A research study of the effectiveness and safety of gamma knife ventral capsulotomy in patients with severe intractable obsessive-compulsive disorder (OCD).

Inclusion Criteria:

1. OCD, diagnosed by Structured Clinical Interview for DSM-IV (SCID-IV), judged of disabling severity with a Yale-Brown Obsessive Compulsive Scale (YBOCS) score of at least 30 and a Social and Occupational Functioning Assessment Scale (SOFAS) score of 45 or less.
2. Persistence of severe symptoms and impairment for five or more years despite: 1. at least three adequate (≥3 months at the maximum tolerated dose) serotonin transporter inhibitor trials (fluoxetine, sertraline, fluvoxamine, paroxetine, citalopram, escitalopram, or clomipramine) alone or in combination with, 2. adequate behavior therapy (≥20 sessions of expert exposure and response prevention), and 3. augmentation of one of the selective SRIs with clomipramine, a neuroleptic, and clonazepam.
3. Age between 18 and 65 years.
4. Able to understand and comply with instructions.
5. Able to give fully informed, written consent in the judgment of the Consent Monitor.
6. Either drug free or on a stable drug regimen for at least 6 weeks.
7. Good general health.
8. A family member or significant other is available and willing to communicate with the research team if the patient's clinical status worsens.
9. The local referring psychiatrist is willing to provide ongoing care.

Exclusion Criteria:

1. Current or past psychotic disorder.
2. Full-scale IQ below 85.
3. A clinical history of bipolar mood disorder.
4. Any current clinically significant neurological disorder or medical illness affecting brain function, other than tic disorders or Tourette syndrome.
5. Any clinically significant abnormality on preoperative magnetic resonance imaging (MRI).
6. Inability to undergo presurgical MRI (cardiac pacemaker, pregnancy, metal in body, severe claustrophobia.
7. Current or unstably remitted substance abuse, dependence, or a positive urine toxicology screen.
8. Pregnancy and women of childbearing age not using effective contraception.
9. Unable to adhere to operational and administrative study requirements (in the investigators' judgment).
10. Clinical history of severe personality disorder.
11. Imminent risk of suicide (in the investigators' judgment).

Open Label