Morphology of the foramen magnum in syndromic and non-syndromic brachycephaly: letter to the editor.

Abstract

Dear Editor, It is with great interest that we read the paper entitled BMorphology of the foramen magnum in syndromic and non-syndromic brachycephaly^ by Assadsangabi et al.[1]. The authors studied the shape and size of the foramen magnum in syndromic craniosynostosis including Apert, Crouzon, and Pfeiffer syndromes. Using the same methodology we applied in a previous paper [2], that is (i) non-parametric comparison, (ii) transverse and anteroposterior diameter analysis, (iii) LOESS regression curve, the authors found that patients with Crouzon syndrome and Pfeiffer syndrome have a smaller area of the foramen magnum than control subjects. Conversely, patients with non-syndromic synostosis have a foramen magnum similar to controls. Unfortunately, it is not clear whether all the children included in their study were classified according to a genetic confirmation of the syndromes as the authors only mention that Bpatients with a clinical and/or genetic diagnosis of Crouzon, Pfeiffer, Apert and SaethreChotzen^ were studied. Including only patients with genetically confirmed syndromes is a strong argument for the homogeneity of the population and allows a comparison with published series [2–5]. This is of critical importance in the so-called non-syndromic cases in which a Pro250Arg mutation in FGFR3 or a TCF12 mutation could be missed clinically [6]. Indeed, in a previous study, we found that patients with bicoronal synostosis and FGFR3 mutation actually have a smaller foramen compared to controls [5]. Moreover, it is unfortunately not specified in the paper the percentage of hydrocephalic patients nor the number of patients who received a ventriculoperitoneal cerebrospinal fluid shunt or any other procedure for the management of CSF circulation disorders. It is well recognized in the medical literature that the placement of a ventriculoperitoneal shunt may induce a secondary craniosynostosis or aggravate a preexisting one [7–13]. Hydrocephalus is common in these children. In the literature, several studies have found hydrocephalus in 9 to 17 % of patients with Crouzon syndrome, 28 to 64 % of patients with Pfeiffer syndrome, and 4 to 7 % of patients with Apert syndrome [3, 14–21]. The presence of hydrocephalus is also important in regard to the size of the foramenmagnum [2, 3]. In a similar study in genetically confirmed FGFR2-related faciocraniosynostosis (31 children under 2 years of age before any surgical procedure, 14 with Crouzon syndrome, 11 with Apert syndrome, and 6 with Pfeiffer syndrome), we found in fact that hydrocephalus was statistically associated with a small foramen magnum area in Crouzon and Pfeiffer syndromes but not in Apert syndrome [3]. Finally, the disparity found in the ages of the children studied in the article also represents a limitation. The use of age groups would have overcome the bias related to the growth of the skull base found in the pediatric population [3]. It is nevertheless interesting that the results of this study corroborate those of the literature, thus adding some confirmation that the skull base growth is deeply altered in complex synostosis. * Guillaume Coll gcoll@chu-clermontferrand.fr