Patient-specific, Effective, and Rational Functional Connectivity Targeting for DBS in OCD

Recently, deep brain stimulation (DBS) has emerged as a potentially circuit-specific treatment for intractable OCD. DBS is programmable, allowing the clinician to "reshape" the volume of tissue activated within the standard ventral capsule/ventral striatum (VC/VS) target. However, VC/VS DBS' efficacy is limited by two major factors: imperfect targeting and a lack of decision rules for stimulation adjustment. The VC/VS target is not a single identifiable structure, but encompasses white matter of the internal capsule and gray matter of the nucleus accumbens (NAc). In current practice for DBS in OCD, all patients are implanted at standard x,y,z coordinates in the VC/VS region. Due to this inter-subject anatomical variability, different fiber tracts are stimulated by ostensibly the "same" parameters in each subject, leading to variable outcomes. This investigation will identify aspects of VC/VS circuitry that may determine clinical response. The hypothesis is that good clinical outcomes may correlate to electrical field capture of either striatal gray matter or of white matter fibers connecting OFC to thalamus. The current study looks to extend the neuroimaging investigation using anatomic white matter targeting, functional gray matter targeting and changes in changes in regional glucose metabolism of Deep Brain Stimulation (DBS) in severe obsessive-compulsive disorder (OCD) with the long-term aim of identifying biomarkers that could improve outcomes of this expensive and invasive therapy. Improved imaging would allow surgeons to place the DBS lead closer to the biological targets, thus improving efficacy of the treatment. The objectives of this study are threefold: * Improve the anatomic white matter targeting of the Deep Brain Stimulator (DBS) implant by tracing and identifying fibers of passage within the Ventral Capsule (VC) white matter using advance tractography methods in preoperative diffusion MRI data. * Improve functional gray matter targeting by studying the overlap of the volume of tissue activated (VTA) with the VC voxels of maximal preoperative connectivity to the orbitofrontal cortex (OFC) * Determine the changes in regional glucose metabolism using preoperative and post-treatment FDG-PET (Positron Emission Tomography) following 3 months of DBS treatment