Non-invasive brain stimulation for dystonia: therapeutic implications

A Randomized Controlled Trial of the Effect of Repetitive Transcranial Magnetic Stimulation of the Motor Cortex on Lower Extremity Spasticity in Hereditary Spastic Paraplegia

INTRODUCTION

Hereditary spastic paraplegia refers to a group of conditions characterized by a slow progression of spasticity in lower limbs resulting in gait abnormalities. Current treatment options have proven to be insufficient in terms of symptom alleviation. In this study, we tested the effectiveness of repetitive transcranial magnetic stimulation (rTMS) on lower limb spasticity in patients with hereditary spastic paraplegia.

METHODS

Eight patients were randomly assigned to receive either five sessions of active 5 Hz-rTMS ( n = 4) or sham rTMS ( n = 4). The primary outcome was a change in spasticity assessed by the modified Ashworth scale. Secondary outcomes were change in 10 m walking test, Fugl-Meyer assessment of lower extremity motor function, and quality-of-life short-form survey scores. Assessment of the outcomes was done before, upon completion, and 1 month after the intervention. We analyzed the data using repeated-measure analysis of variance.

RESULTS

Mean age of the participants was 38.5 (SD = 5.4) years, and 50% were women. Compared with sham rTMS, real rTMS was effective in decreasing modified Ashworth scale (rTMS × time: F [df = 2] = 7.44; P = 0.008). Real rTMS group had lower modified Ashworth scale scores at the end of rTMS sessions (estimate = -0.938; SE = 0.295; P = 0.019) and at the end of follow-up (estimate = -0.688; SE = 0.277; P = 0.048) compared with the sham rTMS group. Real and sham rTMS groups were not different in the secondary outcomes.

CONCLUSIONS

Repetitive transcranial magnetic stimulation is an effective method in reducing lower limb spasticity of patients with hereditary spastic paraplegia.

Neuromodulation in Dystonia - Harnessing the Network

Adult-onset isolated focal dystonia (AOIFD) is a network disorder characterised by abnormalities of sensory processing and motor control. These network abnormalities give rise to both the phenomenology of dystonia and the epiphenomena of altered plasticity and loss of intracortical inhibition. Existing modalities of deep brain stimulation effectively modulate parts of this network but are limited both in terms of targets and invasiveness. Novel approaches using a variety of non-invasive neuromodulation techniques including transcranial stimulation and peripheral stimulation present an interesting alternative approach and may, in conjunction with rehabilitative strategies, have a role in tailored therapies targeting the underlying network abnormality behind AOIFD.

Transcranial Magnetic Stimulation in the Treatment of Neurological Diseases

Transcranial Magnetic Stimulation (TMS) has widespread use in research and clinical application. For psychiatric applications, such as depression or OCD, repetitive TMS protocols (rTMS) are an established and globally applied treatment option. While promising, rTMS is not yet as common in treating neurological diseases, except for neurorehabilitation after (motor) stroke and neuropathic pain treatment. This may soon change. New clinical studies testing the potential of rTMS in various other neurological conditions appear at a rapid pace. This can prove challenging for both practitioners and clinical researchers. Although most of these neurological applications have not yet received the same level of scientific/empirical scrutiny as motor stroke and neuropathic pain, the results are encouraging, opening new doors for TMS in neurology. We here review the latest clinical evidence for rTMS in pioneering neurological applications including movement disorders, Alzheimer's disease/mild cognitive impairment, epilepsy, multiple sclerosis, and disorders of consciousness.

Transcranial Magnetic Stimulation for the Neurological Patient: Scientific Principles and Applications

Non-invasive brain stimulation has been increasingly recognized for its potential as an investigational, diagnostic and therapeutic tool across the clinical neurosciences. Transcranial magnetic stimulation (TMS) is a non-invasive method of focal neuromodulation. Diagnostically, TMS can be used to probe cortical excitability and plasticity, as well as for functional mapping. Therapeutically, depending on the pattern employed, TMS can either facilitate or inhibit stimulated cortex potentially modulating maladaptive physiology through its effects on neuroplasticity. Despite this potential, applications of TMS in neurology have only been approved for diagnostic clinical neurophysiology, pre-surgical mapping of motor and language cortex, and the treatment of migraines. In this article, we discuss the principles of TMS and its clinical applications in neurology, including experimental applications in stroke rehabilitation, seizures, autism spectrum disorder, neurodegenerative disorders, movement disorders, tinnitus, chronic pain and functional neurological disorder. To promote increased cross-talk across neurology and psychiatry, we also succinctly review the TMS literature for the treatment of major depression and obsessive compulsive disorder. Overall, we argue that larger clinical trials that are better informed by circuit-level biomarkers and pathophysiological models will lead to an expansion of the application of TMS for patients cared for by neurologists.

Impact of operator experience on transcranial magnetic stimulation

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Response variability to transcranial magnetic stimulation (TMS) is a crucial issue.

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An operator’s experience in TMS may affect the result of resting motor threshold measurement.

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A beginner may have higher consistency in 1 mV motor evoked potential with practice.

Objective

To determine the impact of an operator’s experience on transcranial magnetic stimulation (TMS) measurement.

Methods

Operator B (beginner), operator E (expert), and 30 healthy participants joined the study consisting of two experiments. In each experiment, each operator performed a TMS protocol on each participant in a random order.

Results

Compared with operator E, operator B exhibited higher resting motor threshold (RMT) in experiment I (60.1 ± 13.0 vs. 57.4 ± 10.9% maximal stimulation output, p = 0.017) and the difference disappeared in experiment II (p = 0.816). In 1-mV motor evoked potential (MEP) measurement, operator B exhibited higher standard deviation indicating lower consistency in experiment I compared with experiment II (1.05 ± 0.40 vs. 1.05 ± 0.16 mV with unequal variances, p = 0.001) and had poor intrarater reliability between the experiments (intraclass correlation coefficient = −0.130). There was no difference in the results of active motor threshold, silent period, paired-pulse stimulation, or continuous theta burst stimulation between the operators.

Conclusions

An operator’s experience in TMS may affect the results of RMT measurement. With practice, a beginner may choose a more precise stimulation location and have higher consistency in 1-mV MEP measurement.

Significance

We recommend that a beginner needs to practice for precise stimulation locations before conducting a trial or clinical practice.

[Issues of diagnostic and therapeutic use of transcranial magnetic stimulation in patients with writing cramp]

OBJECTIVE

To study diagnostic and therapeutic values of transcranial magnetic stimulation (TMS) in writing cramp (WC).

MATERIAL AND METHODS

Twelve right-handed patients with WC were enrolled in the study. All patients underwent low-frequency repetitive TMS (rTMS) of the premotor cortex of contralateral to affected hand hemisphere. The clinical efficacy was assessed using the Writer's Cramp Rating Scale (WCRS) and the Medical Outcomes Study-Short Form (MOS-SF-36). Before and after last rTMS session, motor mapping of Abductor pollicis brevis muscle (APB) was performed using navigated TMS (nTMS). Localization, area, and amplitude-weighted area of the APB muscle cortical representations were compared with the healthy controls. After the rTMS course, the dynamics of the studied parameters was assessed.

RESULTS

Ten sessions of low-frequency rTMS of premotor cortex reduced the severity of WS clinical symptoms with a duration of effect of at least 1 month (p<0.05). There was no statistically significant difference between the area and the weighted area of cortical muscle representations between patients and healthy controls or in patients before and after rTMS. When assessing the localization of cortical muscle representations, two trends were noted: in 4 patients, the localization remained stable, with a shift in the center of gravity of less than 4 mm; in the other 8 patients, a shift in the center of mass of more than 5 mm was noted. No significant correlation between the stability of the cortical muscle representations (the magnitude of the shift in the center of gravity) and the improvement on the WCRS were found.

CONCLUSION

The low-frequency rTMS of the premotor cortex of the contralateral to affected hand hemisphere can be used as an adjuvant therapy for WC. The TMS-motor mapping study did not show its diagnostic value.

New modalities and directions for dystonia care

Dystonia is an abnormal involuntary movement or posture owing to sustained or intermittent muscle contraction. Standard treatment for dystonia includes medications, such as levodopa, anticholinergic and antiepileptic drugs, botulinum toxin, and baclofen pump, and surgeries, such as lesioning surgery and deep-brain stimulation. New treatment modalities aimed toward improving dystonia care in the future are under investigation. There are two main axes to improve dystonia care; one is non-invasive neuromodulation, such as transcranial magnetic stimulation, transcranial electrical stimulation, and transcutaneous electrical nerve stimulation. The other is a quantitative evaluation of dystonia using a wearable device and motion-capturing system, which can be empowered by artificial intelligence. In this article, the current status of these axes will be reviewed.

Reversal of Temporal Discrimination in Cervical Dystonia after Low-Frequency Sensory Stimulation

BACKGROUND

Somatosensory temporal discrimination is abnormal in dystonia and reflects reduced somatosensory inhibition. In healthy individuals, both the latter are enhanced by high-frequency repetitive somatosensory stimulation, whereas opposite effects are observed in patients with cervical dystonia.

OBJECTIVES

We tested whether low-frequency repetitive sensory stimulation, which in healthy individuals worsens discrimination, might have the opposite effect in patients with cervical dystonia at the physiological level and, in turn, improve their perceptual performance.

METHODS

Somatosensory temporal discrimination and several electrophysiological measures of sensorimotor inhibition were collected before and after 45 minutes of low-frequency repetitive sensory stimulation.

RESULTS

As predicted, and opposite to what happened in controls, low-frequency repetitive sensory stimulation in patients enhanced sensorimotor inhibition and normalized somatosensory temporal discrimination.

CONCLUSIONS

Patients with cervical dystonia have an abnormal response to repetitive sensory stimulation, which we hypothesize is attributed to abnormally sensitive homeostatic mechanisms of inhibitory circuitry in both sensory and motor systems. © 2020 International Parkinson and Movement Disorder Society.

Bilateral polymicrogyria associated with dystonia: A new neurogenetic syndrome?

The clinical presentation of bilateral perisylvian polymicrogyria (PMG) is highly variable, including oromotor dysfunction, epilepsy, intellectual disability, and pyramidal signs. Extrapyramidal features are extremely rare. We present four apparently unrelated patients with a unique association of PMG with dystonia. The clinical, genetic, and radiologic features are described and possible mechanisms of dystonia are discussed. All patients were female and two were born to consanguineous families. All presented with early childhood onset dystonia. Other neurologic symptoms and signs classically seen in bilateral perisylvian PMG were observed, including oromotor dysfunction and speech abnormalities ranging from dysarthria to anarthria (4/4), pyramidal signs (3/4), hypotonia (3/4), postnatal microcephaly (1/4), and seizures (1/4). Neuroimaging showed a unique pattern of bilateral PMG with an infolded cortex originating primarily from the perisylvian region in three out of four patients. Whole exome sequencing was performed in two out of four patients and did not reveal pathogenic variants in known genes for cortical malformations or movement disorders. The dystonia seen in our patients is not described in bilateral PMG and suggests an underlying mechanism of impaired connectivity within the motor network or compromised cortical inhibition. The association of bilateral PMG with dystonia in our patients may represent a new neurogenetic disorder.

Non-invasive brain stimulation and kinesiotherapy for treatment of focal dystonia: Instrumental analysis of three cases

Dystonia is a disabling movement disorder characterized by co-contraction of antagonist and agonist muscles, leading to abnormal sustained postures and impaired motor control. Cervical Dystonia (CD) and Hand Focal Dystonia (HFD) have been the most common forms of focal dystonia (FD). Do Non-Invasive Brain Neuromodulation (NIBS) such as Transcranial Direct Current Stimulation (tDCS) and repetitive Transcranial Magnetic Stimulation (rTMS) modulate the excitability of the connections between the motor cortical areas and may represent a therapeutic alternative for focal dystonia? Herein, we reported three cases of focal dystonia, two of them with cervical dystonia (CD) and one with hand focal dystonia (HFD), treated with NIBS combined to kinesiotherapy. The patients were daily submitted to 15 sessions of NIBS combined simultaneously with kinesiotherapy. CD patients were treated with tDCS (2 mA, 20 min, over the primary motor cortex), and HFD patient with rTMS (1 Hz, 1200 pulses, 80% of resting motor threshold, over the premotor cortex). For the CD patient's assessment, the Modified Toronto Scale for Cervical Dystonia Assessment (MTS), quiet balance test, and visual postural assessment were applied to observe the therapeutic effects. Quality handwriting analysis, tremor acceleration amplitudes, and the Wrinter's Cramp Rating Scale (WCRS) were used to assess the NIBS effect on HFD symptoms. Patients were evaluated before (pretest), immediately after (posttest), and three months after treatment (retention). NIBS associated with kinesiotherapy produced a long-term improvement of dystonia symptoms in all three patients. rTMS and tDCS associated with kinesiotherapy showed to be useful and safe to relief the dystonia symptoms in individuals with different types of focal dystonia with distinct functional disorders. SIGNIFICANCE: The combined use of these intervention strategies seems to optimize and anticipate satisfactory clinical results in these neurological conditions, characterized by its difficult clinical management.

Surface Electrical Stimulation for Persistent Stuttering and Concomitant Orofacial Disorders: A Multiple Case Study

This multiple case study analysis describes the immediate effects on speech fluency of transcutaneous electrical nerve stimulation (TENS) applied to participants with persistent stuttering and concomitant orofacial disorders. Study participants were 14 adolescents and adults who stuttered and had jaw clenching bruxism or mouth breathing. Participants experienced low-frequency TENS applied at mild motor level for 20 minutes with electrodes placed at the lower third of the face (Area A), submandibular region (Area B), posterior neck (Area C), or shoulder girdle (Area D), with speech fluency assessed immediately before and after each stimulation.For participants with stuttering and bruxism, AB stimulation reduced the median frequency of syllables stuttered by 27% and reduced the median duration of the three highest stuttering moments by 29%. In addition, for participants with stuttering and mouth breathing, CD stimulation reduced the median duration of the three highest stuttering moments by 28% and increased their median speech rate by 113%. As a single session of TENS may help participants with stuttering and concomitant orofacial disorders better use fluency shaping techniques, the therapeutic potential of TENS for treating stuttering should be further investigated.

Defining research priorities in dystonia

OBJECTIVE

Dystonia is a complex movement disorder. Research progress has been difficult, particularly in developing widely effective therapies. This is a review of the current state of knowledge, research gaps, and proposed research priorities.

METHODS

The NIH convened leaders in the field for a 2-day workshop. The participants addressed the natural history of the disease, the underlying etiology, the pathophysiology, relevant research technologies, research resources, and therapeutic approaches and attempted to prioritize dystonia research recommendations.

RESULTS

The heterogeneity of dystonia poses challenges to research and therapy development. Much can be learned from specific genetic subtypes, and the disorder can be conceptualized along clinical, etiology, and pathophysiology axes. Advances in research technology and pooled resources can accelerate progress. Although etiologically based therapies would be optimal, a focus on circuit abnormalities can provide a convergent common target for symptomatic therapies across dystonia subtypes. The discussions have been integrated into a comprehensive review of all aspects of dystonia.

CONCLUSION

Overall research priorities include the generation and integration of high-quality phenotypic and genotypic data, reproducing key features in cellular and animal models, both of basic cellular mechanisms and phenotypes, leveraging new research technologies, and targeting circuit-level dysfunction with therapeutic interventions. Collaboration is necessary both for collection of large data sets and integration of different research methods.

[Diagnostic and therapeutic issues of using transcranial magnetic stimulation in patients with writer's cramp]

AIM

To assess diagnostic and therapeutic values of transcranial magnetic stimulation (TMS) in patients with writer's cramp (WC).

MATERIAL AND METHODS

Twelve right-handed patients with WC were enrolled in the study. All patients underwent low-frequency repetitive TMS (rTMS) over the premotor cortex of the hemisphere contralateral to the affected hand. The clinical efficacy was assessed using the Writer's Cramp Rating Scale (WCRS) and the Medical Outcomes Study-Short Form (MOS-SF-36). Before and after the last rTMS session, motor mapping of abductor pollicis brevis muscle (APB) was performed using navigated TMS (nTMS). Localization, area, and amplitude-weighted area of the APB muscle cortical representations were compared with the healthy controls. The dynamics of the mentioned above parameters after the rTMS course was assessed.

RESULTS

Ten sessions of low-frequency rTMS over premotor cortex reduced the severity of WC clinical symptoms, with a duration of effect of at least 1 month (p<0.05). There was no significant difference between the area and the weighted area of cortical muscle representations between patients and healthy controls or in patients before and after rTMS. When assessing the localization of cortical muscle representations, two trends were noted: in 4 patients, the localization remained stable, with a shift in the center of gravity of less than 4 mm; in the other 8 patients, a shift in the center of gravity of more than 5 mm was noted. No significant correlations between the stability of the cortical muscle representations (the magnitude of the shift in the center of gravity) and the improvement on the WCRS scale were found.

CONCLUSION

The low-frequency rTMS over the premotor cortex of the hemisphere contralateral to the affected hand can be used as an adjuvant therapy for WC. The TMS-motor mapping study did not show its diagnostic value.

Lasting Effects of Low-Frequency Repetitive Transcranial Magnetic Stimulation in Writer's Cramp: A Case Report

The treatment of writer’s cramp (W’sC) is essentially based on the use of botulinum toxin. However, additional treatments are sometime required to prolong the effects of the toxin, compensate for its progressive loss of efficacy in some subjects, and re-educate handwriting (e.g., rehabilitation strategies). Low-frequency repetitive transcranial magnetic stimulation (rTMS) has been employed to improve W’sC, but with short-lasting and controversial outcomes. We report on the effects of a long-lasting low-frequency rTMS paradigm on W’sC symptoms. A 25-year-old male with a diagnosis of simple W’sC was enrolled in the study. He underwent an objective assessment using the Writer’s Cramp Rating Scale (WCRS) and the 1-min writing test. Further, we recorded muscle activation of the upper limb during handwriting using an EMG wireless system. The patient was provided with 1,200 biphasic magnetic pulses delivered at 1 Hz over the left premotor cortex (PMC), 15 times scheduled every 2 days, thus covering a period of 5 weeks, followed by 10 days of rest. This block of stimulations was practiced other four times, for a period of 6 months. The patient showed a gradual clinical improvement with the progression of the treatments. W’sC symptoms totally disappeared and all the clinical scores showed a significant improvement after rTMS completion. Such improvement lasted up to 1 year after the end of the treatment. Moreover, we detected a long-lasting improvement in sensorimotor plasticity as measured by a paired associative stimulation protocol. Our case suggests that the long-lasting application of 1 Hz rTMS to PMC is a safe and potentially valuable tool to improve W’sC symptoms enduringly, probably by reverting maladaptive plasticity mechanisms within the sensory-motor areas of the hemisphere contralateral to the dystonic hand.

The use of transcranial magnetic stimulation as a treatment for movement disorders: A critical review

BACKGROUND

Transcranial magnetic stimulation is a safe and painless non-invasive brain stimulation technique that has been largely used in the past 30 years to explore cortical function in healthy participants and, inter alia, the pathophysiology of movement disorders. During the years, its use has evolved from primarily research purposes to treatment of a large variety of neurological and psychiatric diseases. In this article, we illustrate the basic principles on which the therapeutic use of transcranial magnetic stimulation is based and review the clinical trials that have been performed in patients with movement disorders.

METHODS

A search of the PubMed database for research and review articles was performed on therapeutic applications of transcranial magnetic stimulation in movement disorders. The search included the following conditions: Parkinson's disease, dystonia, Tourette syndrome and other chronic tic disorders, Huntington's disease and choreas, and essential tremor. The results of the studies and possible mechanistic explanations for the relatively minor effects of transcranial magnetic stimulation are discussed. Possible ways to improve the methodology and achieve greater therapeutic efficacy are discussed.

CONCLUSION

Despite the promising and robust rationales for the use of transcranial magnetic stimulations as a treatment tool in movement disorders, the results taken as a whole are not as successful as were initially expected. There is encouraging evidence that transcranial magnetic stimulation may improve motor symptoms and depression in Parkinson's disease, but the efficacy in other movement disorders is unclear. Possible improvements in methodology are on the horizon but have yet to be implemented in large clinical studies. © 2019 International Parkinson and Movement Disorder Society © 2019 International Parkinson and Movement Disorder Society.

Stereotactic Lesioning of the Thalamic Vo Nucleus for the Treatment of Writer's Cramp (Focal Hand Dystonia)

Writer's cramp (focal hand dystonia) is a sporadic focal dystonia that affects a specific part of the upper limb causing excessive co-contraction of antagonistic muscles. It usually presents as a task-specific dystonia, including, among others, writing of a character or playing a musical instrument. Although treatments for writer's cramp exist, medical therapy often results in unsatisfactory outcomes in patients with this type of dystonia. However, accumulating evidence suggests that long-term and complete remission of various types of focal hand dystonia can be achieved with stereotactic ablation or deep brain stimulation of the thalamic ventral-oralis complex (Vo) nucleus, which includes both the ventralis oralis posterior and anterior nuclei of the thalamus. Following the striking therapeutic success of Vo thalamotomy in patients with medically-refractory writer's cramp, we here introduce the use of stereotactic lesioning of the thalamic Vo nucleus for the treatment of this focal type of dystonia. Our findings identified patients with disabling writer's cramp (i.e., it prevents their success in their professional careers) to be good candidates for positive outcome with this surgical technique.

Dystonia

Dystonia is a neurological condition characterized by abnormal involuntary movements or postures owing to sustained or intermittent muscle contractions. Dystonia can be the manifesting neurological sign of many disorders, either in isolation (isolated dystonia) or with additional signs (combined dystonia). The main focus of this Primer is forms of isolated dystonia of idiopathic or genetic aetiology. These disorders differ in manifestations and severity but can affect all age groups and lead to substantial disability and impaired quality of life. The discovery of genes underlying the mendelian forms of isolated or combined dystonia has led to a better understanding of its pathophysiology. In some of the most common genetic dystonias, such as those caused by TOR1A, THAP1, GCH1 and KMT2B mutations, and idiopathic dystonia, these mechanisms include abnormalities in transcriptional regulation, striatal dopaminergic signalling and synaptic plasticity and a loss of inhibition at neuronal circuits. The diagnosis of dystonia is largely based on clinical signs, and the diagnosis and aetiological definition of this disorder remain a challenge. Effective symptomatic treatments with pharmacological therapy (anticholinergics), intramuscular botulinum toxin injection and deep brain stimulation are available; however, future research will hopefully lead to reliable biomarkers, better treatments and cure of this disorder.

Genetic Dystonia-ataxia Syndromes: Clinical Spectrum, Diagnostic Approach, and Treatment Options

BACKGROUND

Dystonia and ataxia are manifestations of numerous disorders, and indeed, an ever-expanding spectrum of genes causing diseases that encompass dystonia and ataxia are discovered with the advances of genetic techniques. In recent years, a pathophysiological link between both clinical features and the role of the cerebellum in the genesis of dystonia, in some cases, has been proposed. In clinical practice, the genetic diagnosis of dystonia-ataxia syndromes is a major issue for genetic counseling, prognosis and, occasionally, specific treatment.

METHODS

For this pragmatic and educational review, we conducted a comprehensive and structured literature search in Pubmed, OMIM, and GeneReviews using the key words "dystonia" and "ataxia" to identify those genetic diseases that may combine dystonia with ataxia.

RESULTS

There are a plethora of genetic diseases causing dystonia and ataxia. We propose a series of clinico-radiological algorithms to guide their differential diagnosis depending on the age of onset, additional neurological or systemic features, and imaging findings. We suggest a sequential diagnostic approach to dystonia-ataxia syndromes. We briefly highlight the pathophysiological links between dystonia and ataxia and conclude with a review of specific treatment implications.

CONCLUSIONS

The clinical approach presented in this review is intended to improve the diagnostic success of clinicians when faced with patients with dystonia-ataxia syndromes.

Management of Pediatric Movement Disorders: Present and Future

Management of movement disorders in children is an evolving field. This article outlines the major categories of treatment options for pediatric movement disorders and general guidelines for their use. We review the evidence for existing therapies, which continue to lack large-scale controlled trials to guide treatment decisions. The field continues to rely on extrapolations from adult studies and lower quality evidence such as case reports and case series to guide treatment guidelines and consensus statements. Developments in new pharmaceuticals for rare diseases have begun to provide hope for those cases in which a genetic diagnosis can be made. Advances in surgical therapies such as deep brain stimulation as well as new modes of treatment such as gene therapy, epigenetic modulation, and stem cell therapy hold promise for improving outcomes in both primary and secondary causes of movement disorders. There is a critical need for larger, multicenter, controlled clinical trials to fully evaluate treatments for pediatric movement disorders.

The Anatomical Basis for Dystonia: The Motor Network Model

Background

The dystonias include a clinically and etiologically very diverse group of disorders. There are both degenerative and non-degenerative subtypes resulting from genetic or acquired causes. Traditionally, all dystonias have been viewed as disorders of the basal ganglia. However, there has been increasing appreciation for involvement of other brain regions including the cerebellum, thalamus, midbrain, and cortex. Much of the early evidence for these other brain regions has come from studies of animals, but multiple recent studies have been done with humans, in an effort to confirm or refute involvement of these other regions. The purpose of this article is to review the new evidence from animals and humans regarding the motor network model, and to address the issues important to translational neuroscience.

Methods

The English literature was reviewed for articles relating to the neuroanatomical basis for various types of dystonia in both animals and humans.

Results

There is evidence from both animals and humans that multiple brain regions play an important role in various types of dystonia. The most direct evidence for specific brain regions comes from animal studies using pharmacological, lesion, or genetic methods. In these studies, experimental manipulations of specific brain regions provide direct evidence for involvement of the basal ganglia, cerebellum, thalamus and other regions. Additional evidence also comes from human studies using neuropathological, neuroimaging, non-invasive brain stimulation, and surgical interventions. In these studies, the evidence is less conclusive, because discriminating the regions that cause dystonia from those that reflect secondary responses to abnormal movements is more challenging.

Discussion

Overall, the evidence from both animals and humans suggests that different regions may play important roles in different subtypes of dystonia. The evidence so far provides strong support for the motor network model. There are obvious challenges, but also advantages, of attempting to translate knowledge gained from animals into a more complete understanding of human dystonia and novel therapeutic strategies.