Age- and Sex-Specific Reference Curves of Posterior Cranial Fossa Structures in Children: The BIOMAP-PCF Study

BACKGROUND AND PURPOSE: The posterior cranial fossa (PCF) houses structures that are critical for neurological development and the integrated functioning of the central nervous system. Despite their clinical relevance, age and sex-specific reference biometric data in pediatrics remain limited. Aim of this study was to perform a Biometric Investigation Of Morphology and Anatomy in the Pediatric PCF (BIOMAP-PCF), to provide age- and sex-specific reference curves of these structures in a large pediatric population. MATERIALS AND METHODS: In this retrospective two-center study, 3D T1-weighted images of 1054 pediatric subjects from 0 to 18 years were analyzed (9.0±5.0 years, M/F=508/546). Different linear and cross-sectional area measurements of PCF structures were obtained, and age- and sex-specific reference intervals for each variable were estimated using the Royston and Wright method. To better evaluate the pattern of age-dependent changes between posterior cranial fossa structures, selected ratios were calculated. RESULTS: Reference values (3rd, median and 97th percentile) were obtained for each parameter. All measures showed nonlinear growth, with rapid changes in early childhood followed by progressive slowing. Ratios showed stable anteroposterior brainstem proportions across age, while the pons-to-midbrain craniocaudal ratio showed a mild age-related increase. Intra- and interobserver agreement was excellent (ICC>0.90) for all parameters, with the only exception of one measure showing an ICC=0.89. CONCLUSIONS: We provide highly reproducible age- and sex-specific reference curves for PCF structures in pediatric populations. Linear and cross-sectional area measurements, together with brainstem ratios, provide a reproducible, clinically applicable framework for quantitative assessment of PCF development in children.