Patients Seven patients, three men; aged 21-50 years; average (std) 36.67 (±14.64), and four women; aged 28-46 years; average: 35.25 (±8.14), suffering from treatment-refractory obsessive compulsive disorder participated in this study. All patients scored 30 or higher in the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). They were considered as candidates to DBS for OCD by two independent psychiatrists. An independent psychiatric surgery committee composed of one neurosurgeon, one psychiatrist and one legal medicine expert agreed surgery indication was appropriate. All patients provided written informed consent. The study had approval from the Hospital Clínico San Carlos ethics committee.