Deep Brain Stimulation (DBS) for Obsessive Compulsive Disorder (OCD): Improving Targeting Precision

Inclusion Criteria: * Diagnosis of OCD following the diagnostic and statistical manual of mental disorders-fourth edition (DSM-IV) criteria for OCD (300.3). * Failure of documented trials of pharmacotherapy, following an appropriate treatment algorithm for OCD. * Failure of documented trial of cognitive and behavioural therapy * Duration of illness: min. 5 year * Y-BOCS (Yale-Brown Obsessive Compulsive Scale) at least 30/40. * Age: 20-65 year Exclusion Criteria: * DSM-IV diagnosis on axis 2 of severe personality disorder in cluster A or B, especially in the case of heightened risk for acting-out behavior. * DSM-IV diagnosis on axis 3 of organic brain pathology or significant abnormalities on MRI. * Present or past history of psychotic symptoms. * Present substance abuse, or instable remission of substance abuses (i.e. no substance abuse during the last 12 months). * Any disorder affecting cognitive functioning, other than motor tics and Gilles de la Tourette's Syndrome * Mental retardation. A minimum threshold of cognitive skills is needed for adequate reporting on questionnaires and evaluation, and for technical handling of the instruments in a later faze.