Confocal Laser Microscopy in Neurosurgery: State of the Art of Actual Clinical Applications

Roving histological imaging for navigation-confirmed glioma negative margin by handheld endomicroscopy: a parallel controlled study

INTRODUCTION

Roving histopathological imaging in navigation-confirmed tumor negative margin has not been achieved during neurosurgery procedures. This study aims to explore the diagnostic values of a novel intraoperative handheld endomicroscopy DiveScope (DS) for ex vivo glioma diagnosis and in vivo roving scan for navigation-confirmed glioma negative margin and evaluate its safety.

MATERIALS AND METHODS

This prospective pilot study was conducted at Huashan Hospital, Fudan University from October 2021 to October 2023, and enrolled patients scheduled for glioma resection surgery. The diagnostic values of DS scanning were compared with the frozen sections (FS). Hematoxylin-eosin (HE) staining was used as the gold standard for evaluation. The medical device adverse events (MDAE) were recorded for safety analysis.

RESULTS

The previous 24 patients with 73 intraoperative isolated samples were included in the DS ex vivo assessments for glioma diagnosis, and the subsequent 40 patients with 52 samples were included in the DS in vivo assessments for navigation-confirmed tumor negative margin. The sensitivity, specificity, and accuracy of DS scanning were 100.0%, 81.6%, and 90.4% for ex vivo assessment by a pathologist, 100.0%, 76.3%, and 87.7% for ex vivo assessment by a neurosurgeon, and 100.0%, 85.0%, and 94.2% for in vivo assessment, respectively. DS in vivo roving scan showed a significantly improved area under the receiver-operating characteristic curve (AUC) compared to FS in assessing the navigation-confirmed tumor negative margin (AUC: 0.925 vs. 0.725, P = 0.003). There were no MDAEs. Time taken for DS scanning for each sample was 75.77 ± 45.03 s and for each patient was 121.63 ± 94.04 s.

CONCLUSION

DiveScope could provide safe, time-effective, and accurate roving histological imaging for navigation-confirmed glioma negative margin during surgery, which may guide the glioma resection process to achieve maximum safe resection and promote prognosis.

Characterization of irradiated mucosa using confocal laser endomicroscopy in the upper aerodigestive tract

PURPOSE

Confocal laser endomicroscopy (CLE) enables a real time in-vivo optical biopsy of the upper aerodigestive tract. Previous studies demonstrated its potential in identifying malignant tissue, but none examined mucosa treated with radiotherapy. This study characterizes the appearance of irradiated mucosa using CLE.

METHODS

We recorded 58 CLE sequences (860 s, 6,884 frames) in 10 patients previously treated with radiotherapy for upper aerodigestive tract tumors. A corresponding tissue biopsy (formalin-fixed, H&E stained) was taken as the reference standard for each sequence. We analyzed each sequence regarding differences from normal mucosa and characterized irradiated mucosa in CLE.

RESULTS

Irradiated mucosa in CLE exhibits irregular tissue architecture. Radiation induces DNA damage, apoptosis, and tissue inflammation, leading to hyperkeratotic and fibrotic tissue. Consequently, CLE showed a wider range of cellular morphologic and tissue structural aberrancies, in comparison to normal, non-irradiated mucosa. In addition to regular honeycomb-like patterns, the tissue displayed uneven, blurry, and cell-rich areas. Irradiated mucosa appears more irregular and variable in CLE than radiation-naïve mucosa.

CONCLUSION

Irradiated mucosa can be differentiated from healthy tissue using CLE, but its higher baseline morphological variability may mimic malignancy. Further research is needed to clarify its impact on tumor detection and refine existing scoring systems.

Confocal Laser Endomicroscopy: Enhancing Intraoperative Decision Making in Neurosurgery

Brain tumors, both primary and metastatic, represent a significant global health burden due to their high incidence, mortality, and the severe neurological deficits they frequently cause. Gliomas, especially high-grade gliomas (HGGs), rank among the most aggressive and lethal neoplasms, with only modest gains in long-term survival despite extensive molecular research and established standard therapies. In neurosurgical practice, maximizing the extent of safe resection is a principal strategy for improving clinical outcomes. Yet, the infiltrative nature of gliomas often complicates the accurate delineation of tumor margins. Confocal laser endomicroscopy (CLE), originally introduced in gastroenterology, has recently gained prominence in neuro-oncology by enabling real-time, high-resolution cellular imaging during surgery. This technique allows for intraoperative tumor characterization and reduces dependence on time-consuming frozen-section analyses. Recent technological advances, including device miniaturization and second-generation CLE systems, have substantially improved image quality and diagnostic utility. Furthermore, integration with deep learning algorithms and telepathology platforms fosters automated image interpretation and remote expert consultations, thereby accelerating surgical decision making and enhancing diagnostic consistency. Future work should address remaining challenges, such as mitigating motion artifacts, refining training protocols, and broadening the range of applicable fluorescent probes, to solidify CLE's role as a critical intraoperative adjunct in neurosurgical oncology.

Intraoperative fluorescence redefining neurosurgical precision

Surgical resection is essential for treating solid tumors, with success largely dependent on the complete excision of neoplastic cells. However, neurosurgical procedures must delicately balance tumor removal with the preservation of surrounding tissue. Achieving clear margins is particularly challenging in cases like glioblastoma due to the limitations of traditional white light visualization. These limitations often result in incomplete resections, leading to frequent recurrences, or excessive resection that harms vital neural structures, causing iatrogenic nerve damage, which can lead to sensory and functional deficits. Current statistics reveal a 90% recurrence rate for malignant gliomas. Similarly, an 8% incidence of iatrogenic nerve trauma contributes to an estimated 25 million cases of peripheral nerve injury globally each year. These figures underscore the urgent need for improved intraoperative techniques for lesion margin and nerve identification and visualization. Recent advances in neurosurgical imaging, such as fluorescence-guided surgery (FGS), have begun to address these challenges. Fluorescent agents used in FGS illuminate target tissues, although not all do so selectively. Despite the promising results of agents such as 5-aminolevulinic acid and indocyanine green, their applications are mainly limited by issues of sensitivity and specificity. Furthermore, these agents do not effectively address the need for precise nerve visualization. Nerve Peptide 41, a novel systemically administered fluorescent nerve-targeted probe, shows promise in filling this gap. This review assesses the major fluorescent imaging modalities in neurosurgery, highlighting each of their benefits, limitations, and potential.

Clinical confocal laser endomicroscopy for imaging of autofluorescence signals of human brain tumors and non-tumor brain

PURPOSE

Analysis of autofluorescence holds promise for brain tumor delineation and diagnosis. Therefore, we investigated the potential of a commercial confocal laser scanning endomicroscopy (CLE) system for clinical imaging of brain tumors.

METHODS

A clinical CLE system with fiber probe and 488 nm laser excitation was used to acquire images of tissue autofluorescence. Fresh samples were obtained from routine surgeries (glioblastoma n = 6, meningioma n = 6, brain metastases n = 10, pituitary adenoma n = 2, non-tumor from surgery for the treatment of pharmacoresistant epilepsy n = 2). Additionally, in situ intraoperative label-free CLE was performed in three cases. The autofluorescence images were visually inspected for feature identification and quantification. For reference, tissue cryosections were prepared and further analyzed by label-free multiphoton microscopy and HE histology.

RESULTS

Label-free CLE enabled the acquisition of autofluorescence images for all cases. Autofluorescent structures were assigned to the cytoplasmic compartment of cells, elastin fibers, psammoma bodies and blood vessels by comparison to references. Sparse punctuated autofluorescence was identified in most images across all cases, while dense punctuated autofluorescence was most frequent in glioblastomas. Autofluorescent cells were observed in higher abundancies in images of non-tumor samples. Diffuse autofluorescence, fibers and round fluorescent structures were predominantly found in tumor tissues.

CONCLUSION

Label-free CLE imaging through an approved clinical device was able to visualize the characteristic autofluorescence patterns of human brain tumors and non-tumor brain tissue ex vivo and in situ. Therefore, this approach offers the possibility to obtain intraoperative diagnostic information before resection, importantly independent of any kind of marker or label.

Advancements in Neurosurgical Intraoperative Histology

Despite their relatively low incidence globally, central nervous system (CNS) tumors remain amongst the most lethal cancers, with only a few other malignancies surpassing them in 5-year mortality rates. Treatment decisions for brain tumors heavily rely on histopathological analysis, particularly intraoperatively, to guide surgical interventions and optimize patient outcomes. Frozen sectioning has emerged as a vital intraoperative technique, allowing for highly accurate, rapid analysis of tissue samples, although it poses challenges regarding interpretive errors and tissue distortion. Raman histology, based on Raman spectroscopy, has shown great promise in providing label-free, molecular information for accurate intraoperative diagnosis, aiding in tumor resection and the identification of neurodegenerative disease. Techniques including Stimulated Raman Scattering (SRS), Coherent Anti-Stokes Raman Scattering (CARS), Surface-Enhanced Raman Scattering (SERS), and Tip-Enhanced Raman Scattering (TERS) have profoundly enhanced the speed and resolution of Raman imaging. Similarly, Confocal Laser Endomicroscopy (CLE) allows for real-time imaging and the rapid intraoperative histologic evaluation of specimens. While CLE is primarily utilized in gastrointestinal procedures, its application in neurosurgery is promising, particularly in the context of gliomas and meningiomas. This review focuses on discussing the immense progress in intraoperative histology within neurosurgery and provides insight into the impact of these advancements on enhancing patient outcomes.

Fluorescein-guided surgery for high-grade glioma resection: a five-year-long retrospective study at our institute

Objective

This study investigates the extent of resection, duration of surgery, intraoperative blood loss, and postoperative complications in patients with high-grade glioma who received surgery with or without sodium fluorescein guidance.

Methods

A single-center retrospective cohort study was conducted on 112 patients who visited our department and underwent surgery between July 2017 and June 2022, with 61 in the fluorescein group and 51 in the non-fluorescein group. Baseline characteristics, intraoperative blood loss, surgery duration, resection extent, and postoperative complications were documented.

Results

The duration of surgery was significantly shorter in the fluorescein group than in the non-fluorescein group (P = 0.022), especially in patients with tumors in the occipital lobes (P = 0.013). More critically, the gross total resection (GTR) rate was significantly higher in the fluorescein group than in the non-fluorescein group (45.9% vs. 19.6%, P = 0.003). The postoperative residual tumor volume (PRTV) was also significantly lower in the fluorescein group than in the non-fluorescein group (0.40 [0.12-7.11] cm³ vs. 4.76 [0.44-11.00] cm³, P = 0.020). Particularly in patients with tumors located in the temporal and occipital lobes (temporal, GTR 47.1% vs. 8.3%, P = 0.026; PRTV 0.23 [0.12-8.97] cm³ vs. 8.35 [4.05-20.59] cm³, P = 0.027; occipital, GTR 75.0% vs. 0.0%, P = 0.005; PRTV 0.15 [0.13-1.50] cm³ vs. 6.58 [3.70-18.79] cm³, P = 0.005). However, the two groups had no significant difference in intraoperative blood loss (P = 0.407) or postoperative complications (P = 0.481).

Conclusions

Fluorescein-guided resection of high-grade gliomas using a special operating microscope is a feasible, safe, and convenient technique that significantly improves GTR rates and reduces postoperative residual tumor volume when compared to conventional white light surgery without fluorescein guidance. This technique is particularly advantageous for patients with tumors located in non-verbal, sensory, motor, and cognitive areas such as the temporal and occipital lobes, and does not increase the incidence of postoperative complications.

Maximal Safe Resection in Glioblastoma Surgery: A Systematic Review of Advanced Intraoperative Image-Guided Techniques

Glioblastoma multiforme (GBM) represents the most common and aggressive central nervous system tumor associated with a poor prognosis. The aim of this study was to depict the role of intraoperative imaging techniques in GBM surgery and how they can ensure the maximal extent of resection (EOR) while preserving the functional outcome. The authors conducted a systematic review following PRISMA guidelines on the PubMed/Medline and Scopus databases. A total of 1747 articles were identified for screening. Studies focusing on GBM-affected patients, and evaluations of EOR and functional outcomes with the aid of advanced image-guided techniques were included. The resulting studies were assessed for methodological quality using the Risk of Bias in Systematic Review tool. Open Science Framework registration DOI 10.17605/OSF.IO/3FDP9. Eighteen studies were eligible for this systematic review. Among the selected studies, eight analyzed Sodium Fluorescein, three analyzed 5-aminolevulinic acid, two evaluated IoMRI imaging, two evaluated IoUS, and three evaluated multiple intraoperative imaging techniques. A total of 1312 patients were assessed. Gross Total Resection was achieved in the 78.6% of the cases. Follow-up time ranged from 1 to 52 months. All studies assessed the functional outcome based on the Karnofsky Performance Status scale, while one used the Neurologic Assessment in Neuro-Oncology score. In 77.7% of the cases, the functional outcome improved or was stable over the pre-operative assessment. Combining multiple intraoperative imaging techniques could provide better results in GBM surgery than a single technique. However, despite good surgical outcomes, patients often present a neurocognitive decline leading to a marked deterioration of the quality of life. Advanced intraoperative image-guided techniques can allow a better understanding of the anatomo-functional relationships between the tumor and the surrounding brain, thus maximizing the EOR while preserving functional outcomes.

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.

Development, Implementation and Application of Confocal Laser Endomicroscopy in Brain, Head and Neck Surgery—A Review

When we talk about visualization methods in surgery, it is important to mention that the diagnosis of tumors and how we define tumor borders intraoperatively in a correct way are two main things that would not be possible to achieve without this grand variety of visualization methods we have at our disposal nowadays. In addition, histopathology also plays a very important role, and its importance cannot be neglected either. Some biopsy specimens, e.g., frozen sections, are examined by a histopathologist and lead to tumor diagnosis and the definition of its borders. Furthermore, surgical resection is a very important point when it comes to prognosis and life survival. Confocal laser endomicroscopy (CLE) is an imaging technique that provides microscopic information on the tissue in real time. CLE of disorders, such as head, neck and brain tumors, has only recently been suggested to contribute to both immediate tumor characterization and detection. It can be used as an additional tool for surgical biopsies during biopsy or surgical procedures and for inspection of resection margins during surgery. In this review, we analyze the development, implementation, advantages and disadvantages as well as the future directions of this technique in neurosurgical and otorhinolaryngological disciplines.

Novel intraoperative strategies for enhancing tumor control: Future directions

Maximal safe surgical resection plays a key role in the care of patients with gliomas. A range of technologies have been developed to aid surgeons in distinguishing tumor from normal tissue, with the goal of increasing tumor resection and limiting postoperative neurological deficits. Technologies that are currently being investigated to aid in improving tumor control include intraoperative imaging modalities, fluorescent tumor makers, intraoperative cell and molecular profiling of tumors, improved microscopic imaging, intraoperative mapping, augmented and virtual reality, intraoperative drug and radiation delivery, and ablative technologies. In this review, we summarize the aforementioned advancements in neurosurgical oncology and implications for improving patient outcomes.

Novel rapid intraoperative qualitative tumor detection by a residual convolutional neural network using label-free stimulated Raman scattering microscopy

Determining the presence of tumor in biopsies and the decision-making during resections is often dependent on intraoperative rapid frozen-section histopathology. Recently, stimulated Raman scattering microscopy has been introduced to rapidly generate digital hematoxylin-and-eosin-stained-like images (stimulated Raman histology) for intraoperative analysis. To enable intraoperative prediction of tumor presence, we aimed to develop a new deep residual convolutional neural network in an automated pipeline and tested its validity. In a monocentric prospective clinical study with 94 patients undergoing biopsy, brain or spinal tumor resection, Stimulated Raman histology images of intraoperative tissue samples were obtained using a fiber-laser-based stimulated Raman scattering microscope. A residual network was established and trained in ResNetV50 to predict three classes for each image: (1) tumor, (2) non-tumor, and (3) low-quality. The residual network was validated on images obtained in three small random areas within the tissue samples and were blindly independently reviewed by a neuropathologist as ground truth. 402 images derived from 132 tissue samples were analyzed representing the entire spectrum of neurooncological surgery. The automated workflow took in a mean of 240 s per case, and the residual network correctly classified tumor (305/326), non-tumorous tissue (49/67), and low-quality (6/9) images with an inter-rater agreement of 89.6% (κ = 0.671). An excellent internal consistency was found among the random areas with 90.2% (Cα = 0.942) accuracy. In conclusion, the novel stimulated Raman histology-based residual network can reliably detect the microscopic presence of tumor and differentiate from non-tumorous brain tissue in resection and biopsy samples within 4 min and may pave a promising way for an alternative rapid intraoperative histopathological decision-making tool.

OCT-Guided Surgery for Gliomas: Current Concept and Future Perspectives

Optical coherence tomography (OCT) has been recently suggested as a promising method to obtain in vivo and real-time high-resolution images of tissue structure in brain tumor surgery. This review focuses on the basics of OCT imaging, types of OCT images and currently suggested OCT scanner devices and the results of their application in neurosurgery. OCT can assist in achieving intraoperative precision identification of tumor infiltration within surrounding brain parenchyma by using qualitative or quantitative OCT image analysis of scanned tissue. OCT is able to identify tumorous tissue and blood vessels detection during stereotactic biopsy procedures. The combination of OCT with traditional imaging such as MRI, ultrasound and 5-ALA fluorescence has the potential to increase the safety and accuracy of the resection. OCT can improve the extent of resection by offering the direct visualization of tumor with cellular resolution when using microscopic OCT contact probes. The theranostic implementation of OCT as a part of intelligent optical diagnosis and automated lesion localization and ablation could achieve high precision, automation and intelligence in brain tumor surgery. We present this review for the increase of knowledge and formation of critical opinion in the field of OCT implementation in brain tumor surgery.

Socio-Organizational Impact of Confocal Laser Endomicroscopy in Neurosurgery and Neuropathology: Results from a Process Analysis and Expert Survey

During brain tumor resection surgery, it is essential to determine the tumor borders as the extent of resection is important for post-operative patient survival. The current process of removing a tissue sample for frozen section analysis has several shortcomings that might be overcome by confocal laser endomicroscopy (CLE). CLE is a promising new technology enabling the digital in vivo visualization of tissue structures in near real-time. Research on the socio-organizational impact of introducing this new methodology to routine care in neurosurgery and neuropathology is scarce. We analyzed a potential clinical workflow employing CLE by comparing it to the current process. Additionally, a small expert survey was conducted to collect data on the opinion of clinical staff working with CLE. While CLE can contribute to a workload reduction for neuropathologists and enable a shorter process and a more efficient use of resources, the effort for neurosurgeons and surgery assistants might increase. Experts agree that CLE offers huge potential for better diagnosis and therapy but also see challenges, especially due to the current state of experimental use, including a risk for misinterpretations and the need for special training. Future studies will show whether CLE can become part of routine care.