A Magnetic Resonance Spectroscopic Examination of Children and Adolescents Taking Riluzole for Obsessive-Compulsive Disorder

Background: * Obsessive-compulsive disorder (OCD) is a common childhood disorder that often does not respond to standard treatments. Researchers are exploring the role that a brain chemical called glutamate plays in symptoms of OCD, and are testing a drug called riluzole that reduces glutamate to see if changing the levels of glutamate in the brain will help treat the disorder. * Researchers are interested in using magnetic resonance spectroscopy (MRS), a type of magnetic imaging, to take pictures of various chemicals in the brain. MRS images will be used to detect changes in brain levels of glutamate in children taking riluzole. Objectives: \- To use magnetic resonance spectroscopy to study the levels of glutamate in the brains of children and adolescents who have been taking riluzole. Eligibility: \- Children and adolescents ages 7 to 17 who are enrolled in the current NIMH riluzole trial protocol (05-M-0225), who are able to lie still in the scanner for about an hour each time, and who are willing to have up to three MRS scans. Design: * Researchers will study some children/adolescents before they begin to take the study medication riluzole or placebo these children will have an MRS scan before starting the study medication. The scan will take about an hour. * About 2 weeks after reaching the full dose on the study medication, participants will have a second hour-long MRS scan. Participants will have a third MRS scan after being on the study medication for 12 weeks. * Some children who have already completed 12 weeks on riluzole or placebo, and are now taking riluzole, will have only one MRS scan.