A combined dual-port endoscope-assisted pre- and retrosigmoid approach to the cerebellopontine angle: an extensive anatomo-surgical study

The use of the endoscope in the cerebellopontine angle (CPA) has been suggested to minimize cerebellar retraction and reduce the size of the craniotomy. 3D endoscopy combines the benefits of conventional 2D endoscopy with the added benefit of stereoscopic perception, though improved visualization alone does not guarantee improved surgical maneuverability and a better surgical outcome. We propose a new combined dual-port endoscope-assisted pre- and retrosigmoid approach to improve visualization and accessibility of the CPA with shortened distances and increased surgical maneuverability of neurovascular structures. We analyze surgical exposure and maneuverability of this approach and compare it with the surgical microscopic and a conventional single-port endoscope-assisted retrosigmoid approach. This combined pre- and retrosigmoid approach was performed on eight cadaveric heads (16 sides). The endoscopic probe was inserted through the presigmoid surgical port while surgical manipulation was performed through the retrosigmoid corridor. The CPA was divided into three compartments, from medial to lateral, the anteromedial, and the middle and the posterolateral. The microscope provided good visualization of the posterolateral and middle compartments, whereas poor visualization was offered of the anteromedial compartment. The dual-port endoscopic approach dramatically improved visualization and surgical maneuverability of the anteromedial compartments, clivus, and related neurovascular structures. Additionally, the 3D endoscope allowed for a better understanding of the surgical anatomy of the CPA and improved visualization of structures located in the anteromedial compartments towards the midline. This approach allowed for full realization of the benefits of endoscopic-assisted technique by improving surgical access and maneuverability.