The Broadening Application of Chemodenervation in X-Linked Dystonia-Parkinsonism (Part I): Muscle Afferent Block Versus Botulinum Toxin-A in Cervical and Limb Dystonias

A scoping review on the diagnosis and treatment of X-linked dystonia-parkinsonism

INTRODUCTION

X-linked dystonia-parkinsonism (XDP) is a progressive neurodegenerative disorder that has been studied well in recent years.

OBJECTIVES

This scoping review aimed to describe the current state of knowledge about the diagnosis and treatment of XDP, to provide clinicians with a concise and up-to-date overview.

METHODS

We conducted a scoping review of pertinent literature on the diagnosis and treatment of XDP using Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines.

RESULTS

There were 24 articles on diagnostic methods and 20 articles on therapeutic interventions for XDP, with 7 review articles describing both. The detection of the SVA retrotransposon insertion within the TAF1 gene is confirmatory for XDP. Oral medications are marginally effective. Chemodenervation with botulinum toxin is an effective treatment. Pallidal deep brain stimulation (DBS) has been shown to provide significant improvement in the dystonia and quality of life of patients with XDP for a longer time. A less invasive surgical option is the transcranial magnetic resonance-guided focused ultrasound (tcMRgFUS), which has shown promising effects with the limited number of case reports available.

CONCLUSION

XDP is a geneti disorder characterized by striatal symptoms and pathology on neuroimaging. No effective oral medications are available for the management of XDP. The use of botulinum toxin is limited by its cost and duration of effects. As of now, pallidal DBS is deemed to be the best option. Another promising option is the tcMRgFUS but still has limited studies on its safety and efficacy in XDP.

Nine Hereditary Movement Disorders First Described in Asia: Their History and Evolution

Clinical case studies and reporting are important to the discovery of new disorders and the advancement of medical sciences. Both clinicians and basic scientists play equally important roles leading to treatment discoveries for both cures and symptoms. In the field of movement disorders, exceptional observation of patients from clinicians is imperative, not just for phenomenology but also for the variable occurrences of these disorders, along with other signs and symptoms, throughout the day and the disease course. The Movement Disorders in Asia Task Force (TF) was formed to help enhance and promote collaboration and research on movement disorders within the region. As a start, the TF has reviewed the original studies of the movement disorders that were preliminarily described in the region. These include nine disorders that were first described in Asia: Segawa disease, PARK-Parkin, X-linked dystonia-parkinsonism, dentatorubral-pallidoluysian atrophy, Woodhouse-Sakati syndrome, benign adult familial myoclonic epilepsy, Kufor-Rakeb disease, tremulous dystonia associated with mutation of the calmodulin-binding transcription activator 2 gene, and paroxysmal kinesigenic dyskinesia. We hope that the information provided will honor the original researchers and help us learn and understand how earlier neurologists and basic scientists together discovered new disorders and made advances in the field, which impact us all to this day.

Dystonias: Clinical Recognition and the Role of Additional Diagnostic Testing

Dystonia is the third most common movement disorder, characterized by abnormal, frequently twisting postures related to co-contraction of agonist and antagonist muscles. Diagnosis is challenging. We provide a comprehensive appraisal of the epidemiology and an approach to the phenomenology and classification of dystonia, based on the clinical characteristics and underlying etiology of dystonia syndromes. We discuss the features of common idiopathic and genetic forms of dystonia, diagnostic challenges, and dystonia mimics. Appropriate workup is based on the age of symptom onset, rate of progression, whether dystonia is isolated or combined with another movement disorder or complex neurological and other organ system eatures. Based on these features, we discuss when imaging and genetic should be considered. We discuss the multidisciplinary treatment of dystonia, including rehabilitation and treatment principles according to the etiology, including when pathogenesis-direct treatment is available, oral pharmacological therapy, chemodenervation with botulinum toxin injections, deep brain stimulation and other surgical therapies, and future directions.

X-linked dystonia parkinsonism: epidemiology, genetics, clinical features, diagnosis, and treatment

X-linked dystonia parkinsonism (XDP) is a rare X-linked recessive degenerative movement disorder that only affects Filipino descent, predominantly males. Its underlying cause is associated with the genetic alterations in the TAF1/DYT3 multiple transcription system. SINE-VNTR-Alu (SVA) retrotransposon insertion was suggested to be the responsible genetic mutation. Clinically, it initially presents as focal dystonia and generalizes within years. Parkinsonism arises years later and coexists with dystonia. Nonmotor symptoms like cognitive impairment and mood disorders are also common among XDP patients. XDP diagnosis relies on clinical history and physical examination. On imaging, abnormalities of the striatum, such as atrophy, are widely seen and can explain the clinical presentations with a three-model pathway of the striatum. Treatments aim for symptomatic relief of dystonia and parkinsonism and to prevent complications. Oral medications, chemo-denervation, and surgery are used in XDP patients. This review summarizes the currently important information regarding XDP, providing a synoptic overview and understanding of XDP for future studies.

[Therapeutic strategies for oromandibular dystonia]

Oromandibular dystonia is characterized by tonic or clonic involuntary spasms of the masticatory, lingual and / or muscles in the stomatognathic system. It is often misdiagnosed as craniomandibular dysfunction or psychiatric disease. According to clinical features, the oromandibular dystonia is classified into 6 subtypes (jaw closing-, jaw opening-, tongue-, jaw deviation-, jaw protrusion-, and lip dystonia). There are several treatment methods like botulinum toxin injection, muscle afferent block (injection of lidocaine and alcohol into the masticatory or tongue muscles for blocking muscle afferents from muscle spindle), occlusal splint, and oral surgery (coronoidotomy). Most of patients can be treated successfully according to subtype by combination of these treatments. Special treatment recommendations for each subtype were described in this focus article. Accurate diagnosis and treatment of oral dystonia requires comprehensive knowledge and skills of both oral and maxillofacial surgery and neurology. Therefore, collaboration among these departments is very important.

Neuroimaging and neuropathology studies of X-linked dystonia parkinsonism

X-linked Dystonia Parkinsonism (XDP) is a recessive, genetically inherited neurodegenerative disorder endemic to Panay Island in the Philippines. Clinical symptoms include the initial appearance of dystonia, followed by parkinsonian traits after 10-15 years. The basal ganglia, particularly the striatum, is an area of focus in XDP neuropathology research, as the striatum shows marked atrophy that correlates with disease progression. Thus, XDP shares features of Parkinson's disease symptomatology, in addition to the genetic predisposition and presence of striatal atrophy resembling Huntington's disease. However, further research is required to reveal the detailed pathology and indicators of disease in the XDP brain. First, there are limited neuropathological studies that have investigated neuronal changes and neuroinflammation in the XDP brain. However, multiple neuroimaging studies on XDP patients provide clues to other affected brain regions. Furthermore, molecular pathological studies have elucidated that the main genetic cause of XDP is in the TAF-1 gene, but how this mutation relates to XDP neuropathology still remains to be fully investigated. Hence, we aim to provide an extensive overview of the current literature describing neuropathological changes within the XDP brain, and discuss future research avenues, which will provide a better understanding of XDP neuropathogenesis.

X-Linked Dystonia-Parkinsonism: recent advances

PURPOSE OF REVIEW

Our understanding of X-Linked Dystonia-Parkinsonism (XDP) has advanced considerably in recent years because of a wealth of new data describing its genetic basis, cellular phenotypes, neuroimaging features, and response to deep brain stimulation (DBS). This review provides a concise summary of these studies.

RECENT FINDINGS

XDP is associated with a SINE-VNTR-Alu (SVA)-type retrotransposon insertion within the TAF1 gene. This element includes a hexameric DNA repeat expansion, (CCCTCT)n, the length of which varies among patients and is inversely correlated to age of disease onset. In cell models, the SVA alters TAF1 splicing and reduces levels of full-length transcript. Neuroimaging data have confirmed previous neuropathology studies that XDP involves a progressive striatal atrophy, while further detecting functional alterations in additional brain regions. In patients exhibiting features of both dystonia and parkinsonism, pallidal DBS has resulted in rapid improvement of hyperkinetic movements, but effects on hypokinetic features have been inconsistent.

SUMMARY

The discovery that XDP is linked to a polymorphic hexameric sequence suggests that it could share mechanisms with other DNA repeat disorders, whereas the transcriptional defect in cell models raises the possibility that strategies to correct TAF1 splicing could provide therapeutic benefit.

Clinicopathological Phenotype and Genetics of X-Linked Dystonia-Parkinsonism (XDP; DYT3; Lubag)

X-linked dystonia–parkinsonism (XDP; OMIM314250), also referred to as DYT3 dystonia or “Lubag” disease, was first described as an endemic disease in the Philippine island of Panay. XDP is an adult-onset movement disorder characterized by progressive and severe dystonia followed by overt parkinsonism in the later years of life. Among the primary monogenic dystonias, XDP has been identified as a transcriptional dysregulation syndrome with impaired expression of the TAF1 (TATA box-binding protein associated factor 1) gene, which is a critical component of the cellular transcription machinery. The major neuropathology of XDP is progressive neuronal loss in the neostriatum (i.e., the caudate nucleus and putamen). XDP may be used as a human disease model to elucidate the pathomechanisms by which striatal neurodegeneration leads to dystonia symptoms. In this article, we introduce recent advances in the understanding of the interplay between pathophysiology and genetics in XDP.