130 Chapter 8 ABSTRACT Background: Children with Crouzon syndrome have a higher incidence of cerebellar tonsillar herniation (TH) and ventriculomegaly than the general population, or children with other craniosynostosis syndromes. Objective: This retrospective cohort study aimed to determine how ventriculomegaly and TH develop and progress over time and determine associations between ventriculomegaly and TH in Crouzon patients, treated according to our center’s protocol. Methods: Fronto-occipital horn ratio (FOHR) and TH were determined over time using brain-imaging. These data were used to fit a mixed-model to determine associations between them, and with clinical variables, head-circumference, and lambdoid suture synostosis. Results: Sixty-three Crouzon patients were included in this study. Preoperatively, 28% had ventriculomegaly, and 11% had TH ≥ +5mm. Postoperatively ventriculomegaly increased to 49%. Over time and with treatment, FOHR declined and stabilized around 5 years of age. TH ≥ +5mm increased to 46% during follow-up. FOHR and TH were associated: expected FOHR with a TH of either 0mm versus +8.6mm at 0 years: 0.44 versus 0.49, and at 5 years: 0.34 versus 0.38; 10% increase of FOHR was associated with 1.6mm increase in TH. Increased head-circumference was associated with increased FOHR. Lambdoid suture synostosis was associated with +6.9mm TH increase. Conclusions: In Crouzon patients, FOHR was large at onset and decreased and stabilized with treatment and time. FOHR was associated with head-circumference and TH. TH was strongly associated with lambdoid suture synostosis and FOHR. Increased head-circumference was associated with an increased FOHR and closed lambdoid sutures before 1 year of age were associated with a +6.92mm increase in tonsil position.
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