143 Ventriculomegaly and TH | Crouzon own, but also in how often they occur together between studies using single timepoint measurements and serial measurements.20, 23 In this report, the great variation in sequence in which ventriculomegaly and TH ≥ +5mm can occur is exemplified in our relatively large and homogenous group of only Crouzon patients with repeated measurements. Our study showed patients who start with TH ≥ +5mm and develop ventriculomegaly (n = 1), but also those who start with ventriculomegaly and develop TH ≥ +5mm (n = 5), those in whom ventriculomegaly and TH ≥ +5mm are detected at the same time (n = 12), those who start with ventriculomegaly and never get TH ≥ +5mm (n = 13), and those who have TH ≥ +5mm and never develop ventriculomegaly (n = 11). These variations exemplify why it is so difficult to predict at onset which clinical course an individual patient will follow and shows the need for individual treatment plans for Crouzon patients. Figures 3 and 4 show that although FOHR is high at onset, it declines and remains stable from 5 years of age onward. Tonsil position, on the other hand, continues to increase even after the age of 5 years, when FOHR remains stable. This could indicate that TH ≥ +5mm on its own does not contribute to ventriculomegaly in Crouzon patients. This is supported by our finding that only one in 18 patients who eventually developed both TH ≥ +5mm and ventriculomegaly developed TH ≥ +5mm before developing ventriculomegaly. Furthermore, because TH ≥ +5mm rarely causes neurological deficits, we should question how much of the treatment protocol should be focused on treating/stabilizing TH.11, 27, 28 Recent studies show a relationship between ventriculomegaly and increased diffusivity values in white matter tracts of the corpus callosum and cingulate gyrus.29 This is associated with internalizing and externalizing behavior, showing the importance of treating ventriculomegaly at onset in Crouzon patients.30, 31 This study’s first limitation is its retrospective aspect. Over time a shift occurred in the availability of brain imaging material. Starting in 2007, we implemented a protocol, including MRI assessment before surgery. Patients who were treated before this time underwent only CT imaging; thus, tonsil position before surgery could not be determined. Most of these patients underwent MRI assessment after first vault surgery. The second limitation is that we did not have a control group of patients who did not undergo surgical intervention because we aimed to operate on all children before 1 year of age. We therefore cannot determine what changes in FOHR or tonsil position are due to natural progression or due to iatrogenic effects. Similarly, in our small group of patients who underwent VP-drain/ETV, some showed increase in TH; we could not determine if this was despite VP-drain/ETV, or if this was due to iatrogenic effects. These could be topics of interest for future studies. 8
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