Vim Nucleus Research Articles

Evaluating functional connectivity differences between DBS ON/OFF states in essential tremor

Deep brain stimulation (DBS) targeting the ventral intermediate (Vim) nucleus of the thalamus is an effective treatment for essential tremor (ET). We studied 15 ​ET patients undergoing DBS to a major input/output tract of the Vim, the dentato-rubro-thalamic tract (DRTt), using resting state functional MRI (rsfMRI) to evaluate connectivity differences between DBS ON and OFF and elucidate significant regions most influential in impacting tremor control and/or concomitant gait ataxia. Anatomical/functional 1.5T MRIs were acquired and replicated for each DBS state. Tremor severity and gait ataxia severity were scored with DBS ON at optimal stimulation parameters and immediately upon DBS OFF. Whole brain analysis was performed using dual regression analysis followed by randomized permutation testing for multiple correction comparison. Regions of interest (ROI) analysis was also performed. All 15 patients had tremor improvement between DBS ON/OFF (p ​< ​0.001). Whole brain analysis revealed significant connectivity changes between states in the left pre-central gyrus and left supplemental motor area. Group analysis of ROIs revealed that, with threshold p ​< ​0.05, in DBS ON vs. OFF both tremor duration and tremor improvement were significantly correlated to changes in connectivity. A sub-group analysis of patients with greater ataxia had significantly decreased functional connectivity between multiple ROIs in the cortex and cerebellum when DBS was ON compared to OFF. Stimulation of the DRTt and concordant improvement of tremor resulted in connectivity changes seen in multiple regions outside the motor network; when combined with both structural and electrophysiologic connectivity, this may help to serve as a biomarker to improve DBS targeting and possibly predict outcome.

Probabilistic stimulation mapping from intra-operative thalamic deep brain stimulation data in essential tremor

Deep brain stimulation (DBS) is a therapy for Parkinson’s disease (PD) and essential tremor (ET). The mechanism of action of DBS is still incompletely understood. Retrospective group analysis of intra-operative data recorded from ET patients implanted in the ventral intermediate nucleus of the thalamus (Vim) is rare. Intra-operative stimulation tests generate rich data and their use in group analysis has not yet been explored. Objective. To implement, evaluate, and apply a group analysis workflow to generate probabilistic stimulation maps (PSMs) using intra-operative stimulation data from ET patients implanted in Vim. Approach. A group-specific anatomical template was constructed based on the magnetic resonance imaging scans of 6 ET patients and 13 PD patients. Intra-operative test data (total: n = 1821) from the 6 ET patients was analyzed: patient-specific electric field simulations together with tremor assessments obtained by a wrist-based acceleration sensor were transferred to this template. Occurrence and weighted mean maps were generated. Voxels associated with symptomatic response were identified through a linear mixed model approach to form a PSM. Improvements predicted by the PSM were compared to those clinically assessed. Finally, the PSM clusters were compared to those obtained in a multicenter study using data from chronic stimulation effects in ET. Main results. Regions responsible for improvement identified on the PSM were in the posterior sub-thalamic area (PSA) and at the border between the Vim and ventro-oral nucleus of the thalamus (VO). The comparison with literature revealed a center-to-center distance of less than 5 mm and an overlap score (Dice) of 0.4 between the significant clusters. Our workflow and intra-operative test data from 6 ET-Vim patients identified effective stimulation areas in PSA and around Vim and VO, affirming existing medical literature. Significance. This study supports the potential of probabilistic analysis of intra-operative stimulation test data to reveal DBS’s action mechanisms and to assist surgical planning.

Magnetic resonance-guided focused ultrasound unilateral thalamotomy for medically refractory essential tremor: 3-year follow-up data.

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy of the ventralis intermediate (Vim) nucleus is an "incisionless" treatment for medically refractory essential tremor (ET). We present data on 49 consecutive cases of MRgFUS Vim thalamotomy followed-up for 3 years and review the literature on studies with longer follow-up data. A retrospective chart review of patients who underwent MRgFUS thalamotomy (January 2018-December 2020) at our institution was performed. Clinical Rating Scale for Tremor (CRST) and Quality of Life in Essential Tremor (QUEST) scores were obtained pre-operatively and at each follow-up with an assessment of side effects. Patients had post-operative magnetic resonance imaging within 24 h and at 1 month to figure out lesion location, size, and extent. The results of studies with follow-up ≥3 years were summarized through a literature review. The CRST total (baseline: 58.6 ± 17.1, 3-year: 40.8 ± 18.0) and subscale scores (A + B, baseline: 23.5 ± 6.3, 3-year: 12.8 ± 7.9; C, baseline: 12.7 ± 4.3, 3-year: 5.8 ± 3.9) and the QUEST score (baseline: 38.0 ± 14.8, 3-year: 18.7 ± 13.3) showed significant improvement that was stable during the 3-year follow-up. Three patients reported tremor recurrence and two were satisfactorily retreated. Side effects were reported by 44% of patients (severe: 4%, mild and transient: 40%). The improvement in tremor and quality of life in our cohort was consistent with the literature. We confirmed the effectiveness and safety of MRgFUS Vim thalamotomy in medically refractory ET up to 3 years.

Magnetic Resonance-Guided Focused Ultrasound (MRgFUS)-Thalamotomy for Essential Tremor: Lesion Location and Clinical Outcomes.

Factors predicting clinical outcomes after MR-guided focused ultrasound (MRgFUS)-thalamotomy in patients with essential tremor (ET) are not well known. To examine the clinical outcomes and their relationship with patients' baseline demographic and clinical features and lesion characteristics at 6-month follow-up in ET patients. A total of 127 patients were prospectively evaluated at 1 (n = 122), 3 (n = 102), and 6 months (n = 78) after MRgFUS-thalamotomy. Magnetic resonance imaging (MRI) was obtained at 6 months (n = 60). Primary outcomes included: (1) change in the Clinical Rating Scale of Tremor (CRST)-A+B score in the treated hand and (2) frequency and severity of adverse events (AEs) at 6 months. Secondary outcomes included changes in all subitems of the CRST scale in the treated hand, CRST-C, axial tremor (face, head, voice, tongue), AEs, and correlation of primary outcomes at 6 months with lesion characteristics. Statistical analysis included linear mixed, standard, and logistic regression models. Scores for CRST-A+B, CRST-A, CRST-B in the treated hand, CRST-C, and axial tremor were improved at each evaluation (P < 0.001). Five patients had severe AEs at 1 month that became mild throughout the follow-up. Mild AEs occurred in 71%, 45%, and 34% of patients at 1, 3, and 6 months, respectively. Lesion volume was associated with the reduction in the CRST-A (P = 0.003) and its overlapping with the ventralis intermedius nucleus (Vim) nucleus with the reduction in CRST-A+B (P = 0.02) and CRST-B (P = 0.008) at 6 months. MRgFUS-thalamotomy improves hand and axial tremor in ET patients. Transient and mild AEs are frequent. Lesion volume and location are associated with tremor reduction. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Magnetic Resonance-Guided Focused Ultrasound for Treatment of Essential Tremor: Ventral Intermediate Nucleus Ablation Alone or Additional Posterior Subthalamic Area Lesioning?

Magnetic resonance-guided focused ultrasound (MRgFUS) for treatment of essential tremor (ET) traditionally targets the ventral intermediate (Vim) nucleus. Recent strategies include a secondary lesion to the posterior subthalamic area (PSA). The aim was to compare lesion characteristics, tremor improvement, and adverse events (AE) between patients in whom satisfactory tremor suppression was achieved with lesioning of the Vim alone and patients who required additional lesioning of the PSA. Retrospective analysis of data collected from ET patients treated with MRgFUS at St Vincent's Hospital Sydney was performed. Clinical Rating Scale for Tremor (CRST), hand tremor score (HTS), and Quality of Life in Essential Tremor Questionnaire (QUEST) were collected pre- and posttreatment in addition to the prevalence of AEs. The lesion coordinates and overlap with the dentatorubrothalamic tract (DRTT) were evaluated using magnetic resonance imaging. Twenty-one patients were treated in Vim only, and 14 were treated with dual Vim-PSA lesions. Clinical data were available for 29 of the 35 patients (19 single target and 10 dual target). At follow-up (mean: 18.80 months) HTS, CRST, and QUEST in single-target patients improved by 57.97% (P < 0.001), 36.71% (P < 0.001), and 58.26% (P < 0.001), whereas dual-target patients improved by 68.34% (P < 0.001), 35.37% (P < 0.003), and 46.97% (P < 0.005), respectively. The Vim lesion of dual-target patients was further anterior relative to the posterior commissure (PC) (7.84 mm), compared with single-target patients (6.92 mm), with less DRTT involvement (14.85% vs. 23.21%). Dual-target patients exhibited a greater proportion of patients with acute motor AEs (100% vs. 58%); however, motor AE prevalence was similar in both groups at long-term follow-up (33% vs. 38%). Posterior placement of lesions targeting the Vim may confer greater tremor suppression. The addition of a PSA lesion, in patients with inadequate tremor control despite Vim lesioning, had a trend toward better long-term tremor suppression; however, this approach was associated with greater prevalence of gait disturbance in the short term.

Limb Preference Changes after Focused-Ultrasound Thalamotomy for Tremor.

Magnetic resonance-guided focused-ultrasound (MRgFUS) thalamotomy is an effective treatment for essential and other tremors. It targets the ventrointermedius (Vim) nucleus, which is the thalamic relay in a proprioceptive pathway, and contains kinesthetic cells. Although MRgFUS thalamotomy reduces some risks associated with more invasive surgeries, it still has side effects, such as balance and gait disturbances; these may be caused by the lesion impacting proprioception. Our aim was to quantitatively measure the effects of MRgFUS on proprioception and limb use in essential tremor patients. We hypothesized that this thalamotomy alters proprioception, because the sensorimotor Vim thalamus is lesioned. Proprioception was measured using the Kinarm exoskeleton robot in 18 patients. Data were collected pre-operatively, and then 1 day, 3 months, and 1 year after surgery. Patients completed four tasks, assessing motor coordination and postural control, goal-directed movement and bimanual planning, position sense, and kinesthesia. Immediately after surgery there were changes in posture speed (indicating tremor improvement), and in bimanual hand use, with the untreated limb being preferred. However, these measures returned to pre-operative baseline over time. There were no changes in parameters related to proprioception. None of these measures correlated with lesion size or lesion-overlap with the dentato-rubro-thalamic tract. This is the first quantitative assessment of proprioception and limb preference following MRgFUS thalamotomy. Our results suggest that focused-ultrasound lesioning of the Vim thalamus does not degrade proprioception but alters limb preference. This change may indicate a required "relearning" in the treated limb, because the effect is transient. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Deep Brain Stimulation for Holmes Tremors and Literature Review.

Deep Brain Stimulation for Holmes Tremors and Literature Review.

Does Head Tremor Predict Postural Instability After Bilateral Thalamic Stimulation in Essential Tremor?

Essential tremor (ET) may present with head tremor (HT), of presumed cerebellar nature. Deep brain stimulation (DBS) targeting the ventral intermediate (Vim) nucleus of the thalamus is a highly effective therapy for medication-refractory ET. However, stimulation-related side effects may include cerebellar abnormalities, such as postural instability. This retrospective cohort study evaluated the risk of post-Vim DBS postural instability (primary outcome measure) in patients with versus without head tremor (HT vs. nHT). The primary outcome measure, namely post-DBS postural instability, was assessed in both groups using a Wilcoxon rank sum t-test. The time to postural instability was determined using Cox proportional hazards regression analysis adjusted for age and sex. Out of 30 patients analyzed during the follow up period, there was similar postural instability detected in HT (9/14, 64%) and nHT patients (11/16, 69%) at 24 months post-Vim DBS (p=0.82), adjusted hazard ratio[aHR]=0.82, p=0.69). These data suggest that the presence or absence of HT does not have an impact on postural instability after bilateral Vim DBS in patients with ET.

Increased movement-related signals in both basal ganglia and cerebellar output pathways in two children with dystonia.

The contribution of different brain regions to movement abnormalities in children with dystonia is unknown. Three awake subjects undergoing depth electrode implantation for assessments of potential deep brain recording targets performed a rhythmic figure-8 drawing task. Two subjects had dystonia, one was undergoing testing for treatment of Tourette Syndrome and had neither dystonia nor abnormal movements during testing. Movement-related signals were evaluated by determining the magnitude of task-related frequency components. Brain signals were recorded in globus pallidus internus (GPi), the ventral oralis anterior/posterior (VoaVop) and the ventral intermediate (Vim) nuclei of the thalamus. In comparison to the subject without dystonia, both children with dystonia showed increased task-related activity in GPi and Vim. This finding is consistent with a role of both basal ganglia and cerebellar outputs in the pathogenesis of dystonia. Our results further suggest that frequency analysis of brain recordings during cyclic movements may be a useful tool for analysis of the presence of movement-related signals in various brain regions.

P 23 The overlap of lesions placed by MRIgFUS with the cerebellothalamic tract does not adequately explain symptom control in ET

Background: The thalamic ventral intermediate (Vim) nucleus is part of a network that appears to be disrupted in essential tremor (ET) and is the most relevant target of functional neurosurgery to alleviate ET symptoms. As the most important afferent of the VIM, the cerebellothalamic tract (CTT) transmits information from cerebellar nuclei. Disruption of this tract - in the past via subthalatomies and in the present via deep brain stimulation is considered the best option of tremor treatment, partly because of the high anatomical density of CTT fibers before entering the VIM, and partly because of the greater distance to sensory thalamic nuclei. Recently, initial pilot studies have also documented transcranial MRI-guided high-intensity focused ultrasound (MRIgFUS) as an effective treatment modality. Unilateral MRIgFUS lesioning was highly efficacious in reducing contralateral hand tremor in ET with mild and transient adverse effects. However, targeting of MRIgFUS has so far been based on MRI imaging without dedicated evidence of the underlying connectome. Here, we test a method for quantitative analysis of the involved fiber tracts and test whether the measured clinical effect correlates with overlap of the set lesion with individual fiber tracts, such as CTT. Materials and Methods: We revisited pre- and post-procedural MRIs of 6 ET patients (Øage 70,7 (± 8,5) years , Ø Tremor rating (TR) (pre): 43,8 (± 9,8)) who underwent unilateral ablation of the CTT by MRIgFUS. The images, obtained 48 hours (48H) and 3-6 months (3M+) after the procedure, were used to create 3D-models of the lesions which were localized within MNI-space with the pre-procedural MRI and atlas registration using Suretune®. The models were subsequently used to calculate interferences with fiber tracts. A linear model was employed to assess the correlation between the quantitative interference and improvement of the clinical score at two timepoints after the procedure (48H, n=6: TR: 16,7 (±5,5) ; 3M+, n= 5: TR: 19,2 (±7,2)). Results: The lesions volume differed between the 48H (Ø 281.78mm3(±77.77), n=6) and 3M+(Ø 53.82mm3(±22), n=5) conditions (p<0.01). After 48H primarily the CTT (Ø72,4 % (±34)) but also the M1 (Ø36,05 % (±43)) interfered, while after 3M+ the overlap reduced tremendously for the CTT (Ø1% (±1,6), p=0.017) and slightly for the M1(Ø26,7% (±28,4), p=0.67). Preliminary results could not show a correlation between the observed clinical improvement with the interference of the lesions with a specific tract. Discussion: Interestingly, there is no clear correlation between clinical outcome and the overlap between the lesion placed by MRIgFUS and the fibers of the CTT. This might indicate that the observed clinical effect would have to be explained only partially by the targeted CTT but also by other fiber tracts. The data set was too small for a meaningful multivariate regression analysis, but pooling data sets from different centers may mean a solution to this problem in the future.

3T magnetic resonance-guided focused ultrasound thalamotomy in patients with essential tremor: Three-year clinical experience from a single center

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy of the ventralis intermedius (Vim) nucleus is emerging as a minimally invasive treatment for patients with disabling and medication-refractory essential tremor (ET). We report our preliminary three-year experience on 52 patients with ET treated from January 2018 to December 2020 in a single center.

Radiofrequency Ablation for Movement Disorders: Risk Factors for Intracerebral Hemorrhage, a Retrospective Analysis.

One of the greatest concerns associated with radiofrequency ablation is intracerebral hemorrhage (ICH). However, the majority of previous studies have mainly evaluated Parkinson disease patients with ablation of the globus pallidus internus (GPi). To investigate the hemorrhagic risk associated with radiofrequency ablation using ventro-oral (Vo) nucleus, ventral intermediate (Vim) nucleus, GPi, and pallidothalamic tract. Radiofrequency ablations for movement disorders from 2012 to 2019 at our institution were retrospectively analyzed. Multivariate analyses were performed to evaluate associations between potential risk factors and ICH. A total of 558 patients underwent 721 stereotactic radiofrequency ablations for movement disorders. Among 558 patients, 356 had dystonia, 111 had essential tremor, and 51 had Parkinson disease. Among 721 procedures, the stereotactic targets used in this study were as follows: Vo: 230; Vim: 199; GPi: 172; pallidothalamic tract: 102; Vim/Vo: 18. ICH occurred in 37 patients (5.1%, 33 with dystonia and 4 with essential tremor). Symptomatic ICH developed in 3 Vo nuclei (1.3%), 3 Vim nuclei (1.5%), and 2 GPi (1.2%). Hypertension (odds ratio=2.69, P=.0013), higher number of lesions (odds ratio=1.23, P=.0221), and younger age (odds ratio=1.04, P=.0055) were significant risk factors for ICH associated with radiofrequency ablation. The present study revealed that younger age, higher number of lesions, and history of hypertension were independent risk factors for ICH associated with stereotactic radiofrequency ablation.

Radiofrequency Lesioning Surgery for Movement Disorders

Radiofrequency lesioning surgery is primarily performed to treat Parkinson's disease, dystonia, and tremor. Its effects are similar to those of deep brain stimulation (DBS). However, Radiofrequency lesioning surgery has not been popularized, possibly due to the over-evaluation of its risks. The current most available targets for the treatment of movement disorders include ventral intermediate (Vim) nucleus, ventral oral (Vo) nucleus, and globus pallidus internus (GPi). Vim thalamotomy is available for Parkinsonian tremor, essential tremor, dystonic tremor, and other various kinds of tremor, and it is highly effective. Bilateral vim thalamotomy is feasible when properly performed on tiny lesions on the bilateral vim nucleus. Vo thalamotomy is mainly available for focal hand dystonia. The safety profile of bilateral Vo thalamotomy has not yet been established, but it is thought that it may lead to irreversible hypophonia and dysarthria. Pallidotomy is selected for treatment of dystonia and Parkinson's disease. Although unilateral pallidotomy is a safe procedure, it can cause medically refractory parkinsonism including postural reflex disturbance and gait disorder. Delayed infarction on the posterior limb of internal capsule is another major concern associated with pallidotomy and can lead to hemiparesis. Correct understanding is absolutely essential to ensure the safety of radiofrequency lesioning surgery.

Micro-electrode Recordings in Stereotactic Functional Neurosurgery

Accurate targeting to the sensorimotor territory of the globus pallidus internus (GPi), the subthalamic nucleus (STN), and the thalamic ventral intermediate nucleus (Vim) is crucial for the stereotactic neurosurgery of lesioning or implantation of a deep brain stimulation electrode. Intra-operative micro-electrode recording can aid in the localization of these structures. Neurons in the GPi are characterized by high-frequency tonic discharge. The STN has a high density of neurons that show irregular discharge. The majority of neurons in the sensorimotor territory of the GPi and STN exhibit neuronal responses to passive manipulation or active movement of the limbs and orofacial parts, and they are somatotopically arranged. Neurons responding to movements of the legs, arms, and face were found along the dorsal-ventral axis in the posterolateral GPi and along the medial-lateral axis in the posterolateral STN. Similarly, in the lateral part of the thalamic Vim nucleus, most neurons exhibit kinesthetic responses that show well-organized somatotopic arrangement, with the leg on the dorsolateral side, arm on the medioventral side, and face on the more medial side. Some Vim neurons have rhythmic bursting discharges synchronous with limb tremor. These electrophysiological findings allow us to achieve better surgical results.

Comparative evaluation of tractography-based direct targeting and atlas-based indirect targeting of the ventral intermediate (Vim) nucleus in MRgFUS thalamotomy

To analyze and compare direct and indirect targeting of the Vim for MRgFUS thalamotomy. We retrospectively evaluated 21 patients who underwent unilateral MRgFUS Vim ablation and required targeting repositioning during the procedures. For each patient, in the three spatial coordinates, we recorded: (i) indirect coordinates; (ii) the coordinates where we clinically observed tremor reduction during the verification stage sonications; (iii) direct coordinates, measured on the dentatorubrothalamic tract (DRTT) at the after postprocessing of DTI data. The agreement between direct and indirect coordinates compared to clinically effective coordinates was evaluated through the Bland–Altman test and intraclass correlation coefficient. The median absolute percentage error was also calculated. Compared to indirect targeting, direct targeting showed inferior error values on the RL and AP coordinates (0.019 vs. 0.079 and 0.207 vs. 0.221, respectively) and higher error values on the SI coordinates (0.263 vs. 0.021). The agreement between measurements was higher for tractography along the AP and SI planes and lower along the RL planes. Indirect atlas-based targeting represents a valid approach for MRgFUS thalamotomy. The direct tractography approach is a valuable aid in assessing the possible deviation of the error in cases where no immediate clinical response is achieved.

The Brain Connectome after Gamma Knife Radiosurgery of the Ventro-Intermediate Nucleus for Tremor: Marseille-Lausanne Radiobiology Study Protocol

Essential tremor (ET) is the most common movement disorder. Deep brain stimulation is the current gold standard for drug-resistant tremor, followed by radiofrequency lesioning. Stereotactic radiosurgery by Gamma Knife (GK) is considered as a minimally invasive alternative. The majority of procedures aim at the same target, thalamic ventro-intermediate nucleus (Vim). The primary aim is to assess the clinical response in relationship to neuroimaging changes, both at structural and functional level. All GK treatments are uniformly performed in our center using Guiot’s targeting and a radiation dose of 130 Gy. MR neuroimaging protocol includes structural imaging (T1-weighted and diffusion-weighted imaging [DWI]), resting-state functional MRI, and ¹⁸F-fluorodeoxyglucose-positron emission tomography. Neuroimaging changes are studied both at the level of the cerebello-thalamo-cortical tract (using the prior hypothesis based upon Vim’s circuitry: motor cortex, ipsilateral Vim, and contralateral cerebellar dentate nucleus) and also at global brain level (no prior hypothesis). This protocol aims at using modern neuroimaging techniques for studying Vim GK radiobiology for tremor, in relationship to clinical effects, particularly in ET patients. In perspective, using such an approach, patient selection could be based upon a specific brain connectome profile.

A novel local field potential-based functional approach for targeting the centromedian-parafascicular complex for deep brain stimulation

BackgroundThe centromedian-parafascicular (Cm-Pf) complex of the thalamus is a common deep brain stimulation (DBS) target for treatment of Tourette syndrome (TS). Currently, there are no standardized functional intraoperative neurosurgical targeting approaches. Collectively, these issues have led to variability in DBS lead placement. Therefore, more defined methods are needed to improve targeting accuracy. ObjectiveThe objective of this observational study was to develop and to verify a functional mapping task capable of differentiating the Cm-Pf region from the nearby ventral intermediate (Vim) nucleus region of the thalamus. The overarching goal was to improve the reproducibility of DBS targeting in the Cm-Pf region. MethodsSeven TS patients completed a modified Go/NoGo task (five in the post-operative setting and two in the intra-operative setting). Post-operative neural signals from Cm-Pf region were collected using sensing-enabled implanted neural stimulators, and intraoperative neural signals from the Cm-Pf region were collected using an external amplifier. Event-related potential (ERP) features were identified by using the grand-average of stimulus onset signals derived from the postoperative participants. These features were correlated with anatomical locations for the specific electrode recordings. The same features were extracted from the intraoperative patients in order to verify electrode positions in the operating room environment. ResultsTwo features – a positive and a negative deflection – were identified in the average ERP from the post-operative participants. The peak amplitudes of both features were significantly correlated with the electrode depth position (p = 0.025 for positive deflection and p = 0.039 for negative deflection). The same result was reproduced intra-operatively in the two most recent patients, where more ventral electrode contacts revealed stronger peak amplitudes in comparison to the dorsal electrode contacts. ConclusionThis process was used to physiologically confirm accurate lead placement in the operating room setting. The modified Go/NoGo task elicited robust neural responses in the Cm-Pf region however the signal was not present in the Vim nucleus region of thalamus along the DBS electrode trajectory. We conclude that the differences in ERP responses may be a potentially novel LFP based functional approach for future targeting of the Cm-Pf complex for TS DBS.

Simultaneous combined unilateral ventralis intermedius (VIM) thalamotomy and contralateral VIM deep brain stimulation for head tremor: A case report

AbstractHead tremor usually requires bilateral deep brain stimulation of ventralis intermedius nucleus of thalamus. Ablation of VIM nucleus (VIM thalamotomy) is applied for limb tremor unilaterally because of serious complications from bilateral thalamotomy. Therefore, effects of thalamotomy on head tremor have been rarely reported. We report a successful long‐term outcome of head tremor with combined unilateral VIM thalamotomy and contralateral VIM‐DBS simultaneously. The patient was a 49‐year‐old man with head and bilateral hand tremors. His Fahn‐Tolosa‐Marin Tremor Rating Scale scores (head tremor score, range 8‐0, higher scores indicate greater severity) before and after the surgery were 8 and 0, respectively. Only transient tongue numbness was confirmed as a surgical complication. At the final follow‐up (36 months), the patient was completely free from tremor of the head and bilateral hands. Combined thalamotomy and DBS can be an alternative treatment option for head tremor.

Asleep Deep Brain Stimulation of the Nucleus Ventralis Intermedius for Essential Tremor Using Indirect Targeting and Interventional Magnetic Resonance Imaging: Single-Institution Case Series.

Literature on asleep deep brain stimulation (DBS) of the ventralis intermedius (Vim) nucleus in essential tremor is relatively sparse. Furthermore, controversy exists as to whether indirect ("consensus" or "atlas-based") targeting of the Vim requires physiologic adjustment for effective clinical outcomes in DBS surgery. The objective of this study was to evaluate the clinical results of asleep Vim DBS using indirect coordinates and real-time interventional magnetic resonance imaging guidance. Retrospective review of a prospectively collected database was performed to identify patients with essential tremor undergoing asleep Vim DBS using interventional magnetic resonance imaging guidance. Stereotactic and clinical outcomes were abstracted and analyzed using descriptive statistics. A total of 12 consecutive patients were identified, all of whom were available for 6-month clinical follow-up. Stereotactic (radial) error was 0.5 ± 0.2 mm on the left and 0.5 ± 0.3 mm on the right. Fahn-Tolosa-Marin tremor scores in the treated limb(s) decreased by 71.2% ± 31.0% (P = 0.0088), The Essential Tremor Rating Assessment Scale activities of daily living improved by 74.9% ± 23.7% (P < 0.0001), and The Essential Tremor Rating Assessment Scale performance improved by 64.3 ± 16.2% (P = 0.0004). Surgical complications were mild and generally transient. Stimulation-related side effects were similar to those reported in historical series of awake Vim DBS. Asleep Vim DBS using indirect targeting and interventional magnetic resonance imaging-guided placement is safe and effective, with 6-month clinical results similar to those achieved with awake placement. These data support the use of asleep surgery in essential tremor and represent a baseline for comparison with future studies using more advanced targeting techniques.

Vim line technique thalamotomy for Parkinson tremor: Case series

IntroductionThe ventral intermediate (Vim) nucleus of the thalamus is difficult to identify even with 3 T magnetic resonance imaging. Stereotactic Vim thalamotomy is a usual procedure to control Parkinson tremor. Successful relieving of the tremor depends on the accuracy of defining the Vim location. Presentation of casesThree patients with Parkinson tremor were subjected to stereotactic thalamotomy using the Vim line technique (VLT) so as to precisely determine the Vim location. All patients showed good results, with improved tremors, as indicated by the UPDRS score, without any complications. DiscussionThe precise targeting of the Vim nucleus is crucial importance for the successful Vim thalamotomy. Various method has been developed to determine Vim location. Atlas based and Guiot’s technique routinely used by neurosurgeon. VLT is a new technique that has been developed to determine the Vim location on MRI. ConclusionVLT is useful for the determination of the Vim location. However, further research is warranted to prove its effectiveness.