Glucose Consumption During Deep Brain Stimulation With Functional [18F]FDG-Brain-PET in Obsessive-Compulsive Disorder

Inclusion Criteria: * a score of 25 or higher on the Yale-Brown Obsessive Compulsive Scale * previous failure to respond to at least two medication trials with serotonin reuptake inhibitors at or, if tolerated, beyond the FDA maximum recommended dose for a minimum duration over at least ten weeks each. * at least one trial with tricyclic medication at or, if tolerated, beyond the FDA maximum recommended dose for a minimum duration over at least ten weeks each. * at least one trial of augmentation with antipsychotic medication, lithium, a benzodiazepine or buspirone * at least on trial of psychotherapy (cognitive behavioral therapy or comparable techniques) for at least 20 sessions * ability to provide written informed consent Exclusion Criteria: * any history of current or past psychotic disorder * a manic episode within the preceding three years * any current clinically significant medical or neurological disorder, that is a contraindication against DBS * any disease that could lead to an altered glucose reactivity (e.g. diabetes) * any clinically significant preoperative MRI abnormality or inability to undergo presurgical MRI * current or unstable remitted substance abuse or dependence except nicotine * pregnancy or high risk of becoming pregnant during study duration (desire to have children) and refusal to utilize a proper method of contraception * Any current severe personality disorder except comorbid anankastic personality disorder * Inability to follow the study protocol or adhere to operational requirements * Current and unstable suicidality