84 Chapter 5 DISCUSSION In this report, we present, to our knowledge, the first study on automated DTI in patients with trigonocephaly aged 0 to 3 years. Based on the increased prevalence of neurodevelopmental disorders in patients with trigonocephaly, we hypothesized that white matter tracts of the frontal lobe of patients with trigonocephaly would be abnormal from early life onward.2, 29-31 In this study, we did not detect a significant difference in the FA or MD values of frontal lobe tracts in young patients with trigonocephaly as compared to controls. A second reason could be that a difference between patients with trigonocephaly and controls could not be shown because the effect was masked by a large age difference between groups. The exact underlying pathophysiology of metopic synostosis is unclear, with two dominant hypotheses, namely an inborn brain disorder causing the metopic suture to close prematurely vs mechanical restriction in which the closed metopic suture causing impaired development of the frontal lobe.5, 7-9 In line with the theory that trigonocephaly is an inborn brain disorder, recent studies have shown that some genetic mutations found in patients with trigonocephaly overlap with patients with developmental delay disorders.10-12 This suggests that aberrant neural development, especially of the frontal lobe, is associated with metopic synostosis. Previous studies have demonstrated that neuro-developmental disorders occur in both unoperated patients with a mild trigonocephaly phenotype as well as in operated patients with a severe phenotype.2, 3 Mechanical restriction seems unlikely, as surgical intervention has not been proven to improve neuro-cognitive outcomes and the percentage of intracranial hypertension in patients with trigonocephaly is negligible.2-4 Several studies have investigated the associations between neurocognitive disorders and trigonocephaly. Studies focused on different aspects of neurocognitive development, including IQ behavior, autism, and characteristics of attention deficit hyperactivity disorder, oppositional deficit hyperactivity Disorder, or conduct disorder.2, 29-31 These studies strongly suggest that there is an increased risk for patients with trigonocephaly to develop neurocognitive disorders. Twenty-one to thirty-one percent of patients with trigonocephaly have an IQ < 80-85 as compared to <16% of the norm group. Translating these numbers to our cohort would mean a subset, of 9 to 14 patients of this cohort, would be affected. Although a previous study in preterm neonates used DTI as a predictive tool to assess neurocognitive functioning later in life, our study may have missed the subtle effect of only a subgroup of neurocognitively affected patients with trigonocephaly.32 However, if we assess the raw data, we cannot distinguish an outlying subgroup of patients with trigonocephaly. It
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