Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Postoperative follow-up <s> BACKGROUND ::: The electrode Activa 3389 is widely implanted for deep brain stimulation (DBS) and MRI is often used to control the position of the electrode. However, induced distorsion artifacts may result in imprecise localization and may lead to misinterpretations of the clinical effects and mechanisms of DBS. ::: ::: ::: METHODS ::: In vitro 3D MR study: the proximal and distal contacts of one electrode were spotted by two localizers. The maximal artifact height (MAH) and width (MAW: measured on distal contact), and the distances between the artifact and the localizers (proximal, distal and lateral) were measured on 2 transverse and sagittal MR sequences with 90 degrees rotation of frequency-encoded gradient and phase direction. In vivo 3D MR study: coronal and sagittal reconstructions along the main axis of the electrode were performed on 10 postoperative MR (20 electrodes) to measure MAH and MAW. A Student t test was used to compare in vitro and in vivo measurements. ::: ::: ::: FINDINGS ::: In vitro study: A MAH of 10.35 mm (+/-0.23) and MAW of 3.6 mm (+/-0.2) were found. We measured symmetrical extensions of the artifact over the distal contact. In vivo study: A MAH of 10.36 mm (+/-0.44) and MAW of 3.56 mm (+/-0.30) were obtained. No significant different artifact dimensions were measured between in vitro and in vivo studies (p<0.0001). ::: ::: ::: INTERPRETATION ::: Precise 3D localization of the electrode in implanted patients is provided by MR identification of the limits of the distal contact artifact. The position of the other contacts is deduced given the size of the contacts and the intercontact distance. <s> BIB001 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Postoperative follow-up <s> Objective:To assess the role of age in the results of bilateral deep brain stimulation in the subthalamic nucleus (DBS-STN), we carried out a study of two groups of patients regarding age at time of surgery. Methods:We compared, up to 2 years after surgery, the clinical effects, safety, and quality of life in parkinsonian patients younger than 65 years old (young patients) vs parkinsonian patients 65 years old or older (old patients). Results:The mean age was 57.4 ± 4.9 years (n = 53) in young patients and 68.8 ± 2.8 years (n = 34) in old patients. A dramatic improvement in motor complications was equally observed in both groups of patients. There was no significant difference between the groups regarding acute effects of DBS-STN on the motor score of the Unified Parkinson's Disease Rating Scale part III (UPDRS III). Time course evolution of UPDRS the motor score (p < 0.0001) and axial score (p = 0.0001) assessed postoperatively in “on” medication and “on” stimulation conditions appeared worse in old patients as compared to young patients. Improvement in the Schwab and England Scale score was better in young patients in “on” (p < 0.0003) and “off” state (p < 0.001). Quality of life assessed with the 39-item Parkinson's Disease Questionnaire showed an improvement in subscales evaluating mobility (p < 0.0001), activities of daily life (p < 0.0001), emotion and stigma (p = 0.0004), cognition (p < 0.0074), and communication (p = 0.0029) in young patients as compared to old patients. Side effects were similar in the two groups. Conclusions:Although deep brain stimulation in the subthalamic nucleus reduces motor complications equally in both groups of patients, postoperative quality of life improved only in young patients. <s> BIB002 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Postoperative follow-up <s> Object ::: In deep brain stimulation, the anatomic positions of electrode contact centers are used as the basis for analysis. We propose a new semi-quantitative approach (contact membership concept) considering patient’s individual anatomy, contact size, and extent of involvement of STN and neighboring structures. <s> BIB003
Postoperatively, a control of the final electrode position and the absence of haemorrhage via CT or MRI BIB003 BIB001  is commonly part of the protocol (Fig. 2c) . This is then done directly after the implantation procedure with or without the frame on. Due to the electrode artefacts on the postoperative images hiding parts of the anatomical structures, pre-and postoperative images are often merged using stereotactic planning software-sometimes as well with anatomical atlases-in order to be able to identify the anatomical structures around each electrode contact. Furthermore, this image fusion is part of a quality control as it makes possible a comparison between the planned and the final electrode position. The patient follow-up is as well part of the postoperative follow-up; it consists of regular consultations. Especially at the early stage, stimulation parameters have to be adapted individually: stimulated contacts, pulse width, frequency and voltage have to be programmed. When an ON/OFF effect (immediate disappearance and reappearance respectively of symptoms) exists, as is the case for tremor, many centres perform a test session where all the four electrode contacts are successively activated with increasing voltage to identify first the therapeutically effective contacts. Furthermore, the ''symptom arrest threshold'', i.e. the lowest voltage for which symptoms disappear, and the ''side effect threshold'', i.e. the lowest voltage for which side effects start to occur BIB002 , can be determined. When the therapeutic effect is not immediate and may take days to several months, as for dystonia, a long lasting test period is needed in searching for the optimal stimulation parameters. In these cases, the choice of the first parameter configuration is based on experience and can be guided by the anatomic contact position, especially when postoperative MRI could be performed  BIB002 .