Developmental changes in the posterior cranial fossa of children studied by CT.

We reviewed 181 brain CT examinations, with no abnormal findings, to determine normative data for the posterior cranial fossa (PF) in children. The volume of the PF and the supratentorial cranial cavity (SC) was assessed by summing consecutive CT cross-sectional areas. Linear measurements of the PF structures-cerebellum, vermis, brain stem and fourth ventricle were also performed. The PF grows rapidly during the first 3 years of life and thereafter a smaller increase in size is observed. All the PF structures showed a positive correlation with the PF volume. The PF volume increased in parallel with that of the SC and the PF/SC volume ratio remained relatively constant during childhood. The establishment of normative data for the volume of the PF and its contents may be of value in the CT study of diseases associated with morphological alterations in the PF.