Linear Accelerator Radiosurgical Anterior Capsulotomy With Task-based fMRI Identification of PERSonalized and PrEdictiVE Biomarkers of REsponse in Treatment-Refractory Obsessive-Compulsive Disorder (PERSEVERE Trial)

One treatment for treatment-refractory OCD is a procedure called anterior capsulotomy, which modifies a part of the brain called the anterior limb of the internal capsule (ALIC). The ALIC contains connections between some regions of the brain that are overactive in OCD. Anterior capsulotomy can be done with a minimally invasive procedure called radiosurgery, which uses a one-time targeted radiation treatment to weaken the hyperactive connections that travel through the ALIC. Traditionally, radiosurgery was done using a machine called the Gamma Knife. Many radiation treatment centers use a different type of treatment machine, called a linear accelerator, to treat conditions in the brain that were traditionally treated on the Gamma Knife. This study will enroll 10 patients and offer anterior capsulotomy on a linear accelerator radiosurgery system and monitor participants OCD symptom improvement after the procedure. This study will also use a special type of brain imaging technique, called task-based functional MRI, to collect information about brain activity before and after treatment.

Inclusion Criteria: * Age 18 or older at time of enrollment * Documented diagnosis of Obsessive Compulsive Disorder (OCD) * Y-BOCS score of 28 or higher confirmed with behavioral testing during pre-existing clinical documentation * Two trials of selective serotonin reuptake inhibitors for an adequate duration at maximally tolerated dose OR one trial of a selective serotonin reuptake inhibitor with antipsychotic augmentation for an adequate duration at maximally tolerated dose OR one trial of a selective serotonin reuptake inhibitor and clomipramine for an adequate duration at maximally tolerated dose * Nonresponse to at least one trial of Exposure-Response Prevention behavioral therapy for an adequate duration. * Patient able to understand written and spoken English Exclusion Criteria: * Patient has prior ablative procedure to the brain (radiofrequency ablation, thermal ablation, laser interstitial thermal therapy, high-frequency ultrasound) * Patient has MRI contraindications (cardiac implantable electronic devices, metallic intraocular foreign bodies, implantable neurostimulation systems, cochlear or ear implants, and drug infusion pumps) * Pregnant women are excluded from this study. * Patient has prior diagnosis of brain tumor * Patient has active suicidal thoughts as assessed by a mental health professional * Patient has comorbid neurodegenerative disorder * Patient has history of substance use disorder in the past 24 months * Patient deemed by study investigator to lack capacity to provide informed consent.