Changes in cerebral blood flow during cognitive activation evaluated by single photon emission computed tomography in patients with Alzheimer's disease

Regional cerebral blood flow (CBF) pattern evaluated by single photon emission computed tomography (SPECT) could be useful for the clinical evaluation of patients with Alzheimer's disease (AD). The aim of our study was to evaluate, using brain-dedicated SPECT and (99M)Tc-d, 1-hexamethyl propylene amine oxime ( 99mTc-HMPAO), CBF pattern in patients with AD in relation to the severity of the disease and also to verify possible CBF changes during a cognitive activation test. Twenty-four patients with AD were studied: relative CBF was assessed at rest and during a global cognitive stimulation test performed by inviting the patients to describe a vignette with many objects and people. CBF was compared with that observed in 10 age- and sex-matched controls. A heterogeneous pattern of CBF reduction was observed in patients with AD, particularly involving the temporal and parietal regions, unilaterally or bilaterally, proportionally to the severity of the disease. During the stimulation test CBF increased significantly only at the temporal and left precentral areas. In the left parietal region, CBF changes were related to resting values: the lower the CBF at rest, the smaller the increase in perfusion during the cognitive activation test.