Analysis of Endoscope-Assisted Retrosigmoid Approach versus Modified Transjugular Approach for Microvascular Decompression of the Facial Nerve: A Comparative Cadaveric Study

Objective: Two main approaches for microvascular decompression for hemifacial spasm include the retrosigmoid approach (RA) and the modified transjugular-tubercular approach (MTA). This anatomical study compares both and evaluates the value of neuroendoscopy. Methods: Dissections were performed on 4 cadaveric human heads, performing RA on one side and MTA on the other. Anatomical landmarks were determined beforehand, and the accessibility to each was evaluated by determining visibility with a microscope and 0°, 30°, and 45° endoscopes. The degree of freedom at each landmark, representing the working area afforded by each approach, was measured using vectors from the boundaries of the craniotomy to the points of interest. Results: MTA yielded 90.1% greater degree of freedom (P < 0.00001) at the internal acoustic canal and 118.3% greater access (P < 0.001) to the facial nerve root exit zone than RA. For landmarks with sub-100% microscopic visualization, the 0° endoscope improved visualization for 15/16 (94%) landmarks with RA and 9/9 (100%) with MTA. Introducing 30° and 45° angled endoscopes improved visualization in every instance. Although MTA provided a higher visualization for some landmarks with the microscope and 0° endoscope, all discrepancies were eliminated with the 30° endoscope, while the 45° endoscope showed identical visualization. Conclusions: Despite the greater degree of freedom with MTA, visualizing and manipulating the facial nerve at the root exit zone was comparable between both approaches, with the use of angled endoscopy further improving visualization and accessibility. As such, the endoscope-assisted RA, with its smaller exposure and soft-tissue disruption, is a viable approach for microvascular decompression for hemifacial spasm.