2025 Proffered Presentations
S259: ANALYSIS OF ENDOSCOPE-ASSISTED RETROSIGMOID APPROACH VERSUS MODIFIED TRANSJUGULAR APPROACH FOR MICROVASCULAR DECOMPRESSION OF THE FACIAL NERVE, A COMPARATIVE CADAVERIC STUDY
Felipe Sfeir, MD1; Mehrdad Pahlevani, MD1; Fan Zhao, MD1; Kayla Lanker1; Alex Corlin, BA1; Regin Jay Mallari, BS1; Gregory Lekovic, MD2; Garni Bakhoudarian, MD1; 1Pacific Neuroscience Institute; 2UCLA
Introduction: There are multiple approaches to perform microvascular decompression (MVD) of the facial nerve. Two main approaches include the retrosigmoid approach and the modified transjugular approach. This anatomical study compares both approaches and evaluates the value of neuroendoscopy for this operation.
Methods: Anatomical dissections were performed on 4 cadaveric human heads (8 sides), performing a retrosigmoid approach on one side and a trans-jugular-tubercular approach for the other side. A list of anatomical landmarks was determined prior to performing the dissections, and the access to each landmark was evaluated once the dissections were completed. Accessibility was evaluated in terms of whether the landmark was visible with a microscope, 0° endoscope, 30° angled endoscope, and 45° angled endoscope. Accessibility data of each landmark was collected and converted into percentages for each approach and visualization tool. In addition to assessing the visual accessibility of each landmark, a quantitative neuronavigation system was utilized to compare the degree of freedom at each landmark as a representation of the working area afforded by each approach -- as measured by vectors from the boundaries of the craniotomy to the points of interest.
Results: The transtubercular approach yielded 90.1% greater access in the mean degree of freedom at the IAC, than the retrosigmoid approach (P < 0.00001). The transtubercular approach also yielded 118.3% greater access to the facial nerve root exit zone than the retrosigmoid approach (P < 0.001). Of all landmarks with sub-100% microscopic visualization, use of a 0° angled endoscope improved visualization for 15/16 (94%) landmarks in the retrosigmoid approach and 9/9 (100%) landmarks in the trans-tubercular approach, relative to the microscopic visualization. Of all landmarks with sub-100% microscopic visualization, use of the 30° angled endoscope and 45° angled endoscope improved visualization relative to the microscopic visualization percentage in every instance. Although the trans-tubercular approach provided a higher percentage visualization for some landmarks with the microscope and 0° angled endoscope, all discrepancies were eliminated upon implementation of the 30° angled endoscope. The 45° angled endoscope also showed identical visualization percentages between approaches.
Conclusion: Despite the larger craniotomy with a trans-jugular tubercular approach and the increased degree of freedom, the ability to visualize and manipulate the facial nerve at the root exit zone was comparable between both approaches, with the use of angled endoscopy improving visualization and accessibility for relevant landmarks. As such, the endoscope-assisted retrosigmoid approach, with its smaller exposure and soft tissue disruption, is a viable approach to MVD for hemifacial spasm.