Mandibular asymmetry in plagiocephaly without synostosis

SUBJECT: The number of plagiocephalies without synostosis (PWS) strongly increased in the last decade. Its impact on the mandible remains badly understood, the more so as there are various forms of PSS. The purpose of this study was to analyze mandible deformation according to the deformation of PWS. MATERIAL AND METHODS: The study was carried out retrospectively starting from three-dimensional scans of children presenting with a PWS. They were classified in 2 groups according to the deformation of the cranium. There were 51 frontal plagiocephalies (PF) and 19 occipital plagiocephalies (PO) for which the cephalic index was calculated. The position of the mandible compared to the base of cranium and its intrinsic asymmetry were analyzed (paired parametric Student test). RESULTS: The mandible was symmetrical in PO whereas it was asymmetrical for PF. This asymmetry was present at the level of the corpus and developed in 2 ways: that is to say asymmetry compensated for that of the base of the cranium (68.6%); or it worsened it (23.5%). The degree of brachycephaly was more important in PO than the PF with a cranial index of 0.93+/-0.07 and 0.85+/-0.07 respectively (P<0.05). In both cases the position of the mandibular condyle followed the asymmetry of the base of cranium and the asymmetry of the temporomandibular joint (TMJ) was secondary with that of the base of cranium. DISCUSSION: In addition to the asymmetry of TMJ position there was an intrinsic mandibular asymmetry in PF which was not found in PO. This asymmetry of the mandible was variable but in most cases it tended to compensate for the asymmetry of the base of the cranium which was more important in PF. The risk to have asymmetry of dental occlusion seems more important in PF than in PO, and an orthodontic follow-up appeared to be justified for these children.