Dose-dependent frontal hypometabolism on FDG-PET in methamphetamine dependent patients

Abstract

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Objectives: There are mounting evidences from neuropsychological and neuroimaging studies to support the view that patients with substance dependence have abnormalities in prefrontal cortex. However, functional deficits in prefrontal cortex have not been fully investigated in methamphetamine dependence. Therefore, the purpose of this study is to examine whether methamphetamine dependent patients have metabolic abnormalities and executive dysfunction.

Methods: Twenty-four abstinent methamphetamine dependent patients and 21 age-matched normal controls underwent resting brain FDG-PET and completed computerized versions of the Wisconsin Card Sorting Test (WCST). Brain PET images were obtained 30 minutes after intravenous injection of 370 MBq of 18F-FDG. Significant differences of glucose metabolism were estimated for every voxel using t-statistics on SPM2 implemented in Matlab.

Results: FDG-PET revealed significant hypometabolism in the left inferior frontal white matter (Talairach coordinates (x, y, z): -34, 7, 31) in methamphetamine dependent patients compared to the normal controls (corrected p<0.05, t>5.10). The nearest gray matter region was the left inferior frontal cortex (Brodmann area 9). There were negative correlations between the rCMRglc value in the left inferior frontal white matter and the total amount of methamphetamine (r=-0.57, p<0.01). Methamphetamine dependent patients completed significantly fewer categories (3.66±2.19) and made more perseveration errors (22.04±11.94) and total errors (44.57±19.70) on the WCST compared to the normal controls (p<0.01).

Conclusions: These data suggest that methamphetamine dependent patients have dose-dependent frontal hypometabolism and frontal executive dysfunction.