139 Ventriculomegaly and TH | Crouzon Figure 3 displays the expected FOHR and corresponding 95% CIs across age for different scenarios with respect to tonsil position, head-circumference and closed lambdoid sutures at the age of less than 1 year. It shows that FOHR starts high during the first 1.5 years of life, declines with treatment and time, and from the age of 5 years remains relatively stable. Figure 3A displays the expected FOHR in two scenarios where tonsil position is either 0mm (first quartile in observed data; Q1) or +8.6mm (third quartile in observed data; Q3). The other variables were set to the median (headcircumference: 0.51 SD) and reference category (lambdoid sutures: open). It visualizes the difference in FOHR associated with tonsil position at Q1 and Q3: at age 0 an FOHR of 0.44 (Q1 range 95% CI band: [0.42–0.47]) versus 0.49 (Q3 range 95% CI-band: [0.45–0.52]), and at age 5 years an FOHR of 0.34 (Q1 range 95% CI-band [0.33–0.36]) versus 0.38 (Q3 range 95% CI-band [0.36–0.41]). Figure 3. Expected FOHR across age by 3 different covariate values. Expected FOHR and corresponding 95% CI across age, by specific covariate values: FOHR by tonsil position (A); FOHR by head circumference (B); FOHR by lambdoid suture closure before the age of 1 year (C). Variables that are not shown in a particular panel were set to reference/median values (tonsillar position: +3.88 mm, head-circumference: 0.51 SD, lambdoid suture: open). Results of the mixed-model for tonsil position are given in Table 3. Ten percentagepoint higher FOHR was associated with a +1. 597mm increase in tonsil position (95% CI[0.410–3.047]). Figure 4 visualizes the estimated development of tonsil position over time for different scenarios with regard to FOHR values, head-circumference, and closed lambdoid sutures at the age of less than 1 year. It presents a steep increase in tonsil position during the first 2.5 years of life, after which it slows down. Figure 4A shows the expected tonsil position in two scenarios, where FOHR is either 0.33 (Q1) or 0.41 (Q3), and shows an overlap between their 95% CIs. Again, for these scenarios, the other independent variables are set to median or reference values. 8
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