181 Summary In Chapter 6 we perform a prospective diffusion tensor imaging MRI study in nonoperated syndromic craniosynostosis patients aged 0-2 years. Before any surgery, microstructural parameters of white matter tracts of syndromic craniosynostosis patients are comparable to those of controls aged 0-2 years. Subsequent analyses show that age and FOHR are associated factors. Enlargement of the ventricles plays a significant role on RD in the corpus callosum genu and the hippocampal segment of the cingulate bundle. In Chapter 7 the cortical thickness of the brain in Crouzon syndrome is assessed in relation to the area of vault expansion. This study does not find any difference in effect between frontal and occipital vault expansion on global and lobar cerebral cortical thickness. Lambdoid synostosis is shown to be associated with thinning across all brain regions, but particularly within the cingulate and frontal cortices. This leads us to question our hypothesis of localized growth restriction affecting underlying cortical lobes and to consider more how lambdoid synostosis contributes to intracranial pressure elevation and subsequent thinning in distant regions of the brain by causing e.g. a crowded posterior fossa and enlarged ventricles. In Chapter 8 the course of ventriculomegaly and cerebellar tonsillar position over time and its potential associations in children with Crouzon syndrome are investigated. We find that ventricular size in Crouzon patients is large at onset but decreases and stabilizes with treatment over time. Ventricular size is shown to be associated with headcircumference and tonsillar herniation. Irrespective of treatment, both the incidence of patients with tonsillar herniation as well as the severity of tonsillar herniation (in millimeter) itself show to increase over time, is strongly associated with lambdoid suture synostosis and ventricular size. Treatment aimed to correct ventriculomegaly is effective and may prevent tonsillar herniation in the long term, while (posterior) vault expansion appears to have little effect on the development of tonsillar herniation. At last, Chapter 9 dives into the rare and severe course of patients with Crouzon syndrome and acanthosis nigricans. Three European craniofacial centres have undertaken this multicentre study to assess clinical signs in relation to the required interventions and treatment course of these patients. This study reveals patients with the mutation c.1172C>A (p.Ala391Glu) in FGFR 3 gene follow a severe clinical course, requiring numerous interventions. Timing and order of interventions differs between patients and centers, but no obvious difference in outcome was related to this. 11
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