Surgical Relevance of Pediatric Skull Base Maturation for the Far-Lateral Approach

Object: Lesions of the foramen magnum and inferolateral clivus are often treated using a far-lateral approach. The development and surgical relevance of critical skull base bony structures encountered during this approach, including the occipital condyle (OC), hypoglossal canal (HGC), and jugular tubercle (JT), are nonetheless poorly defined in the pediatric population.

Methods: Measurements from high-resolution computed tomography (CT) scans were made of the relevant skull base anatomy (OC area, HGC depth from posterior edge of OC, and JT dimensions; [Fig. 1]) from 60 pediatric patients (evenly distributed from ages 0–3, 4–7, 8–11 12–15, and 16–18 years) and 10 adult patients, and analyzed via parametric testing and logistic regression.

Results: There were no significant differences in skull base parameters by laterality, and HGC depth and JT size did not differ by sex. OC area was significantly larger in males versus females (221.16 vs. 191.27 mm²; p = 0.01). From ages 0–3 to adult, mean HGC depth increased by 26% from 8.9 to 11.3 mm and OC area increased by 52% from 121.4 to 184.0 mm² ([Fig. 2A], [B]). The majority of growth for these parameters occurred between the 0–3 to 4–7 age groups. Conversely, JT volume increased nearly 3-fold (281%) from 97.4 to 370.9 mm3 from ages 0–3 to adult, with two periods of substantial growth seen between the 0–3 to 4–7 and 12–15 to 16–18 age groups ([Fig. 2C]). Overall, JT growth during pediatric development was significantly greater than increases in HGC depth and OC area (p <  0.03; [Fig. 3]). JT volume remained < 65% of adult size up to age 16.

Conclusion: When performing a far-lateral approach in pediatric patients, standard OC drilling is likely to be needed due to the relative stability of OC and HGC anatomy during development. The JT significantly increases in size with development, yet likely only needs to be drilled in in older children (>16) and adults.