FDG-PET scans used to assess OCD patients

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The rapid response of obsessive-compulsive disease (OCD) to intensive cognitive-behavioral therapy (CBT) is mediated by a distinct pattern of changes in regional brain function, according to the Jan. 8 issue of the Journal of Molecular Psychiatry.

S. Saxena, MD, department of psychiatry, School of Medicine, University of California, San Diego in La Jolla, Calif., and colleagues, sought to elucidate the brain mediation of response to brief intensive CBT for OCD and determine whether the treatment could induce functional brain changes previously seen after longer trials of pharmacotherapy or standard CBT.

Cerebral glucose metabolism was measured with [18F]-fluorodeoxyglucose (FDG)-PET in all subjects before and after 4 weeks of intensive, daily CBT.

PET brain scans were obtained on 10 OCD patients before and after four weeks of intensive individual CBT, and 12 normal controls were scanned twice, several weeks apart, without treatment, according to the researchers. Normal controls were scanned before and after 10–12 weeks without any treatment, to control for the effects of habituation to the scanning procedures and environment on brain metabolism.

The regional glucose metabolic changes were compared between groups. OCD symptoms, depression, anxiety and overall functioning improved robustly with treatment, the authors reported. Significant changes in normalized regional glucose metabolism were seen after brief intensive CBT, the authors wrote.

Compared to controls, OCD patients showed significant bilateral decreases in normalized thalamic metabolism with intensive CBT but had a significant increase in right dorsal anterior cingulate cortex activity that correlated strongly with the degree of improvement in OCD symptoms, according to the researchers.

The reduction of thalamic activity may represent a common pathway for improvement in OCD, but response to intensive CBT may require activation of dorsal anterior cingulate cortex, a region involved in reappraisal and suppression of negative emotions.