Obsessive-compulsive disorder (OCD) is a chronic and debilitating illness that affects between 2% and 3% of the adult population of the United States. People with OCD often experience persistent unwanted thoughts and carry out ritual-like behaviors to rid themselves of these obsessive thoughts. Additionally, OCD symptoms are usually tied with feelings of intense anxiety and functional impairment, making it important for people with OCD to seek effective treatment. Although there are currently many treatment options for OCD, including psychotherapy and medications such as serotonin reuptake inhibitors, between 40% and 60%of people with OCD only partially respond, or do not respond at all, to these treatment methods. Given the large percentage of people who do not respond to aggressive conventional treatments, alternative options are necessary for people with treatment-resistant OCD. Deep brain stimulation (DBS) is a procedure that involves the se of thin wires to carry electric current to parts of the brain associated with producing OCD symptoms. DBS has been effectively and safely used to treat movement disorders, such as Parkinson's disease, and may be beneficial in reducing OCD symptom severity. This study will evaluate the safety and efficacy of DBS in treating people with severe and treatment-resistant OCD.

Study participation through follow-up will last up to 2 years. Participants will be allowed to remain on any pre-surgical medications or behavioral therapy programs throughout the study. Before surgery, all participants will undergo a series of initial tests and examinations that will include psychiatric, medical, and neuropsychological histories and examinations.

Implantation of the devices will be performed at a single session. The leads that are inserted into the anterior limb of each internal capsule, will be implanted under local anesthesia. On the day of the surgery, participants will have a metal frame fixed to their heads for support during surgery, and magnetic resonance imagining (MRI) will be used to determine the exact placement of the wires. An extension wire will pass from the scalp area to the subclavicular region and connect each electrode to a subcutaneous implanted pulse generator (IPG), which will be implanted under general anesthesia. After placement of the DBS system, the patient will be admitted to the hospital for overnight observation for possible complications. Postoperative evaluation will consist of physical and neurological examinations, postoperative CBC, electrolyte panel, x-rays of the head, neck, and chest, a standard shunt series to ensure the integrity of connections, and a head CT scan to monitor for possible postoperative intracranial hemorrhage.

Surgical implantation will be followed by a three-week period with no stimulation, and then an intensive five-day preliminary outpatient stimulation trial, followed by longer-term outpatient stimulation. All patients will follow the same sequence of test conditions. The initial DBS testing will be open, followed by three blocks of testing in which the patients and investigators administering rating scales will not be informed of the stimulation condition. These three blocks will in general be three months long, but may be longer or shorter depending on the stability of any clinical improvement, and the possible emergence of symptom worsening. The remainder of the the study, up to the two-year study endpoint, will consist of a continuation phase of active open stimulation.