Epidural premotor cortical stimulation in primary focal dystonia: clinical and 18F-fluoro deoxyglucose positron emission tomography open study

[18F]FDG PET in conditions associated with hyperkinetic movement disorders and ataxia: a systematic review

PURPOSE

To give a comprehensive literature overview of alterations in regional cerebral glucose metabolism, measured using [18F]FDG PET, in conditions associated with hyperkinetic movement disorders and ataxia. In addition, correlations between glucose metabolism and clinical variables as well as the effect of treatment on glucose metabolism are discussed.

METHODS

A systematic literature search was performed according to PRISMA guidelines. Studies concerning tremors, tics, dystonia, ataxia, chorea, myoclonus, functional movement disorders, or mixed movement disorders due to autoimmune or metabolic aetiologies were eligible for inclusion. A PubMed search was performed up to November 2021.

RESULTS

Of 1240 studies retrieved in the original search, 104 articles were included. Most articles concerned patients with chorea (n = 27), followed by ataxia (n = 25), dystonia (n = 20), tremor (n = 8), metabolic disease (n = 7), myoclonus (n = 6), tics (n = 6), and autoimmune disorders (n = 5). No papers on functional movement disorders were included. Altered glucose metabolism was detected in various brain regions in all movement disorders, with dystonia-related hypermetabolism of the lentiform nuclei and both hyper- and hypometabolism of the cerebellum; pronounced cerebellar hypometabolism in ataxia; and striatal hypometabolism in chorea (dominated by Huntington disease). Correlations between clinical characteristics and glucose metabolism were often described. [18F]FDG PET-showed normalization of metabolic alterations after treatment in tremors, ataxia, and chorea.

CONCLUSION

In all conditions with hyperkinetic movement disorders, hypo- or hypermetabolism was found in multiple, partly overlapping brain regions, and clinical characteristics often correlated with glucose metabolism. For some movement disorders, [18F]FDG PET metabolic changes reflected the effect of treatment.

Invasive cortical stimulation

The field of neuromodulation, at its essence, aims to apply electrical stimulation to the brain to ameliorate various pathology. Many methods of applying this stimulation exist, including invasive and non-invasive means. In the realm of invasive stimulation, stimulation of the cortex remains one of the earliest techniques investigated, yet one of the most underutilized today. Evidence for the efficacy of direct invasive cortical stimulation continues to mount, especially in recent years. In this chapter we will review the evidence for the use of invasive cortical stimulation as it applies to neuropathic pain, epilepsy, psychiatric disease, movement disorders, tinnitus, and post-stroke recovery, as well explore some potential mechanisms and future directions of the technique.

Sensorimotor Perceptive Rehabilitation Integrated (SPRInt) program: exercises with augmented movement feedback associated to botulinum neurotoxin in idiopathic cervical dystonia-an observational study

BACKGROUND

Idiopathic cervical dystonia (ICD) is a focal dystonia affecting neck muscles. Botulinum neurotoxin (BoNT) is the first-line treatment of ICD and different physical therapies (including exercise) are often proposed as adjunct treatments. However, the actual effectiveness of exercise in ICD is unclear. The aim of the current work is to assess the potential effectiveness of the Sensorimotor Perceptive Rehabilitation Integrated (SPRInt) exercise program as adjunct therapy for ICD.

METHODS

Fifteen ICD patients received BoNT injections in the neck muscles and, 12 weeks later, received BoNT a second time and SPRInt started. SPRInt consists in 18 exercise sessions in which augmented feedback of movement (including visual and acoustic feedback) is extensively used. Dystonia burden was measured by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Patients were evaluated immediately before, 6 and 12 weeks after each BoNT injection.

RESULTS

Six weeks after the first BoNT injection (i.e., at BoNT peak effect), TWSTRS total score was better than baseline and remained improved at 12 weeks. TWSTRS disability domain slightly improved 6 weeks after the first BoNT injection, but after 6 more weeks returned to its baseline level. Disability improved more at SPRInt end (i.e., 6 weeks after the second BoNT injection), being even lower than after toxin alone. With a single-subject analysis, 4/10 patients who did not improve disability after BoNT improved after SPRInt plus BoNT.

CONCLUSIONS

SPRInt plus BoNT can be more effective than BoNT alone in improving cervical dystonia patients' difficulties in the activities of daily living.

TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier NCT03247868 (https://register.clinicaltrials.gov).

Decoding natural scenes based on sounds of objects within scenes using multivariate pattern analysis

Scene recognition plays an important role in spatial navigation and scene classification. It remains unknown whether the occipitotemporal cortex could represent the semantic association between the scenes and sounds of objects within the scenes. In this study, we used the functional magnetic resonance imaging (fMRI) technique and multivariate pattern analysis to assess whether diff ; ;erent scenes could be discriminated based on the patterns evoked by sounds of objects within the scenes. We found that patterns evoked by scenes could be predicted with patterns evoked by sounds of objects within the scenes in the posterior fusiform area (pF), lateral occipital area (LO) and superior temporal sulcus (STS). The further functional connectivity analysis suggested significant correlations between pF, LO and parahippocampal place area (PPA) except that between STS and other three regions under the scene and sound conditions. A distinct network in processing scenes and sounds was discovered using a seed-to-voxel analysis with STS as the seed. This study may provide a cross-modal channel of scene decoding through the sounds of objects within the scenes in the occipitotemporal cortex, which could complement the single-modal channel of scene decoding based on the global scene properties or objects within the scenes.

Prefrontal Cortical Stimulation in Tourette Disorder: Proof-of-concept Clinical and Neuroimaging Study

Background

The benefits of neurosurgery in Tourette Syndrome (TS) are still incompletely understood. Prefrontal cortical electrical stimulation offers a less invasive alternative to deep brain stimulation.

Objective

To perform a pilot assessment on safety and efficacy of prefrontal cortical bilateral electrical stimulation in TS using clinical and brain metabolic assessments.

Methods

Four adult TS patients underwent tic assessment using the Yale Global Tic Severity Scale and the Rush Video Rating Scale at baseline and 1, 3, 6, and 12-months after implant; whereas FDG-PET scans were acquired at baseline and after 6 and 12 months.

Results

Tic clinical scores were improved at 6 months after implant, meanwhile they showed a tendency to re-emerge at the 12-month follow-up. There was a correlation between FDG-PET and tics, mainly consisting in a reduction of baseline brain hypermetabolism, which paralleled tic score reduction.

Conclusion

Epidural stimulation in TS is safe and yields a modulation of tics, paralleled by FDG-PET metabolic modulation.

Isolated Focal Dystonia as a Disorder of Large-Scale Functional Networks

Isolated focal dystonias are a group of disorders with diverse symptomatology but unknown pathophysiology. Although recent neuroimaging studies demonstrated regional changes in brain connectivity, it remains unclear whether focal dystonia may be considered a disorder of abnormal networks. We examined topology as well as the global and local features of large-scale functional brain networks across different forms of isolated focal dystonia, including patients with task-specific (TSD) and nontask-specific (NTSD) dystonias. Compared with healthy participants, all patients showed altered network architecture characterized by abnormal expansion or shrinkage of neural communities, such as breakdown of basal ganglia-cerebellar community, loss of a pivotal region of information transfer (hub) in the premotor cortex, and pronounced connectivity reduction within the sensorimotor and frontoparietal regions. TSD were further characterized by significant connectivity changes in the primary sensorimotor and inferior parietal cortices and abnormal hub formation in insula and superior temporal cortex, whereas NTSD exhibited abnormal strength and number of regional connections. We suggest that isolated focal dystonias likely represent a disorder of large-scale functional networks, where abnormal regional interactions contribute to network-wide functional alterations and may underline the pathophysiology of isolated focal dystonia. Distinct symptomatology in TSD and NTSD may be linked to disorder-specific network aberrations.

Therapeutic Use of Non-invasive Brain Stimulation in Dystonia

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are non-invasive methods for stimulating cortical neurons that have been increasingly used in the neurology realm and in the neurosciences applied to movement disorders. In addition, these tools have the potential to be delivered as clinically therapeutic approach. Despite several studies support this hypothesis, there are several limitations related to the extreme variability of the stimulation protocols, clinical enrolment and variability of rTMS and tDCS after effects that make clinical interpretation very difficult. Aim of the present study will be to critically discuss the state of art therapeutically applications of rTMS and tDCS in dystonia.

Molecular imaging of movement disorders

Positron emission tomography measures the activity of radioactively labeled compounds which distribute and accumulate in central nervous system regions in proportion to their metabolic rate or blood flow. Specific circuits such as the dopaminergic nigrostriatal projection can be studied with ligands that bind to the pre-synaptic dopamine transporter or post-synaptic dopamine receptors (D1 and D2). Single photon emission computerized tomography (SPECT) measures the activity of similar tracers labeled with heavy radioactive species such as technetium and iodine. In essential tremor, there is cerebellar hypermetabolism and abnormal GABAergic function in premotor cortices, dentate nuclei and ventral thalami, without significant abnormalities in dopaminergic transmission. In Huntington’s disease, there is hypometabolism in the striatum, frontal and temporal cortices. Disease progression is accompanied by reduction in striatal D1 and D2 binding that correlate with trinucleotide repeat length, disease duration and severity. In dystonia, there is hypermetabolism in the basal ganglia, supplementary motor areas and cerebellum at rest. Thalamic and cerebellar hypermetabolism is seen during dystonic movements, which can be modulated by globus pallidus deep brain stimulation (DBS). Additionally, GABA-A receptor activity is reduced in motor, premotor and somatosensory cortices. In Tourette’s syndrome, there is hypermetabolism in premotor and sensorimotor cortices, as well as hypometabolism in the striatum, thalamus and limbic regions at rest. During tics, multiple areas related to cognitive, sensory and motor functions become hypermetabolic. Also, there is abnormal serotoninergic transmission in prefrontal cortices and bilateral thalami, as well as hyperactivity in the striatal dopaminergic system which can be modulated with thalamic DBS. In Parkinson’s disease (PD), there is asymmetric progressive decline in striatal dopaminergic tracer accumulation, which follows a caudal-to-rostral direction. Uptake declines prior to symptom presentation and progresses from contralateral to the most symptomatic side to bilateral, correlating with symptom severity. In progressive supranuclear palsy (PSP) and multiple system atrophy (MSA), striatal activity is symmetrically and diffusely decreased. The caudal-to-rostral pattern is lost in PSP, but could be present in MSA. In corticobasal degeneration (CBD), there is asymmetric, diffuse reduction of striatal activity, contralateral to the most symptomatic side. Additionally, there is hypometabolism in contralateral parieto-occipital and frontal cortices in PD; bilateral putamen and cerebellum in MSA; caudate, thalamus, midbrain, mesial frontal and prefrontal cortices in PSP; and contralateral cortices in CBD. Finally, cardiac sympathetic SPECT signal is decreased in PD. The capacity of molecular imaging to provide in vivo time courses of gene expression, protein synthesis, receptor and transporter binding, could facilitate the development and evaluation of novel medical, surgical and genetic therapies in movement disorders.

Sensory abnormalities in focal hand dystonia and non-invasive brain stimulation

It has been proposed that synchronous and convergent afferent input arising from repetitive motor tasks may play an important role in driving the maladaptive cortical plasticity seen in focal hand dystonia (FHD). This hypothesis receives support from several sources. First, it has been reported that in subjects with FHD, paired associative stimulation produces an abnormal increase in corticospinal excitability, which was not confined to stimulated muscles. These findings provide support for the role of excessive plasticity in FHD. Second, the genetic contribution to the dystonias is increasingly recognized indicating that repetitive, stereotyped afferent inputs may lead to late-onset dystonia, such as FHD, more rapidly in genetically susceptible individuals. It can be postulated, according to the two factor hypothesis that dystonia is triggered and maintained by the concurrence of environmental factors such as repetitive training and subtle abnormal mechanisms of plasticity within somatosensory loop. In the present review, we examine the contribution of sensory-motor integration in the pathophysiology of primary dystonia. In addition, we will discuss the role of non-invasive brain stimulation as therapeutic approach in FHD.

Resting-state networks link invasive and noninvasive brain stimulation across diverse psychiatric and neurological diseases

Brain stimulation, a therapy increasingly used for neurological and psychiatric disease, traditionally is divided into invasive approaches, such as deep brain stimulation (DBS), and noninvasive approaches, such as transcranial magnetic stimulation. The relationship between these approaches is unknown, therapeutic mechanisms remain unclear, and the ideal stimulation site for a given technique is often ambiguous, limiting optimization of the stimulation and its application in further disorders. In this article, we identify diseases treated with both types of stimulation, list the stimulation sites thought to be most effective in each disease, and test the hypothesis that these sites are different nodes within the same brain network as defined by resting-state functional-connectivity MRI. Sites where DBS was effective were functionally connected to sites where noninvasive brain stimulation was effective across diseases including depression, Parkinson's disease, obsessive-compulsive disorder, essential tremor, addiction, pain, minimally conscious states, and Alzheimer's disease. A lack of functional connectivity identified sites where stimulation was ineffective, and the sign of the correlation related to whether excitatory or inhibitory noninvasive stimulation was found clinically effective. These results suggest that resting-state functional connectivity may be useful for translating therapy between stimulation modalities, optimizing treatment, and identifying new stimulation targets. More broadly, this work supports a network perspective toward understanding and treating neuropsychiatric disease, highlighting the therapeutic potential of targeted brain network modulation.

PET Neuroimaging: Insights on Dystonia and Tourette Syndrome and Potential Applications

Primary dystonia (pD) is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric developmental disorder characterized by motor and phonic tics, which could progress to behavioral changes. GTS and obsessive-compulsive disorders are often seen in comorbidity, also suggesting that a possible overlap in the pathophysiological bases of these two conditions. PET techniques are of considerable value in detecting functional and molecular abnormalities in vivo, according to the adopted radioligands. For example, PET is the unique technique that allows in vivo investigation of neurotransmitter systems, providing evidence of changes in GTS or pD. For example, presynaptic and post-synaptic dopaminergic studies with PET have shown alterations compatible with dysfunction or loss of D2-receptors bearing neurons, increased synaptic dopamine levels, or both. Measures of cerebral glucose metabolism with (18)F-fluorodeoxyglucose PET ((18)F-FDG PET) are very sensitive in showing brain functional alterations as well. (18)F-FDG PET data have shown metabolic changes within the cortico-striato-pallido-thalamo-cortical and cerebello-thalamo-cortical networks, revealing possible involvement of brain circuits not limited to basal ganglia in pD and GTS. The aim of this work is to overview PET consistent neuroimaging literature on pD and GTS that has provided functional and molecular knowledge of the underlying neural dysfunction. Furthermore, we suggest potential applications of these techniques in monitoring treatments.

Rethinking stimulation of the brain in stroke rehabilitation: why higher motor areas might be better alternatives for patients with greater impairments

Stimulating the brain to drive its adaptive plastic potential is promising to accelerate rehabilitative outcomes in stroke. The ipsilesional primary motor cortex (M1) is invariably facilitated. However, evidence supporting its efficacy is divided, indicating that we may have overgeneralized its potential. Since the M1 and its corticospinal output are frequently damaged in patients with serious lesions and impairments, ipsilesional premotor areas (PMAs) could be useful alternates instead. We base our premise on their higher probability of survival, greater descending projections, and adaptive potential, which is causal for recovery across the seriously impaired. Using a conceptual model, we describe how chronically stimulating PMAs would strongly affect key mechanisms of stroke motor recovery, such as facilitating the plasticity of alternate descending output, restoring interhemispheric balance, and establishing widespread connectivity. Although at this time it is difficult to predict whether PMAs would be "better," it is important to at least investigate whether they are reasonable substitutes for the M1. Even if the stimulation of the M1 may benefit those with maximum recovery potential, while that of PMAs may only help the more disadvantaged, it may still be reasonable to achieve some recovery across the majority rather than stimulate a single locus fated to be inconsistently effective across all.

Emerging concepts in the physiological basis of dystonia

Work over the past 2 decades has led to substantial changes in our understanding of dystonia pathophysiology. Three general abnormalities appear to underlie the pathophysiological substrate. The first is a loss of inhibition. This makes sense considering that it may be responsible for the excess of movement and for the overflow phenomena seen in dystonia. A second abnormality is sensory dysfunction which is related to the mild sensory complaints in patients with focal dystonias and may be responsible for some of the motor dysfunction. Third, evidence from animal models of dystonia as well as from patients with primary dystonia has revealed significant alterations of synaptic plasticity characterized by a disruption of homeostatic plasticity, with a prevailing facilitation of synaptic potentiation, together with the loss of synaptic inhibitory processes. We speculate that during motor learning this abnormal plasticity may lead to an abnormal sensorimotor integration, leading to consolidation of abnormal motor engrams. If so, then removing this abnormal plasticity might have little immediate effect on dystonic movements because bad motor memories have already been ''learned'' and are difficult to erase. These considerations might explain the delayed clinical effects of deep brain stimulation (DBS) in patients with generalized dystonia. Current lines of research will be discussed from a network perspective. © 2013 Movement Disorder Society.

Dystonia rating scales: critique and recommendations

Many rating scales have been applied to the evaluation of dystonia, but only few have been assessed for clinimetric properties. The Movement Disorders Society commissioned this task force to critique existing dystonia rating scales and place them in the clinical and clinimetric context. A systematic literature review was conducted to identify rating scales that have either been validated or used in dystonia. Thirty-six potential scales were identified. Eight were excluded because they did not meet review criteria, leaving 28 scales that were critiqued and rated by the task force. Seven scales were found to meet criteria to be "recommended": the Blepharospasm Disability Index is recommended for rating blepharospasm; the Cervical Dystonia Impact Scale and the Toronto Western Spasmodic Torticollis Rating Scale for rating cervical dystonia; the Craniocervical Dystonia Questionnaire for blepharospasm and cervical dystonia; the Voice Handicap Index (VHI) and the Vocal Performance Questionnaire (VPQ) for laryngeal dystonia; and the Fahn-Marsden Dystonia Rating Scale for rating generalized dystonia. Two "recommended" scales (VHI and VPQ) are generic scales validated on few patients with laryngeal dystonia, whereas the others are disease-specific scales. Twelve scales met criteria for "suggested" and 7 scales met criteria for "listed." All the scales are individually reviewed in the online information. The task force recommends 5 specific dystonia scales and suggests to further validate 2 recommended generic voice-disorder scales in dystonia. Existing scales for oromandibular, arm, and task-specific dystonia should be refined and fully assessed. Scales should be developed for body regions for which no scales are available, such as lower limbs and trunk.

Deep-brain stimulation for dystonia: current indications and future orientations

ABSTRACT: Deep-brain stimulation of the internal globus pallidus is a therapeutic option for dystonia. However, the available data are heterogeneous, ranging from single case reports to a few controlled studies. The outcomes are also largely heterogeneous, depending mostly on the etiology of the dystonia. Except for some well-established good indications, such as primary generalized dystonia and tardive dyskinesia, the efficacy of globus pallidus stimulation remains debated for several forms of dystonia. In addition, many issues are still unsolved, such as the best target of stimulation and the interest of simultaneously combining multiple targets of stimulation or not. Finally the efficacy of new strategies of treatment, such as cortical stimulation, remains to be determined. The aim of this review is to cover these different aspects and give an overview of the current indications and future orientations.

Imaging studies in focal dystonias: a systems level approach to studying a systems level disorder

Focal dystonias are dystonias that affect one part of the body, and are sometimes task-specific. Brain imaging and transcranial magnetic stimulation techniques have been valuable in defining the pathophysiology of dystonias in general, and are particularly amenable to studying focal dystonias. Over the past few years, several common themes have emerged in the imaging literature, and this review summarizes these findings and suggests some ways in which these distinct themes might all point to one common systems-level mechanism for dystonia. These themes include (1) the role of premotor regions in focal dystonia, (2) the role of the sensory system and sensorimotor integration in focal dystonia, (3) the role of decreased inhibition/increased excitation in focal dystonia, and (4) the role of brain imaging in evaluating and guiding treatment of focal dystonias. The data across these themes, together with the features of dystonia itself, are consistent with a hypothesis that all dystonias reflect excessive output of postural control/stabilization systems in the brain, and that the mechanisms for dystonia reflect amplification of an existing functional system, rather than recruitment of the wrong motor programs. Imaging is currently being used to test treatment effectiveness, and to visually guide treatment of dystonia, such as placement of deep brain stimulation electrodes. In the future, it is hoped that imaging may be used to individualize treatments across behavioral, pharmacologic, and surgical domains, thus optimizing both the speed and effectiveness of treatment for any given individual with focal dystonia.

Transcranial magnetic stimulation in dystonia

Transcranial magnetic stimulation (TMS) is a method of noninvasive brain stimulation that directly affects the cerebral cortex but not deep structures. TMS has been used extensively in patients with primary dystonia to test the excitability of connections within and among motor areas of the cortex, and has provided useful information on pathophysiology; however, interindividual variability in the responses has resulted in difficulties in translating this method into a clinically applicable diagnostic use. In addition, TMS studies have disclosed that dystonia is a disorder linked to a disruption of synaptic "scaling," with an excess of synaptic plasticity that is in keeping with findings obtained in animal models of dystonia. This alteration is a unique feature of organic dystonia and may be helpful in differentiating patients with psychogenic dystonia. Finally, TMS can potentially be used as a therapeutic tool to treat some forms of dystonia, such as focal hand dystonia, where pharmacological options or injections of botulinum toxin are often ineffective.

Update on dystonia

PURPOSE OF REVIEW

This review considers the recent literature pertaining to the clinical features, genetics, neuropathology and treatment of dystonia syndromes.

RECENT FINDINGS

The term dystonia indicates at the same time a clinical phenotype and a collection of neurological syndromes mainly of genetic origin. The physical signs contributing to the phenomenology of dystonia have been recently assembled into a coherent set. The molecular genetics of primary dystonia syndromes (DYT1 and DYT6) have been the object of extensive analysis, providing converging views on their causative mechanisms. The relationship between genotype, phenotype, and endophenotypes has been explored for hereditary and sporadic dystonia syndromes. Neurophysiological studies on DYT1 and DYT6 patients, as well as on nonmanifesting carriers, have demonstrated the presence of altered synaptic plasticity. Several recent data indicate a role of dopamine and acetylcholine (ACh) transmission in the pathophysiology of primary dystonia.

SUMMARY

Recent findings have led to novel, testable hypotheses on cellular mechanisms and physiopathological abnormalities underlying dystonia. Neurophysiological studies, imaging data and animal models support the view that corticostriatal, cerebellar, and dopaminergic dysfunctions converge to produce the pathophysiological abnormalities of dystonia.

Epidural direct current stimulation over the left medial prefrontal cortex facilitates spatial working memory performance in rats

BACKGROUND

Extensive evidence supports the notion that modulation of PFC excitability using low-intensity electrical stimulation is a promising modality for treating neuropsychiatric diseases and improving cognitive function.

OBJECTIVE

This study examined the effects of epidural direct current stimulation (eDCS), a method providing smaller shunting of current and more focal stimulation, on spatial working memory.

METHODS

Male Wistar rats that were well trained in an 8-arm radial maze and in which 5-mm round electrodes were implanted over the left medial prefrontal cortex (mPFC) received anodal eDCS (400 μA during 11 min) (n = 9) or sham procedure (n = 9) five minutes before delayed tests in the radial maze.

RESULTS

Animals that received eDCS over the left mPFC had significantly fewer errors in the post-delay performance on the 1-h (P < 0.01), 4-h (P < 0.001), and 10-h (P < 0.001) delayed tests compared with sham-treated animals. General locomotor activity was unaffected because time spent in each visited arm did not change significantly by eDCS. There was no evidence of neuronal lesions in the mPFC underneath the eDCS.

CONCLUSIONS

Our results suggest that epidural direct current stimulation over the mPFC facilitates spatial working memory in rats, an effect that persisted over the long term.

Current and future medical treatment in primary dystonia

Dystonia is a hyperkinetic movement disorder, characterized by involuntary and sustained contractions of opposing muscles causing twisting movements and abnormal postures. It is often a disabling disorder that has a significant impact on physical and psychosocial wellbeing. The medical therapeutic armamentarium used in practice is quite extensive, but for many of these interventions formal proof of efficacy is lacking. Exceptions are the use of botulinum toxin in patients with cervical dystonia, some forms of cranial dystonia (in particular, blepharospasm) and writer's cramp; deep brain stimulation of the pallidum in generalized and segmental dystonia; and high-dose trihexyphenidyl in young patients with segmental and generalized dystonia. In order to move this field forward, we not only need better trials that examine the effect of current treatment interventions, but also a further understanding of the pathophysiology of dystonia as a first step to design and test new therapies that are targeted at the underlying biologic and neurophysiologic mechanisms.