Case study: caudate glutamatergic changes with paroxetine persist after medication discontinuation in pediatric OCD.

Proton magnetic resonance spectroscopy (1H-MRS) was used to examine glutamatergic (Glx) abnormalities in the caudate nucleus in pediatric obsessive-compulsive disorder (OCD), associated with severity of illness and response to acute (12 weeks) treatment with paroxetine. In this report, OCD symptoms improved markedly in an 8-year-old girl treated for 14 months with the selective serotonin reuptake inhibitor paroxetine (titrated from 10 to 40 mg/day). Paroxetine dose was then decreased in 10-mg decrements and discontinued without symptom recurrence. Serial 1H-MRS examinations were acquired before and after 12 weeks of paroxetine treatment (40 mg/day) and 3 months after medication discontinuation. A striking decrease in caudate Glx was observed after 12 weeks of treatment which persisted after medication discontinuation. These data provide further support for a reversible glutamatergically mediated dysfunction of the caudate nucleus in OCD that may serve as a pathophysiological and treatment response marker.