70 Chapter 3 implanted in the anterior limb of the internal capsule with an anterior angle of approximately 75° to the intercommissural line, using stereotactic frame-based 1.5 Tesla magnetic resonance imaging (MRI) coregistered to pre-operative 3T MRI with 1-mm slices for target determination. The upper three contact points of the electrode were placed in the vALIC, the lowest contact point was placed in the nucleus accumbens, ±3 mm anterior to the anterior commissure according to Mai et al., 2015. The electrodes were connected via a subcutaneous extension cable to a neurostimulator (Activa Primary Cell/Rechargeable Cell, Medtronic, Minneapolis), implanted under the pectoral muscle in the infraclavicular region. Postoperative computed tomography (CT) was performed and coregistered to pre-operative MRI to confirm accurate position of the electrodes. Treatment procedure In accordance with our earlier DBS studies (6) the complete study comprised four sequential phases: preoperative, surgery, optimization and maintenance phase. In the preoperative phase (T-1) we conducted baseline measurements. Standard somatic and psychiatric care was available to all patients throughout this period, including hospitalization. Once patients were considered fit for surgery (T0), the electrodes and stimulator were implanted. The patients were discharged from the department of neurosurgery one or several days after the procedure, depending on the physical condition of the patient. The optimization phase lasted between three and nine months. In brief, immediately after recovery from surgery, the neurostimulator stayed in off mode during three weeks in order to prevent interference with the effects from surgery that might have complicated the fine-tuning of the stimulation parameters (electrode contact selection, frequency, voltage). After these three weeks, we switched the neurostimulator on (T1) and performed fine-tuning/ optimization of the neurostimulation during three to six months. We optimized the stimulation intensity with initial steps of 0,5 V, fine-tuning occurred by adjusting the voltage with steps of 0,1 V. During this phase, we determined the stimulation parameter settings that provided the best clinical improvement (4). If, thereafter, we still expected clinical improvement with additional changes in neurostimulator settings, a continuation of the fine-tuning phase was possible for three more months (optimization was performed during three to nine months), with assessments of improvement every week until a plateau of effectiveness was reached. In one patient the contact points were changed during the optimization period in order to use the two contact points that were closest to the medial forebrain bundle (MFB). Patients entered the maintenance phase of the study after the optimization period was completed (T2). The maintenance phase consisted of a 12 months period with the stimulator on, to assess the long-term effect of DBS on BMI, comorbidity, and eating behavior. Measuring points during the maintenance phase were at 6 months (T3) and at 12 months (T4, end of the study).
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