This volume is dedicated to the Third International Symposium on Microneurosurgical Anastomoses for Cerebral Ischemia, which took place in Rottach-Egern, June 2&-30, 1976, under the sponsorship of Professor F. Marguth, Director of the Depart ment of Neurosurgery, Ludwig-Maximilians-University of Munich (West Germany). It contains the continuing devel opments of the extra- intracranial arterial bypass (EIAB) for cerebrovascular occlusive disease since the First International Symposium in Lorna Linda, California, in June, 1973, and the Second International Symposium in Chicago, Illinois, in June, 1974. The EIAB was developed by Donaghy and Yasargil, and it consists of a microsurgical anastomosis of the superficial tem poral artery or the occipi tal branch of the external carotid artery to the middle cerebral artery on the surface of the brain and, very recently, the anastomosis of the occipital artery to the posterior-inferior cerebellar artery for the treatment of verte brobasilar insufficiency. From the presentations at the sym posium it became evident that the greatest potential in the pre vention of a stroke in a susceptible patient is the presence of an adequate collateral cerebral blood flow. The basic diagnostic procedure is cerebral angiography in cluding both carotid and vertebral arteries. Regional cerebral blood flow (rCBF) studies and computerized tomography add further diagnostic information and are particularly important in the selection of potential surgical candidates.

A decade has passed since systematic studies were initiated in the USA in an attempt at establishing the experimental basis for a surgical technique which was to prove an effective tool in combatting one of the most common diseases, i.e. cerebrovascular accidents. The development of such intricate vasculosurgical techniques as are required for extra intracranial arterial bypass operations would not have been possible without the aid of the surgical microscope, which had been designed some years earlier. In the past few years increasing emphasis has been placed on establishing clear-cut indications for the bypass operation, because satisfactory long-term results are unlikely to be obtained without them. Needless to say that this requires a close cooperation of the neurosurgeon with a team composed of neurologists, internists, radiologists, and pathologists. Fortunately enough, cooperation between the services of the University of Vienna Medical School proved to be exemplary. While there has been no lack of efforts by major medical centers both in Europe and the overseas countries to perfect bypass operations for cerebrovascular accidents, a comprehensive monograph reviewing all medical and operative problems involved in microvascular surgery for strokes was badly missed by many.

This 13th volume of Advances in Neurosurgery presents thos.e papers held at the 35th Annual Meeting of the German Society of Neurosurgery in Hannover, June 13-16, 1984. Of 150 papers submitted, the program com mittee of the Society chose 69 for presentation. I would like to thank Professors Bock, Brock, Jensen, Wenker, and Wlillenweber for their as sistance in the selection. It was the intention of the President of the Congress at this meeting to lay special scientific emphasis on discussion. For this reason the number of papers had to be limited even more than usual in order to give all participants the opportunity for questions and the presenta tion of their own experience. The main topic of the first day was Extra-Intracranial Anastomoses. Here the operative experience and the long-term results of these operations in the German-speaking countries were reviewed. This discussion was preceded a day earlier by a satellite symposium on the possibilities of the prophylaxis and treatment of ischemic neurological deficits fol lowing subarachnoid hemorrhage by means of calcium antagonists. Microsurgery at the Edge of the Tentorium was the second main topic. In co operation with the SOCiety's microneurosurgery working group, only a small number of lectures were planned, but the topic was covered thor oughly in a round-table discussion.

In June 1973, Professor George Austin invited a small group of neuroscientists from Asia, Europe, the United States, and Canada to the Loma Linda University School of Medicine in Loma Linda, California. The fundamental technique of fashioning a small vessel collateral to the brain had been pioneered by Donaghy and Yasargil 5 years before and was now gaining momentum with the increased availability of the operating microscope, fine instruments and sutures, and surgeons trained in microvascular surgery. The interchange of ideas at this first conference was magic. The handful of participants returned home stimulated with new ideas of technique, patient selection, and postoperative evaluation and resolved to meet again on a regular basis. A Second International Symposium was hosted by Howard Reichman at Loyola University in Chicago, Illinois in June of 1974; a Third Symposium at Rottach-Egern, West Germany in June of 1976 under Professor F. Marguth of the Ludwig-Maximilians-University of Munich.