Neurosurgery in Obsessive Compulsive Disorder:From targets to treatment to tracts and back again

People with obsessive compulsive disorder (OCD) suffer from obsessive thoughts and/or behavior, with a constant presence that can hardly be ignored. A range of interventions is effective in the management of OCD including behavioral therapy, cognitive therapy and cognitive behavioral therapy (CBT). In addition, a large body of evidence advocate on the use of selective serotonin reuptake inhibitors (SSRIs) and clomipramine, a tricyclic antidepressant, in the treatment of OCD, often used in combination with CBT. However, 40-60% of patients remain treatment-refractory, defined as a less than 25% reduction in Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) score. This scale is used to determine the severity of the disorder. The resistance of such a big amount of patients to therapy may urge the need for alternative treatment strategies, such as deep brain stimulation (DBS) of subcortical structures or gamma knife ventral capsulotomy (GVC), a noninvasive procedure using gamma rays to destroy certain brain tissues. The first part of this thesis aimed at identifying fiber bundles associated with clinical response to DBS or GVC. OCD patients consistently underperform across multiple cognitive domains. The second part of this thesis was focused on the neuropsychological outcome of OCD DBS in order to identify a cognitive pattern associated with a good outcome or that would (in part) help explain the functional mechanism of OCD-DBS. The third part focused on several postoperative aspects of (OCD)-DBS patients including surgical and hardware related adverse events of DBS and reviewing the effectiveness, timing and procedural aspects of CBT after DBS with the aim to provide clinical recommendations