Quantitative analysis of surgical exposure and maneuverability associated with the endoscope and the microscope in the retrosigmoid and various posterior petrosectomy approaches to the petroclival region using computer tomograpy-based frameless stereotaxy. A cadaveric study. - Chi-Tun Tang; Kurozumi, Kazuhiko; Pillai, Promod; Filipce, Venko; Chiocca, E. Antonio; Ammirati, Mario (Clinical Neurology & Neurosurgery, 2013)