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Age-Specific Biometric Ratios of the Posterior Fossa in Pediatric Neuroimaging: Establishing Normative Reference
Sam Mirfendereski1, Shahin Fesharaki1, Mohadeseh Zadehmir2
1Department of Radiology, Isfahan University of Medical Sciences, Isfahan, Iran.
Insights
This study establishes normative biometric ratios for pediatric posterior fossa structures, crucial for diagnosing conditions like cerebellar hypoplasia. The findings provide objective criteria to identify developmental anomalies in children.
Area of Science:
- Pediatric Radiology
- Neuroimaging
- Developmental Biology
Background:
- Normative biometric data for posterior fossa structures in children are essential for diagnosing conditions like cerebellar hypoplasia.
- A lack of objective, age-stratified biometric ratios limits diagnostic precision in pediatric posterior fossa anomalies.
- Previous studies on pediatric posterior fossa biometric data are limited.
Purpose of the Study:
- To establish objective, age-stratified biometric ratios for key posterior fossa structures in a pediatric population.
- To provide normative reference values for diagnosing cerebellar hypoplasia and other posterior fossa anomalies.
- To investigate sex-based differences in posterior fossa biometric parameters.
Main Methods:
- A cross-sectional study involving 420 children (≤15 years) undergoing MRI at Imam Hossein Children's Hospital.
- Measurement of 2D parameters: height of the vermian (H-V), anterior-posterior diameter of the vermis (APD-V), anterior-posterior diameter of the midbrain-pons junction (APD-MP), and anterior-posterior diameter of the midpons.
- Calculation of four biometric ratios (APD-P/APD-V, H-V/APD-V, H-V/APD-P, APD-P/APD-MP) to normalize morphology across age and sex.
Main Results:
- All posterior fossa parameters, except APD-V, were significantly higher in boys.
- The APD-P/APD-V ratio (mean 0.77 ± 0.09) increased with age, with values near or above 1.00 potentially indicating pontocerebellar hypoplasia.
- The H-V/APD-V ratio (mean 1.72 ± 0.18) showed a dip in early childhood (1-3 years), and the H-V/APD-P ratio declined from ~2.30 to ~2.11 with age.
- The APD-P/APD-MP ratio remained stable around 1.91-1.95, consistent with the 2:1 anatomical norm.
Conclusions:
- This study provides normative reference values and objective criteria for key posterior fossa biometric ratios in children.
- The established ratios, particularly APD-P/APD-V, can aid in the quantitative detection of anomalies like pontocerebellar hypoplasia.
- Findings highlight age- and sex-related variations in posterior fossa dimensions, contributing to more precise diagnoses.
Objectives:
Understanding normative biometric data of the posterior fossa is imperative to elucidate pathological alterations. Consequently, a reference for normative biometric data on posterior fossa structures in pediatric populations is essential for diagnosing cerebellar hypoplasia and other associated anomalies. However, a comprehensive set of objective, age-stratified biometric ratios for key posterior fossa structures is lacking, limiting diagnostic precision. To the best of our knowledge, only one study has evaluated the biometric data of the posterior fossa components in children.
Materials & Methods:
The current study is a cross-sectional study conducted among children hospitalized at Imam Hossein Children's Hospital in Isfahan, Iran, in 2022-2023. All magnetic resonance imaging (MRI) examinations, including midline sagittal sections, performed in children ≤ 15 years of age, were included. Patients with a clinical history of posterior fossa involvement or MRI abnormalities were excluded from this study. Two-dimensional (2D) parameters, including the height of the vermian (H-V), anterior-posterior diameter of the vermis (APD-V), anterior-posterior diameter of the midbrain-pons junction (APD-MP), and anterior-posterior diameter of the midpons, were all measured. Four biometric ratios were calculated to normalize posterior fossa morphology across age groups, accounting for individual size variability and providing objective criteria.
Results:
Four hundred twenty patients, with a mean age of 5.79 ± 4.02 years, were investigated, of whome 222 (52.9%) were boys. All parameters, except APD-V, were significantly higher in boys than in girls. Although boys had a higher mean APD-V than girls, this difference was not statistically significant. In addition, all studied parameters had the fastest growth rates in the first year and continued to grow more slowly until the end of the 15th year. Key findings reveal a mean APD-P/APD-V ratio of 0.77 ± 0.09. The ratio was generally higher in older children, indicating that pontine growth outpaces vermian expansion during development-values near or above 1.00 may suggest pontocerebellar hypoplasia. The H-V/APD-V ratio (mean 1.72 ± 0.18) shows a dip in early childhood, particularly at 1-3 years, suggestingtransient vermian flattening. The H-V/APD-P ratio declines from ~2.30 in infancy to ~2.11 in adolescence, reflecting posterior fossa maturation. Meanwhile, the APD-P/APD-MP ratio remains consistently around 1.91-1.95, aligning with the expected 2:1 anatomical norm, and serving as a reliable reference across age and sex groups.
Conclusion:
The present study showed that all posterior fossa parameters, except APD-V, were significantly higher in boys. This study establishes normative reference values for key posterior fossa ratios. The APD-P/APD-V ratio (mean 0.77 ± 0.09) increases with age, while the H-V/APD-P ratio declines from ~2.30 to ~2.11. The APD-P/APD-MP ratio remains stable at ~1.91, consistent with the 2:1 anatomical norm. These objective criteria provide quantifiable thresholds for detecting anomalies like pontocerebellar hypoplasia.
