S. Hoyer – författare

Infirmity, that decays the wise, doth ever make the better fool William.Shakespeare, Twelfth Night 1,5 Since antiquity, it has been a dream of mankind to live in eternal youth and thus to attain longevity. Gods and heroes of the myths of many European cultures were always repre­ sented as young. Their youth was one of their most remark­ able attributes, and eternal youth given to a human being from a god was the greatest act of grace. This age old dream of mankind is demonstrated very graphically in one of the most impressive paintings of the Middle Ages, the famous "Jungbrunnen" (Fountain of Youth) by Lucas Cranach. During recent decades, progress in medical and social areas has increased life expectancy at least in the highly developed countries. Although this longevity does not mean eternal youth, it obviously fulfills the ancient desire of mankind. However, to live longer and longer and thus to become older and older also means to live in infirmity over a longer period of life. Ifprogress in medical science continues at the present rate, longevity will as seems inevitable, increase further. At least at this stage, problems of aging might become as important as problems of development.

Significant progress has doubtlessly been made in the field of cere­ bral protection compared to earlier centuries, as recently reviewed by Elisabeth Frost (6). She cites the recommendations for treat­ ment of brain trauma by Areteus, a Greek physician of the second century A. D. He expressed quite modem views with regard to the need for prompt action considering complications that follow even minor symptoms. He advised burr holes for evacuation of hema­ toma in seizures, the use of diuretics and, most interestingly, also hypothermia. German surgeons of the 17th century had little more to offer than prescriptions of which the most effective constituent was alcohol (10). Thus, Sir Astley Cooper was probably the next surgeon to make noteworthy contributions when advising the use of leeches to the temporal artery and other means of bleeding in­ stead of surgical intervention in cases of raised intracranial pressure (loc. cit. 6). Although our knowledge has greatly expanded during the last two decades, extensive discussions have led to only few conclusions. Promising results from animal studies were translated to clinical sit­ uations only to yield controversial and sometimes confusing results. Since the observations of Brierly (5) on ischemic cell damage, im­ proved information on structural aspects, probably even related to concomitant biochemical studies, should allow the validity of thera­ peutic concepts to be verified. Investigations on cerebral ischemia have led to the differentiation of synaptic transmission failure and membrane failure.

Significant progress has doubtlessly been made in the field of cere­ bral protection compared to earlier centuries, as recently reviewed by Elisabeth Frost (6). She cites the recommendations for treat­ ment of brain trauma by Areteus, a Greek physician of the second century A. D. He expressed quite modem views with regard to the need for prompt action considering complications that follow even minor symptoms. He advised burr holes for evacuation of hema­ toma in seizures, the use of diuretics and, most interestingly, also hypothermia. German surgeons of the 17th century had little more to offer than prescriptions of which the most effective constituent was alcohol (10). Thus, Sir Astley Cooper was probably the next surgeon to make noteworthy contributions when advising the use of leeches to the temporal artery and other means of bleeding in­ stead of surgical intervention in cases of raised intracranial pressure (loc. cit. 6). Although our knowledge has greatly expanded during the last two decades, extensive discussions have led to only few conclusions. Promising results from animal studies were translated to clinical sit­ uations only to yield controversial and sometimes confusing results. Since the observations of Brierly (5) on ischemic cell damage, im­ proved information on structural aspects, probably even related to concomitant biochemical studies, should allow the validity of thera­ peutic concepts to be verified. Investigations on cerebral ischemia have led to the differentiation of synaptic transmission failure and membrane failure.

At the present time several techniques are available for studying quantitatively global and regional blood flow and metabolism of the human brain. How­ ever, many scientists working in the clinical and research field who would like to use these tools for their investigations may be less familiar with the indi­ cations and limitations of the individual methods. The rapid development of both modern imaging techniques and new tracers may have led to some con­ fusion in answering the question as to which method is appropriate to solve the diagnostic problem of an individuum with brain disease. Scepticism and ignorance as to the methods to be used as tools in differential diagnosis of brain disorders may have prevented their widespread introduction into clinical practice. Thus, the significance of circulatory and metabolic parameters involved in the majority of diseases of the central nervous system may have been overlooked. The contributions compiled in this book describe in detail the individual techniques, outline their indications and limitations and deal in particular with newer methods such as the atraumatic 133Xe technique, stable xenon tomogra­ phy, three-dimensional techniques such as 133Xe single photon emission tomog­ raphy and N-isopropyl-P23-iodoamphetamine. Positron emission tomography studies provide information on function and metabolism, particularly that of oxygen and glucose, in regional brain areas of interest. Nuclear magnetic reso­ nance may be a promising method for studying metabolic parameters; however, accurate circulation measurements can not be performed at present.