Correlation of changes of regional cerebral blood flow with cognitive decline in patients with schizophrenia

Abstract

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Objectives: Impairment of cognitive function is increasingly recognized as a core feature of schizophrenia but the results of the study on brain regions related with cognitive dysfunction were inconsistent. We sought to evaluate brain regions related with cognitive decline using IQ reduction (the difference between current IQ and estimating premorbid IQ) in schizophrenic patients. Methods: A total of 21 patients who met DSM-IV diagnostic criteria for schizophrenia and schizoaffective disorder were selected. To assess general intelligence, the Korean-Wechsler Adult Intelligence Scale (K-WAIS) was administered as a standardized cognitive test. The full scale IQ score of K-WAIS was calculated based on performance of all 11 subtests according to age based norms. All patients underwent 99mTc-ECD brain perfusion SPECT. We applied an analysis of covariance to identify correlation patterns using Statistical Parametric Mapping software. We used a cognitive decline index, which was defined as the difference between scores of estimating premorbid IQ and current IQ, as covariates and age and duration of illness as nuisance variables. Only clusters of at least 10 voxels were reported (p < 0.01, uncorrected for multiple comparisons). Results: A statistical result showed a significant difference between current IQ and premorbid IQ (p < 0.05). A positive correlation between cognitive decline index and regional cerebral blood flow was observed in the left precuneus (Brodmann’s area; BA7), inferior parietal lobule (BA40) and right postcentral gyrus (BA3), precentral gyrus (BA6) and bilateral putamen. We also found a negative correlation in the bilateral cingulate gyrus (BA31), bilateral fusiform gyrus (BA37), left inferior gyrus (BA37), and left middle temporal gyrus (BA20). Conclusions: These findings suggest that cognitive decline in patients with schizophrenia is positively correlated with the parietal regions which were associated with working memory.