Intractable Essential Tremor Research Articles

Feasibility of Endovascular Deep Brain Stimulation of Anterior Nucleus of the Thalamus for Refractory Epilepsy.

Deep brain stimulation (DBS) has developed into an effective therapy for several disease states including treatment-resistant Parkinson disease and medically intractable essential tremor, as well as segmental, generalized and cervical dystonia, and obsessive-compulsive disorder (OCD). Dystonia and OCD are approved with Humanitarian Device Exemption. In addition, DBS is also approved for the treatment of epilepsy in the anterior nucleus of the thalamus. Although overall considered an effective treatment for Parkinson disease and epilepsy, a number of specific factors determine the treatment success for DBS including careful patient selection, effective postoperative programming of DBS devices and accurate electrode placement. Furthermore, invasiveness of the procedure is a rate limiter for patient adoption. It is desired to explore a less invasive way to deliver DBS therapy. Here, we report for the first time the direct comparison of endovascular and parenchymal DBS in a triplicate ovine model using the anterior nucleus of the thalamus as the parenchymal target for refractory epilepsy. Triplicate ovine studies show comparable sensing resolution and stimulation performance of endovascular DBS with parenchymal DBS. The results from this feasibility study opens up a new frontier for minimally invasive DBS therapy.

Long‐term outcome following magnetic resonance imaging‐guided focused ultrasound unilateral thalamotomy for medication‐refractory essential tremor

AbstractObjectiveTo investigate the long‐term outcome 5 years after transcranial magnetic resonance imaging‐guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (Vim) thalamotomy for essential tremor (ET), following our interim reports.MethodsThis was a prospective and open‐labeled study involving a single center. Ten medication‐refractory ET patients (8 men and 2 women, aged 67.1 ± 17.5 years, all right‐handed) underwent left MRgFUS Vim thalamotomy. They were assessed using the Clinical Rating Scale for Tremor (CRST) and the overall health and quality of life (QOL) scale of the Quality of Life in Essential Tremor Questionnaire (QUEST). Additionally, we assessed safety issues during the study period.ResultsRight‐hand tremor improved immediately after the procedure in all patients. The right‐hand CRST score remained significantly improved by 60.2% and 33.5% from baseline at both 1‐ and 5‐years post‐treatment, respectively (both p < 0.05). On the other hand, the left‐hand CRST score and the overall QOL score of QUEST showed no improvement. Adverse events during and immediately after the procedure were mild and reversible. We observed no delayed adverse events.ConclusionMRgFUS unilateral Vim thalamotomy is adopted as one of the therapeutic options for intractable ET. Further investigation of the methodology for accurate targeting and sonication is important to improve long‐term outcomes involving a larger number of patients. In addition, not only unilateral but also bilateral Vim thalamotomy may be necessary to achieve a better quality of life.

Unilateral Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy Thalamotomy for Essential Tremor.

Essential tremor (ET) affects numerous adults, impacting quality of life (QOL) and often defying pharmacological treatment. Surgical interventions like deep brain stimulation (DBS) and lesional approaches, including radiofrequency, gamma-knife radiosurgery, and magnetic resonance imaging (MRI)-guided focused ultrasound, offer solutions but are not devoid of limitations. This retrospective, single-center, single-blinded pilot study aimed to assess the safety and efficacy of unilateral MRI-guided laser interstitial thermal therapy (MRIg-LITT) thalamotomy for medically intractable ET. Nine patients with ET, unresponsive to medications and unsuitable for DBS, underwent unilateral MRIg-LITT thalamotomy. We assessed tremor severity, QOL, cognitive function, and adverse events (AE) over a 12-month period. Tremor severity significantly improved, with a reduction of 83.37% at 12 months post-procedure. QOL scores improved by 74.60% at 12 months. Reported AEs predominantly included transient dysarthria, proprioceptive disturbances, and gait balance issues, which largely resolved within a month. At 3 months, 2 patients (22%) exhibited contralateral hemiparesis requiring physiotherapy, with 1 patient (11%) exhibiting persistent hemiparesis at 12 months. No significant cognitive impairment was detected post-procedure. Unilateral MRIg-LITT thalamotomy yielded substantial and enduring tremor alleviation and enhanced QOL in patients with ET that is resistant to medication. The AE profile was acceptable. Our findings support the need for additional research with expanded patient cohorts and extended follow-up to corroborate these outcomes and to refine the role of MRIg-LITT as a targeted and minimally invasive approach for ET management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Posterior subthalamic area deep brain stimulation for recurrent tremor after ventral intermediate nucleus thalamotomy: a case report

Neurosurgical treatments, including both lesioning procedures and deep brain stimulation (DBS), are considered effective treatments for patients with intractable essential tremor (ET). However, it can be challenging to arrive at the decision to perform a second surgical attempt for recurrent ET after the initial neurosurgical treatment because of the uncertainty of successful results. We encountered a 49-year-old man who complained of recurrent tremor after ventral intermediate nucleus thalamotomy. The patient underwent DBS in the posterior subthalamic area (PSA), resulting in significantly reduced tremor and improved daily function. Although there are various surgical options for recurrent ET, DBS targeting the PSA induces favorable tremor control and can be successfully used as a salvage therapy after thalamotomy.

Technical and operative factors affecting magnetic resonance imaging-guided focused ultrasound thalamotomy for essential tremor: experience from 250 treatments.

Magnetic resonance imaging-guided focused ultrasound (MRgFUS) provides real-time monitoring of patients to assess tremor control and document any adverse effects. MRgFUS of the ventral intermediate nucleus (VIM) of the thalamus has become an effective treatment option for medically intractable essential tremor (ET). The aim of this study was to analyze the correlations of clinical and technical parameters with 12-month outcomes after unilateral MRgFUS thalamotomy for ET to help guide future clinical treatments. From October 2013 to January 2019, data on unilateral MRgFUS thalamotomy from the original pivotal study and continued-access studies from three different geographic regions were collected. Authors of the present study retrospectively reviewed those data and evaluated the efficacy of the procedure on the basis of improvement in the Clinical Rating Scale for Tremor (CRST) subscore at 1 year posttreatment. Safety was based on the rates of moderate and severe thalamotomy-related adverse events. Treatment outcomes in relation to various patient- and sonication-related parameters were analyzed in a large cohort of patients with ET. In total, 250 patients were included in the present analysis. Improvement was sustained throughout the 12-month follow-up period, and 184 (73.6%) of 250 patients had minimal or no disability due to tremor (CRST subscore < 10) at the 12-month follow-up. Younger age and higher focal temperature (Tmax) correlated with tremor improvement in the multivariate analysis (OR 0.948, p = 0.013; OR 1.188, p = 0.025; respectively). However, no single statistically significant factor correlated with Tmax in the multivariate analysis. The cutoff value of Tmax in predicting a CRST subscore < 10 was 55.8°C. Skull density ratio (SDR) was positively correlated with heating efficiency (β = 0.005, p < 0.001), but no significant relationship with tremor improvement was observed. In the low-temperature group, 1-3 repetitions to the right target with 52°C ≤ Tmax ≤ 54°C was sufficient to generate sustained tremor suppression within the investigated follow-up period. The high-temperature group had a higher rate of balance disturbances than the low-temperature group (p = 0.04). The authors analyzed the data of 250 patients with the aim of improving practices for patient screening and determining treatment endpoints. These results may improve the safety, efficacy, and efficiency of MRgFUS thalamotomy for ET.

Focused Ultrasound Thalamotomy for the Treatment of Essential Tremor: A 2-Year Outcome Study of Chinese People.

Background: Essential tremor (ET) is a common movement disorder among elderly individuals worldwide and is occasionally associated with a high risk for mild cognitive impairment and dementia. This retrospective study aimed to determine the clinical outcome of unilateral magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy in Chinese patients with ET.Methods: In total, 31 male and 17 female patients with drug-refractory ET were enrolled in this research study from January 2017 to September 2019. The severity of tremor and disability were assessed using the Clinical Rating Scale for Tremor (CRST) within a 2-year follow-up period.Results: The mean age of the participants was 59.14 ± 13.5 years. The mean skull density ratio (SDR) was 0.5 ± 0.1. The mean highest temperature was 57.0 ± 2.4°C. The mean number of sonications was 10.0 ± 2.6. The average maximum energy was 19,710.5 ± 8,624.9 J. The total CRST scores and sub-scores after MRgFUS thalamotomy significantly reduced during each follow-up (p < 0.001). All but four (8.3%) of the patients had reversible adverse events (AEs) after the procedure.Conclusions: MRgFUS had sustained clinical efficacy 2 years after treatment for intractable ET. Only few patients presented with thalamotomy-related AEs including numbness, weakness, and ataxia for an extended period. Most Chinese patients were treated safely and effectively despite their low SDR.

Diffusion tensor imaging‐based magnetic resonance imaging‐guided focused ultrasound thalamotomy for tremor recurrence after radiofrequency thalamotomy: A case report

AbstractWe report a 42‐year‐old, left‐handed woman with tremor recurrence after radiofrequency right ventral intermediate nucleus (Vim) thalamotomy for an intractable essential tremor. The recurring tremor of the left hand disappeared on conducting magnetic resonance imaging‐guided focused ultrasound (MRgFUS) right Vim thalamotomy based on diffusion tensor imaging (DTI). Referring the location of rubro‐thalamic‐cortical tract, we set the target medial to the prior lesion. Pre‐treatment evaluation with DTI could be important for an accurate targeting and a better outcome. Furthermore, MRgFUS Vim thalamotomy could become one of the options for tremor recurrence after surgical intervention.

Comparing Programming Sessions of Vim-DBS.

Background: Essential Tremor (ET) is a progressive neurological disorder characterized by postural and kinetic tremor most commonly affecting the hands and arms. Medically intractable ET can be treated by deep brain stimulation (DBS) of the ventral intermediate nucleus of thalamus (VIM). We investigated whether the location of the effective contact (most tremor suppression with at least side effects) in VIM-DBS for ET changes over time, indicating a distinct mechanism of loss of efficacy that goes beyond progression of tremor severity, or a mere reduction of DBS efficacy.Methods: We performed programming sessions in 10 patients who underwent bilateral vim-DBS surgery between 2009 and 2017 at our department. In addition to the intraoperative (T1) and first clinical programming session (T2) a third programming session (T3) was performed to assess the effect- and side effect threshold (minimum voltage at which a tremor suppression or side effects occurred). Additionally, we compared the choice of the effective contact between T1 and T2 which might be affected by a surgical induced “brain shift.”Discussion: Over a time span of about 4 years VIM-DBS in ET showed continuous efficacy in tremor suppression during stim-ON compared to stim-OFF. Compared to immediate postoperative programming sessions in ET-patients with DBS, long-term evaluation showed no relevant change in the choice of contact with respect to side effects and efficacy. In the majority of the cases the active contact at T2 did not correspond to the most effective intraoperative stimulation site T1, which might be explained by a brain-shift due to cerebral spinal fluid loss after neurosurgical procedure.

Two-year Follow-up Results of Magnetic Resonance Imaging-guided Focused Ultrasound Unilateral Thalamotomy for Medication-refractory Essential Tremor.

Objective To investigate the long-term efficacy and safety of magnetic resonance imaging-guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (Vim) thalamotomy for medication-refractory essential tremor (ET). Methods We performed MRgFUS left-sided Vim thalamotomy for 10 medication-refractory ET patients (8 men and 2 women, aged 67.1±17.5 years, all right-handed). We followed them for 2 years using the clinical rating scale for tremor (CRST) and the quality of life in essential tremor questionnaire (QUEST). Results Right-handed tremor improved immediately after the left Vim thalamotomy in all patients. The tremor became re-exacerbated in 2 patients by 6 months after treatment; however, an approximately 60% decrease in the average CRST score of the right hand persisted until 2 years. On the other hand, the average CRST score of the left hand and the average QUEST score showed no improvement. Headache was the most common adverse event during the sonication (8 patients), followed by a floating sensation (4 patients). On the other hand, sensory disturbances (4 patients) and gait instability (4 patients) were observed after the treatment, but most of them were mild and transient. There were no delayed adverse events. Conclusion MRgFUS unilateral Vim thalamotomy could be adopted as one of the therapeutic options for intractable ET. Further improvement of tremor in the targeted hand or contralateral Vim thalamotomy may be necessary to improve the quality of life.

Bilateral Posterior Subthalamic Area Deep Brain Stimulation for Essential Tremor: A Case Series.

BackgroundDeep brain stimulation (DBS) of the posterior subthalamic area (PSA) provides a potentially effective treatment for medication-refractory essential tremor (ET).ObjectiveTo study the clinical benefits and adverse-event profile of bilateral PSA-DBS for refractory ET.MethodsSeven patients with refractory ET underwent bilateral PSA-DBS surgery under general anesthesia between September 2017 and May 2018. Clinical outcome assessments, using the Essential Tremor Rating Scale, were performed at 1-, 6-, and 12-month follow-up, except for the last assessment of one patient who was followed up to 9 months. Analysis was focused on changes in patients’ motor symptoms and quality of life following surgery as well as documenting the adverse-event profile associated with the surgical PSA-DBS treatment.ResultsAfter surgery, patients’ motor symptoms, including upper limb tremor and head tremor, were improved by 84.2% and their quality of life by 81.25% at 1-month follow-up. The clinical benefits to patients were maintained at 6-month and last follow-up. Adverse side effects included dysarthria (n = 4), balance disorder (n = 2), and paresthesia of the right limb (n = 1). No habituation effects were observed throughout the follow-up.ConclusionBilateral PSA-DBS seems to offer an effective and safe alternative treatment for medically intractable ET, warranting further research into its clinical utility, adverse-event profile, and comparative effectiveness.

Deep Brain Stimulation Programming for Movement Disorders: Current Concepts and Evidence-Based Strategies.

Deep brain stimulation (DBS) has become the treatment of choice for advanced stages of Parkinson's disease, medically intractable essential tremor, and complicated segmental and generalized dystonia. In addition to accurate electrode placement in the target area, effective programming of DBS devices is considered the most important factor for the individual outcome after DBS. Programming of the implanted pulse generator (IPG) is the only modifiable factor once DBS leads have been implanted and it becomes even more relevant in cases in which the electrodes are located at the border of the intended target structure and when side effects become challenging. At present, adjusting stimulation parameters depends to a large extent on personal experience. Based on a comprehensive literature search, we here summarize previous studies that examined the significance of distinct stimulation strategies for ameliorating disease signs and symptoms. We assess the effect of adjusting the stimulus amplitude (A), frequency (f), and pulse width (pw) on clinical symptoms and examine more recent techniques for modulating neuronal elements by electrical stimulation, such as interleaving (Medtronic®) or directional current steering (Boston Scientific®, Abbott®). We thus provide an evidence-based strategy for achieving the best clinical effect with different disorders and avoiding adverse effects in DBS of the subthalamic nucleus (STN), the ventro-intermedius nucleus (VIM), and the globus pallidus internus (GPi).

Four-year follow-up results of magnetic resonance-guided focused ultrasound thalamotomy for essential tremor.

Following the emergence of magnetic resonance-guided focused ultrasound as a promising tool for movement disorder surgery, thalamotomy for essential tremor using this technique has become a useful tool based on its efficacy and lack of adverse effects. Here, we summarize the 4-year results of previous reports focusing on the durability of effectiveness of magnetic resonance-guided focused ultrasound thalamotomy for essential tremor. From October 2013 to August 2014, 15 patients with intractable essential tremor were enrolled. Twelve of them completed clinical assessment through 4 years of postoperative follow-up. Tremor severity, task performance, and disability were measured using the Clinical Rating Scale of Tremor. The mean age of the 12 patients was 61.7 ± 8.1 years. Maximally delivered energy was 15,552.4 ± 6574.1 joules. The mean number of sonications was 17.3 ± 1.6. The mean postoperative lesion volume was 82.6 ± 29.023 mm3 and in 1 year was a mean of 9.667 ± 8.573 mm3 . Four years postoperatively, improvement of the hand tremor score was 56%, that of the disability score was 63%, that of the postural score was 70%, and that of the action score was 63% compared with baseline; all improvements were significant and sustained over the 4-year period after thalamotomy. There was no permanent adverse effect throughout the 4-year follow-up period. Magnetic resonance-guided focused ultrasound thalamotomy exhibits sustained clinical efficacy 4 years after the treatment of intractable essential tremor. Adverse events are generally transient. A large cohort of patients who have undergone magnetic resonance-guided focused ultrasound thalamotomy with longer follow-up is needed to confirm our findings. © 2019 International Parkinson and Movement Disorder Society.

Skull Factors Affecting Outcomes of Magnetic Resonance-Guided Focused Ultrasound for Patients with Essential Tremor.

PurposeMagnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy has become a standard treatment for medically intractable essential tremor (ET). Skull density ratio (SDR) and skull volume in patients with ET are currently considered useful indicators of the successful application of MRgFUS. We compared the clinical outcomes of MRgFUS thalamotomy with SDR above 0.4 and 0.45. We also described patterns of SDR and skull volume in Korean patients with ET who were eligible to be screened for MRgFUS.Materials and MethodsIn screening 318 ET patients, we evaluated patterns of skull density and skull volume according to age and sex. Fifty patients with ET were treated with MRgFUS. We investigated the effects of SDR and skull volume on treatment parameters and the outcomes of ET.ResultsThe mean SDR of the 318 ET patients was 0.45±0.11, and that for skull volume was 315.74±40.95 cm3. The male patients had a higher SDR than female patients (p=0.047). Skull volume significantly decreased with aging. SDR and skull volume exhibited a linear negative relationship. Among therapeutic parameters, maximal temperature was positively related to SDR, while sonication number was not related to either SDR or skull volume. Tremor outcome was also not related to SDR or skull volume.ConclusionSDR varied widely from 0.11 to 0.73, and men had a higher SDR. Therapeutic parameters and clinical outcomes were not affected by SDR or skull volume.

Stereotactic radiosurgery for essential tremor: Retrospective analysis of a 19-year experience.

Essential Tremor (ET) is a common movement disorder that can be disabling. Initial treatment is in the form of medical therapies. Patients with medically refractory ET seek surgical intervention which include radiofrequency thalamotomy, deep brain stimulation, and radiosurgical thalamotomy. Radiosurgical thalamotomy is a minimally invasive surgical option which is especially valuable for elderly and high surgical risk patients. The purpose of this study was to retrospectively analyze the outcomes of stereotactic radiosurgery for patients suffering from medically refractory essential tremor. During a 19-year period (1996-2015), 73 patients underwent gamma knife thalamotomy for intractable essential tremor. A median central dose of 140 Gy (range, 130-150) was delivered to the nucleus ventralis intermedius through a single 4-mm isocenter. We used the Fahn-Tolosa-Marin clinical tremor rating scale to score tremor, handwriting, drawing, and ability to drink fluids. The median time to last follow-up was 28 months (range, 6-152). After gamma knife thalamotomy, 93.2% improved in tremor. Forty-four patients (60.3%) experienced tremor arrest or barely perceptible tremor. Eighteen patients (24.7%) noted tremor arrest and complete restoration of motor function. Tremor improvement was sustained at last follow-up in 96% of patients who experience tremor relief. Mean tremor score improved from 3.19 before to 1.27 after gamma knife thalamotomy (P < 0.0001). Mean handwriting score improved from 2.97 to 1.25 (P < 0.0001). Mean drawing score improved from 3.16 to 1.26 (P < 0.0001). Mean drinking score improved from 3.14 to 1.56 (P < 0.0001). Imaging follow-up showed three types of lesions: enhancing lesion, streaking along internal capsule on fluid-attenuated inversion recovery, and significant reactive changes. Three patients (4%) experienced temporary adverse radiation effects. Radiosurgery is a safe and valuable treatment option for medically refractory essential tremor, especially for the elderly or those with high surgical risk for DBS or radiofrequency thalamotomy. © 2017 International Parkinson and Movement Disorder Society.

Effects of Cerebellothalamic Tractotomy on Cognitive and Emotional Functioning in Essential Tremor: A Preliminary Study in 5 Essential Tremor Patients

Background: Subthalamic stereotactic interventions have recently caught renewed interest as a treatment for essential tremor (ET). However, it is not clear whether these interventions are associated with neurocognitive, mood or personality changes. Objective: To investigate neurocognition, neuropsychiatric functions and personality variables in patients with ET and to explore the neurocognitive and neuropsychiatric effects of cerebellothalamic tractotomy (CTT), a form of subthalamotomy. Methods: In our study, we investigated cognitive functions, frontal functions, mood and personality variables in 5 patients with intractable ET. Patients were tested before and 3 months after surgery using neuropsychological tests, clinical scales for depression, anxiety, anger regulation and a personality test. Results: Before surgery, ET patients showed normal neurocognitive function, a slightly elevated frontal lobe score in the dimensions mental control and memory, without being indicative of a frontal lesion, and no elevated depression or anxiety scores compared to norm values. After surgery, there was no change in neurocognitive function and no increase in depression or anxiety scores. Conclusion: In this exploratory study on 5 ET patients, CTT was not associated with alterations of mood or neurocognitive functions.

Effect of Ventralis Intermedius Thalamotomy on the Area in the Sensorimotor Cortex Activated by Passive Hand Movements: fMR Imaging Study

Stereotactic ventralis intermedius (Vim) thalamotomy is effective for essential tremor (ET) of the limb, but the effect on the activity of the sensorimotor cortex is still unclear. The functional changes in this cortical area of patients with ET after Vim thalamotomy were investigated using functional magnetic resonance (fMR) imaging. Six patients underwent Vim thalamotomy for medically intractable ET, predominantly in the right hand. 1.5-tesla fMR imaging was performed using the blood oxygenation level-dependent sequence, before and after Vim thalamotomy, during passive movements with right wrist flexion and extension. Before and after images were analyzed using SPM99 software. Activation in the sensorimotor cortex and supplementary motor area evoked by wrist passive movement was observed both before and after surgery. Group analysis of changes in the blood oxygenation level-dependent response revealed a significantly smaller activated area postoperatively. Activation at the fundus of the central sulcus was characteristically decreased. All patients showed marked improvement in tremor after Vim thalamotomy. No patient experienced neurological deficits. fMR imaging showed that activation at the fundus of the central sulcus evoked by passive wrist movement was suppressed after Vim thalamotomy in ET patients, probably due to disruption of the thalamocortical pathway. The fundus of the central sulcus (Brodmann area 3a) is likely to be one of the key relays in the tremor circuit.

Kinematic analysis of thalamic versus subthalamic neurostimulation in postural and intention tremor

Deep brain stimulation of the thalamus (thalamic DBS) is an established therapy for medically intractable essential tremor and tremor caused by multiple sclerosis. In both disorders, motor disability results from complex interaction between kinetic tremor and accompanying ataxia with voluntary movements. In clinical studies, the efficacy of thalamic DBS has been thoroughly assessed. However, the optimal anatomical target structure for neurostimulation is still debated and has never been analysed in conjunction with objective measurements of the different aspects of motor impairment. In 10 essential tremor and 11 multiple sclerosis patients, we analysed the effect of thalamic DBS through each contact of the quadripolar electrode on the contralateral tremor rating scale, accelerometry and kinematic measures of reach-to-grasp-movements. These measures were correlated with the anatomical position of the stimulating electrode in stereotactic space and in relation to nuclear boundaries derived from intraoperative microrecording. We found a significant impact of the stereotactic z-coordinate of stimulation contacts on the TRS, accelerometry total power and spatial deviation in the deceleration and target period of reach-to-grasp-movements. Most effective contacts clustered within the subthalamic area (STA) covering the posterior Zona incerta and prelemniscal radiation. Stimulation within this region led to a mean reduction of the lateralized tremor rating scale by 15.8 points which was significantly superior to stimulation within the thalamus (P < 0.05, student's t-test). STA stimulation resulted in reduction of the accelerometry total power by 99%, whereas stimulation at the ventral thalamic border (68%) or within the thalamus proper (2.5%) was significantly less effective (P < 0.01). Concomitantly, STA stimulation led to a significantly higher increase of tremor frequency and decrease in EMG synchronization compared to stimulation within the thalamus proper (P < 0.001). In reach-to-grasp movements, STA stimulation reduced the spatial variability of the movement path in the deceleration period by 28.9% and in the target period by 58.4%, whereas stimulation within the thalamus was again significantly less effective (P < 0.05), with a reduction in the deceleration period between 6.5 and 21.8% and in the target period between 1.2 and 11.3%. An analysis of the nuclear boundaries from intraoperative microrecording confirmed the anatomical impression that most effective electrodes were located within the STA. Our data demonstrate a profound effect of deep brain stimulation of the thalamic region on tremor and ataxia in essential tremor and tremor caused by multiple sclerosis. The better efficacy of stimulation within the STA compared to thalamus proper favours the concept of a modulation of cerebello-thalamic projections underlying the improvement of these symptoms.

Stereotactic Ventral Intermedial Thalamotomy for the Treatment of Essential Tremor:Results of a Series of 37 Patients

We have analyzed 43 ventral intermediate thalamotomies performed in our center for treatment of medically intractable essential tremor (ET) in 37 patients. The mean age of patients was 70.9 years (range 42–84), duration of symptoms 33.3 years (1–65). The surgery in all cases was performed with stereotactic technique using MRI or CT localization. Intraoperative neurophysiological confirmation of the target location was obtained using a macrostimulation technique. All patients experienced either complete abolition of the contralateral tremor or significant improvement in tremor intensity immediately after the surgery. At follow-up examination 1–13 months after the operation, 60.5% of patients had no tremor, and 13.9% had mild residual tremor without interference with daily life. Tremor recurrence was observed in 5 patients, all of whom underwent repeat ventral intermedial (VIM) thalamotomy with excellent results. Transient problems with speech and motor functions were observed after 15 thalamotomies, permanent hemiparesis and speech difficulties were seen in 6 patients. We conclude that VIM thalamotomy is a highly effective procedure for medically intractable ET and may be performed with no mortality and low morbidity rate.

The symptomatic and functional outcome of stereotactic thalamotomy for medically intractable essential tremor

Eight patients with medically refractory disabling essential tremor underwent ventralis lateralis (VL) thalamotomies; the procedure was unilateral in seven cases and bilateral (staged) in the other. Contralateral tremor remained absent or markedly reduced in all patients at the time of the most recent follow-up examinations, at a mean of 17.3 months after surgery. Disability was determined by a modified form of an established rating scale for tremor, and was reduced from a mean score of 21.1 (moderate grade) to 3.9 (absent grade) (p less than 0.001). Interestingly, voice tremor was abolished or significantly improved in 71.4% of patients with preoperative voice tremor. This feature has not been reported previously. Persistent surgical morbidity was limited to two patients with mild dysarthria and one with a mild cognitive impairment. There were no surgically related deaths. It is concluded that stereotactic VL thalamotomy is a treatment option for medically intractable disabling essential tremor.

Stereotactic thalamotomy for medically intractable essential tremor.

Objective surgical symptomatic outcome of ventrolateral (VL) thalamotomy specifically for essential tremor is uncommonly reported and functional outcome has not been investigated previously. In the present series, 7 patients underwent unilateral and 1 patient staged bilateral VL thalamotomies for disabling medically refractory essential tremor. At follow-up examination (mean 17.3 months, range 1-50 months), all patients enjoyed complete ablation or significant amelioration of the targeted tremor. Disability as determined by a modified form of an established rating scale for tremor was reduced from moderate (57%) or severe (43%) to absent (86%) or mild (14%). Interestingly, voice tremor was ablated or significantly improved in 71.4% of patients with preoperative voice tremor.