The role of the posterior fossa in developing Chiari I malformation in children with craniosynostosis syndromes.

OBJECTIVE: Patients with craniosynostosis syndromes are at risk of increased intracranial pressure (ICP) and Chiari I malformation (CMI), caused by a combination of restricted skull growth, venous hypertension, obstructive sleep apnea (OSA), and an overproduction or insufficient resorption of cerebrospinal fluid. This study evaluates whether craniosynostosis patients with CMI have an imbalance between cerebellar volume (CV) and posterior fossa volume (PFV), that is, an overcrowded posterior fossa. METHODS: Volumes were measured in 3D-SPGR T1-weighted MR scans of 28 'not-operated' craniosynostosis patients (mean age: 4.0 years; range: 0-14), 85 'operated' craniosynostosis patients (mean age: 8.0 years; range: 1-18), and 34 control subjects (mean age: 5.4 years; range: 0-15). Volumes and CV/PFV ratios were compared between the operated and not-operated craniosynostosis patients, between the individual craniosynostosis syndromes and controls, and between craniosynostosis patients with and without CMI. Data were logarithmically transformed and studied with analysis of covariance (ANCOVA). RESULTS: The CV, PFV, and CV/PFV ratios of not-operated craniosynostosis patients and operated craniosynostosis patients were similar to those of the control subjects. None of the individual syndromes was associated with a restricted PFV. However, craniosynostosis patients with CMI had a significantly higher CV/PFV ratio than the control group (0.77 vs. 0.75; p = 0.008). The range of CV/PFV ratios for craniosynostosis patients with CMI, however, did not exceed the normal range. CONCLUSION: Volumes and CV/PFV ratio cannot predict which craniosynostosis patients are more prone to developing CMI than others. Treatment should focus on the skull vault and other contributing factors to increased ICP, including OSA and venous hypertension.

The occipitofrontal circumference: reliable prediction of the intracranial volume in children with syndromic and complex craniosynostosis.

OBJECT Patients with syndromic and complex craniosynostosis are characterized by the premature fusion of one or more cranial sutures. These patients are at risk for developing elevated intracranial pressure (ICP). There are several factors known to contribute to elevated ICP in these patients, including craniocerebral disproportion, hydrocephalus, venous hypertension, and obstructive sleep apnea. However, the causal mechanism is unknown, and patients develop elevated ICP even after skull surgery. In clinical practice, the occipitofrontal circumference (OFC) is used as an indirect measure for intracranial volume (ICV), to evaluate skull growth. However, it remains unknown whether OFC is a reliable predictor of ICV in patients with a severe skull deformity. Therefore, in this study the authors evaluated the relation between ICV and OFC. METHODS Eighty-four CT scans obtained in 69 patients with syndromic and complex craniosynostosis treated at the Erasmus University Medical Center-Sophia Children's Hospital were included. The ICV was calculated based on CT scans by using autosegmentation with an HU threshold < 150. The OFC was collected from electronic patient files. The CT scans and OFC measurements were matched based on a maximum amount of the time that was allowed between these examinations, which was dependent on age. A Pearson correlation coefficient was calculated to evaluate the correlations between OFC and ICV. The predictive value of OFC, age, and sex on ICV was then further evaluated using a univariate linear mixed model. The significant factors in the univariate analysis were subsequently entered in a multivariate mixed model. RESULTS The correlations found between OFC and ICV were r = 0.908 for the total group (p < 0.001), r = 0.981 for Apert (p < 0.001), r = 0.867 for Crouzon-Pfeiffer (p < 0.001), r = 0.989 for Muenke (p < 0.001), r = 0.858 for Saethre- Chotzen syndrome (p = 0.001), and r = 0.917 for complex craniosynostosis (p < 0.001). Age and OFC were significant predictors of ICV in the univariate linear mixed model (p < 0.001 for both factors). The OFC was the only predictor that remained significant in the multivariate analysis (p < 0.001). CONCLUSIONS The OFC is a significant predictor of ICV in patients with syndromic and complex craniosynostosis. Therefore, measuring the OFC during clinical practice is very useful in determining which patients are at risk for impaired skull growth.