The main aim of this study is to define the clinical criteria which must be considered in order to come to an adequate decision whether a patient with intracranial arteriovenous malformation (AVM) should be operated upon or treated conservatively. A special method was used to reduce the effects of selection. This method made it possible to evaluate the therapeutic efficacy of conservative treatment versus surgery. The method implies that patients with equal combinations of variables (risk profiles) were compared in the two treatment lines. The variables building up the risk-profile pattern were chosen by analysing the decision process, as it was originally practiced by the surgeon who selected and treated the patients of this study. The risk profiles thus described relevant characteristics of the patient and his malformation. The variables were assigned numerical values accord ing to their prognostic value. Summation of the variables making up the risk profile then gives each risk profile a certain value. A low value symbolizes a bad prognosis and a high value a good prognosis in both treatment groups. There were many risk profiles with the same value in both groups and a comparison could be made over a large part of the risk-profile scale. This comparison showed that surgical treatment of A VM can always be justified, although the indications for surgery are less strong in patients with low risk profile values."

The Committee of Neurotraumatology of the World Federation of Neurosurgical Societies decided to elaborate a Glossary of Neuro- traumatology, and for this purpose appointed a subgroup of members of this Committee, headed by Dr. E. S. Gurdjian, whose report follows this preface. The main reason for the Committee's decision was the hope that the diffusion of the Glossary through "Acta Neurochirurgica" may bring about a better understanding of neurotraumatological terminology on a worldwide scale. The Glossary should facilitate the classification and the comparison of traumatic lesions of the Nervous System. It will consequently be easier to compile statistics and correctly interpret the informations thus obtained. The very commendable initiative of the Congress of Neurological Surgeons in revising the terminology of head injuries and in publishing this work in Vol. 12 (1966) of "Clinical Neurosurgery" constitutes an important contribution. In 1977 the Glossary now presented endeav- ours to complete and bring up to date the definitions of anatomical or physiological modifications in the neurotraumatological field. We wish to express our thanks to Dr. Gurdjian and to the other members of the Neurotraumatological Committee who were responsible for the elaboration of this Glossary and whose efforts to standardise, as much as possible, the language used by scientists of different nationalities, have resulted in a better understanding between neurosurgeons.