ORIGIN OF CALVARIAL SUTURES IN RELATION TO DURAL REFLECTIONS: NORMAL DEVELOPMENT AND PREDICTABLE ALTERATIONS SECONDARY TO BRAIN MALFORMATION

Abstract

Studies of normal calvarial morphogenesis in human fetuses were found to support the concepts of Tondury and of Moss. The early growth and form of the brain causes growth stretch on the dura with the development of reflections which extend from the sites of dural attachment at the cranial base and conform to the major recesses in the early brain. The dura is the guiding tissue in the morphogenesis of the overlying calvarium and its major sutures, which develop from 10 to 16 weeks of fetal life. In the quiet zones between the dural reflections ossification occurs, whereas over the reflections of dura no ossification occurs, these being the sites of sutures. Supportive evidence for the role of the dural reflections in determining the sites of sutures was obtained from the evaluation of instances of major brain malformations which must have antedated calvarial morphogenesis. These included holoprosencephaly (13 cases), craniopagus (7 cases) and dicephaly (2 cases). In each case the gross brain malformation gave rise to unusual sites of dural reflection, which were found to coincide with the unusual sites of sutures in the calvarium. Furthermore, a lack of a dural reflection was accompanied by a lack of development of a suture at that site. The relevance of these findings to the evaluation of problems of brain morphogenesis and the diagnosis and management of craniostenosis will be discussed.