Operations in the skull base area are performed by neurosurgeons, ear-nose- and throat physicians and ophthalmologists, as well as by facial surgeons, since the skull base is characterized as a transition area of intracranial space, sinuses and orbitae. In this volume the areas of neurosurgical interest to be covered are basically limited to intra- and extradural relations of dura, cranial nerves and brain. Some of these operative procedures may be carried out in cooperation with colleagues in related fields, as when sinuses or orbitae are opened. Other operations, for example those in the area of A. carotis int. path within Os petrosum, are left completely to specialists in other fields, since the neurosurgeon rarely has sufficient experience in the problematic anatomical topographical relations of the skull base.