Efficacy of pharmacological treatment of dystonia: evidence-based review including meta-analysis of the effect of botulinum toxin and other cure options

Pharmacological and neurosurgical management of cerebral palsy and dystonia: Clinical practice guideline update

Dystonia, typically characterized by slow repetitive involuntary movements, stiff abnormal postures, and hypertonia, is common among individuals with cerebral palsy (CP). Dystonia can interfere with activities and have considerable impact on motor function, pain/comfort, and ease of caregiving. Although pharmacological and neurosurgical approaches are used clinically in individuals with CP and dystonia that is causing interference, evidence to support these options is limited. This clinical practice guideline update comprises 10 evidence-based recommendations on the use of pharmacological and neurosurgical interventions for individuals with CP and dystonia causing interference, developed by an international expert panel following the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. The recommendations are intended to help inform clinicians in their use of these management options for individuals with CP and dystonia, and to guide a shared decision-making process in selecting a management approach that is aligned with the individual's and the family's values and preferences.

The efficacy and safety of intra-articular botulinum toxin type A injection for knee osteoarthritis: A meta-analysis of randomized controlled trials

The purpose of this study was to investigate the efficacy and safety of intra-articular Botulinum Toxin type A (BTA) injection in the management of patients with knee osteoarthritis (KOA). The literature retrieval was conducted based on PRISMA guidelines. Databases including Pubmed, Web of science, EMBASE, and Cochrane Library were searched to identify RCTs that comparing the effects of intra-articular BTA injection with control interventions on patients with KOA. The primary outcomes involved pain and function improvements as well as the occurrence of adverse events. Seven RCTs comprising 548 participants were included in this meta-analysis. Compared with the control group, BTA injection exhibited greater pain reduction at 4 weeks posttreatment (SMD = -0.86, 95% CI [-1.52, -0.19], p = 0.011), but not 8-24 weeks posttreatment (wk 8, SMD = -0.53, 95% CI [-1.21, 0.15], p = 0.127; wk 12, SMD = -0.34, 95% CI [-0.73, 0.04], p = 0.081; wk 24, SMD = -0.65, 95% CI [-1.52, 0.22], p = 0.144). Additionally, no differences were found between BTA injection versus control intervention on functional improvement at all time points assessed (wk 4, WMD = -5.16, 95% CI [-12.31, 2.00], p = 0.158; wk 8, WMD = -0.98, 95% CI [-5.66, 3.71], p = 0.683; wk 12, WMD = -2.52, 95% CI [-7.54, 2.50], p = 0.325); wk 24, WMD = -3.66, 95% CI [-14.09, 6.76], p = 0.491). There was no significant difference in adverse event rate between the BTA and control group (OR = 0.88, 95% CI [0.24, 3.18], p = 0.843). This meta-analysis suggests that intra-articular BTA injection could be an efficious and safe strategy for analgesic treatment of KOA. However, evidence is limited due to the small number and heterogeneity of included studies, this urges further and stronger trials to confirm our findings.

Botulinum toxin for motor disorders

Botulinum neurotoxins are a group of biological toxins produced by the gram-negative bacteria Clostridium botulinum. After intramuscular injection, they produce dose-related muscle relaxation, which has proven useful in the treatment of a large number of motor and movement disorders. In this chapter, we discuss the utility of botulinum toxin treatment in three major and common medical conditions related to the dysfunction of the motor system, namely dystonia, tremor, and spasticity. A summary of the existing literature is provided along with different techniques of injection including those recommended by the authors.

Trihexyphenidyl in young children with dystonic cerebral palsy: A single arm study

PURPOSE

The incidence of dystonic cerebral palsy causing significant morbidity is on the rise. There is a paucity of evidence for the management of dystonia in children.

METHODS

Forty-one children aged 6 months-5 years with predominantly dystonic cerebral palsy were started on a predetermined protocol of trihexyphenidyl (0.25-0.52 mg/kg) and followed up at 3, 6 and 12 weeks. Dystonia severity, motor function and developmental age at baseline and 12 weeks were compared using the Global Dystonia Scale (GDS), the Gross Motor Function Measure (GMFM), and Fine Motor/Perceptual Subscale of the Early Developmental Profile-2. Thirty-four children completed the entire 12 weeks of intervention.

RESULTS

The mean age of participants was 25±11 months. A significant decrease in median total dystonia scores on the GDS was observed post-intervention (74.5 to 59, p <  0.0001), and 64% of participants gained motor milestones. GMFM scores increased significantly from a median of 19.8% pre-intervention to 26.5% post-intervention (p <  0.0001). There was improvement in the fine motor domain as compared to the baseline (p <  0.0001). The number of children classified at Gross Motor Function Classification System levels 1 and 2 increased to 47.05% from 5.88% in the pre-intervention group.

CONCLUSION

Trihexyphenidyl significantly improved dystonia, motor function and development in children with dystonic cerebral palsy in this study. Additional studies are needed to clarify its role in larger numbers of children with this condition.

Movement disorders of the mouth: a review of the common phenomenologies

Movement disorders of the mouth encompass a spectrum of hyperactive movements involving the muscles of the orofacial complex. They are rare conditions and are described in the literature primarily in case reports originating from neurologists, psychiatrists, and the dental community. The focus of this review is to provide a phenomenological description of different oral motor disorders including oromandibular dystonia, orofacial dyskinesia and orolingual tremor, and to offer management strategies for optimal treatment based on the current literature. A literature search of full text studies using PubMed/Medline and Cochrane library combined with a manual search of the reference lists was conducted until June 2021. Results from this search included meta-analyses, systematic reviews, reviews, clinical studies, case series, and case reports published by neurologists, psychiatrists, dentists and oral and maxillofacial surgeons. Data garnered from these sources were used to provide an overview of most commonly encountered movement disorders of the mouth, aiding physicians in recognizing these rare conditions and in initiating appropriate therapy.

Efficacy and Safety of Zolpidem for Focal Dystonia After Neurosurgical Treatments: A Retrospective Cohort Study

Although there are several reports of the significant efficacy of zolpidem for treating dystonia, zolpidem is still considered an anecdotal treatment. Here, we evaluated the efficacy and safety of zolpidem for treating residual dystonia in patients who previously received various neurosurgical treatments majorly including deep brain stimulation and radiofrequency ablation. We retrospectively reviewed medical records from January 2021 to September 2021 to identify patients with dystonia who had been prescribed zolpidem after undergoing neurosurgery. Twenty patients were enrolled in this study, including those with blepharospasm (two), tongue dystonia (four), mouth dystonia (one), spasmodic dysphonia (two), cervical dystonia (six), focal hand dystonia (three), hemidystonia (two), blepharospasm with cervical dystonia (one), and mouth dystonia with cervical dystonia (one). Single doses of zolpidem ranged between 2.5 and 10 mg, while daily dosages ranged from 10 to 30 mg. The zolpidem dose prescribed was 5–10 mg, with single and daily doses of 7 ± 2.9 and 14.5 ± 6.0 mg, respectively. With zolpidem administration, the participants' Burke-Fahn-Marsden Dystonia Rating Scale-Movement Scale score significantly improved from 8.1 ± 6.7 to 3.7 ± 2.5 (50.6% improvement, p < 0.0001). Improvements in arm dystonia, blepharospasm, and spasmodic dysphonia were observed using the Arm Dystonia Disability Scale, Jankovic Rating Scale, and Voice Handicap Index, respectively. No improvements were observed in cervical dystonia on the Toronto Western Spasmodic Torticollis Rating Scale. Drowsiness, including three cases each of mild and moderate drowsiness, was the most frequent adverse effect (30%), which persisted for 2–3 h. Transient amnesia and rapid eye movement sleep behavior disorder occurred in two patients and one patient, respectively. Although our findings suggest that zolpidem can be a valuable treatment option for patients with residual dystonia after neurosurgical treatments, the beneficial effects for cervical dystonia were limited.

Perspectives on the pharmacological management of dystonia

Introduction: Treatment of dystonia is particularly complex due to various etiologies and heterogeneous clinical manifestation, as well as different degrees of disability. In absence of causative treatment, all symptomatic therapy should be predominantly tailored to ameliorate those symptoms (motor and non/motor) that mostly affect patients' daily life and regular activities. Many different treatment options, including oral medications, neurosurgical interventions, physical and occupational therapy are available in treatment of dystonia.Areas covered: The aim of this perspective is to point out different possibilities in pharmacological management of dystonic movements. Due to pure clinical presentation, the authors concentrate mainly on the isolated dystonias, which are presented solely as dystonic movements. Combined and complex dystonias are not instructive due to compound clinical presentation and consequently, complicated treatment. The article is based on a literature search from sources including PubMed, the Cochrane Library, Web of Science, PiCarta, and PsycINFO.Expert opinion: Although dystonia therapy should be adapted according to the individual needs, severity, age, type, symptoms distribution and acceptable side-effect profile, certain principles should be followed to reach the optimal result. Furthermore, the authors believe that a better understanding of the pathophysiology of dystonia will bring with it the development of new and improved treatment approaches and medications.

Safety and efficacy of unilateral and bilateral pallidotomy for primary dystonia

Objective

Ablation of the globus pallidus internus (pallidotomy) is an effective surgical intervention for dystonia. However, the current literature on the efficacy and safety of pallidotomy for dystonia is derived only from single‐case reports and small cohort studies.

Methods

We retrospectively analyzed patients with primary dystonia who underwent pallidotomy at our institution between 2014 and 2019. Neurological conditions were evaluated using the Burke‐Fahn‐Marsden Dystonia Rating Scale (BFMDRS, range: 0–120). We evaluated the total BFMDRS score and each subitem score (nine body regions) in the patients who underwent unilateral and bilateral pallidotomy before surgery and at last available follow‐up. Moreover, postoperative complications were analyzed.

Results

We found that 69 and 20 patients underwent unilateral and bilateral pallidotomy respectively. The mean age at dystonia onset was 40.4 ± 15.2 years. The mean clinical follow‐up period was 17.2 ± 11.6 months. Unilateral pallidotomy significantly improved the total BFMDRS score from 11.2 ± 14.7 preoperatively to 5.4 ± 7.6 at last available follow‐up (51.8% improvement, p < 0.001). Furthermore, there was a significant and independent improvement in all midline BFMDRS subitems, including eyes, mouth, speech/swallow, and neck, after unilateral pallidotomy. Bilateral pallidotomy significantly improved the total BFMDRS score from 14.6 ± 10.2 preoperatively to 3.8 ± 8.2 at last available follow‐up (74.0% improvement, p < 0.001). However, bilateral pallidotomy induced medically refractory parkinsonism (postural instability and gait disturbance) in five patients, dysarthria in three patients, and dysphagia in one patient.

Interpretation

Unilateral radiofrequency pallidotomy remains a viable treatment option for patients with some forms of dystonia. Bilateral pallidotomy cannot be recommended due to unacceptably high complication rates.

Bilateral Pallidal Stimulation with Directional Leads for Primary Focal Lingual Dystonia

There have been limited studies regarding stereotactic and functional neurosurgery for lingual dystonia. Here, we report a patient with primary lingual dystonia who showed significant improvement after bilateral deep brain stimulation (DBS). A 42-year-old woman presented with a 5- to 6-year history of tongue protrusion; however, she lacked a significant medical or medication history before onset. She presented with gradually worsening symptoms and was diagnosed with idiopathic lingual dystonia. Her tongue was injected with botulinum toxin on 6 occasions; however, it had a limited effect. Oral medications were ineffective. She underwent DBS since her involuntary tongue movements were causing nocturnal breathing problems. Directional leads were bilaterally inserted into the internal segment of the globus pallidus (GPi). The directional part of each lead was inserted at the GPi bottom on both sides. The posteromedial contacts were used to deliver stimulation. After 1.5 years, the patient's Burke-Fahn-Marsden dystonia rating scale score improved from 9 to 1.5 and 2 to 1 for movement and disability, respectively. This case demonstrated the effectiveness of bilateral GPi-DBS. Placing the directional part of the lead in the GPi bottom could improve the stimulation effects.

Medical and Surgical Treatments for Dystonia

The dystonias are a large and heterogenous group of disorders characterized by excessive muscle contractions leading to abnormal postures and/or repetitive movements. Their clinical manifestations vary widely, and there are many potential causes. Despite the heterogeneity, helpful treatments are available for the vast majority of patients. Symptom-based therapies include oral medications, botulinum toxins, and surgical interventions. For some subtypes of dystonia, specific mechanism-based treatments are available. Advances in understanding the biological basis for many types of dystonia have led to numerous recent clinical trials, so additional treatments are likely to become available in the very near future.

Evaluation of a programming algorithm for deep brain stimulation in dystonia used in a double-blind, sham-controlled multicenter study

Background

Programming deep brain stimulation in dystonia is difficult because of the delayed benefits and absence of evidence-based guidelines. Therefore, we evaluated the efficacy of a programming algorithm applied in a double-blind, sham-controlled multicenter study of pallidal deep brain stimulation in dystonia.

Methods

A standardized monopolar review to identify the contact with the best acute antidystonic effect was applied in 40 patients, who were then programmed 0.5 V below the adverse effect threshold and maintained on these settings for at least 3 months, if tolerated. If no acute effects were observed, contact selection was based on adverse effects or anatomical criteria. Three-year follow-up data was available for 31 patients, and five-year data for 32 patients. The efficacy of the algorithm was based on changes in motor scores, adverse events, and the need for reprogramming.

Results

The mean (±standard deviation) dystonia motor score decreased by 73 ± 24% at 3 years and 63 ± 38% at 5 years for contacts that exhibited acute improvement of dystonia (n = 17) during the monopolar review. Contacts without acute benefit improved by 58 ± 30% at 3 years (n = 63) and 53 ± 31% at 5 years (n = 59). Interestingly, acute worsening or induction of dystonia/dyskinesia (n = 9) correlated significantly with improvement after 3 years, but not 5 years.

Conclusions

Monopolar review helped to detect the best therapeutic contact in approximately 30% of patients exhibiting acute modulation of dystonic symptoms. Acute improvement, as well as worsening of dystonia, predicted a good long-term outcome, while induction of phosphenes did not correlate with outcome.

Trial registration

ClinicalTrials.gov NCT00142259.

Fu's subcutaneous needling and constraint-induced movement therapy for a patient with chronic stroke: One-year follow-up case report

RATIONALE

Spasticity is a common issue in chronic stroke. To date, no study has reported the long-term (up to 1 year) outcomes of Fu's subcutaneous needling in combination with constraint-induced movement therapy in chronic stroke. This report describes the successful addition of acupuncture on spasticity and arm function in a patient with chronic stroke and arm paresis.

PATIENT CONCERNS

The patient suffered an infarction in the right posterior limb of the internal capsule 1 year ago, which resulted in hemiparesis in his left (nondominant) hand and arm. The only limitation for constraint-induced movement therapy was insufficient finger extension. The patient was unable to voluntarily extend his interphalangeal or metacarpophalangeal joints beyond the 10 degrees required for constraint-induced movement therapy. However, his muscle tension did not change after the BTX type A injection.

DIAGNOSES

A 35-year-old male experienced arm paresis after an infarction in the right posterior limb of the internal capsule 1 year before the intervention.

INTERVENTIONS

The BTX type A injection did not work, so the patient received Fu's subcutaneous needling as an alternative therapy before 5 h of constraint-induced movement therapy for 12 weekdays.

OUTCOMES

All outcome measures (Modified Ashworth Scale, Fugl-Meyer Assessment, Action Research Arm Test, and Motor Activity Log) substantially improved over the 1-year period. Moreover, during the observation period, the patient's muscle tone and arm function did not worsen.

LESSONS

As a result of a reduction in spasticity, a reduction of learned nonuse behaviors, or use-dependent plasticity after the combined therapy, the arm functions include volitional movements, and coordination or speed of movements in the paretic arm have been improved. However, we cannot rule out the possibility of an influence of the passage of time or the Hawthorne effect. The costs of the treatment of stroke may be reduced, if this combined therapy proved useful in future controlled studies.

Safety and long-term efficacy of ventro-oral thalamotomy for focal hand dystonia: A retrospective study of 171 patients

Objective

To report the safety and long-term efficacy of ventro-oral thalamotomy for 171 consecutive patients with task-specific focal hand dystonia.

Methods

Between October 2003 and February 2017, 171 consecutive patients with task-specific focal hand dystonia underwent unilateral ventro-oral thalamotomy. Etiologies included writer's cramps (n = 92), musician's dystonias (n = 58), and other occupational task-related dystonias (n = 21). The task-specific focal hand dystonia scale was used to evaluate patients' neurologic conditions (range 1–5, high score indicated a better condition). The scores before surgery; at 1 week, 3 months, and 12 months postoperatively; and the last available follow-up period were determined. Postoperative complications and postoperative recurrence were also evaluated.

Results

The scores before surgery; at 1 week (1.72 ± 0.57, 4.33 ± 0.85 [p < 0.001]), 3 months (4.30 ± 1.06 [p < 0.001]), and 12 months (4.30 ± 1.13 [p < 0.001]); and the last available follow-up (4.39 ± 1.07 [p < 0.001]) postoperatively improved. The mean clinical follow-up period was 25.4 ± 32.1 months (range: 3–165). Permanent adverse events developed in 6 patients (3.5%). Eighteen patients developed recurrent dystonic symptoms postoperatively. Of these 18 patients, 9 underwent ventro-oral thalamotomy again, of which 7 achieved improvement.

Conclusion

Ventro-oral thalamotomy is a feasible and reasonable treatment for patients with refractory task-specific focal hand dystonias. Prospective, randomized, and blinded studies are warranted to clarify more accurate assessment of the safety and efficacy of ventro-oral thalamotomy for task-specific focal hand dystonia.

Classification of evidence

This study provides Class IV evidence that for patients with task-specific focal hand dystonia, ventro-oral thalamotomy improves dystonia.

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.

Pharmacological and neurosurgical interventions for managing dystonia in cerebral palsy: a systematic review

AIM

To systematically review evidence for pharmacological/neurosurgical interventions for managing dystonia in individuals with cerebral palsy (CP) to inform a care pathway.

METHOD

Searches included studies with a minimum of five participants with dystonia in CP receiving oral baclofen, benzodiazepines (clonazepam, diazepam, lorazepam), clonidine, gabapentin, levodopa, trihexyphenidyl, botulinum toxin, intrathecal baclofen (ITB), or deep brain stimulation (DBS). Evidence was classified according to American Academy of Neurology guidelines.

RESULTS

Twenty-eight articles underwent data extraction: one levodopa, five trihexyphenidyl, three botulinum toxin, six ITB, and 13 DBS studies. No articles for oral baclofen, benzodiazepines, clonidine, or gabapentin met the inclusion criteria. Evidence for reducing dystonia was level C (possibly effective) for ITB and DBS; level C (possibly ineffective) for trihexyphenidyl; and level U (inadequate data) for botulinum toxin.

INTERPRETATION

For dystonia reduction, ITB and DBS are possibly effective, whereas trihexyphenidyl was possibly ineffective. There is insufficient evidence to support oral medications or botulinum toxin to reduce dystonia. There is insufficient evidence for pharmacological and neurosurgical interventions to improve motor function, decrease pain, and ease caregiving. The majority of the pharmacological and neurosurgical management of dystonia in CP is based on clinical expert opinion.

WHAT THIS PAPER ADDS

Intrathecal baclofen and deep brain stimulation are possibly effective in reducing dystonia. Current evidence does not support effectiveness of oral medications or botulinum toxin to reduce dystonia. Evidence is inadequate for pharmacological/neurosurgical interventions impact on improving motor function, pain/comfort, and easing caregiving. The majority of the care pathway rests on expert opinion.

Acupuncture and constraint-induced movement therapy for a patient with chronic stroke: One-year follow-up case report

RATIONALE

Spasticity is a widespread problem in chronic stroke. To date, no study has reported the long-term (up to 1 year) outcomes of acupuncture in combination with constraint-induced movement therapy in patients with chronic stroke. This report describes the successful addition of acupuncture on spasticity and arm function in a patient with chronic stroke and arm paresis.

PATIENT CONCERNS

At screening, the patient was unable to voluntarily extend her interphalangeal or metacarpophalangeal joints beyond the 10 degrees required for constraint-induced movement therapy. However, the BTX type A injection couldn't be used as she had ever suffered a severe allergic reaction in the injection of BTX type A for facial anti-wrinkle.

DIAGNOSES

A 40-year-old female experienced arm paresis after an infarction in the right posterior limb of the internal capsule 2 years before the intervention.

INTERVENTIONS

The BTX type A injection couldn't be used as she had ever suffered a severe allergic reaction in the injection of BTX type A for facial anti-wrinkle, so the patient received 1 hour of acupuncture as an alternative therapy before 5 hours of constraint-induced movement therapy for 12 weekdays.

OUTCOMES

All outcome measures (Modified Ashworth Scale, Fugl-Meyer Assessment, Action Research Arm Test, Motor Activity Log) substantially improved over the 1-year period. Moreover, during the observation period, the patient's muscle tone and arm function did not worsen.

LESSONS

As a result of a reduction in spasticity, a reduction of learned nonuse behaviors, or use-dependent plasticity after the combined therapy, the arm functions include volitional movements and coordination or speed of movements in the paretic arm have been improved. However, we can not rule out the possibility of an influence of the passage of time or the Hawthorne effect. The costs of the treatment of stroke may be reduced, if this combined therapy proved useful in future controlled studies.

Clinical Management of Dystonia in Childhood

Dystonia is one of the most frequent movement disorders in childhood. It can impede normal motor development and cause significant motor disability. The diagnostic evaluation of childhood dystonia is challenging due to the phenotypic variability and heterogeneous etiologies. Evidence to guide the diagnostic evaluation and treatment is limited. Assessment is primarily directed by clinical history and distinctive examination findings. Neuroimaging is typically necessary to evaluate for acquired or complex inherited dystonias. A trial of levodopa can be both diagnostic and therapeutic in children with dopa-responsive dystonia. However, for the majority of children with early-onset dystonia, treatment is symptomatic with varying efficacy. There is a paucity of therapeutic trials for childhood dystonia and most treatment recommendations are consensus or expert opinion driven. This review summarizes the available evidence and guidelines on the diagnostic evaluation and pharmacological treatment of childhood-onset dystonia and provides practical frameworks to approach both issues based on best evidence.

Evaluation of the Edrophonium Challenge Test for Cervical Dystonia

Objective To examine whether or not an edrophonium challenge test is useful for diagnosing cervical dystonia. Patients We evaluated 10 patients with cervical dystonia and 10 with hemifacial spasms (disease controls). We administered edrophonium and saline in this double-blinded study. Before and after the injection, we recorded the participants' clinical signs using a video camera to assess the objective symptoms every two minutes. Ten minutes after the saline and edrophonium injections, participants evaluated their subjective clinical signs using a visual analog scale. The objective signs on the video recordings were scored by specialists who were blinded to the treatment. The mean visual analog scale scores were compared using the Wilcoxon rank-sum test for paired continuous variables. Results The clinical signs of participants with cervical dystonia were amplified by edrophonium. In contrast, the clinical signs in participants with hemifacial spasms were not affected by the edrophonium challenge test. Conclusion The edrophonium challenge test may be useful for diagnosing cervical dystonia.

Functional activity of the sensorimotor cortex and cerebellum relates to cervical dystonia symptoms

Cervical dystonia (CD) is the most common type of focal dystonia, causing abnormal movements of the neck and head. In this study, we used noninvasive imaging to investigate the motor system of patients with CD and uncover the neural correlates of dystonic symptoms. Furthermore, we examined whether a commonly prescribed anticholinergic medication in CD has an effect on the dystonia-related brain abnormalities. Participants included 16 patients with CD and 16 healthy age-matched controls. We collected functional MRI scans during a force task previously shown to extensively engage the motor system, and diffusion and T1-weighted MRI scans from which we calculated free-water and brain tissue densities. The dystonia group was also scanned ca. 2 h after a 2-mg dose of trihexyphenidyl. Severity of dystonia was assessed pre- and post-drug using the Burke-Fahn-Marsden Dystonia Rating Scale. Motor-related activity in CD was altered relative to controls in the primary somatosensory cortex, cerebellum, dorsal premotor and posterior parietal cortices, and occipital cortex. Most importantly, a regression model showed that increased severity of symptoms was associated with decreased functional activity of the somatosensory cortex and increased activity of the cerebellum. Structural imaging measures did not differ between CD and controls. The single dose of trihexyphenidyl altered the fMRI signal in the somatosensory cortex but not in the cerebellum. Symptom severity was not significantly reduced post-treatment. Findings show widespread changes in functional brain activity in CD and most importantly that dystonic symptoms relate to disrupted activity in the somatosensory cortex and cerebellum. Hum Brain Mapp 38:4563-4573, 2017. © 2017 Wiley Periodicals, Inc.

The safety of intra-articular injections for the treatment of knee osteoarthritis: a critical narrative review

INTRODUCTION

International guidelines recommend that the management of knee osteoarthritis (OA) combine both nonpharmacological and pharmacological interventions. Intra-articular (IA) therapies are considered part of this multimodal approach and are well-established Food and Drug Administration (FDA) and European Medicines Agency (EMA)-approved treatments. Areas covered: Safety data for knee OA, including IA corticosteroids, hyaluronic acid, platelet-rich plasma and botulinum toxin are critically reviewed, and evidence- and pratice-based measures to improve safety of IA therapies are discussed. Expert opinion: The incidence of AEs attributable to IA therapies across clinical trials in knee OA is very low, and barely reaches significance when compared to the incidence of AEs in the comparator group. These events are exceptionally serious. Mild differences between products have been inconsistently reported mainly for IA HA. One can distinguish self-limited AEs such as post-injection pain and swelling that are the most frequently reported AEs, from AEs that are not self-limited but rare such as septic arthritis. The safety of IA therapies can be improved by applying simple measures designed to prevent AEs. However, even though no specific safety concerns have been raised to date about IA therapies, the quality of evidence is low, and there is a need to improve the monitoring and reporting of safety data from clinical trials and post-marketing surveillance.

Clonidine use in the outpatient management of severe secondary dystonia

OBJECTIVE

To evaluate the safety, efficacy and effective dosage of clonidine in the outpatient (OP) management of secondary dystonia.

METHODS

A retrospective analysis of children and young people (CAYP) prescribed clonidine in an OP clinic between January 2011 and November 2013 for dystonia management. Of 224 children receiving clonidine, 149/224 did not have a movement disorder and 12/224 had no data leaving 63 movement disorder cases, 15/63 managed as in-patients, 15/48 suffered from tics leaving 33/63 for OP evaluation. Clonidine effectiveness was assessed by 'yes/no' criteria in improving 5 areas: seating, sleep, pain, tone and involuntary movements.

RESULTS

2/33 motor cases had insufficient data; 7/33 had concurrent therapy leaving 24/33 for analysis. Improvement in at least one area was reported by 20/24 (83%) CAYP: Improved seating tolerance 14/24, and sleep 15/24; reduced pain 15/24; improved tone 16/24 and involuntary movements 17/24. Starting doses ranged from 1 mcg/kg OD to 2 mcg/kg TDS with optimum doses reached on average at 9.5 months follow-up. Maximum dose reached was 75 mcg/kg/day given in 8 divided doses. Average maximum daily dose was 20 mcg/kg/day. The commonest frequency of administration was 8 hourly. Side effects were reported in 11/24 CAYP and discontinued in 1/24 for lack of clinical effectiveness, 1/24 for side effects and 4/24 due to both lack of effectiveness and side effects.

CONCLUSION

Clonidine was effective in secondary dystonia management in 83% of cases. A starting dose of 1 mcg/kg TDS was well tolerated and safely escalated. Prospective objective evaluation is now required to confirm the efficacy of clonidine.

Dystonia treatment: Patterns of medication use in an international cohort

OBJECTIVE

To determine the frequency of medication use in patients with dystonia enrolled in an international biorepository study.

METHODS

In a cross-sectional analysis, we included 2,026 participants enrolled at 37 sites in the United States, Canada, Europe, and Australia through Project 1 of the Dystonia Coalition, an international biorepository study. The primary aim was to assess the frequency of medication classes recommended for treating patients with dystonia, and the secondary aim was to compare characteristics (disease type, age, sex, duration of disease, comorbid conditions, severity).

RESULTS

Querying the database for the presence of any medication for dystonia used (includes both injectable and oral therapy), we found 73% using medications (n = 1,488) and 27% using no dystonia medications (n = 538). Furthermore, 61% of the total sample used botulinum toxin (BoNT) therapy alone or in combination. Differences were found in medication use patterns by dystonia type, with the lowest oral medication use in focal dystonia and highest use in generalized dystonia; by region, with highest BoNT therapy rate reported in Italy and the lowest in the Northeast region of the United States; and by focal dystonia subtype, with highest BoNT therapy alone in blepharospasm and spasmodic dysphonia (49%) and lowest in other cranial dystonia (32%).

CONCLUSIONS

The majority of patients with dystonia enrolled in the Dystonia Coalition Project 1 were using medications to treat their dystonia. Overall, a complex picture of medication use patterns emerged, with factors such as region, disease duration, type of dystonia, disease severity, and psychiatric comorbidities all playing a significant role.

Focal task specific dystonia: a review and update

In this review, we summarize recent advances in understanding the etiology, risk factors and pathophysiology of focal task specific dystonia (FTSD), movement disorders characterized by abnormal motor activation during the performance of specific, repetitive actions. We focus on two common FTSD, musician’s dystonia and writer’s cramp. FTSD may pose a threat to the patient’s livelihood, and improved therapeutic treatments are needed.

Understanding dystonia: diagnostic issues and how to overcome them

ABSTRACT The diagnosis and treatment of dystonia are challenging. This is likely due to gaps in the complete understanding of its pathophysiology, lack of animal models for translational studies, absence of a consistent pathological substrate and highly variable phenotypes and genotypes. The aim of this review article is to provide an overview of the clinical, neurophysiological and genetic features of dystonia that can help in the identification of this movement disorder, as well as in the differential diagnosis of the main forms of genetic dystonia. The variation of penetrance, age of onset, and topographic distribution of the disease in carriers of the same genetic mutation indicates that other factors – either genetic or environmental – might be involved in the development of symptoms. The growing knowledge of cell dysfunction in mutants may give insights into more effective therapeutic targets.

Medication use in childhood dystonia

BACKGROUND

Data around current prescription practices in childhood dystonia is limited. Medication use may be limited by side effects, the incidence of which is uncertain. For a large cohort assessed by our supra-regional service we aimed to: i) Review medications used at the point of referral. ii) Determine the prevalence of adverse drug responses (ADR) resulting in discontinuation of drug use. iii) Identify clinical risk factors for ADR.

METHODS

Case note review of 278 children with dystonia referred to our service. Data collected on medications, ADR, dystonia aetiology, Gross Motor Function Classification System (GMFCS) level and motor phenotype (pure dystonia/mixed dystonia-spasticity). Logistic regression analysis was used to identify risk factors for ADR.

RESULTS

At referral 82/278 (29.4%) children were taking no anti-dystonic medication. In the remainder the median number of anti-dystonic medications was 2 (range 1-5). Medications use increased with worsening GMFCS level. The commonest drugs used were baclofen (118/278: 42.4%), trihexyphenidyl (98/278: 35.2%), l-Dopa (57/278: 20.5%) and diazepam (53/278: 19%). Choice of medication appeared to be influenced by dystonia aetiology. ADR had been experienced by 171/278 (61.5%) of children. The commonest drugs responsible for ADR were trihexyphenidyl (90/171: 52.3%), baclofen (43/171: 25.1%) and l-Dopa (26/171: 15.2%). Binary logistic regression demonstrated no clinical risk factors for ADR.

CONCLUSIONS

ADR is commonly experienced by children with dystonia, regardless of dystonia severity or aetiology. A wide variation in drug management of dystonia was identified. Collectively these findings highlight the need for a rational approach to the pharmacological management of dystonia in childhood.

Edrophonium Challenge Test for Blepharospasm

Background: Blepharospasm is typically diagnosed by excluding any secondary diseases and neuropsychiatric disorders, as specific tests for blepharospasm are currently unavailable. Since anticholinergic agents are used to improve the symptoms of dystonia, we hypothesized that edrophonium chloride, an acetylcholinesterase inhibitor, may make the symptoms of dystonia more apparent. Therefore, we examined whether an edrophonium challenge test would be useful for diagnosing blepharospasm.

Methods: We studied 10 patients with blepharospasm and 10 with hemifacial spasms (as disease controls). We administered edrophonium and saline in this double-blind study. Before and after the injection, we recorded the clinical signs using a video camera to assess the objective symptoms every 2 min. Ten minutes after the isotonic sodium chloride and edrophonium injections, the patients evaluated their subjective signs using a visual analog scale (VAS). The objective signs on the video recordings were scored by specialists who were blind to the treatment.

Results: The subjective and objective signs of the patients with blepharospasm were amplified by edrophonium. In contrast, the signs in patients with hemifacial spasms were not changed by the edrophonium challenge test.

Conclusions: The edrophonium challenge test may be used to diagnose blepharospasm. The study was registered with a ICMJE recognized registry, the UMIN-CTR, with the number UMIN000022557.

Advances in management of movement disorders in children

Movement disorders in children are causally and clinically heterogeneous and present in a challenging developmental context. Treatment options are broad ranging, from pharmacotherapy to invasive neuromodulation and experimental gene and stem cell therapies. The clinical effects of these therapies are variable and often poorly sustained, and only a few of the management strategies used in paediatric populations have been tested in randomised controlled studies with age-appropriate cohorts. Identification of the most appropriate treatment is uniquely challenging in children because of the incomplete knowledge about the pathophysiology of movement disorders and their influence on normal motor development; thus, effective therapeutic options for these children remain an unmet need. It is vital to transfer the expanding knowledge of the movement disorders into the development of novel symptomatic or, ideally, disease-modifying treatments, and to assess these therapeutic strategies in appropriately designed and well done trials.

A randomized trial of specialized versus standard neck physiotherapy in cervical dystonia

BACKGROUND

Anecdotal reports suggested that a specialized physiotherapy technique developed in France (the Bleton technique) improved primary cervical dystonia. We evaluated the technique in a randomized trial.

METHODS

A parallel-group, single-blind, two-centre randomized trial compared the specialized outpatient physiotherapy programme given by trained physiotherapists up to once a week for 24 weeks with standard physiotherapy advice for neck problems. Randomization was by a central telephone service. The primary outcome was the change in the total Toronto Western Spasmodic Torticollis Rating (TWSTR) scale, measured before any botulinum injections that were due, between baseline and 24 weeks evaluated by a clinician masked to treatment. Analysis was by intention-to-treat.

RESULTS

110 patients were randomized (55 in each group) with 24 week outcomes available for 84. Most (92%) were receiving botulinum toxin injections. Physiotherapy adherence was good. There was no difference between the groups in the change in TWSTR score over 24 weeks (mean adjusted difference 1.44 [95% CI -3.63, 6.51]) or 52 weeks (mean adjusted difference 2.47 [-2.72, 7.65]) nor in any of the secondary outcome measures (Cervical Dystonia Impact Profile-58, clinician and patient-rated global impression of change, mean botulinum toxin dose). Both groups showed large sustained improvements compared to baseline in the TWSTR, most of which occurred in the first four weeks. There were no major adverse events. Subgroup analysis suggested a centre effect.

CONCLUSION

There was no statistically or clinically significant benefit from the specialized physiotherapy compared to standard neck physiotherapy advice but further trials are warranted.

Botulinum neurotoxin: Progress in negating its neurotoxicity; and in extending its therapeutic utility via molecular engineering. MiniReview

While the poisonous effects of botulinum neurotoxin (BoNT) have been recognized since antiquity, the overall actions and mechanisms of effects of BoNT have been elucidated primarily over the past several decades. The general utility of BoNT is described in the paper, but the focus is mainly on the approaches towards negating the toxic effects of BoNT, and on the projection of an engineered BoNT molecule serving as a Trojan Horse to deliver a therapeutic load for treatment of a host of medical disorders. The BoNT molecule is configured with a binding domain, a zinc-dependent protease with specificity primarily for vesicular proteins, and a translocation domain for delivery of the metalloprotease into the cytoplasm. The anti-toxin approaches for BoNT include the use of vaccines, antibodies, block of BoNT binding or translocation, inhibition of metalloprotease activity, impeded translocation of the protease/catalytic domain, and inhibition of the downstream Src signaling pathway. Projections of BoNT as a therapeutic include its targeting to non-cholinergic nerves, also targeting to non-neuronal cells for treatment of hypersecretory disorders (e.g., cystic fibrosis), and treatment of hormonal disorders (e.g., acromegaly). Still in the exploratory phase, there is the expectation of major advances in BoNT neuroprotective strategies and burgeoning utility of engineered BoNTs as therapeutics.

Diagnosis and treatment of dystonia

The dystonias are a group of disorders characterized by excessive involuntary muscle contractions leading to abnormal postures and/or repetitive movements. A careful assessment of the clinical manifestations is helpful for identifying syndromic patterns that focus diagnostic testing on potential causes. If a cause is identified, specific etiology-based treatments may be available. In most cases, a specific cause cannot be identified, and treatments are based on symptoms. Treatment options include counseling, education, oral medications, botulinum toxin injections, and several surgical procedures. A substantial reduction in symptoms and improved quality of life is achieved in most patients by combining these options.

Childhood dystonias

OPINION STATEMENT

Dystonia is a movement disorder caused by diverse etiologies. Its treatment in children is particularly challenging due to the complexity of the development of the nervous system from birth to young adulthood. The treatment options of childhood dystonia include several oral pharmaceutical agents, botulinum toxin injections, and deep brain stimulation (DBS) therapy. The choice of drug therapy relies on the suspected etiology of the dystonia and the adverse effect profile of the drugs. Dystonic syndromes with known etiologies may require specific interventions, but most dystonias are treated by trying serially a handful of medications starting with those with the best risk/benefit profile. In conjunction to drug therapy, botulinum toxin injections may be used to target a problematic group dystonic muscles. The maximal botulinum toxin dose is limited by the weight of the child, therefore limiting the number of the muscles amenable to such treatment. When drugs and botulinum toxin injections fail to control the child's disabling dystonia, DBS therapy may be offered as a last remedy. Delivering optimal DBS therapy to children with dystonia requires a multidisciplinary team of experienced pediatric neurosurgeons, neurologists, and nurses to select adequate candidates, perform this delicate stereotactic procedure, and optimize DBS delivery. Even in the best hands, the response of childhood dystonia to DBS therapy varies greatly. Future therapy of childhood dystonia will parallel the advancement of knowledge of the pathophysiology of dystonic syndromes and the development of clinical and research tools for their study.

Therapeutic applications of botulinum neurotoxins in head and neck disorders

Objective

The aim of this article is to review the mechanism of action, physiological effects, and therapeutic applications of botulinum neurotoxins in the head and neck area.

Study design

An extensive literature search was performed using keywords. The resulting articles were analyzed for relevance in four areas: overview on botulinum neurotoxins, the role of botulinum neurotoxins in the management of salivary secretory disorders, the role of botulinum neurotoxins in the management of facial pain, and the role of botulinum neurotoxins in head and neck movement disorders. Institutional review board approval was not needed due the nature of the study.

Results

Botulinum neurotoxin therapy was demonstrated to be a valuable alternative to conventional medical therapy for many conditions affecting the head and neck area in terms of morbidly, mortality, and patient satisfaction with treatment outcomes.

Conclusion

Botulinum neurotoxin therapy provides viable alternatives to traditional treatment modalities for some conditions affecting the head and neck region that have neurological components. This therapy can overcome some of the morbidities associated with conventional therapy. More research is needed to determine the ideal doses of botulinum neurotoxin to treat different diseases affecting the head and neck regions.

Pallidal neurostimulation in patients with medication-refractory cervical dystonia: a randomised, sham-controlled trial

BACKGROUND

Cervical dystonia is managed mainly by repeated botulinum toxin injections. We aimed to establish whether pallidal neurostimulation could improve symptoms in patients not adequately responding to chemodenervation or oral drug treatment.

METHODS

In this randomised, sham-controlled trial, we recruited patients with cervical dystonia from centres in Germany, Norway, and Austria. Eligible patients (ie, those aged 18-75 years, disease duration ≥3 years, Toronto Western Spasmodic Torticollis Rating Scale [TWSTRS] severity score ≥15 points) were randomly assigned (1:1) to receive active neurostimulation (frequency 180 Hz; pulse width 120 μs; amplitude 0·5 V below adverse event threshold) or sham stimulation (amplitude 0 V) by computer-generated randomisation lists with randomly permuted block lengths stratified by centre. All patients, masked to treatment assignment, were implanted with a deep brain stimulation device and received their assigned treatment for 3 months. Neurostimulation was activated in the sham group at 3 months and outcomes were reassessed in all patients after 6 months of active treatment. Treating physicians were not masked. The primary endpoint was the change in the TWSTRS severity score from baseline to 3 months, assessed by two masked dystonia experts using standardised videos, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00148889.

FINDINGS

Between Jan 19, 2006, and May 29, 2008, we recruited 62 patients, of whom 32 were randomly assigned to neurostimulation and 30 to sham stimulation. Outcome data were recorded in 60 (97%) patients at 3 months and 56 (90%) patients at 6 months. At 3 months, the reduction in dystonia severity was significantly greater with neurostimulation (-5·1 points [SD 5·1], 95% CI -7·0 to -3·5) than with sham stimulation (-1·3 [2·4], -2·2 to -0·4, p=0·0024; mean between-group difference 3·8 points, 1·8 to 5·8) in the intention-to-treat population. Over the course of the study, 21 adverse events (five serious) were reported in 11 (34%) of 32 patients in the neurostimulation group compared with 20 (11 serious) in nine (30%) of 30 patients in the sham-stimulation group. Serious adverse events were typically related to the implant procedure or the implanted device, and 11 of 16 resolved without sequelae. Dysarthria (in four patients assigned to neurostimulation vs three patients assigned to sham stimulation), involuntary movements (ie, dyskinesia or worsening of dystonia; five vs one), and depression (one vs two) were the most common non-serious adverse events reported during the course of the study.

INTERPRETATION

Pallidal neurostimulation for 3 months is more effective than sham stimulation at reducing symptoms of cervical dystonia. Extended follow-up is needed to ascertain the magnitude and stability of chronic neurostimulation effects before this treatment can be recommended as routine for patients who are not responding to conventional medical therapy.

FUNDING

Medtronic.

Intra-articular botulinum toxin A for the treatment of osteoarthritic joint pain in dogs: a randomized, double-blinded, placebo-controlled clinical trial

The aim of this study was to investigate the efficacy of intra-articular (IA) botulinum toxin A (IA BoNT A) for the treatment of osteoarthritic joint pain in dogs. The study was a placebo-controlled, randomized, double-blinded clinical trial with parallel group design and 12-week follow-up. Thirty-six dogs with chronic lameness due to stifle, hip or elbow osteoarthritis were randomized to receive an IA injection of 30IU of BoNT A or placebo. The main outcome variables were vertical impulse (VI) and peak vertical force (PVF) measured with a force platform, and Helsinki chronic pain index (HCPI). Subjective pain score and the need for rescue analgesics were secondary variables. The response to treatment was assessed as the change from baseline to each examination week. The variables were analyzed by ANOVA with repeated measurements and results were considered statistically significant if P ⩽ 0.05. The improvement from baseline to 12 weeks after baseline was statistically significant in VI, PVF and HCPI in the treatment group (P=0.001, P=0.054 and P=0.053, respectively). Additionally, there were statistically significant improvements in VI in the treatment group at 2, 4 and 8 weeks after baseline (P=0.037, P=0.016 and P=0.016, respectively). The difference between groups in improvement in VI was statistically significant at 12weeks after baseline (P=0.005). There was no significant change in the subjective pain score or in the requirement for rescue analgesics in either group. No major adverse events thought to be related to trial protocol were detected. These results suggest that IA BoNT A has some efficacy in reducing osteoarthritic pain in dogs.

Motor vehicle accidents and injuries in patients with idiopathic blepharospasm

BACKGROUND

Blepharospasm can cause transient functional blindness that may cause catastrophic traffic accidents.

METHODS

Sixty-six patients in southern Taiwan with idiopathic blepharospasm were enrolled. The incidence of and injuries from traffic accidents from the onset of blepharospasm symptoms to the first injection of botulinum toxin were analyzed. Data were collected from medical records and face-to-face interviews with patients and their families.

RESULTS

Twenty-six patients (39.4%) had traffic accidents (21 motorcycle; 5 car). There were 5 incapacitating motorcycle injuries: 1 cervical spine injury with quadriparesis, 1 blunt abdominal injury with internal bleeding, 2 broken limbs, and 1 ligament rupture; 1 incapacitating car injury: broken limb of other person; and 11 non-incapacitating motorcycle injuries (abrasions, bruises, and minor lacerations). Nine patients were uninjured.

CONCLUSIONS

Blepharospasm caused incapacitating injuries for motorcyclists themselves and another person in a car accident. Patients with untreated blepharospasm should avoid riding motorcycles and driving cars.

Long-term improvement of musician's dystonia after stereotactic ventro-oral thalamotomy

OBJECTIVE

Musician's dystonia is a task-specific movement disorder that causes twisting or repetitive abnormal finger postures and movements, which tend to occur only while playing musical instruments. Such a movement disorder will probably lead to termination of the careers of affected professional musicians. Most of the currently available treatments have yet to provide consistent and satisfactory results. We present the long-term follow-up results of ventro-oral thalamotomy for 15 patients with musician's dystonia.

METHODS

Between October 2003 and September 2010, 15 patients with medically intractable task-specific focal hand dystonia that occurred only while playing musical instruments underwent ventro-oral thalamotomy. We used Tubiana's musician's dystonia scale to evaluate the patients' pre- and postoperative neurological conditions.

RESULTS

All patients except 1 (93%) experienced dramatic improvement of dystonic symptoms immediately after ventro-oral thalamotomy. The mean follow-up period was 30.8 months (range=4-108 months). None of the patients experienced recurrence or deterioration of symptoms during the follow-up periods.

INTERPRETATION

Ventro-oral thalamotomy remarkably improved musician's dystonia, and the effect persisted for a long duration.

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.

Oromandibular dystonia: a clinical report

Oromandibular dystonia (OMD) consists of prolonged spasms caused by contraction of the muscles of the mouth and mandible and involves the muscles of mastication, facial expression, tongue, and eye lids. A multidisciplinary treatment approach is presented including the fabrication of a dental prosthesis to reduce/eliminate the symptoms of OMD. Etiology and treatment issues are discussed, emphasizing the importance of an interdisciplinary treatment approach.

Update on pediatric dystonias: etiology, epidemiology, and management

Dystonia is a movement disorder characterized by sustained muscle contractions producing twisting, repetitive, and patterned movements or abnormal postures. Dystonia is among the most commonly observed movement disorders in clinical practice both in adults and children. It is classified on the basis of etiology, age at onset of symptoms, and distribution of affected body regions.

Etiology

The etiology of pediatric dystonia is quite heterogeneous. There are many different genetic syndromes and several causes of symptomatic syndromes. Dystonia can be secondary to virtually any pathological process that affects the motor system, and particularly the basal ganglia.

Classification

The etiological classification distinguishes primary dystonia with no identifiable exogenous cause or evidence of neurodegeneration and secondary syndromes.

Treatment

Treatment for most forms of dystonia is symptomatic and includes drugs (systemic or focal treatments, such as botulinum toxin) and surgical procedures. There are several medications including anticholinergic, dopamine-blocking and depleting agents, baclofen, and benzodiazepines. In patients with dopamine synthesis defects L-dopa treatment may be very useful. Botulinum toxin treatment may be helpful in controlling the most disabling symptoms of segmental or focal dystonia. Long-term electrical stimulation of the globus pallidum internum appears to be especially successful in children suffering from generalized dystonia.

Selective inhibition of striatal fast-spiking interneurons causes dyskinesias

Fast-spiking interneurons (FSIs) can exert powerful control over striatal output, and deficits in this cell population have been observed in human patients with Tourette syndrome and rodent models of dystonia. However, a direct experimental test of striatal FSI involvement in motor control has never been performed. We applied a novel pharmacological approach to examine the behavioral consequences of selective FSI suppression in mouse striatum. IEM-1460, an inhibitor of GluA2-lacking AMPARs, selectively blocked synaptic excitation of FSIs but not striatal projection neurons. Infusion of IEM-1460 into the sensorimotor striatum reduced the firing rate of FSIs but not other cell populations, and elicited robust dystonia-like impairments. These results provide direct evidence that hypofunction of striatal FSIs can produce movement abnormalities, and suggest that they may represent a novel therapeutic target for the treatment of hyperkinetic movement disorders.