Rare Missense Variants in KCNJ10 Are Associated with Paroxysmal Kinesigenic Dyskinesia

BACKGROUND

Although the group of paroxysmal kinesigenic dyskinesia (PKD) genes is expanding, the molecular cause remains elusive in more than 50% of cases.

OBJECTIVE

The aim is to identify the missing genetic causes of PKD.

METHODS

Phenotypic characterization, whole exome sequencing and association test were performed among 53 PKD cases.

RESULTS

We identified four causative variants in KCNJ10, already associated with EAST syndrome (epilepsy, cerebellar ataxia, sensorineural hearing impairment and renal tubulopathy). Homozygous p.(Ile209Thr) variant was found in two brothers from a single autosomal recessive PKD family, whereas heterozygous p.(Cys294Tyr) and p.(Thr178Ile) variants were found in six patients from two autosomal dominant PKD families. Heterozygous p.(Arg180His) variant was identified in one additional sporadic PKD case. Compared to the Genome Aggregation Database v2.1.1, our PKD cohort was significantly enriched in both rare heterozygous (odds ratio, 21.6; P = 9.7 × 10-8 ) and rare homozygous (odds ratio, 2047; P = 1.65 × 10-6 ) missense variants in KCNJ10.

CONCLUSIONS

We demonstrated that both rare monoallelic and biallelic missense variants in KCNJ10 are associated with PKD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

An Electroencephalography Profile of Paroxysmal Kinesigenic Dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) is associated with a disturbance of neural circuit and network activities, while its neurophysiological characteristics have not been fully elucidated. This study utilized the high-density electroencephalogram (hd-EEG) signals to detect abnormal brain activity of PKD and provide a neural biomarker for its clinical diagnosis and PKD progression monitoring. The resting hd-EEGs are recorded from two independent datasets and then source-localized for measuring the oscillatory activities and function connectivity (FC) patterns of cortical and subcortical regions. The abnormal elevation of theta oscillation in wildly brain regions represents the most remarkable physiological feature for PKD and these changes returned to healthy control level in remission patients. Another remarkable feature of PKD is the decreased high-gamma FCs in non-remission patients. Subtype analyses report that increased theta oscillations may be related to the emotional factors of PKD, while the decreased high-gamma FCs are related to the motor symptoms. Finally, the authors established connectome-based predictive modelling and successfully identified the remission state in PKD patients in dataset 1 and dataset 2. The findings establish a clinically relevant electroencephalography profile of PKD and indicate that hd-EEG can provide robust neural biomarkers to evaluate the prognosis of PKD.

Genetic and phenotypic analyses of PRRT2 positive and negative paroxysmal kinesigenic dyskinesia

Background

Paroxysmal kinesigenic dyskinesia (PKD) is a rare neurological disorder, characterized by attacks of involuntary movements triggered by sudden action. Variants in proline-rich transmembrane protein 2 (PRRT2) are the most common genetic cause of PKD.

Objective

The objective was to investigate the clinical and genetic characteristics of PKD and to establish genotype-phenotype correlations.

Methods

We enrolled 219 PKD patients, documented their clinical information and performed PRRT2 screening using Sanger sequencing. Whole exome sequencing was performed on 49 PKD probands without PRRT2 variants. Genotype-phenotype correlation analyses were conducted on the probands.

Results

Among 219 PKD patients (99 cases from 39 families and 120 sporadic cases), 16 PRRT2 variants were identified. Nine variants (c.879+4A>G, c.879+5G>A, c.856G>A, c.955G>T, c.884G>C, c.649C>T, c.649dupC, c.649delC and c.696_697delCA) were previously known, while seven were novel (c.367_403del, c.347_348delAA, c.835C>T, c.116dupC, c.837_838insC, c.916_937del and c.902G>A). The mean interval from onset to diagnosis was 7.94 years. Compared to patients without PRRT2 variants, patients with the variants were more likely to have a positive family history, an earlier age of onset and a higher prevalence of falls during pre-treatment attacks (27.14% versus 8.99%, respectively). Patients with truncated PRRT2 variants tend to have bilateral attacks. We identified two transmembrane protein 151A (TMEM151A) variants including a novel variant (c.368G>C) and a reported variant (c.203C>T) in two PRRT2-negative probands with PKD.

Conclusion

These findings provide insights on the clinical characteristics, diagnostic timeline and treatment response of PKD patients. PKD patients with truncated PRRT2 variants may tend to have more severe paroxysmal symptoms. This study expands the spectrum of PRRT2 and TMEM151A variants. Carbamazepine and oxcarbazepine are both used as a first-line treatment choice for PKD patients.

Effects of PRRT2 mutation on brain gray matter networks in paroxysmal kinesigenic dyskinesia

Although proline-rich transmembrane protein 2 is the primary causative gene of paroxysmal kinesigenic dyskinesia, its effects on the brain structure of paroxysmal kinesigenic dyskinesia patients are not yet clear. Here, we explored the influence of proline-rich transmembrane protein 2 mutations on similarity-based gray matter morphological networks in individuals with paroxysmal kinesigenic dyskinesia. A total of 51 paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 mutations, 55 paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 non-mutation, and 80 healthy controls participated in the study. We analyzed the structural connectome characteristics across groups by graph theory approaches. Relative to paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 non-mutation and healthy controls, paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 mutations exhibited a notable increase in characteristic path length and a reduction in both global and local efficiency. Relative to healthy controls, both patient groups showed reduced nodal metrics in right postcentral gyrus, right angular, and bilateral thalamus; Relative to healthy controls and paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 non-mutation, paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 mutations showed almost all reduced nodal centralities and structural connections in cortico-basal ganglia-thalamo-cortical circuit including bilateral supplementary motor area, bilateral pallidum, and right caudate nucleus. Finally, we used support vector machine by gray matter network matrices to classify paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 mutations and paroxysmal kinesigenic dyskinesia patients possessing proline-rich transmembrane protein 2 non-mutation, achieving an accuracy of 73%. These results show that proline-rich transmembrane protein 2 related gray matter network deficits may contribute to paroxysmal kinesigenic dyskinesia, offering new insights into its pathophysiological mechanisms.

Proline-rich transmembrane protein 2 knock-in mice present dopamine-dependent motor deficits

Mutations of proline-rich transmembrane protein 2 (PRRT2) lead to dyskinetic disorders such as paroxysmal kinesigenic dyskinesia (PKD), which is characterized by attacks of involuntary movements precipitated by suddenly initiated motion, and some convulsive disorders. Although previous studies have shown that PKD might be caused by cerebellar dysfunction, PRRT2 has not been sufficiently analyzed in some motor-related regions, including the basal ganglia, where dopaminergic neurons are most abundant in the brain. Here, we generated several types of Prrt2 knock-in (KI) mice harboring mutations, such as c.672dupG, that mimics the human pathological mutation c.649dupC and investigated the contribution of Prrt2 to dopaminergic regulation. Regardless of differences in the frameshift sites, all truncating mutations abolished Prrt2 expression within the striatum and cerebral cortex, consistent with previous reports of similar Prrt2 mutant rodents, confirming the loss-of-function nature of these mutations. Importantly, administration of l-dopa, a precursor of dopamine, exacerbated rotarod performance, especially in Prrt2-KI mice. These findings suggest that dopaminergic dysfunction in the brain by the PRRT2 mutation might be implicated in a part of motor symptoms of PKD and related disorders.

Functional Neurological Disorder Overlapping Paroxysmal Kinesigenic Dyskinesia Confirmed by Genetic Diagnosis

Functional neurological disorder (FND) may mimic various kinds of neurologic diseases and may coexist with other neurologic disorders. In cases overlapped by FND, it might be challenging to distinguish symptoms induced by FND and those induced by other underlying neurological disorders, especially when patients show no positive signs indicative of FND. Here, we present the case of a patient who was genetically diagnosed with paroxysmal kinesigenic dyskinesia (PKD). However, most of the patient's symptoms were considered to indicate FND. To our knowledge, there are no reports of FND overlapping PKD. This case illustrates the possibility that FND can coexist with and mimic symptoms of other diseases. It is necessary to rule out coexisting FND symptoms that may modify clinical presentations that cannot simply be explained by a recognized neurological disease.

A Curious Case of a Child With Recurrent Twisting Movements of Limbs

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent attacks of abnormal involuntary movements that are triggered by sudden movement, intention to move, or acceleration. A 10-year-old boy presented with paroxysmal, involuntary twisting movements of the left upper and lower limbs, precipitated by sudden body movements, lasting for 10-15 seconds and subsiding spontaneously. On examination, choreiform movements were observed, which were precipitated by sudden movements during some activities. The patient responded to carbamazepine with complete subsidence of the movements. The diagnosis of PKD was further confirmed by genetic testing. A high suspicion index helps in the prompt and early diagnosis of this rare entity.

The Pathogenesis of Paroxysmal Kinesigenic Dyskinesia: Current Concepts

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by recurrent and transient episodes of involuntary movements, including dystonia, chorea, ballism, or a combination of these, which are typically triggered by sudden voluntary movement. Disturbance of the basal ganglia-thalamo-cortical circuit has long been considered the cause of involuntary movements. Impairment of the gating function of the basal ganglia can cause an aberrant output toward the thalamus, which in turn leads to excessive activation of the cerebral cortex. Structural and functional abnormalities in the basal ganglia, thalamus, and cortex and abnormal connections between these brain regions have been found in patients with PKD. Recent studies have highlighted the role of the cerebellum in PKD. Insufficient suppression from the cerebellar cortex to the deep cerebellar nuclei could lead to overexcitation of the thalamocortical pathway. Therefore, this literature review aims to provide a comprehensive overview of the current research progress to explore the neural circuits and pathogenesis of PKD and promote further understanding and outlook on the pathophysiological mechanism of movement disorders. © 2023 International Parkinson and Movement Disorder Society.

[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.

PRRT2 Mutation and Serum Cytokines in Paroxysmal Kinesigenic Dyskinesia

OBJECTIVE

Paroxysmal kinesigenic dyskinesia (PKD) is a rare movement disorder PRRT2 gene mutations have been reported to cause PKD. However, the pathophysiological mechanism of PKD remains unclear, and it is unknown whether an inflammatory response is involved in the occurrence of this disease. We aimed to investigate the symptomatology, genotype, and serum cytokines of patients with PKD.

METHODS

We recruited 21 patients with PKD, including 7 with familial PKD and 14 with sporadic PKD. Their clinical features were investigated, and blood samples were collected, and PRRT2 mutations and cytokine levels were detected.

RESULTS

The mean age at PKD onset was 12.3±2.2 years old. Dystonia was the most common manifestation of dyskinesia, and the limbs were the most commonly affected parts. All attacks were induced by identifiable kinesigenic triggers, and the attack durations were brief (<1 min). Four different mutations from 9 probands were identified in 7 familial cases (71.4%) and 14 sporadic cases (28.6%). Two of these mutations (c.649dupC, c.620_621delAA) had already been reported, while other 2 (c.1018_1019delAA, c.1012+1G>A) were previously undocumented. The tumor necrosis factor (TNF)-α level in the PKD group was significantly higher than that in the age- and sex-matched control group (P=0.025). There were no significant differences in the interleukin (IL)-1β, IL-2R, IL-6, IL-8, or IL-10 levels between the two groups.

CONCLUSION

In this study, we summarized the clinical and genetic characteristics of PKD. We found that the serum TNF-α levels were elevated in patients clinically diagnosed with PKD, suggesting that an inflammatory response is involved in the pathogenesis of PKD.

TMEM151A Variants Cause Paroxysmal Kinesigenic Dyskinesia: A Large-Sample Study

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesias. Only one-third of PKD patients are attributed to proline-rich transmembrane protein 2 (PRRT2) mutations.

OBJECTIVE

We aimed to explore the potential causative gene for PKD.

METHODS

A cohort of 196 PRRT2-negative PKD probands were enrolled for whole-exome sequencing (WES). Gene Ranking, Identification and Prediction Tool, a method of case-control analysis, was applied to identify the candidate genes. Another 325 PRRT2-negative PKD probands were subsequently screened with Sanger sequencing.

RESULTS

Transmembrane Protein 151 (TMEM151A) variants were mainly clustered in PKD patients compared with the control groups. 24 heterozygous variants were detected in 25 of 521 probands (frequency = 4.80%), including 18 missense and 6 nonsense mutations. In 29 patients with TMEM151A variants, the ratio of male to female was 2.63:1 and the mean age of onset was 12.93 ± 3.15 years. Compared with PRRT2 mutation carriers, TMEM151A-related PKD were more common in sporadic PKD patients with pure phenotype. There was no significant difference in types of attack and treatment outcome between TMEM151A-positive and PRRT2-positive groups.

CONCLUSIONS

We consolidated mutations in TMEM151A causing PKD with the aid of case-control analysis of a large-scale WES data, which broadens the genotypic spectrum of PKD. TMEM151A-related PKD were more common in sporadic cases and tended to present as pure phenotype with a late onset. Extensive functional studies are needed to enhance our understanding of the pathogenesis of TMEM151A-related PKD. © 2021 International Parkinson and Movement Disorder Society.

Features Differ Between Paroxysmal Kinesigenic Dyskinesia Patients with PRRT2 and TMEM151A Variants

BACKGROUND

Mutations in proline-rich transmembrane protein 2 (PRRT2) are the major cause of paroxysmal kinesigenic dyskinesia (PKD). We recently reported transmembrane protein 151A (TMEM151A) mutations caused PKD. Herein, we aimed to conduct phenotypic comparisons of patients with PKD carrying PRRT2 variants, carrying TMEM151A variants, and carrying neither the PRRT2 nor TMEM151A variant.

METHODS

Sanger sequencing of PRRT2 and TMEM151A was performed, and phenotypic characteristics were analyzed.

RESULTS

In a cohort of 131 PKD probands (108 without PRRT2 variants and 23 newly recruited), five novel TMEM151A variants were identified and one (c.647C > A) occurred de novo. Together with our previous studies, PRRT2 and TMEM151A variants accounted for 34.7% (85/245) and 6.9% (17/245) of PKD probands, respectively. Compared with patients carrying PRRT2 variants, those with TMEM151A variants tended to exbibit dystonia with shorter durations, have no history of benign infantile epilepsy, and have residual attacks/aura when treated with carbamazepine/oxcarbazepine.

CONCLUSIONS

Patients with TMEM151A variants have different features from patients with PRRT2 variants. © 2022 International Parkinson and Movement Disorder Society.

Paroxysmal Kinesigenic Dyskinesia Masquerading as Dissociative Disorder: A Case Report on Pseudo-Dissociation

Movement disorders are common presentations to psychiatry and neurology clinics in general hospitals. Many a times, liaison between psychiatry and neurology helps in determining the exact etiology and diagnosis of rare movement disorders. Paroxysmal dyskinesia is a group of disorders caused by a genetic mutation. It is one of the rare presentations among dyskinetic disorders but often encountered by psychiatrists due to the psychogenic nature of episodes and apparently normal neurological findings in-between the episodes. Liaison work with a neurologist is of great importance rather than misdiagnosing them as a dissociative or psychogenic movement disorder. Unawareness of their presentation can lead to repeated consultations, unwarranted psychotherapies, and can create a sense of therapeutic nihilism among the treating psychiatrists. Predominantly four different variants are described in the literature under this group and new classification has been proposed recently. We encountered a case of paroxysmal kinesigenic dyskinesia with obstructive sleep apnea masquerading as a dissociative disorder.

Case Report: Long-Term Suppression of Paroxysmal Kinesigenic Dyskinesia After Bilateral Thalamotomy

Background: Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by transient dyskinetic movements, including dystonia, chorea, or both, triggered by sudden voluntary movements. Carbamazepine and other antiepileptic drugs (AEDs) are widely used in the treatment of PKD, and they provide complete remission in 80–90% of medically treated patients. However, the adverse effects of AEDs include drowsiness and dizziness, which interfere with patients' daily lives. For those with poor compatibility with AEDs, other treatment approaches are warranted.

Case Report: A 19-year-old man presented to our institute with right hand and foot dyskinesia. He had a significant family history of PKD; his uncle, grandfather, and grandfather's brother had PKD. The patient first experienced paroxysmal involuntary left hand and toe flexion with left forearm pronation triggered by sudden voluntary movements at the age of 14. Carbamazepine (100 mg/day) was prescribed, which led to a significant reduction in the frequency of attacks. However, carbamazepine induced drowsiness, which significantly interfered with his daily life, especially school life. He underwent right-sided ventro-oral (Vo) thalamotomy at the age of 15, which resulted in complete resolution of PKD attacks immediately after the surgery. Four months after the thalamotomy, he developed right elbow, hand, and toe flexion. He underwent left-sided Vo thalamotomy at the age of 19. Immediately after the surgery, the PKD attacks resolved completely. However, mild dysarthria developed, which spontaneously resolved within three months. Left-sided PKD attacks never developed six years after the right Vo thalamotomy, and right-sided PKD attacks never developed two years after the left Vo thalamotomy without medication.

Conclusion: The present case showed long-term suppression of bilateral PKDs after bilateral thalamotomy, which led to drug-free conditions.

Penetrance estimation of PRRT2 variants in paroxysmal kinesigenic dyskinesia and infantile convulsions

Proline-rich transmembrane protein 2 (PRRT2) is the leading cause of paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy (BFIE), and infantile convulsions with choreoathetosis (ICCA). Reduced penetrance of PRRT2 has been observed in previous studies, whereas the exact penetrance has not been evaluated well. The objective of this study was to estimate the penetrance of PRRT2 and determine its influencing factors. We screened 222 PKD index patients and their available relatives, identified 39 families with pathogenic or likely pathogenic (P/LP) PRRT2 variants via Sanger sequencing, and obtained 184 PKD/BFIE/ICCA families with P/LP PRRT2 variants from the literature. Penetrance was estimated as the proportion of affected variant carriers. PRRT2 penetrance estimate was 77.6% (95% confidence interval (CI) 74.5%-80.7%) in relatives and 74.5% (95% CI 70.2%-78.8%) in obligate carriers. In addition, we first observed that penetrance was higher in truncated than in non-truncated variants (75.8% versus 50.0%, P = 0.01), higher in Asian than in Caucasian carriers (81.5% versus 68.5%, P = 0.004), and exhibited no difference in gender or parental transmission. Our results are meaningful for genetic counseling, implying that approximately three-quarters of PRRT2 variant carriers will develop PRRT2-related disorders, with patients from Asia or carrying truncated variants at a higher risk.

Cerebellar spreading depolarization mediates paroxysmal movement disorder

Paroxysmal kinesigenic dyskinesia (PKD) is the most common paroxysmal dyskinesia, characterized by recurrent episodes of involuntary movements provoked by sudden changes in movement. Proline-rich transmembrane protein 2 (PRRT2) has been identified as the major causative gene for PKD. Here, we report that PRRT2 deficiency facilitates the induction of cerebellar spreading depolarization (SD) and inhibition of cerebellar SD prevents the occurrence of dyskinetic movements. Using Ca²⁺ imaging, we show that cerebellar SD depolarizes a large population of cerebellar granule cells and Purkinje cells in Prrt2-deficient mice. Electrophysiological recordings further reveal that cerebellar SD blocks Purkinje cell spiking and disturbs neuronal firing of the deep cerebellar nuclei (DCN). The resultant aberrant firing patterns in DCN are tightly, temporally coupled to dyskinetic episodes in Prrt2-deficient mice. Cumulatively, our findings uncover a pivotal role of cerebellar SD in paroxysmal dyskinesia, providing a potent target for treating PRRT2-related paroxysmal disorders.

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.

The Spectrum of PRRT2-Associated Disorders: Update on Clinical Features and Pathophysiology

Mutations in the PRRT2 (proline-rich transmembrane protein 2) gene have been identified as the main cause of an expanding spectrum of disorders, including paroxysmal kinesigenic dyskinesia and benign familial infantile epilepsy, which places this gene at the border between epilepsy and movement disorders. The clinical spectrum has largely expanded to include episodic ataxia, hemiplegic migraine, and complex neurodevelopmental disorders in cases with biallelic mutations. Prior to the discovery of PRRT2 as the causative gene for this spectrum of disorders, the sensitivity of paroxysmal kinesigenic dyskinesia to anticonvulsant drugs regulating ion channel function as well as the co-occurrence of epilepsy in some patients or families fostered the hypothesis this could represent a channelopathy. However, recent evidence implicates PRRT2 in synapse functioning, which disproves the "channel hypothesis" (although PRRT2 modulates ion channels at the presynaptic level), and justifies the classification of these conditions as synaptopathies, an emerging rubric of brain disorders. This review aims to provide an update of the clinical and pathophysiologic features of PRRT2-associated disorders.

Disruption of gray matter morphological networks in patients with paroxysmal kinesigenic dyskinesia

This study explores the topological properties of brain gray matter (GM) networks in patients with paroxysmal kinesigenic dyskinesia (PKD) and asks whether GM network features have potential diagnostic value. We used 3D T1-weighted magnetic resonance imaging and graph theoretical approaches to investigate the topological organization of GM morphological networks in 87 PKD patients and 115 age- and sex-matched healthy controls. We applied a support vector machine to GM morphological network matrices to classify PKD patients versus healthy controls. Compared with the HC group, the GM morphological networks of PKD patients showed significant abnormalities at the global level, including an increase in characteristic path length (Lp) and decreases in local efficiency (Eloc ), clustering coefficient (Cp), normalized clustering coefficient (γ), and small-worldness (σ). The decrease in Cp was significantly correlated with disease duration and age of onset. The GM morphological networks of PKD patients also showed significant changes in nodal topological characteristics, mainly in the basal ganglia-thalamus circuitry, default-mode network and central executive network. Finally, we used the GM morphological network matrices to classify individuals as PKD patients versus healthy controls, achieving 87.8% accuracy. Overall, this study demonstrated disruption of GM morphological networks in PKD, which might extend our understanding of the pathophysiology of PKD; further, GM morphological network matrices might have the potential to serve as network neuroimaging biomarkers for the diagnosis of PKD.

Paroxysmal kinesigenic dyskinesia associated with a novel POLG variant: A case report

INTRODUCTION

Paroxysmal kinesigenic dyskinesia (PKD) is a rare neurological disease characterized by recurrent dyskinesia or choreoathetosis triggered by sudden movements. Pathogenic variants in PRRT2 are the main cause of PKD. However, only about half of clinically diagnosed PKD patients have PRRT2 mutations, indicating that additional undiscovered causative genes could be implicated. PKD associated with POLG variant has not been reported.

PATIENT CONCERNS

A 14-year-old boy presented with a 2-month history of involuntary dystonic movements triggered by sudden activities. He was conscious during the attacks. Neurological examination, laboratory tests, brain magnetic resonance imaging (MRI), electroencephalogram (EEG) were all normal. Genetic analysis showed a novel variant of POLG (c.440G>T, p.Ser147Ile), which was considered to be a likely pathogenic variant in this case.

DIAGNOSES

The patient was diagnosed with PKD.

INTERVENTIONS

Low dose carbamazepine was used orally for treatment.

OUTCOMES

The patient achieved complete resolution of symptoms without any dyskinesia during the 6-month follow up.

CONCLUSION

Our study identified the novel POLG variant (c.440G>T, p.Ser147Ile) to be a likely pathogenic variant in PKD.

A Child Who Suddenly Freezes While Trying to Cross Crosswalks-Unique Clinical Manifestation of Paroxysmal Kinesigenic Dyskinesia: A Case Report

(1) Background: We report the case of a patient with a unique clinical presentation of inability to cross crosswalks due to paroxysmal kinesigenic dyskinesia (PKD). (2) Case presentation: A 14-year-old boy presented with the inability to move his right leg at gait initiation from the standing position. This episode lasted for approximately 20–30 s and manifested 1–3 times a day. The difficulty in gait initiation usually occurred when the patient tried to cross crosswalks when the traffic light turned from red to blue. His right arm stiffened occasionally while trying to write with a pencil and eat food with a spoon or chopsticks. Other neurological manifestations and pain were absent during these episodes. No neurological symptoms were observed between the attacks. Brain magnetic resonance imaging did not reveal any abnormalities. A next-generation sequencing study revealed a pathological variant in the proline-rich transmembrane protein 2 (PRRT2) gene. The patient was diagnosed with PKD. His symptoms disappeared completely after treatment with carbamazepine (100 mg/day). (3) Conclusions: The symptoms of PKD can be successfully controlled using antiepileptic medications. Therefore, clinicians should be aware of the clinical manifestations of PKD to provide appropriate treatment.

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.

Paroxysmal dyskinesia and epilepsy in pseudohypoparathyroidism

Background

Paroxysmal kinesigenic dyskinesia (PKD) and epilepsy share common pathogenic mechanisms but their pathophysiological connections remain unknown. Our study reports an individual with both disorders as a consequence of pseudohypoparathyroidism (PHP). This observation suggests potential shared pathophysiological mechanisms between PKD and epilepsy.

Methods

We report the case of a 15‐year‐old male with pre‐diagnosed PKD and symptomatic epilepsy. We recorded the symptoms and carried out comprehensive biochemical, genetic, imaging, and EEG analyses to examine the characteristics and potentially shared etiology of these conditions.

Results

In this case, the patient's PKD and symptomatic epilepsy were secondary to pseudohypoparathyroidism (PHP). The patient had a seven‐year history of intermittent, involuntary paroxysmal episodic movements, and a six‐year history of a loss of consciousness with convulsions. The electroencephalography results showed that the paroxysmal low and medium amplitude slow waves, isolated sharp waves, and sharp slow‐wave release occurred in the right prefrontal temporal cortex. Serum analysis indicated a calcium concentration of 1.91 mmol/L, a phosphorus concentration of 2.68 mmol/L, an alkaline phosphatase concentration of 114 IU/L, and a parathyroid hormone concentration of 109 pg/ml. Computerized tomography and magnetic resonance imaging results showed multiple calcifications in the bilateral frontal and parietal lobe cortex, bilateral thalamus, basal ganglia, and centrum semiovale. Furthermore, GNAS methylation abnormalities were discovered during methylation testing. There was no recurrence of abnormal movements or epileptic seizures, and calcium concentrations returned to healthy levels, following the pharmacological treatment of PHP.

Conclusion

In this case, PKD and symptomatic epilepsy were caused by PHP. This report underscores the importance of looking for biochemical abnormalities in PKD and symptomatic epilepsy patients. We suggest that all such intractable epilepsy seizure patients should be screened for PHP.

Brain structural connectome in relation to PRRT2 mutations in paroxysmal kinesigenic dyskinesia

This study explored the topological characteristics of brain white matter structural networks in patients with Paroxysmal Kinesigenic Dyskinesia (PKD), and the potential influence of the brain network stability gene PRRT2 on the structural connectome in PKD. Thirty‐five PKD patients with PRRT2 mutations (PKD‐M), 43 PKD patients without PRRT2 mutations (PKD‐N), and 40 demographically‐matched healthy control (HC) subjects underwent diffusion tensor imaging. Graph theory and network‐based statistic (NBS) approaches were performed; the topological properties of the white matter structural connectome were compared across the groups, and their relationships with the clinical variables were assessed. Both disease groups PKD‐M and PKD‐N showed lower local efficiency (implying decreased segregation ability) compared to the HC group; PKD‐M had longer characteristic path length and lower global efficiency (implying decreased integration ability) compared to PKD‐N and HC, independently of the potential effects of medication. Both PKD‐M and PKD‐N had decreased nodal characteristics in the left thalamus and left inferior frontal gyrus, the alterations being more pronounced in PKD‐M patients, who also showed abnormalities in the left fusiform and bilateral middle temporal gyrus. In the connectivity characteristics assessed by NBS, the alterations were more pronounced in the PKD‐M group versus HC than in PKD‐N versus HC. As well as the white matter alterations in the basal ganglia‐thalamo‐cortical circuit related to PKD with or without PRRT2 mutations, findings in the PKD‐M group of weaker small‐worldness and more pronounced regional disturbance show the adverse effects of PRRT2 gene mutations on brain structural connectome.

Novel mutation of the PRRT2 gene in two cases of paroxysmal kinesigenic dyskinesia: Two case reports

Paroxysmal kinesigenic dyskinesia (PKD) is a rare condition characterized by recurrent brief episodes of dystonia, chorea, athetosis or any combination of these, without alterations of consciousness. The proline-rich transmembrane protein 2 (PRRT2) gene has been widely investigated as a causative gene of PKD. To date, a cluster of pathogenic variants associated with PKD have been identified in the PRRT2 gene. In the present case report, two Chinese patients with sporadic PKD are discussed. Genetic analysis revealed a de novo heterozygous missense mutation, c.955G>T (p.Val319Leu) in exon 3 of the PRRT2 gene. Compared with the commonly reported clinical manifestation of PRRT2-associated PKD, the patients in this report showed several primary distinctive features. The mutations identified in the present analysis expand upon the mutation spectrum of the PRRT2 gene, and this newly found variant further reinforces the importance of the PRR2 gene in PKD.

The Phenotypic and Genetic Spectrum of Paroxysmal Kinesigenic Dyskinesia in China

BACKGROUND

Paroxysmal kinesigenic dyskinesia is a spectrum of involuntary dyskinetic disorders with high clinical and genetic heterogeneity. Mutations in proline-rich transmembrane protein 2 have been identified as the major pathogenic factor.

OBJECTIVES

We analyzed 600 paroxysmal kinesigenic dyskinesia patients nationwide who were identified by the China Paroxysmal Dyskinesia Collaborative Group to summarize the clinical phenotypes and genetic features of paroxysmal kinesigenic dyskinesia in China and to provide new thoughts on diagnosis and therapy.

METHODS

The China Paroxysmal Dyskinesia Collaborative Group was composed of departments of neurology from 22 hospitals. Clinical manifestations and proline-rich transmembrane protein 2 screening results were recorded using unified paroxysmal kinesigenic dyskinesia registration forms. Genotype-phenotype correlation analyses were conducted in patients with and without proline-rich transmembrane protein 2 mutations. High-knee exercises were applied in partial patients as a new diagnostic test to induce attacks.

RESULTS

Kinesigenic triggers, male predilection, dystonic attacks, aura, complicated forms of paroxysmal kinesigenic dyskinesia, clustering in patients with family history, and dramatic responses to antiepileptic treatment were the prominent features in this multicenter study. Clinical analysis showed that proline-rich transmembrane protein 2 mutation carriers were prone to present at a younger age and have longer attack duration, bilateral limb involvement, choreic attacks, a complicated form of paroxysmal kinesigenic dyskinesia, family history, and more forms of dyskinesia. The new high-knee-exercise test efficiently induced attacks and could assist in diagnosis.

CONCLUSIONS

We propose recommendations regarding diagnostic criteria for paroxysmal kinesigenic dyskinesia based on this large clinical study of paroxysmal kinesigenic dyskinesia. The findings offered some new insights into the diagnosis and treatment of paroxysmal kinesigenic dyskinesia and might help in building standardized paroxysmal kinesigenic dyskinesia clinical evaluations and therapies. © 2020 International Parkinson and Movement Disorder Society.

Paroxysmal Dyskinesias in a PRRT2 Mutation Carrier

Background

Paroxysmal movement disorders are rare and heterogeneous genetic conditions characterized by the recurrence of transient involuntary movements.

Phenomenology Shown

The phenomenology of a paroxysmal kinesigenic dyskinesia in a young professional athlete.

Educational Value

Providing basic clinical and genetic elements for the early recognition and diagnosis of a rare movement disorder.

Falling After Starting Running in a Case of Myoclonus Epilepsy Associated with Ragged-red Fibers with a 8344A>G mtDNA Mutation

Myoclonus epilepsy associated with ragged-red fibers (MERRF) is traditionally characterized by myoclonus, generalized epilepsy and ragged-red fibers. We herein report a 42-year-old man who complained of falling after starting running, symptoms resembling those of paroxysmal kinesigenic dyskinesia. He showed only slight muscle weakness of the right quadriceps femoris. Muscle pathology and a genetic analysis identified him as having MERRF with a 8344A>G mtDNA mutation. We diagnosed his symptoms as having been caused by slight quadriceps femoris muscle weakness and exercise intolerance. This case suggests that mitochondrial myopathy should be considered in cases with strong muscle symptoms for muscle weakness.

16p11.2 deletion in patients with paroxysmal kinesigenic dyskinesia but without intellectual disability

INTRODUCTION

Mutations of the PRRT2 gene are the most common cause for paroxysmal kinesigenic dyskinesia. However, patients with negative PRRT2 mutations are not rare. The aim of this study is to determine whether copy number variant of PRRT2 gene is another potential pathogenic mechanism in the patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations.

METHODS

We screened PRRT2 copy number variants using the AccuCopy™ method in 29 patients with paroxysmal kinesigenic dyskinesia with negative PRRT2 point and frameshift mutations. Next-generation sequencing was used to determine the chromosomal deletion sites in patients with PRRT2 copy number variants, and to exclude mutations in other known causative genes for paroxysmal kinesigenic dyskinesia.

RESULTS

Two sporadic patients with negative PRRT2 point and frameshift mutations (6.9%) were identified to have de novo PRRT2 copy number deletions (591 and 832 Kb deletions located in 16p11.2). The two patients presented with pure paroxysmal kinesigenic dyskinesia and paroxysmal kinesigenic dyskinesia and benign infantile convulsions, respectively. They had normal intelligence and neuropsychiatric development, in contrast to those previously reported with 16p11.2 deletions complicated with neuropsychiatric disorders. No correlation between the deletion ranges and phenotypic variations was found.

CONCLUSION

16p11.2 deletions play causative roles in paroxysmal kinesigenic dyskinesia, especially for sporadic cases. Our findings extend the phenotype of 16p11.2 deletions to pure paroxysmal kinesigenic dyskinesia. Screening for 16p11.2 deletions should thus be included in genetic evaluations for patients with paroxysmal kinesigenic dyskinesia.

Aberrant Sensory Gating of the Primary Somatosensory Cortex Contributes to the Motor Circuit Dysfunction in Paroxysmal Kinesigenic Dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) is conventionally regarded as a movement disorder (MD) and characterized by episodic hyperkinesia by sudden movements. However, patients of PKD often have sensory aura and respond excellently to antiepileptic agents. PRRT2 mutations, the most common genetic etiology of PKD, could cause epilepsy syndromes as well. Standing in the twilight zone between MDs and epilepsy, the pathogenesis of PKD is unclear. Gamma oscillations arise from the inhibitory interneurons which are crucial in the thalamocortical circuits. The role of synchronized gamma oscillations in sensory gating is an important mechanism of automatic cortical inhibition. The patterns of gamma oscillations have been used to characterize neurophysiological features of many neurological diseases, including epilepsy and MDs. This study was aimed to investigate the features of gamma synchronizations in PKD. In the paired-pulse electrical-stimulation task, we recorded the magnetoencephalographic data with distributed source modeling and time-frequency analysis in 19 patients of newly-diagnosed PKD without receiving pharmacotherapy and 18 healthy controls. In combination with the magnetic resonance imaging, the source of gamma oscillations was localized in the primary somatosensory cortex. Somatosensory evoked fields of PKD patients had a reduced peak frequency (p < 0.001 for the first and the second response) and a prolonged peak latency (the first response p = 0.02, the second response p = 0.002), indicating the synchronization of gamma oscillation is significantly attenuated. The power ratio between two responses was much higher in the PKD group (p = 0.013), indicating the incompetence of activity suppression. Aberrant gamma synchronizations revealed the defective sensory gating of the somatosensory area contributes the pathogenesis of PKD. Our findings documented disinhibited cortical function is a pathomechanism common to PKD and epilepsy, thus rationalized the clinical overlaps of these two diseases and the therapeutic effect of antiepileptic agents for PKD. There is a greater reduction of the peak gamma frequency in PRRT2-related PKD than the non-PRRT PKD group (p = 0.028 for the first response, p = 0.004 for the second response). Loss-of-function PRRT2 mutations could lead to synaptic dysfunction. The disinhibiton change on neurophysiology reflected the impacts of PRRT2 mutations on human neurophysiology.

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.

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.

[Clinical manifestations and genetic diagnosis of paroxysmal kinesigenic dyskinesia]

The clinical manifestations of five children with paroxysmal kinesigenic dyskinesia (PKD) were retrospectively analyzed and their gene mutations were analyzed by high-throughput sequencing and chromosome microarray. The 5 patients consisted of 4 males and 1 female and the age of onset was 6-9 years. Dyskinesia was induced by sudden turn movement, scare, mental stress, or other factors. These patients were conscious and had abnormal posture of unilateral or bilateral extremities, athetosis, facial muscle twitching, and abnormal body posture. The frequency of onset ranged from 3-5 times a month to 2-7 times a day, with a duration of <30 seconds every time. Electroencephalography showed no abnormality in these patients. Three patients had a family history of similar disease. The high-throughput sequencing results showed that a heterozygous mutation in the PRRT2 gene, c.649_650insC (p.R217PfsX8), was found in two patients; the mutation c.436C>T (p.P146S) was found in one patient; a splice site mutation, IVS2-1G>A, was found in one patient. The two mutations c.436C>T and IVS2-1G>A had not been reported previously. The chromosome microarray analysis was performed in one patient with negative results of gene detection, and the chromosome 16p11.2 deletion (0.55 Mb) was observed. Low-dose carbamazepine was effective for treatment of the 5 patients. PKD is a rare neurological disease. The detection of the PRRT2 gene by multiple genetic analysis can help the early diagnosis of PKD.

Paroxysmal Kinesigenic Dyskinesia as the Presenting and Only Manifestation of Multiple Sclerosis after Eighteen Months of Follow-Up

Other than tremor, movement disorders are uncommon in multiple sclerosis. Among these uncommon clinical manifestations, paroxysmal kinesigenic dyskinesia is the most frequently reported. It is characterized by episodic attacks of involuntary movements that are induced by repetitive or sudden movements, startling noise or hyperventilation. The diagnosis is essentially clinical and based on a good observation of the attacks. It is very easy to misdiagnose it. We describe the case of a young female patient who presented paroxysmal kinesigenic dyskinesia as the first and only clinical manifestation of multiple sclerosis, with no recurrence of attacks nor any other neurologic symptom after eighteen months of follow-up.

A case of paroxysmal kinesigenic dyskinesia which exhibited the phenotype of anxiety disorder

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is a rare heritable neurologic disorder characterized by attacks of involuntary movement induced by sudden voluntary movements. No previous reports have described cases showing comorbidity with psychiatric disease or symptoms. In this case, we showed a patient with PKD who exhibited several manifestations of anxiety disorder.

CASE

A 35-year-old Japanese man with PKD had been maintained on carbamazepine since he was 16 years of age without any attacks. However, 10 years before this referral, he became aware of a feeling of breakdown in his overall physical functions. He had then avoided becoming familiar with people out of concern that his physical dysfunctions might be perceived in a negative light. One day he was referred by the neurologic department at our hospital to the Department of Psychiatry because of severe anxiety and hyperventilation triggered by carbamazepine. We treated with escitalopram, aripiprazole, and ethyl loflazepate. Both his subjective physical condition and objective expressions subsequently showed gradual improvement. At last, the feelings of chest compression and anxiety entirely disappeared. Accordingly, increases in plasma monoamine metabolite levels were observed, and the c.649dupC mutation, which has been found in most Japanese PKD families, was detected in his proline-rich transmembrane protein 2 gene.

CONCLUSION

This is the first report to describe psychiatric comorbidities or symptoms in a PKD case. The efficacy of psychotropic medication used in this case, the resulting changes in plasma monoamine metabolite levels, and the recent advances in the molecular understanding of PKD suggested slight, but widespread alterations to the neurotransmitter systems in the brain.

Atypical Manifestations in Glut1 Deficiency Syndrome

Glucose transporter type 1 deficiency syndrome is a genetically determined, treatable, neurologic disorder that is caused by an insufficient transport of glucose into the brain. It is caused by a mutation in the SCL2A1 gene, which is so far the only known to be associated with this condition. Glucose transporter type 1 deficiency syndrome consists of a wide clinical spectrum that usually presents with cognitive impairment, epilepsy, paroxysmal exercise-induced dyskinesia, acquired microcephaly, hemolytic anemia, gait disturbance, and dyspraxia in different combinations. However, there are other clinical manifestations that we consider equally peculiar but that have so far been poorly described in literature. In this review, supported by a video contribution, we will accurately describe this type of clinical manifestation such as oculogyric crises, weakness, paroxysmal kinesigenic and nonkinesigenic dyskinesia in order to provide an additional instrument for a correct, rapid diagnosis.

Reduced Penetrance of PRRT2 Mutation in a Chinese Family With Infantile Convulsion and Choreoathetosis Syndrome

Paroxysmal kinesigenic dyskinesia is a rare episodic movement disorder that can be isolated or associated with benign infantile seizures as part of choreoathetosis syndrome. Mutations in the PRRT2 gene have been recently identified as a cause of paroxysmal kinesigenic dyskinesia and infantile convulsion and choreoathetosis (ICCA). We reported a PRRT2 heterozygous mutation (c.604-607delTCAC, p.S202Hfs*25) in a 3-generation Chinese family with infantile convulsion and choreoathetosis and paroxysmal kinesigenic dyskinesia. The mutation was present in 5 family members, of which 4 were clinically affected and 1 was an obligate carrier with reduced penetrance of PRRT2. The affected carriers of this mutation presented with a similar type of infantile convulsion during early childhood and developed additional paroxysmal kinesigenic dyskinesia symptoms later in life. In addition, they all had a dramatic clinical response to oxcarbazepine/phenytoin therapy. Reduced penetrance of the PRRT2 mutation in this family could warrant genetic counseling.

Five cases of paroxysmal kinesigenic dyskinesia by genetic diagnosis

Paroxysmal kinesigenic dyskinesia (PKD) is an autosomal dominant disorder and PRRT2 is the causative gene of PKD. The aim of this study was to investigate PRRT2 mutations in patients who were clinically diagnosed with PKD. Nine PKD cases, including four familial cases and five sporadic cases, were selected. Peripheral blood was drawn after obtaining informed consent, and genomic DNA was extracted by a standard protocol. Sanger sequencing was performed for the screening of PRRT2 mutations. A total of five cases were detected to harbor PRRT2 mutations. Four familial cases carried a c.649dupC (p.Arg217Profs^*8) mutation, while one sporadic case and his asymptomatic father carried a c.133-136delCCAG (p.Pro45Argfs^*44) mutation. PRRT2 mutations were not identified in the remaining cases. The study further confirmed that PRRT2 was a causative gene of PKD and implied that PRRT2 mutation has incomplete penetrance.

Molecular analysis of PRRT2 gene in a case of paroxysmal kinesigenic dyskinesia patient

Paroxysmal kinesigenic dyskinesia (PKD) is an abnormal involuntary movement that is episodic or intermittent, with sudden onset, and the attacks are induced by sudden movement. Mutations in proline-rich transmembrane protein 2 (PRRT2) gene have been implicated in the cause of this disorder. This study presents a case of PKD on the basis of clinical findings supported and evidences obtained through a mutational analysis. Sequencing of all the exons of PRRT2 gene revealed a frameshift mutation (p.R217Pfs*8) in exon 2 and a novel transition mutation (c.244C > T) in 5′-untranslated region (UTR). Though mutations in PRRT2 gene are well-established in PKD, this study for the first time presents a novel transition mutation in the exon 2 region.

Thalamic involvement in paroxysmal kinesigenic dyskinesia: a combined structural and diffusion tensor MRI analysis

Alteration of basal ganglia-thalamocortical circuit has been hypothesized to play a role in the pathophysiology underlying paroxysmal kinesigenic dyskinesia (PKD). We investigated macrostructural and microstructural changes in PKD patients using structural and diffusion tensor magnetic resonance imaging (MRI) analyses. Twenty-five patients with idiopathic PKD and 25 control subjects were prospectively studied on a 3T magnetic resonance (MR) scanner. Cortical thickness analysis was used to evaluate cortical gray matter (GM) changes, and automated volumetry and shape analysis were used to assess volume changes and shape deformation of the subcortical GM structures, respectively. Tract-based spatial statistics (TBSS) was used to evaluate white matter integrity changes in a whole-brain manner, and region-of-interest (ROI) analysis of diffusion tensor metrics was performed in subcortical GM structures. Compared to controls, PKD patients exhibited a reduction in volume of bilateral thalami and regional shape deformation mainly localized to the anterior and medial aspects of bilateral thalami. TBSS revealed an increase in fractional anisotropy (FA) of bilateral thalami and right anterior thalamic radiation in patients relative to controls. ROI analysis also showed an increase in FA of bilateral thalami in patients compared to controls. We have shown evidence for thalamic abnormalities of volume reduction, regional shape deformation, and increased FA in patients with PKD. Our novel findings of concomitant macrostructural and microstructural abnormalities in the thalamus lend further support to previous observations indicating causal relationship between a preferential lesion in the thalamus and development of PKD, thus providing neuroanatomical basis for the involvement of thalamus within the basal ganglia-thalamocortical pathway in PKD.

Clinical and polygraphic study of familial paroxysmal kinesigenic dyskinesia with PRRT2 mutation

BACKGROUND

Paroxysmal kinesigenic dyskinesia is a neurological condition characterised by brief attacks of involuntary movements triggered by sudden voluntary movements.

METHODS

We describe the clinical, polygraphic, and genetic features of an Italian family with paroxysmal kinesigenic dyskinesia.

RESULTS

Paroxysmal kinesigenic dyskinesia manifested as brief choreoathetosic-dystonic attacks precipitated by sudden movements, varying in severity and frequency, amongst the four affected family members. The disorder follows an autosomal dominant transmission and affects female members. Mutation of SLC2A1, MR1, CACNA1A, and ATP1A2 genes was excluded by direct sequencing. Mutation analysis of the PRRT2 gene revealed a single nucleotide duplication, c.649dupC, resulting in the frameshift mutation p.Arg217Profs*8 in all affected members.

CONCLUSION

Paroxysmal kinesigenic dyskinesia is the most common type of paroxysmal movement disorder and is often misdiagnosed clinically as epilepsy. We describe a family with paroxysmal kinesigenic dyskinesia associated with PRRT2 gene mutation, mild intrafamilial clinical heterogeneity, and benign course. [Published with video sequences].

Paroxysmal Kinesigenic Dyskinesia-like Symptoms in a Patient with Tourette Syndrome

Background

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by episodic dystonia or choreiform movements provoked by sudden voluntary movement. PKD is not commonly reported in Tourette syndrome (TS). We describe a unique case of TS with PKD-like episodic dyskinesia that responded to carbamazepine.

Case Report

A 36-year-old male with long-standing TS developed paroxysmal “cramping”. Attacks were provoked by quick, sudden arm movements, which induced dystonic cramping, or by reaching overhead, which caused painful contraction of truncal muscles. The spells typically lasted 5–20 seconds and occurred multiple times daily. The patient’s mother suffered from intermittent dystonic toe curling. In view of the similarity of symptoms to PKD, carbamazepine was prescribed at 400 mg daily. The symptoms resolved completely. Inadvertent discontinuation led to relapse, and resumption led to recapture of benefit.

Discussion

This case demonstrates the possibility that PKD-like symptoms may co-occur with TS and may be responsive to carbamazepine.

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.