Anatomic Assessment of Petrous Internal Carotid Artery, Facial Nerve, and Cochlea Through the Anterior Transpetrosal Approach

The aim of this study was to measure the related parameters of the cochlea, so as to allow preoperative assessment of the anatomic relationship of the petrous internal carotid artery (ICA), the facial nerve (FN), and the cochlea during skull base surgery. Seven parameters of these 3 structures were examined in the computed tomographic scan of 120 patients. The shortest distance from the cupula cochleae to the petrous ICA and the FN is as follows: 19.39 (1.01)mm to the stylomastoid foramen (D-2), 10.27 (0.80)mm to the midpoint of the genu of FN canal (D-3), 13.66 (0.88)mm to the exocranial opening of the carotid canal (D-4), and 5.64 (1.03)mm to the midpoint of carotid knee (D-5). The shortest distance between the mastoid segment of FN canal and the vertical segment of the petrous ICA (D-6) was 13.33 (1.25)mm. The angle between D-2 and D-3 was measured at 45.66 (3.31)degrees, and the angle between D-4 and D-5 was measured at 41.08 (2.64)degrees. Clinically, it is relatively safe to work within the distances and angles measured in this research, and these results may give surgeons a practical and specific view of these 3 structures in the skull base approaches such as anterior transpetrosal approach to achieve the best possible surgical outcome and maximize safety.