Does the association between abnormal anatomy of the skull base and cerebellar tonsillar position also exist in syndromic craniosynostosis?

Purpose: Cerebellar tonsillar herniation (TH) occurs frequently in syndromic craniosynostosis; however, the exact pathogenesis is unknown. This study evaluates the association between skull base deformities and TH in syndromic craniosynostosis. Methods: Retrospective study MRI study comparing syndromic craniosynostosis to controls. Measured parameters included clivus length, skull base angle, Boogard's angle, foramen magnum area, and cerebellar tonsillar position (TP). The association between skull base parameters and TP was evaluated with linear mixed models, correcting for age and risk factors for TH in craniosynostosis (hydrocephalus, intracranial hypertension, craniocerebral disproportion, and lambdoid synostosis). Results: Two hundred and eighty-two scans in 145 patients were included, and 146 scans in 146 controls. The clivus was smaller at birth, and its growth was retarded in all syndromes. The skull base angle was smaller at birth in Apert and Crouzon syndromes, and the evolution through time was normal. Boogard's angle was smaller at birth in Apert syndrome, and its evolution was disturbed in Apert and Saethre-Chotzen syndromes. The foramen magnum was smaller at birth in Crouzon and Saethre-Chotzen syndromes, and its growth was disturbed in Apert, Crouzon, and Saethre-Chotzen syndromes. TP was higher at birth in Apert syndrome, but lowered faster. In Crouzon syndrome, TP was lower at birth and throughout life. A smaller clivus and larger foramen magnum were associated with a lower TP in controls (p<0.001, p=0.007), and in Crouzon syndrome, this applied to only foramen magnum size (p=0.004). Conclusion: The skull base and its growth are significantly different in syndromic craniosynostosis compared to controls. However, only foramen magnum area is associated with TP in Crouzon syndrome.