Cerebral spect and Alzheimer disease: a revision

The Single Photon Emission Tomography (SPECT) is one of the recent neuroima ging techniques that contributes with information about the regional cerebr al blood flow (rCBF). The present paper presents a description of the SPECT methodology and reviews the contribution of cerebral SPECT studies in Alzh eimer's Disease (AD). Several studies have shown a pattern of bilateral par ietotemporal hypoperfusion in AD. This pattern of rCBF enables to distingui sh between AD and normal subjects with a sensibility of 70% to 100%, and a specificity of 87% to 100%. The SPECT is also a fundamental technique for t he differential diagnosis for AD and other dementias like vascular dementia , Parkinson's Disease, Huntington Disease and others. Several studies have shown an association between neuropsychological performance and rCBF, speci ally when studying patients with language impairments, apraxia, semantic me mory impairments and attentional deficits. SPECT imaging studies conducted while the patient is engaged in a cognitive task or under sensory stimulati on are referred to as activation studies. Activation studies afford unique opportunities to explore brain metabolic changes related to specific cognit ive operations and to establish hypothesis of the neural networks supportin g very discrete cognitive functions. We conclude that SPECT has the necessa ry potential to become a reliable diagnostic and research instrument for AD .