Use of a Compact High-Definition Two-Dimensional Exoscope in Surgical Treatment of Large Vestibular Schwannoma

Use of a Compact High-Definition Two-Dimensional Exoscope in Surgical Treatment of Large Vestibular Schwannoma

Vestibular schwannoma (VS) is a benign tumor that accounts for 8% of all intracranial tumors and 85% of cerebellopontine angle tumors. Large and symptomatic VSs often require surgical resection, with the primary goal being the removal of the tumor mass while preserving facial and cochlear nerve function. Traditional surgical techniques rely on a binocular surgical microscope, which offers high magnification, three-dimensional (3D) visualization, and deep illumination. However, the surgical microscope has several limitations, including a shallow depth of field, frequent field adjustments, and ergonomic challenges for surgeons. The compact high-definition (HD) two-dimensional (2D) exoscope has emerged as a potential alternative, offering longer focal length, deeper depth of field, and improved ergonomics. This study evaluates the efficacy and safety of using a 2D exoscope in the surgical removal of large VSs compared to a traditional surgical microscope.

Background and Rationale

VSs are typically managed surgically when they are large or symptomatic. The traditional surgical microscope has been the standard tool for such procedures, providing the necessary magnification and illumination for precise microsurgical techniques. However, the microscope’s limitations, such as its bulky size, frequent need for field adjustments, and ergonomic discomfort for surgeons, have prompted the exploration of alternative visualization tools. The 2D exoscope, with its compact design and HD video capabilities, offers a promising solution. This study aims to compare the clinical outcomes, surgical efficiency, and surgeon comfort between the 2D exoscope and the traditional surgical microscope in the resection of large VSs.

Methods

This prospective cohort study was conducted at Tianjin Medical University General Hospital between January 2013 and June 2018. Patients with Koos grade 3 and grade 4 VSs were enrolled and randomly assigned to either the exoscope group (n = 39) or the surgical microscope group (n = 42). The inclusion criteria included age between 18 and 70 years, while exclusion criteria included Koos grade 1 and grade 2 VSs, neurofibromatosis type 2, bilateral VSs, prior surgery or radiation for VS, pregnancy, and participation in other clinical trials within the past 30 days.

All patients underwent a standardized diagnostic workup, including physical examination, audiometry, and radiographic imaging. Tumor characteristics, such as size, Koos grade, and composition (cystic or solid), were recorded. Surgical procedures were performed via the retrosigmoid approach under either the 2D exoscope or the surgical microscope. The exoscope system used was the ViTOM (Video Telescope Operating Microscopy) by Karl Storz GmbH, which included a 90° telescope, a full-HD camera, and two 26-inch video monitors for the primary and assistant surgeons. The surgical microscopes used were the Leica M525 OH4 and Carl Zeiss OPMI PENTERO 900.

Outcome measures included duration of surgery, volume of blood loss, extent of tumor resection, number of field adjustments, pre- and post-operative facial and cochlear nerve function, complications, and surgeon comfort. Facial nerve function was evaluated using the House-Brackmann grading scale, and hearing ability was assessed according to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines. Surgeon comfort was scored on a scale from 0 (comfortable) to 2 (uncomfortable).

Results

The study included 81 patients, with 39 in the exoscope group and 42 in the surgical microscope group. The two groups were comparable in terms of demographic and tumor characteristics, including age, sex, tumor side, size, Koos grade, and composition. There were no significant differences in the duration of surgery, extent of tumor resection, or post-operative facial and cochlear nerve function between the two groups.

However, patients in the exoscope group had significantly less blood loss (190.8 ± 83.4 mL) compared to the surgical microscope group (230.0 ± 82.3 mL, P = 0.036). Additionally, the exoscope group required fewer field adjustments (3.4 ± 0.7) than the surgical microscope group (10.3 ± 0.9, P < 0.001). Surgeons reported higher levels of comfort when using the exoscope, with 71.8% of primary surgeons and 94.9% of assistant surgeons reporting good comfort levels, compared to 35.7% and 54.8%, respectively, in the surgical microscope group (P = 0.001 and P < 0.001).

Discussion

The findings of this study demonstrate that the 2D exoscope is a safe and effective alternative to the traditional surgical microscope for the resection of large VSs. The exoscope system provided comparable surgical outcomes in terms of operative time, extent of tumor resection, and post-operative nerve function, while offering additional benefits such as reduced blood loss and fewer field adjustments. The ergonomic advantages of the exoscope, including the ability for surgeons to maintain a neutral posture and the shared visual field for the entire surgical team, contributed to the higher levels of reported comfort.

The reduced blood loss observed in the exoscope group may be attributed to the deeper depth of field and wider field of view provided by the exoscope, which allows for more precise dissection and reduced need for field adjustments. The fewer field adjustments required with the exoscope also likely contributed to the shorter operative times and reduced blood loss. The improved ergonomics of the exoscope system, which allows surgeons to operate in a more natural and comfortable position, may also have played a role in the reduced blood loss and improved surgical outcomes.

The study’s findings are consistent with previous reports on the use of exoscopes in other neurosurgical procedures, such as spine surgery, intracranial hematoma evacuation, and glioma resection. The exoscope’s ability to provide high-resolution, magnified images on a video monitor, combined with its compact design and ergonomic advantages, makes it a valuable tool for high-precision neurosurgical procedures. The shared visual field provided by the exoscope also enhances its utility as a training tool, allowing surgical assistants and trainees to have the same view as the primary surgeon.

Limitations

While this study provides valuable insights into the use of the 2D exoscope in the resection of large VSs, it has several limitations. The study was conducted at a single institution, and the results may not be generalizable to other settings. Additionally, the study did not compare the 2D exoscope to a 3D exoscope, which may offer additional advantages in terms of depth perception. Further studies are needed to evaluate the use of the exoscope in other complex neurosurgical procedures and to compare the 2D and 3D exoscope systems.

Conclusion

The compact HD 2D exoscope system is a safe and effective alternative to the traditional surgical microscope for the resection of large VSs. The exoscope system offers several advantages, including reduced blood loss, fewer field adjustments, and improved surgeon comfort, without compromising surgical outcomes. The ergonomic benefits of the exoscope, combined with its high-resolution visualization and shared visual field, make it a valuable tool for high-precision neurosurgical procedures. Further studies are needed to explore the use of the exoscope in other neurosurgical applications and to compare the 2D and 3D exoscope systems.

doi.org/10.1097/CM9.0000000000000818

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