Determination of cerebral blood flow by SPECT: a valuable tool in the investigation of dementia?

Positron emission tomography (PET) studies have demonstrated distinctive abnormalities in Alzheimer's disease (AD), multi-infarct-dementia (MID) and Pick's disease. Since PET is a complicated and expensive technique, its clinical application will be limited in the near future. An important finding in these PET studies is persistent coupling of brain metabolism and regional cerebral blood flow (rCBF). Therefore it should be possible to demonstrate bilateral temporoparietal hypometabolism as seen in patients with clinically diagnosed AD indirectly by measuring cerebral blood flow by Single Photon Emission Computer Tomography (SPECT). We report our first experiences with SPECT in the differential diagnosis of dementia with four case histories. We demonstrated temporoparietal hypoperfusion in AD and frontal hypoperfusion in Pick's disease as shown previously by PET. We could not demonstrate a typical SPECT in MID. The main purpose of SPECT in MID could be exclusion of coexisting AD. Based on current knowledge the possibilities and the limitation of this new technique are discussed. It is concluded that rCBF-SPECT may be of value in the diagnosis of AD and Pick's disease. Before this method can be used in daily clinical routine, its diagnostic value should be established according to principles of clinical decision making.