Obsessive-Compulsive Disorder (OCD) is among the most disabling psychiatric disorders as more than 40% of patients are resistant to the standard pharmacological and psychotherapy approaches and about 10% show severe disability and require institutionalization. These resistant patients may benefit from new surgical therapeutic approaches such as Deep Brain Stimulation (DBS) using high frequency stimulation of specific cerebral regions to modulate neural networks. Although promising, these results need nevertheless to be replicated and confirmed within a larger cohort of patients and considering a different main objective, instead of clinical improvement only. Indeed, despite a positive treatment response, adaptive functioning and quality of life may continue to be negatively impacted in OCD. Thus beyond symptom reduction, health-related quality of life (QoL) represents a more important objective of a treatment, as it includes both the individual's functional status and the individual's subjective perception of the impact of the illness on the patient's life. STN DBS induces significant clinical improvement, which may not be proportional to the QoL gain. Consequently, QoL appears to be a better outcome to target in the coming studies than clinical improvement alone. THe investigators thus propose a prospective study assessing the QoL changes of resistant OCD patients under STN DBS+BMT versus Best Medical Treatment (BMT) at 12 months, in order to assess the DBS induced gain in QoL in BMT-managed patients versus BMT alone.