Tc-99m-HMPAO neuroactivation SPECT in patients with Alzheimer's disease

Aim: Tc-99m-HMPAO-SPECT detects the hypoperfusion areas in the temporal and parietal lobes as well as in the frontal lobes in the advanced stages of Alzheimer's disease. These hypoperfusion areas correlate with decreased glucose metabolism and oxygen utilization. The aim of the study was to establish the neuroactivation effect on the regional cerebral blood flow and on the hypoperfusion areas detected by means of Tc-99m-HMPAO-SPECT in patients with Alzheimer's disease. Materials and methods: Subject to the study were 22 patients with Alzheimer's disease divided into two groups according to the results from the neuropsychological tests as follows: Ist group - 10 patients with slight cognitive disturbances; IInd group - 12 patients with prominent cognitive impairment. All patients underwent Brain-SPECT after I.V. injection of 740 MBq Tc-99m-HMPAO at rest and during neuroactivation by labyrinth task on the next day. Regional blood flow was detected by means of the hypoperfusion indices calculated as follows: hypoperfusion areas in the temporal lobe and /or the parietal lobe to the referent areas of the cerebellum. The regional blood flow decrease in hypoperfusion areas was calculated in per cent. Results: Hypoperfusion areas were detected at rest in 5 patients from the Ist group and in all patients from the IInd group. A decrease of the regional cerebral blood flow by 5-10% was established after neuroactivation in all the seventeen patients with hypoperfusion areas at rest. After neuroactivation three of the patients with normal regional cerebral perfusion at rest revealed hypoperfusion areas in the posterior part of the parietal lobe and the temporo-parietal areas. The remaining two patients showed normal regional cerebral blood flow at rest and during neuroactivation. Conclusion: Neuroactivation reduces the regional cerebral blood flow in hypoperfusion areas at rest in patients with Alzheimer's disease. Neuroactivation Tc-99m-HMPAO SPECT is useful for the detection of hypoperfusion areas which cannot be visualized at rest