Measurement and imaging of cerebral function in ageing and dementia.

Publisher Summary There has been considerable interest in the measurement of cerebral energy metabolism in the dementing diseases since such measurements became possible in man in the 1940's. As the patterns of metabolic dysfunction were identified, the relationship of changes in normal ageing to pathological processes became a field of primary interest. This was paralleled by the elaboration of sophisticated techniques for measuring cerebral flow and glucose metabolism in animals with a very high degree of regional precision, using autoradiographic techniques. Various animal models of ageing have subsequently been studied. Anatomical localization in human studies advanced dramatically with the application of tomographic reconstruction techniques to imaging by transmitted (X-ray) or emitted (γ-ray) radiation. The advent of tomography to radioisotope imaging has resulted in the elaboration of sophisticated techniques, using positron-emitting isotopes of biologically important elements, such as carbon, oxygen and nitrogen, designed to quantitate various physiological and biochemical functions. Positron-emission tomography (PET) has developed into a technique for applying quantitative tracer methodology to investigate cerebral function regionally in man. The problems of energy metabolism, a crude and indirect non-specific marker of neuronal damage, have largely been answered in dementia. Of therapeutic importance is the demonstration that vasodilator drugs have no physiological basis for their use in the management of dementing disorders, but that certain highly selected and rare patients with obstructive vascular disease as a cause of dementia may benefit from reconstructive vascular surgery.