Fluorescein-Guided Resection of Intramedullary Spinal Cord Tumors: Results from a Preliminary, Multicentric, Retrospective Study

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.

A light in the darkness: sodium fluorescein-assisted peripheral nerve sheath tumors resection - a comprehensive systematic review and single-arm meta-analysis

The treatment for peripheral nerve sheath tumors (PNSTs) is based on surgical excision and the primary goal is to improve symptoms whilst preserving neurological function. In order to improve this technique, surgeons may use sodium fluorescein (SF) to help visualize the neoplasm and, consequently, facilitate its removal. Aiming to assess the efficacy of this emerging surgical strategy, we conducted a systematic review and single-arm meta-analysis. We conducted a systematic search on the PubMed, Embase, and Web of Science databases, following the PRISMA guidelines. Studies without outcomes of interest, case series with less than four patients, letters, comments, technical notes, editorials, reviews, and basic research papers were excluded. The outcomes considered for this study were: the number of tumors that achieved total resection, subtotal resection, or near total resection, the approach/technique utilized by the surgeon, SF-related complications, and total complications. Five studies, with a total of 175 individuals, were included in our survey. Notably, 70% of the neoplasms presented by the patients were schwannomas. Considering extracranial lesions, we found a proportion of 96% (95% CI: 88 - 100%) in total resection, 0% (95% CI: 0-1%) in near total resection, and 4% (95% CI: 0-12%) in subtotal resection, all linked to an amount of 185 analyzed PNSTs. Furthermore, a proportion of 1% (95% CI: 0 - 2%) in SF-related complications was spotted among 183 patients. Finally, total complications analysis accounted for 11% (95% CI: 0 - 25%) among 183 individuals. We concluded that SF-assisted resection of PNSTs is a suitable and relatively safe technique, linked to minimum complications, of which the majority was not associated with the chemical compound itself. Future research is necessary to increase the number of patients available in the current literature and, therefore, enhance future analyses.

Fluorescence-guided resection of intradural spinal tumors: a systematic review and meta-analysis

Intradural spinal tumors present significant challenges due to involvement of critical motor and sensory tracts. Achieving maximal resection while preserving functional tissue is therefore crucial. Fluorescence-guided surgery aims to improve resection accuracy and is well studied for brain tumors, but its efficacy has not been fully assessed for spinal tumors. This meta-analysis aims to delineate the efficacy of fluorescence guidance in intradural spinal tumor resection. The authors performed a systematic review in four databases. We included studies that have utilized fluorescence agents, 5-aminolevulinic acid (5-ALA) or sodium fluorescein, for the resection of intradural spinal tumors. A meta-analysis was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 12 studies involving 552 patients undergoing fluorescence-guided intradural spinal tumor resection were included. Meningiomas demonstrated a 98% fluorescence rate and were associated with a homogenous florescence pattern; however, astrocytomas had variable fluorescence rate with pooled proportion of 70%. There was no significant difference in gross total resection (GTR) rates between fluorescein and 5-ALA (94% vs 84%, p = .22). Pre-operative contrast enhancement was significantly associated with intraoperative fluorescence with fluorescein. Intramedullary tumors with positive intraoperative fluorescence were significantly associated with higher GTR rates (96% vs 73%, p = .03). Utilizing fluorescence guidance during intradural spinal tumor resection holds promise of improving intraoperative visualization for specific intradural spinal tumors. Meningiomas and ependymomas have the highest fluorescence rates especially with sodium fluorescein; on the other hand, astrocytomas have variable fluorescence rates with no superiority of either agent. Positive fluorescence of intramedullary tumors is associated with a higher degree of resection.

Assessing the role of sodium fluorescein in peripheral nerve sheath tumors and mimicking lesions surgery: An update after 142 cases

Objective

Peripheral nerve sheath tumors (PNST) include mainly schwannomas and neurofibromas. Surgical resection represents the mainstay of treatment but due to their pathogenesis, distinguishing between intact functional nerve and the fibers from whence the PNST arose may not always be easy to perform, constituting the most relevant risk factor in determining a worsening in neurological condition. The introduction of intraoperative tools to better visualize these tumors could help achieve a gross-total resection. In this study, we analyzed the effect of sodium fluorescein (SF) on the visualization and resection of a large cohort of PNST.

Methods

Between September 2018 and December 2021, 142 consecutive patients harboring a suspected PNST underwent fluorescein-guided surgery at the Department of Neurosurgery of the Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy. All patients presented with a different degree of contrast enhancement at preoperative MRI. SF was intravenously injected after intubation at 1 mg/kg. Intraoperative fluorescein characteristics and postoperative neurological and radiological outcomes were collected, analyzed, and retrospectively compared with a historical series.

Results

142 patients were included (42 syndromic and 100 sporadic); schwannoma was the predominant histology, followed by neurofibroma (17 neurofibroma e 12 plexiform neurofibroma) and MPNST. Bright fluorescence was present in all cases of schwannomas and neurofibromas, although with a less homogeneous pattern, whereas it was significantly less evident for malignant PNST; perineurioma and hybrid nerve sheath tumors were characterized by a faint fluorescence enhancement. The surgical resection rate in the general population and even among the subgroups was about 66.7%; from the comparative analysis, we found a consistently higher rate of complete tumor removal in plexiform neurofibromas, 66% in the "fluorescent" group vs 44% in the "historical" group (p-value < 0.05). The rate of complications and mean surgical time were superimposable among the two populations.

Conclusions

SF is a valuable method for safe fluorescence-guided PNST and mimicking lesions resection. Our data showed a positive effect of fluorescein-guided surgery in increasing the rate of surgical resection of plexiform neurofibromas, suggesting a possible role in improving the functional and oncological outcome of these lesions.

First Clinical Report of the Intraoperative Macro- and Micro-Photodiagnosis and Photodynamic Therapy Using Talaporfin Sodium for a Patient with Disseminated Lumbar Medulloblastoma

Photodiagnosis (PD) and photodynamic therapy (PDT) using the second-generation photosensitizer talaporfin sodium together with an exciting laser for primary intracranial malignant tumors is well recognized in Japan, and many medical institutions are introducing this new therapeutic option. In particular, intraoperative PDT using talaporfin sodium for infiltrating tumor cells in the cavity walls after the resection of malignant glioma is now covered by health insurance after receiving governmental approvement, and this method has been recommended in therapeutic guidelines for primary malignant brain tumors in Japan. On the other hand, experimental and clinical studies on the development of novel therapeutic strategies for malignant spinal cord tumors have not been reported to date, although their histological features are almost identical to those of intracranial malignant tumors. Therefore, the clinical outcomes of malignant spinal cord tumors have been less favorable than those of malignant brain tumors. In this report, we performed the PD and PDT using talaporfin sodium on a patient with a metastatic lumbar lesion that was detected on magnetic resonance image (MRI) 50 months after the resection of cerebellar medulloblastoma who presented with lumbago and sciatica. We were able to detect the target lesion in the conus medullaris using a surgical microscope, and detected the disseminated medulloblastoma cells floating in the cerebrospinal fluid using a compact fluorescence microscope. Furthermore, we performed PDT to the resected lumbar lesion with the adjuvant platinum-based chemotherapy, and the patient survived a meaningful life for more than 2 years after the lumbar surgery. This report describes the first case of a human patient in whom the efficacy of PD and PDT was demonstrated for a malignant spinal cord tumor.

Hemangioblastomas and Other Vascular Origating Tumors of Brain or Spinal Cord

Hemangioblastomas (HBs) are highly vascularized, slow-growing, rare benign tumors (WHO grade I). They account for about 2% of intracranial neoplasms; however, they are the most common primary cerebellar tumors in adults. Another frequent seat is the spinal cord (2-10% of primary spinal cord tumors). HBs are constituted by stromal and capillary vascular cells; macroscopically, HBs appear as nodular tumors, with or without cystic components. Although most of the HBs are sporadic (57-75%), they represent a particular component of von Hippel-Lindau disease (VHL), an autosomal dominant syndrome with high penetrance, due to a germline pathogenic mutation in the VHL gene, which is a tumor suppressor with chromosomal location on the short arm of chromosome three. VHL disease determines a variety of malignant and benign tumors, most frequently HBs, renal cell carcinomas, pheochromocytomas/paragangliomas, pancreatic neuroendocrine tumors, and endolymphatic sac tumors. Up to 20% of cases are due to de novo pathogenic variants without a family history. Many epidemiologic details of these tumors, especially the sporadic forms, are not well known. The median age of patients with sporadic HBS is about 40 years. More than two-third of VHL patients develop one or more central nervous system HBs during their lifetime; in case of VHL, patients at first diagnosis are usually younger than the patients with sporadic tumors. The most common presenting signs and symptoms are related to increased intracranial pressure, cerebellar signs, or spinal cord alterations in case of spinal involvement. Magnetic resonance imaging is the gold standard for the diagnosis, assessment, and follow-up of HBs, both sporadic and syndrome-related; angiography is rarely performed because the diagnosis is easily obtained with magnetic resonance. However, the diagnosis of an asymptomatic lesion does not automatically result in therapeutic actions, as the risks of treatment and the onset of possible neurological deficit need to be balanced, considering that HBs may remain asymptomatic and have a static or slow-growing behavior. In such cases, regular follow-up can represent a valid therapeutic option until the patients remain asymptomatic. There are no actual pharmacological therapies that are demonstrated to be effective for HBs. Surgery represents the primary therapeutic approach for these tumors. Observation or radiotherapy also plays a role in the long-term management of patients harboring HBs, especially in VHL; in few selected cases, endovascular treatment has been suggested before surgical removal. This chapter presents a systematic overview of epidemiology, clinical appearance, histopathological and neuroradiological characteristics of central nervous system HBs. Moreover, the genetic and molecular biology of sporadic and VHL HBS deserves special attention. Furthermore, we will describe all the available therapeutic options, along with the follow-up management. Finally, we will briefly report other vascular originating tumors as hemangioendotheliomas, hemangiomas, or angiosarcomas.

Towards an Established Intraoperative Oncological Favorable Tool: Results of Fluorescein-Guided Resection from a Monocentric, Prospective Series of 93 Primary Glioblastoma Patients

It is commonly reported that maximizing surgical resection of contrast-enhancing regions in patients with glioblastoma improves overall survival. Efforts to achieve an improved rate of resection have included several tools: among those, the recent widespread of fluorophores. Sodium fluorescein is an unspecific, vascular dye which tends to accumulate in areas with an altered blood-brain barrier. In this retrospective analysis of patients prospectively enrolled in the FLUOCERTUM study, we aimed to assess the role of fluorescein-guided surgery on surgical radicality, survival, and morbidity. A retrospective review based on 93 consecutively and prospectively enrolled IDH wild-type glioblastoma patients (2016-2022) was performed; fluorescence characteristics, rate of resection, clinical outcome, and survival were analyzed. No side effect related to fluorescein occurred; all of the tumors presented a strong yellow-green enhancement and fluorescein was judged fundamental in distinguishing tumors from viable tissue in all cases. Gross total resection was achieved in 77 cases out of 93 patients (82.8%). After a mean follow-up time of 17.4 months (3-78 months), the median progression-free survival was 12 months, with a PFS-6 and PFS-12 of 94.2% and 50%, respectively, whereas median overall survival was estimated to be 16 months; survival at 6, 12, and 24 months was 91.8%, 72.3%, and 30.1%, respectively. Based on these results, we can assert that the fluorescein-guided technique is a safe and valuable method for patients harboring a newly diagnosed, untreated glioblastoma.

The use of the sodium fluorescein and YELLOW 560 nm filter for the resection of pediatric posterior fossa lesions

PURPOSE

This study aimed to verify the feasibility, safety, and benefit of using fluorescein sodium (FL) and a YELLOW 560 nm filter in posterior fossa tumors in children.

METHODS

All cases of pediatric posterior fossa tumors that have undergone surgery using fluorescein (2018-2022) have been included and were examined retrospectively. In those cases where resection of the tumor was planned, a blinded neuroradiologist distinguished gross total resection and subtotal resection according to the postoperative MRI findings. The surgical report and medical files were reviewed regarding the intraoperative staining grade and adverse events. The grade of fluorescent staining of the targeted lesion was assessed as described in the surgical reports. The screening was conducted for any reference to the degree of fluorescent staining: "intense," "medium," "slight," and "no staining."

RESULTS

19 cases have been included. In 14 cases, a complete resection was initially intended. In 11 of these cases, a gross total resection could be achieved (78.6%). Staining was described as intense in most cases (58.8%). Except for yellow-colored urine, no side effects obviously related to FL were found throughout the observation period.

CONCLUSION

In combination with a specific filter, FL is a reliable, safe, and feasible tool in posterior fossa surgery in children.

The role of sodium fluorescein in pediatric supratentorial intra-axial tumor resection: new insights from a monocentric series of 33 consecutive patients

INTRODUCTION

Surgical resection represents the mainstay of treatment, in pediatric central nervous system (CNS) tumors, and aggressive resection correlates with prognosis for several histotypes. Sodium fluorescein (SF), a green, water-soluble dye, is used as neurosurgical fluorescent tracer thanks to its property to accumulate in cerebral regions of blood-brain barrier disruption, acting as a valid tool to improve the extent of resection in tumors enhancing at preoperative MRI. Brain neoplasms represent a heterogeneous group of tumors in the pediatric age, constituting the most common solid cancers; they typically show a varying degree of contrast enhancement on MRI.

MATERIALS AND 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 retrospective analysis of a group of 33 consecutive pediatric patients harboring a supratentorial lesion.

RESULTS

In 17 of 33 (51.5%) procedures, fluorescence was reported as intense; in 14 of 33 (42.4%), moderate; and in 2 of 33 (6.1%), slight. Intraoperative fluorescence corresponds to preoperative-MRI-documented contrast enhancement. In 28 of 33 (84.8%) surgical procedures, SF was considered useful; in 2 of 33 (6.1%), partial useful; and in 3 of 33 (9.1%), not essential because the tumor was already recognizable. No adverse effect to SF administration was registered.

CONCLUSION

Fluorescein-guided surgery with a dedicated filter on the microscope is a safe and effective technique to improve visualization and resection of different pediatric brain tumors.

Sodium fluorescein in pediatric oncological neurosurgery: a pilot study on 50 children

BACKGROUND

Sodium fluorescein (SF) is currently considered a valid intraoperative adjunct in the resection of high-grade brain lesions in adults. Experiences in pediatric groups and in low-grade gliomas and other low-grade lesions are still limited in literature, and subjective evaluation of fluorescence is still a limitation.

MATERIAL AND METHODS

This study retrospectively reviewed all patients with brain or spine lesions operated on from September 2021 to July 2022 in the Pediatric Neurosurgery Unit of Hôpital Femme Mère Enfant, Lyon, who had received 5 mg/kg of 10%. Surgery was performed using a YELLOW560 filter at crucial times. At the end of surgery, the first operator completed a questionnaire, including his opinion on whether SF had been useful in tumor resection, recorded as a binary variable. Post hoc, surgical images were reviewed using ImageJ, an open-source Java image processing platform. In order to compare independent discrete variables, we applied the Student's t test, and we applied the Chi-square or Fisher exact test for binary variables. A threshold of p < 0.05 was set for statistical significance.

RESULTS

We included 50 pediatric patients (0.2-17.6 years old). Forty/50 lesions showed SF uptake (80%). The differentiation between healthy and affected tissue, thanks to SF, subjectively evaluated by the surgeon, had as objective counterpart the statistically significant higher brightness of green in lesions, registered by the software (p < 0.001). SF overall allowed a good differentiation in 33/50 lesions, and overall utility of SF has been noted in 67% of them. When specifically considering gliomas, overall utility reached 75%.

CONCLUSION

SF is a feasible, safe, and useful intraoperative adjunct in pediatric neurosurgery. In particular, it seems to have a promising role in some low-grade infiltrating glial tumors. The subjective evaluation of fluorescence seems to be reliable with respect to image analyses software.

Fluorescein sodium in the surgical treatment of pleomorphic xanthoastrocytomas: Results from a retrospective study

OBJECTIVE

Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor, most commonly affecting children and young adults. Surgical resection represents the mainstay of treatment, and extent of resection is associated with improved survival. In this study, we analyzed the role of sodium fluorescein (SF) in improving intraoperative visualization easing resection.

METHODS

Surgical database of FLUOCERTUM study (Besta Institute, Milan, Italy) was retrospectively reviewed to find pleomorphic xanthoastrocytomas and anaplastic xanthoastrocytomas, according to WHO-2016/2021 classification, surgically removed by a fluorescein-guided technique from March 2016 to February 2022. SF was intravenously injected (5mg/kg) immediately after induction of general anesthesia. Tumors were removed using a microsurgical technique with the YELLOW 560 filter (Carl Zeiss Meditec, Oberkochen, Germany).

RESULTS

Twelve patients (7 males and 5 females; 3 pediatric patients, mean age 10 years, range 5 to 13 years and 9 adult patients, mean age 50.6 years, range 35 to 63 years) underwent fluorescein-guided surgery. No side effects related to SF occurred. In all tumors, contrast enhancement on preoperative MRI correlated with intense, heterogeneous yellow fluorescence with bright fluorescent cystic fluid. Fluorescein was considered helpful in distinguishing tumors from viable tissue in all cases. Gross total resection was achieved in 8 cases (66.7%); in 4 cases, otherwise, the resection was subtotal with fluorescent residual spots to avoid neurological worsening (33.3%).

CONCLUSIONS

The use of SF is a valuable method for safe fluorescence-guided tumor resection. Our data documented a positive effect of fluorescein-guided surgery on intraoperative visualization, suggesting a probable role in improving the extent of resection during yellow surgery of PXA.

Sporadic and von Hippel-Lindau Related Hemangioblastomas of Brain and Spinal Cord: Multimodal Imaging for Intraoperative Strategy

Hemangioblastomas (HBs) are rare, benign tumors often related to von Hippel-Lindau disease. They represent the most frequent primary cerebellar tumors in adults. Neurosurgical procedures aim to obtain a gross-total resection of tumor nodules, avoiding intra-postoperative hemorrhage. The introduction of new intraoperative imaging techniques has considerably changed surgical strategies in neuro-oncology. We present an overview of clinical and radiological data of a mono-institutional retrospective cohort, focusing on the role of intraoperative multimodal imaging in surgical strategy. From 2015 to 2021, we identified 64 (81%) cranial (42 cerebellar, 8 supratentorial, and 14 of the brainstem) HBs and 15 (19%) spinal (4 cervical and 11 dorsal) HBs in 79 patients. Intraoperatively, indocyanine green videoangiography with FLOW800 was used in 62 cases (52 cranial and 10 spinal), intraoperative ultrasound and contrast-enhanced ultrasounds in 22 cases (18 cranial and 4 spinal HBs), and fluorescein in 10 cases (in 6 cranial and 2 spinal cases used as SF-VA). Gross total resection was achieved in 100% of the cases (53 mural nodule removal and 26 complete resections of the solid tumor). No side effects were reported following the combination of these tools. Multimodal intraoperative techniques provide valuable and reliable information to identify the tumor and its vasculature, guiding a more precise and safer resection and reducing the risk of recurrence.

Intramedullary pancreatic adenocarcinoma metastasis: The first case in literature

BACKGROUND

Pancreatic cancer is a common gastrointestinal malignancy, and is often associated with a poor prognosis. Although liver is generally seen as a distant metastasis point, it has been shown that it can metastasize to any organ, especially the gastrointestinal tract, and approximately 0.3% of metastases are observed in spinal cord.

CASE DESCRIPTION

We report a 36-year-old woman with a prior history of pancreatic adenocarcinoma who presented to us with a thoracic intramedullary lesion and recent onset of neurological deficits. She underwent surgery with histological confirmation of a diagnosis of metastatic adenocarcinoma.

CONCLUSION

To our knowledge there is no prior report of pure intramedullary spinal cord metastasis from a pancreatic adenocarcinoma in the literature. We report the present patient in view of the rarity of intramedullary spinal cord metastasis and its clinical significance. Although intramedullary metastases are rare, they should be investigated in every patient with malignancy and progressive neurological deficit. While its general prognosis is poor regardless of the type of treatment, early diagnosis and treatment is important in terms of quality of life and survival.

Fluorescein-guided surgery for the resection of pilocytic astrocytomas: A multicentric retrospective study

Objective

Pilocytic astrocytomas (PAs) are relatively benign tumors, usually enhancing on post-contrast MRI and often characterized by a mural nodule within a cystic component. Surgical resection represents the mainstay of treatment, and extent of resection (EOR) is associated with improved survival. In this study, we analyzed the effect of sodium fluorescein (SF) on the visualization and resection of these circumscribed astrocytic gliomas.

Methods

Surgical databases at two neurosurgical departments (Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy and Department of Neurosurgery, University Medical Center Regensburg, Regensburg, Germany) were retrospectively reviewed to identify the cohort of patients with pilocytic astrocytoma who had undergone fluorescein-guided tumor resection at any of the centers between March 2016 and February 2022. SF was intravenously injected (5 mg/kg) immediately after the induction of general anesthesia. Tumors were removed using a microsurgical technique with the YELLOW 560 filter (Carl Zeiss Meditec, Oberkochen, Germany).

Results

Forty-four patients (25 males and 19 females; 26 pediatric patients, mean age of 9.77 years, range 2 to 17 years; and 18 adult patients, mean age of 34.39 years, range 18 to 58 years) underwent fluorescein-guided surgery. No side effects related to SF occurred. In all tumors, contrast enhancement on preoperative MRI was correlated with intense, heterogeneous yellow fluorescence with bright fluorescent cystic fluid. Fluorescein was considered helpful in distinguishing tumors from viable tissue in all cases except three patients due to faint fluorescein enhancement. Biopsy was intended in two operations, and partial resection was intended in three operations. Gross total resection was achieved in 24 cases out of 39 patients scheduled for tumor removal (61.54%), in five cases a minimal residual volume was highlighted by postoperative MRI despite the intraoperative subjective evaluation of complete tumor removal (12.82%); in the other 10 cases, the resection was subtotal with fluorescent residual spots to avoid neurological worsening (25.64%).

Conclusions

The use of SF is a valuable method for safe fluorescence-guided tumor resection. Our data showed a positive effect of fluorescein-guided surgery on intraoperative visualization during resection of Pas, suggesting a possible role in improving the extent of resection of these lesions.

5-aminolevulinic acid and sodium fluorescein in IV ventricle ependymoma surgery: preliminary experience comparing the two techniques

Purpose

The aim of this study is to compare the use of 5-aminolevulinic acid (5-ALA) and sodium fluorescein (SF) in IV ventricular ependymoma (IVEP) surgical resection.

Methods

In this retrospective study, six patients with IVEP were enrolled. Gender ratio 2:1 male to female, with mean age 38.9 years old. A 5-ALA oral dose of 20 mg/kg and a SF intravenous dose of 2 mg/kg were administered. Telo-velar approach, operative microscope, and intraoperative monitoring were used in all the operations. We retrospectively compared the two fluorescence techniques at four steps during the surgical procedure: step 1: exposure of the tumor; step 2: dissection of the lesion from the cerebellum; step 3: assessment of the tumor borders and differentiation from normal tissue at the base of implants; and step 4: evaluation of possible residual tissue in the surgical cavity.

Results

At the first step, the ependymomas resulted well delineated by both fluorescent agents. In this step, 5-ALA was particularly helpful in the case of recurrent ependymoma. At step 2, 5-ALA provided a better identification of the ependymoma boundaries and distinction from cerebellum hemispheres than SF. In steps 3 and 4, SF was really helpful to detect tumor tissue.

Conclusion

According to our experience, fluorescence-guided surgery of IVEP with 5-ALA and SF is useful to maximize surgical resection with less risk of brainstem injury. Both fluorescence techniques are helpful in different steps of IVEP resection. However, further studies are needed to confirm our preliminary data.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-022-06012-z.

Application of sodium fluorescein for spinal cord lesions: intraoperative localization for tissue biopsy and surgical resection

Sodium fluorescein (NaFL) has been used to aid in the resection of primary and secondary lesions within the brain. Comparatively, there is limited research on clinical applications for lesions within the spinal cord. Fluorescein-guided microsurgery may increase the ability to localize and safely surgically treat spinal lesions. Twelve patients with spinal cord lesions received fluorescein sodium 10% (Alcon Laboratories INC, Fort Worth, TX, USA) at 3 mg/kg prior to surgical resection. Intraoperative visualization of fluorescence was performed using a Zeiss Pentero (Carl Zeiss AG, Oberkochen, Germany) microscope equipped with a Yellow560 filter or a Leica OH6 (Leica Microsystems, Wetzlar, Germany) equipped with a FL560 filter. Administration of NaFL resulted in lesional fluorescent contrast extravasation and facilitated surgical resection and localization in all twelve patients. In patients with a goal of complete resection, NaFL aided in complete resection of the spinal lesions in seven patients. In surgical resection patients, pathology was consistent with WHO grade I myxopapillary ependymoma in one patient, WHO grade II ependymoma in five patients, and nerve sheath tumor in one patient. In the other five patients, NaFL allowed for intraoperative tissue identification and successful tissue biopsy. In patients undergoing biopsy, tissue samples were positive for an intramedullary abscess, EBV-driven lymphoproliferative disease, and primary glial neoplasms. Fluorescein is a helpful microsurgical tool in guiding surgical resection and in the localization of intramedullary spinal lesions. Further research is necessary to explore fluorescein sodium applications in the resection of spinal cord lesions.

Effect of 5-Aminolevulinic Acid and Sodium Fluorescein on the Extent of Resection in High-Grade Gliomas and Brain Metastasis

Surgery is essential in the treatment of high-grade gliomas (HGG) and gross total resection (GTR) is known to increase the overall survival and progression-free survival. Several studies have shown that fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) increases GTR considerably compared to white light surgery (65% vs. 36%). In recent years, sodium fluorescein (SF) has become an increasingly popular agent for fluorescence-guided surgery due to numerous utility benefits compared to 5-ALA, including lower cost, non-toxicity, easy administration during surgery and a wide indication range covering all contrast-enhancing lesions with disruption of the blood-brain barrier in the CNS. However, currently, SF is an off-label agent and the level of evidence for use in HGG surgery is inferior compared to 5-ALA. Here, we give an update and review the latest literature on fluorescence-guided surgery with 5-ALA and SF for brain tumors with emphasis on fluorescence-guided surgery in HGG and brain metastases. Further, we assess the advantages and disadvantages of both fluorophores and discuss their future perspectives.

Fluorescein-guided surgery for intradural spinal tumors: A single-center experience

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Gross total removal has a pivotal role in surgical treatment of intradural spinal tumors.

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Sodium fluorescein prevents vascular injuries also preserving pial vessels in posterior myelotomy.

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Fluorescence before the durotomy helps to distinguishing tumor from healthy tissue in intradural lesions.

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Intraoperative fluorescence is safe and effective, also preserving functional anatomy in tumor removal.

Intracranial Sonodynamic Therapy With 5-Aminolevulinic Acid and Sodium Fluorescein: Safety Study in a Porcine Model

Background

Sonodynamic therapy (SDT) is an emerging ultrasound-based treatment modality for malignant gliomas which combines ultrasound with sonosensitizers to produce a localized cytotoxic and modulatory effect. Tumor-specificity of the treatment is achieved by the selective extravasation and accumulation of sonosensitizers in the tumor-bearing regions. The aim of this study is to demonstrate the safety of low-intensity ultrasonic irradiation of healthy brain tissue after the administration of FDA-approved sonosensitizers used for SDT in experimental studies in an in vivo large animal model.

Methods

In vivo safety of fluorescein (Na-Fl)- and 5 aminolevulinic acid (5-ALA)-mediated low-intensity ultrasound irradiation of healthy brain parenchyma was assessed in two sets of four healthy swine brains, using the magnetic resonance imaging (MRI)-guided Insightec ExAblate 4000 220 kHz system. After administration of the sonosensitizers, a wide fronto-parietal craniotomy was performed in pig skulls to allow transmission of ultrasonic beams. Sonication was performed on different spots within the thalamus and periventricular white matter with continuous thermal monitoring. Sonication-related effects were investigated with MRI and histological analysis.

Results

Post-treatment MRI images acquired within one hour following the last sonication, on day one, and day seven did not visualize any sign of brain damage. On histopathology, no signs of necrosis or apoptosis attributable to the ultrasonic treatments were shown in target areas.

Conclusions

The results of the present study suggest that either Na-FL or 5-ALA-mediated sonodynamic therapies under MRI-guidance with the current acoustic parameters are safe towards healthy brain tissue in a large in vivo model. These results further support growing interest in clinical translation of sonodynamic therapy for intracranial gliomas and other brain tumors.

Second-Window Indocyanine Green for Visualization of Hemangioblastoma: A Case Report With Two-Dimensional Operative Video

BACKGROUND AND IMPORTANCE

The proper differentiation of neoplastic tissue from adjacent brain parenchyma can pose a great challenge, especially in eloquent areas of the brain. With the novel technique, "Second-Window Indocyanine Green," injection of a near-infrared fluorophore (ICG) allows for intraoperative visualization of tumors by taking advantage of the compromised vasculature surrounding the tumor. Thus, such a technique may demonstrate utility for hemangioblastomas, which are hypervascular tumors of the central nervous system.

CLINICAL PRESENTATION

Here we present the case of a 39-yr-old male with a demonstrated cystic mass in the left cerebellum, with additional edema spreading towards the vermis. A total of 5 mg/kg of ICG was delivered intravenously 24 h prior to the operation. The tumor was approached via the infratentorial suboccipital approach. We observed strong near-infrared fluorescence through the intact dura, consistent with the tumor location. Surgical pathology confirmed a final diagnosis of cerebellar hemangioblastoma. There was complete resection of the tumor, with the patient discharged uneventfully.

CONCLUSION

We report the first successful case of fluorescence-guided surgery of a cerebellar hemangioblastoma using near-infrared fluorescence imaging with the Second-Window ICG technique. This joins a growing series of publications that demonstrate the efficacy of a novel application of ICG, a near-infrared fluorophore, in accurate intraoperative visualization of neoplastic tissue. While the use of a dedicated near-infrared platform (ie, the VisionSense Iridium [Visionsense, Philadelphia, Pennsylvania]) yields a higher signal-to-background ratio, a neurosurgical microscope (ie, the Leica OH6 [Leica Microsystems, Wetzlar, Germany]) may also provide a suitable option in cases where fluorescence is very strong.

Fluorescence-Guided Surgery: A Review on Timing and Use in Brain Tumor Surgery

Fluorescence-guided surgery (FGS) allows surgeons to have improved visualization of tumor tissue in the operating room, enabling maximal safe resection of malignant brain tumors. Over the past two decades, multiple fluorescent agents have been studied for FGS, including 5-aminolevulinic acid (5-ALA), fluorescein sodium, and indocyanine green (ICG). Both non-targeted and targeted fluorescent agents are currently being used in clinical practice, as well as under investigation, for glioma visualization and resection. While the efficacy of intraoperative fluorescence in studied fluorophores has been well established in the literature, the effect of timing on fluorophore administration in glioma surgery has not been as well depicted. In the past year, recent studies of 5-ALA use have shown that intraoperative fluorescence may persist beyond the previously studied window used in prior multicenter trials. Additionally, the use of fluorophores for different brain tumor types is discussed in detail, including a discussion of choosing the right fluorophore based on tumor etiology. In the following review, the authors will describe the temporal nature of the various fluorophores used in glioma surgery, what remains uncertain in FGS, and provide a guide for using fluorescence as a surgical adjunct in brain tumor surgery.

Intramedullary pancreatic adenocarcinoma metastasis: The first case in literature

BACKGROUND

Pancreatic cancer is a common gastrointestinal malignancy, and is often associated with a poor prognosis. Although liver is generally seen as a distant metastasis point, it has been shown that it can metastasize to any organ, especially the gastrointestinal tract, and approximately 0.3% of metastases are observed in spinal cord.

CASE DESCRIPTION

We report a 36-year-old woman with a prior history of pancreatic adenocarcinoma who presented to us with a thoracic intramedullary lesion and recent onset of neurological deficits. She underwent surgery with histological confirmation of a diagnosis of metastatic adenocarcinoma.

CONCLUSION

To our knowledge there is no prior report of pure intramedullary spinal cord metastasis from a pancreatic adenocarcinoma in the literature. We report the present patient in view of the rarity of intramedullary spinal cord metastasis and its clinical significance. Although intramedullary metastases are rare, they should be investigated in every patient with malignancy and progressive neurological deficit. While its general prognosis is poor regardless of the type of treatment, early diagnosis and treatment is important in terms of quality of life and survival.

Sodium Fluorescein for Spinal Intradural Tumors

Technological innovations in spinal intradural tumor surgery simplify treatment. Surgical treatment of cranial benign and malignant pathologies under microscope with sodium (Na)-fluorescein guidance has often been reported, but few studies have focused on spinal intradural tumors. We aimed to investigate the usefulness of Na-fluorescein under yellow filter in intradural spinal tumor surgery by retrospectively reviewing cases involving intramedullary and extramedullary tumors operated under the guidance of Na-fluorescein. Forty-nine adult patients with a diagnosis of spinal intradural tumor operated under a yellow filter (560 nm) microscope using Na-fluorescein dye were included in the study. Demographic data, such as age and sex, neurological status, extent of tumor resection, histopathological diagnosis, Na-fluorescein staining pattern, and its usefulness during surgery were noted and statistically analyzed. Of all recruited patients, 26 women (53.1%) and 23 men (46.9%), were included for analysis. The age range of the patients was 18–64 years, with a mean age of 41.6 ± 13.9. An intradural intramedullary mass was found in 30.6% (n = 15) of the patients, and an intradural extramedullary mass in 69.4% (n: 34). While Na-fluorescein staining was homogeneous in all intradural extramedullary tumors, 73.3% (n: 11) of intradural intramedullary tumors were homogeneous, and 13.3% (n: 2) moderately heterogeneous. In the whole study group, the Na-fluorescein staining pattern was helpful in surgical resection in 47 cases (95.9%). While 34/34 (100%) found it helpful for extramedullary tumors, 13/15 (86.7%) did in intramedullary tumors, and for 2/15 (13.3%) it was not. In conclusion, Na-fluorescein helps in distinguishing tumor from healthy tissue in intradural extramedullary and intramedullary tumor surgery under a yellow filter microscope in most cases, thus providing convenient assistance to surgeons.

Fluorescein-guided removal of peripheral nerve sheath tumors: a preliminary analysis of 20 cases

OBJECTIVE

Benign peripheral nerve sheath tumors (PNSTs) include mainly schwannomas-the most common tumors arising from peripheral nerves-and neurofibromas. Due to their origin, distinguishing between functional intact nerve and the fibers from whence the PNST arose may not always be easy to perform. The introduction of intraoperative tools to better visualize these tumors could be helpful in achieving a gross-total resection. In this study, the authors present a series of patients harboring PNST in which the surgery was performed under fluorescein guidance.

METHODS

Between September 2018 and February 2019, 20 consecutive patients with a total of 25 suspected PNSTs underwent fluorescein-guided surgery performed under microscopic view with a dedicated filter integrated into the surgical microscope (YELLOW 560) and with intraoperative monitoring. All patients presented with a different degree of contrast enhancement at preoperative MRI. Fluorescein was intravenously injected after intubation at a dose of 1 mg/kg. Preoperative clinical and radiological data, intraoperative fluorescein characteristics, and postoperative neurological and radiological outcomes were collected and analyzed.

RESULTS

Six patients were affected by neurofibromatosis or schwannomatosis. There were 14 schwannomas, 8 neurofibromas, 1 myxoma, 1 reactive follicular hyperplasia, and 1 giant cell tumor of tendon sheath. No patient experienced worsening of neurological status after surgery. No side effects related to fluorescein injection were found in this series. Fluorescein allowed an optimal intraoperative distinction between tumor and surrounding nerves in 13 of 14 schwannomas and in all neurofibromas. In 6 neurofibromas and in 1 schwannoma, the final YELLOW 560 visualization showed the presence of small tumor remnants that were not visible under white-light illumination and that could be removed, obtaining a gross-total resection.

CONCLUSIONS

Fluorescein was demonstrated to be a feasible, safe, and helpful intraoperative adjunct to better identify and distinguish PNSTs from intact functional nerves, with a possible impact on tumor resection, particularly in diffuse neurofibromas.

Intraoperative imaging of brain tumors with fluorescein: confocal laser endomicroscopy in neurosurgery. Clinical and user experience

OBJECTIVE

Confocal laser endomicroscopy (CLE) is an established tool in basic research for tissue imaging at the level of microstructures. Miniaturization and refinement of the technology have made this modality available for operative imaging with a handheld device. Sufficient image contrast is provided by the preoperative application of fluorescein sodium. The authors report their first experiences in a clinical case series using the new confocal laser endomicroscope.

METHODS

Handling, operative workflow, and visualization of the CLE were critically evaluated in 12 cases of different CNS tumors. Three different imaging positions in relation to the tumor were chosen: the tumor border (I), tumor center (II), and perilesional zone (III). Respective diagnostic sampling with H & E staining and matching intraoperative neuronavigation and microscope images are provided.

RESULTS

CLE was found to be beneficial in terms of high-quality visualization of fine structures and for displaying hidden anatomical details. The handling of the device was good, and the workflow was easy.

CONCLUSIONS

Handling ergonomics and image acquisition are intuitive. The endomicroscope allows excellent additional visualization of microstructures in the surgical field with a minimally invasive technique and could improve safety and clinical outcomes. The new confocal laser endomicroscope is an advanced tool with the potential to change intracranial tumor surgery. Imaging of these microstructures is novel, and research with comparative validation with traditional neuropathological assessments is needed.

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.

[Visual fluorescence combined with laser spectroscopy in surgery for intramedullary spinal cord tumors]

BACKGROUND

Surgical treatment of intramedullary spinal cord tumors is aimed at total resection of tumor with maximum preservation of neurological and functional status. In some cases, intramedullary tumors have unclear dissection plane or gliosis zone. This area is not a tumor and does not require resection. However, it is difficult to distinguish visually intact spinal cord tissue and tumor at the last surgical stages. Thus, we evaluated the effectiveness of fluorescence combined with laser spectroscopy in surgical treatment of intramedullary spinal cord tumors.

OBJECTIVE

To determine the effectiveness of visual fluorescence combined with laser spectroscopy in surgery for intramedullary spinal cord tumors.

MATERIAL AND METHODS

There were 850 patients with intramedullary spinal cord tumors for the period 2001-2019. In 35 cases, intraoperative fluoroscopy with laser spectroscopy were used. All patients underwent a comprehensive pre- and postoperative clinical and instrumental examination (general and neurological status, McCormick grade, spinal cord MRI). Carl Zeiss OPMI Pentero microscope with a fluorescent module was used for intraoperative fluorescence diagnosis. A domestic preparation 5-ALA «ALASENS» (State Research Center NIOPIK, Moscow, Russia) was used for induction of visible fluorescence. Laser spectroscopy was carried out using a LESA-01-BIOSPEK spectrum analyzer. Morphological analysis of intramedullary spinal cord tumors was performed in the neuromorphology laboratory of the Burdenko Neurosurgery Center.

RESULTS

Intramedullary anaplastic ependymoma and astrocytoma, as well as conventional ependymoma were characterized by the highest index of 5-ALA accumulation. Intramedullary hemangioblastoma and cavernoma do not accumulate 5-aminolevulinic acid due to morphological structure of these tumors. In particular, there are no cells capable of capturing and processing 5-ALA in these tumors. Sensitivity of visual fluorescence combined with laser spectroscopy varies from 0% to 100% depending on the histological type of tumor: hemangiogblastoma and cavernoma - 0%, low-grade astrocytoma - 70%, high-grade astrocytoma - 80%, ependymoma - 92%, anaplastic ependymoma 100%. Dissection plane is absent in anaplastic ependymoma, high-grade astrocytoma. We often observed gliosis during resection of ependymoma. This tissue is not a part of tumor. Intraoperative metabolic navigation with neurophysiological monitoring are advisable for total tumor resection in case of unclear dissection plane and peritumoral gliosis.

CONCLUSION

Visual fluorescence combined with laser spectroscopy is a perspective method for intraoperative imaging of tumor remnants and total resection of intramedullary spinal cord tumors with minimum risk of neurological impairment.

Lighting Up the Tumor-Fluorescein-Guided Resection of Gangliogliomas

(1) Background: Gangliogliomas comprise a small number of brain tumors. They usually present as World Health Organization (WHO) grade I, and they delineate on gadolinium-enhanced MRI; the surgical goal is wide radical resection, and the course thereafter is usually benign. Fluorescein sodium (FL) tends to accumulate in areas with altered blood–brain barrier (BBB). Thus far, the results provided by prospective and retrospective studies show that the utilization of this fluorophore may be associated with better visualization and improvement of resection for several tumors of the central nervous system. In this study, we retrospectively studied the effect of fluorescein sodium on visualization and resection of gangliogliomas. (2) Methods: Surgical databases in three neurosurgical departments (Regensburg University Hospital; Besta Institute, Milano, Italy; and Liv Hospital, Istanbul, Turkey), with approval by the local ethics committee, were retrospectively reviewed to find gangliogliomas surgically removed by a fluorescein-guided technique by the aid of a dedicated filter on the surgical microscope from April 2014 to February 2020. Eighteen patients (13 women, 5 men; mean age 22.9 years, range 3 to 78 years) underwent surgical treatment for gangliogliomas during 19 operations. Fluorescein was intravenously injected (5 mg/kg) after general anesthesia induction. Tumors were removed using a microsurgical technique with the YELLOW 560 Filter (YE560) (KINEVO/PENTERO 900, Carl Zeiss Meditec, Oberkochen, Germany). (3) Results: No side effects related to fluorescein occurred. In all tumors, contrast enhancement on preoperative MRI correlated with bright yellow fluorescence during the surgical procedure (17 gangliogliomas WHO grade I, 1 ganglioglioma WHO grade II). Fluorescein was considered helpful by the operating surgeon in distinguishing tumors from viable tissue in all cases (100%). Biopsy was intended in two operations, and subtotal resection was intended in one operation. In all other operations considered preoperatively eligible, gross total resection (GTR) was achieved in 12 out of 16 (75%) instances. (4) Conclusions: The use of FL and YE560 is a readily available method for safe fluorescence-guided tumor resection, possibly visualizing tumor margins intraoperatively similar to contrast enhancement in T1-weighted MRI. Our data suggested a positive effect of fluorescein-guided surgery on intraoperative visualization and extent of resection during resection of gangliogliomas.

The Central Dot Sign : A Specific Post-gadolinium Enhancement Feature of Intramedullary Spinal Cord Metastases

PURPOSE

Peripheral enhancement characteristics on magnetic resonance imaging (MRI), namely the rim and flame signs, are specific for intramedullary spinal cord metastases (ISCM) compared to primary cord masses. The study compared the frequency of a novel finding-the central dot sign-in ISCMs versus primary intramedullary masses.

METHODS

In this study 45 patients with 64 ISCMs and 64 control patients with 64 primary intramedullary cord masses were investigated and 2 radiologists blinded to lesion type independently evaluated MR images for the presence of a central dot sign: a punctate focus of enhancement in/near the center of an enhancing intramedullary mass. The frequency of this sign in the two patient groups was compared.

RESULTS

A total of 63 enhancing ISCMs in 44 patients and 54 enhancing primary cord masses in 54 patients were included. The central dot sign was identified in 6% (4/63) of enhancing ISCMs in 9% (4/44) of patients and in none (0/54) of the enhancing primary cord masses (p = 0.038, per patient). The specificity for diagnosing ISCMs among spinal cord masses was 100%. The central dot sign was present in the axial plane only in two ISCMs and in the axial and sagittal planes in two ISCMs. The two ISCMs harboring the central dot sign also demonstrated both the previously described rim and flame signs, and two also demonstrated the rim sign alone.

CONCLUSION

The central dot sign is not sensitive but highly specific for ISCMs compared to primary spinal cord masses. The rim and/or flame signs may or may not be concurrently present in ISCMs.

Ten-Segment Intramedullary Ependymoma and Whole Spinal Syringomyelia

BACKGROUND

Ten-segment intramedullary tumors are rare lesions in adults.

CASE DESCRIPTION

In this report, we describe the case of a 30-year-old woman who presented with a 2-year history of right lower limb numbness. Spinal magnetic resonance imaging showed an expansive 10-segment intramedullary lesion and syringomyelia. The final pathologic tests confirmed World Health Organization grade II ependymoma. She received a successful gross total tumorectomy with no obvious surgical-related complications.

CONCLUSIONS

The postoperative recovery is far beyond our expectations.

Fluorescence Imaging of Nerves During Surgery

OBJECTIVE

This review details the agents for fluorescence-guided nerve imaging in both preclinical and clinical use to identify factors important in selecting nerve-specific fluorescent agents for surgical procedures.

BACKGROUND

Iatrogenic nerve injury remains a significant cause of morbidity in patients undergoing surgical procedures. Current real-time identification of nerves during surgery involves neurophysiologic nerve stimulation, which has practical limitations. Intraoperative fluorescence-guided imaging provides a complimentary means of differentiating tissue types and pathology. Recent advances in fluorescence-guided nerve imaging have shown promise, but the ideal agent remains elusive.

METHODS

In February 2018, PubMed was searched for articles investigating peripheral nerve fluorescence. Key terms used in this search include: "intraoperative, nerve, fluorescence, peripheral nerve, visualization, near infrared, and myelin." Limits were set to exclude articles exclusively dealing with central nervous system targets or written in languages other than English. References were cross-checked for articles not otherwise identified.

RESULTS

Of the nonspecific agents, tracers that rely on axonal transport showed the greatest tissue specificity; however, neurovascular dyes already enjoy wide clinical use. Fluorophores specific to nerve moieties result in excellent nerve to background ratios. Although noteworthy findings on tissue specificity, toxicity, and route of administration specific to each fluorescent agent were reported, significant data objectively quantifying nerve-specific fluorescence and toxicity are lacking.

CONCLUSIONS

Fluorescence-based nerve enhancement has advanced rapidly over the past 10 years with potential for continued utilization and progression in translational research. An ideal agent would be easily administered perioperatively, would not cross the blood-brain barrier, and would fluoresce in the near-infrared spectrum. Agents administered systemically that target nerve-specific moieties have shown the greatest promise. Based on the heterogeneity of published studies and methods for reporting outcomes, it appears that the development of an optimal nerve imaging agent remains challenging.

Sodium Fluorescein as Intraoperative Visualization Tool During Peripheral Nerve Biopsies

OBJECTIVE

Owing to technical development of specific fluorophore filters, the neurosurgical application of sodium fluorescein (SF) has regained value in brain tumor surgery. The aim of this study was to determine the usefulness of SF during nerve biopsies.

METHODS

This single-center study included 5 cases of nerve biopsies performed under microscope-based fluorescence with SF performed between March 2016 and February 2017. SF was applied intravenously (1 mg/kg body weight). After microsurgical dissection of the involved nerve segment, fluorescence-guided fascicular biopsy was performed. Selection of target fascicles was at the surgeon's discretion and took into account nerve stimulation for preservation of motor function and fluorescence intensity. Correlation to histopathologic examination was examined. Video analysis of intraoperative images comparing target fascicles with intense fluorescent response to adjacent fascicles of the same nerve segment was performed using ImageJ.

RESULTS

All patients had motor or sensory deficits. Magnetic resonance imaging findings were similar, depicting long segments of gadolinium enhancement (minimum 11.7 cm). Each biopsy sample was positive resulting in diverse histopathologic results. Digital image analysis revealed a statistically significant difference of the complementary color green (P = 0.0473).

CONCLUSIONS

Magnetic resonance imaging is the gold standard in diagnostic work-up of peripheral nerve disorders. Longitudinal nerve thickening with positive contrast enhancement is an unspecific magnetic resonance imaging finding. Various pathologies, such as tumors and inflammatory lesions, may cause this morphologic phenomenon. Nerve biopsies may be needed for diagnostic work-up. Intraoperative SF may help to depict the most affected fascicles and identify target fascicles for biopsy and increase diagnostic certainty of nerve biopsies.

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.

The impact of fluorescein-guided technique in the surgical removal of CNS tumors in a pediatric population: results from a multicentric observational study

BACKGROUND

Surgery has a fundamental role in central nervous system (CNS) tumors in the pediatric population, as aggressive resection correlates with prognosis. Due to its accumulation in areas with damaged blood brain barrier, sodium fluorescein (SF) could be a valid tool to improve the extent of resection in tumors enhancing at preoperative MRI. This study is aimed to systematically assess the utility of SF in a pediatric population.

METHODS

Patient data were collected in two centers, one in Italy and the other in Germany. At the induction of anesthesia, SF was administered intravenously (5 mg/kg). Surgery was performed using a YELLOW560 filter. Fluorescence intensity was graduated as bright, moderate or absent based on surgeon's opinion; furthermore, SF use was judged as "helpful," "not helpful" or "not essential" in tumor removal.

RESULTS

Twenty-four patients for 27 surgical procedures were identified. In 21 of 27 (77.8%) procedures fluorescence was reported as bright or moderate, in two of 27 (7.4%) absent and in four of 27 (14.8%) data were unavailable. Intraoperative fluorescence was reported in 21 of 25 (84%) surgeries whose corresponding preoperative MRI had shown contrast enhancement. In 14 of 27 (51.8%) surgical procedures SF was considered "helpful"; in two of 27 (7.4%) not "helpful"; in seven of 27 (25.9%) "not essential." In four of 27 (14.8%) data were unavailable. No adverse effect to SF was registered.

CONCLUSIONS

SF could be considered a valid and safe tool to improve visualization of tumors enhancing at preoperative MRI also in pediatric patients. Future prospective studies are needed to confirm these preliminary data.

Novel Technique of Coregistered Intraoperative Computed Tomography and Preoperative Magnetic Resonance Imaging and Diffusion Tensor Imaging Navigation in Spinal Cord Tumor Resection

Background: Intradural spinal tumors are surgically challenging lesions, and intraoperative spinal navigation offers clear potential assistance. While intraoperative computed tomography (iCT) of bony anatomy is routinely performed, coregistration with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) to facilitate intradural spinal tumor resection is not widely described. We present 2 cases in which iCT was coregistered with MRI and DTI for navigational guidance in the resection of intradural spinal tumors to assess technical feasibility and surgical efficacy. Case Series: Navigation using coregistered iCT/MRI was used in the resection of one extramedullary and one intramedullary cervicomedullary tumor. The iCT was obtained following open midline exposure of bony anatomy. The images were then coregistered with preoperative MRI sequences to allow for optical tracking navigation via an optical tracking station (Brainlab). For the intramedullary tumor, preoperative DTI sequences were also coregistered for enhanced identification of relevant anatomy. Navigational accuracy for all cases was confirmed to be acceptable at the level of the posterior bony elements, the dura, and the tumor-parenchyma interface. Conclusion: The coregistration of preoperative MRI sequences and iCT images allowed for meaningfully enhanced navigation during resection. In the case involving the intramedullary cervicomedullary tumor with marked distortion of longitudinal tracts, iCT/DTI navigation allowed for accurate visualization of critical structures and facilitated delineation of tumor margins that otherwise would have been difficult. The use of combined iCT and preoperative MRI/DTI neuronavigational guidance is an effective approach in the resection of intradural extramedullary and intramedullary spinal cord tumors.

Sodium fluorescein-guided brain tumor surgery under the YELLOW-560-nm surgical microscope filter in pediatric age group: feasibility and preliminary results

OBJECTIVE

To evaluate the feasibility and safety of sodium fluorescein (Na-Fl)-guided surgery with the use of the PENTERO 900 surgical microscope (Carl Zeiss, Meditec, Oberkochen, Germany) equipped with the YELLOW-560-nm filter and low-dose Na-Fl (2 mg/kg) in pediatric brain tumor surgery.

METHODS

The study included 23 pediatric patients with various intracranial pathologies, who underwent Na-Fl-guided surgery between April 2015 and February 2018. Clinical features, surgical observations, extent of resection, and tumor histopathology were retrospectively analyzed. The use of YELLOW-560-nm filter was found "helpful" if the discrimination of the pinkish brain tissue and bright yellow stained tumor tissue was clear. Otherwise, it was described as "not helpful."

RESULTS

There were 11 female and 12 male patients with a mean age of 9.4 years. There were 7 brain stem/tectal plate gliomas, 6 supratentorial tumors, 4 intraventricular tumors, 2 pineal tumors, 2 infratentorial tumors, 1 clivus tumor, and 1 tumor with supra- and infratentorial extensions in the current series. Na-Fl was found helpful by means of the tumor demarcation in 20 instances (87%). In 11 of these 20 operations (55%), a total resection was achieved regardless of the tumor pathology. A subtotal resection was achieved in the remaining 9 patients (45%). No adverse events or side effects were encountered with regard to Na-Fl use.

CONCLUSION

Na-Fl guidance with the use of the YELLOW-560 filter is safe and effective during brain tumor surgery in pediatric age group.

Parathyroid gland management using optical technologies during thyroidectomy or parathyroidectomy: A systematic review

New optical technologies enhancing localization or assessing viability of parathyroid glands (PG) during endocrine surgery have been reported in clinical studies. These technologies could become complementary to the surgeon's eyes and may improve surgical outcomes in thyroidectomy and parathyroidectomy. Here, we conducted a systematic review focusing on PG identification and functional assessment using optical methods to enhance surgery. A systematic literature review was performed using MEDLINE and Embase database. Two authors selected studies and extracted data; qualitative analysis was performed to summarize the characteristics of reported optical tools for thyroidectomy or parathyroidectomy. Identification and vascularisation of PG during surgery were evaluated. Clinical and biochemical outcomes were appraised when reported. Studies relating to parathyroidectomy or thyroidectomy combined with autofluorescence, fluorescent methylene blue, 5-aminolevulinic acid, indocyanine green (ICG), optical coherence tomography, laser speckle contrast imaging, dynamic optical contrast imaging and Raman spectroscopy were identified with MEDLINE and Embase. We included a total of 47 relevant articles with a total of 1615 patients enrolled. Each optical technique is described and appreciated related to its surgical purpose. Autofluorescence and ICG imaging of PG are the most widely reported optical technologies for identification and assessment of vascularisation of PG. Results are mainly based on observational studies and argue for the feasibility of both techniques in endocrine surgery but prospective randomized studies have not been performed. In vivo applications are still limited for the other methods and further investigations correlating these techniques with post-operative parathormone measurements are still needed before considering these technologies in clinical practice.

Utilization of intraoperative confocal laser endomicroscopy in brain tumor surgery

Precise identification of tumor margins is of the utmost importance in neuro-oncology. Confocal microscopy is capable of rapid imaging of fresh tissues at cellular resolution and has been miniaturized into handheld probe-based systems suitable for use in the operating room. We aimed to perform a literature review to provide an update on the current status of confocal laser endomicroscopy (CLE) technology for brain tumor surgery. Aside from benchtop confocal microscopes used in ex vivo fashion, there are four CLE systems that have been investigated for potential application in the workflow of brain tumor surgery. Preclinical studies on animal tumor models and clinical studies on human brain tumors have assessed in vivo and ex vivo imaging approaches, suggesting that confocal microscopy holds promise for rapid identification of the characteristic (diagnostic) histological features of tumor and normal brain tissues. However, there are few studies assessing diagnostic accuracy sufficient to provide a definitive determination of the clinical and economical value of CLE in brain tumor surgery. Intraoperative real-time, high-resolution tissue imaging has significant clinical potential in the field of neuro-oncology. CLE is an emerging imaging technology that shows promise for improving brain tumor surgery workflow in in vivo and ex vivo studies. Future clinical studies are necessary to demonstrate clinical and economic benefit of CLE.

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.

The role of indocyanine green videoangiography with FLOW 800 analysis for the surgical management of central nervous system tumors: an update

OBJECTIVE

Indocyanine green videoangiography (ICG-VA) is an intraoperative technique used to highlight vessels in neurovascular surgery. Its application in the study of the vascular pathophysiology in CNS tumors and its role in their surgical management are still rather limited. A recent innovation of ICG-VA (i.e., the FLOW 800 algorithm integrated in the surgical microscope) allows a semiquantitative evaluation of cerebral blood flow. The aim of this study was to evaluate for the first time the systematic application of ICG-VA and FLOW 800 analysis during surgical removal of CNS tumors.

METHODS

Between May 2011 and December 2017, all cases in which ICG-VA and FLOW 800 analysis were used at least one time before, during, or after the tumor resection, and in which surgical videos were available, were retrospectively reviewed. Results of the histological analysis were analyzed together with the intraoperative ICG-VA with FLOW 800 in order to investigate the tumor-related videoangiographic features.

RESULTS

Seventy-one patients who underwent surgery for cerebral and spinal tumors were intraoperatively analyzed using ICG-VA with FLOW 800, either before or after tumor resection, for a total of 93 videoangiographic studies. The histological diagnosis was meningioma in 25 cases, glioma in 14, metastasis in 7, pineal region tumor in 5, hemangioblastoma in 4, chordoma in 3, and other histological types in 13 cases. The authors identified 4 possible applications of ICG-VA and FLOW 800 in CNS tumor surgery: extradural surveys allowed exploration of sinus patency and the course of veins before dural opening; preresection surveys helped in identifying pathological vascularization (arteriovenous fistulas and neo-angiogenesis) and regional venous outflow, and in performing temporary venous clipping tests, when necessary; postresection surveys were conducted to evaluate arterial and venous patency and parenchymal perfusion after tumor removal; and a premyelotomy survey was conducted in intramedullary tumors to highlight the posterior median sulcus.

CONCLUSIONS

The authors found ICG-VA with FLOW 800 to be a useful method to monitor blood flow in the exposed vessels and parenchyma during microsurgical removal of CNS tumors in selected cases. In particular, a preresection survey provides useful information about pathophysiological changes of brain vasculature related to the tumor and aids in the individuation of helpful landmarks for the surgical approach, and the postresection survey helps to prevent potential complications associated with the resection (such as local hypoperfusion or venous infarction).

The utilization of fluorescein in brain tumor surgery: a systematic review

INTRODUCTION

Sodium fluorescein (SF) is a green, water-soluble dye with the capacity to accumulate in cerebral areas as a result of damaged blood-brain barrier (BBB); this property allows SF to concentrate specifically at the tumor site of various types of brain neoplasms, making the tumor tissue more clearly visible.

EVIDENCE ACQUISITION

A literature search (1947-2018) was conducted with the keywords "fluorescein neurosurgery," "YELLOW neurosurgery," "fluorescein brain tumor," "YELLOW brain tumor." We included clinical studies, clinical trials, observational studies, only conducted on humans and concerning surgery; in addition, we have included 3 articles derived from the analysis of the references of other papers. Ultimately, 57 articles were included for further analysis.

EVIDENCE SYNTHESIS

Fluorescein as a fluorescent tracer in neuro-oncology is gaining a wider acceptance in the neurosurgical literature: until February 1st, 2018, at least 1099 neuro-oncological patients have been operated through fluorescein-assistance, mostly only after 2012. The most important application remains the aim to improve tumor visualization and extent of resection for high-grade gliomas (HGG), but the nonspecific mechanism of action is the theoretical base for its use also for tumors different from HGG. Nevertheless, no homogenous protocol of fluorescein utilization in neurosurgical oncology can be found in literature.

CONCLUSIONS

Fluorescein-guided surgery is a safe and effective technique to improve visualization and resection of different CNS tumors and conditions, based on BBB alteration, with a growing evidence-based background.

Diagnostic Accuracy of a Confocal Laser Endomicroscope for In Vivo Differentiation Between Normal Injured And Tumor Tissue During Fluorescein-Guided Glioma Resection: Laboratory Investigation

OBJECTIVE

Glioma resection with fluorescein sodium (FNa) guidance has a potential drawback of nonspecific leakage of FNa from nontumor areas with a compromised blood-brain barrier. We investigated the diagnostic accuracy of in vivo confocal laser endomicroscopy (CLE) after FNa administration to differentiate normal brain, injured normal brain, and tumor tissue in an animal glioma model.

METHODS

GL261-Luc2 gliomas in C57BL/6 mice were used as a brain tumor model. CLE images of normal, injured normal, and tumor brain tissues were collected after intravenous FNa administration. Correlative sections stained with hematoxylin and eosin were taken at the same sites. A set of 40 CLE images was given to 1 neuropathologist and 3 neurosurgeons to assess diagnostic accuracy and rate image quality (1-10 scale). Additionally, we developed a deep convolution neural network (DCNN) model for automatic image classification.

RESULTS

The mean observer accuracy for correct diagnosis of glioma compared with either injured or uninjured brain using CLE images was 85%, and the DCNN model accuracy was 80%. For differentiation of tumor from nontumor tissue, the experts' mean accuracy, specificity, and sensitivity were 90%, 86%, and 96%, respectively, with high interobserver agreement overall (Cohen κ = 0.74). The percentage of correctly identified images was significantly higher for images with a quality rating >5 (104/116, 90%) than for images with a quality rating ≤5 (32/44, 73%) (P = 0.007).

CONCLUSIONS

With sufficient FNa present in tissues, CLE was an effective tool for intraoperative differentiation among normal, injured normal, and tumor brain tissue. Clinical studies are warranted to confirm these findings.