50 Chapter 3 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 (15) the complete study comprised four sequential phases: preoperative, surgery, optimization and maintenance phase (figure 1). Figure 1. Treatment protocol (wks = weeks; min = minimal) 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 T-1 T0 T1 T2 T3 T4 Preoperative phase Surgery phase - - 3 wks min 12 wks 26 wks 26 wks No implants - off on on on Optimization phase Maintenance phase
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