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

Objective

Although a lot of evidence from neuropsychological and neuroimaging studies supports the view that patients with substance dependence have abnormalities in the prefrontal cortex, functional deficits in the prefrontal cortex have not been fully investigated in methamphetamine (MA) dependent patients. This study was prepared to examine whether MA abusers have cerebral metabolic abnormalities and executive dysfunction.

Method

Twenty-four abstinent MA dependent patients and 21 age-matched control subjects underwent resting brain FDG-PET and completed computerized versions of the Wisconsin card sorting test (WCST). Resting brain PET images were obtained 30 min after an intravenous injection of 370 MBq of ¹⁸F-FDG. Significant differences in glucose metabolism were estimated for every voxel using t-statistics on SPM2 implemented in Matlab.

Results

Resting brain FDG-PET revealed significant hypometabolism in the left inferior frontal white matter (Talairach coordinates (x, y, z): −34, 7, 31) in MA dependent patients compared to the control subjects (corrected p = 0.001, peak Z = 5.37, voxel number 201). The nearest gray matter region was the left inferior frontal cortex (Brodmann area 9). There were negative correlations between the relative regional cerebral metabolism for glucose (rCMRglc) in the left inferior frontal white matter and the total cumulative dose of MA (r = −0.57, p < 0.01). MA dependent patients completed significantly fewer categories (3.8 ± 2.2) and made more perseveration errors (21.3 ± 11.8) and total errors (43.5 ± 19.5) on the WCST when compared to the control subjects (p < 0.01).

Conclusions

These data suggest that MA dependent patients have dose-dependent frontal hypometabolism and frontal executive dysfunction.