Deep Brain Stimulation For Tremor Research Articles

Comparison of Dentatorubrothalamic Tractography Methods Based on the Anatomy of the Rubral Wing.

Precise localization of the dentatorubrothalamic (DRT) tract can facilitate anatomic targeting in MRI-guided high-intensity focused ultrasound (HIFU) thalamotomy and thalamic deep brain stimulation for tremor. The anatomic segment of DRT fibers adjacent to the ventral intermediate nucleus of the thalamus (VIM), referred to as the rubral wing (RW), may be directly visualized on the fast gray matter acquisition T1 inversion recovery. We compared reproducibility, lesion overlap, and clinical outcomes when reconstructing the DRT tract using a novel anatomically defined RW region of interest, DRT-RW, to an existing tractography method based on the posterior subthalamic area region of interest (DRT-PSA). We reviewed data of 23 patients with either essential tremor (n = 18) or tremor-predominant Parkinson's disease (n = 5) who underwent HIFU thalamotomy, targeting the VIM. DRT tractography, ipsilateral to the lesion, was created based on either DRT-PSA or DRT-RW. Volume sections of each tract were created and dice similarity coefficients were used to measure spatial overlap between the 2 tractographies. Post-HIFU lesion size and location (on postoperative T2 MRI) was correlated with tremor outcomes and side effects for both DRT tractography methods and the RW itself. DRT-PSA passed through the RW and DRT-RW intersected with the ROIs of the DRT-PSA in all 23 cases. A higher percentage of the RW was ablated in patients who achieved tremor control (18.9%, 95% CI 15.1, 22.7) vs those without tremor relief (6.7%, 95% CI% 0, 22.4, P = .017). In patients with tremor control 6 months postoperatively (n = 12), those with side effects (n = 6) had larger percentages of their tracts ablated in comparison with those without side effects in both DRT-PSA (44.8, 95% CI 31.8, 57.8 vs 24.2%, 95% CI 12.4, 36.1, P = .025) and DRT-RW (35.4%, 95% CI 21.5, 49.3 vs 21.7%, 95% CI 12.7, 30.8, P = .030). Tractography of the DRT could be reconstructed by direct anatomic visualization of the RW on fast gray matter acquisition T1 inversion recovery-MRI. Anatomic planning is expected to be quicker, more reproducible, and less operator-dependent.

Deep Brain Stimulation for Tremor: Update on Long-Term Outcomes, Target Considerations and Future Directions

Deep brain stimulation (DBS) of the thalamic ventral intermediate nucleus is one of the main advanced neurosurgical treatments for drug-resistant tremor. However, not every patient may be eligible for this procedure. Nowadays, various other functional neurosurgical procedures are available. In particular cases, radiofrequency thalamotomy, focused ultrasound and radiosurgery are proven alternatives to DBS. Besides, other DBS targets, such as the posterior subthalamic area (PSA) or the dentato-rubro-thalamic tract (DRT), may be appraised as well. In this review, the clinical characteristics and pathophysiology of tremor syndromes, as well as long-term outcomes of DBS in different targets, will be summarized. The effectiveness and safety of lesioning procedures will be discussed, and an evidence-based clinical treatment approach for patients with drug-resistant tremor will be presented. Lastly, the future directions in the treatment of severe tremor syndromes will be elaborated.

Deep-Brain Stimulation for Essential Tremor and Other Tremor Syndromes: A Narrative Review of Current Targets and Clinical Outcomes.

Tremor is a prevalent symptom associated with multiple conditions, including essential tremor (ET), Parkinson’s disease (PD), multiple sclerosis (MS), stroke and trauma. The surgical management of tremor evolved from stereotactic lesions to deep-brain stimulation (DBS), which allowed safe and reversible interference with specific neural networks. This paper reviews the current literature on DBS for tremor, starting with a detailed discussion of current tremor targets (ventral intermediate nucleus of the thalamus (Vim), prelemniscal radiations (Raprl), caudal zona incerta (Zi), thalamus (Vo) and subthalamic nucleus (STN)) and continuing with a discussion of results obtained when performing DBS in the various aforementioned tremor syndromes. Future directions for DBS research are then briefly discussed.

Thalamic Deep Brain Stimulation for tremor: The critical role of intraoperative testing

IntroductionOptimal placement of Deep Brain Stimulation (DBS) lead is critical to ensure an adequate therapeutic benefit and minimize stimulation-induced side effects. MethodsWe reviewed data from 2004 to 2018 of all cases of essential tremor treated with thalamic DBS at the University of Cincinnati. All procedures were performed with the patient awake. Change in parallel trajectory was classified as major repositioning, whereas a change in depth of electrode classified as minor repositioning. The following data were compared between groups (no vs. minor vs. major repositioning): age at surgery, sex, AC-PC length, third ventricle width, cerebral atrophy, small vessel disease burden, and intraoperative tremor control. Univariate and multivariate analyses were conducted to identify factors associated with intraoperative repositioning. ResultsOf the 127 encounters with essential tremor, 71 required repositioning (33 major and 38 minor). Comparing procedures with major, minor, and no repositioning, mean number of changes per procedure (4 vs. 1.2 vs 0; p < 0.001) and AC-PC length (26 vs. 27 vs. 27.2 mm; p = 0.021) differed between the three groups. Older age at surgery (OR 1.04, p = 0.042), left side (OR 2.56, p = 0.04) and decrease in AC-PC length (OR 1.33, p = 0.026) were associated with greater odds of any (minor or major) repositioning. A decrease in AC-PC length was associated with greater odds of major repositioning (OR 1.37, p = 0.009). ConclusionIntraoperative functional testing may be critical to ensure the accuracy of thalamic DBS targeting based on neuroimaging data, particularly in patients with reduced AC-PC length.

Deep Brain Stimulation for Tremor and Dystonia.

Deep brain stimulation (DBS) is the most commonly used surgical treatment for drug-refractory movement disorders such as tremor and dystonia. Appropriate patient selection along with target selection is important to ensure optimal outcome without complications. This review summarizes the recent literature regarding the mechanism of action, indications, outcome, and complications of DBS in tremor and dystonia. A comparison with other modalities of surgical interventions is discussed along with a note of the recent advances in technology. Future research needs to be directed to understand the underlying etiopathogenesis of the disease and the way in which DBS modulates the intracranial abnormal networks.

Comparison of posterior subthalamic area deep brain stimulation for tremor using conventional landmarks versus directly targeting the dentatorubrothalamic tract with tractography

ObjectiveTo compare posterior subthalamic area deep brain stimulation (PSA-DBS) performed in the conventional manner against diffusion tensor imaging and tractography (DTIT)-guided lead implantation into the dentatorubrothalamic tract (DRTT). Patients and MethodsDouble-blind, randomised study involving 34 patients with either tremor-dominant Parkinson's disease or essential tremor. Patients were randomised to Group A (DBS leads inserted using conventional landmarks) or Group B (leads guided into the DRTT using DTIT). Tremor (Fahn-Tolosa-Marin) and quality-of-life (PDQ-39) scores were evaluated 0-, 6-, 12-, 36- and 60-months after surgery. ResultsPSA-DBS resulted in marked tremor reduction in both groups. However, Group B patients had significantly better arm tremor control (especially control of intention tremor), increased mobility and activities of daily living, reduced social stigma and need for social support as well as lower stimulation amplitudes and pulse widths compared to Group A patients. The better outcomes were sustained for up to 60-months from surgery. The active contacts of Group B patients were consistently closer to the centre of the DRTT than in Group A. Speech problems were more common in Group A patients. ConclusionDTIT-guided lead placement results in better and more stable tremor control and fewer adverse effects compared to lead placement in the conventional manner. This is because DTIT-guidance allows closer and more consistent placement of leads to the centre of the DRTT than conventional methods.

An Unusual Case of Essential Tremor Deep Brain Stimulation: Where is the Lead?

An Unusual Case of Essential Tremor Deep Brain Stimulation: Where is the Lead?

Thalamic Directional Deep Brain Stimulation for tremor: Spend less, get more

BackgroundDirectional Deep Brain Stimulation (D-DBS) allows axially asymmetric electrical field shaping, away from structures causing side-effects. However, concerns regarding the impact on device lifespan and complexity of the monopolar survey have contributed to sparing use of these features. ObjectiveTo investigate whether chronically implanted D-DBS systems can improve the therapeutic window, without a negative impact on device lifespan, in thalamic deep brain stimulation (DBS). MethodsWe evaluated stable outcomes of initial programming sessions (4–6 weeks post-implantation) retrospectively in 8 patients with drug-resistant disabling tremor syndromes. We assessed the impact of directional stimulation on the Therapeutic Window (TW), Therapeutic Current Strength (TCS), tremor scores, disability scores and total electrical energy delivered. Finally, we performed Volume of Tissue Activation (VTA) modelling, based on a range of parameters. ResultsWe report significant gains in TW (91%) and reductions in TCS (31%) with stimulation in the best direction compared to best omnidirectional stimulation alternative. Tremor and ADL scores improvements remained unchanged at six months. There was no increase in averaged IPG power consumption (there is a 6% reduction over the omnidirectional-only alternative). Illustrative VTA modelling shows that D-DBS achieves 85% of the total activation volume at just 69% of the stimulation amplitude of non-directional configuration.Conclusions: D-DBS can improve the therapeutic window over non-directional DBS, leading to significant reduction in disability that may be sustained without additional reprogramming visits. When averaged across the cohort, power output and predicted device lifespan was not impacted by the use of directional stimulation in this study.

Predictors of deep brain stimulation outcome in tremor patients

BackgroundDeep brain stimulation of the ventro-intermedius nucleus of the thalamus is an established treatment for tremor of differing etiologies but factors that may predict the short- and especially long-term outcome of surgery are still largely unknown. MethodsWe retrospectively investigated the clinical, pharmacological, electrophysiological and anatomical features that might predict the initial response and preservation of benefit in all patients who underwent deep brain stimulation for tremor. Data were collected at the following time points: baseline (preoperative), one-year post-surgery, and most recent visit. Tremor severity was recorded using the Fahn-Tolosa-Marin Tremor Rating Scale and/or the Unified Parkinson's Disease Rating Scale. ResultsA total of 52 patients were included in the final analysis: 31 with essential tremor, 15 with cerebellar tremor of different etiologies, and 6 with Parkinson's disease. Long-term success (mean follow-up duration 34.7 months, range 1.7–121.1 months) was reported in 63.5%. Predictors of long-term benefit were: underlying tremor etiology (best outcome in Parkinson's disease, worst outcome in cerebellar tremor); age at surgery (the older the better); baseline tremor severity (the greater the better); lack of response to benzodiazepines; a more anterior electrode placement and single-unit beta power (the greater the better). ConclusionsSpecific patients' features (including single unit beta activity) and electrode locations may predict the short- and long-term benefit of thalamic stimulation for tremor. Future prospective studies enrolling a much larger sample of patients are needed to substantiate the associations detected by this retrospective study.

Connectivity derived thalamic segmentation in deep brain stimulation for tremor.

The ventral intermediate nucleus (VIM) of the thalamus is an established surgical target for stereotactic ablation and deep brain stimulation (DBS) in the treatment of tremor in Parkinson's disease (PD) and essential tremor (ET). It is centrally placed on a cerebello-thalamo-cortical network connecting the primary motor cortex, to the dentate nucleus of the contralateral cerebellum through the dentato-rubro-thalamic tract (DRT). The VIM is not readily visible on conventional MR imaging, so identifying the surgical target traditionally involved indirect targeting that relies on atlas-defined coordinates. Unfortunately, this approach does not fully account for individual variability and requires surgery to be performed with the patient awake to allow for intraoperative targeting confirmation. The aim of this study is to identify the VIM and the DRT using probabilistic tractography in patients that will undergo thalamic DBS for tremor. Four male patients with tremor dominant PD and five patients (three female) with ET underwent high angular resolution diffusion imaging (HARDI) (128 diffusion directions, 1.5 mm isotropic voxels and b value = 1500) preoperatively. Patients received VIM-DBS using an MR image guided and MR image verified approach with indirect targeting. Postoperatively, using parallel Graphical Processing Unit (GPU) processing, thalamic areas with the highest diffusion connectivity to the primary motor area (M1), supplementary motor area (SMA), primary sensory area (S1) and contralateral dentate nucleus were identified. Additionally, volume of tissue activation (VTA) corresponding to active DBS contacts were modelled. Response to treatment was defined as 40% reduction in the total Fahn-Tolosa-Martin Tremor Rating Score (FTMTRS) with DBS-ON, one year from surgery. Three out of nine patients had a suboptimal, long-term response to treatment. The segmented thalamic areas corresponded well to anatomically known counterparts in the ventrolateral (VL) and ventroposterior (VP) thalamus. The dentate-thalamic area, lay within the M1-thalamic area in a ventral and lateral location. Streamlines corresponding to the DRT connected M1 to the contralateral dentate nucleus via the dentate-thalamic area, clearly crossing the midline in the mesencephalon. Good response was seen when the active contact VTA was in the thalamic area with highest connectivity to the contralateral dentate nucleus. Non-responders had active contact VTAs outside the dentate-thalamic area. We conclude that probabilistic tractography techniques can be used to segment the VL and VP thalamus based on cortical and cerebellar connectivity. The thalamic area, best representing the VIM, is connected to the contralateral dentate cerebellar nucleus. Connectivity based segmentation of the VIM can be achieved in individual patients in a clinically feasible timescale, using HARDI and high performance computing with parallel GPU processing. This same technique can map out the DRT tract with clear mesencephalic crossing.

Radiosurgical Pallidotomy for Parkinson's Disease.

Deep brain stimulation (DBS) has been widely accepted as a tool for treating many symptoms of Parkinson's disease (PD); pallidotomy has been nearly abandoned. Concerns about both the safety and efficacy of pallidotomy are based on small series, isolated case reports, and techniques that would now be considered obsolete. The senior author recently reviewed long-term follow-up of a series of patients who had gamma knife pallidotomy (GKP) for advanced PD. GKP leads to durable, clinically significant benefit. Bilateral GKP adds incremental improvement. The complication rate was 4% when calculated on a per lesion basis. GKP is not quite as effective as DBS for tremor and bradykinesia; the results of GKP and DBS are equivalent for dyskinesia. GKP should be considered in patients who are not candidates for DBS. GKP is not as invasive as radiofrequency pallidotomy and avoids the problems and expenses associated with DBS. Patients on anticoagulants, with cognitive deficits or with other contraindications to DBS can be offered GKP to alleviate many of the motor symptoms of PD.

Deep Brain Stimulation for Tremor: Is There a Common Structure?

Background: Subthalamic nucleus (STN) stimulation has been recognized to control resting tremor in Parkinson disease. Similarly, thalamic stimulation (ventral intermediate nucleus; VIM) has shown tremor control in Parkinson disease, essential, and intention tremors. Recently, stimulation of the posterior subthalamic area (PSA) has been associated with excellent tremor control. Thus, the optimal site of stimulation may be located in the surrounding white matter. Aims: The objective of this work was to investigate the area of stimulation by determining the contact location correlated with the best tremor control in STN/VIM patients. Methods: The mean stimulation site and related volume of tissue activated (VTA) of 25 tremor patients (STN or VIM) were projected on the Morel atlas and compared to stimulation sites from other tremor studies. Results: All patients showed a VTA that covered ≥50% of the area superior and medial to the STN or inferior to the VIM. Our stimulation areas suggest involvement of the more lateral and superior part of the dentato-rubro-thalamic tract (DRTT), whereas targets described in other studies seem to involve the DRTT in its more medial and inferior part when it crosses the PSA. Conclusions: According to anatomical and diffusion tensor imaging data, the DRTT might be the common structure stimulated at different portions within the PSA/caudal zona incerta.

Thalamic deep brain stimulation for tremor in Parkinson disease, essential tremor, and dystonia

To report on the long-term outcomes of deep brain stimulation (DBS) of the thalamic ventral intermediate nucleus (VIM) in Parkinson disease (PD), essential tremor (ET), and dystonic tremor. One hundred fifty-nine patients with PD, ET, and dystonia underwent VIM DBS due to refractory tremor at the Grenoble University Hospital. The primary outcome was a change in the tremor scores at 1 year after surgery and at the latest follow-up (21 years). Secondary outcomes included the relationship between tremor score reduction over time and the active contact position. Tremor scores (Unified Parkinson's Disease Rating Scale-III, items 20 and 21; Fahn, Tolosa, Marin Tremor Rating Scale) and the coordinates of the active contacts were recorded. Ninety-eight patients were included. Patients with PD and ET had sustained improvement in tremor with VIM stimulation (mean improvement, 70% and 66% at 1 year; 63% and 48% beyond 10 years, respectively; p < 0.05). There was no significant loss of stimulation benefit over time (p > 0.05). Patients with dystonia exhibited a moderate response at 1-year follow-up (41% tremor improvement, p = 0.027), which was not sustained after 5 years (30% improvement, p = 0.109). The more dorsal active contacts' coordinates in the right lead were related to a better outcome 1 year after surgery (p = 0.029). During the whole follow-up, forty-eight patients (49%) experienced minor side effects, whereas 2 (2.0%) had serious events (brain hemorrhage and infection). VIM DBS is an effective long-term (beyond 10 years) treatment for tremor in PD and ET. Effects on dystonic tremor were modest and transient. This provides Class IV evidence. It is an observational study.

Diffusion tensor imaging tractography assisted direct targeting of the cerebello-thalamo-cortical network for deep brain stimulation in tremor - surgical strategy and intra-operative effects

Diffusion tensor imaging tractography assisted direct targeting of the cerebello-thalamo-cortical network for deep brain stimulation in tremor - surgical strategy and intra-operative effects

SP 1. Parkinsonian rest tremor can be detected based on frequency domain features of the cerebral tremor network

Recent research has revealed several features of electrophysiological signals, which change upon manifestation of Parkinsonian rest tremor. These observations spur hope that the onset and the presence of tremor can be inferred by online analysis of brain signals, enabling demand-driven deep brain stimulation for tremor. It is an open question, however, whether it is possible to detect the presence of tremor given only a short data epoch. Furthermore, it is unclear which signals need to be considered for this task. In this study, we re-analyze data from 18 subthalamic nuclei (STN) of 12 tremor-dominant Parkinson patients in whom magnetoencephalography (MEG) and STN local field potentials (LFPs) were recorded simultaneously. Patients rested while tremor waxed and waned spontaneously. Epochs were attributed either to the tremor condition or to the tremor-free condition based on inspection of forearm electromyograms. MEG source activity was extracted from the cerebral tremor network proposed by Timmermann et al. (2003). Data were segmented into 4s epochs and power and connectivity features were computed for each epoch. These features were used as input to elastic net logistic regression to decode the tremor condition. Feature importance was evaluated through analysis of activation patterns and re-classification with single features or a subset of features. When testing and training was performed in different subjects, the decoder accuracy was 70%. Accuracy could be substantially improved by performing cross-validated training within subjects (81 ± 12%). An analysis of feature importance revealed that power features were much more informative than connectivity features. Among others, STN and primary motor cortex beta power as well as thalamic gamma power were found to be particularly discriminative. Considering only STN power features yielded an accuracy of 77 ± 12% in within-subject classification, which was increased to 86 ± 11% when adding MEG power features. A similar accuracy could be obtained when using MEG power features only (85 ± 12%). We conclude that Parkinsonian rest tremor can be distinguished from tremor-free periods with low error rate, provided that training data are available for each subject. Furthermore, connectivity features contribute little to tremor detection on a timescale of a few seconds. Nevertheless, it is of advantage to record cortical, cerebellar and thalamic sources in addition to the STN, as their power features provide additional information. Future research will integrate the current and related findings to design an algorithm for online stimulation control, incorporating estimates of the tremor state and patient-specific parameters set by the clinician.

EP 78. Probabilistic imaging of motor projections of dentate nucleus as target structure for deep brain stimulation in tremor

Objective As previously described ( [Coenen et al., 2014] , [Coenen et al., 2011] ), deep brain stimulation of dentate-rubro-thalamo-(cortical) (DRT(C)) pathway, efferent motor projection of dentate nucleus, leads to improvement of tremor symptoms. Visualization of DRT (C), as proposed by several authors ( [Coenen et al., 2011] , [Keser et al., 2015] ), reconstructs connections between dentate nucleus (DN) and ruber nucleus (RN) using deterministic diffusion tensor tractography. However tracer primate studies show that motor projections read spread more than classically described pathway in ruber nucleus ( Dum and Strick, 2003 ). Well known is also that tremor suppressing effects are seen after deep brain stimulation of caudal zona incerta ( Fytagoridis et al., 2012 ) (cZI), which is dorsolateral to RN. We propose alternative way of DRT visualization with probabilistic connectivity evaluation between DN and anatomically defined ROI of hand and leg projection of primary motor cortex (PMC) on the ipsilateral side. Materials and methods We included MRI data of 16 Patients with essential tremor. DTI Imaging with 30 directions as well as 3D turbo spin echo and 3D mprage sequences produced on 1,5T Siemens Avanto scanner. Manual segmentation of seed regions of interest (ROI) in DN and in PMC was done as start–end landmarks of DRT (C). Reconstruction of pyramidal tract is done using PMC-ROI and medulla oblongata ROI. Reconstruction of probabilistic tractography maps was done in FSL Software (FMRIB, Oxford, UK). Tractography results transferred to standard MNI152 space, and mean images calculated (NPM, Mricron Software). Tractography result was analyzed using MNI152 based atlas tools. Results Connectivity maps showed high connectivity values inside of DRT (C), demonstrating similar path distribution and course in brainstem and thalamus. Tractography was able to visualize little connectivity to the contralateral motor cortex because of low resolution to depict fibers in decussation of upper cerebellar peduncle, as already reported from other authors ( Jbabdi et al., 2015 ). Crossed fibers located anterolatheral of those, which not cross. Fiber course differed from other tractography results in additional fibers going laterally from rubber nucleus. Conclusions Probabalistic tractography can reconstruct motor projections of DN. Even if more sophisticated to produce, probabilistic connectivity maps provide quantitative connection probability, hotspot of which can be used for stereotactic target planning. Further studies to compare deterministic and probabilistic approach to map DRT(C) are needed.

Erratum for Oyama G, Thompson A, Foote KD, et al. Deep brain stimulation for tremor associated with underlying ataxia syndromes: A case series and discussion of issues. Tremor Other Hyperkinet Mov. 2014; 4. doi: 10.7916/D8542KQ5

Erratum for Oyama G, Thompson A, Foote KD, et al. Deep brain stimulation for tremor associated with underlying ataxia syndromes: A case series and discussion of issues. Tremor Other Hyperkinet Mov. 2014; 4. doi: 10.7916/D8542KQ5

Deep Brain Stimulation in Neurological and Psychiatric Disorders.

Deep brain stimulation (DBS) is the chronic electrical stimulation of selected target sites in the brain through stereotactically implanted electrodes. More than 150 000 patients around the world have been treated to date with DBS for medically intractable conditions. The indications for DBS include movement disorders, epilepsy, and some types of mental illness. This review is based on relevant publications retrieved by a selective search in PubMed and the Cochrane Library, and on the current guidelines of the German Neurological Society (Deutsche Gesellschaft für Neurologie, DGN). DBS is usually performed to treat neurological diseases, most often movement disorders and, in particular, Parkinson's disease. Multiple randomized controlled trials (RCTs) have shown that DBS improves tremor, dyskinesia, and quality of life in patients with Parkinson's disease by 25% to 50%, depending on the rating scales used. DBS for tremor usually involves stimulation in the cerebello-thalamo-cortical regulatory loop. In an RCT of DBS for the treatment of primary generalized dystonia, the patients who underwent DBS experienced a 39.3% improvement of dystonia, compared to only 4.9% in the control group. Two multicenter trials of DBS for depression were terminated early because of a lack of efficacy. DBS is an established treatment for various neurological and psychiatric diseases. It has been incorporated in the DGN guidelines and is now considered a standard treatment for advanced Parkinson's disease. The safety and efficacy of DBS can be expected to improve with the application of new technical developments in electrode geometry and new imaging techniques. Controlled trials would be helpful so that DBS could be extended to further indications, particularly psychiatric ones.

Modulation of the cerebello-thalamo-cortical network in thalamic deep brain stimulation for tremor: a diffusion tensor imaging study.

Deep brain stimulation alleviates tremor of various origins. Several regions like the ventralis intermediate nucleus of thalamus, the caudal zona incerta, and the posterior subthalamic region are generally targeted. Previous work with fiber tractography has shown the involvement of the cerebello-thalamo-cortical network in tremor control. To report the results of a prospective trial in a group of patients with tremor who underwent post hoc tractographic analysis after treatment with traditional thalamic deep brain stimulation. A total of 11 patients (aged 64 ± 17 years, 6 male) were enrolled (essential tremor [6], Parkinson tremor [3], and myoclonic tremor in myoclonus dystonia [2]). Patients received 1 (3 patients), 2 (7 patients), or 3 (1 patient) quadripolar electrodes. A 32-direction diffusion tensor magnetic resonance imaging sequence was acquired preoperatively. Tractography was processed postoperatively for evaluation and the dentato-rubro-thalamic tract (DRT) was individually tracked. Electrode positions were determined with helical computed tomography. Electric fields (EFs) were simulated according to individual stimulation parameters in a standardized atlas brain space (ICBM-MNI 152). Tremor was reduced in all patients (69.4% mean) on the global (bilateral) tremor score. Effective contacts were located inside or in proximity to the DRT. In moderate tremor reduction (2 patients), the EFs were centered on its anterior border. In good and excellent tremor reduction (9 patients), EFs focused on its center. Deep brain stimulation of the cerebello-thalamo-cortical network reduces tremor. The DRT connects 3 traditional target regions for deep brain stimulation in tremor disease. Tractography techniques can be used to directly visualize the DRT and, therefore, optimize target definition in individual patients.

Deep Brain Stimulation for Tremor Associated with Underlying Ataxia Syndromes: A Case Series and Discussion of Issues

Deep Brain Stimulation for Tremor Associated with Underlying Ataxia Syndromes: A Case Series and Discussion of Issues