[18F]FDG PET Study of Cerebral Glucose Metabolism in Obsessive-Compulsive Disorder

Kwon, Jun Soo; Lee, Dong Woo; Lee, Jae Sung; Choi, Jeong Im; Lee, Dong Soo; Jung, June Key; Cho, Maeng Je; Lee, Myung Chul; Lyoo, In Kyoon

Abstract

OBJECTIVE
Functional imaging studies on obsessive-compulsive disorder(OCD) subjects have repeatedly reported increased metabolism in orbitofrontal lobes and caudate nucleus, resulting in the "frontal-subcortical" circuit abnormality theory. Limitations of the previous studies to date include little consideration for the duration of illness, and the use of regions of interest methods, as an image analysis method. Our study objectives are 1) to include the duration of illness as an important study variable, and 2) to use Statistical Parametric Mapping(SPM) method in order to tap relations between the brain function and the psychopathology and symptoms of OCD. METHOD: The [18] fluorodeoxyglucose positron emission tomography(FDG-PET) scans of OCD subjects and normal comparison subjects, as diagnosed by the Structured Clinical Interview for DSM-IV(SCID-IV), were analyzed using SPM.
RESULTS
1) Comparison of OCD and control groups: OCD subjects had significantly decreased metabolism in both parietal lobes and didn't have any areas of increased metabolism in comparison to comparison subjects(p<0.01). Four OCD subjects with the illness duration of 10 years or longer, had significantly increased metabolism in both orbitofrontal lobes(p<0.01). OCD subjects whose illness duration is shorter than 10 years didn't have any areas of increased metabolism and had significantly decreased parietal lobe metabolism, as in the analyses of all subjects(p<0.01). 2) Correlation analysis between areas and symptom severity: Metabolism of both thalamic areas showed significant positive correlation with Yale-Brown Obsessive-Compulsive Scale(Y-BOCS) scores(p<0.01). Metabolism of right parietal area showed significant negative corre-lation with Y-BOCS scores(p<0.01).
CONCLUSIONS
The current findings suggest that the increased metabolism in orbitofrontal lobe, previously reported, may be a secondary phenomenon due to the extended illness duration and that decreased metabolism in the parietal lobes are primary abnormality in OCD subjects. Thus Baxter's fronto-subcortical circuit theory should be extended into "fronto-parietal" complex theory, which includes the parietal lobes.