Milestones in dystonia

Improvements in Nerve Dissection Surgery Methodology for Spasmodic Torticollis Treatment

Spasmodic torticollis is the most common focal dystonia and is characterized by aberrant involuntary contraction of muscles of the neck and shoulders, which greatly affects patients' quality of life. Consequently, patients with this condition often desire treatment to alleviate their symptoms. The common clinical treatments for spasmodic torticollis include interventions such as drug therapy, botulinum toxin injections, and surgery. Surgical treatment is feasible for patients who do not respond well to other treatments or who are resistant to drugs. The gradual improvement of surgeons' understanding of anatomy and the ongoing developments in surgical techniques since their advent in the 1640s have resulted in many innovative surgical approaches that have led to improvements in the treatment of spasmodic torticollis. Previously used surgical treatments that result in uncertain outcomes, various postoperative complications, and serious damage to motor functions of the head and neck have gradually been discontinued. Nerve dissection surgery is the most common surgical treatment for spasmodic torticollis. This article reviews existing research on nerve dissection surgery for the treatment of spasmodic torticollis and the history of its development, along with the advantages and disadvantages of various surgical improvements. This article aims to provide clinicians with practical advice.

Laryngeal Dystonia: Multidisciplinary Update on Terminology, Pathophysiology, and Research Priorities

OBJECTIVE

To delineate research priorities for improving clinical management of laryngeal dystonia, the NIH convened a multidisciplinary panel of experts for a 1-day workshop to examine the current progress in understanding its etiopathophysiology and clinical care.

METHODS

The participants reviewed the current terminology of disorder and discussed advances in understanding its pathophysiology since a similar workshop was held in 2005. Clinical and research gaps were identified, and recommendations for future directions were delineated.

RESULTS

The panel unanimously agreed to adopt the term "laryngeal dystonia" instead of "spasmodic dysphonia" to reflect the current progress in characterizations of this disorder. Laryngeal dystonia was recognized as a multifactorial, phenotypically heterogeneous form of isolated dystonia. Its etiology remains unknown, whereas the pathophysiology likely involves large-scale functional and structural brain network disorganization. Current challenges include the lack of clinically validated diagnostic markers and outcome measures and the paucity of therapies that address the disorder pathophysiology.

CONCLUSION

Research priorities should be guided by challenges in clinical management of laryngeal dystonia. Identification of disorder-specific biomarkers would allow the development of novel diagnostic tools and unified measures of treatment outcome. Elucidation of the critical nodes within neural networks that cause or modulate symptoms would allow the development of targeted therapies that address the underlying pathophysiology. Given the rarity of laryngeal dystonia, future rapid research progress may be facilitated by multicenter, national and international collaborations.

Optogenetic augmentation of the hypercholinergic endophenotype in DYT1 knock-in mice induced erratic hyperactive movements but not dystonia

BACKGROUND

The most prevalent inherited form of generalized dystonia is caused by a mutation in torsinA (DYT1, ∆GAG) with incomplete penetrance. Rodent models with mutated torsinA do not develop dystonic symptoms, but previous ex vivo studies indicated abnormal excitation of cholinergic interneurons (ChI) and increased striatal acetylcholine.

METHODS

We used in vivo optogenetics to exacerbate this endophenotype in order to determine its capacity to trigger dystonic symptoms in freely behaving mice. Tor1a^+/Δgag DYT1 mice and wildtype littermates expressing channelrhodopsin2 under the Chat promotor were implanted bilaterally with optical LED cannulae and stimulated with blue light pulses of varied durations.

FINDINGS

Six months old DYT1 KI mice but not wildtype controls responded with hyperactivity to blue light specifically at 25 ms pulse duration, 10 Hz frequency. Neuronal activity (c-Fos) in cholinergic interneurons was increased immediately after light stimulation and persisted only in DYT1 KI over 15 min. Substance P was increased specifically in striosome compartments in naïve DYT1 KI mice compared to wildtype. Under optogenetic stimulation substance P increased in wildtype to match levels in Dyt1 KI, and acetylcholinesterase was elevated in the striatum of stimulated DYT1 KI. No signs of dystonic movements were observed under stimulation of up to one hour in both genotypes and age groups, and the sensorimotor deficit previously observed in 6 months old DYT1 KI mice persisted under stimulation.

INTERPRETATION

Overall this supports an endophenotype of dysregulated cholinergic activity in DYT1 dystonia, but depolarizing cholinergic interneurons was not sufficient to induce overt dystonia in DYT1 KI mice.

The effects of a relaxation program featuring aquatic therapy and autogenic training among people with cervical dystonia (a pilot study)

Classic physical interventions for cervical dystonia (CD) have focused on treating motor components or, on motor components and relaxation programs. However, no CD treatment study has focused on a relaxation program alone. We developed a pilot study to assess whether a therapy completely based on a relaxation program could improve the physical and mental symptomatologies of patients with CD. Fifteen persons were included in the experimental group, which received individual sessions of aquatic (Watsu) therapy (WT) and autogenic training (AT). In addition, 12 persons were included in passive control group. We administered different questionnaires related to quality of life (SF-36), pain (Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Visual Analog Scale (VAS)) and mood (Beck Depression Inventory (BDI-II) and State-Trait Anxiety Inventory (STAI)). A significant interaction was observed between treatment and time with regard to the SF-36, VAS, and TWSTRS within the experimental group (p < 0.01). The BDI-II showed depression decrease as a simple effect (p < 0.05), and the STAI did not change. No effects were found with regard to the control group. In this exploratory study, we found that a therapy based on whole body relaxation improved the symptoms of patients with CD. This knowledge enables a disease-management strategy that uses a holistic perspective and moves beyond the dystonic focus.

Mutant torsinA in the heterozygous DYT1 state compromises HSV propagation in infected neurons and fibroblasts

Most cases of early onset torsion dystonia (DYT1) are caused by a 3-base pair deletion in one allele of the TOR1A gene causing loss of a glutamate in torsinA, a luminal protein in the nuclear envelope. This dominantly inherited neurologic disease has reduced penetrance and no other medical manifestations. It has been challenging to understand the neuronal abnormalities as cells and mouse models which are heterozygous (Het) for the mutant allele are quite similar to wild-type (WT) controls. Here we found that patient fibroblasts and mouse neurons Het for this mutation showed significant differences from WT cells in several parameters revealed by infection with herpes simplex virus type 1 (HSV) which replicates in the nucleus and egresses out through the nuclear envelope. Using a red fluorescent protein capsid to monitor HSV infection, patient fibroblasts showed decreased viral plaque formation as compared to controls. Mouse Het neurons had a decrease in cytoplasmic, but not nuclear HSV fluorescence, and reduced numbers of capsids entering axons as compared to infected WT neurons. These findings point to altered dynamics of the nuclear envelope in cells with the patient genotype, which can provide assays to screen for therapeutic agents that can normalize these cells.

Inherited dystonias: clinical features and molecular pathways

Recent decades have witnessed dramatic increases in understanding of the genetics of dystonia - a movement disorder characterized by involuntary twisting and abnormal posture. Hampered by a lack of overt neuropathology, researchers are investigating isolated monogenic causes to pinpoint common molecular mechanisms in this heterogeneous disease. Evidence from imaging, cellular, and murine work implicates deficiencies in dopamine neurotransmission, transcriptional dysregulation, and selective vulnerability of distinct neuronal populations to disease mutations. Studies of genetic forms of dystonia are also illuminating the developmental dependence of disease symptoms that is typical of many forms of the disease. As understanding of monogenic forms of dystonia grows, a clearer picture will develop of the abnormal motor circuitry behind this relatively common phenomenology. This chapter focuses on the current data covering the etiology and epidemiology, clinical presentation, and pathogenesis of four monogenic forms of isolated dystonia: DYT-TOR1A, DYT-THAP1, DYT-GCH1, and DYT-GNAL.

Alterations of M1 and M4 acetylcholine receptors in the genetically dystonic (dtsz) hamster and moderate antidystonic efficacy of M1 and M4 anticholinergics

Striatal cholinergic dysfunction has been suggested to play a critical role in the pathophysiology of dystonia. In the dt^sz hamster, a phenotypic model of paroxysmal dystonia, M1 antagonists exerted moderate antidystonic efficacy after acute systemic administration. In the present study, we examined the effects of the M4 preferring antagonist tropicamid and whether long-term systemic or acute intrastriatal injections of the M1 preferring antagonist trihexyphenidyl are more effective in mutant hamsters. Furthermore, M1 and M4 receptors were analyzed by autoradiography and immunohistochemistry. Tropicamide retarded the onset of dystonic attacks, as previously observed after acute systemic administration of trihexyphenidyl. Combined systemic administration of trihexyphenidyl (30mg/kg) and tropicamide (15mg/kg) reduced the severity in acute trials and delayed the onset of dystonia during long-term treatment. In contrast, acute striatal microinjections of trihexyphenidyl, tropicamid or the positive allosteric M4 receptor modulator VU0152100 did not exert significant effects. Receptor analyses revealed changes of M1 receptors in the dorsomedial striatum, suggesting that the cholinergic system is involved in abnormal striatal plasticity in dt^sz hamsters, but the pharmacological data argue against a crucial role on the phenotype in this animal model. However, antidystonic effects of tropicamide after systemic administration point to a novel therapeutic potential of M4 preferring anticholinergics for the treatment of dystonia.

Heterozygous Gnal Mice Are a Novel Animal Model with Which to Study Dystonia Pathophysiology

Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions and its pathophysiological mechanisms are still poorly understood. Dominant mutations of the GNAL gene are a cause of isolated dystonia (DYT25) in patients. Some mutations result in a complete loss of function of the encoded protein, Gα_olf, an adenylyl-cyclase-stimulatory G-protein highly enriched in striatal projection neurons, where it mediates the actions of dopamine and adenosine. We used male and female heterozygous Gnal knock-out mice (Gnal^+/-) to study how GNAL haplodeficiency is implicated in dystonia. In basal conditions, no overt dystonic movements or postures or change in locomotor activity were observed. However, Gnal haploinsufficiency altered self-grooming, motor coordination, and apparent motivation in operant conditioning, as well as spine morphology and phospho-CaMKIIβ in the striatum. After systemic administration of oxotremorine, an unselective cholinergic agonist, Gnal^+/- mice developed more abnormal postures and movements than WT mice. These effects were not caused by seizures as indicated by EEG recordings. They were prevented by the M1-preferring muscarinic antagonists, telenzepine, pirenzepine, and trihexyphenidyl, which alleviate dystonic symptoms in patients. The motor defects were worsened by mecamylamine, a selective nicotinic antagonist. These oxotremorine-induced abnormalities in Gnal^+/- mice were replicated by oxotremorine infusion into the striatum, but not into the cerebellum, indicating that defects in striatal neurons favor the appearance of dystonia-like movement alterations after oxotremorine. Untreated and oxotremorine-treated Gnal^+/- mice provide a model of presymptomic and symptomatic stages of DYT25-associated dystonia, respectively, and clues about the mechanisms underlying dystonia pathogenesis.SIGNIFICANCE STATEMENT Adult-onset dystonia DYT25 is caused by dominant loss-of-function mutations of GNAL, a gene encoding the stimulatory G-protein Gαolf, which is critical for activation of the cAMP pathway in the striatal projection neurons. Here, we demonstrate that Gnal-haplodeficient mice have a mild neurological phenotype and display vulnerability to developing dystonic movements after systemic or intrastriatal injection of the cholinergic agonist oxotremorine. Therefore, impairment of the cAMP pathway in association with an increased cholinergic tone creates alterations in striatal neuron functions that can promote the onset of dystonia. Our results also provide evidence that untreated and oxotremorine-treated Gnal-haplodeficient mice are powerful models with which to study presymptomic and symptomatic stages of DYT25-associated dystonia, respectively.

Cortical sensorimotor alterations classify clinical phenotype and putative genotype of spasmodic dysphonia

BACKGROUND AND PURPOSE

Spasmodic dysphonia (SD), or laryngeal dystonia, is a task-specific isolated focal dystonia of unknown causes and pathophysiology. Although functional and structural abnormalities have been described in this disorder, the influence of its different clinical phenotypes and genotypes remains scant, making it difficult to explain SD pathophysiology and to identify potential biomarkers.

METHODS

We used a combination of independent component analysis and linear discriminant analysis of resting-state functional magnetic resonance imaging data to investigate brain organization in different SD phenotypes (abductor versus adductor type) and putative genotypes (familial versus sporadic cases) and to characterize neural markers for genotype/phenotype categorization.

RESULTS

We found abnormal functional connectivity within sensorimotor and frontoparietal networks in patients with SD compared with healthy individuals as well as phenotype- and genotype-distinct alterations of these networks, involving primary somatosensory, premotor and parietal cortices. The linear discriminant analysis achieved 71% accuracy classifying SD and healthy individuals using connectivity measures in the left inferior parietal and sensorimotor cortices. When categorizing between different forms of SD, the combination of measures from the left inferior parietal, premotor and right sensorimotor cortices achieved 81% discriminatory power between familial and sporadic SD cases, whereas the combination of measures from the right superior parietal, primary somatosensory and premotor cortices led to 71% accuracy in the classification of adductor and abductor SD forms.

CONCLUSIONS

Our findings present the first effort to identify and categorize isolated focal dystonia based on its brain functional connectivity profile, which may have a potential impact on the future development of biomarkers for this rare disorder.

GNAL mutation in isolated laryngeal dystonia

BACKGROUND

Up to 12% of patients with laryngeal dystonia report a familial history of dystonia, pointing to involvement of genetic factors. However, its genetic causes remain unknown.

METHOD

Using Sanger sequencing, we screened 57 patients with isolated laryngeal dystonia for mutations in known dystonia genes TOR1A (DYT1), THAP1 (DYT6), TUBB4A (DYT4), and GNAL (DYT25). Using functional MRI, we explored the influence of the identified mutation on brain activation during symptomatic task production.

RESULTS

We identified 1 patient with laryngeal dystonia who was a GNAL mutation carrier. When compared with 26 patients without known mutations, the GNAL carrier had increased activity in the fronto-parietal cortex and decreased activity in the cerebellum.

CONCLUSIONS

Our data show that GNAL mutation may represent one of the rare causative genetic factors of isolated laryngeal dystonia. Exploratory evidence of distinct neural abnormalities in the GNAL carrier may suggest the presence of divergent pathophysiological cascades underlying this disorder. © 2016 International Parkinson and Movement Disorder Society.

Screening of GNAL variants in Brazilian patients with isolated dystonia reveals a novel mutation with partial loss of function

GNAL was identified as a cause of dystonia in patients from North America, Europe and Asia. In this study, we aimed to investigate the prevalence of GNAL variants in Brazilian patients with dystonia. Ninety-one patients with isolated idiopathic dystonia, negative for THAP1 and TOR1A mutations, were screened for GNAL variants by Sanger sequencing. Functional characterization of the Gαolf protein variant was performed using the bioluminescence resonance energy transfer assay. A novel heterozygous nonsynonymous variant (p. F133L) was identified in a patient with cervical and laryngeal dystonia since the third decade of life, with no family history. This variant was not identified in healthy Brazilian controls and was not described in 63,000 exomas of the ExAC database. The F133L mutant exhibited significantly elevated levels of basal BRET and severely diminished amplitude of response elicited by dopamine, that both indicate substantial functional impairment of Gαolf in transducing receptor signals, which could be involved in dystonia pathophysiology. GNAL mutations are not a common cause of dystonia in the Brazilian population and have a lower prevalence than THAP1 and TOR1A mutations. We present a novel variant that results in partial Gαolf loss of function.

Dystonia and Paroxysmal Dyskinesias: Under-Recognized Movement Disorders in Domestic Animals? A Comparison with Human Dystonia/Paroxysmal Dyskinesias

Dystonia is defined as a neurological syndrome characterized by involuntary sustained or intermittent muscle contractions causing twisting, often repetitive movements, and postures. Paroxysmal dyskinesias are episodic movement disorders encompassing dystonia, chorea, athetosis, and ballism in conscious individuals. Several decades of research have enhanced the understanding of the etiology of human dystonia and dyskinesias that are associated with dystonia, but the pathophysiology remains largely unknown. The spontaneous occurrence of hereditary dystonia and paroxysmal dyskinesia is well documented in rodents used as animal models in basic dystonia research. Several hyperkinetic movement disorders, described in dogs, horses and cattle, show similarities to these human movement disorders. Although dystonia is regarded as the third most common movement disorder in humans, it is often misdiagnosed because of the heterogeneity of etiology and clinical presentation. Since these conditions are poorly known in veterinary practice, their prevalence may be underestimated in veterinary medicine. In order to attract attention to these movement disorders, i.e., dystonia and paroxysmal dyskinesias associated with dystonia, and to enhance interest in translational research, this review gives a brief overview of the current literature regarding dystonia/paroxysmal dyskinesia in humans and summarizes similar hereditary movement disorders reported in domestic animals.

Rapid genotyping of animals followed by establishing primary cultures of brain neurons

High-resolution analysis of the morphology and function of mammalian neurons often requires the genotyping of individual animals followed by the analysis of primary cultures of neurons. We describe a set of procedures for: labeling newborn mice to be genotyped, rapid genotyping, and establishing low-density cultures of brain neurons from these mice. Individual mice are labeled by tattooing, which allows for long-term identification lasting into adulthood. Genotyping by the described protocol is fast and efficient, and allows for automated extraction of nucleic acid with good reliability. This is useful under circumstances where sufficient time for conventional genotyping is not available, e.g., in mice that suffer from neonatal lethality. Primary neuronal cultures are generated at low density, which enables imaging experiments at high spatial resolution. This culture method requires the preparation of glial feeder layers prior to neuronal plating. The protocol is applied in its entirety to a mouse model of the movement disorder DYT1 dystonia (ΔE-torsinA knock-in mice), and neuronal cultures are prepared from the hippocampus, cerebral cortex and striatum of these mice. This protocol can be applied to mice with other genetic mutations, as well as to animals of other species. Furthermore, individual components of the protocol can be used for isolated sub-projects. Thus this protocol will have wide applications, not only in neuroscience but also in other fields of biological and medical sciences.

Neuropathological features of genetically confirmed DYT1 dystonia: investigating disease-specific inclusions

Introduction

Early onset isolated dystonia (DYT1) is linked to a three base pair deletion (ΔGAG) mutation in the TOR1A gene. Clinical manifestation includes intermittent muscle contraction leading to twisting movements or abnormal postures. Neuropathological studies on DYT1 cases are limited, most showing no significant abnormalities. In one study, brainstem intraneuronal inclusions immunoreactive for ubiquitin, torsinA and lamin A/C were described. Using the largest series reported to date comprising 7 DYT1 cases, we aimed to identify consistent neuropathological features in the disease and determine whether we would find the same intraneuronal inclusions as previously reported.

Result

The pathological changes of brainstem inclusions reported in DYT1 dystonia were not replicated in our case series. Other anatomical regions implicated in dystonia showed no disease-specific pathological intracellular inclusions or evidence of more than mild neuronal loss.

Conclusion

Our findings suggest that the intracellular inclusions described previously in DYT1 dystonia may not be a hallmark feature of the disorder. In isolated dystonia, DYT1 in particular, biochemical changes may be more relevant than the morphological changes.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0159-x) contains supplementary material, which is available to authorized users.

TOR1A polymorphisms in a Russian cohort with primary focal/segmental dystonia

PURPOSE/AIM OF THE STUDY

To analyze contribution of rs3842225 and rs1182 single nucleotide polymorphisms (SNP) in TOR1A gene, the causative gene for the DYT1 form of hereditary early-onset generalized dystonia, to the development of focal and segmental dystonia in Russian patients.

MATERIALS AND METHODS

We analyzed associations between rs3842225 and rs1182 polymorphisms in TOR1A and focal/segmental dystonia in 254 patients from Russian population, including 218 Slavic patients and 36 patients of mixed ethnic background.

RESULTS

Stratification of patients based on age at the disease onset (≤ 30 years and > 30 years) showed statistically significant prevalence of the del-allele at the rs3842225 locus in Slavic patients with earlier age of onset of dystonia (36.96% vs. 21.39% in patients with late age of onset, p = 0.002) and an overrepresentation of the T-allele at the rs1182 locus (36.96% vs. 21.69%, p = 0.003). In Slavs, we also observed an overrepresentation of the homozygous genotypes, T/T (general sample of dystonia, 9.17% and focal dystonia, 10.28%) or G/G (general sample of dystonia, 60.55% and focal dystonia, 58.86%), compared to controls (T/T, 4.27% and G/G, 55.49%). In non-Slavic patients, we revealed neither significant associations, nor statistical tendencies regarding any of the clinical features.

CONCLUSIONS

Our data in an Eastern Slavic (Russian) population correspond well to results of other studies from different countries and confirm that certain TOR1A genotypes may be regarded as factors predisposing to focal and segmental dystonia.

Genetic animal models of dystonia: common features and diversities

Animal models are pivotal for studies of pathogenesis and treatment of disorders of the central nervous system which in its complexity cannot yet be modeled in vitro or using computer simulations. The choice of a specific model to test novel therapeutic strategies for a human disease should be based on validity of the model for the approach: does the model reflect symptoms, pathogenesis and treatment response present in human patients? In the movement disorder dystonia, prior to the availability of genetically engineered mice, spontaneous mutants were chosen based on expression of dystonic features, including abnormal muscle contraction, movements and postures. Recent discovery of a number of genes and gene products involved in dystonia initiated research on pathogenesis of the disorder, and the creation of novel models based on gene mutations. Here we present a review of current models of dystonia, with a focus on genetic rodent models, which will likely be first choice in the future either for pathophysiological or for preclinical drug testing or both. In order to help selection of a model depending on expression of a specific feature of dystonia, this review is organized by symptoms and current knowledge of pathogenesis of dystonia. We conclude that albeit there is increasing need for research on pathogenesis of the disease and development of improved models, current models do replicate features of dystonia and are useful tools to develop urgently demanded treatment for this debilitating disorder.

Genetics in dystonia: an update

The past year has been extremely successful with regard to the genetics of dystonia, with the identification of four new dystonia genes (CIZ1, ANO3, GNAL, and TUBB4A). This progress was primarily achieved because of the application of a new technology, next-generation DNA sequencing, which allows rapid and comprehensive assessment of a patient's genome. In addition, a combination of next-generation and traditional Sanger sequencing has expanded the phenotypic spectrum associated with some of the dystonia plus (ATP1A3) and paroxysmal (PRRT2) loci. This article reviews the newly identified genes and phenotypes and discusses the future applications of next-generation sequencing to dystonia research.

Treatment of dystonia

Selecting the appropriate treatment for dystonia begins with proper classification of disease based on age, distribution, and underlying etiology. The therapies available for dystonia include oral medications, botulinum toxin, and surgical procedures. Oral medications are generally reserved for generalized and segmental dystonia. Botulinum toxin revolutionized the treatment of focal dystonia when it was introduced for therapeutic purposes in the 1980s. Surgical procedures are available for medication-refractory dystonia, markedly affecting an individual's quality of life.

Descriptive epidemiology of cervical dystonia

Background

Cervical dystonia (CD), the most common form of adult-onset focal dystonia, has a heterogeneous clinical presentation with variable clinical features, leading to difficulties and delays in diagnosis. Owing to the lack of reviews specifically focusing on the frequency of primary CD in the general population, we performed a systematic literature search to examine its prevalence/incidence and analyze methodological differences among studies.

Methods

We performed a systematic literature search to examine the prevalence data of primary focal CD. Sixteen articles met our methodological criteria. Because the reported prevalence estimates were found to vary widely across studies, we analyzed methodological differences and other factors to determine whether true differences exist in prevalence rates among geographic areas (and by gender and age distributions), as well as to facilitate recommendations for future studies.

Results

Prevalence estimates ranged from 20–4,100 cases/million. Generally, studies that relied on service-based and record-linkage system data likely underestimated the prevalence of CD, whereas population-based studies suffered from over-ascertainment. The more methodologically robust studies yielded a range of estimates of 28–183 cases/million. Despite the varying prevalence estimates, an approximate 2:1 female:male ratio was consistent among many studies. Three studies estimated incidence, ranging from 8–12 cases/million person-years.

Discussion

Although several studies have attempted to estimate the prevalence and incidence of CD, there is a need for additional well-designed epidemiological studies on primary CD that include large populations; use defined CD diagnostic criteria; and stratify for factors such as age, gender, and ethnicity.

New genetic insights highlight 'old' ideas on motor dysfunction in dystonia

Primary dystonia is a poorly understood but common movement disorder. Recently, several new primary dystonia genes were identified that provide new insight into dystonia pathogenesis. The GNAL dystonia gene is central for striatal responses to dopamine (DA) and is a component of a molecular pathway already implicated in DOPA-responsive dystonia (DRD). Furthermore, this pathway is also dysfunctional and pathogenically linked to mTOR signaling in L-DOPA-induced dyskinesias (LID). These new data suggest that striatal DA responses are central to primary dystonia, even when symptoms do not benefit from DA therapies. Here we integrate these new findings with current understanding of striatal microcircuitry and other dystonia-causing insults to develop new ideas on the pathophysiology of this incapacitating movement disorder.

Thalamic post-inhibitory bursting occurs in patients with organic dystonia more often than controls

We now test the hypothesis that post-inhibitory bursting in the human pallidal receiving nucleus of the thalamus (ventral oral) mediates inhibitory pallido-thalamic transmission during dystonia. We have compared thalamic single neuron activity in nine patients with organic dystonia to that in a patient with psychogenic dystonia (Psyd) and in healthy waking monkeys. In organic dystonia, EMG power is commonly concentrated at the lowest frequency of the smoothed autopower spectrum (0.39Hz). Therefore, segments of spike trains with a signal-to-noise ratio ≥2 at 0.39Hz were termed dystonia frequency (DF) segments, which occurred more commonly during dystonia related to movement. Those with a SNR<2 were termed non-dystonia frequency (nDF) segments, which were associated with spontaneous dystonia. We concentrated on nDF activity since neuronal activity in our controls was measured at rest. Neuronal spike trains were categorized into those with post-inhibitory bursts (G, grouped), with single spikes (NG, non-grouped), or with both single spikes and bursts (I, intermediate). nDF spike trains in ventral oral had more G category firing in dystonia than in controls. The burst rate and the pre-burst silent period in nDF firing of organic dystonia were consistently greater than those of both the monkeys and the patient with Psyd. The distribution of the pre-burst silent period was bimodal with a longer mode of approximately GABAb (gamma amino butyric acid receptor-type b) duration. These results demonstrate distinct differences of post-inhibitory bursting in organic dystonia versus controls. The presence of inhibitory events consistent with GABAb duration suggests interventions for treatment of dystonia.

Mutations in the autoregulatory domain of β-tubulin 4a cause hereditary dystonia

Dystonia type 4 (DYT4) was first described in a large family from Heacham in Norfolk with an autosomal dominantly inherited whispering dysphonia, generalized dystonia, and a characteristic hobby horse ataxic gait. We carried out a genetic linkage analysis in the extended DYT4 family that spanned 7 generations from England and Australia, revealing a single LOD score peak of 6.33 on chromosome 19p13.12-13. Exome sequencing in 2 cousins identified a single cosegregating mutation (p.R2G) in the β-tubulin 4a (TUBB4a) gene that was absent in a large number of controls. The mutation is highly conserved in the β-tubulin autoregulatory MREI (methionine-arginine-glutamic acid-isoleucine) domain, highly expressed in the central nervous system, and extensive in vitro work has previously demonstrated that substitutions at residue 2, specifically R2G, disrupt the autoregulatory capability of the wild-type β-tubulin peptide, affirming the role of the cytoskeleton in dystonia pathogenesis.

Mutations in GNAL cause primary torsion dystonia

Dystonia is a movement disorder characterized by repetitive twisting muscle contractions and postures^1,2. Its molecular pathophysiology is poorly understood, in part due to limited knowledge of the genetic basis of the disorder. Only three genes for primary torsion dystonia (PTD), TOR1A (DYT1)³, THAP1 (DYT6)⁴, and CIZ1⁵ have been identified. Using exome sequencing in two PTD families we identified a novel causative gene, GNAL, with a nonsense p.S293X mutation resulting in premature stop codon in one family and a missense p.V137M mutation in the other. Screening of GNAL in 39 PTD families, revealed six additional novel mutations in this gene. Impaired function of several of the mutations was shown by bioluminescence resonance energy transfer (BRET) assays.

Respiratory disorders associated with dystonia

BACKGROUND

Respiratory difficulties are sometimes reported by patients with cranial-cervical and other forms of dystonia, but the nature or mechanisms of the breathing problems have not been well characterized.

CASE REPORT

We review 13 dystonic patients with various respiratory complaints and describe their symptoms and response to treatment, including botulinum toxin (BoNT) injections.

DISCUSSION

Gasping, stridor, interrupted flow of speech, paradoxical breathing, dyspnea on exertion, and other respiratory symptoms reported by patients suggest involvement of the upper airways, chest, and diaphragm. BoNT injections may be, at least partially, beneficial in some patients.

CONCLUSION

This series of patients draws attention to respiratory distress as a potentially serious, even life-threatening, complication of dystonia.

Association of rs1182 polymorphism of the DYT1 gene with primary dystonia in Chinese population

BACKGROUND

The deletion mutation of glutamate codon (GAG) in the TOR1A gene is a major cause of primary generalized dystonia. Recent genetic studies suggest that the rs1182 polymorphism in the same gene may represent a risk factor for primary dystonia. However, this finding has been inconsistent. Furthermore, no data on such an association in a Chinese population have been published.

METHODS

A total of 291 patients with primary dystonia from the Department of Neurology, West China Hospital of Sichuan University were included. From the same region, 294 healthy individuals were recruited as a control group. The SNP was identified by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

In the present study, focal dystonia was the most common presented form. No difference was found in the genotype frequency, minor allele frequencies, and "G" allele frequency between all dystonia patients and controls. No difference was found either, between early- and late-onset dystonia patients, patients with and without a positive family history, patients with pain and without pain, and patients with and without sensory trick. Moreover, no significant differences in the genotype and allele frequencies were found among different dystonia subtypes.

CONCLUSION

No association of the rs1182 of TOR1A with Chinese primary dystonia was found. More studies on such an association involving a larger number of participants, especially from Asian populations, are needed to confirm the present findings.

Posttraumatic focal dystonia of the shoulder

Focal posttraumatic shoulder dystonia is a rare and not easily identifiable entity. Its true pathophysiologic nature, predisposing factors, and disease course remain debatable.This article describes a rare case of a 40-year-old man with late symptoms of focal shoulder dystonia after peripheral trauma of his left shoulder girdle. The shoulder was indirectly injured from the impact of a fall off his motorbike 3 years earlier. He was referred to the authors' institution because remarkable reduction of arm abduction, muscle spasms, and circumscribed hypertrophy of the trapezius muscle were noted while his head and neck were in neutral position and had a full range of motion. The left shoulder had a fixed elevated posture compared with the contralateral shoulder. A continuous burning pain was localized over the area of the hypertrophied trapezius muscle, radiating to the ipsilateral side of the head and neck. Dystonic movements of the trapezius, rhomboid, and supraspinatus muscles were observed. The abduction of the shoulder was significantly decreased, and any repetitive effort for arm abduction induced an exaggeration of his movement disorder, leading to a more pronounced shoulder elevation.Plain radiographs and magnetic resonance imaging of the left shoulder revealed a suprascapular tendinitis with no other abnormalities. Repeated needle electromyography of the left trapezius muscle and neurography of the accessory nerve on both sides were normal. Injections of botulinum toxin A were effective in the resolution of muscle hypertrophy and abnormal posture.

The use of next-generation sequencing in movement disorders

New advances in genomic technology are being introduced at a greater speed and are revolutionizing the field of genetics for both complex and Mendelian diseases. For instance, during the past few years, genome-wide association studies (GWAS) have identified a large number of significant associations between genomic loci and movement disorders such as Parkinson's disease and progressive supranuclear palsy. GWAS are carried out through the use of high-throughput SNP genotyping arrays, which are also used to perform linkage analyses in families previously considered statistically underpowered for genetic analyses. In inherited movement disorders, using this latter technology, it has repeatedly been shown that mutations in a single gene can lead to different phenotypes, while the same clinical entity can be caused by mutations in different genes. This is being highlighted with the use of next-generation sequencing technologies and leads to the search for genes or genetic modifiers that contribute to the phenotypic expression of movement disorders. Establishing an accurate genome-epigenome-phenotype relationship is becoming a major challenge in the post-genomic research that should be facilitated through the implementation of both functional and cellular analyses.

Secondary dystonia in a botulinum toxin clinic: clinical characteristics, neuroanatomical substrate and comparison with idiopathic dystonia

The analysis of patients with secondary dystonia has been valuable to explore the anatomical, pharmacological and physiological bases of this disorder. The goal of this study is to compare the clinical characteristics of patients with primary and secondary dystonia and analyze the neuroanatomical bases of a subgroup of patients with lesion-induced dystonia. We identified patients evaluated in our Botulinum Toxin Clinic from 1/2000 to 7/2009 with an ICD code for "dystonia". Medical records of all subjects were reviewed, recording demographic, clinical, therapeutic and neuroimaging data. A total of 230 patients were included in the study. Idiopathic/primary dystonia was diagnosed in 162 and secondary dystonia in 58, while in 10 the etiology was uncertain. We found a female predominance (2.4:1 and 1.9:1 for primary and secondary dystonia, respectively). The cervical region was most commonly affected in primary dystonia and the limbs in secondary cases. The age at presentation was higher in primary (54.4 ± 14.1) than secondary (49 ± 17.9) dystonia. Among patients with secondary dystonia, a focal lesion was the presumed etiology in 32, with localizing diagnostic studies available in 16. The most common lesions were strokes involving the corticospinal pathway. All of those patients exhibited limb dystonia, except one with cervical dystonia following a thalamic infarct. In conclusion, primary and secondary dystonias are more prevalent in women, suggesting a sex-related predisposition to the development of this movement disorder. Lesion-induced dystonia most frequently involves the limbs and is caused by lesions in the cerebral cortex and subcortical white matter.