Fully endoscopic supraorbital keyhole approach to the anterior cranial base: A cadaveric study

Supraorbital keyhole approach: Pure endoscopic and endoscope-assisted perspective

OBJECTIVE

To assess the assumed advantages of pure endoscopic and endoscope-assisted methods for the supraorbital keyhole approach. The aim is to demonstrate visibility and accessibility of the pure endoscope approach as a possible standard approach for the supraorbital keyhole approach.

PATIENTS AND METHODS

We performed eight dissections on four cadaver heads using an operating microscope, an endoscope, and neuronavigation. The visibility and accessibility of the anterior and middle cranial fossae regions were compared for each. Special structures were defined to assess their preservation in both approaches. We used pure endoscopy on the eight sides and with a microscope on those same eight sides. Accessibility was quantified for key structures using linear measurements taken with the navigation system. In addition, we present clinical cases in which an endoscope-assisted supraorbital approach was employed.

RESULTS

Our measurements have been reported for each side in the formalin-fixed heads as the mean ± SD (in mm) from the bone margin to selected regions. Moreover, image analysis was performed using ImageJ software to compare selected surface area measurements between the endoscope and microscope images on each side for all cadaveric available specimens. There were no significant statistical differences between visualization of the selected areas. This means that by visual analysis both endoscopic and microscopic images can provide the surgeon nearly the same visibility and accessibility of a selected region.

CONCLUSION

A pure endoscopic method can be used to conduct the supraorbital keyhole approach when the endoscope is used as a primary tool. Our recommendation is to use the measurements described in this study for preoperative planning of the keyhole approach. We believe that with advances in neuro-endoscope technology, and instrumentations, the endoscopic approach may replace the microscopic approach in the near future.

Indigenous Inexpensive Practice Models for Skill Development in Neuroendoscopy

Introduction:

Neurosurgery is a branch having a tough learning curve. Residents generally get very less hands-on exposure for advanced procedures like neuroendoscopy. With the limited number of cadavers available and ethical issues associated with animal models, practice models, and simulators are becoming the able alternative. Most of these simulators are very costly. We tried to build indigenous inexpensive practice models that can help in developing most of the skills of neuroendoscopy.

Materials and Methods:

Models were built for learning hand-eye coordination, dexterity, instrument manipulation, cutting, fine dissection, keyhole concept, drilling, and simulation of laminectomy and ligamentum flavum resection. These were shown in the neuroendoscopic fellowship program conducted in authors' institute, and trainees' responses were recorded.

Results:

Both novice and experienced neuroendoscopic surgeons validated the models. There was no significant difference between their responses (P = 0.791).

Conclusion:

Indigenous innovative models can be used to learn and teach neuroendoscopic skills. The presented models were reliable, valid, eco-friendly, highly cost-effective, portable, easily made and can be kept in one's chamber for practicing.

A Side Door to Meckel's Cave: Anatomic Feasibility Study for the Lateral Transorbital Approach

BACKGROUND: In the last decade, endoscopic skull base surgery has significantly developed and generated a plethora of techniques and approaches for access to the cranial ventral floor. However, the exploration for the least-aggressive, maximally efficient approach continues.

OBJECTIVE: To describe in detail an anatomical study, along with the technical nuances of a novel endoscopic approach to Meckel's Cave (MC) using a lateral transorbital (LTO) route.

METHODS: Eighteen orbits of injected cadaveric specimens were operated on, using an endoscopic LTO approach to MC, middle cranial fossa, and paramedian skull base preserving the orbital rim. Surgical navigation and an after-the-fact infratemporal craniectomy were utilized to identify the limits of the approach.

RESULTS: Following a transorbital approach opening a trapezoid window at the superolateral aspect (average 166.7 mm2), a middle fossa “peeling” and full visualization of MC was accomplished with no difficulties in all specimens. The entire approach was performed extradurally without the need to expose the temporal lobe.

CONCLUSION: In a cadaveric model, the endoscopic LTO approach affords a direct route to access MC. Its main advantage is that it is minimally disruptive in nature, less brain retraction is required, and it reaches the middle fossa in an anterolateral perspective. It also requires no manipulation of the temporalis muscle, limited cosmetic incision, and rapid recovery. It seems a viable alternative to traditional approaches for lesions lateral to the cranial nerves at the cavernous sinus and MC, that is, schwannomas. Clinical utilization of this approach will challenge its efficacy and identify limitations.