Transcanal anterior approach for cystic lesions of the petrous apex.

OBJECTIVE: To investigate the utility of a newly described approach, the transcanal anterior approach that is a modification of the subcochlear approach for the drainage of cystic lesions of the petrous apex. STUDY DESIGN: Prospective temporal bone study. SETTING: Tertiary referral center. MATERIALS: A total of six cadaveric temporal bone specimens (four males) were included. Right ear in four specimens and left ear in two specimens were used. INTERVENTIONS: The approach commenced with postauricular skin incision. After the transsection of the meatal skin, antero-inferior tympanotomy was performed. Anteroinferior canaloplasty localized the carotid canal. As much as 0.5 cm of the vertical segment of the internal carotid artery was skeletonized. After the identification of the artery, petrous apex cells were reached by drilling the cortical bone between the cochlea and the internal carotid artery. An air cell tract was established. Position and length of the tract in two specimens were demonstrated on the 1 mm-cut computerized tomography scans. MAIN OUTCOME MEASURES: Utility of the approach was investigated based on the established criteria: anteroposterior diameter and height of the fenestra of the tract, length of the tract from the cochlea to the deepest point of the tract (depth of the tract), and the injury risk of the internal carotid artery and the cochlea. RESULTS: The mean anteroposterior diameter, the height, and the length were 4.7 +/- 1.05 mm, 3.2 +/- 0.68 mm, and 14.7 +/- 1.1 mm, respectively. Injury did not occur in the cochlea or internal carotid artery in any of the specimens. CONCLUSION: With the subcochlear approach, there is always potential risk of injury to the cochlea, the internal carotid artery, and the jugular bulb. Although this new approach includes a technically challenging stage (exposing the vertical portion of the internal carotid artery), partly exposing the vertical portion of the artery provides a safer approach, which decreases the injury risk for the round window and the jugular bulb. Additionally, measurements show that it is possible to reach a considerable part of the petrous apex cells.