Changes in Cerebral Cortex and Limbic Brain Functions after Short-Term Paroxetine Treatment in Panic Disorder: An [(18)F]FDG-PET Pilot Study

OBJECTIVE: Panic disorder (PD) is a common and often chronic psychiatric illness, and serotonin-specific reuptake inhibitors (SSRIs) are the drugs of choice for the treatment of PD. Previous studies suggested the cerebral cortex and limbic brain structures played a major role in the development of PD, but the therapeutic effect of SSRIs on specific brain structures remains unclear in PD. We examined the changes in PD patients' glucose metabolism using the [(18)F] Fluorodeoxy-glucose-positron emission tomography (FDG-PET) before and after 12 weeks of paroxetine treatment. METHODS: We assessed the brain glucose metabolism of 5 PD patients, using the [(18)F]FDG-PET, and treated them with paroxetine (12.5-37.5 mg/day) for 12 weeks. Then, we compared before and after treatment PET images of the patients, using voxel-based statistical analysis and a post hoc regions of interest analysis. Furthermore, we measured the patients' clinical variables, including information from the Panic Disorder Severity Scale (PDSS), Clinical Global Impression for Severity (CGI-S), and Hamilton Anxiety Rating Scale (HAMA). RESULTS: After 12 weeks of paroxetine treatment, the patients showed significant clinical improvement in terms of PDSS, CGI-S and HAMA scores (12.8±1.8 vs. 3.8±2.3, 4.6±0.5 vs. 2.0±1.4, and 15.2±4.0 vs. 5.0±1.2, respectively; all p values<0.05). After treatment, patients' glucose metabolism increased significantly in global brain areas: the right precentral gyrus, right middle frontal gyrus, right amygdala, right caudate body, right putamen, left middle frontal gyrus, left precentral gyrus, left insula, left parahippocampal gyrus, and left inferior frontal gyrus (All areas were significant at uncorrected p<0.001 and cluster level corrected p<0.05). CONCLUSION: In these PD patients, cerebral cortex and limbic brain functions changed after short-term treatment with paroxetine. The therapeutic action of paroxetine may be related to altered glucose metabolism at both the cerebral cortex and limbic brain areas.