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Signal Attenuation as a Rat Model of Obsessive Compulsive Disorder
Published on: January 9, 2015
Amygdala volume reductions in pediatric patients with obsessive-compulsive disorder treated with paroxetine:
Philip R Szeszko1, Shauna MacMillan, Marjorie McMeniman
1Department of Psychiatry Research, Zucker Hillside Hospital, North Shore - Long Island Jewish Health System, Glen Oaks, NY 11004, USA. szeszko@lij.edu
Insights
Obsessive-compulsive disorder (OCD) patients showed amygdala asymmetry. Paroxetine treatment, a selective serotonin reuptake inhibitor (SRI), reduced left amygdala volume, suggesting a role for amygdala changes in OCD pathophysiology and treatment response.
Area of Science:
- Neuroscience
- Psychiatry
- Radiology
Background:
- The amygdala's role in fear conditioning and its responsiveness to serotonin reuptake inhibitors (SRIs) suggest its involvement in obsessive-compulsive disorder (OCD) pathophysiology.
- Selective serotonin reuptake inhibitors (SRIs) are the primary pharmacotherapy for OCD.
Purpose of the Study:
- To investigate in vivo volumetric changes in the amygdala in pediatric OCD patients treated with paroxetine hydrochloride.
- To examine the relationship between amygdala volume changes and paroxetine dosage or cumulative exposure.
Main Methods:
- Magnetic resonance (MR) imaging (1.5 mm contiguous slices) was used to measure amygdala volumes in 11 drug-naive pediatric OCD patients before and after 16 weeks of paroxetine monotherapy.
- Eleven healthy pediatric comparison subjects underwent similar baseline and follow-up scans without medication.
Main Results:
- Pediatric OCD patients exhibited significant left-dominant amygdala asymmetry at baseline, unlike healthy controls.
- Following paroxetine treatment, a significant reduction in left amygdala volume was observed in OCD patients.
- This reduction in left amygdala volume correlated with higher paroxetine dosage and cumulative exposure.
Conclusions:
- Abnormal amygdala asymmetry may be implicated in the pathogenesis of OCD.
- Paroxetine treatment in pediatric OCD patients is associated with a decrease in left amygdala volume.
Abstract:
The amygdala is believed to be highly relevant to the pathophysiology of obsessive-compulsive disorder (OCD) given its prominent role in fear conditioning and because it is an important target of the serotonin reuptake inhibitors (SRIs), the pharmacotherapy of choice for OCD. In the present study, we measured in vivo volumetric changes in the amygdala in pediatric patients with OCD following 16 weeks of monotherapy with the selective SRI, paroxetine hydrochloride. Amygdala volumes were computed from contiguous 1.5 mm magnetic resonance (MR) images in 11 psychotropic drug-naive patients with OCD prior to and then following treatment. Eleven healthy pediatric comparison subjects also had baseline and follow-up scans, but none of these subjects received medication. Patients demonstrated significant asymmetry of the amygdala (L>R) prior to pharmacologic intervention in contrast to healthy comparison subjects who showed no asymmetry at the time of their baseline scan. Mixed model analyses using age and total brain volume as time varying covariates indicated that left amygdala volume decreased significantly in patients following treatment. The reduction in left amygdala volume in patients correlated significantly with higher paroxetine dosage at the time of the follow-up scan and total cumulative paroxetine exposure between the scans. No significant changes in either right or left amygdala volume were evident among healthy comparison subjects from the baseline to the follow-up scan. These preliminary findings suggest that abnormal asymmetry of the amygdala may play a role in the pathogenesis of OCD and that paroxetine treatment may be associated with a reduction in amygdala volume.
