The developing anterior skull base: CT appearance from birth to 2 years of age.

PURPOSE To describe the normal CT appearance of the developing anterior skull base in children 24 months of age and younger. METHODS A retrospective review of the CT examinations of a healthy population of 61 subjects newborn through 24 months of age was performed. Two investigators independently reviewed the examinations, making measurements and observations regarding the length of the skull base, ossification pattern, and development of the crista galli, perpendicular plate of the ethmoid bone, and fovea ethmoidalis. RESULTS At birth, the anterior skull base is largely cartilaginous. Ossification begins in the roof of the ethmoidal labyrinth laterally and spreads toward the midline. By 6 months of age, 50% of the anterior skull base has completely ossified. This percentage steadily increases over the first 2 years of life, and by 24 months, 84% of the anterior skull base is completely ossified, with a cartilaginous gap anteriorly in the region of the foramen cecum, the residual unossified portion. Ossification of the crista galli and perpendicular plate of the ethmoid bone begins around 2 months of age, shows a steady increase in ossification to 14 months of age, then increases little to 24 months of age. The fovea ethmoidalis begins development by 6 months of age, with the anterior portion the most developed in 82% of the population. CONCLUSION The timing and pattern of ossification we observed differ somewhat from that reported in prior radiologic and anatomic studies, with the earliest bony bridging of the ethmoidal complex to the crista galli seen as early as 2 months of age. Development of the anterior skull base follows a predictable and orderly pattern that is important for understanding how to avoid errors in interpreting CT examinations through this region.