Brain single photon emission computed tomography findings in depressive pseudodementia patients

Background: Recently, there have been studies suggesting that depressive pseudodementia would include early-stage dementing disorder. Through the comparison of the 99mTc-HMPAO single photon emission computed tomography (SPECT) image of depressive pseudodementia subjects, healthy comparison subjects, depressed subjects free of cognitive impairment, and dementia of Alzheimer’s type (DAT) subjects, we aimed to see part of pathophysiology of the depressive pseudodementia of elderly patients. Methods: Study subjects consisted of seven patients with depressive pseudodementia, seven healthy comparison subjects, seven patients with depression free of cognitive impairment, and eleven patients with DAT. Depression patients were diagnosed according to DSM-III-R. DAT patients were diagnosed by DSM III-R and NINCDS-ADRDA criteria of DAT. Other measures for assessment include Hamilton Rating Scale for Depression and Mini Mental State Exam. All underwent 99mTc-HMPAO SPECT scan. The images of each group were analyzed using statistical parametric mapping of Friston, which compares the images on voxel-by-voxel basis. Results: The results were as follows (1) The DAT group showed significant decreases of cerebral blood flow (CBF) in the right frontal, right temporal region, and both parietal regions as compared with control group (P<0.05). (2) The depression group showed a significant decrease of CBF in the left frontal region as compared with control group (P<0.05). (3) The depressive pseudodementia group showed significant decreases of CBF in both parietal regions as compared with control group (P<0.05). (4) The depressive pseudodementia group showed significant decreases of CBF in the right temporal region and both parietal regions as compared with depression group (P<0.05). (5) The DAT group showed significant decreases of CBF in the right temporal region, both frontal regions, and both parietal regions as compared with depressive pseudodementia group (P<0.05). Limitations: The small number of subjects may make it difficult to generalize from our results. Because decreased CBF in depressive pseudodementia is found while the subjects were depressed, we cannot tell whether it is a state marker or a trait marker. Conclusions: The depressive pseudodementia group showed decreased CBF in the temporo-parietal region, similar to that of the DAT group and different from that of the depression group.