[Contribution to the knowledge of the "periostitis ossificans interna" of the cranial vault (author's transl)].

An unusual observation of hyperostosis of the frontal bone exhibiting five alternating layers of compact and cancellous bone on cross section is demonstrated. The peculiar, hitherto not described hyperostosis occurred in an 18 year old female suffering from recurrent chronical pachy- and lepto-meningitis since birth. A second similar observation was made in a 15 year old male, trepanated because of an epidural abscess. Similar accessory layers of cancellous bone on the internal surface of temporal bone suggested that also the first observation had to be interpreted as an unusually extensive form of periostitis ossificans, only involving the frontal bone, due to the recurring inflammation processes of the meninges.