Stereotactic neurosurgery for disabling tremor in multiple sclerosis: thalamotomy or deep brain stimulation?

Clinical neurophysiology in the treatment of movement disorders: IFCN handbook chapter

In this review, different aspects of the use of clinical neurophysiology techniques for the treatment of movement disorders are addressed. First of all, these techniques can be used to guide neuromodulation techniques or to perform therapeutic neuromodulation as such. Neuromodulation includes invasive techniques based on the surgical implantation of electrodes and a pulse generator, such as deep brain stimulation (DBS) or spinal cord stimulation (SCS) on the one hand, and non-invasive techniques aimed at modulating or even lesioning neural structures by transcranial application. Movement disorders are one of the main areas of indication for the various neuromodulation techniques. This review focuses on the following techniques: DBS, repetitive transcranial magnetic stimulation (rTMS), low-intensity transcranial electrical stimulation, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), and focused ultrasound (FUS), including high-intensity magnetic resonance-guided FUS (MRgFUS), and pulsed mode low-intensity transcranial FUS stimulation (TUS). The main clinical conditions in which neuromodulation has proven its efficacy are Parkinson's disease, dystonia, and essential tremor, mainly using DBS or MRgFUS. There is also some evidence for Tourette syndrome (DBS), Huntington's disease (DBS), cerebellar ataxia (tDCS), and axial signs (SCS) and depression (rTMS) in PD. The development of non-invasive transcranial neuromodulation techniques is limited by the short-term clinical impact of these techniques, especially rTMS, in the context of very chronic diseases. However, at-home use (tDCS) or current advances in the design of closed-loop stimulation (tACS) may open new perspectives for the application of these techniques in patients, favored by their easier use and lower rate of adverse effects compared to invasive or lesioning methods. Finally, this review summarizes the evidence for keeping the use of electromyography to optimize the identification of muscles to be treated with botulinum toxin injection, which is indicated and widely performed for the treatment of various movement disorders.

Brain stimulation for patients with multiple sclerosis: an umbrella review of therapeutic efficacy

Multiple sclerosis patients often experience various symptoms that can greatly impact their quality of life. There are various brain stimulation techniques that have been evaluated for their ability to reduce the symptoms of multiple sclerosis. However, there is inconsistency in the specific stimulation methods used and the symptoms targeted in the existing research. This umbrella review conducted in order to evaluate the effectiveness of brain stimulation and identify limitations and gaps for further research. In this umbrella review, we conducted a searched on Web of Knowledge, PubMed, and Scopus database. We specifically looked for reviews, with or without meta-analyses, that have investigated the effects of brain stimulation methods on symptoms of multiple sclerosis. All articles were examined by AMSTAR 2 (A Measure Tool to Assess Systematic Review 2). We identified 155 articles, of which 14 were eligible for inclusion. Of those, five were qualitative studies and nine were meta-analyses. Among the included studies, four examined the use of deep brain stimulation, while ten investigated the therapeutic potential of noninvasive brain stimulation. Considering the heterogeneity of studies, the current evidence suggests that repetitive transcranial magnetic stimulation may be effective in treating pain and improving motor function, while transcranial direct current stimulation may be useful in alleviating fatigue and enhancing certain aspects of cognitive performance. Deep brain stimulation, on the other hand, appears to be effective in reducing tremors. However, further research is warranted to validate these findings and address the existing limitations in the field.

Patient selection and outcome of deep brain stimulation for multiple sclerosis-associated tremor

INTRODUCTION

Tremor is a disabling symptom of multiple sclerosis (MS), with limited treatment modalities. Thalamic ventral-intermediate-nucleus (VIM) deep brain stimulation (DBS) is a method of neuromodulation. We describe the long-term outcomes of our carefully selected patients who underwent VIM DBS for their MS-associated tremor.

METHODS

Patients were referred from the regional neurology units. Pre-operative assessments included suitability for anesthesia, tremor quantification by the Fahn-Tolosa-Marin scores, and quality-of-life (EQ5D) measures. Exclusion criteria included prominent cerebellar symptoms such as ataxia and dysmetria, intracranial pathology such as ventriculomegaly, cerebellar plaques and thalamic abnormality, and comorbid psychiatric symptoms. Seven patients (3M:4F) underwent DBS for MS-associated tremor between September 2013 and February 2019. Mean age was 42 years (±SD 8 years). DBS was performed at a mean of 13 years (±SD 9 years) after diagnosis of MS.

RESULTS

There were no postoperative surgical complications. All patients showed improvement in FTM tremor scores, by up to 61% at 6 months postoperatively. There was an improvement of 30-175% in quality-of-life scores at 6 months. Improvement of tremor and quality of life, over baseline, was sustained over a long period of follow-up (mean 26.6 months ± SD 20.7 months), including our longest duration at 72 months.

CONCLUSION

With careful selection, DBS is a safe, efficacious intervention for MS-tremor and can positively impact on tremor and quality of life, with effects over a long period. As patients live longer with MS and the advent of new therapies, DBS should be considered for selected patients.

Movement Disorders in Multiple Sclerosis: An Update

Background:

Multiple sclerosis (MS), a subset of chronic primary inflammatory demyelinating disorders of the central nervous system, is closely associated with various movement disorders. These disorders may be due to MS pathophysiology or be coincidental. This review describes the full spectrum of movement disorders in MS with their possible mechanistic pathways and therapeutic modalities.

Methods:

The authors conducted a narrative literature review by searching for ‘multiple sclerosis’ and the specific movement disorder on PubMed until October 2021. Relevant articles were screened, selected, and included in the review according to groups of movement disorders.

Results:

The most prevalent movement disorders described in MS include restless leg syndrome, tremor, ataxia, parkinsonism, paroxysmal dyskinesias, chorea and ballism, facial myokymia, including hemifacial spasm and spastic paretic hemifacial contracture, tics, and tourettism. The anatomical basis of some of these disorders is poorly understood; however, the link between them and MS is supported by clinical and neuroimaging evidence. Treatment options are disorder-specific and often multidisciplinary, including pharmacological, surgical, and physical therapies.

Discussion:

Movements disorders in MS involve multiple pathophysiological processes and anatomical pathways. Since these disorders can be the presenting symptoms, they may aid in early diagnosis and managing the patient, including monitoring disease progression. Treatment of these disorders is a challenge. Further work needs to be done to understand the prevalence and the pathophysiological mechanisms responsible for movement disorders in MS.

A detailed analysis of anatomical plausibility of crossed and uncrossed streamline rendition of the dentato-rubro-thalamic tract (DRT(T)) in a commercial stereotactic planning system

Background

An increasing number of neurosurgeons use display of the dentato-rubro-thalamic tract (DRT) based on diffusion weighted imaging (dMRI) as basis for their routine planning of stimulation or lesioning approaches in stereotactic tremor surgery. An evaluation of the anatomical validity of the display of the DRT with respect to modern stereotactic planning systems and across different tracking environments has not been performed.

Methods

Distinct dMRI and anatomical magnetic resonance imaging (MRI) data of high and low quality from 9 subjects were used. Six subjects had repeated MRI scans and therefore entered the analysis twice. Standardized DICOM structure templates for volume of interest definition were applied in native space for all investigations. For tracking BrainLab Elements (BrainLab, Munich, Germany), two tensor deterministic tracking (FT2), MRtrix IFOD2 (https://www.mrtrix.org), and a global tracking (GT) approach were used to compare the display of the uncrossed (DRTu) and crossed (DRTx) fiber structure after transformation into MNI space. The resulting streamlines were investigated for congruence, reproducibility, anatomical validity, and penetration of anatomical way point structures.

Results

In general, the DRTu can be depicted with good quality (as judged by waypoints). FT2 (surgical) and GT (neuroscientific) show high congruence. While GT shows partly reproducible results for DRTx, the crossed pathway cannot be reliably reconstructed with the other (iFOD2 and FT2) algorithms.

Conclusion

Since a direct anatomical comparison is difficult in the individual subjects, we chose a comparison with two research tracking environments as the best possible “ground truth.” FT2 is useful especially because of its manual editing possibilities of cutting erroneous fibers on the single subject level. An uncertainty of 2 mm as mean displacement of DRTu is expectable and should be respected when using this approach for surgical planning. Tractographic renditions of the DRTx on the single subject level seem to be still illusive.

Functional neuroplasticity in response to cerebello-thalamic injury underpins the clinical presentation of tremor in multiple sclerosis

BACKGROUND

Tremor is present in almost half of multiple sclerosis (MS) patients. The lack of understanding of its pathophysiology is hampering progress in development of treatments.

OBJECTIVES

To clarify the structural and functional brain changes associated with the clinical phenotype of upper limb tremor in people with MS.

METHODS

Fifteen healthy controls (46.1 ± 15.4 years), 27 MS participants without tremor (46.7 ± 11.6 years) and 42 with tremor (46.6 ± 11.5 years) were included. Tremor was quantified using the Bain score (0-10) for overall severity, handwriting and Archimedes spiral drawing. Functional magnetic resonance imaging activations were compared between participants groups during performance of a joystick task designed to isolate tremulous movement. Inflammation and atrophy of cerebello-thalamo-cortical brain structures were quantified.

RESULTS

Tremor participants were found to have atrophy of the cerebellum and thalamus, and higher ipsilateral cerebellar lesion load compared to participants without tremor (p < 0.020). We found higher ipsilateral activation in the inferior parietal lobule, the premotor cortex and supplementary motor area in MS tremor participants compared to MS participants without tremor during the joystick task. Finally, stronger activation in those areas was associated with lower tremor severity.

CONCLUSION

Subcortical neurodegeneration and inflammation along the cerebello-thalamo-cortical and cortical functional neuroplasticity contribute to the severity of tremor in MS.

Tremor in multiple sclerosis is associated with cerebello-thalamic pathology

Tremor in people with multiple sclerosis (MS) is a frequent and debilitating symptom with a relatively poorly understood pathophysiology. To determine the relationship between clinical tremor severity and structural magnetic resonance imaging parameters. Eleven patients with clinically definite MS and right-sided upper limb tremor were studied. Tremor severity was assessed using the Bain score (overall severity, writing, and Archimedes spiral drawing). Cerebellar dysfunction was assessed using the Scale for the Assessment and Rating of Ataxia. Dystonia was assessed using the Global Dystonia Scale adapted for upper limb. For all subjects, volume was calculated for the thalamus from T1-weighted volumetric scans using Freesurfer. Superior cerebellar peduncle (SCP) cross-sectional areas were measured manually. The presence of lesions was visually determined and the lesion volumes were calculated by the lesion growth algorithm as implemented in the Lesion Segmentation Toolbox. Right thalamic volume negatively correlated with Bain tremor severity score (ρ = - 0.65, p = 0.03). Left thalamic volume negatively correlated with general Bain tremor severity score (ρ = - 0.65, p = 0.03) and the Bain writing score (ρ = - 0.65, p = 0.03). Right SCP area negatively correlated with Bain writing score (ρ = - 0.69, p = 0.02). Finally, Bain Archimedes score was significantly higher in patients with lesions in the contralateral thalamus. Whole brain lesion load showed no relationship with tremor severity. These results implicate degeneration of key structures within the cerebello-thalamic pathway as pathological substrates for tremor in MS patients.

Stereotactic radiosurgery for medically refractory multiple sclerosis-related tremor

OBJECTIVE Multiple sclerosis (MS) is a neurodegenerative disease that can lead to severe intention tremor in some patients. In several case reports, conventional radiotherapy has been reported to possibly exacerbate MS. Radiosurgery dramatically limits normal tissue irradiation to potentially avoid such a problem. Gamma Knife thalamotomy (GKT) has been established as a minimally invasive technique that is effective in treating essential tremor and Parkinson's disease-related tremor. The goal in this study was to analyze the outcomes of GKT in patients suffering from medically refractory MS-related tremor. METHODS The authors retrospectively studied the outcomes of 15 patients (mean age 46.5 years) who had undergone GKT over a 15-year period (1998-2012). Fourteen patients underwent GKT at a median maximum dose of 140 Gy (range 130-150 Gy) using a single 4-mm isocenter. One patient underwent GKT at a dose of 140 Gy delivered via two 4-mm isocenters (3 mm apart). The posteroinferior region of the nucleus ventralis intermedius (VIM) was the target for all GKTs. The Fahn-Tolosa-Marin clinical tremor rating scale was used to evaluate tremor, handwriting, drawing, and drinking. The median time to the last follow-up was 39 months. RESULTS After GKT, 13 patients experienced tremor improvement on the side contralateral to surgery. Four patients noted tremor arrest at a median of 4.5 months post-GKT. Seven patients had excellent tremor improvement and 6 had good tremor improvement. Four patients noted excellent functional improvement, 8 noted good functional improvement, and 1 noted satisfactory functional improvement. Three patients experienced diminished tremor relief at a median of 18 months after radiosurgery. Two patients experienced temporary adverse radiation effects. Another patient developed a large thalamic cyst 60 months after GKT, which was successfully managed with Ommaya reservoir placement. CONCLUSIONS Gamma Knife thalamotomy was found to be a minimally invasive and beneficial procedure for medically refractory MS tremor.

Cerebellar Dysfunction in Multiple Sclerosis

Multiple sclerosis (MS) commonly affects the cerebellum causing acute and chronic symptoms. Cerebellar signs contribute significantly to clinical disability, and symptoms such as tremor, ataxia, and dysarthria are particularly difficult to treat. Increasing knowledge concerning the pathophysiology of cerebellar disease in MS from human postmortem studies, experimental models, and clinical trials has raised the hope that cerebellar symptoms will be better treated in the future.

The occurrence of dystonia in upper-limb multiple sclerosis tremor

BACKGROUND

The pathophysiology of multiple sclerosis (MS) tremor is uncertain with limited phenotypical studies available.

OBJECTIVE

To investigate whether dystonia contributes to MS tremor and its severity.

METHODS

MS patients (n = 54) with and without disabling uni- or bilateral upper limb tremor were recruited (39 limbs per group). We rated tremor severity, writing and Archimedes spiral drawing; cerebellar dysfunction (SARA score); the Global Dystonia Scale (GDS) for proximal and distal upper limbs, dystonic posturing, mirror movements, geste antagoniste, and writer's cramp.

RESULTS

Geste antagoniste, mirror dystonia, and dystonic posturing were more frequent and severe (p < 0.001) and dystonia scores were correlated with tremor severity in tremor compared to non-tremor patients. A 1-unit increase in distal dystonia predicted a 0.52-Bain unit (95% confidence interval (CI) 0.08-0.97), p = 0.022) increase in tremor severity and a 1-unit (95% CI 0.48-1.6, p = 0.001) increase in drawing scores. A 1-unit increase in proximal dystonia predicted 0.93-Bain unit increase (95% CI 0.45-1.41, p < 0.001) in tremor severity and 1.5-units (95% CI 0.62-2.41, p = 0.002) increase in the drawing score. Cerebellar function in the tremor limb and tremor severity was correlated (p < 0.001).

CONCLUSIONS

Upper limb dystonia is common in MS tremor suggesting that MS tremor pathophysiology involves cerebello-pallido-thalamo-cortical network dysfunction.

Deep brain stimulation and multiple sclerosis: Therapeutic applications

Deep brain stimulation is a neurosurgical technique that can be used to alleviate symptoms in a growing number of neurological conditions through modulating activity within brain networks. Certain applications of deep brain stimulation are relevant for the management of symptoms in multiple sclerosis. In this paper we discuss existing treatment options for tremor, facial pain and urinary dysfunction in multiple sclerosis and discuss evidence to support the potential use of deep brain stimulation for these symptoms.

Targeting thalamic tremor cells in deep brain stimulation for multiple sclerosis-induced complex tremor

BACKGROUND

Tremor is an important cause of disability in patients with multiple sclerosis (MS). It is an ongoing debate as to which brain region should be targeted in MS patients with complex tremors.

CASE DESCRIPTION

Here, we describe our experience with targeting thalamic tremor cells in the ventro-intermediate/ventro-oralis posterior (Vim/Vop) region in a patient with MS related complex tremor. Intraoperative multiple-microelectrode recordings showed the existence of tremor cells. Test stimulation produced the best effect when performed at the regions where tremor cells were recorded. Postoperative examination revealed a substantial improvement of the tremor.

CONCLUSION

Our case observation reveals the existence of a neurophysiological target for deep brain stimulation (DBS) in MS related tremor.

Understanding tremor in multiple sclerosis: prevalence, pathological anatomy, and pharmacological and surgical approaches to treatment

Background

Given that tremor is one of the most prevalent and disabling features of multiple sclerosis (MS), we will review the most significant milestones in tremor in this disease in recent years, focusing on prevalence, clinical features, anatomical basis, and treatment.

Methods

Data for this review were identified by searching MEDLINE with the search terms “multiple sclerosis” and “tremor”. References were also identified from relevant articles published between January 1966 and May 2012.

Results

The predominant type of MS tremor is a large-amplitude, postural, and kinetic tremor, which most commonly affects the arms, although tremor can also involve head, neck, vocal cords, and trunk. Involvement of the tongue, jaw, or palate has not been reported. Although the anatomical basis underlying tremor in MS is poorly understood, the link between the cerebellum and the MS-related tremor is supported by clinical and experimental studies. Currently available medication is often unsuccessful in most cases. Surgical treatment can be a satisfactory alternative to treat severe and disabling tremor.

Discussion

Tremor in MS patients could be considered as an advanced consequence of the disease and its presence suggests a more aggressive course. MS tremor can be severe and very disabling for a small group of patients. Treatment of MS tremor remains a great challenge. Recent studies suggest that dissociating tremor from cerebellar dysfunction using selected clinical tests would be the key issue to successful surgical treatment. Understanding the pathophysiology and biochemistry of tremor production in MS may lead to new therapeutic approaches.

Moving forward: advances in the treatment of movement disorders with deep brain stimulation

The modern era of stereotactic and functional neurosurgery has ushered in state of the art technologies for the treatment of movement disorders, particularly Parkinson's disease (PD), tremor, and dystonia. After years of experience with various surgical therapies, the eventual shortcomings of both medical and surgical treatments, and several serendipitous discoveries, deep brain stimulation (DBS) has risen to the forefront as a highly effective, safe, and reversible treatment for these conditions. Idiopathic advanced PD can be treated with thalamic, globus pallidus internus (GPi), or subthalamic nucleus (STN) DBS. Thalamic DBS primarily relieves tremor while GPi and STN DBS alleviate a wide range of Parkinsonian symptoms. Thalamic DBS is also used in the treatment of other types of tremor, particularly essential tremor, with excellent results. Both primary and various types of secondary dystonia can be treated very effectively with GPi DBS. The variety of anatomical targets for these movement disorders is indicative of the network-level dysfunction mediating these movement disturbances. Despite an increasing understanding of the clinical benefits of DBS, little is known about how DBS can create such wide sweeping neuromodulatory effects. The key to improving this therapeutic modality and discovering new ways to treat these and other neurologic conditions lies in better understanding the intricacies of DBS. Here we review the history and pertinent clinical data for DBS treatment of PD, tremor, and dystonia. While multiple regions of the brain have been targeted for DBS in the treatment of these movement disorders, this review article focuses on those that are most commonly used in current clinical practice. Our search criteria for PubMed included combinations of the following terms: DBS, neuromodulation, movement disorders, PD, tremor, dystonia, and history. Dates were not restricted.

Symptomatic therapy in multiple sclerosis: a review for a multimodal approach in clinical practice

As more investigations into factors affecting the quality of life of patients with multiple sclerosis (MS) are undertaken, it is becoming increasingly apparent that certain comorbidities and associated symptoms commonly found in these patients differ in incidence, pathophysiology and other factors compared with the general population. Many of these MS-related symptoms are frequently ignored in assessments of disease status and are often not considered to be associated with the disease. Research into how such comorbidities and symptoms can be diagnosed and treated within the MS population is lacking. This information gap adds further complexity to disease management and represents an unmet need in MS, particularly as early recognition and treatment of these conditions can improve patient outcomes. In this manuscript, we sought to review the literature on the comorbidities and symptoms of MS and to summarize the evidence for treatments that have been or may be used to alleviate them.

[Clinical characteristics and treatment of dystonia]

Dystonia is defined as a syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements, or abnormal postures. Its diagnosis is based on clinical characteristics. In dystonia, the pattern of abnormal posture or movement tends to be constant during the short term even if its severity fluctuates. This stereotypy often helps differentiate dystonia from psychogenic reaction. Dystonia may appear only during some specific task (task specificity) especially in its early phase, although it often becomes obscure during the long clinical course, resulting in persistent dystonic posture. Sensory trick or geste antagoniste means the change of severity triggered by some sensory input Overflow phenomenon is the activation of muscles unnecessary to a task, hampering purposeful movement. Symptoms tend to be milder in the morning, with large individual variation of its duration (morning benefit). Symptoms of dystonia may abruptly appear or disappear (flip-flop phenomenon). Cocontraction, believed as an essential feature of dystonia, reflects a loss of reciprocal inhibition of muscle activities, causing involuntary simultaneous contractions of agonists and antagonists. "Negative dystonia," still an unaccepted feature of dystonia, is defined as non-paretic loss of central driving of muscle activities necessary to a task. Apraxia of lid opening/closure, paretic form of hand dystonia, dropped head syndrome, camptocormia, Pisa syndrome, cervical dystonia with limited range of head movement, or mandibular dystonia without cocontractions of masticatory muscles, can be explained with this concept at least in a subset of cases. Treatment of dystonia includes medication, botulinum toxin injection, intrathecal baclofen, surgical intervention, acupuncture and other alternative therapies, rehabilitation, and psychotherapy. Oral medication is usually an adjunct to more potent therapeutic options except for some specific indications like dopa-responsive dystonia. Botulinum toxin is usually the treatment of choice for focal dystonia. Deep brain stimulation can be considered for both focal and non-focal phenotypes of dystonia.

Movement disorders in patients with multiple sclerosis

Apart from tremor and restless-legs syndrome, abnormal involuntary movements are uncommon in patients with multiple sclerosis. A review of the literature in multiple sclerosis reveals case reports of a variety of other movement disorders such as myoclonus, spasmodic torticollis, paroxysmal dystonia, chorea, ballism, and parkinsonism. This chapter presents a thorough review of these movement disorders in multiple sclerosis patients and provides readers with potential underlying pathogenetic mechanisms.

Deep Brain Stimulation of the Ventral Intermediate Nucleus of the Thalamus for Tremor in Patients With Multiple Sclerosis

BACKGROUND

Tremor is an important cause of disability in patients with multiple sclerosis (MS). Deep brain stimulation (DBS) in the ventral intermediate nucleus (VIM) of the thalamus is said to be beneficial for MS tremor.

OBJECTIVE

To assess the long-term efficacy of VIM DBS for MS disabling tumor.

METHODS

We treated 10 patients (4 men and 6 women) with advanced MS-related medication-resistant tremor with DBS at the VIM thalamic nucleus. DBS was unilateral in 9 patients and bilateral in 1 patient in 2 stages. Contralateral arm tremor was assessed with the Fahn-Tolosa-Marin tremor rating scale.

RESULTS

At 1 year, 5 of 10 patients (5 of 11 hemispheres) had a reduction in tremor scores with stimulation compared with baseline; in 3 patients, the reduction was &gt; 50%. After 36 months, 3 patients continued benefiting from stimulation, 2 having &gt; 50% improvement. Of the 6 symptomatic sides that did not benefit at 1 year, 3 failed to have even initial benefit, and 3 had a transient improvement lasting &lt; 1 year. One patient stopped using stimulation because of a lack of improvement at 5 months after surgery and was lost to follow-up.

CONCLUSION

Approximately one-half of the patients derived some benefit from VIM DBS 1 year after surgery, but this benefit reached a &gt; 50% reduction in only 30% of the patients. This level of improvement may be related to the variability of the demyelinating lesions and the superimposition of ataxia in the MS patients. Developing better treatments for MS tremor continues to be a challenge.

The effect of levetiracetam on tremor severity and functionality in patients with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) intention tremor is a disabling symptom, which is difficult to treat.

OBJECTIVES

To investigate the effects of levetiracetam, an antiepileptic drug, on tremor severity and related functionality in MS.

METHODS

A randomized, double-blind, placebo-controlled, cross-over study examined the effects of 6 weeks of oral levetiracetam administration (starting dose=250 mg/day, maximal dose=2000 mg/day) in 18 MS patients with disabling intention tremor. Primary outcome was Fahn's Tremor Rating Scale (FTRS) A&B. Secondary outcome measures were the nine-hole peg test, patient's opinion rated with the visual analog scale, FTRS C, and an activities of daily life questionnaire and validated tremor indexes derived during the performance of a digitized spiral drawing task and a wrist step-tracking task. Repeated measures analysis of variance and Friedman tests were applied.

RESULTS

In all, 14 patients completed the trial. Maximal dose intake ranged from 1000 to most commonly 2000 mg, depending on patients' tolerance level. No significant effects of levetiracetam were found for any outcome measure. Further analyses on subgroups with different tremor severity showed no differential effects. Eight patients reported adverse events such as fatigue and stomach ache.

CONCLUSIONS

Levetiracetam intake of 2000 mg/day did not affect tremor severity or functionality in patients with MS.

Deep brain stimulation and tremor

Deep brain stimulation (DBS) has been used to treat various tremor disorders for several decades. Medication-resistant, disabling essential tremor (ET) is the most common tremor disorder treated with DBS. The treatment has been consistently reported to result in significant benefit in upper extremity, as well as head and voice tremor, all of which were improved more dramatically with bilateral procedures. These benefits have been demonstrated to be sustained for up to 7 years. DBS has also been shown to be beneficial for the tremor associated with multiple sclerosis and post-traumatic tremor; however, fewer cases have been reported and the benefit is less consistent, less dramatic, and more transient than that seen with ET. The ventral intermediate nucleus of the thalamus is the most common DBS target for tremor disorders, but more recent studies have demonstrated benefits in tremor from DBS of the subthalamic area, primarily the zona incerta. Surgical complications are relatively uncommon and are generally less frequent than those seen with thalamotomy. Stimulation-related effects are usually mild and resolve with adjustment of stimulation parameters. DBS is thus a relatively safe and effective treatment for tremor disorders, particularly for medication-resistant, disabling ET, but may also have some role in medication-resistant, disabling tremor associated with multiple sclerosis and traumatic head injury.