Patients with intractable Obsessive-Compulsive Disorder (OCD) receiving therapeutic gamma knife capsulotomy will improve more when capsulotomy produces greater interruption in connections between thalamic nuclei and orbitofrontal regions (Brodmann areas 12 and 13) on diffusion tensor MRI (DT-MRI).
To determine how the therapeutic effects of gamma capsulotomy relate to changes in the structure of the thalamus-prefrontal cortex pathways with a new neuroimaging technique called diffusion tensor MRI. The researchers predict that changes in the connections between the thalamus and the orbitofrontal cortex in the brain, which will be visible on DT-MRI but not on conventional MRI, will underlie capsulotomy's therapeutic benefit in OCD. Understanding the changes after surgery that result in the best therapeutic outcomes will allow for the improvement of capsulotomy as a treatment for this debilitating disease. With this information, researchers can refine the targeting of capsulotomy for individual patients, and possibly aid the development of a newer treatment, deep brain stimulation, for intractable OCD. Researchers may also learn more about how the same brain circuits are involved in other psychiatric disorders commonly associated with OCD.
Participants will be adults, ages 18-65, with OCD of disabling severity, refractory to prolonged treatment attempts with conventional medication and behavioral therapies, who have elected to undergo gamma capsulotomy under separate ongoing IRB-approved protocols at Brown University/Butler Hospital. Using a stereotactic frame within the Leksell gamma knife, pairs of lesions, each approximately 4 mm in diameter, are made in the entire ventral half of the anterior limb of the internal capsule at a standard distance rostral to the anterior commissure. Lesion placement is subsequently assessed by conventional MRI obtained 3 months postoperatively. Serial DT-MRI images and symptom ratings will be acquired at presurgical baseline and at 3, 6, and 12 months postsurgery.