A Combined Extradural–Intradural Technique for an En Bloc Anterior Petrosectomy: A Cadaveric Feasibility Study

The anterior petrosectomy approach is among the most popular for exposure of the petroclival region. However, the complexity of the anatomy, drilling time required, and risk of injury to neurovascular structures have made this procedure especially challenging. We have proposed a novel combined extradural–intradural technique for en bloc anterior petrosectomy—or one-piece Kawase—and have charted the landmarks that define its surgical boundaries. The approach was performed on 14 embalmed specimens. The one-piece Kawase approach consists of 3 extradural drilling steps, followed by incision of the dura and skeletonization of the superior petrosal sinus. The procedure culminates with 2 intradural drilling steps. The bone piece was then removed en bloc, and the maximum anteroposterior, superoinferior, and mediolateral lengths were recorded. The linear distances between the main neurovascular landmarks were also measured using a stereotactic navigation system. The mean measurements were 17.6 ± 2.6 mm for the anteroposterior distance, 10.5 ± 2.3 mm for the superoinferior distance, and 9.5 ± 2.6 mm for the mediolateral distance. The medial linear distance from the mandibular nerve/greater superficial petrosal nerve to the internal carotid artery was 6.8 ± 1.3 mm, to the facial hiatus was 11.6 ± 2.2 mm, and to the lateral internal acoustic canal was 17.9 ± 1.8 mm. The average distance from the porus trigeminus to the medial internal acoustic canal was 19.4 mm. The advantages of this technique include the wide exposure of the petroclival region, extensive visualization of critical structures via extradural and intradural corridors, and minimization of bone drilling, which could reduce heat damage. Clinical application of the illustrated technique is required to test its reliability in different pathological subsets.