CT-Based Timeline for Closure of Sphenoid Body Synchondroses and Foramina in Children.

Background and purpose: The sphenoid bone is formed from multiple ossification centers. Its body develops through the fusion of the presphenoid and postsphenoid cartilages separated by the inter-sphenoidal synchondrosis. Variations in ossification can lead to persistent craniopharyngeal duct remnants, potentially associated with pituitary dysfunction or tumors. We aimed to determine the timeline of closure of these synchondroses and associated foramina in children without skull base abnormalities on CT scans.

Materials and methods: This retrospective study analyzed CT scans of children aged 0-6 years from a tertiary pediatric hospital (2018-2022). Scans with abnormalities or skull anomalies were excluded. Two pediatric radiologists assessed synchondroses and foramina, classifying them as patent or fused. Sample size was determined using AUC analysis. Statistical methods included descriptive analysis, interrater reliability (Cohen's Kappa, ICC), Mann-Whitney U test, and cut point analysis with bootstrapping to determine closure times.

Results: We analyzed 160 scans (94 males, 58.8%; 66 females, 41.2%) with a median age of 1.4 years (IQR: 0.3-3.7). Interrater reliability was strong (κ > 0.80) for most structures, moderate for detecting intra-pre-sphenoid synchondrosis and pneumatization, and weak for intra-post-sphenoidal synchondrosis. Cut-point analysis demonstrated that the inter-sphenoid synchondrosis fused first at 4 months, followed by the intra-pre-sphenoid synchondrosis, the anterior and posterior foramen, with pneumatization occurring last at 24.8 months; all with an area under the curve > 80%. Pairwise threshold differentiation showed pneumatization followed the closure of inter-sphenoid synchondrosis, intra-pre-sphenoid synchondrosis, and anterior foramen by 22.8, 22.7, and 17.4 weeks, respectively.

Conclusions: The sphenoid body synchondroses and foramina show a predictable closure timeline within the first year of life, while pneumatization commences after the second year. Understanding this timeline provides radiologists with a reference standard for interpreting CT examinations that include the skull base (e.g., head, maxillofacial, temporal bone CTs) in children under two years of age, supporting more confident interpretation and potentially reducing overcalling and related follow-up imaging.

Abbreviations: AUC＝Area Under the Curve; CI＝Confidence Interval; IQR = Interquartile Range.