Maturation of the anterior petrous apex: surgical relevance for performance of the middle fossa transpetrosal approach in pediatric patients

OBJECTIVE The middle fossa transpetrosal approach to the petroclival and posterior cavernous sinus regions includes removal of the anterior petrous apex (APA), an area well studied in adults but not in children. To this end, the authors performed a morphometric analysis of the APA region during pediatric maturation. METHODS Measurements of the distance from the clivus to the internal auditory canal (IAC; C-IAC), the distance of the petrous segment of the internal carotid artery (petrous carotid; PC) to the mesial petrous bone (MPB; PC-MPB), the distance of the PC to the mesial petrous apex (MPA; PC-MPA), and the IAC depth from the middle fossa floor (IAC-D) were made on thin-cut CT scans from 60 patients (distributed across ages 0-3, 4-7, 8-11, 12-15, 16-18, and > 18 years). The APA volume was calculated as a cylinder using C-IAC (length) and PC-MPB (diameter). APA pneumatization was noted. Data were analyzed by laterality, sex, and age. RESULTS APA parameters did not differ by laterality or sex. APA pneumatization was seen on 20 of 60 scans (33.3%) in patients ≥ 4 years. The majority of the APA region growth occurred by ages 8-11 years, with PC-MPA and PC-MPB increasing 15.9% (from 9.4 to 10.9 mm, p = 0.08) and 23.5% (from 8.9 to 11.0 mm, p < 0.01) between ages 0-3 and 8-11 years, and C-IAC increasing 20.7% (from 13.0 to 15.7 mm, p < 0.01) between ages 0-3 and 4-7 years. APA volume increased 79.6% from ages 0-3 to 8-11 years (from 834.3 to 1499.2 mm3, p < 0.01). None of these parameters displayed further significant growth. Finally, IAC-D increased 51.1% (from 4.3 to 6.5 mm, p < 0.01) between ages 0-3 and adult, without significant differences between successive age groups. CONCLUSIONS APA development is largely complete by the ages of 8-11 years. Knowledge of APA growth patterns may aid approach selection and APA removal in pediatric patients.