[Circumscribed changes in the cranium due to extracerebral fluid collection in the middle cranial fossa]

On the basis of 26 cases with extracerebral fluid accumulation in the middle cranial fossa the bony changes occurring in this connection are described and discussed in respect of their aetiology. If there are bony accompanying reactions, two entities can be observed in principle. One group shows thinning and protrusion of the temporal squama, raising of the lesser wing of the sphenoid bone and protrusion of the greater wing of the sphenoid bone. The second group is associated with thickening of the temporal squama and of the lesser and greater wing of the sphenoid bone without showing any change in volume of the middle cranial fossa. If we postulate in the first group a space-occupying property of the extracerebral fluid accumulation, the prominent reactions in the second group are those usually associated with absence of pressure exercised on the cranial vault by a space-occupying growth.