Pathogenesis of craniosynostosis is poorly understood. Several different factors (primary fusion of a cranial vault suture, abnormal tensile forces acting on the cranial sutures, genetic control, fetal constraint) may be responsible for the malformation. Trigonocephaly is a relatively rare form of cranial malformation ranging from 5 to 20% of all the craniosynostotic syndromes. This form of craniosynostosis may be simple not associated with other cerebral defects or complex, associated with arhinencephaly and hypoplasia of frontal lobes; three gradations of malformation (marked, mild, incomplete) may be considered. A case of trigonocephaly associated with anterior basal meningocele is reported. The operative treatment and radiological findings are described. The pathogenetic role of the basal meningocele to determine the premature sutural fusion through tensile forces transmitted by abnormal dural attachments is evaluated.