Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> Summary In seven selected patients with dystonia musculorum deformans-1 generalised dystonia (DYT1), continuous bilateral stimulation of the globus pallidus internus was associated with substantial improvement of dystonia and functional disability. <s> BIB001 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> In 48 consecutive patients, we applied a new stereotactic imaging technique to individually visualize the pallidal target before surgery. A turbo spin-echo proton density sequence (acquisition time ... <s> BIB002 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> For deep brain stimulation (DBS) of the subthalamic nucleus (STN), it would be an advantage if the STN could be visualized with fast acquisition of MR images, allowing direct and individual targeting. We present a protocol for T2-weighted, nonvolumetric fast-acquisition MRI, implemented at 8 centers in 6 countries. Acquisition time varied between 3 min 5 s and 7 min 48 s according to the center, and imaging often provided visualization of the STN on axial and coronal scans. Postoperatively, the same imaging protocol permitted visualization of the target area and DBS electrodes with minimum artifacts. This imaging technique may contribute to a decrease in the number of electrode passes at surgery. <s> BIB003 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> The long term objective of our research is to develop a system that will automate as much as possible DBS implantation procedures. It is estimated that about 180,000 patients/year would benefit from DBS implantation. Yet, only 3000 procedures are performed annually. This is so because the combined expertise required to perform the procedure successfully is only available at a limited number of sites. Our goal is to transform this procedure into a procedure that can be performed by a general neurosurgeon at a community hospital. In this work we report on our current progress toward developing a system for the computer-assisted pre-operative selection of target points and for the intra-operative adjustment of these points. The system consists of a deformable atlas of optimal target points that can be used to select automatically the pre-operative target, of an electrophysiological atlas, and of an intra-operative interface. The atlas is deformed using a rigid then a non-rigid registration algorithm developed at our institution. Results we have obtained show that automatic prediction of target points is an achievable goal. Our results also indicate that electrophysiological information can be used to resolve structures not visible in anatomic images, thus improving both pre-operative and intra-operative guidance. Our intra-operative system has reached the stage of a working prototype that is clinically used at our institution. <s> BIB004 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> OBJECT ::: Functional neurosurgical interventions such as deep brain stimulation (DBS) are traditionally performed with the aid of a stereotactic frame. Although frameless techniques have been perceived as less accurate, data from a recent phantom study of a modified frameless approach demonstrated a laboratory accuracy exceeding that obtained using a common frame system. The present study was conducted to evaluate the accuracy of a frameless system in routine clinical use. ::: ::: ::: METHODS ::: Deep brain stimulation leads were implanted in 38 patients by using a skull-mounted trajectory guide and an image-guided workstation. Registration was accomplished with bone fiducial markers. Final lead positions were measured on postoperative computerized tomography scans and compared with the planned lead positions. The accuracy of the Leksell frame within the clinical situation has been reported on in a recent study; these raw data served as a comparison data set. The difference between expected and actual lead locations in the x plane was 1.4 mm in the frame-based procedure and 1.6 mm in the frameless procedure. Similarly, the difference in the y plane was 1.6 mm in the frame-based system and 1.3 mm in the frameless one. The error was greatest in the z plane, that is, 1.7 mm in the frame-based method and 2 mm in the frameless system. Multivariate analysis of variance demonstrated no statistically significant difference in the accuracy of the two methods. ::: ::: ::: CONCLUSIONS ::: The accuracy of the frame-based and frameless systems was not statistically significantly different (p = 0.22). Note, however, that frameless techniques offer advantages in patient comfort, separation of imaging from surgery, and decreased operating time. <s> BIB005 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> INTRODUCTION ::: The use of image-guided systems (IGS) for brain biopsy has increased in neurosurgical practice. We sought to evaluate the accuracy of a plastic, disposable burr hole mounted guide for stereotactic biopsy using an IGS and compare the results of different targeting methods with those of frame based localization. ::: ::: ::: METHODS ::: MRIs were performed on a skull model with mounted fiducials with a stereotactic frame in place and data was loaded onto the Stealth IGS. The model was placed in a Mayfield head holder and fixed to the OR table. Registration of imaging to physical space was carried out. Using three different targeting methods on the Stealth IGS, the distance between the target and the predicted position of the target, the offset error, was measured in three dimensions and confirmed by 2 observers. A sum of squares for the 3 offset errors in all planes was used to calculate the summed vector error. The same MRI dataset used with the Cosman-Roberts-Wells (CRW) stereotactic frame for comparison. The summed vector error was calculated in the same manner to compare the accuracy of targeting with these guides to the frame-based CRW system. ::: ::: ::: RESULTS ::: For frameless stereotaxy using the "Straight- guide 4 2D" targeting method the mean error was 2.58 +/- 0.51 mm (n=12). The vector error was 5.23 +/- 0.54 (n=4). For the registration set and target using the "Offset- guide 4 2D" targeting method the mean error was 1.66 +/- 0.36 mm (n=12). The vector error was 3.32 +/- 0.72 (n=4). The best localization was obtained with the "probe's eye" planning and targeting. The mean error was 0.33 +/- 0.16 mm (n=12). The vector error was 1.0 +/- 0.28 (n=4). We found a statistical difference between the different techniques (P<0.001) (Kruskal-Wallis One Way Analysis of Variance on Ranks). An all pairwise multiple comparison procedure (Holm-Sidak method) found an overall significance level = 0.05. For the frame-based CRW the mean error from the target was 1.03 +/- 0.19 mm (n=18) and the mean target localization error vector was 2.23 +/- 0.14 (n=6). We found a statistically significant difference between NDT guide "Probes Eye" vs. the MR-CRW (P=0.003, Mann-Whitney Rank Sum Test). ::: ::: ::: CONCLUSIONS ::: These results indicate that using MR imaging, surgical planning software and the skull mounted Navigus-DT with the probe's eye view option for targeting, localization accuracy appears to fall within acceptable ranges compared with frame-based methods which have been the standards for stereotactic brain biopsy and functional neurosurgery. Furthermore, there may be considerable differences in accuracy between different targeting methods. <s> BIB006 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> BACKGROUND ::: Deep brain stimulation (DBS) is widely used to treat advanced Parkinson's disease, other movement and psychiatric disorders. DBS implantation requires application of a stereotactic frame throughout a lengthy procedure, making it uncomfortable and tiring. We designed a stereotactic cube to stage the operation, perform frameless microelectrode recording (MER) and fix the DBS. ::: ::: ::: METHODS ::: The 15-mm cube is implanted in a burr hole using bone cement. It contains 5 parallel trajectories (central + 4 around). It is aligned by stereotactic frame so that central trajectory reaches the target. Frameless MER is performed by attaching a micro-driver to the cube using 2-5 cannulae (4 cm). The DBS is fixed to the cube by a mini-plate and 1 screw. Ninety-six cubes were compared with 43 Bennet spheres (BS). ::: ::: ::: RESULTS ::: No cube moved compared to 2 (5%) BS (p < 0.05). The final trajectory was central in 64.4% of cubes compared to 47.5% of BS, and the final target was >2 mm out in no cubes compared to 12.5% of BS (p < 0.01). Infection and haemorrhage were observed in 2.5% and 3.3% of cubes, respectively, while 5% of BS developed infection, 5% haemorrhage and 7.5% skin erosion. ::: ::: ::: CONCLUSIONS ::: This method is simple and effective in staging DBS procedures, performing frameless MER and DBS implantation, fixation and revision. <s> BIB007 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> Numerous factors need to be taken into account when implanting deep brain stimulation (DBS) systems into patients with Parkinson's disease. The surgical procedure itself can be divided into immediate preoperative, intraoperative, and immediate postoperative phases. Preoperative considerations include medication withdrawal issues, stereotactic equipment choices, imaging modalities, and targeting strategy. Intraoperative considerations focus on methods for physiological confirmation of a given target for DBS electrode deployment. Terms such as microelectrode recording, microstimulation, and macrostimulation will be defined to clarify inconsistencies in the literature. Advantages and disadvantages of each technique will be addressed. Furthermore, operative decisions such as staging, choice of electrode and implantable pulse generator, and methods of device fixation will be outlined. Postoperative issues include imaging considerations, including magnetic resonance safety, device–device interactions, and immediate surgical complications pertaining to the DBS procedure. This report outlines answers to a series of questions developed to address all aspects of the DBS surgical procedure and decision-making with a systematic overview of the literature (until mid-2004) and by the expert opinion of the authors. This is a report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society. It outlines answers to a series of questions developed to address all surgical aspects of deep brain stimulation. © 2006 Movement Disorder Society <s> BIB008 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> The accuracy and precision of frameless neuronavigation as compared to conventional frame-based stereotaxy for implantation of deep brain stimulation (DBS) electrodes were studied in 14 patients with essential tremor. DBS electrodes were implanted bilaterally in the ventrolateral thalamus [ventrointermediate nucleus (VIM)] in one procedure. Frameless neuronavigation was used on one side and the conventional frame-based technique on the other. Targeting was guided by MRI and CT imaging. Intraoperative stereotactic plain X-ray verified final electrode positions and electrode deviations from the planned target were measured. Clinical outcome was evaluated with the Essential Tremor Rating Scale. Thirteen of the patients were eligible for measuring electrode deviations and 10 of them were available for a clinical follow-up. Electrode deviations from target were larger using the frameless technique in the medial-lateral (x: 1.9 +/- 1.3 mm) and anterior-posterior (y:0.9 +/- 0.8 mm) directions as compared to the frame-based technique (x: 0.5 +/- 0.5 and y: 0.4 +/- 0.4 mm) but similar in the superior-inferior direction (z). The vector of deviation was 2.5 +/- 1.4 mm with the frameless technique and 1.2 +/- 0.6 with the frame-based technique. The differences were statistically significant (p < 0.05-0.001). The dispersion was larger with the frameless technique as represented by the larger standard deviations in all three planes. At clinical follow-ups, tremor reduction was similar irrespective of the implantation technique. It is concluded that conventional frame-based stereotaxy has higher accuracy/precision for hitting a small brain target than the frameless technique. However, the difference is relatively small and does not influence the clinical result of DBS electrode implantations in the VIM when treating tremor. <s> BIB009 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> Object Relationships between clinical effects, anatomy, and electrophysiology are not fully understood in DBS of the subthalamic region in Parkinson's disease. We proposed an anatomic study based on direct image-guided stereotactic surgery with a multiple source data analysis. ::: Materials and Methods A manual anatomic mapping was realized on coronal 1.5-Tesla MRI of 15 patients. Biological data were collected under local anesthesia: the spontaneous neu-ron activities and the clinical efficiency and the appearance of adverse effects. They were related to relevant current values (mA), the benefit threshold (bt, minimal current leading an clear efficiency), the adverse effect threshold (at, minimal current leading an adverse effect) and the stimulation margin (sm = at − bt); they were matched with anatomy. ::: Results We found consistent relationships between anatomy and biological data. The optimal stimulation parameters (low bt + high sm) were noted in the dorsolateral STN. The highest spontaneous neuron activity was found in the ventromedial STN. Dorsolateral (sensorimotor) STN seems the main DBS effector. The highest spontaneous neuron activity seems related to the anterior (rostral) ventromedial (limbic) STN. ::: Conclusion 1.5 Tesla images provide sufficiently detailed sub-thalamic anatomy for image-guided stereotactic surgery and may aid in understanding DBS mechanisms. <s> BIB010 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> OBJECTIVE: Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective treatment for medically refractory primary dystonia. We present our technique for direct preoperative visualization of the target using a fast spin-echo inversion-recovery (FSE-IR) sequence. METHODS: Twenty-three consecutive patients (mean age 41 years, range 9-68 years, male to female ratio 11:12) with severe dystonia were operated using a combination of FSE-IR imaging for direct visualization of the globus pallidus internus with stereotactic, gadolinium-enhanced T1-MPRage images. The complete procedure, including stereotactic MRI, was performed under general anesthesia with propofol and remifentanyl. We used multichannel microdrive systems (Medtronic; Alpha-Omega) to introduce up to five parallel microelectrodes for microelectrode recordings (MER) and test stimulation with the central trajectory directed at the anatomically predefined target. The initial standard coordinates in relation to the mid-commissural point (mid-AC-PC) were as follows: lateral 21 mm, anterior 3 mm, and inferior 2 mm, which were then adapted to the individual case based on direct visualization of the target area and further refined by the intraoperative neurophysiology. RESULTS: In ten patients (43%) atlas-based standard coordinates were modified based on the direct visualization of the GPi in the FSE-IR images (bilaterally in seven patients, unilaterally in three). The modified targets ranged from 18.5 to 23.5 mm (mean 20.76 mm) laterally, 1-7 mm (mean 2.75 mm) anteriorly and 1-2 mm (mean 1.95 mm) inferiorly to the mid-AC-PC. We implanted the permanent electrode based on the results of MER and intraoperative stimulation performed to determine the threshold for pyramidal tract responses on the central trajectory in 67%, medially in 16%, anteriorly in 11%, laterally in 4%, dorsally in 2%. The procedure resulted in excellent clinical benefits (average reduction of the Burke-Fahn-Marsden Dystonia Rating Score (BFMDRS) or the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) were respectively 65.9%, range 20.9-91.4%) within the first year after surgery. Safety was demonstrated by the absence of intracranial bleeding or other surgical complications causing neurological morbidity. CONCLUSION: Inversion recovery sequences are an excellent tool for direct visualization of the GPi. These images can be fused to stereotactic MRI or CCT and may help to improve anatomical targeting of the GPi for the implantation of DBS electrodes. <s> BIB011 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> Deep-brain-stimulation (DBS) surgery requires implanting stimulators at target positions with sub millimetric accuracy. Traditional stereotactic frames can provide such accuracy, but a recent innovation called the micro Targeting Platform (FHC, Inc.) replaces this large, universal frame with a single-use, miniature, and custom-designed platform. Both single-target and dual-target platforms are available for unilateral and bilateral procedures, respectively. In this paper, their targeting accuracies are evaluated in vitro. Our approach employs ldquovirtual targets,rdquo which eliminates the problem of collision of the implant with the target. We implement virtual targets by mounting fiducial markers, which are not used in platform targeting, on an artificial skull and defining targets relative to the skull via that fiducial system. The fiducial system is designed to surround the targets, thereby reducing the overall effect of fiducial localization inaccuracies on the evaluation. It also provides the geometrical transformation from image to physical space. Target selection is based on an atlas of stimulation targets from a set of 31 DBS patients. The measured targeting error is the displacement between the phantom implant and the virtual target. Our results show that the micro Targeting Platform exhibits sub millimetric in vitro accuracy with a mean of 0.42 mm and a 99.9% level of 0.90 mm. <s> BIB012 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> Surgery combining stereotactically guided implantation of brain electrodes in subcortical key structures of the brain with the connection of these brain electrodes to subcutaneously implanted impulse generators is one precondition for the therapeutic application of deep brain stimulation (DBS). During the last 10-15 years minimal requirements concerning this surgery have been formulated, addressing in particular technical equipment and operational procedures and being also in parts supported quantitatively by systematic investigations. Only appropriate patient management, high technical standards and an adequate surgical technique can minimize the frequency of those complications, which are supposed to be directly caused by surgery. High-resolution imaging is the basis for target definition, determination of the surgical approach, documentation of final electrode position and postoperative exclusion of iatrogenic intracerebral haemorrhage. In addition, the quality of treatment planning depends largely on the image processing and viewing possibilities provided by specific planning software. Further issues, for which standards are defined, address electrophysiological and clinical examinations to be performed intraoperatively and general surgical measures, which should be considered during implantation of DBS systems. This review summarizes and evaluates requirements imposed on the aforementioned system components and working steps, taking into consideration data from the literature. <s> BIB013 </s> Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools <s> Preoperative planning <s> AIMS ::: Spectral analysis of local field potential (LFP) recorded by deep brain stimulation (DBS) electrode around the subthalamic nucleus (STN) in patients with Parkinson's disease was performed. ::: ::: ::: METHODS ::: The borders of the STN were determined by microelectrode recording. The most eligible trajectory for the sensorimotor area of the STN was used for LFP recording while advancing the DBS electrode. ::: ::: ::: RESULTS ::: The low-frequency LFP power (theta- to beta-band) increased from a few millimeters above the dorsal border of the STN defined by microelectrode recording; however, the low-frequency power kept the same level beyond the ventral border of the STN. Only high beta-power showed close correlation to the dorsal and ventral borders of the STN. ::: ::: ::: CONCLUSIONS ::: A spectral power analysis of LFP recording by DBS electrode helps with the final confirmation of the dorsal and ventral borders of the STN of Parkinson's disease in DBS implantation surgery. <s> BIB014
The first part is preoperative planning where the specific target in the brain and the trajectory to reach this target are planned on preoperative anatomical images. In general, fiducials are affixed to the skull of the patient via a stereotactic system in order to introduce a reference system to the images. Different frameless fiducial systems for DBS implantation have been described and compared with frame-based systems BIB012 BIB009 BIB004 BIB007 BIB005  BIB006 , but stereotactic frame-based systems remain the gold standard. In consequence, this article will concentrate on the procedures using the stereotactic frame. Comparing the implantation procedures in different clinical centres, differences in the preoperative part can especially be found in the stereotactic system, the imaging modality, the moment of image acquisition and the targeting technique. Concerning the stereotactic systems, differences do exist such as the type of coordinate system used, either a Cartesian coordinate system with x, y and z coordinates (G frame, Leksell Stereotactic Systems Ò )  or a polar coordinate system describing the target by angles to horizontal and vertical plane and the distance to a reference point (CosmanRobert-Wells CRW frame, Riechert-Mundinger frame)  . Furthermore, sometimes a phantom base exists to confirm accuracy of coordinate adjustment and integrity of the entire stereotactic system (CRW, Riechert-Mundinger frame). The coordinate calculation is usually performed with a commercially available stereotactic software: iPlan (BrainLab AG, Munich, Germany), SurgiPlan (Elekta Instrument AB, Stockholm, Sweden), Framelink (Medtronic Incorporation, Minneapolis, MN, USA) and STP (Stereotactic Treatment Planning System; Howmedica Leibinger GmbH, Freiburg, Germany). Concerning the imaging modalities, ventriculography has historically been the gold standard based on its highly reliable identification of the anterior and the posterior commissure (AC, PC) used as references for atlas-based indirect targeting. Today it has been replaced by CT and MR imaging BIB008 BIB013 . MRI is the imaging modality of choice to visualise the anatomic targets. The sequence used depends on the chosen target structure: T 1 BIB001 or proton density imaging BIB002 is especially used for targeting of the globus pallidus; T 2 imaging for STN targeting BIB003 BIB008  ; inversion recovery images are also beneficial for direct targeting of GPi and STN BIB011 . Figure 2a shows a stereotactic T 2 MR image and 2b the planned trajectories. Moments of image acquisition can be different. Some centres acquire stereotactic MRI on the day of implantation just before surgery  , while others perform the MRI on the day before surgery and reposition the stereotactic frame on the day of surgery BIB010 . More often, an MRI is acquired some days before the implantation to be merged with a stereotactic CT on the day of surgery BIB014  . Furthermore, there are two types of targeting techniques. The planning, i.e. the way the definition of entry point, trajectory and target takes place is sometimes based on MR or, CT and MR data alone  BIB003 which is called ''direct targeting'' (Fig. 2b) . Other groups prefer using anatomical brain atlases created from dissected brains and superimposing them to the MRI (''indirect targeting'') to improve the identification of nuclei in the thalamus or basal ganglia (e.g. STN, GPi), or other invisible or hardly identifiable structures of the deep brain. Modern versions of the Schaltenbrandt-Wahren and the Talairach atlases  computer use and as 3D image reconstructions. Another approach to perform an accurate 3D multiplane analysis is manual segmentation with the help of stereotactic books and 4.7 Tesla MRI anatomy software BIB010 .