method based on multispectral fluorescence (MFL) imaging of indocyanine green (ICG) video angiography (VA) allows real-time, augmented reality (AR) visualization of blood flow superimposed on white-light microscopic images. We describe our single-center experience using MFL AR in cerebrovascular surgery.

METHODS

Case descriptions are provided of cerebrovascular surgery with intraoperative use of MFL AR images performed at our institution from June 2018 to April 2020. MFL superimposes the blood flow in real time on white-light microscopic images. We used MFL AR imaging as well as standard ICG-VA visualization and intraoperative digital subtraction angiography (DSA) as a control.

RESULTS

A total of 39 cases (33 aneurysm clippings, 4 arteriovenous malformations, and 2 external carotid-internal carotid bypass surgeries), were performed using MFL technology-based AR visualization of ICG. MFL AR imaging and DSA showed a high correlation concerning aneurysm occlusion and vessel patency. In arteriovenous malformation resection surgery, MFL AR imaging facilitated early identification of the feeding arteries and draining veins. Because of increased sensitivity of MFL AR, a reduced dose of ICG could be used, allowing repeated intraoperative imaging. There were no postoperative complications, side effects, or technical problems related to the use of MFL AR imaging.

CONCLUSIONS

MFL AR is an easy-to-use adjunct in cerebrovascular surgery and shows a high correlation with intraoperative DSA. No interruption of the surgery is necessary because MFL AR images of the blood flow are superimposed in real time on white-light microscopic images.

Combined Use of Color Doppler Ultrasound and Contrast-Enhanced Ultrasound in the Intraoperative Armamentarium for Arteriovenous Malformation Surgery

BACKGROUND

Safety and efficacy in surgical treatment of cerebral arteriovenous malformations (AVMs) are dictated by thorough understanding of angioarchitectural features, intraoperative identification of feeding vessels, and appreciation of surrounding eloquent areas. Our aim was to describe the preliminary results of combined application of color Doppler ultrasound (CDUS) and contrast-enhanced ultrasound (CEUS) in a consecutive surgical series of AVM. We pointed out the tool's efficacy in distinguishing feeding from bystander vessels and in identifying pattern of venous drainage. We examined its role as an adjunct for semiquantitative evaluation of the nidus inflow.

METHODS

We used combined CDUS and CEUS in patients surgically treated for cerebral AVMs. We adopted these techniques following a designed protocol to guide safer AVM resection as an adjunct to indocyanine green videoangiography. Intraoperative assessment by ultrasound was performed before, during, and following nidus resection.

RESULTS

Four surgically treated cerebral AVMs availed of the ultrasound protocol. Postoperative conventional angiography showed complete resection of the AVMs. CDUS and CEUS proved to be valuable adjunctive tools to indocyanine green videoangiography and micro-Doppler in properly navigating and discerning vascular structures, especially vessel feeders from bystanders. The protocol allows us to identify flow direction, estimate blood velocity within the nidus, and appreciate flow modifications following temporary clipping. Ultimately, it allows us to evaluate the degree of nidus deafferentation, residual flow, restoration of venous drainage and absence of arteriovenous shunts.

CONCLUSIONS

The CDUS and CEUS protocol is safe and repeatable and works as real-time imaging, further supporting complete surgical resection of AVMs.