Three-dimensional computed tomographic cranial base measurements for improvement of surgical approaches to the petrous carotid artery and apex regions

OBJECTIVE: The bony and vascular anatomic features in the region of the pet rous apex can vary significantly. These variations affect the operative vie w obtained via extended subtemporal or anterior transpetrosal approaches to cranial base lesions for individual patients. The goal of this study was t o evaluate three-dimensional computed tomography as a means of obtaining de tailed preoperative anatomic information regarding bony and vascular landma rks and spatial relationships in the region of the petrous carotid artery a nd petrous apex. METHODS: We radiographically studied 15 patients (30 sides), using 0.8- to 1-mm-thick, reconstructed, computed tomographic images. Special attention w as given to the course of the petrous carotid artery. RESULTS: The petrous carotid artery was located lateral to the trigeminal i mpression. The size of the petrous apex medial to the horizontal petrous ca rotid artery was observed to be variable. The width of bone from the trigem inal impression to the wall of the internal auditory canal averaged 9.6 mm (range, 5.2-16.1 mm). A variable amount of bone overlying the internal audi tory canal (4.5 mm) was also present. Multiple other relationships among ke y landmarks were quantified. CONCLUSION: There is significant variability in the anatomic features of th e petrous apex among patients. For each patient, detailed preoperative info rmation regarding the amount of bone to be removed during a cranial base pr ocedure can be obtained using three-dimensional computed tomography. This i nformation may be critical for determination of the amount of extra exposur e that can be achieved via an anterior petrosectomy for each patient.