Decrease in Caudate Glutamatergic Concentrations in Pediatric Obsessive-Compulsive Disorder Patients Taking Paroxetine

Objective To measure in vivo neurochemical changes in the caudate nucleus in pediatric obsessive-compulsive disorder (OCD) before and after treatment. Method Single-voxel proton magnetic resonance spectroscopic (1H-MRS) examinations of the left caudate were conducted in 11 psychotropic drug-naive children, aged 8 to 17 years, with OCD before and after 12 weeks of monotherapy with the selective serotonin reuptake inhibitor paroxetine (10-60 mg/day) and 11 healthy children aged 8 to 17 years. A different sample of 8 pediatric OCD patients and 8 healthy children had a 1H-MRS examination of occipital cortex. Results Caudate glutamatergic concentrations (Glx) were significantly greater in treatment-naive OCD patients than in controls but declined significantly after paroxetine treatment to levels comparable with those of controls, Decrease in caudate Glx was associated with decrease in OCD symptom severity. Occipital Glx did not differ between OCD patients and controls. Conclusions These preliminary findings provide new evidence of Glx abnormalities in the caudate nucleus in pediatric OCD and suggest that paroxetine treatment may be mediated by a serotonergically modulated reduction in caudate Glx.