Quantitative Cadaveric Comparison of Exposure in Standard Retrosigmoid Suboccipital Craniotomy (RSSO) Approach versus Extended RSSO Approach for Access to Petroclival Region

Introduction: The retrosigmoid suboccipital (RSSO) approach is widely used for accessing lesions in the cerebellopontine angle and petroclival region. While the standard RSSO provides excellent exposure to lateral posterior fossa structures, the extended RSSO that involves mobilization of transverse and sigmoid sinus has been developed to improve access to the ventral brainstem and petroclival area. This study aims to quantitatively compare these approaches to guide surgical decision-making for skull base tumors in petroclival region.

Objective: This article aims to quantitatively compare the surgical exposure and maneuverability provided by the standard RSSO approach versus the extended RSSO approach for accessing the petroclival region.

Methods: We used four latex-injected fresh cadaveric head specimens (eight sides). Standard RSSO was performed and it was further modified into an extended RSSO approach on both the sides of specimen. Quantitative measurements included area of brainstem exposure, surgical freedom, and angles of attack to key anatomical targets. For calculating the surgical exposure of the petroclival region, a polygon was defined in the exposed area connecting the following points: the posterior clinoid process, Meckel’s cave, internal acoustic canal, jugular foramen and two variable points (the highest and lowest point on the clivus). For calculating the ventral brainstem exposure, anatomical landmarks included root entry zones of trigeminal and facial nerve and three variable points on the brainstem (lowest medial, highest medial, and highest lateral part). Angle of attack was measured at oculomotor foramen, Meckel’s cave, Dorello’s canal, root entry zones of facial nerve and trigeminal nerve. Measurements were taken using a stereotactic navigation system and analyzed statistically to compare these approaches.

Results: The extended RSSO provided a significantly greater total brainstem exposure compared to standard RSSO, particularly in the anterior and lateral brainstem areas. It also improved surgical freedom to the petroclival region and a wider angle of attack to the ventral brainstem with the extended technique.

Conclusion: This study provides objective, quantitative data comparing these two surgical approaches. Results can guide surgical decision-making for lesions in the petroclival and ventral brainstem regions, potentially improving patient outcomes by allowing surgeons to choose the most appropriate approach based on lesion location and extent.

Publication History

Article published online:
07 February 2025