Quantitative Analysis of the Far-Lateral, Supra-Articular Transcondylar Transtubercular Approach Using Cadaveric Computed Tomography and Magnetic Resonance Imaging.

Abstract

Removing the jugular tubercle (JT) is regarded as an important step in the far-lateral approach; however, few cadaveric studies have objectively evaluated it. To quantitatively analyze the effect of JT removal in the far-lateral approach, using cadaveric computed tomography (CT) and magnetic resonance (MR) imaging. The far-lateral, supra-articular transcondylar transtubercular approach was employed on 23 sides of 13 formalin-fixed cadaveric heads. CT bone images were obtained before and after JT removal, and MR images were obtained before dissection and were merged with the CT bone images. The angles of attack used to approach the ventral region of the medulla, the distances between the medulla and the bony structure, and the volume of the paramedullary space were measured at the level of the JT on axial CT-MR fusion images. The values obtained after JT removal were compared with those obtained before JT removal. All evaluated values were significantly increased after JT removal, including the angle of attack at the level of the JT (29.8±7.4° vs 58.2±15.5°, P<.001), the distance between the olive and the JT (6.4±2.0 mm vs 9.5±5.0 mm, P=.01), and the volume of the space around the medulla (0.28±0.04 cm3 vs 0.47±0.09 cm3, P<.001). The paramedullary surgical working space widened by JT removal was quantitatively demonstrated in the cadaveric CT and MR imaging study. The measurement methods in this study can be applied to clinical cases and other skull base cadaveric studies.