24 Chapter 1 Because of the involvement of the reward-related neurocircuitries described above, the areas communicating between the limbic and the cortical systems , such as the nucleus accumbens (NAc) and the cingulate and insular cortices (41, 85) may be of particular interest as possible target areas for future neurosurgical interventions. DEEP BRAIN STIMULATION Deep brain stimulation (DBS) is an innovative and promising approach for the treatment of patients with treatment-refractory reward-related psychiatric disorders (86-89). DBS is a reversible and adjustable neurosurgical treatment involving the implantation of electrodes that send electrical impulses to specific locations in the brain, selected according to the type of symptoms to be addressed and its putative neuroanatomical correlates (90, 91). Our center has experience with DBS in OCD, addiction, and major depressive disorder. In all these disorders, DBS targets reward related brain areas such as the NAc and the ventral capsule/ventral striatum (VC/VS). Target selection has evolved based on clinical results from earlier ablative procedures and DBS-studies, neuroimaging studies and theoretical considerations regarding the implicated neurocircuitries involved in these disorders (86, 88, 89, 92). The current working hypothesis is that DBS inhibits or functionally overrides pathological network hyperactivity in several treatment-resistant psychiatric disorders. Our research group showed efficacy for DBS in OCD targeted at the NAc normalizing NAc activity, reducing excessive connectivity between the NAc and prefrontal cortex, and decreasing frontal low-frequency oscillations during symptom provocation in patients with OCD. These findings taken together suggest that DBS is able to reduce maladaptive activity and connectivity of the stimulated region and to restore disease-related brain networks to a healthy state (93). To consider a psychiatric disorder as a possible new indication for DBS and a particular patient as candidate Denys (2008) suggested the following criteria (94): Disorder-related criteria: (a) A general agreement on the neuropsychiatric nature of the disorder. (b) A proven relationship with a dysfunctional brain circuitry. (c) Objectively measurable symptoms. Patient-related criteria: (a) Presence of very severe symptoms and considerable suffering. (b) Absence of available effective treatments. (c) Potential to regain reasonable functioning and integration in society.
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