Computerised analysis of writing and drawing by essential tremor phenotype

We investigated whether computerised analysis of writing and drawing could discriminate essential tremor (ET) phenotypes according to the 2018 Consensus Statement on the Classification of Tremors. The Consensus scheme emphasises soft additional findings, mainly motor, that do not suffice to diagnose another tremor syndrome. Ten men and nine women were classified by blinded assessors according to Consensus Axis 1 definitions of ET and ET plus. Blinded scoring of tremor severity and alternating limb movement was also conducted. Twenty healthy participants acted as controls. Four writing and three drawing tasks were performed on a Wacom Intuos Pro Large digital tablet with a pressure-sensor mounted ink pen. Sixty-seven computerised measurements were obtained, comprising static (dimensional and temporal), kinematic and pen pressure features. The mean age of ET participants was 67.2±13.0 years and mean tremor duration was 21.7±19.0 years. Six were classified as ET, five had one plus feature and eight had two plus features. The computerised analysis could predict the presence and number of ET plus features. Measures of acceleration and variation of pen pressure performed strongly to separate ET phenotypes (p<0.05). Plus features were associated with higher scores on the Fahn-Tolosa-Marin Tremor Rating Scale (p=0.001) and it appeared that ET groups were mainly being separated according to severity of tremor and by compensatory manoeuvres used by participants with more severe tremor. There were, in addition, a small number of negative kinematic correlations suggesting some slowness with ET plus. Abnormal repetitive limb movement was also correlated with tremor severity (R=0.57) by clinical grading. Critics of the Consensus Statement have drawn attention to weaknesses of the ET plus concept in relation to duration and severity of ET. This classification of ET may be too biased towards tremor severity to assist in distinguishing underlying biological differences by clinical measurement.

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Sporadic Schwannomatosis: A Systematic Review Following the 2005 Consensus Statement

Journal of Neurological Surgery Part A Central European Neurosurgery ◽

10.1055/s-0038-1655548 ◽

2018 ◽

Vol 79 (05) ◽

pp. 408-415 ◽

Cited By ~ 1

Author(s):

Jan Victor ◽

Thibault Poujade ◽

Nadine Hollevoet ◽

Gregoire Chick

Keyword(s):

Systematic Review ◽

Consensus Statement ◽

Case Reports ◽

Case Series ◽

Spinal Tumors ◽

The Mean ◽

Tumor Distribution ◽

Key Aspects ◽

Number Of Individuals

Aims To identify the frequency of reports of sporadic schwannomatosis, the types of patients affected, and the nerves affected. Patients and Methods We identified all case reports and case series that reported on patients with sporadic schwannomatosis according to established criteria. Results The initial search yielded 1,597 studies, of which 15 were included. A total of 38 of 55 individuals met the inclusion criteria. The mean age of the patients was 48 years; 41% were male. Thirty-three patients had peripheral nerve tumors, and 17 had spinal tumors. Twelve had tumors in both locations. Tumor distribution was unilateral in 25 of 30 cases (83.3%) and segmental (limited to one limb or five or fewer contiguous segments of the spine) in 28 of 38 cases (73.7%). Conclusion This systematic review quantified the number of individuals who meet the criteria for sporadic schwannomatosis and better described this population to facilitate the classification of neurofibromatosis in regard to the 2005 consensus statement. Unilateral or segmental distribution of nerve tumors are key aspects when dealing with multiple noncutaneous schwannomas without involvement of the vestibular nerve.

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Longitudinal follow-up with VIM thalamic deep brain stimulation for dystonic or essential tremor

Neurology ◽

10.1212/wnl.0000000000008875 ◽

2020 ◽

Vol 94 (10) ◽

pp. e1073-e1084 ◽

Cited By ~ 6

Author(s):

Takashi Tsuboi ◽

Zakia Jabarkheel ◽

Pamela R. Zeilman ◽

Matthew J. Barabas ◽

Kelly D. Foote ◽

...

Keyword(s):

Deep Brain Stimulation ◽

Essential Tremor ◽

Brain Stimulation ◽

Rating Scale ◽

Statistical Significance ◽

Ventral Intermediate Nucleus ◽

Deep Brain

ObjectiveTo assess longitudinal tremor outcomes with ventral intermediate nucleus deep brain stimulation (VIM DBS) in patients with dystonic tremor (DT) and to compare with DBS outcomes in essential tremor (ET).MethodsWe retrospectively investigated VIM DBS outcomes for 163 patients followed at our center diagnosed with either DT or ET. The Fahn-Tolosa-Marin tremor rating scale (TRS) was used to assess change in tremor and activities of daily living (ADL) at 6 months, 1 year, 2–3 years, 4–5 years, and ≥6 years after surgery.ResultsTwenty-six patients with DT and 97 patients with ET were analyzed. Compared to preoperative baseline, there were significant improvements in TRS motor up to 4–5 years (52.2%; p = 0.032) but this did not reach statistical significance at ≥6 years (46.0%, p = 0.063) in DT, which was comparable to the outcomes in ET. While the improvements in the upper extremity tremor, head tremor, and axial tremor were also comparable between DT and ET throughout the follow-up, the ADL improvements in DT were lost at 2–3 years follow-up.ConclusionOverall, tremor control with VIM DBS in DT and ET was comparable and remained sustained at long term likely related to intervention at the final common node in the pathologic tremor network. However, the long-term ADL improvements in DT were not sustained, possibly due to inadequate control of concomitant dystonia symptoms. These findings from a large cohort of DT indicate that VIM targeting is reasonable if the tremor is considerably more disabling than the dystonic features.Classification of evidenceThis study provides Class IV evidence that VIM DBS improves tremor in patients with DT or ET.

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Magnetic resonance–guided focused ultrasound thalamotomy for tremor: a report of 30 Parkinson's disease and essential tremor cases

Journal of Neurosurgery ◽

10.3171/2016.10.jns16758 ◽

2018 ◽

Vol 128 (1) ◽

pp. 202-210 ◽

Cited By ~ 70

Author(s):

Menashe Zaaroor ◽

Alon Sinai ◽

Dorith Goldsher ◽

Ayelet Eran ◽

Maria Nassar ◽

...

Keyword(s):

Quality Of Life ◽

Parkinson’S Disease ◽

Parkinson's Disease ◽

Adverse Events ◽

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Innovative Technology ◽

The Mean

OBJECTIVEThalamotomy of the ventral intermediate nucleus (VIM) is effective in alleviating medication-resistant tremor in patients with essential tremor (ET) and Parkinson's disease (PD). MR-guided focused ultrasound (MRgFUS) is an innovative technology that enables noninvasive thalamotomy via thermal ablation.METHODSPatients with severe medication-resistant tremor underwent unilateral VIM thalamotomy using MRgFUS. Effects on tremor were evaluated using the Clinical Rating Scale for Tremor (CRST) in patients with ET and by the motor part of the Unified Parkinson's Disease Rating Scale (UPDRS) in patients with PD and ET-PD (defined as patients with ET who developed PD many years later). Quality of life in ET was measured by the Quality of Life in Essential Tremor (QUEST) questionnaire and in PD by the PD Questionnaire (PDQ-39).RESULTSThirty patients underwent MRgFUS, including 18 with ET, 9 with PD, and 3 with ET-PD. The mean age of the study population was 68.9 ± 8.3 years (range 46–87 years) with a mean disease duration of 12.1 ± 8.9 years (range 2–30 years). MRgFUS created a lesion at the planned target in all patients, resulting in cessation of tremor in the treated hand immediately following treatment. At 1 month posttreatment, the mean CRST score of the patients with ET decreased from 40.7 ± 11.6 to 9.3 ± 7.1 (p < 0.001) and was 8.2 ± 5.0 six months after treatment (p < 0.001, compared with baseline). Average QUEST scores decreased from 44.8 ± 12.9 to 13.1 ± 13.2 (p < 0.001) and was 12.3 ± 7.2 six months after treatment (p < 0.001). In patients with PD, the mean score of the motor part of the UPDRS decreased from 24.9 ± 8.0 to 16.4 ± 11.1 (p = 0.042) at 1 month and was 13.4 ± 9.2 six months after treatment (p = 0.009, compared with baseline). The mean PDQ-39 score decreased from 38.6 ± 16.8 to 26.1 ± 7.2 (p = 0.036) and was 20.6 ± 8.8 six months after treatment (p = 0.008). During follow-up of 6–24 months (mean 11.5 ± 7.2 months, median 12.0 months), tremor reappeared in 6 of the patients (2 with ET, 2 with PD, and 2 with ET-PD), to a lesser degree than before the procedure in 5. Adverse events that transiently occurred during sonication included headache (n = 11), short-lasting vertigo (n = 14) and dizziness (n = 4), nausea (n = 3), burning scalp sensation (n = 3), vomiting (n = 2) and lip paresthesia (n = 2). Adverse events that lasted after the procedure included gait ataxia (n = 5), unsteady feeling (n = 4), taste disturbances (n = 4), asthenia (n = 4), and hand ataxia (n = 3). No adverse event lasted beyond 3 months. Patients underwent on average 21.0 ± 6.9 sonications (range 14–45 sonications) with an average maximal sonication time of 16.0 ± 3.0 seconds (range 13–24 seconds). The mean maximal energy reached was 12,500 ± 4274 J (range 5850–23,040 J) with a mean maximal temperature of 56.5° ± 2.2°C (range 55°–60°C).CONCLUSIONSMRgFUS VIM thalamotomy to relieve medication-resistant tremor was safe and effective in patients with ET, PD, and ET-PD. Current results emphasize the superior adverse events profile of MRgFUS over other surgical approaches for treating tremor with similar efficacy. Large randomized studies are needed to assess prolonged efficacy and safety.

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MR-guided focused ultrasound cerebellothalamic tractotomy for chronic therapy-resistant essential tremor: anatomical target reappraisal and clinical results

Journal of Neurosurgery ◽

10.3171/2019.12.jns192219 ◽

2020 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Marc N. Gallay ◽

David Moser ◽

Daniel Jeanmonod

Keyword(s):

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Hand Function ◽

Red Nucleus ◽

Posterior Part ◽

Clinical Results ◽

Effective Treatment Option ◽

Chronic Therapy ◽

The Mean

OBJECTIVEIn addition to the well-recognized ventral intermediate nucleus (Vim) thalamotomy for the treatment of chronic therapy-resistant essential tremor (ET), an alternative approach targeting the posterior part of the subthalamus was proposed in the 1960s and early 1970s and then was reactualized as cerebellothalamic tractotomy (CTT) with the advent of MR-guided focused ultrasound (MRgFUS) surgery. The goal of this study was to improve target coverage and thus efficacy (i.e., tremor control and its consistency). The authors undertook a histological reappraisal of the CTT target and proposed a targeting strategy of the MRgFUS CTT based on 1) the MR visualization of the center of the red nucleus and 2) the application of preplanned target subunits realized with short sonications under thermal dose control. This study was aimed at demonstrating the efficacy and risk profile of this approach against chronic therapy-resistant ET.METHODSTen consecutive patients suffering from chronic therapy-resistant ET benefited from a unilateral MRgFUS CTT and were followed over the course of 1 year. Primary endpoints were subjective tremor relief, Clinical Rating Scale for Tremor (CRST) score, activities of daily living (ADL) score, and the hand function (HF) scores HF16 and HF32. Histological reappraisal of the target led the authors to propose a standardized targeting protocol for MRgFUS CTT. Thermal doses for 18 and 240 cumulative equivalent minutes at 43°C were calculated and correlated with intraoperative and 2 days postoperative T2-weighted MR images.RESULTSThe mean ± SD for the baseline CRST score was 48 ± 12; the score was 16 ± 7 at 3 months, and 17 ± 8 at 1 year. The mean tremor relief rated by the patients for the operated side was 95% after 2 days, 96% at 3 months, and 93% at 1 year. The mean HF16 was 11.0 ± 2.1 at baseline, 0.7 ± 0.7 at 3 months, and 0.8 ± 0.9 at 1 year (93% mean reduction). The minimum reduction for the HF16 at 1 year was 78%. There was a 51% reduction of the mean ADL score at 1 year. There was no bleeding or infection. Gait difficulties, only detectable on tandem gait, were increased in 3 patients and reduced in 2 patients at 1 year. There was no dysarthria.CONCLUSIONSThe authors’ results suggest that MRgFUS CTT is a very effective treatment option for therapy-resistant ET.

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MRI-guided focused ultrasound thalamotomy in non-ET tremor syndromes

Neurology ◽

10.1212/wnl.0000000000004268 ◽

2017 ◽

Vol 89 (8) ◽

pp. 771-775 ◽

Cited By ~ 34

Author(s):

Alfonso Fasano ◽

Maheleth Llinas ◽

Renato P. Munhoz ◽

Eugen Hlasny ◽

Walter Kucharczyk ◽

...

Keyword(s):

Side Effects ◽

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Invasive Technique ◽

Sustained Improvement ◽

Future Studies ◽

Mri Guided

Objective:To report the 6-month single-blinded results of unilateral thalamotomy with MRI-guided focused ultrasound (MRgFUS) in patients with tremors other than essential tremor.Methods:Three patients with tremor due to Parkinson disease, 2 with dystonic tremor in the context of cervicobrachial dystonia and writer's cramp, and 1 with dystonia gene–associated tremor underwent MRgFUS targeting the ventro-intermedius nucleus (Vim) of the dominant hemisphere. The primary endpoint was the reduction of lateralized items of the Tremor Rating Scale of contralateral hemibody assessed by a blinded rater.Results:All patients achieved a statistically significant, immediate, and sustained improvement of the contralateral tremor score by 42.2%, 52.0%, 55.9%, and 52.9% at 1 week and 1, 3, and 6 months after the procedure, respectively. All patients experienced transient side effects and 2 patients experienced persistent side effects at the time of last evaluation: hemitongue numbness and hemiparesis with hemihypoesthesia.Conclusions:Vim MRgFUS is a promising, incision-free, but nevertheless invasive technique to effectively treat tremors other than essential tremor. Future studies on larger samples and longer follow-up will further define its effectiveness and safety.Clinicaltrials.gov identifier:NCT02252380.Classification of evidence:This study provides Class IV evidence that for patients with tremor not caused by essential tremor, MRgFUS of the Vim improves the tremor of the contralateral hemibody at 6 months.

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Two year data from a preliminary study of double lesion site MRgFUS treatment of Essential Tremor targeting the thalamus and the posterior subthalamic area

10.1101/2020.12.27.20248723 ◽

2021 ◽

Author(s):

Ayesha Jameel ◽

Wladyslaw Gedroyc ◽

Dipankar Nandi ◽

Bryn Jones ◽

Olga Kirmi ◽

...

Keyword(s):

Quality Of Life ◽

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Severity Scores ◽

The Mean ◽

Preliminary Study ◽

Clinical Rating Scale

AbstractBackgroundMR-guided focused ultrasound (MRgFUS) is an effective treatment for essential tremor (ET). However, the optimal intracranial target sites remain to be determined.ObjectiveTo assess MRgFUS induced sequential lesions in (anterior-VIM/VOP nuclei) the thalamus and then posterior subthalamic area (PSA) performed during the same procedure for alleviating ET.Methods14 patients had unilateral MRgFUS lesions placed in anterior-VIM/VOP then PSA. Bain-Findley Spirals were collected during MRgFUS from the treated arm (BFS-TA) and throughout the study from the treated (BFS-TA) and non-treated (BFS-NTA) arms and scored by blinded assessors. Although, the primary outcome was change in the BFS-TA from baseline to 12 months we have highlighted the 24 month data.Secondary outcomes included the Clinical Rating Scale for Tremor (CRST), Quality of Life for ET (QUEST) and PHQ-9 depression scores.ResultsThe mean improvement in the BFS-TA from baseline to 24 months was 41.1% (p<0.001) whilst BFS-NTA worsened by 8.8% (p<0.001). Intra-operative BFS scores from the targeted arm showed a mean 27.9% (p<0.001) decrease after anterior-VIM/VOP ablation and an additional 30.1% (p<0.001) reduction from post anterior-VIM/VOP to post-PSA ablation.Mean improvements at 24 month follow-up in the CRST-parts A, B and C were 60.7%, 30.4% and 65.6% respectively and 37.8% in QUEST-tremor score (all p<0.05). Unilateral tremor severity scores decreased in the treated arm (UETTS-TA) 72.9% (p=0.001) and non-treated arm (UETTS-NTA) 30.5% (p=0.003). At 24 months residual adverse effects were slight unsteadiness (n=1) and mild hemi-chorea (n=1).ConclusionUnilateral anterior-VIM/VOP and PSA MRgFUS significantly diminished contralateral arm tremor with improvements in arm function, tremor related disability and quality of life, with an acceptable adverse event profile.

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Bilateral Magnetic Resonance Imaging-Guided Focused Ultrasound Thalamotomy for Essential Tremor

Stereotactic and Functional Neurosurgery ◽

10.1159/000518662 ◽

2021 ◽

pp. 1-9

Author(s):

Kenji Fukutome ◽

Hidehiro Hirabayashi ◽

Yosuke Osakada ◽

Yoshihiro Kuga ◽

Hideyuki Ohnishi

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Adverse Events ◽

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Resonance Imaging ◽

Clinical Rating ◽

The Mean ◽

Clinical Rating Scale

Introduction: Essential tremor is the most common movement disorder in adults. Bilateral symptoms are typical; however, bilateral thalamotomy for essential tremor is associated with a high probability of adverse events. We retrospectively investigated the efficacy and safety of staged bilateral ventral intermediate nucleus thalamotomy for refractory essential tremor using magnetic resonance imaging-guided focused ultrasound. Methods: We enrolled 5 consecutive patients with refractory essential tremor between September 2016 and March 2020. Patients underwent a second operation at least 1 year after the first operation. The second lesion was created asymmetrically to the first lesion. Results: Mean patient age was 57.6 years, and the mean interval between the 2 operations was 27.8 months. The second lesion center was superior to the first lesion in all patients. The mean baseline, second preoperative, and second postoperative Clinical Rating Scale for Tremor total scores were 63.6, 49.2, and 21.8, respectively. The mean baseline, second preoperative, and second postoperative Clinical Rating Scale for Tremor part C scores were 18.4, 8.2, and 2.6, respectively. One patient had permanent adverse events of slight dysarthria and discomfort in the tongue. No patient experienced dysphagia or cognitive dysfunction after the second operation. Four of the 5 patients were satisfied with the results of the bilateral treatment, including the patient who had permanent adverse events. Conclusions: Magnetic resonance imaging-guided focused ultrasound is an effective method for bilateral thalamotomy when adhering to the following considerations: (1) asymmetrical lesions are created and (2) sufficient interval (>1 year) between operations.

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

Frontiers in Aging Neuroscience ◽

10.3389/fnagi.2021.697029 ◽

2021 ◽

Vol 13 ◽

Author(s):

Peihan Wu ◽

Wei Lin ◽

Kun Hong Li ◽

Hui-Chin Lai ◽

Ming-Tsung Lee ◽

...

Keyword(s):

Essential Tremor ◽

Focused Ultrasound ◽

Rating Scale ◽

Density Ratio ◽

Extended Period ◽

Maximum Energy ◽

Chinese Patients ◽

Average Maximum ◽

The Mean

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.

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Thalamic short pulse stimulation diminishes adverse effects in essential tremor patients

Neurology ◽

10.1212/wnl.0000000000006033 ◽

2018 ◽

Vol 91 (8) ◽

pp. e704-e713 ◽

Cited By ~ 11

Author(s):

Chi-un Choe ◽

Ute Hidding ◽

Miriam Schaper ◽

Alessandro Gulberti ◽

Johannes Köppen ◽

...

Keyword(s):

Side Effects ◽

Adverse Effects ◽

Essential Tremor ◽

Rating Scale ◽

Short Pulse ◽

Current Steering ◽

Tremor Suppression ◽

Monopolar Stimulation ◽

Pulse Stimulation

ObjectiveTo investigate the effect of directional current steering and short pulse stimulation in the ventral intermediate thalamic nucleus (VIM) on stimulation-induced side effects in patients with essential tremor.MethodsWe recruited 8 patients with essential tremor in a stable postoperative condition (>3 months after electrode implantation of deep brain stimulation [DBS] electrodes) with segmented contacts implanted in the VIM. Tremor severity on acute stimulation was assessed by the Fahn-Tolosa-Marin Tremor Rating Scale. Cerebellar impairment was evaluated with the International Cooperative Ataxia Rating Scale. Patients rated paresthesia intensity with a visual analog scale.ResultsIn all patients, tremor was reduced to the same extent by VIM stimulation regardless of pulse width using energy dose–equivalent amplitudes. Short pulse stimulation diminished stimulation-induced ataxia of the upper extremities and paresthesia compared with conventional parameters. Directional steering with monopolar stimulation of single segments successfully suppressed tremor but also induced ataxia. No differences in adverse effects were found between single-segment stimulation conditions.ConclusionThese proof-of-principle findings provide evidence that acute short pulse stimulation is superior to directional steering in the subthalamic area to decrease stimulation-induced side effects while preserving tremor suppression effects in patients with tremor.Classification of evidenceThis study provides Class IV evidence that for patients with tremor with thalamic DBS, acute short pulse stimulation reduces adverse effects, while directional steering does not provide a generalizable benefit regarding adverse effects.

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Stimulation of the subthalamic region for essential tremor

Journal of Neurosurgery ◽

10.3171/jns.2004.101.1.0048 ◽

2004 ◽

Vol 101 (1) ◽

pp. 48-54 ◽

Cited By ~ 92

Author(s):

Puneet Plaha ◽

Nikunj K. Patel ◽

Steven S. Gill

Keyword(s):

Essential Tremor ◽

Upper Limb ◽

Functional Disability ◽

Rating Scale ◽

Related Complication ◽

Content Type ◽

The Mean ◽

Fine Print ◽

Deep Brain

Object. The goal of this study was to determine the safety and efficacy of bilateral subthalamic region stimulation in the treatment of essential tremor (ET). Methods. Following induction of general anesthesia, four patients with disabling tremor that had proved to be refractory to pharmacotherapy underwent magnetic resonance imaging—guided deep brain stimulation (DBS) of the bilateral subthalamic region. Tremor was assessed by applying the Fahn-Tolosa-Marín Tremor Rating Scale at baseline and again at the 12-month follow-up examination. Following surgery the total tremor score improved by 80.1% (from a baseline mean score of 63 ± 15.1 to a score of 11.8 ± 3.9 at 12 months postoperatively). There was a significant improvement (p < 0.0001) in the mean tremor score of the upper limb (postural and action component) from a baseline score of 3 ± 0.9 to a score of 0.5 ± 0.5 at 12 months postoperatively. In two patients with Score 4 head tremor complete arrest of the tremor was observed at 12 months. Motor function scores of the upper limb for drawing spirals, pouring water, and drawing lines improved significantly (p < 0.05) by 66.7, 76.9, and 58.3%, respectively. Handwriting improved by 68%, but this gain was not significant. The mean activities of daily living score at baseline was 20 ± 3.2; there was an 88.8% improvement in this score to 2.3 ± 1.5 at the 12-month evaluation. The voltage required for effective tremor control was low (mean 1.8 ± 0.2 V) and, along with the other parameters of DBS (frequency and pulse width), did not change significantly over the 12-month period. Tolerance to the action component of tremor was not seen. There was no procedural or stimulation-related complication. Conclusions. Bilateral subthalamic region stimulation is effective in arresting tremor and head titubation, as well as functional disability in ET. Complications like dysarthria and disequilibrium were not seen. These patients required low voltages of stimulation and did not develop a tolerance to the treatment.

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