Three-Dimensional Exoscopic Versus Microscopic Resection of Vestibular Schwannomas: A Comparative Series

Selective Microsurgical Disconnection of Greater Sphenoid Wing Dural Arteriovenous Fistula Through the Subtemporal Approach Under Exoscope Magnification

OBJECTIVE

Sphenoid dural arteriovenous fistulas located on the greater sphenoid wing carry a notable risk of intracranial hemorrhage due to the frequent presence of cortical venous reflux. Because of the challenging embolization procedure, microsurgery remains a valuable option in these cases.

METHODS

In most cases, the fistula is located in the anterolateral endocranial surface of the middle cranial fossa just below the sphenoid ridge; however, in a small subset of cases, the fistula is positioned posteriorly and medially in the region between the foramen ovale and rotundum. The former region can be reached using various frontolateral approaches, whereas the latter region can be accessed through a subtemporal trajectory, minimizing temporal lobe retraction. The exoscope has been gaining popularity for improved magnification, visualization, and surgeon ergonomics expanding the surgeon's possible trajectory in skull base surgery.

RESULTS

We present a targeted subtemporal approach using the exoscope for selective occlusion of an unruptured greater sphenoid wing dural arteriovenous fistula. With proper brain relaxation, a small temporobasal craniotomy opens a direct corridor to the middle cranial fossa. Exoscope-assisted surgery could improve dissection of the middle cranial base and dynamic temporal lobe retraction and expand the range of anteromedial subtemporal trajectories, providing angles that may be challenging to achieve using the operative microscope, as well as improve the surgeon's ergonomic position.

CONCLUSIONS

An exoscopic-assisted subtemporal approach is a feasible, safe, and minimally invasive approach to treat unruptured greater sphenoid wing dural arteriovenous fistulas and could be considered an alternative to endovascular treatment.

Digital 3D exoscope is an effective tool for the surgery of falx and parasagittal meningiomas

PURPOSE

Digital 3D exoscopes are promising tools for microneurosurgery. The results of exoscope-assisted resection of intracranial meningiomas have only been addressed in few case reports. We retrospectively compared the results of exoscope and microscope-assisted surgery of falx and parasagittal meningiomas.

METHODS

We included all consecutive adult patients (n = 36) with falx or parasagittal meningioma who were operated with curative intention during an 8-year period by one senior neurosurgeon. The operations were performed either with a surgical microscope (n = 16; Zeiss Kinevo or Pentero 900) or a digital 3D exoscope (n = 20, Aesculap Aeos). We reviewed the pre- and postoperative radiological images, clinical examinations and surgical reports to assess clinical outcomes and complications. We also analyzed surgical videos.

RESULTS

Gross-total resection (Simpson grade I-II) was achieved in approximately 90% of the patients in both groups (89% in exoscope and 92% in microscope group). The duration of the operation was slightly longer (117 vs. 88 min) in the exoscope group. Surgical outcomes were comparable, despite there being larger tumors (median diameter 53 vs. 38 mm) with higher grades (WHO Grade 2-3: 45% vs. 19%) in the exoscope group. Transient postoperative complications were more frequent in the exoscope group (40 vs. 25%) mainly related to the larger tumor size.

CONCLUSION

The digital 3D exoscope is an effective tool for performing surgery on falx and parasagittal meningiomas. The extent of removal, clinical results and complications seem to be comparable to surgical microscope even in large tumors. Larger prospective studies are required to confirm this result.

3D exoscopic versus microscopic superficial temporal artery to middle cerebral artery bypass surgery for moyamoya disease - a comparative series

PURPOSE

Superficial temporal artery to middle cerebral artery (STA-MCA) direct bypass surgery is the most common surgical procedure to treat moyamoya disease (MMD). Here, we aim to compare the performance of the 3D exoscope in bypass surgery with the gold standard operative microscope.

METHODS

All direct STA-MCA bypass procedures performed at a single university hospital for MMD between 2015 and 2023 were considered for inclusion. Data were retrospectively collected from patient files and surgical video material. From 2020 onwards, bypass procedures were exclusively performed using a digital three-dimensional exoscope as visualization device. Results were compared with a microsurgical bypass control group (2015-2019). The primary endpoint was defined as total duration of surgery, duration of completing the vascular anastomosis (ischemia time), bypass patency, number of stiches to perform the anastomosis, added stiches after leakage testing of the anastomosis and the Glasgow outcome scale (GOS) at last follow-up as secondary outcome parameter.

RESULTS

A total of 16 consecutive moyamoya patients underwent 21 STA-MCA bypass procedures. Thereof, six patients were operated using a microscope and ten patients using an exoscope (ORBEYE® n = 1; AEOS® n = 9). Total duration of surgery was comparable between devices (microscope: 313 min. ± 116 vs. exoscope: 279 min. ± 42; p = 0.647). Ischemia time also proved similar between groups (microscope: 43 min. ± 19 vs. exoscope: 41 min. ± 7; p = 0.701). No differences were noted in bypass patency rates. The number of stiches per anastomosis was similar between visualization devices (microscope: 17 ± 4 vs. exoscope: 17 ± 2; p = 0.887). In contrast, more additional stiches were needed in microscopic anastomoses after leakage testing the bypass (p = 0.035).

CONCLUSION

Taking into account the small sample size, end-to-side bypass surgery for moyamoya disease using a foot switch-operated 3D exoscope was not associated with more complications and led to comparable clinical and radiological results as microscopic bypass surgery.

A multi-institutional machine learning algorithm for prognosticating facial nerve injury following microsurgical resection of vestibular schwannoma

Vestibular schwannomas (VS) are the most common tumor of the skull base with available treatment options that carry a risk of iatrogenic injury to the facial nerve, which can significantly impact patients' quality of life. As facial nerve outcomes remain challenging to prognosticate, we endeavored to utilize machine learning to decipher predictive factors relevant to facial nerve outcomes following microsurgical resection of VS. A database of patient-, tumor- and surgery-specific features was constructed via retrospective chart review of 242 consecutive patients who underwent microsurgical resection of VS over a 7-year study period. This database was then used to train non-linear supervised machine learning classifiers to predict facial nerve preservation, defined as House-Brackmann (HB) I vs. facial nerve injury, defined as HB II-VI, as determined at 6-month outpatient follow-up. A random forest algorithm demonstrated 90.5% accuracy, 90% sensitivity and 90% specificity in facial nerve injury prognostication. A random variable (rv) was generated by randomly sampling a Gaussian distribution and used as a benchmark to compare the predictiveness of other features. This analysis revealed age, body mass index (BMI), case length and the tumor dimension representing tumor growth towards the brainstem as prognosticators of facial nerve injury. When validated via prospective assessment of facial nerve injury risk, this model demonstrated 84% accuracy. Here, we describe the development of a machine learning algorithm to predict the likelihood of facial nerve injury following microsurgical resection of VS. In addition to serving as a clinically applicable tool, this highlights the potential of machine learning to reveal non-linear relationships between variables which may have clinical value in prognostication of outcomes for high-risk surgical procedures.

Digital 3D Exoscope is Safe and Effective in Surgery for Intradural Extramedullary Tumors: A Comparative Series

BACKGROUND

Digital 3D exoscopes have been shown to be comparably safe and effective as surgical microscopes in complex microneurosurgical procedures. However, the results of exoscopic spinal tumor surgeries are scarce. The purpose of this study is to compare results of a transition from microscope to exoscope in surgeries for spinal intradural extramedullary tumors.

METHODS

We included all consecutive patients with intradural extramedullary spinal tumors operated on by the senior author during January 2016 to October 2023. The 3D exoscope was used in the latter half of the series from November 2020. We evaluated pre- and postoperative clinical findings, imaging studies, intra- and postoperative events, and analyzed surgical videos from the operations retrospectively.

RESULTS

We operated 35 patients (exoscope n = 19, microscope n = 16) for intradural extramedullary tumors (meningioma n = 18, schwannoma n = 12, other n = 5). Tumors in the cervical and thoracic spine were more common than in the lumbar region. The duration of surgery was slightly longer (median 220 vs. 185 minutes) in the exoscope group. However, the rate of gross total resection of the tumor was higher (81% vs. 67%) and the tumors more often located anteriorly to the spinal cord (42% vs. 13%) in the exoscope group. No major complications (i.e., permanent motor deficit or postoperative hematoma) occurred in either group. We saw postoperative gait improvement in 81% and 85% of the patients with preoperative deterioration of gait after exoscopic and microscopic surgeries, respectively.

CONCLUSIONS

This study demonstrates that exoscope-assisted surgery for spinal intradural extramedullary tumors is comparable in safety and effectiveness to traditional microscopic surgery.

Even short-term training improves the skills of novice exoscope users: a prospective laboratory experiment

BACKGROUND

The surgical 3D exoscopes have recently been introduced as an alternative to the surgical microscopes in microneurosurgery. Since the exoscope availability is still limited, it is relevant to know whether even a short-term exoscope training develops the skills needed for performing exoscope-assisted surgeries.

METHODS

Ten participants (six consultants, four residents) performed two laboratory bypass test tasks with a 3D exoscope (Aesculap Aeos®). Six training sessions (6 h) were performed in between (interval of 2-5 weeks) on artificial models. The participants were divided into two groups: test group (n = 6) trained with the exoscope and control group (n = 4) with a surgical microscope. The test task was an artificial end-to-side microsurgical anastomosis model, using 12 interrupted 9-0 sutures and recorded on video. We compared the individual as well as group performance among the test subjects based on suturing time, anastomosis quality, and manual dexterity.

RESULTS

Altogether, 20 bypass tasks were performed (baseline n = 10, follow-up n = 10). The median duration decreased by 28 min and 44% in the exoscope training group. The decrease was steeper (29 min, 45%) among the participants with less than 6 years of microneurosurgery experience compared to the more experienced participants (13 min, 24%). After training, the participants with at least 1-year experience of using the exoscope did not improve their task duration. The training with the exoscope led to a greater time reduction than the training with the microscope (44% vs 17%).

CONCLUSIONS

Even short-term training with the exoscope led to marked improvements in exoscope-assisted bypass suturing among novice microneurosurgeons. For the more experienced participants, a plateau in the initial learning curve was reached quickly. A much longer-term effort might be needed to witness further improvement in this user group.

High-Definition 3D Exoscope in Pediatric Otorhinolaryngology: A Systematic Literature Review

This PRISMA-compliant systematic review aimed to investigate the use of and the most common procedures performed with the novel 3D 4K exoscope in surgical pediatric head and neck settings.

METHODS

Search criteria were applied to PubMed, EMBASE and the Cochrane Review databases and included all studies published up to January 2023 reporting 3D 4K exoscope-assisted surgeries in pediatric patients. After the removal of duplicates, selection of abstracts and full-text articles, and quality assessment, we reviewed eligible articles for number of patients treated, age, surgical procedures, and outcomes.

RESULTS

Among 54 potentially relevant records, 5 studies were considered eligible and included in this systematic review, with reported treatment data for 182 patients. The surgical procedures belong to the otologic field (121 cases), head and neck surgery (25 cases) and transoral surgery (36 cases). Exoscopy allowed high quality visualization of anatomical structures during cochlear implantation and during reconstruction in head and neck surgery; moreover, it improved the surgical view of surgeons, spectators and ENT students.

CONCLUSIONS

The use of 3D 4K exoscopy has shown promising potential as a valuable tool in pediatric ORL-head and neck surgery; nevertheless, further validation of these encouraging outcomes is necessary through larger-scale studies specifically focused on pediatric patients.

Intraoperative Imaging and Optical Visualization Techniques for Brain Tumor Resection: A Narrative Review

Advancements in intraoperative visualization and imaging techniques are increasingly central to the success and safety of brain tumor surgery, leading to transformative improvements in patient outcomes. This comprehensive review intricately describes the evolution of conventional and emerging technologies for intraoperative imaging, encompassing the surgical microscope, exoscope, Raman spectroscopy, confocal microscopy, fluorescence-guided surgery, intraoperative ultrasound, magnetic resonance imaging, and computed tomography. We detail how each of these imaging modalities contributes uniquely to the precision, safety, and efficacy of neurosurgical procedures. Despite their substantial benefits, these technologies share common challenges, including difficulties in image interpretation and steep learning curves. Looking forward, innovations in this field are poised to incorporate artificial intelligence, integrated multimodal imaging approaches, and augmented and virtual reality technologies. This rapidly evolving landscape represents fertile ground for future research and technological development, aiming to further elevate surgical precision, safety, and, most critically, patient outcomes in the management of brain tumors.

Taming the exoscope: a one-year prospective laboratory training study

PURPOSE

Digital 3D exoscopes have been recently introduced as an alternative to a surgical microscope in microneurosurgery. We designed a laboratory training program to facilitate and measure the transition from microscope to exoscope. Our aim was to observe the effect of a one-year active training on microsurgical skills with the exoscope by repeating a standardized test task at several time points during the training program.

METHODS

Two board-certified neurosurgeons with no previous exoscope experience performed the same test tasks in February, July, and November during a 12-month period. In between the test tasks, both participants worked with the exoscope in the laboratory and assisted during clinical surgeries on daily basis. Each of the test segments consisted of repeating the same task 10 times during one week. Altogether, 60 test tasks were performed, 30 each. The test task consisted of dissecting and harvesting the ulnar and radial arteries of the second segment of a chicken wing using an exoscope (Aesculap AEOS). Each dissection was recorded on video and analyzed by two independent evaluators. We measured the time required to complete the task as well as several metrics for evaluating the manual skills of the dissection and handling of the exoscope system.

RESULT

There was a clear reduction in dissection time between the first and the last session, mean 34 min (SD 5.96) vs. 26 min (SD 8.69), respectively. At the end of the training, both neurosurgeons used the exoscope more efficiently utilizing more available options of the device. There was correlation between the dissection time and several of the factors we used for evaluating the work flow: staying in focus, zoom control, reduction of unnecessary movements or repetitive manual motions, manipulation technique of the vessel under dissection, handling of the instruments, and using them for multiple dissection purposes (stretching, cutting, and splitting).

CONCLUSION

Continuous, dedicated long-term training program is effective for microsurgical skill development when switching from a microscope to an exoscope. With practice, the micromotor movements become more efficient and the use of microinstruments more versatile.

3D Exoscopes in Experimental Microanastomosis: A Comparison of Different Systems

Background: In recent years, three-dimensional exoscopes have been increasingly applied in neurosurgery. Multiple exoscopic systems are available, all offering specific features. In this study, we assessed practical and visualization performance of four different exoscopic systems in a highly challenging microsurgical procedure, and evaluated whether these affected the quality of work. Methods: We included four different exoscopes: Olympus ORBEYE, Zeiss KINEVO, Storz VITOM, and Aesculap AEOS. With each exoscope, ten experimental bypass procedures were carried out on chicken wing vessels at a depth of 3 cm. We evaluated the quality of the anastomoses, the practical considerations for the setup of the exoscopic systems, and the visualization quality by tracking the number of unnecessary movements. Results: All included exoscopes enabled us to perform the bypass procedures with mostly adequate or excellent results. Surgically, the most pronounced difference between the exoscopes was the duration of the procedure, which was mainly due to the number of unnecessary movements. Practically, the exoscopes differ highly which is important when considering which exoscope to apply. Conclusions: This is the first study comparing different exoscope systems while performing the same challenging microsurgical procedure. We found major practical differences between the exoscopes that determine the suitability of an exoscope based on the demands and conditions of the surgical procedure. Therefore, preprocedural practical training with the exoscope is required.