Familial paroxysmal dystonic choreoathetosis and its differentiation from related syndromes

Long-term low-dose lamotrigine for paroxysmal kinesigenic dyskinesia: a two-year investigation of cognitive function in children

Objective

While low-dose lamotrigine has shown effectiveness in managing paroxysmal kinesigenic dyskinesia (PKD) in pediatric populations, the cognitive consequences of extended use are yet to be fully elucidated. This study seeks to assess the evolution of cognitive functions and the amelioration of attention deficit and hyperactivity disorder (ADHD) symptoms following a two-year lamotrigine treatment in children.

Methods

This investigation employed an open-label, uncontrolled trial design. Between January 2008 and December 2021, thirty-one participants, ranging in age from 6.5 to 14.1 years, were enrolled upon receiving a new diagnosis of PKD, as defined by the clinical diagnostic criteria set by Bruno in 2004. Comprehensive evaluation of PRRT2 variants and 16p11.2 microdeletion was achieved using whole-exome sequencing (WES) and bioinformatics analysis of copy number variant (CNV) for all subjects. Immediately after diagnosis, participants commenced treatment with low-dose lamotrigine. Cognitive function was assessed using the Wechsler Intelligence Scale for Children-Chinese Revised (WISC-CR) at baseline and after 2 years, with ADHD diagnoses and symptom severity simultaneously assessed by experts in accordance with the DSM-IV diagnostic criteria for ADHD and the ADHD Rating Scale-IV (ADHD-RS-IV).

Results

Initially, twelve out of 31 patients (38.7%) presented with comorbid ADHD. The latency to treatment initiation was notably longer in PKD patients with ADHD (30.75 ± 12.88 months) than in those without ADHD (11.66 ± 9.08 months), t = 4.856, p<0.001. Notably, patients with a latency exceeding 2 years exhibited a heightened risk for comorbid ADHD (OR = 4.671, P=0.015) in comparison to those with shorter latency. Out of the cohort, twenty-five patients saw the clinical trial to its completion. These individuals demonstrated a marked elevation in WISC-CR scores at the 2-year mark relative to the outset across FSIQ (baseline mean: 108.72 ± 10.45 vs 24 months: 110.56 ± 10.03, p=0.001), VIQ (baseline mean: 109.44 ± 11.15 vs 24 months: 110.80 ± 10.44, p=0.028), and PIQ domains (baseline mean: 106.52 ± 9.74 vs 24 months: 108.24 ± 9.38, p=0.012). Concurrently, a substantial mitigation was observed in ADHD inattention at 2 years compared to baseline (p<0.001), with an average total subscale scores decrement from 9.04 ± 4.99 to 6.24 ± 4.05.

Conclusion

Prolonged duration of untreated PKD in children may elevate the risk of ADHD comorbidity. Notably, following a 2-year lamotrigine regimen, enhancements were observed in both cognitive test outcomes and ADHD symptomatology.

Genetic Links to Episodic Movement Disorders: Current Insights

Episodic or paroxysmal movement disorders (PxMD) are conditions, which occur episodically, are transient, usually have normal interictal periods, and are characterized by hyperkinetic disorders, including ataxia, chorea, dystonia, and ballism. Broadly, these comprise paroxysmal dyskinesias (paroxysmal kinesigenic and non-kinesigenic dyskinesia [PKD/PNKD], paroxysmal exercise-induced dyskinesias [PED]) and episodic ataxias (EA) types 1-9. Classification of paroxysmal dyskinesias has traditionally been clinical. However, with advancement in genetics and the discovery of the molecular basis of several of these disorders, it is becoming clear that phenotypic pleiotropy exists, that is, the same variant may give rise to a variety of phenotypes, and the classical understanding of these disorders requires a new paradigm. Based on molecular pathogenesis, paroxysmal disorders are now categorized as synaptopathies, transportopathies, channelopathies, second-messenger related disorders, mitochondrial or others. A genetic paradigm also has an advantage of identifying potentially treatable disorders, such as glucose transporter 1 deficiency syndromes, which necessitates a ketogenic diet, and ADCY5-related disorders, which may respond to caffeine. Clues for a primary etiology include age at onset below 18 years, presence of family history and fixed triggers and attack duration. Paroxysmal movement disorder is a network disorder, with both the basal ganglia and the cerebellum implicated in pathogenesis. Abnormalities in the striatal cAMP turnover pathway may also be contributory. Although next-generation sequencing has restructured the approach to paroxysmal movement disorders, the genetic underpinnings of several entities remain undiscovered. As more genes and variants continue to be reported, these will lead to enhanced understanding of pathophysiological mechanisms and precise treatment.

[A case of a pathological variant of the PRRT2 gene in twins with paroxysmal kinesiogenic dyskinesia]

Paroxysmal dyskinesia is a clinically and etiologically polymorphic group of diseases, the main clinical manifestation of which is transient attacks of extrapyramidal movements, with different conditions of occurrence. Paroxysmal kinesigenic dyskinesia belongs to the group of primary dyskinesias, which also includes paroxysmal non-kinesigenic dyskinesia and exercise-induced paroxysmal dyskinesia. The most common cause of paroxysmal kinesiogenic dyskinesia is mutations in the PRRT2 gene; in cases of non-kinesiogenic dyskinesia, a mutation in the MR1 gene is detected. The diagnosis of primary dyskinesias causes significant difficulty for clinicians due to the rarity of occurrence, as well as the large spectrum of conditions occurring with paroxysmal motor disorders in childhood. The article describes the clinical observation of 16-year-old twin brothers with transient attacks of dystonic, choreic and ballistic hyperkinesis that suddenly arose during movement. Patients were treated for tics and epilepsy for 12 years. Taking into account the clinical picture - transient attacks of hyperkinesis, their connection with movement, as well as data from video-electroencephalographic monitoring, a diagnosis of paroxysmal kinesiogenic dyskinesia was established, which in a further diagnostic search was confirmed by targeted sequencing of the pathological variant of the PRRT2 gene previously described in patients with kinesiogenic dyskinesia. The administration of carbamazepine, which is the drug of choice in the treatment of this category of patients, has achieved significant control over hyperkinesis in twins. Thus, molecular genetic diagnosis helps confirm the diagnosis of paroxysmal dyskinesias, but careful analysis of the clinical picture, considering the provoking factor, remains the basis of diagnosis.

Paroxysmal dyskinesia and electrodermal volatility: The role of mindfulness, self-compassion and psychophysiological interventions

To date, there are no behavioral or psychophysiological treatment studies on paroxysmal dyskinesia (PD). PD is a group of debilitating movement disorders that present with severe episodes of dystonia, chorea, and/or ballistic like movements. This is a first case report of a 50-year-old male who received behavioral interventions (e.g., mindfulness, CBT, and biofeedback interventions) to manage his PD episodes in tandem with multidisciplinary treatments (e.g., neurology, psychiatry, etc.). The paper primarily discusses the serendipitous observation of galvanic skin response (GSR) elevations and spikes immediately before and after the onset of PD episodes. GSR volatility was noted in wave amplitude and wave morphology. Graphs are presented to illustrate GSR volatility associate with PD episodes and the reduction of GSR volatility in response to behavioral approaches. The discussion highlights the feasibility of using GSR biofeedback as an adjunct to mindfulness and CBT to manage PD as part of a multidisciplinary treatment approach. Peripherally, issues that related to misclassification of somatic symptoms and related disorders (e.g., psychogenic non-epileptic seizures) and aspects of neurocognitive disorders are discussed. The paper reviews neurological findings, MRI, neuropsychological data, and psychiatric assessment to highlight the dilemma clinician's face and clarify behavioral practices to further the management of PD.

PRRT2 Related Epilepsies: A Gene Review

PRRT2 encodes for proline-rich transmembrane protein 2 involved in synaptic vesicle fusion and presynaptic neurotransmitter release. Mutations in human PRRT2 have been related to paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions with choreoathetosis, benign familial infantile epilepsies, and hemiplegic migraine. PRRT2 mutations cause neuronal hyperexcitability, which could be related to basal ganglia or cortical circuits dysfunction, leading to paroxysmal disorders. PRRT2 is expressed in the cerebral cortex, basal ganglia, and cerebellum. Approximately, 90% of pathogenic variants are inherited and 10% are de novo. Paroxysmal attacks in PKD are characterized by dystonia, choreoathetosis, and ballismus. In the benign familial infantile epilepsy (BFIE), seizures are usually focal with or without generalization, usually begin between 3 and 12 months of age and remit by 2 years of age. In 30% of cases of PRRT2-associated PKD, there is an association with BFIE, and this entity is referred to as PKD with infantile convulsions (PKD/IC). PRRT2 mutations are the cause of benign family childhood epilepsy and PKD/IC. On the other hand, PRRT2 mutations do not seem to correlate with other types of epilepsy. The increasing incidence of hemiplegic migraine in families with PRRT2-associated PKD or PKD/IC suggests a common disease pathway, and it is possible to assert that BFIE, paroxysmal kinesigenic dyskinesia, and PKD with IC belong to a continuous disease spectrum of PRRT2-associated diseases.

Paroxysmal Genetic Movement Disorders and Epilepsy

Paroxysmal movement disorders include paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, paroxysmal exercise-induced dyskinesia, and episodic ataxias. In recent years, there has been renewed interest and recognition of these disorders and their intersection with epilepsy, at the molecular and pathophysiological levels. In this review, we discuss how these distinct phenotypes were constructed from a historical perspective and discuss how they are currently coalescing into established genetic etiologies with extensive pleiotropy, emphasizing clinical phenotyping important for diagnosis and for interpreting results from genetic testing. We discuss insights on the pathophysiology of select disorders and describe shared mechanisms that overlap treatment principles in some of these disorders. In the near future, it is likely that a growing number of genes will be described associating movement disorders and epilepsy, in parallel with improved understanding of disease mechanisms leading to more effective treatments.

Recommendations for the diagnosis and treatment of paroxysmal kinesigenic dyskinesia: an expert consensus in China

Paroxysmal dyskinesias are a group of neurological diseases characterized by intermittent episodes of involuntary movements with different causes. Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesia and can be divided into primary and secondary types based on the etiology. Clinically, PKD is characterized by recurrent and transient attacks of involuntary movements precipitated by a sudden voluntary action. The major cause of primary PKD is genetic abnormalities, and the inheritance pattern of PKD is mainly autosomal-dominant with incomplete penetrance. The proline-rich transmembrane protein 2 (PRRT2) was the first identified causative gene of PKD, accounting for the majority of PKD cases worldwide. An increasing number of studies has revealed the clinical and genetic characteristics, as well as the underlying mechanisms of PKD. By seeking the views of domestic experts, we propose an expert consensus regarding the diagnosis and treatment of PKD to help establish standardized clinical evaluation and therapies for PKD. In this consensus, we review the clinical manifestations, etiology, clinical diagnostic criteria and therapeutic recommendations for PKD, and results of genetic analyses in PKD patients performed in domestic hospitals.

Treatment of Paroxysmal Dyskinesia

Paroxysmal dyskinesia (PxD) is a heterogeneous group of syndromes characterized by recurrent attacks of abnormal movements, triggered by detectable factors, without loss of consciousness. According to the precipitating factors, they are classified as paroxysmal kinesigenic dyskinesia (PKD), paroxysmal non-kinesigenic dyskinesia (PNKD), and paroxysmal exercise-induced dystonia (PED). PxD treatment is based on the combination of nonpharmacologic and pharmacologic approaches. Pharmacologic and nonpharmacologic treatments effective for PNKD and PED also are available. In PxD refractory to conventional treatment, surgery might be an alternative therapeutic option. The course of PRRT2-PKD and MR-1-PNKD is benign, and treatment might not be needed with advancing age.

Presynaptic PRRT2 Deficiency Causes Cerebellar Dysfunction and Paroxysmal Kinesigenic Dyskinesia

PRRT2 loss-of-function mutations have been associated with familial paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions and choreoathetosis, and benign familial infantile seizures. Dystonia is the foremost involuntary movement disorder manifest by patients with PKD. Using a lacZ reporter and quantitative reverse-transcriptase PCR, we mapped the temporal and spatial distribution of Prrt2 in mouse brain and showed the highest levels of expression in cerebellar cortex. Further investigation into PRRT2 localization within the cerebellar cortex revealed that Prrt2 transcripts reside in granule cells but not Purkinje cells or interneurons within cerebellar cortex, and PRRT2 is presynaptically localized in the molecular layer. Analysis of synapses in the cerebellar molecular layer via electron microscopy showed that Prrt2^-/- mice have increased numbers of docked vesicles but decreased vesicle numbers overall. In addition to impaired performance on several motor tasks, approximately 5% of Prrt2^-/- mice exhibited overt PKD with clear face validity manifest as dystonia. In Prrt2 mutants, we found reduced parallel fiber facilitation at parallel fiber-Purkinje cell synapses, reduced Purkinje cell excitability, and normal cerebellar nuclear excitability, establishing a potential mechanism by which altered cerebellar activity promotes disinhibition of the cerebellar nuclei, driving motor abnormalities in PKD. Overall, our findings replicate, refine, and expand upon previous work with PRRT2 mouse models, contribute to understanding of paroxysmal disorders of the nervous system, and provide mechanistic insight into the role of cerebellar cortical dysfunction in dystonia.

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 movement disorders - practical update on diagnosis and management

Introduction: Paroxysmal dyskinesias and episodic ataxias are often caused by mutations in genes related to cell membrane and synaptic function. Despite the exponential increase in publications of genetically confirmed cases, management remains largely clinical based on non-systematic evidence. Areas covered: The authors provide a historical and clinical review of the main types of paroxysmal dyskinesias and episodic ataxias, with recommendations for diagnosis and management of patients suffering from these conditions. Expert opinion: After secondary paroxysmal dyskinesias, the most common paroxysmal movement disorders are likely to be PRRT2-associated paroxysmal kinesigenic dyskinesias, which respond well to small doses of carbamazepine, and episodic ataxia type 2, which often responds to acetazolamide. Familial paroxysmal non-kinesigenic dyskinesias are largely caused by mutations in PNKD and have poor response to therapy but improve with age. Exercise-induced dyskinesias are genetically heterogeneous, caused by disorders of glucose transport, mitochondrial function, dopaminergic pathways or neurodegenerative conditions amongst others. GNAO1 and ADCY5 mutations can also cause paroxysmal movement disorders, often in the context of ongoing motor symptoms. Although a therapeutic trial is justified for classic cases and in limited resource settings, genetic testing may help direct initial or rescue therapy. Deep brain stimulation may be an option for severe cases.

The spectrum of paroxysmal dyskinesias

Paroxysmal dyskinesias (PxD) comprise a group of heterogeneous syndromes characterized by recurrent attacks of mainly dystonia and/or chorea, without loss of consciousness. PxD have been classified according to their triggers and duration as paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia and paroxysmal exertion-induced dyskinesia. Of note, the spectrum of genetic and nongenetic conditions underlying PxD is continuously increasing, but not always a phenotype–etiology correlation exists. This creates a challenge in the diagnostic work-up, increased by the fact that most of these episodes are unwitnessed. Furthermore, other paroxysmal disorders, included those of psychogenic origin, should be considered in the differential diagnosis. In this review, some key points for the diagnosis are provided, as well as the appropriate treatment and future approaches discussed.

Clinical Features and Treatment in the Spectrum of Paroxysmal Dyskinesias: An Observational Study in South-West Castilla y Leon, Spain

BACKGROUND

Paroxysmal dyskinesias (PxD) are a group of heterogeneous disorders characterized by intermittent episodes of involuntary movements. PxD include paroxysmal kinesigenic (PKD), nonkinesigenic (PNK), and exercise-induced (PED) varieties.

OBJECTIVES

To define the phenotype of primary and secondary PxD forms.

METHODS

Twenty-two patients with PxD (9 men/13 women) were evaluated in two hospitals in south-west Castilla y Leon, Spain. Clinical features of the episodes, causes, family history, and response to treatment were collected.

RESULTS

Thirteen participants with primary PxD (6 men/7 women) and 9 with secondary PxD (3 men/6 women) were recruited. Nine patients belong to three nonrelated families (2 had PKD and 1 had PED). Mean age at onset in primary PKD cases was 10 years (range 5-23 years), earlier than in PNKD (24 years) and PED (20 years). Most primary PKD cases experienced daily episodes of duration <1 minute, which are more frequent and shorter attacks than in PNKD (1-2 per month, 5 minutes) and PED (1 per day, 15 minutes). The location of the involuntary movements varied widely; isolated dystonia was more common than mixed chorea and dystonia. All PKD patients who received antiepileptic treatment significantly improved. Levodopa and ketogenic diet proved to be effective in two patients with PED. Secondary forms presented a later mean age of onset (51 years). Six cases had PNKD, 1 had PKD, 1 both PNKD and PKD, and 1 had PED. Causes comprised vascular lesions, encephalitis, multiple sclerosis, peripheral trauma, endocrinopathies, and drugs such as selective serotonin reuptake inhibitors (SSRIs).

CONCLUSION

The knowledge of the clinical features and spectrum of causes related to PxD is crucial to avoid delays in diagnosis and treatment, or even a nonorganic disorder diagnosis.

Unravelling of the paroxysmal dyskinesias

Paroxysmal dyskinesias (PxD) refer to a rare group of clinically and genetically heterogeneous disorders presenting with recurrent attacks of abnormal movements, typically dystonia, chorea or a combination thereof, without loss of consciousness. Classically, PxD have been categorised according to their triggers and duration of the attacks, but increasing evidence suggests that there is a certain degree of clinical and genetic overlap and challenges the concept that one phenotype is attributable to one single aetiology. Here we review the increasing spectrum of genetic conditions, as well as of other non-genetic disorders, that might present with PxD, provide criteria for case definition and propose a diagnostic workup to reach a definitive diagnosis, on which treatment is heavily dependent.

Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes

Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis‐characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.

Paroxysmal Dyskinesia in Children: from Genes to the Clinic

Background and Purpose

Paroxysmal dyskinesia is a genetically and clinically heterogeneous movement disorder. Recent studies have shown that it exhibits both phenotype and genotype overlap with other paroxysmal disorders as well as clinical heterogeneity. We investigated the clinical and genetic characteristics of paroxysmal dyskinesia in children.

Methods

Fifty-five patients (16 from 14 families and 39 sporadic cases) were enrolled. We classified them into three phenotypes: paroxysmal kinesigenic dyskinesia (PKD), paroxysmal nonkinesigenic dyskinesia (PNKD), and paroxysmal exercise-induced dyskinesia (PED). We sequenced PRRT2, SLC2A1, and MR-1 in these patients and reviewed their medical records.

Results

Forty patients were categorized as PKD, 14 as PNKD, and 1 as PED. Thirty-eight (69.1%) patients were male, and their age at onset was 8.80±4.53 years (mean±SD). Dystonia was the most common symptom (38 patients, 69.1%). Pathogenic variants were identified in 20 patients (36.4%): 18 with PRRT2 and 2 with SLC2A1. All of the patients with PRRT2 mutations presented with PKD alone. The 2 patients carrying SLC2A1 mutations presented as PNKD and PED, and one of them was treated effectively with a ketogenic diet. Six mutations in PRRT2 (including 2 novel variants) were identified in 9 of the 13 tested families (69.2%) and in 8 patients of the 25 tested sporadic cases (32.0%). There were no significant differences in clinical features or drug response between the PRRT2-positive and PRRT2-negative PKD groups.

Conclusions

This study has summarized the clinical and genetic heterogeneity of paroxysmal dyskinesia in children. We suggest that pediatric paroxysmal dyskinesia should not be diagnosed using clinical features alone, but by combining them with broader genetic testing.

Phenotypes, genotypes, and the management of paroxysmal movement disorders

As a consequence of the genomic revolution, a large number of publications describing paroxysmal movement disorders have been published in the last few years, shedding light on their molecular pathology. Routine gene testing is not necessary to guide treatment for typical forms of paroxysmal kinesigenic dyskinesia (PKD), paroxysmal nonkinesigenic dyskinesia (PNKD), and episodic ataxia type 1 or 2. It can, however, be helpful in the management of atypical or complex cases, especially for genetic counselling, treatment strategies, and the offer of preimplantation genetic diagnosis. Antiepileptic drugs remain the treatment of choice for PKD and episodic ataxia type 1, benzodiazepines are often useful for PNKD, and episodic ataxia type 2 benefits from acetazolamide regardless of the genetic etiology.

WHAT THE PAPER ADDS

A growing number of genes have been associated with classic and newly described paroxysmal movement disorders. Paroxysmal movement disorders share common mechanisms and clinical features with other neurological paroxysmal phenomena including epilepsy and migraine.

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.

Misdiagnosed atypical paroxysmal kinesigenic dyskinesia: a case report

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by sudden episodes of involuntary movements. PKD is a very rare movement disorder, and correct clinical diagnosis is often a challenge.

CASE

We present the case of a 23-year-old female with PKD. The patient showed episodes of twisting movements for 3 years. The symptoms lasted for about 5-10 minutes and subsided spontaneously. She was diagnosed as having epilepsy, and depressive and anxiety disorders successively. However, her symptoms did not alleviate after taking sodium valproate and antidepressants. Though there were no mutations in her PRRT2 gene, carbamazepine was used for treatment and was effective in controlling her symptoms.

CONCLUSION

The clinical features of PKD patients are not always typical; therefore, it is important to distinguish PKD from the other subtypes of paroxysmal dyskinesia and psychogenic disorders.

[Parasomnia and paroxysmal dyskinesia]

Short involuntary paroxysmal movements or behavioral patterns are an important differential diagnosis to epileptic seizures, especially when occurring for the first time. Typically, these attacks are not witnessed by medically trained personnel and the patient anamnesis or observations by a third party are often not specific enough to differentiate between epileptic seizures and the differential diagnoses. This review presents the epidemiology, the clinical presentation, the necessary diagnostic steps and the differential diagnostic approach to parasomnias and dyskinesias. The focus is on the clinical aspects, and therapeutic principles are also briefly described.

The epileptic and nonepileptic spectrum of paroxysmal dyskinesias: Channelopathies, synaptopathies, and transportopathies

Historically, the syndrome of primary paroxysmal dyskinesias was considered a group of disorders as a result of ion channel dysfunction. This proposition was primarily based on the discovery of mutations in ion channels, which caused other episodic neurological disorders such as epilepsy and migraine and also supported by the frequent association between paroxysmal dyskinesias and epilepsy. However, the discovery of the genes responsible for the 3 classic forms of paroxysmal dyskinesias disproved this ion channel theory. On the other hand, novel gene mutations implicating ion channels have been recently reported to produce episodic movement disorders clinically similar to the classic paroxysmal dyskinesias. Here, we review the clinical and pathophysiological aspects of the paroxysmal dyskinesias, further proposing a pathophysiological framework according to which they can be classified as synaptopathies (proline-rich transmembrane protein 2 and myofibrillogenesis regulator gene), channelopathies (calcium-activated potassium channel subunit alpha-1 and voltage-gated sodium channel type 8), or transportopathies (solute carrier family 2 member 1). This proposal might serve to explain similarities and differences among the various paroxysmal dyskinesias in terms of clinical features, treatment response, and natural history. © 2017 International Parkinson and Movement Disorder Society.

Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation

OBJECTIVE

Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination-known as infantile convulsions and paroxysmal choreoathetosis (ICCA)-are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

METHODS

We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

RESULTS

In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic-clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or "shivering" attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

INTERPRETATION

Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical-genetic spectrum of combined epileptic and dyskinetic syndromes.

The clinical and genetic heterogeneity of paroxysmal dyskinesias

The contributions of different genes to inherited paroxysmal movement disorders are incompletely understood. Gardiner et al. identify mutations in 47% of 145 individuals with paroxysmal dyskinesias, with PRRT2 mutations in 35%, SLC2A1 in 10% and PNKD in 2%. New mutations expand the associated phenotypes and implicate overlapping mechanisms.

Paroxysmal dyskinesia can be subdivided into three clinical syndromes: paroxysmal kinesigenic dyskinesia or choreoathetosis, paroxysmal exercise-induced dyskinesia, and paroxysmal non-kinesigenic dyskinesia. Each subtype is associated with the known causative genes PRRT2, SLC2A1 and PNKD, respectively. Although separate screening studies have been carried out on each of the paroxysmal dyskinesia genes, to date there has been no large study across all genes in these disorders and little is known about the pathogenic mechanisms. We analysed all three genes (the whole coding regions of SLC2A1 and PRRT2 and exons one and two of PNKD) in a series of 145 families with paroxysmal dyskinesias as well as in a series of 53 patients with familial episodic ataxia and hemiplegic migraine to investigate the mutation frequency and type and the genetic and phenotypic spectrum. We examined the mRNA expression in brain regions to investigate how selective vulnerability could help explain the phenotypes and analysed the effect of mutations on patient-derived mRNA. Mutations in the PRRT2, SLC2A1 and PNKD genes were identified in 72 families in the entire study. In patients with paroxysmal movement disorders 68 families had mutations (47%) out of 145 patients. PRRT2 mutations were identified in 35% of patients, SLC2A1 mutations in 10%, PNKD in 2%. Two PRRT2 mutations were in familial hemiplegic migraine or episodic ataxia, one SLC2A1 family had episodic ataxia and one PNKD family had familial hemiplegic migraine alone. Several previously unreported mutations were identified. The phenotypes associated with PRRT2 mutations included a high frequency of migraine and hemiplegic migraine. SLC2A1 mutations were associated with variable phenotypes including paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, episodic ataxia and myotonia and we identified a novel PNKD gene deletion in familial hemiplegic migraine. We found that some PRRT2 loss-of-function mutations cause nonsense mediated decay, except when in the last exon, whereas missense mutations do not affect mRNA. In the PNKD family with a novel deletion, mRNA was truncated losing the C-terminus of PNKD-L and still likely loss-of-function, leading to a reduction of the inhibition of exocytosis, and similar to PRRT2, an increase in vesicle release. This study highlights the frequency, novel mutations and clinical and molecular spectrum of PRRT2, SLC2A1 and PNKD mutations as well as the phenotype–genotype overlap among these paroxysmal movement disorders. The investigation of paroxysmal movement disorders should always include the analysis of all three genes, but around half of our paroxysmal series remain genetically undefined implying that additional genes are yet to be identified.

The contributions of different genes to inherited paroxysmal movement disorders are incompletely understood. Gardiner et al. identify mutations in 47% of 145 individuals with paroxysmal dyskinesias, with PRRT2 mutations in 35%, SLC2A1 in 10% and PNKD in 2%. New mutations expand the associated phenotypes and implicate overlapping mechanisms.

The Dystonias

Dystonia is a difficult problem for both the clinician and the scientist. It is sufficiently common to be seen by almost all physicians, yet uncommon enough to prevent any physician from gaining broad experience in its diagnosis and treatment. Each case represents a difficult challenge even to the specialist. The basic scientist is faced with investigating a disorder that is without relevant animal models and which is so rare that obtaining suitable tissue for study is a major obstacle. Dystonia may be idiopathic, or associated with lesions from many sources, including a variety of rare diseases. If idiopathic, it may be genetically transmitted or sporadic. If genetically transmitted, it may be generalized or focal, with symptoms varying in different members of the same family. It may be refractory to treatment, or it may respond to any one of a number of individual drugs that have very different mechanisms of action. For idiopathic dystonias, no clear method of genetic transmission has been established and no consistent pathology identified.

Paroxysmal movement disorders

Paroxysmal dyskinesias represent a group of episodic abnormal involuntary movements manifested by recurrent attacks of dystonia, chorea, athetosis, or a combination of these disorders. Paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, paroxysmal exertion-induced dyskinesia, and paroxysmal hypnogenic dyskinesia are distinguished clinically by precipitating factors, duration and frequency of attacks, and response to medication. Primary paroxysmal dyskinesias are usually autosomal dominant genetic conditions. Secondary paroxysmal dyskinesias can be the symptoms of different neurologic and medical disorders. This review summarizes the updates on etiology, pathophysiology, genetics, clinical presentation, differential diagnosis, and treatment of paroxysmal dyskinesias and other episodic movement disorders.

Treatment of paroxysmal dyskinesias in children

OPINION STATEMENT

Paroxysmal dyskinesia represents a group of uncommon movement disorders that are characterized by episodes of abnormal movements arising from a baseline of normal or nearly normal movement. Recent advances in the genetics of these disorders have helped provide some unification of classification schemes and better understanding. However, the approach to treatment continues to be based on the phenotype more than the genotype. The treatment approach is primarily based on the factors that precipitate the episodes of abnormal movements. For paroxysmal kinesigenic dyskinesia (PKD) in which the spells are triggered by sudden movement, treatment with anticonvulsants that target voltage-sensitive sodium channels (e.g., carbamazepine or phenytoin) is highly effective. For paroxysmal nonkinesigenic dyskinesia (PNKD), treatment with benzodiazepines is effective in many patients. PNKD episodes are often precipitated by caffeine, ethanol, or sleep deprivation, and lifestyle modifications are often helpful. Paroxysmal exertion-induced dyskinesia (PED) is less likely to respond to medications, but the ketogenic diet or modified Atkins diet may provide benefit. As more knowledge is gained about the underlying biology of these disorders, additional treatments may emerge.

Episodic and electrical nervous system disorders caused by nonchannel genes

As noted in the separate introduction to this special topic section, episodic and electrical disorders can appear quite different clinically and yet share many overlapping features, including attack precipitants, therapeutic responses, natural history, and the types of genes that cause many of the genetic forms (i.e., ion channel genes). Thus, as we mapped and attempted to clone genes causing other episodic disorders, ion channels were always outstanding candidates when they mapped to the critical region of linkage in such a family. However, some of these disorders do not result from mutations in channels. This realization has opened up large and exciting new areas for the pathogenesis of these disorders. In some cases, the mutations occur in genes of unknown function or without understanding of molecular pathogenesis. Recently, emerging insights into a fascinating group of episodic movement disorders, the paroxysmal dyskinesias, and study of the causative genes and proteins are leading to the emerging concept of episodic electric disorders resulting from synaptic dysfunction. Much work remains to be done, but the field is evolving rapidly. As it does, we have come to realize that the molecular pathogenesis of electrical and episodic disorders is more complex than a scenario in which such disorders are simply due to mutations in the primary determinants of membrane excitability (channels).

A case of familial paroxysmal nonkinesigenic dyskinesia due to mutation of the PNKD gene in Chinese Mainland

BACKGROUND

Paroxysmal dyskinesia is a rare neurological disorder characterized by paroxysmal movement disorders. Paroxysmal movement disorders include kinesigenic choreoathetosis, nonkinesigenic choreoathetosis or dyskinesia (PNKD), exercise-induced choreoathetosis, and hypnogenic paroxysmal dystonia. There have been some sporadic reports of PNKD occurrences in Chinese Mainland, but none has been reported on familial PNKD. Proband and methods A 32 years old male admitted to the First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China in 2009 with recurrent limb involuntary movements spanning over 30 years was diagnosed with PNKD. Family history was collected to identify if it was a case of familial or sporadic PNKD. Mutation and linkage analysis were performed to identify the pathogenic gene and the localization of the same.

RESULTS

There were five generations of 26 patients, out of which 3 of these patients died. Follow-up was conducted on 17 out of the 23 patients alive and 9 normal family members. The pedigree showed autosomal dominant inheritance, whom could be divided into light, moderate, and severe group according to clinical signs, spontaneous attack and response to drugs. All patients harbored c.20C>T (p.A7V) mutation in exon 1 of the PNKD/MR-1 gene. Preliminary linkage analyses using phenocopy rates of 0.0001 and 0.1 suggested that linkage signal localizes between D2S126 and D2S377. The functional consequence of the mutation in the disease pathogenesis is pending investigation. Conclusions We report the first case of familial paroxysmal non-kinesigenic dyskinesia (PNKD) in Chinese Mainland, which coincidentally is also the largest case of familial PNKD ever reported. This article is part of a Special Issue entitled Brain and Memory.

Paroxysmal dyskinesias revisited: a review of 500 genetically proven cases and a new classification

Paroxysmal movement disorders are a heterogeneous group of conditions manifesting as episodic dyskinesia with sudden onset and lasting a variable duration. Based on the difference of precipitating factors, three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), non-kinesigenic (PNKD), and exercise induced (PED). The elucidation of the genetic cause of various forms of paroxysmal dyskinesia has led to better clinical definitions based on genotype-phenotype correlations in the familial forms. However, it has been increasingly recognized that (1) there is a marked pleiotropy of mutations in such genes with still expanding clinical spectra; and (2) not all patients clinically presenting with either PKD, PNKD, or PED have mutations in these genes. We aimed to review the clinical features of 500 genetically proven cases published to date. Based on our results, it is clear that there is not a complete phenotypic-genotypic correlation, and therefore we suggest an algorithm to lead the genetic analyses. Given the fact that the reliability of current clinical categorization is not entirely valid, we further propose a novel classification for paroxysmal dyskinesias, which takes into account the recent genetic discoveries in this field.

Episodic movement disorders: from phenotype to genotype and back

Episodic dyskinetic movement disorders are a heterogeneous group of rare conditions. Paroxysmal dyskinesias constitute the core of this group and usually exhibit normal interepisodic neurologic findings. Contrariwise, episodic dyskinesias occur as a particular feature of complex chronic neurologic disorders. Conjunction of accurate phenotyping with up-to-date methods of molecular genetics recently provided remarkable new insights concerning the genetic causes of episodic dyskinesia. The identification of heterozygous mutations in the PRRT2 gene in paroxysmal kinesigenic dyskinesia as well as in benign familial infantile seizures linked episodic movement disorders with epilepsy. Alternating hemiplegia of childhood, the prototype of a chronic multisystem disease with episodic dyskinesia as a clinical hallmark, was recently found to be caused by heterozygous de novo mutations in the ATP1A3 gene. The clinical spectra of PRRT2 as well as of ATP1A3 mutations are still expanding. This review summarizes new genetic findings and clinical aspects in episodic dyskinesias.

Assessment of patients with isolated or combined dystonia: an update on dystonia syndromes

The clinical evaluation of a patient with dystonia is a stepwise process, beginning with classification of the phenomenology of the movement disorder(s), then formulation of the dystonia syndrome, which, in turn, leads to a targeted etiological differential diagnosis. In recent years, there have been significant advances in our understanding of the etiological basis of dystonia, aided especially by discoveries in imaging and genetics. In this review, we provide an update on the assessment of a patient with dystonia, including the phenomenology of dystonia and highlighting how to integrate clinical, imaging, blood, and neurophysiological investigations in order to formulate a dystonia syndrome. Evolving or emerging dystonia syndromes are reviewed, and potential etiologies of these as well as established dystonia syndromes listed to guide diagnostic testing. © 2013 Movement Disorder Society.

Phenotypic spectrum of glucose transporter type 1 deficiency syndrome (Glut1 DS)

Glut1 deficiency syndrome (Glut1 DS) was originally described in 1991 as a developmental encephalopathy characterized by infantile onset refractory epilepsy, cognitive impairment, and mixed motor abnormalities including spasticity, ataxia, and dystonia. The clinical condition is caused by impaired glucose transport across the blood brain barrier. The past 5 years have seen a dramatic expansion in the range of clinical syndromes that are recognized to occur with Glut1 DS. In particular, there has been greater recognition of milder phenotypes. Absence epilepsy and other idiopathic generalized epilepsy syndromes may occur with seizure onset in childhood or adulthood. A number of patients present predominantly with movement disorders, sometimes without any accompanying seizures. In particular, paroxysmal exertional dyskinesia is now a well-documented clinical feature that occurs in individuals with Glut1 DS. A clue to the diagnosis in patients with paroxysmal symptoms may be the triggering of episodes during fasting or exercise. Intellectual impairment may range from severe to very mild. Awareness of the broad range of potential clinical phenotypes associated with Glut1 DS will facilitate earlier diagnosis of this treatable neurologic condition. The ketogenic diet is the mainstay of treatment and nourishes the starving symptomatic brain during development.

Clinical features of paroxysmal kinesigenic dyskinesia: report of 24 cases

Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesia and is characterized by involuntary, intermittent movements induced by sudden movements. Here, we describe 24 patients with PKD, whose clinical data were analyzed. The attacks of involuntary movements were all short lasting, and could involve extremities, trunk, neck, or face without alteration of consciousness. The motor function was normal between attacks, and in some cases, attacks could be evoked during examination. Most patients had normal electroencephalogram (EEG) and neuroimaging results, but 2 cases had abnormal EEGs, and another 2 cases had bilateral calcification of basal ganglion on brain computed tomography (CT) scans. Previous history of misdiagnosis was a predominant feature, while treatments based on misdiagnosis sometimes did lead to improvement. Here, we discuss the clinical characteristics, especially the abnormalities of investigations and misdiagnosis, and recent insights into the pathophysiology of PKD.

Paroxysmal hypnogenic dyskinesia responsive to doxylamine: a case report

Paroxysmal hypnogenic dyskinesia is a rare clinical entity characterized by intermittent dystonia and choreoathetoid movements that begin exclusively during sleep, often with consciousness preserved once the patient is awakened during the episodes. They occur almost every night and are often misdiagnosed as sleeping disorders. Paroxysmal hypnogenic dyskinesia is currently known to be a form of frontal lobe epilepsy, but not in all cases. We present a 19-year-old male patient with paroxysmal hypnogenic dyskinesia who responded to antihistamines. This supports an alternative theory from 1977 (before the cases had been adequately described) that the disorder lies in dysregulation in the basal ganglia. This description now appears similar to acute dystonic reactions such as extrapyramidal symptoms from antipsychotic medications, which also respond to antihistamines.

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.

Diagnosis and treatment of paroxysmal dyskinesias revisited

Paroxysmal dyskinesias (PDs) are a rare group of hyperkinetic movement disorders mainly characterized by their episodic nature. Neurological examination may be entirely normal between the attacks. Three main types of PDs can be distinguished based on their precipitating events - (i) paroxysmal kinesigenic dyskinesias (PKD), (ii) paroxysmal non-kinesigenic dyskinesias (PNKD) and (iii) paroxysmal exercise-induced (exertion-induced) dyskinesias (PED). The diagnosis of PDs is based on their clinical presentation and precipitating events. Substantial progress has been made in the field of genetics and PDs. Treatment options mainly include anticonvulsants and benefit of treatment is depending on the type of PD. Most important differential diagnosis are non-epileptic psychogenic, non-epileptic organic and epileptic attack disorders, especially nocturnal frontal lobe epilepsy.

Paroxysmal dyskinesias

Paroxysmal movement disorders are a relatively rare and heterogenous group of conditions manifesting as episodic dyskinesia lasting a brief duration. Three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), nonkinisegenic (PNKD), and exercise induced (PED). There have been major advances in the understanding of the pathophysiological mechanisms and the genetics of these disorders, leading to better clinical definitions based on genotype-phenotype correlations in the familial idiopathic forms. PKD is genetically heterogenous, but there is linkage to chromosome 16 in a number of families. PNKD is due to mutations of the MR-1 gene. PED is genetically heterogenous, but a number of familial and sporadic cases may be due to GLUT-1 gene mutations. The GLUT1 gene-related form of PED may respond to a ketogenic diet. Potassium and calcium channel mutations underlie the 2 main forms of episodic ataxia (EA1 and EA2), whereas benign torticollis of infancy may also be a calcium channel disorder.

Chorea caused by toxins

Chorea is uncommonly caused by toxins. Anecdotal evidence from cases of toxin-induced chorea assists in our understanding of neurodegenerative diseases associated with chorea. Beginning in medieval Europe with ergotism and the "fire that twisted people," spanning to crack dancing in contemporary times and the coexistence of alcohol abuse with chorea, toxins may exert direct effects to enhance mesolimbic dopamine transmission or indirect effects through gamma-aminobutyric acid modulation. The following chapter will discuss toxins associated with chorea and the presumed pathophysiology underlying the movement disorders in these case series.

Paroxysmal choreodystonic disorders

Paroxysmal choreodystonic disorders or paroxysmal dyskinesias are a heterogeneous group of movement disorders characterized by recurrent attacks of abnormal involuntary movements. They are classified into four categories according to the precipitant, duration of attacks, and etiology: (1) paroxysmal kinesigenic dyskinesia (PKD), in which attacks are brief and induced by sudden voluntary movements; (2) paroxysmal nonkinesigenic dyskinesia (PNKD), in which attacks occur spontaneously; (3) paroxysmal exertion-induced dyskinesia (PED), in which attacks are brought on by prolonged exercise; and (4) paroxysmal hypnogenic dyskinesia (PHD), in which attacks occur during sleep. Among them, PHD is currently known to be a form of mesial frontal-lobe epilepsy, and has been given the term "autosomal-dominant nocturnal frontal lobe epilepsy" (ANDFLE) in some familiar cases with an autosomal-dominant inheritance. The clinical, etiological and pathophysiological features of PKD, PNKD, and PED are reviewed.

Treatment of paroxysmal dyskinesias

IMPORTANCE OF THE FIELD

Paroxysmal dyskinesias represent a heterogeneous group of rare diseases sharing characteristics with two important groups of neurological disorders, the movement disorders and the epilepsies. Their common hallmark is the paroxysmal occurrence of dyskinesias including athetosis, ballism, chorea and dystonia. During the last two decades, various genetic abnormalities have been identified thereby providing insight into the underlying pathophysiology and offering therapeutic opportunities for many of these conditions.

AREAS COVERED IN THIS REVIEW

We summarize the diagnostic criteria of idiopathic and symptomatic paroxysmal dyskinesias and describe their therapeutic options. For the preparation of this review article, an extensive literature search was undertaken using PubMed.

WHAT THE READER WILL GAIN

This review provides a practical guide to the diagnosis and treatment of paroxysmal dyskinesias.

TAKE HOME MESSAGE

The mainstay of therapy is carbamazepine for paroxysmal kinesigenic dyskinesias and clonazepam for the nonkinesigenic dyskinesias. In symptomatic paroxysmal dyskinesias, the treatment of the underlying disease will provide best results. The ketogenic diet for patients with paroxysmal exertion-induced dyskinesias is a promising new therapeutic strategy and may not only prevent attacks but also lead to improvement of developmental delay in affected children.