A prospective comparative study of microscope-integrated intraoperative fluorescein and indocyanine videoangiography for clip ligation of complex cerebral aneurysms

Application of fluorescein sodium videoangiography in aneurysm surgery

BACKGROUND

The use of fluorescent technologies in vascular neurosurgery emerged after indocyanine green video angiography (ICG-VA) was first described in 2003. As data supporting the efficiency of ICG in preventing postoperative complications has grown substantially, it has now established itself as the standard of care. However, the predominant literature centers on ICG techniques, leaving the evaluation of cost-effective fluorescein tools pending. We report the results of a prospective study in which we demonstrated the impact of intraoperative fluorescein videoangiography (FL-VA) in aneurysm surgery.

METHODS

Between December 2021 and September 2022, a total of 57 patients underwent craniotomy for intracranial aneurysm surgery. After aneurysm clipping, we administered a 0.5 mg/Kg of sodium fluorescein, and the intracranial area of interest was inspected through the microscope integrated module. The following data were collected: patient age and sex; number of clipped aneurysms; aneurysm location, size, and rupture status; Hunt Hess grade; intraoperative rupture; aneurysm calcification and thrombosed aneurysm; visualization of blood flow in perforating arteries; need for a clip adjustment after FL-VA analysis by neurosurgeon.

RESULTS

For the surgical clipping of 64 aneurysms in 57 patients, 80 FL-VA studies were performed. Clip adjustments were performed following FL-VA in 13 aneurysms. FL-VA had an impact on 20 % of the clipping. In seven aneurysms, clip adjustment was due to the "presence of residual aneurysm", in three cases due to the "presence of neck", and in three cases due to "adjacent vessel stenosis". Regarding the evaluation of flow in the perforating vessels, it was possible, with a good and detailed image in all cases.

CONCLUSION

The use of FL-VA has a significant impact in aneurysm surgery, enhancing effectiveness and safety. The dosage of 0.5 mg/kg administered is sufficient for assessing both aneurysm occlusion and the presence of flow in adjacent vessels.

Comparison of intraoperative sodium fluorescein and indocyanine green videoangiography during intracranial aneurysm and arteriovenous malformation surgery

OBJECTIVE

Indocyanine green (ICG) and sodium fluorescein (Na-Fl) are two fluorophores, which are used for videoangiography purposes. This prospective study reports our experience by using surgical microscopes equipped with two special filters. We compared the imaging efficacy of Na-FL and ICG videoangiography techniques during aneurysm and arteriovenous malformations (AVM) surgeries.

PATIENT AND METHODS

Fourtynine consecutive patients were operated between September 2015 and December 2022. Patients with ruptured/unruptured aneurysms or with AVMs presented with/without hemorrhage were included to the current study.

RESULTS

There were a total of 48 aneurysms and 11 AVMs in 49 patients in the current study. Na-Fl enables the surgeon to manipulate vessels and aneurysms real-time. ICG provides the ability to watch the videoangiography repeatedly and understand the angioarchitecture. The use of FLOW-800 module allows the surgeon to make concrete judgements about the flow dynamics of AVMs and therefore ICG videoangiography found useful in AVM surgery. Na-Fl has been found more useful for the evalution of the low caliber perforating arteries and anatomical features of the aneursym dome in aneurysm surgery.

CONCLUSION

The results of our series demonstrated the safety and efficacy of Na-Fl use in the surgery of aneurysms and AVMs. Both the ICG and Na-Fl videoangiographies are easy to perform and complimentary to each other. Combined use of these two mediums may provide better surgical results, considering the separate advantages and disadvantages of these both techniques.

Fluorescein videoangiography (FL-VAG) as a predictor of cerebral bypass patency

Background

The fluorescein videoangiography (FL-VAG) has become a valuable adjunct tool in vascular neurosurgery. This work describes using the FL-VAG during bypass surgery and proposes a classification method for evaluating surgical results.

Methods

We analyzed 26 patients with 50 cerebral bypasses from September 2018 to September 2022. We used a three grades classification method based on the pass of intravenous fluorescein through the anastomosis. Grade 1 represents the synchronous and total filling of the "T" shape ("green T″) formed by the donor and recipient vessel, Grade 2, the asynchronous filling of the anastomosis (incomplete/asynchronous "green T″), and Grade 3, a non-patent anastomosis (absence of "green T″).

Results

Of the 26 patients, 8 underwent one bypass, 14 underwent double bypass, 2 underwent three bypasses, and 2 underwent four bypasses in two different interventions. The type of bypass was end-to-side anastomosis in 47 (94%) cases, internal maxillary artery to middle cerebral artery bypass with a radial artery graft (IMax-MCA anastomosis) in 2 (4%), and PICA-VA transposition in one (2%). We made 24 (48%) bypasses on the right side and 26 (52%) on the left side. After the initial surgery, thirty-nine (78%) bypasses were considered as Grade 1, 5 (10%) as Grade 2, and 6 (12%) as Grade 3. After intraoperative bypass patency assessment (IBPA), 45 (90%) of the bypasses were considered Grade 1 and remained patent on CTA.

Conclusions

Using FL-VAG and a three-tier classification method is a reliable tool to predict bypass patency. It is safe, low-risk, and available worldwide.

Comparative Study of Intraoperative Fluorescein and Indocyanine Green Videoangiography for Ruptured Cerebral Aneurysms Clipping: A Single Centre Study of 30 Cases

Aim This study assesses the application of microscope integrated videoangiography techniques in aneurysm clipping surgery using Indocyanine Green and Fluorescein fluorophores and evaluates merits and demerits of each technique.

Materials and Methods Total 30 patients of cerebral aneurysmal clipping were included. Standard microsurgical procedures were done. After clipping, we administered a 25 mg bolus intravenous dose of indocyanine green with microscope focused through the INFRARED 800 camera module, followed by administration of 60 mg bolus intravenous dose of fluorescein with microscope focused through the yellow 560 module and images were assessed.

Results The average aneurysm size was 17 mm. In 12 patients (40%), FL-VA allowed better assessment of perforating arteries (seven cases) or distal branches (three cases) or both (two cases), when compared with ICG-VA. In one case of MCA (M1) aneurysm, ICG-VA showed no fluorescent signal in one of the distal trunks whereas FL-VA showed normal signal. In one case of ACOM aneurysm, perforators were missed on ICG-VA but were seen on FL-VA. FL-VA was able to identify inadequate aneurysm clipping in one case. In two patients, FL-VA provided the advantage of real-time manipulation of the vessels to expose the vessels and aneurysms of interest. Fluorescein detected all the perforators that were visible under white light (68/68) whereas ICG was able to detect 56 (82.35%) perforators (p-value< 0.05).

Conclusion Intraoperative ICG and Fluorescein videoangiography recognize inadequate occlusion of aneurysm, decreased flow in branches or perforators. When various study parameters were considered such as ability to assess small size perforators, branching vessels, adequacy of aneurysmal clipping, and useful information on repeat imaging, FL-VA was found superior to ICG-VA.

Enhance Safety in Aneurysm Surgery: Strategies for Prevention of Intraoperative Vascular Complications

Complications during surgery for intracranial aneurysms can be devastating. Notorious pitfalls include premature rupture, parent vessel occlusion, local cerebral injury and brain contusion, and incomplete neck obliteration. These unfavorable intraoperative events can result in major neurological deficits with permanent morbidity and even mortality. Herein, the author highlights the relevant surgical strategies used in his daily practice of aneurysm surgery (e.g., aneurysm clipping with adenosine-induced temporary cardiac arrest), application of which may help prevent vascular complications and enhance surgical safety through reduction of the associated risks, thus allowing improvement of postoperative outcomes. Overall, all described methods and techniques should be considered as small pieces in the complex puzzle of prevention of vascular complications during aneurysm surgery.

Intraoperative fluorescein video angiography in intracranial aneurysm surgery: single-center, observational cohort study

The aim of this study was to compare the incidence of postoperative, surgery-related complications in patients where fluorescein video angiography (FL-VA) was performed with those operated without intraoperative verification. This is an observational cohort study including 97 patients who were selected for microsurgical clipping due to intracranial aneurysm. First 52 patients enrolled in the study were operated prior to introduction of fluorescein fluorescence in our surgical workflow. These patients were considered as controls. The study group consisted of 45 consecutive patients operated with the use of fluorescein video angiography and by the same surgical team. Outcomes in both groups were compared using non-parametric test (Mann-Whitney U). Intraoperative fluorescein video angiography revealed aneurysm remnant or inadvertent vessel occlusion in 17.8% of patients. Following clip reposition, a repeated FL-VA was performed to confirm restoration of blood flow and/or complete aneurysm obliteration. Intraoperative findings were later confirmed using computed tomography angiography (CTA). None of the patients in our study group developed surgery-related complications; whereas in the control group, aneurysm remnant was discovered in 7.7%, brain ischemia in 9.6% and both of the latter in 5.8% of patients. Difference in treatment-related outcome was statistically significant (p < 0.05). Intraoperative fluorescein video angiography successfully identified aneurysm residual and adjacent artery occlusion leading to excellent outcome following clip reposition.

In Situ Side-to-Side Pericallosal-Pericallosal Artery and Callosomarginal-Callosomarginal Artery Bypasses for Complex Distal Anterior Cerebral Artery Aneurysms: A Technical Note

BACKGROUND

Despite surgical and endovascular technical improvements over the last decades, the treatment of complex aneurysms of the distal anterior cerebral artery (ACA) is very challenging for both vascular neurosurgeons and interventional neuroradiologists. Furthermore, the interpersonal anatomic variability requires, most of the time, a tailored planning.

OBJECTIVE

To describe a novel technique of bypasses in the territory of ACA to protect the brain territory distal to the aneurysm.

METHODS

A 53-yr-old male with a large complex fusiform aneurysm of the left distal A2 segment of the ACA, involving the origin of the callosomarginal and pericallosal arteries, was judged not suitable for a single procedure (endovascular or neurosurgical). Two side-to-side bypasses were performed in a single surgery to connect the pericallosal and callosomarginal arteries of both sides, distally to the aneurysm. Subsequently, an endovascular embolization of the aneurysm was achieved with coils.

RESULTS

The patency of the microanastomoses, performed in the anterior interhemispheric fissure, was positively evaluated intraoperatively with indocyanine green and fluorescein videoangiography. The aneurysm sac, together with proximal A2 segment, was completely occluded with platinum coils. At the last follow-up, computed tomography angiography confirmed the patency of both bypasses, without any sign of aneurysm recanalization. The patients never complained of any focal neurological deficits or worsening of clinical status.

CONCLUSION

We present an elegant and innovative solution to completely protect the distal ACA territory in cases of complex aneurysm involving the origin of both callosomarginal and pericallosal arteries.

The evolution of intracranial aneurysm treatment techniques and future directions

Treatment techniques and management guidelines for intracranial aneurysms (IAs) have been continually developing and this rapid development has altered treatment decision-making for clinicians. IAs are treated in one of two ways: surgical treatments such as microsurgical clipping with or without bypass techniques, and endovascular methods such as coiling, balloon- or stent-assisted coiling, or intravascular flow diversion and intrasaccular flow disruption. In certain cases, a single approach may be inadequate in completely resolving the IA and successful treatment requires a combination of microsurgical and endovascular techniques, such as in complex aneurysms. The treatment option should be considered based on factors such as age; past medical history; comorbidities; patient preference; aneurysm characteristics such as location, morphology, and size; and finally the operator’s experience. The purpose of this review is to provide practicing neurosurgeons with a summary of the techniques available, and to aid decision-making by highlighting ideal or less ideal cases for a given technique. Next, we illustrate the evolution of techniques to overcome the shortfalls of preceding techniques. At the outset, we emphasize that this decision-making process is dynamic and will be directed by current best scientific evidence, and future technological advances.

Intra-operative fluorescein videoangiography-related nephrotoxicity in intracranial aneurysm surgery: Single center, observational cohort study

OBJECTIVES

Intra-operative fluorescein video angiography (FL-VA) has been given increasing attention recently and several studies reported its high utility in neurovascular surgery. The aim of this study was to evaluate the safety of FL-VA in a prospective, single-center cohort of patients operated due to cerebral aneurysms.

PATIENTS AND METHODS

This is an observational cohort study including 150 patients operated due to intracranial aneurysms. The study group consisted of 70 consecutive patients operated with the use of fluorescein video angiography. Post-operative acute kidney injury (AKI) occurrence as well as systemic adverse reactions were reported and further compared with 80 matched controls where FL-VA was not used. Statistical analysis was performed using non-parametric tests (Fisher's exact test).

RESULTS

Post-operative AKI was observed in 17,1% of patients in the study group with only half presenting with acute functional impairment. All of these patients presented initially due to aneurysm rupture. Pre-existing renal dysfunction and hypertension occurred in 16,7% and 33,3%, respectively. No systemic complications following FL-VA were reported. When compared to matched controls, no statistically significant difference regarding AKI occurrence was observed between these two patient populations.

CONCLUSION

Intra-operative fluorescein video angiography proved to have a good safety profile in our cohort. The results of this study suggest that post-operative acute kidney injury observed in patients with subarachnoid hemorrhage is not related to fluorescein use.

Comprehensive review of surgical microscopes: technology development and medical applications

SIGNIFICANCE

Surgical microscopes provide adjustable magnification, bright illumination, and clear visualization of the surgical field and have been increasingly used in operating rooms. State-of-the-art surgical microscopes are integrated with various imaging modalities, such as optical coherence tomography (OCT), fluorescence imaging, and augmented reality (AR) for image-guided surgery.

AIM

This comprehensive review is based on the literature of over 500 papers that cover the technology development and applications of surgical microscopy over the past century. The aim of this review is threefold: (i) providing a comprehensive technical overview of surgical microscopes, (ii) providing critical references for microscope selection and system development, and (iii) providing an overview of various medical applications.

APPROACH

More than 500 references were collected and reviewed. A timeline of important milestones during the evolution of surgical microscope is provided in this study. An in-depth technical overview of the optical system, mechanical system, illumination, visualization, and integration with advanced imaging modalities is provided. Various medical applications of surgical microscopes in neurosurgery and spine surgery, ophthalmic surgery, ear-nose-throat (ENT) surgery, endodontics, and plastic and reconstructive surgery are described.

RESULTS

Surgical microscopy has been significantly advanced in the technical aspects of high-end optics, bright and shadow-free illumination, stable and flexible mechanical design, and versatile visualization. New imaging modalities, such as hyperspectral imaging, OCT, fluorescence imaging, photoacoustic microscopy, and laser speckle contrast imaging, are being integrated with surgical microscopes. Advanced visualization and AR are being added to surgical microscopes as new features that are changing clinical practices in the operating room.

CONCLUSIONS

The combination of new imaging technologies and surgical microscopy will enable surgeons to perform challenging procedures and improve surgical outcomes. With advanced visualization and improved ergonomics, the surgical microscope has become a powerful tool in neurosurgery, spinal, ENT, ophthalmic, plastic and reconstructive surgeries.

Multi-wavelength fluorescence imaging with a da Vinci Firefly-a technical look behind the scenes

The field of fluorescence-guided surgery builds on colored fluorescent tracers that have become available for different clinical applications. Combined use of complementary fluorescent emissions can allow visualization of different anatomical structures (e.g. tumor, lymphatics and nerves) in the same patient. With the aim to assess the requirements for multi-color fluorescence guidance under in vivo conditions, we thoroughly characterized two FDA-approved laparoscopic Firefly camera systems available on the da Vinci Si or da Vinci Xi surgical robot. In this process, we studied the cameras’ performance with respect to the photophysical properties of the FDA-approved dyes Fluorescein and ICG. Our findings indicate that multi-wavelength fluorescence imaging of Fluorescein and ICG is possible using clinical-grade fluorescence laparoscopes, but critical factors for success include the photophysical dye properties, imaging system performance and the amount of accumulated dye. When comparing the camera performance, the Xi system provided more effective excitation (adaptions in the light source) and higher detection sensitivity (chip-on-a-tip and/or enhanced image processing) for both Fluorescein and ICG. Both systems can readily be used for multi-wavelength fluorescence imaging of Fluorescein and ICG under clinically relevant conditions. With that, another step has been made towards the routine implementation of multi-wavelength image-guided surgery concepts.

Multi-Wavelength Fluorescence in Image-Guided Surgery, Clinical Feasibility and Future Perspectives

With the rise of fluorescence-guided surgery, it has become evident that different types of fluorescence signals can provide value in the surgical setting. Hereby a different range of targets have been pursued in a great variety of surgical indications. One of the future challenges lies in combining complementary fluorescent readouts during one and the same surgical procedure, so-called multi-wavelength fluorescence guidance. In this review we summarize the current clinical state-of-the-art in multi-wavelength fluorescence guidance, basic technical concepts, possible future extensions of existing clinical indications and impact that the technology can bring to clinical care.

Real-Time Overlapping of Indocyanine Green—Video Angiography With White Light Imaging for Vascular Neurosurgery: Technique, Implementation, and Clinical Experience

BACKGROUND

Fluorescent-guided techniques in vascular neurosurgery can be demonstrated via black and white indocyanine green videoangiography (ICG-VA). Multispectral imaging (MFL) is a new method, which overlaps fluorescence with the white light and provides a fluorescent white light augmented reality image to the surgeon.

OBJECTIVE

To investigate (a) whether MFL can enhance the visualization of the blood-flow with simultaneous visualization of the anatomic structures and (b) if MFL can ergonomically improve the microvascular surgical treatment compared to ICG-VA.

METHODS

A digital imaging of the blood flow after intravenous injection of ICG on 7 pigs was performed in real time under white light, standard fluorescence, and MFL. The blood flow was interrupted with a surgical clip, demonstrating the blockage of the blood flow. We prospectively included 30 patients with vascular deformities. The vasculature was visualized on the microscope's monitor and through the microscope's eyepiece.

RESULTS

In the animal experiment, the visualization of the anatomy and the blood flow under MFL produced high resolution images. The occlusion of blood vessels demonstrated sufficiently the blockage of tissue perfusion and its reperfusion after clip removal. During all 30 surgical cases, the MFL technique and the direct delivery of the pseudo-colored image through the eyepiece allowed for enhanced anatomic and dynamic data.

CONCLUSION

MFL was shown to be superior to the classic ICG-VA, delivering enhanced data and notably improving the workflow due to the simultaneous and precise white light visualization of the blood flow and the surrounding anatomic structures.

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.

Application of Fluorescein Fluorescence in Vascular Neurosurgery

Background: Fluorescein sodium (FNa) is a fluorescent drug with a long history of use for assessing retinal blood flow in ophthalmology; however, its application in vascular neurosurgery is only now gaining popularity. This review summarizes the current knowledge about using FNa videoangiography in vascular neurosurgery.

Methods: We performed a literature review on the usage of FNa for fluorescent videoangiography procedures in neurosurgery. We analyzed methods of injection, dosages of FNa, visualizing platforms, and interpretation of FNa videoangiography. We also reviewed practical applications of FNa videoangiography during various vascular neurosurgeries.

Results: FNa videoangiography can be performed with intraarterial (intracarotid) or intravenous dye injections. Both methods provide excellent resolution with enhanced fluorescence that shows intravascular blood flow on top of visible surrounding anatomy, and both allow simultaneous purposeful microsurgical manipulations. Although it is invasive, an intracarotid FNa injection results in faster contrast appearance and higher-intensity fluorescence and requires a lower dose per injection (reported range, 1–50 mg) compared with peripheral intravenous FNa injection (reported range, 75–2,000 mg or 1–1.5 mg/kg body weight). Four optical excitation/detection tools for FNa videoangiography have been successfully used: conventional xenon-light operating microscope with a special filter set, pencil-type light-emitting diode probe with a filter set, laser-illumination operating microscope, and an endoscope with a filter set. FNa videoangiography was reported to be feasible and useful in various clinical scenarios, such as examining the feeders and drainers in arteriovenous malformation surgery, checking the patency of a microvascular anastomosis, and assessing blood flow during aneurysm clipping. FNa videoangiography can be repeated during the same procedure and used along with indocyanine green (ICG) videoangiography.

Conclusions: Compared with ICG videoangiography, FNa videoangiography has the advantages of enabling real-time inspection and better visualization at deep locations; however, thick vessel walls limit visualization of FNa in larger vessels. FNa videoangiography is a useful tool in multiple neurovascular scenarios and merits further studies to establish its clinical value.

Fluorescein Application in Cranial and Spinal Tumors Enhancing at Preoperative MRI and Operated With a Dedicated Filter on the Surgical Microscope: Preliminary Results in 279 Patients Enrolled in the FLUOCERTUM Prospective Study

Objective: Sodium fluorescein, a green, water soluble dye, is used as neurosurgical fluorescent tracer thanks to its property to accumulate in cerebral regions of blood-brain barrier (BBB) disruption. The authors report the preliminary results of a prospective observational study regarding the use of fluorescein-guided technique for the resection of suspected malignant neoplasms of the central nervous system (CNS), contrast enhancing at preoperative magnetic resonance imaging (MRI), using a dedicated filter on the surgical microscope. Methods: In March 2016 the authors started a prospective, observational trial to evaluate intraoperative fluorescence's characteristics of CNS tumors, the percentage of extent of resection thanks to fluorescein aid and side effects related to fluorescein administration. This report is based on a preliminary analysis of the results of first 279 enrolled patients. Fluorescein was intravenously injected after intubation or immediately at the entrance in the operating room for awake procedures; the tumor was removed using a dedicated filter on the surgical microscope in an inside-out fashion until all fluorescent tissue was removed, as considered feasible by the surgeon. Results: The 279 patients finally enrolled in the trial, both firstly diagnosed and recurrent, were categorized according to WHO pathological classification and there were 212 neuroepithelial tumors, 25 brain metastases, 10 cerebral lymphomas, 7 hemangioblastomas, or hemangioendotheliomas and 25 other tumors and conditions. No adverse reaction related to the administration of fluorescein or to the combined use of fluorescein with other fluorophores was registered. Fluorescein accumulated in cerebral regions where the BBB was damaged, representing a significant surgical aid in most of the CNS tumors with contrast enhancement. In cases of complete removal of all fluorescent tissue, as intraoperatively judged by the surgeon, postoperative MRI revealed a gross total resection in 181/198 patients (91.4%). Conclusions: Based on these preliminary results, fluorescein-guided surgery with a dedicated filter on the microscope is a safe and effective technique to improve visualization and resection of different CNS tumors and conditions, based on BBB alteration.

Vasa Vasorum Densities in Human Carotid Atherosclerosis Is Associated with Plaque Development and Vulnerability

Objective

The extensive vasa vasorum network functions as a conduit for the entry of inflammatory cells or factors that promote the progression of angiogenesis and plaque formation. Therefore, we investigated the correlation between the carotid vasa vasorum activities and carotid plaque vulnerability using indocyanine green video angiography (ICG-VA) during carotid endarterectomy (CEA).

Methods

Sixty-nine patients who underwent CEA were enrolled prospectively from September 2015 to December 2017. During CEA, a bolus of ICG was injected intravenously before and after resecting the atheroma. Additionally, we performed immunohistochemistry using CD68 (a surface marker of macrophages), CD117 (a surface marker of mast cells), and CD4 and CD8 (surface markers of T-cells) antibodies to analyze the resected plaque specimens.

Results

The density of active vasa vasorum was observed in all patients using ICG-VA. The vasa vasorum externa (VVE) and interna (VVI) were seen in 11 (16%) and 57 patients (82.6%), respectively. Macroscopically, the VVE-type patterns were strongly associated with preoperative angiographic instability (81.8%, p=0.005) and carotid plaque vulnerability (90.9%, p=0.017). In contrast, the VVI-type patterns were weakly associated with angiographic instability (31.6%) and plaque vulnerability (49.1%). CD68-stained macrophages and CD117-stained mast cells were observed more frequently in unstable plaques than in stable plaques (p<0.0001, p=0.002, respectively).

Conclusion

The early appearance of VVE, along with the presence of many microvessel channels that provided nutrients to the developing and expanding atheroma during ICG-VA, was strongly associated with unstable carotid plaques. The degree of infiltration of macrophages and mast cells is possibly related to the formation of unstable plaques.

Quantitative Comparison of the Intraoperative Utility of Indocyanine Green and Fluorescein Videoangiographies in Cerebrovascular Surgery

BACKGROUND

A quantitative analysis comparing indocyanine green videoangiography (ICG-VAG) and fluorescein videoangiography (FL-VAG) in cerebrovascular surgery has not been reported so far.

OBJECTIVE

To clear the differences of characteristics of ICG-VAG and FL-VAG by quantitative assessment.

METHODS

We prospectively analyzed results from 23 patients (3 males; mean age at surgery: 60.9 years, range: 14-75 years) at our hospital from August 2014 to July 2015. Eighteen patients had cerebral aneurysms for clipping, and 5 had intracranial arterial stenosis for superficial temporal artery (STA)-middle cerebral artery bypass. We imported data from the operative image data, converted by Audio Video Interleave to Aquacosmos as picture fluorescence intensity-analyzing software. Regions of interest were set at the parent artery, dome of aneurysms, and perforating artery in cases of clipping of aneurysms, and setting at 3 points in STA, in case of bypass. The transition of fluorescence intensity at each region of interest was calculated and plotted using Aquacosmos.

RESULTS

Thick-walled artery, such as parent artery ( P = .0017) and STA ( P = .0182), was more significantly visualized by ICG-VAG than FL-VAG, whereas the perforating artery, especially in deep surgical fields, such as anterior communicating artery, internal carotid artery, and basilar artery, was better visualized by FL-VAG than ICG-VAG ( P < .0001).

CONCLUSION

In this quantitative analysis of fluorescence study, ICG-VAG showed greater efficacy than FL-VAG in visualizing relatively thick arteries, such as parent artery and STA. However, FL-VAG has greater efficacy than ICG-VAG in visualizing perforating artery, especially in deep surgical fields with characteristic vessel walls.

Indocyanine Green Videoangiography for Surgery of a Ruptured Dissecting Aneurysm in the Precommunicating Anterior Cerebral Artery: A Technical Case Report

BACKGROUND AND IMPORTANCE

Indocyanine green videoangiography (ICG-VA) is an important intraoperative adjunct for saccular aneurysm surgery, but its efficacy in surgery for dissecting aneurysms has rarely been reported. The authors describe the usefulness of preclipping ICG-VA in a rare case of a ruptured dissecting aneurysm located at the precommunicating (A1) segment of the anterior cerebral artery.

CLINICAL PRESENTATION

A 52-year-old woman, with no history of connective tissue diseases or vascular disorders, presented with sudden headache and convulsion. The CT scan showed that the patient had subarachnoid hemorrhage. Angiography showed a dissecting aneurysm in the left A1 segment of the anterior cerebral artery. Thus, the patient underwent trapping of the dissecting aneurysm. ICG-VA was used as an intraoperative adjunct before and after clipping. The preclipping ICG-VA showed the heterogeneously bright dissecting aneurysm and branching arteries even in the presence of hematoma.

CONCLUSION

Preclipping ICG-VA may enhance the advantage of direct surgery for dissecting aneurysm by allowing visualization of the extent of the dissected vascular wall and the related branching arteries. ICG-VA can be an indispensable adjunct to minimize the compromise from the surgical treatment for intracranial dissecting aneurysms.

Universal fluorescence module for intraoperative fluorescein angiography-a technical report

BACKGROUND

Even in specialized centers, suboptimal aneurysm clipping can be as high as 12%. Intraoperative fluorescence angiography with indocyanine green and, more recently, fluorescein sodium have been shown to be a good method for intraoperative flow assessment. However, the cost with the apparatus it entails limits its widespread use. We have developed a low-cost universal fluorescence module (FM) designed to visualize fluorescein and perform intraoperative angiography. The purpose of this paper is to describe this device as well as to present our early experience with its use in the treatment of cerebral aneurysms.

METHOD

A FM was designed and built using a cyan-blue narrow bandpass (460 to 490 nm) excitation filter and a yellow-orange longpass (blocking wavelengths under 520 nm) barrier filter mounted on a 3D-printed holding tray in a specific disposition to perfectly match the light source and the objective lens of the surgical microscope. It allowed switching from white light to fluorescence mode in a simple and sterile fashion. Its perfect attachment to the microscope was possible by reusing the lens fittings extracted from used original drape sets that would otherwise be discarded. Four patients underwent aneurysm clipping using the FM at two institutions from April to September 2018.

RESULTS

A bright green fluorescence against a dark background was observed after intravenous bolus of fluorescein. Blood vessels became obviously distinct from non-contrast-filled structures such as clipped aneurysms and the brain. Vascular anatomy could be appreciated without any distortion, including perforating arteries.

CONCLUSIONS

Intraoperative fluorescence angiography was successfully performed with the use of this universal FM after intravenous injection of fluorescein sodium. This simple and low-cost device may be useful in resource-limited centers, where other sorts of intraoperative angiography are not available.

In vivo demonstration of blood-brain barrier impairment in Moyamoya disease

BACKGROUND

Moyamoya disease (MMD) is a cerebrovascular disorder characterized by fragile vascular system. Previous studies suggested that the blood-brain barrier (BBB) destabilizing cytokine angiopoietin-2 plays a critical role in increasing vascular plasticity and endothelial disintegration in MMD. The aim of this study was to assess cerebrovascular integrity in vivo in patients affected by MMD.

METHODS

We retrospectively analyzed 11 patients that underwent bypass for MMD (MMD group), 11 patients that underwent bypass for atherosclerotic cerebrovascular disease (ACVD-control group I), and 5 patients that underwent clipping for unruptured aneurysms (non-ischemic-control group II). Sodium fluorescein (NaFL) extravasation was evaluated during videoangiography when checking for bypass patency. A grading system (0, +, ++, +++) was used to define the extent of extravasation. Frequency and intensity of leakage was compared among different groups.

RESULTS

NaFL extravasation appeared in 10/11 (91%) patients with MMD and in 8/11 (73%) patients with ACVD during bypass procedures. Extravasation was observed in none of the patients undergoing clipping for unruptured aneurysms. Although both chronic ischemic patient groups showed a comparably high incidence of NaFL extravasation, the MMD group was characterized by a much greater intensity of NaFL extravasation (grade +++ in 82%) than the ACVD group (grade +++ in 27%, p < 0.05).

CONCLUSIONS

We demonstrate blood-brain barrier impairment in MMD patients for the first time in vivo. This may be due to mechanisms intrinsic to the unique pathology of MMD, probably explaining the higher association with hemorrhage and post-operative hyperperfusion.

Intraoperative Measurement of Arterial Blood Flow in Aneurysm Surgery

Intraoperative flowmetry (IF) has been recently introduced during cerebral aneurysm surgery in order to obtain a safer surgical exclusion of the aneurysm. This study evaluates the usefulness of IF during surgery for cerebral aneurysms and compares the results obtained in the joined surgical series of Verona and Padua to the more recent results obtained at the neurosurgical department of Verona.In the first surgical series, between 2001 and 2010, a total of 312 patients were submitted to IF during surgery for cerebral aneurysm at the neurosurgical departments of Verona and Padua: 162 patients presented with subarachnoid hemorrhage (SAH) whereas 150 patients harbored unruptured aneurysms. In the second series, between 2011 and 2016, 112 patients were submitted to IF during surgery for cerebral aneurysm at the neurosurgical department of Verona; 24 patients were admitted for SAH, whereas 88 patients were operated on for unruptured aneurysms.Comparison of the baseline values in the two surgical series and the baseline values between unruptured and ruptured aneurysms showed no statistical differences between the two clinical series. Analysis of flowmetry measurements showed three types of loco-regional flow derangements: hyperemia after temporary arterial occlusion, redistribution of flow in efferent vessels after clipping, and low flow in patients with SAH-related vasospasm.IF provides real-time data about flow derangements caused by surgical clipping of cerebral aneurysm, thus enabling the surgeon to obtain a safer exclusion; furthermore, it permits the evaluation of other effects of clipping on the loco-regional blood flow. It is suggested that-in contribution with intraoperative neurophysiological monitoring-IF may now constitute the most reliable tool for increasing safety in aneurysm surgery.

Laboratory Evaluation of a Robotic Operative Microscope - Visualization Platform for Neurosurgery

Background We assessed a new robotic visualization platform with novel user-control features and compared its performance to the previous model of operative microscope. Methods In a neurosurgery research laboratory, we performed anatomical dissections and assessed robotic, exoscopic, endoscopic, fluorescence functionality. Usability and functionality were tested in the operating room over 1 year. Results The robotic microscope showed higher sensitivity for fluorescein sodium, higher detail in non-fluorescent background, and recorded/presented pictures with color quality similar to observation through the oculars. PpIX visualization was comparable to the previous microscope. Near-infrared indocyanine green imaging 3-step replay allowed for more convenient accurate assessment of blood flow. Point lock and pivot point functions were used in dissections to create 3D virtual reality microsurgical anatomy demonstrations. Pivot point control was particularly useful in deep surgical corridors with dynamic retraction. 3D exoscopic function was successfully used in brain tumor and spine cases. Endoscopic assistance was used for around-the-corner views in minimally invasive approaches. We present illustrative cases highlighting utility and new ways to control the operative microscope. Conclusion Improvements of the robotic visualization platform include intraoperative fluorescence visualization using FNa, integrated micro-inspection tool, improved ocular imaging clarity, and exoscopic mode. New robotic movements positively assist the surgeon and provide improved ergonomics and a greater level of intraoperative comfort, with the potential to increase the viewing quality. New operational modes also allow significant impact for anatomy instruction. With the increasing number and complexity of functions, surgeons should receive additional training in order to avail themselves of the advantages of the numerous novel features.

Fluorescent tracers in neurosurgical procedures: an European survey

BACKGROUND

In recent years several techniques have been proposed with the aim of improving tumors visualization and extent of resection and, among them, the use of photosensitive dyes is gaining great interest. Regarding the application of the two most used dyes, 5-aminolevulinic acid (5-ALA) and sodium fluorescein (SF), there is still a lack of shared and established protocols among different centers. The main objective of the present study was to evaluate the current practice of fluorescence-guided techniques in neuro-oncological surgery in Europe.

METHODS

An online questionnaire consisting of 33 questions was completed by 136 European Association of Neurosurgical Societies neurosurgeons. Responses were entered into a database and subsequently analyzed.

RESULTS

Data were analyzed from 136 out of 1476 active European neurosurgeons which had been contacted, with a 9,2% response rate. Based on the data from the questionnaire, Germany was the most responsive country (15% of the total respondents) and the main indication for 5-ALA and SF utilization were high-grade gliomas. 5-ALA was mainly used as defined in Gliolan® datasheet, while SF as off-label technique with a 5 mg/kg dose of injection at the end of patient intubation. Both the dyes were mainly used in adult population, more frequently by neurosurgeons with less-than 20 cases per year expertise. Mean price per patient were 817,6 € and 7,7 € for 5-ALA and SF, respectively.

CONCLUSIONS

5-ALA acid is still the preferred and more established fluorescent dye used during high-grade gliomas resection, with SF as a gaining-attention, really cheaper and more ductile alternative.

Fluorescein videoangiography during extracranial-to-intracranial bypass surgery: preliminary results

BACKGROUND

Over the last years, intraoperative use of fluorescein is gaining ground in the field of neurosurgery, due to development of a microscope-integrated YELLOW 560 module, with reported experiences in brain malignancies, aneurysms, and arteriovenous malformation surgery. The aim of this study is to determine the feasibility and value of fluorescein videoangiography during bypass procedures.

METHODS

The authors enrolled 11 patients who underwent extracranial-to-intracranial bypass for moyamoya disease, atherosclerotic steno-occlusive cerebrovascular disease, and flow replacement during a giant middle cerebral artery (MCA) aneurysm treatment. Patients underwent fluorescein videoangiography using microscope-integrated fluorescence module.

RESULTS

In all 11 cases, good bypass patency was intraoperatively demonstrated through fluorescein videoangiography and confirmed by post-operative digital subtraction angiography or computed tomographic angiography. The technique seems to be less sensible than standard indocyanine green videoangiography in terms of flow velocity assessment during first pass and does not benefit from a dedicated software to perform hemodynamic parameter analysis (i.e., FLOW 800). Fluorescein videoangiography was able to show a higher number of vessels than indocyanine green videoangiography, providing an extremely well-defined view of cortical vascular network, also in deeper cortical areas. In case of deep-seated anastomosis, it allowed real-time manipulation of neurovascular structures, making it possible a safe analysis of vessels in deep surgical field during videoangiography observation.

CONCLUSIONS

Fluorescein videoangiography is a cost-effective, easy-to-use, fast and safe intraoperative tool and is useful to assess graft patency and extent of cortical vascular network also in deeper cortical areas. In case of deep-seated anastomosis, it provides the great advantage of performing real-time manipulation of neurovascular structures during videoangiography observation. It could represent a valuable complementary or alternative technique to assess intraoperative bypass function.

Indocyanine Green Videoangiography in Aneurysm Surgery: Systematic Review and Meta-Analysis

BACKGROUND

Although digital subtraction angiography (DSA) may be considered the gold standard for intraoperative vascular imaging, many neurosurgical centers rely only on indocyanine green videoangiography (ICG-VA) for the evaluation of clipping accuracy. Many studies have compared the results of ICG-VA with those of intraoperative DSA; however, a systematic review summarizing these results is still lacking.

OBJECTIVE

To analyze the literature in order to evaluate ICG-VA accuracy in the identification of aneurysm remnants and vessel stenosis after aneurysm clipping.

METHODS

We performed a systematic literature review of ICG-VA accuracy during aneurysm clipping as compared to microscopic visual observation (primary endpoint 1) and DSA (primary endpoint 2). Quality of studies was assessed with the QUADAS-2 tool. Meta-analysis was performed using a random effects model.

RESULTS

The initial PubMed search resulted in 2871 records from January 2003 to April 2016; of these, 20 articles were eligible for primary endpoint 1 and 11 for primary endpoint 2. The rate of mis-clippings that eluded microscopic visual observation and were identified at ICG-VA was 6.1% (95% CI: 4.2-8.2), and the rate of mis-clippings that eluded ICG-VA and were identified at DSA was 4.5% (95% CI: 1.8-8.3).

CONCLUSION

Because a proportion of mis-clippings cannot be identified with ICG-VA, this technique should still be considered complementary rather than a replacement to DSA during aneurysm surgery. Incorporating other intraoperative tools, such as flowmetry or electrophysiological monitoring, can obviate the need for intraoperative DSA for the identification of vessel stenosis. Nevertheless, DSA likely remains the best tool for the detection of aneurysm remnants.

Efficacy of Endoscopic Fluorescein Video Angiography in Aneurysm Surgery—Novel and Innovative Assessment of Vascular Blood Flow in the Dead Angles of the Microscope

BACKGROUND: In aneurysm surgery, assessment of the blood flow around the aneurysm is crucial. Recently, intraoperative fluorescence video angiography has been widely adopted for this purpose. However, the observation field of this procedure is limited to the microscopic view, and it is difficult to visualize blood flow obscured by the skull base anatomy, parent arteries, and aneurysm.

OBJECTIVE: To demonstrate the efficacy of a new small-caliber endoscopic fluorescence video angiography system employing sodium fluorescein in aneurysm surgery for the first time.

METHODS: Eighteen patients with 18 cerebral aneurysms were enrolled in this study. Both microscopic fluorescence angiography and endoscopic fluorescein video angiography were performed before and after clip placement.

RESULTS: Endoscopic fluorescein video angiography provided bright fluorescence imaging even with a 2.7-mm-diameter endoscope and clearly revealed blood flow within the vessels in the dead angle areas of the microscope in all 18 aneurysms. Consequently, it revealed information about aneurysmal occlusion and perforator patency in 15 aneurysms (83.3%) that was not obtainable with microscopic fluorescence video angiography. Furthermore, only endoscopic video angiography detected the incomplete clipping in 2 aneurysms and the occlusion of the perforating branches in 3 aneurysms, which led to the reapplication of clips in 2 aneurysms.

CONCLUSION: The innovative endoscopic fluorescein video angiography system we developed features a small-caliber endoscope and bright fluorescence images. Because it reveals blood flow in the dead angle areas of the microscope, this novel system could contribute to the safety and long-term effectiveness of aneurysm surgery even in a narrow operative field.

The Fluoropen: a simple low-cost device to detect intraoperative fluorescein fluorescence in stereotactic needle biopsy of brain tumors

BACKGROUND

The use of fluorescein fluorescence-guided stereotactic needle biopsy has been shown to improve diagnostic accuracy and to expedite operative procedure in the stereotactic needle biopsy of high-grade gliomas. We developed a device (Fluoropen) for detecting fluorescence in brain tumor tissues obtained by fluorescein fluorescence-guided stereotactic needle biopsy.

METHODS

The Fluoropen is a device consisting of a light source fitted with color filters to create the required emission and visualization wavelengths. The proof-of-concept study consisted of four consecutive patients who underwent fluorescein fluorescence-guided frameless stereotactic biopsy of brain tumor. Each sample was examined for the presence of fluorescence using the Fluoropen and compared with a microscope with fluorescence visualization capability.

RESULTS

A total of six samples were obtained from four stereotactic needle biopsy procedures. Four out of five samples (80%) taken from the contrast-enhancing part of the tumors were shown to be fluorescent under the microscope fitted with fluorescence module and the Fluoropen. One non-contrast enhancing lesion was non-fluorescent using both the microscope fitted with fluorescence module and the Fluoropen. The Fluoropen was shown to have 100% concordance with the microscope fitted with fluorescence module.

CONCLUSIONS

The Fluoropen is a low-cost and simple standalone device for the detection of fluorescein fluorescence that can expedite stereotactic needle biopsy by providing instant confirmation of the diagnostic sample and therefore avoid the need for an intraoperative frozen section. In patients with non-contrast enhancing tumors and those who were pre-treated with dexamethasone prior to surgery, fluorescein fluorescence-guided stereotactic needle biopsy will need to be used with caution.

Dual-Image Videoangiography During Intracranial Microvascular Surgery

OBJECTIVE

Indocyanine green videoangiography (ICG-VA) is a valuable tool to assess vessel and aneurysm patency during neurovascular surgical procedures. However, ICG-VA highlights vascular structures, which appear white over a black background. Anatomic relationships are sometimes difficult to understand at first glance. Dual-image videoangiography (DIVA) enables simultaneous visualization of light and near-infrared fluorescence images of ICG-VA.

METHODS

The DIVA system was mounted on an OPMI Pentero Flow 800 intraoperative microscope. DIVA was used during microsurgical procedures on 5 patients who were operated for aneurysm clipping and superficial temporal artery-middle cerebral artery bypass.

RESULTS

DIVA provides real-time simultaneous visualization of aneurysm and vessels and surrounding structures including brain, nerves, and surgical clips. Although visual contrast between vessels and background is higher with standard black-and-white imaging, DIVA makes it easier to understand anatomic relationships between intracranial structures. DIVA also provides better vision of the depth of field.

CONCLUSIONS

DIVA has the potential to become a widely used intraoperative tool to check patency of intracranial vessels. It should be considered as an adjunct to standard ICG-VA for better understanding of vascular anatomy in relation to surrounding structures and can have an impact on decision making during surgery.

Optical technologies for intraoperative neurosurgical guidance

Biomedical optics is a broadly interdisciplinary field at the interface of optical engineering, biophysics, computer science, medicine, biology, and chemistry, helping us understand light-tissue interactions to create applications with diagnostic and therapeutic value in medicine. Implementation of biomedical optics tools and principles has had a notable scientific and clinical resurgence in recent years in the neurosurgical community. This is in great part due to work in fluorescence-guided surgery of brain tumors leading to reports of significant improvement in maximizing the rates of gross-total resection. Multiple additional optical technologies have been implemented clinically, including diffuse reflectance spectroscopy and imaging, optical coherence tomography, Raman spectroscopy and imaging, and advanced quantitative methods, including quantitative fluorescence and lifetime imaging. Here we present a clinically relevant and technologically informed overview and discussion of some of the major clinical implementations of optical technologies as intraoperative guidance tools in neurosurgery.

Feasibility of simultaneous sodium fluorescein and indocyanine green injection in neurosurgical procedures

OBJECTIVE

The objective of this study is to assess the feasibility of simultaneous Sodium Fluorescein (SF) and Indocyanine Green (ICG) injection during neurosurgical procedures.

PATIENTS AND METHODS

Three patients harboring a high-grade glioma (HGG) were retrospectively identified in the surgical database of the Neurosurgical Unit 2 at the Foundation IRCCS Istituto Neurologico C. Besta in Milan, by having received intraoperatively both SF for tumor resection and ICG for vasculature angiographic studies in the same surgical procedure. We identified 2 males and 1 female (age range 25-60). Lesions were located in the left temporo-polar area and hippocampus (1 case), right superior frontal gyrus (1 case), left supplementary motor area (1 case). All the three lesions showed Magnetic Resonance Imaging (MRI) characteristics of HGG and, for this reason, in all patients a fluorescein-guided tumor removal was proposed. In the same surgical procedure ICG videoangiography was considered necessary in order to study arterial and venous vasculature, given by the strict relation of the tumor with an unexpected Posterior Communicating Artery (PComA) aneurysm in one case and with cortical drainage veins complexes in the other two cases. In all cases a microscope equipped with both YELLOW560 and IR800 integrated filters (Pentero 900, Carl Zeiss, Oberkorchen, Germany) was used. Fluorescein was i.v. injected at a dose of 5mg/kg immediately after patient intubation. ICG was i.v. injected in bolus on demand of the operating surgeon at a dose of 12.5mg.

RESULTS

No side-effects related to simultaneous injection of SF and ICG were identified. In all three cases, the use of SF allowed to better visualize the tumor areas during surgical removal, thus leading to a radical resection until no macroscopic appearance of residual tumor mass and no fluorescence was visible in the surgical cavity. ICG videoangiography confirmed the patency of branches of internal carotid artery after clipping of an unexpected small PComA aneurysm found intraoperatively during tumor removal in one case, while in patient 2 and 3 it allowed to evaluate patency and study flow pattern in cortical drainage veins that were intimately related to the tumors and the way of the surgical approach. Postoperative MRI showed a Gross Total Resection of the tumors in all cases.

CONCLUSIONS

This study showed for the first time the feasibility of intravenous SF injection and ICG videoangiography in the same surgical procedure. The presence of different fluorescence filters on the same surgical microscope allows the surgeon to recognize and safely resect the tumor and simultaneously evaluate local brain vascularization.

Intraoperative indocyanine green videoangiography to guide decision making regarding need for vessel bypass: A case report and technical note

Background:

Indocyanine green (ICG) videoangiography is an intraoperative technique recently used in vascular neurosurgery to assess the presence or absence of blood flow during critical times of a procedure. These include, but are not limited to, detecting whether daughter branches or perforators are patent after placing a vascular clip or determining whether an aneurysm has been completely isolated from the cerebral circulation after clipping. We present a case of a less-commonly reported application of ICG videoangiography involving the selection of a vessel to act as the bypass recipient once the need is identified during the surgical treatment of a complex intracranial aneurysm.

Case Description:

A 51-year-old male presented with a ruptured dissecting superior cerebellar artery (SCA) aneurysm that had two branches arising from the dome. Due to the difficult morphology of this aneurysm, a superficial temporal artery to SCA bypass was planned. We used ICG videoangiography to identify the branch that had insufficient retrograde flow via collateral circulation, to which the bypass was performed, followed by the isolation of the aneurysm from the cerebral circulation using permanent surgical clips.

Conclusion:

Our case represents a possible use of ICG videoangiography during the operative treatment of a difficult aneurysm. Our patient suffered no infarcts postoperatively. In the correct clinical context, this method represents a possible treatment option for complex aneurysms requiring a bypass.