HMPAO-SPECT Can Discriminate between Patients with Subjective Cognitive Complaints with and without Cognitive Deficits and those with Mild Cognitive Impairment.

BACKGROUND: Growing evidence suggests that pathological processes leading to Alzheimer's disease occurs gradually and begins to develop decades before the earliest clinical symptoms occur. The use of biomarkers has been proposed to detect evidence of preclinical Alzheimer's pathologic change in asymptomatic subjects. Subjective cognitive complaints (SCC) i.e. self-reported cognitive decline with normal cognition have been reported as an indicator of future cognitive decline, however, this condition is unspecific. OBJECTIVE: In the present study we used the regional brain perfusion measured by HMPAO-SPECT as Biomarker of neurodegeneration to compare the regional brain perfusion of patient with subjective cognitive complaints with and without minimal cognitive dysfunction (SCC+ and SCC- respectively) in respect to patients with mild cognitive impairment (MCI). METHODS: We retrospectively examined 736 Patients who referred to our Memory Clinic because of suspected cognitive dysfunction. After exclusion of patients with overt dementia, automated, quantitatively assessed relative cerebral blood flow of 10 forebrain regions (thalamus, parietotemporal, medial temporal, posterior temporal, posterior cingulate gyrus, each region left hemispheric and right hemispheric) and neuropsychological assessment of 64 SCC (32 SCC+; 32 SCC-) and 28 MCI subjects were analysed. RESULTS: .The most relevant differences between groups in cognitive performance concerned verbal memory. Left hemispheric medial temporal region could significantly discriminate between all three groups, with a progressive decrease n perfusion from SCC towards MCI. Area under the curve of left medial temporal region showed a sensitivity of 0,61 and a specificity of 0,78 for discriminating MCI from SCC. CONCLUSION: Automated analysis of HMPAO-SPECT data of MCI and SCC+ patients showed significant perfusion differences in medial temporal region and impaired verbal memory, both of which are known features of Alzheimer's disease. Perfusion patterns and verbal memory performance in SCC+ are more similar to MCI than SCC-. Thus, SPECT analysis could distinguish those subjects whose perfusion pattern resembles that of an MCI from those who do not. In our opinion, this could identify two populations with a different risk of progression to AD, with SCC+ subjects needing further diagnostic examination and repeated follow-up.

Brain perfusion SPECT in patients with mild cognitive impairment and Alzheimer's disease: comparison of a semiquantitative and a visual evaluation.

Due to the increasing importance of early recognition and differential diagnosis of dementias, cerebral perfusion scans using "single photon emission computed tomography" (SPECT) are increasingly integrated into the examination routine. The goal of this study was to check the diagnostic validity of SPECT scans of MCI- and DAT-patients, two subgroups out of 369 persons with etiologically unclear cognitive dysfunction, which underwent an assessment program for probable dementia including cognitive testing, cranial computed tomography, ultrasound, routine laboratory testing including vascular risk factors. After exclusion of patients with no or other forms of dementia we analyzed SPECT data of patients with mild cognitive impairment (MCI; n = 85) and dementia of the Alzheimer type (DAT; n = 78) in comparison with a healthy control group (n = 34).Visual assessment as well as a manual "regions of interest" (ROI) regionalization of the cortex were performed, whereby a ROI/cerebellum ratio was calculated as a semi-quantitative value. Association cortex areas were assessed regarding frontal, temporal, and parietal lobes of both hemispheres. When comparing the ratios of patients with DAT and controls, we found a statistically significant reduction of the cerebral perfusion in all measured cortex areas (p < 0.001). The comparison of patients with MCI with the selected control group also established a statistically significant difference in the cerebral perfusion for the evaluated cortex areas with the exception of the left hemispheric frontal and parietal cortex.A considerable number of the MCI patients showed an MMSE-score within the normal range, but with regard to the perfusion in the right hemispheric association cortex these patients also could be distinguished unambiguously from controls. Sensitivity levels found by visual assessment were at least as high as those found by the ROI method (pathological assessment: visual 49.4% vs. ROI 47.1% for MCI; visual 75.6% vs. ROI 73.1% for DAT). High experienced visual assessment of cerebral perfusion scans using SPECT provides an useful additional tool in diagnosis of cognitive impairment. The used semiquantitative ROI-method is nearly equivalent and does not depend on the experience of the investigator.