Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias.

Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.

Paroxysmal Dyskinesias.

Paroxysmal dyskinesias (PD) are hyperkinetic movement disorders where patients usually retain consciousness. Paroxysmal dyskinesias can be kinesigenic (PKD), nonkinesigenic (PNKD), and exercise induced (PED). These are usually differentiated from each other based on their phenotypic and genotypic characteristics. Genetic causes of PD are continuing to be discovered. Genes found to be involved in the pathogenesis of PD include MR-1, PRRT2, SLC2A1, and KCNMA1. The differential diagnosis is broad as PDs can mimic psychogenic events, seizure, or other movement disorders. This review also includes secondary causes of PDs, which can range from infections, metabolic, structural malformations to malignancies. Treatment is usually based on the correct identification of type of PD. PKD responds well to antiepileptic medications, whereas PNKD and PED respond to avoidance of triggers and exercise, respectively. In this article, we review the classification, clinical features, genetics, differential diagnosis, and management of PD.

Classification of involuntary movements in dogs: Paroxysmal dyskinesias.

Paroxysmal dyskinesias (PDs) are a group of hyperkinetic movement disorders characterised by circumscribed episodes of disturbed movement, superimposed on a background state in which such abnormality is absent. There is no loss of consciousness. Episodes can last seconds, minutes or hours, and the beginning and end of the movement disturbance are abrupt. Neurological examination is typically normal between episodes. PDs are associated with a broad spectrum of clinical presentations, encompassing various aetiologies. In humans, three main groups of PDs are distinguished, based on precipitating events rather than phenomenology: (1) paroxysmal kinesigenic dyskinesia (PKD); (2) paroxysmal nonkinesigenic dyskinesia (PNKD); and (3) paroxysmal exertion-induced dyskinesia (PED). In recent years, there has been an expansion of the spectrum of manifestations of PD due to the identification of genes associated with PD in humans (PRRT1, MR-1, SLC2A1 and KCNMA1) and dogs (BCAN and PIGN). The precise pathophysiological mechanism underlying the clinical manifestations of these reported mutations remains to be elucidated. Progress is also being made in the field of immunology, and links to gluten hypersensitivity in Border terriers with so-called canine epileptoid cramping syndrome (CECS) have been reported. This review aims to synthesise a classification scheme for veterinary PDs by reviewing human systems and applying them to veterinary examples. However, it is anticipated that genetic advancement will greatly aid in future stratification and therapy for PDs in dogs. Therefore, classification systems should be viewed as works in progress that should be modified as necessary.

Paroxysmal movement disorders: An update.

Paroxysmal movement disorders comprise both paroxysmal dyskinesia, characterized by attacks of dystonic and/or choreic movements, and episodic ataxia, defined by attacks of cerebellar ataxia. They may be primary (familial or sporadic) or secondary to an underlying cause. They can be classified according to their phenomenology (kinesigenic, non-kinesigenic or exercise-induced) or their genetic cause. The main genes involved in primary paroxysmal movement disorders include PRRT2, PNKD, SLC2A1, ATP1A3, GCH1, PARK2, ADCY5, CACNA1A and KCNA1. Many cases remain genetically undiagnosed, thereby suggesting that additional culprit genes remain to be discovered. The present report is a general overview that aims to help clinicians diagnose and treat patients with paroxysmal movement disorders.

The genetics of the dystonias--a review based on the new classification of the dystonias.

The definition and classification of the dystonias was recently revisited. In the new 2013 classification, the dystonias are subdivided in terms of their etiology according to whether they are the result of pathological changes or structural damage, have acquired causes or are inherited. As hereditary dystonias are clinically and genetically heterogeneous, we sought to classify them according to the new recently defined criteria. We observed that although the new classification is still the subject of much debate and controversy, it is easy to use in a logical and objective manner with the inherited dystonias. With the discovery of new genes, however, it remains to be seen whether the new classification will continue to be effective.

The genetics of the dystonias – a review based on the new classification of the dystonias / A genética das distonias – uma revisão baseada na nova classificação das distonias

The definition and classification of the dystonias was recently revisited. In the new 2013 classification, the dystonias are subdivided in terms of their etiology according to whether they are the result of pathological changes or structural damage, have acquired causes or are inherited. As hereditary dystonias are clinically and genetically heterogeneous, we sought to classify them according to the new recently defined criteria. We observed that although the new classification is still the subject of much debate and controversy, it is easy to use in a logical and objective manner with the inherited dystonias. With the discovery of new genes, however, it remains to be seen whether the new classification will continue to be effective.

O conceito e a classificação das distonias foram recentemente revisados. Na nova classificação de 2013, quanto à etiologia, as distonias podem ser subdividas em relação às alterações patológicas, aos danos estruturais, às causas adquiridas e à hereditariedade. Como as distonias hereditárias são clínica e geneticamente heterogêneas, buscamos classifica-las segundo os novos critérios estabelecidos recentemente. Observamos que apesar da nova classificação das distonias ainda ser objeto de discussões e controvérsias, ela pode usada com facilidade, de uma maneira lógica e objetiva, no contexto das distonias hereditárias. Com a descoberta de novos genes poderemos observar se essa classificação continuará sendo efetiva.

Discinesia paroxística cinesigénica familiar: descripción de una familia / Familial paroxysmal kinesigenic dyskinesia. A case description

Las discinesias paroxísticas son trastornos del movimiento caracterizadas por episodios repentinos de movimientos involuntarios. Se dividen en cinesigénicas, no cinesigénicas e inducidas por el ejercicio. Los autores enfatizan la importancia de la historia clínica y de la descripción de los episodios en el diagnóstico diferencial. Adolescente de 12 años con episodios de torsión de la lengua y posturas distónicas de las extremidades superiores desencadenados por movimientos súbitos como empezar a correr o bajar escaleras y al comienzo del ejercicio, cesando espontáneamente segundos después. Algunos episodios eran desencadenados por el estrés. En la historia familiar, el padre, tío paterno y hermana también presentaban episodios paroxísticos. El examen neurológico intercrítico fue normal. Se identificó una mutación en el gen PRRT2 asociado con trastornos neurológicos como discinesia paroxística cinesigénica, convulsiones infantiles con coreoatetosis, migraña, ataxia episódica, tortícolis paroxística y retraso cognitivo. El tratamiento con carbamacepina fue eficaz

Paroxysmal dyskinesias are movement disorders characterized by sudden episodes of involuntary movements. They are divided into kinesigenic, non-kinesigenic, and exerciseinduced dyskinesias. Emphasis is made on the importance of the clinical history and fully describing the episodes in the differential diagnosis. The case is presented of a twelve year-old female with paroxysmal episodes of tongue torsion and dystonic postures of the upper limbs when start running or descending stairs and in the beginning of physical exercise, which ceased spontaneously seconds later. Some episodes were triggered by stress. In family history her father, paternal uncle, and sister also had paroxysmal movements. Interictal neurological examination was normal. Laboratory tests revealed a mutation in PRRT2 gene, which is related to neurological disorders such as paroxysmal kinesigenic dyskinesia, infantile convulsions and choreoathetosis migraine, episodic ataxia, paroxysmal torticollis, and intellectual disability. Treatment with carbamazepine was effective

Echogenicity of basal ganglia structures in different Huntington's disease phenotypes.

In Huntington's disease (HD), a neurodegenerative-inherited disease, chorea as the typical kind of movement disorder is described. Beside chorea, however, all other kinds of movement disturbances, such as bradykinesia, dystonia, tremor or myoclonus can occur. Aim of the current study was to investigate alterations in the echogenicity of basal ganglia structures in different Huntington's disease phenotypes. 47 patients with manifest and genetically confirmed HD were recruited. All participants underwent a thorough neurological examination. According to a previously described method, classification into predominantly choreatic, mixed or bradykinetic-rigid motor phenotypes was performed depending on subscores of the Unified Huntington's Disease Rating Scale. In addition, findings in juvenile HD were compared to adult HD. Transcranial sonography was performed by investigators blinded to clinical classification. There were no significant differences in basal ganglia echogenicities between the three phenotypes. Size of echogenic area of substantia nigra (SN) correlated positively with CAG repeat and bradykinesia subscore, and negatively with age of onset and chorea subscore. Comparing juvenile and adult HD subtypes, SN hyperechogenicity was significantly more often detectable in the juvenile form (100 vs. 29.3 %, p = 0.002). Regarding echogenicity of caudate or lentiform nuclei, no significant differences were detected. HD patients with the juvenile variant exhibit marked hyperechogenicity of substantia nigra. No significant differences in basal ganglia echogenicities between predominantly choreatic, mixed or bradykinetic-rigid motor phenotypes were detected.

Genetic and phenotypic heterogeneity in sporadic and familial forms of paroxysmal dyskinesia.

Paroxysmal dyskinesia (PxD) is a group of movement disorders characterized by recurrent episodes of involuntary movements. Familial paroxysmal kinesigenic dyskinesia (PKD) is caused by PRRT2 mutations, but a distinct etiology has been suggested for sporadic PKD. Here we describe a cohort of patients collected from our movement disorders outpatient clinic in the period 1996-2011. Fifteen patients with sporadic PxD and 23 subjects from three pedigrees with familial PKD were screened for mutations in candidate genes. PRRT2 mutations co-segregated with PKD in two families and occurred in two sporadic cases of PKD. No mutations were detected in patients with non-kinesigenic or exertion-induced dyskinesia, and none in other candidate genes including PNKD1 (MR-1) and SLC2A1 (GLUT1). Thus, PRRT2 mutations also cause sporadic PKD as might be expected given the variable expressivity and reduced penetrance observed in familial PKD. Further genetic heterogeneity is suggested by the absence of candidate gene mutations in both sporadic and familial PKD suggesting a contribution of other genes or non-coding regions.

Benign hereditary chorea.

Benign hereditary chorea (BHC) is a hyperkinetic movement disorder that historically has been characterized as a nonprogressive, dominantly inherited, childhood-onset chorea with normal intelligence. However, in some cases, atypical features were described such that controversy arose regarding whether BHC was a single syndrome. In 2002, a candidate gene, thyroid transcription factor (TITF-1), was identified to cause at least some cases of BHC. Since that time, the classical phenotype has expanded further to include "brain-thyroid-lung syndrome," which, in addition to the neurological symptoms, also manifests variable degrees of thyroid and lung abnormalities. Pathophysiologic mechanisms by which symptoms can occur are postulated to include haploinsufficiency (loss of function) and/or dominant negative effect on wild-type protein. However, genotype-phenotype correlations are complex and there is no clear relationship between mutation size, location or type of mutation, and severity of phenotype. Gross and microscopic pathology has been unremarkable, though immunohistochemistry suggests that BHC may manifest as a result of a reduced complement of migratory interneurons to the striatum and cortex. This chapter reviews the historical literature and current understanding regarding this familial, developmental disorder.

[Paroxysmal kinesigenic dyskinesia]. / Paroxysmalis kinesogenicus dyskinesia.

Paroxysmal kinesigenic dyskinesia (PKD) is a rare neurological disease and the diagnosis is based on case history and clinical features. Despite of simply diagnostic criteria, the recognition of the disease is sometimes delayed. The involuntary movements in PKD lead to anxiety, social isolation, trauma and worsens the quality of life. To establish the diagnosis many other paroxysmal syndromes have to be excluded. The disease responds to antiepileptic therapy well. The genetic background of the familiar cases is not known. Here we present a 19 year-old patient with PKD and review the current literature. Our patient's events were triggered by sudden movements and last several seconds. His physical and neurological examinations were normal and responded well to carbamazepine therapy.

[Differential diagnosis of chorea].

Chorea is an involuntary movement that appears along with many diseases, it is commonly described as a frequent, brief, sudden, and twitch-like movement that is manifested in various parts of the body in a chaotic pattern. Huntington disease (HD) is a representative neurodegenerative disorder that presents with chorea. Although HD is caused by a CAG-repeat expansion in the IT-15 gene which encodes huntingtin, a small group of patients showing the symptoms and signs of HD do not have the causative CAG-repeat expansion, thereby showing that autosomal-dominant chorea is genetically heterogeneous. Recent studies have demonstrated that such disorders include dentatorubral pallidoluysian atrophy (DRPLA), spinocerebellar ataxia type 17 (SCA17), Huntington disease like 1 (HDL1), Huntington disease like 2 (HDL2), and benign hereditary chorea (BHC). We recently identified 2 Japanese families with adult-onset benign chorea that was inherited in an autosomal-dominant pattern that was linked to chromosome 8q22.2-q23.3, and we named this disease "benign hereditary chorea type 2 (BHC2)". Chorea can also be caused by a wide range of other hereditary diseases and sporadic disease such as metabolic, infectious, inflammatory, vascular, and drug-induced syndromes. In this article, we have reviewed the clinical features of the disorders associated with chorea.

The borderland of epilepsy: clinical and molecular features of phenomena that mimic epileptic seizures.

Paroxysmal losses of consciousness and other episodic neurological symptoms have many causes. Distinguishing epileptic from non-epileptic disorders is fundamental to diagnosis, but even this basic dichotomy is often challenging and is certainly not new. In 1907, the British neurologist William Richard Gowers published his book The Border-land of Epilepsy in which he discussed paroxysmal conditions "in the border-land of epilepsy-near it, but not of it" and their clinical differentiation from epilepsy itself. Now, a century later, we revisit the epilepsy borderland, focusing on syncope, migraine, vertigo, parasomnias, and some rarer paroxysmal disorders. For each condition, we review the clinical distinction from epileptic seizures. We then integrate current understanding of the molecular pathophysiology of these disorders into this clinical framework. This analysis shows that, although the clinical manifestations of paroxysmal disorders are highly heterogeneous, striking similarities in molecular pathophysiology are seen among many epileptic and non-epileptic paroxysmal phenomena.

[Paroxysmal dyskinesias]. / Discinesias paroxísticas.

INTRODUCTION: Paroxysmal dyskinesias are uncommon movements disorders that consist on recurrent brief episodes characterized by attacks with any combination of dystonia, chorea, athetosis or ballismus. DEVELOPMENT AND CONCLUSIONS: The pathophysiology of paroxysmal dyskinesias is unclear at the present time. An epileptic mechanism and basal ganglia disorders have been proposed although channelopathy due to ion channel mutations have been recently suggested. These disorders were classified by Demirkiran and Jankovic into two main groups: paroxysmal kinesigenic dyskinesia if the attacks were induced by sudden movement and paroxysmal nonkinesigenic dyskinesia if they were not. In addition to these groups, two more types have been known, namely paroxysmal exercise-induced dyskinesia and hypnogenic paroxysmal dyskinesia. As well association between benign infantile familial convulsions and paroxysmal choreoathetosis, or rolandic epilepsy, episodes of exercise induced dystonia, and writers' cramp have been described. Also others paroxysmal movements disorders have been known, we mention below. Paroxysmal dyskinesias can further be divided into idiopathic (familiar in most of the cases) or secondary cases depending on underlying cause.