EPENDYMOBLASTOMA IN THE FOURTH VENTRICLE, WITH NEW BONE FORMATION

The presence of newly formed bone in the cranial cavity is apparently rare except in the meninges and falx, where deposition of calcium and ossification frequently have been reported.¹The formation of bone within the brain itself is extremely uncommon. In the older literature a few reports of "osteoma" of the brain may be found,²but recently there has been a tendency to abandon the term osteoma because of the difficulty of deciding when bone is neoplastic.³From a study of the available reports, formation of new bone would seem to occur within the brain substance under three sets of conditions: Calcification and ossification of intracerebral hemorrhages and scars apparently may occur rarely. Brunner,4 Leriche and Policard5 and Berner^3bhave reported cases of this kind. There is, however, always some doubt whether the meninges participate in the formation of bone, especially in those cases in which trauma