Deconstructing a common pathway concept for Deep Brain Stimulation in the case of Obsessive-Compulsive Disorder

Deep Brain Stimulation (DBS) is a therapeutic option for treatment resistant (TR) obsessive-compulsive disorder (OCD). The OCD network comprises different sub-networks with homeostatic functions, altered under disease and modifiable with DBS. Connectomic analyses of DBS data sets have defined fiber selections explaining anti-OCD efficacy. This is a retrospective stimulation and outcome derived anatomical overlay analysis of 26 TR-OCD patients who received DBS at two academic centers. Grenoble, 14 anteromedial subthalamic nucleus (amSTN); Freiburg, 12 superolateral medial forebrain bundle (slMFB). Yale-Brown Obsessive Compulsive Scale improvement at 24 months served as outcome parameter. Structural proximity and outcomes were correlated using individual volumes of activated tissue for STN, slMFB, ORT (average OCD response tract) and further structures based on atlases or established connectomes. Connectomes (slMFB, ORT) were inspected for structural congruences. Normative connectomic data served to investigate cortical fiber penetration for the two target regions. Cortical sub-network conjugations were evaluated as peak levels. Our analyses revealed that ORT represents a fiber selection from the slMFB. DBS of amSTN and slMFB each address distinctive sub-networks while deep amSTN DBS can also address slMFB. Sub-network conjugations project amongst other regions onto the dorsomedial prefrontal cortex (dmPFC). The average ORT fiber selection is an integral part of the generic slMFB. Anti-OCD effects of amSTN DBS are not entirely explained by ORT overlay. The slMFB is dispersed and encompasses all OCD sub-networks and might qualify as a common DBS target when stimulated close to the ventral tegmental area. The dmPFC emerges as an interesting conjugation/hub between OCD sub-networks.