Radiological Study of the Carotid-Clival Window and Its Application in Endoscopic Endonasal Expanded Approaches

Background The surgical approach to the petrous apex (PA) and petroclival junction (PCJ) remains a challenge. The carotid-clival window (CCW) represents the widest window available to approach the PCJ from a mediolateral endoscopic route. Here we define the CCW radiologically in nonpathological conditions, to establish the anatomic variability of the PCJ, relate this variability to pneumatization patterns, and evaluate some technical concerns conditioned by the CCW. Methods This was an analytical study of 10 multislice computed tomography scans from patients without SB pathology. Bilateral measures were taken at the roof and floor levels of the lacerum canal (LC) and its posterior projection over the PCJ (segments DE and QR). All measures were compared across different pneumatization patterns. Results The DE and QR lengths were found to be the most important measures affecting the width of the CCW. Wide variability was observed, with a mean DE length of 8.52 mm (range, 2.4–12.8 mm) at the LC floor level and a mean QR length of 9.11 mm (range, 4.3–13.1 mm) at the LC roof level. The presence of retrocarotid pneumatization was statistically significantly associated with longer DE and QR segments. No differences were found among other pneumatization patterns. Conclusions The CCW varies widely among individuals. The presence of pneumatization behind the paraclival carotid represents an advantageous characteristic when planning an endoscopic approach to the PCJ.