The Current State of Visualization Techniques in Endoscopic Skull Base Surgery

Applicability of a Dexterity-Enhancing Handheld Robot for 360° Endoscopic Skull Base Approaches: An Exploratory Cadaver Study

BACKGROUND AND OBJECTIVES

Endoscopic skull base surgery aims to reduce surgical morbidity by minimizing tissue manipulation and exposure. However, the anatomic constraints posed by the narrow surgical corridors and constrained operative workspace present technical challenges due to reduced dexterity. This study evaluates the applicability of a novel dexterity-enhancing handheld robot for endoscopic skull base approaches.

METHODS

The robotic system is comprised of interchangeable articulated end-effectors coupled to a handheld controller. Two attending skull base neurosurgeons and 2 neurosurgery residents performed 8 skull base approaches on cadaveric specimens, spanning anterior, anterolateral, lateral, posterolateral, and posterior approaches. Conventional instruments were used to expose anatomic landmarks, followed by intraoperative tasks using the handheld robot. Participants were interviewed during the procedures to assess the robot's feasibility (ability to safely reach and perform its objective of manipulating tissue at the operative site) and usefulness (ability to perform desired objectives well).

RESULTS

The handheld robotic system was tested across 8 endoscopic skull base approaches, achieving feasibility in all cases. Superior workspace reach compared with standard instruments was demonstrated in 6 of 8 approaches. Tissue manipulation was satisfactory in all approaches. All surgeons reported that the current or a future device prototype could be useful across all 8 approaches. The most frequently cited advantage was the expanded dextrous workspace reach provided by the articulated end-effectors, particularly in approaches with long working channels, such as the endonasal approach. However, the robot encountered difficulties in transcranial approaches (trans-sylvian and subtemporal) due to the lack of shorter, curved shafts, which impaired visualization.

CONCLUSION

The handheld robotic system demonstrated applicability across various endoscopic skull base approaches, offering increased dextrous workspace and effective tissue manipulation capabilities. Overall, this study supports the potential of handheld robots in endoscopic skull base surgery while highlighting the need for iterative development to optimize instrument design and functionality.

Fully endoscopic microvascular decompression for hemifacial spasm: a systematic review

Hemifacial spasm (HFS) is a distressing condition caused by facial nerve compression and characterized by involuntary facial muscle twitching, adversely impacting quality of life. Microvascular decompression (MVD) is effective but poses risks. Fully endoscopic MVD (E-MVD) as an emerging technique offers enhanced safety and efficacy. Therefore, this systematic review aimed to evaluate the use of fully E-MVD in treating HFS. In accordance with PRISMA guidelines, the systematic review included a thorough literature search in PubMed/MEDLINE, Embase, and Cochrane Library. Eligible studies were evaluated based on predefined criteria, with duplicates eliminated and conflicts resolved by a senior author. Data extraction was performed independently by two authors, with disagreements resolved by the senior author. Details on study characteristics, demographics, intraoperative observations, postoperative complications, and efficacy of fully E-MVD for HFS were gathered. Quality assessment was conducted using the NIH tool. A total of 408 patients were included in the study, with females comprising 68% and males 32% of the cohort. The mean age of patients was 52.4 years, with an average symptom duration of 4.5 years. Right-sided and left-sided symptoms were reported in 54.4% and 46.6% of patients, respectively. Intraoperatively, the most common offending blood vessel was a single AICA (48.1%). Early postoperative complications were reported in 13.6% of patients, which primarily consisted of transient facial palsy (6.8%) and hearing impairment (4%). All cases of facial palsy resolved during the follow-up period, yet 1.3% of hearing impairments persisted. The efficacy of Fully E-MVD for HFS was promising, with 93.3% of patients experiencing effective resolution at follow-up. With advancements in surgical techniques and technology, fully E-MVD continues to show promising results in improving the quality of life for patients suffering from HFS. Favorable outcomes and symptom resolution support fully E-MVD's advantages. Surgeons must consider limitations and proper techniques for optimal patient outcomes.

Fluorescence guidance in skull base surgery: Applications and limitations - A systematic review

Introduction

Intraoperative fluorescence guidance is a well-established surgical adjunct in high-grade glioma surgery. In contrast, the clinical use of such dyes and technology has been scarcely reported in skull base surgery.

Research question

We aimed to systematically review the clinical applications of different fluorophores in both open and endonasal skull base surgery.

Material and methods

We performed a systematic review and discussed the current literature on fluorescence guidance in skull base surgery.

Results

After a comprehensive literature search, 77 articles on skull base fluorescence guidance were evaluated. A qualitative analysis of the articles is presented, discussing clinical indications and current controversies. The use of intrathecal fluorescein was the most frequently reported in the literature. Beyond that, 5-ALA and ICG were two other fluorescent dyes most extensively discussed, with some experimental fluorophore applications in skull base surgery.

Discussion and conclusion

Intraoperative fluorescence imaging can serve as an adjunct technology in skull base surgery. The scope of initial indications of these fluorophores has expanded beyond malignant glioma resection alone. We discuss current use and controversies and present an extensive overview of additional indications for fluorescence imaging in skull base pathologies. Further quantitative studies will be needed in the future, focusing on tissue selectivity and time-dependency of the different fluorophores currently commercially available, as well as the development of new compounds to expand applications and facilitate skull base surgeries.

Exoscopic Retrosigmoid Approach for an Anteromedial Tentorial Meningioma: 2D Operative Video

We present a 2-dimensional operative video (Video 1) of a suboccipital retrosigmoid approach for an anteromedial tentorial meningioma with a specific focus on the use of a surgical exoscope. The patient is a 50-year-old woman who presented to emergency room with a 6-month history of nausea, dizziness, and gait imbalance secondary to a 2.5-cm homogenously enhancing mass originating from the anteromedial tentorium on the right side with associated brainstem compression. Retrosigmoid craniotomy was selected due to the favorable surgical corridor for resection and lower risk of cerebrospinal fluid leak, hearing loss, and seizures compared with other approaches.1-5 The patient consented to the procedure. Video 1 emphasizes the advantages of the exoscope compared with the microscope in optimizing surgeon efficiency, ergonomics, and comfort.6 The unique operating room setup associated with exoscope use is highlighted. The patient underwent uncomplicated gross total resection with a mild trochlear nerve palsy noted postoperatively that was resolved at follow-up.7.

Single-Center Experience in Microsurgical Resection of Acoustic Neurinomas and the Benefit of Microscope-Based Augmented Reality

Background and Objectives: Microsurgical resection with intraoperative neuromonitoring is the gold standard for acoustic neurinomas (ANs) which are classified as T3 or T4 tumors according to the Hannover Classification. Microscope-based augmented reality (AR) can be beneficial in cerebellopontine angle and lateral skull base surgery, since these are small areas packed with anatomical structures and the use of this technology enables automatic 3D building of a model without the need for a surgeon to mentally perform this task of transferring 2D images seen on the microscope into imaginary 3D images, which then reduces the possibility of error and provides better orientation in the operative field. Materials and Methods: All patients who underwent surgery for resection of ANs in our department were included in this study. Clinical outcomes in terms of postoperative neurological deficits and complications were evaluated, as well as neuroradiological outcomes for tumor remnants and recurrence. Results: A total of 43 consecutive patients (25 female, median age 60.5 ± 16 years) who underwent resection of ANs via retrosigmoid osteoclastic craniotomy with the use of intraoperative neuromonitoring (22 right-sided, 14 giant tumors, 10 cystic, 7 with hydrocephalus) by a single surgeon were included in this study, with a median follow up of 41.2 ± 32.2 months. A total of 18 patients underwent subtotal resection, 1 patient partial resection and 24 patients gross total resection. A total of 27 patients underwent resection in sitting position and the rest in semi-sitting position. Out of 37 patients who had no facial nerve deficit prior to surgery, 19 patients were intact following surgery, 7 patients had House Brackmann (HB) Grade II paresis, 3 patients HB III, 7 patients HB IV and 1 patient HB V. Wound healing deficit with cerebrospinal fluid (CSF) leak occurred in 8 patients (18.6%). Operative time was 317.3 ± 99 min. One patient which had recurrence and one further patient with partial resection underwent radiotherapy following surgery. A total of 16 patients (37.2%) underwent resection using fiducial-based navigation and microscope-based AR, all in sitting position. Segmented objects of interest in AR were the sigmoid and transverse sinus, tumor outline, cranial nerves (CN) VII, VIII and V, petrous vein, cochlea and semicircular canals and brain stem. Operative time and clinical outcome did not differ between the AR and the non-AR group. However, use of AR improved orientation in the operative field for craniotomy planning and microsurgical resection by identification of important neurovascular structures. Conclusions: The single-center experience of resection of ANs showed a high rate of gross total (GTR) and subtotal resection (STR) with low recurrence. Use of AR improves intraoperative orientation and facilitates craniotomy planning and AN resection through early improved identification of important anatomical relations to structures of the inner auditory canal, venous sinuses, petrous vein, brain stem and the course of cranial nerves.

Towards navigation in endoscopic kidney surgery based on preoperative imaging

Endoscopic renal surgeries have high re-operation rates, particularly for lower volume surgeons. Due to the limited field and depth of view of current endoscopes, mentally mapping preoperative computed tomography (CT) images of patient anatomy to the surgical field is challenging. The inability to completely navigate the intrarenal collecting system leads to missed kidney stones and tumors, subsequently raising recurrence rates. A guidance system is proposed to estimate the endoscope positions within the CT to reduce re-operation rates. A Structure from Motion algorithm is used to reconstruct the kidney collecting system from the endoscope videos. In addition, the kidney collecting system is segmented from CT scans using 3D U-Net to create a 3D model. The two collecting system representations can then be registered to provide information on the relative endoscope position. Correct reconstruction and localization of intrarenal anatomy and endoscope position is demonstrated. Furthermore, a 3D map is created supported by the RGB endoscope images to reduce the burden of mental mapping during surgery. The proposed reconstruction pipeline has been validated for guidance. It can reduce the mental burden for surgeons and is a step towards the long-term goal of reducing re-operation rates in kidney stone surgery.

Operative Adjuncts in Pediatric Brain Tumor Surgery with a Focus on Suprasellar Tumors

The primary objective of surgery for brain tumor resection has always been maximizing safe resection while minimizing the risk to normal brain tissue. Technological advances applied in the operating room help surgeons to achieve this objective. This chapter discusses specific tools and approaches in the operating environment that target safe surgery for brain tumors in children, with a focus on pathologies in the sellar/suprasellar region. Particular focus is given to tools that help with safe patient positioning; intraoperative imaging modalities; and chemical visualization adjuncts. Both static (preoperative images used for neuronavigation) and dynamic (images updated during the procedure) intraoperative imaging modalities are discussed. There is further overview of operative rehearsal and preparation strategies, which are rapidly evolving as virtual reality systems become more commonplace. While the rapid evolution of intraoperative adjuncts in neurosurgery means the status of a given technology as novel is quite transient, this chapter offers a snapshot of the current state of advanced intraoperative tools for pediatric brain tumor surgery.

On-Device Execution of Deep Learning Models on HoloLens2 for Real-Time Augmented Reality Medical Applications

The integration of Deep Learning (DL) models with the HoloLens2 Augmented Reality (AR) headset has enormous potential for real-time AR medical applications. Currently, most applications execute the models on an external server that communicates with the headset via Wi-Fi. This client-server architecture introduces undesirable delays and lacks reliability for real-time applications. However, due to HoloLens2's limited computation capabilities, running the DL model directly on the device and achieving real-time performances is not trivial. Therefore, this study has two primary objectives: (i) to systematically evaluate two popular frameworks to execute DL models on HoloLens2-Unity Barracuda and Windows Machine Learning (WinML)-using the inference time as the primary evaluation metric; (ii) to provide benchmark values for state-of-the-art DL models that can be integrated in different medical applications (e.g., Yolo and Unet models). In this study, we executed DL models with various complexities and analyzed inference times ranging from a few milliseconds to seconds. Our results show that Unity Barracuda is significantly faster than WinML (p-value < 0.005). With our findings, we sought to provide practical guidance and reference values for future studies aiming to develop single, portable AR systems for real-time medical assistance.

Neuroendoscopy: How We Got Here

From its inception in ancient Egyptian rituals, neuroendoscopy always promised a minimally invasive route to the cerebrum. Early visionaries, however, hit the proverbial wall of technical development until the 20th century, when new technologies allowed for light to be transmitted across a tube for visualization of intracranial structures. Despite a hiccupping start, with surgical microscopy hampering initial excitement, the development and transformation of neuroendoscopy continued, and today it is a widespread and reliable surgical option for the treatment of numerous varied and complex pathologies.

Ergonomic Analysis of Otologic Surgery: Comparison of Endoscope and Microscope

OBJECTIVE

The comparative postural health of surgeons performing endoscopic and microscopic otologic surgeries has been a topic of active debate, with many nascent or anecdotal reports suggesting the latter encourages suboptimal ergonomics. Using inertial body sensors to measure joint angles, this study sought to objectively evaluate and compare the ergonomics of surgeons during endoscopic and microscopic otologic surgeries.

STUDY DESIGN

Prospective pilot trial.

SETTING

Large, multicenter, academic hospital system. Performed 21 otologic operations (10 endoscopic and 11 microscopic) in November 2020 and January 2021. All attendings were fellowship trained in otology/neurotology.

SUBJECTS

Eight otolaryngologists (four attendings and four residents) performing 21 otologic surgeries (11 microscopic and 10 endoscopic).

INTERVENTION

Approach to otologic surgery: endoscope or microscope.

MAIN OUTCOME MEASURES

Surgeons' neck and back angles while wearing ergonomic sensors affixed to either side of each major joint, mental and physical burdens and pain after each surgery (via modified NASA Task Load Index).

RESULTS

Residents' necks (9.54° microscopic vs. -4.79° endoscopic, p = 0.04) and backs (16.48° microscopic vs. 3.66° endoscopic, p = 0.01) were significantly more flexed when performing microscopic surgery than when performing endoscopic surgery, although attending neck and back flexion were comparable during microscopic and endoscopic surgeries. Attendings reported significantly higher pain levels after operating microscopically than after operating endoscopically (0.13 vs. 2.76, p = 0.01).

CONCLUSIONS

Residents were found to operate with significantly higher risk back and neck postures (as defined by the validated ergonomic tool, Rapid Entire Body Assessment) when operating microscopically. Attendings reported significantly higher levels of pain after operating microscopically versus endoscopically, suggesting that the suboptimal microscopic postures adopted earlier in training may pose an indelible risk later in a surgeon's career.

History, Current Techniques, and Future Prospects of Surgery to the Sellar and Parasellar Region

The sellar and parasellar region can be affected by diverse pathologies. The deep-seated location and surrounding critical neurovascular structures make treatment challenging; there is no singular, optimal approach for management. The history and development of transcranial and transsphenoidal approaches by pioneers in skull base surgery were largely aimed at treating pituitary adenomas, which are the most common lesions of the sella. This review explores the history of sellar surgery, the most commonly used approaches today, and future considerations for surgery of the sellar/parasellar region.