Paroxysmal kinesigenic choreoathetosis with abnormal electroencephalogram during attacks

Novel Locus for Paroxysmal Kinesigenic Dyskinesia Mapped to Chromosome 3q28-29

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent and brief attacks of dystonia or chorea precipitated by sudden movements. It can be sporadic or familial. Proline-Rich Transmembrane Protein 2 (PRRT2) has been shown to be a common causative gene of PKD. However, less than 50% of patients with primary PKD harbor mutations in PRRT2. The aim of this study is to use eight families with PKD to identify the pathogenic PRRT2 mutations, or possible novel genetic cause of PKD phenotypes. After extensive clinical investigation, direct sequencing and mutation analysis of PRRT2 were performed on patients from eight PKD families. A genome-wide STR and SNP based linkage analysis was performed in one large family that is negative for pathogenic PRRT2 mutations. Using additional polymorphic markers, we identified a novel gene locus on chromosome 3q in this PRRT2-mutation-negative PKD family. The LOD score for the region between markers D3S1314 and D3S1256 is 3.02 and we proposed to designate this locus as Episodic Kinesigenic Dyskinesia (EKD3). Further studies are needed to identify the causative gene within this locus.

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.

Successful control with carbamazepine of family with paroxysmal kinesigenic dyskinesia of PRRT2 mutation

Paroxysmal kinesigenic dyskinesia (PKD), a rare paroxysmal movement disorder often misdiagnosed as epilepsy, is characterized by recurrent, brief dyskinesia attacks triggered by sudden voluntary movement. Pathophysiological mechanism of PKD remains not well understood. Ion channelopathy has been suggested, since the disease responds well to ion channel blockers. Mutations in proline-rich transmembrane protein 2 (PRRT2) were recently identified in patients with familial PKD. To extend these genetic reports, we studied a family with clinical manifestations of familial PKD responding well to low dose carbamazepine. Therapeutic dose ranged from 1.5 to 2.0 mg/ kg/day, below that in seizure control. One insertion mutation c.649_650insC (p.P217fsX7) was identified in three patients of the family. This study avers PRRT2’s high sensitivity for PKD phenotype. Identification of genes underlying pathogenesis will enhance diagnosis and treatment. Function of PRRT2 and its role in PKD warrant further investigation.

Paroxysmal kinesigenic dyskinesia: cortical or non-cortical origin

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by involuntary dystonia and/or chorea triggered by a sudden movement. Cases are usually familial with an autosomal dominant inheritance. Hypotheses regarding the pathogenesis of PKD focus on the controversy whether PKD has a cortical or non-cortical origin. A combined familial trait of PKD and benign familial infantile seizures has been reported as the infantile convulsions and paroxysmal choreoathetosis (ICCA) syndrome. Here, we report a family diagnosed with ICCA syndrome with an Arg217STOP mutation. The index patient showed interictal EEG focal changes compatible with paroxysmal dystonic movements of his contralateral leg. This might support cortical involvement in PKD.

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.

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.

Paroxysmal kinesigenic choreoathetosis: evidence of linkage to the pericentromeric region of chromosome 16 in four Chinese families

BACKGROUND

Paroxysmal kinesigenic choreoathetosis (PKC) is an autosomal dominant condition characterized by abnormal involuntary movements precipitated by sudden movement. The pericentromeric region of chromosome 16 has been linked to PKC by several reports. This study was to localize and identify PKC gene in four Chinese PKC families.

METHODS

Genetic linkage mapping with eight markers spanning chromosome 16p12-q13 was performed in 43 family members. Genome-wide single nucleotide polymorphism (SNP) scans were performed on four individuals in Family 1 in which infantile convulsion (IC) was co-inherited with PKC.

RESULTS

Individuals in Family 1 presented with both IC and paroxysmal choreoathetosis (ICCA), and Families 2, 3, and 4 presented only with PKC. Evidence for linkage was found with a maximum two-point LOD score of 4.89 for D16S690 (theta = 0.0) and a maximum multipoint LOD score was 5.34 between D16S3080 and D16S3136. Haplotype analysis showed the disease locus was between D16S3093 and D16S3057. A total of 84 SNPs spanned on 16q12.1-q13 was not segregated with the PKC phenotype, which defined an unlinked region from rs9933187 to rs8044753. Thus, the critical region of the PKC gene is across the pericentromeric region of chromosome 16, and most likely maps to a region of 20.5 Mb (6.2 cM) between D16S3093 and rs9933187 (16p11.2-q12.1).

CONCLUSION

The assignment of the locus for PKC to the pericentromeric region of chromosome 16 is confirmed and putatively narrowed in the present study.

Kinesigenic attacks with ictal electroencephalographic abnormalities

We report on a 14-year 5-month-old male who had attacks similar to those of paroxysmal kinesigenic choreoathetosis. The attacks were elicited exclusively by sudden movements. On several occasions, these attacks were immediately followed by loss of consciousness or a seizure. Ictal electroencephalograms of his attacks without loss of consciousness or a seizure indicated 1.5-3.0 Hz activity in the left hemisphere. A small dosage of carbamazepine was remarkably effective in stopping the attacks. This case demonstrates that a thorough ictal electroencephalographic examination is indispensable for clarifying the pathophysiology of kinesigenic attacks. The relationship between paroxysmal kinesigenic choreoathetosis and supplementary motor area seizures is also discussed.

Paroxysmal kinesigenic dyskinesias

The paroxysmal dyskinesias (PxDs) are involuntary, intermittent movement disorders manifested by dystonia, chorea, athetosis, ballismus or any combination of these hyperkinetic disorders. Paroxysmal kinesigenic dyskinesia (PKD), one of the four main types of PxD, involves sudden attacks of dyskinesias induced by voluntary movements. PKD most commonly occurs sporadically or as an autosomal-dominant familial trait with variable penetrance. Many causes of secondary PKD are being recognized. The exact pathophysiology of the PxDs awaits further elucidation, although basal ganglia dysfunction appears to play a major role. Although the precise gene remains unknown, genetic linkage studies have isolated loci on chromosome 16, which colocalizes with the locus for familial infantile convulsions and paroxysmal choreoathetosis in some studies. The episodic nature of PKD and its relationship with other episodic diseases, such as epilepsy, migraine, and episodic ataxia, suggests channelopathy as a possible underlying etiology. PKD may remit spontaneously, but it also responds well to anticonvulsants as well as some other agents.

Genetic and clinical heterogeneity in paroxysmal kinesigenic dyskinesia: evidence for a third EKD gene

Paroxysmal kinesigenic dyskinesia (PKD) is characterised by paroxysms of choreic, dystonic, ballistic, or athetoid movements. The attacks typically last seconds to minutes in duration and are induced by sudden voluntary movement. PKD loci have been identified on chromosome 16. We present the clinical and genetic details of two British and an Indian family with PKD. Linkage to the PKD loci on chromosome 16 has been excluded in one of these families, providing evidence for a third loci for PKD. Detailed clinical descriptions highlight the presence of both adolescent and infantile seizures in some of the PKD families. This study attempts to clarify the relationship of adolescent and infantile seizures to PKD and provides evidence that PKD is both genetically and clinically heterogeneous.

Interictal and ictal EEG activity in the basal ganglia: an SEEG study in patients with temporal lobe epilepsy

PURPOSE

The interictal and ictal EEG activity in the basal ganglia in patients with temporal lobe epilepsy were studied during invasive EEG monitoring.

METHODS

Eight epilepsy surgery candidates, each with a proven mesiotemporal seizure-onset zone, participated in the study. We used two invasive EEG methods to determine the seizure-onset zone. In both methods, diagonal electrodes were targeted into the amygdalohippocampal complex via a frontal approach and were passed through the basal ganglia with several leads. We analyzed 16 partial epileptic seizures, four of which became secondarily generalized.

RESULTS

No epileptic interictal or ictal discharges were noticed in the basal ganglia. The interictal activity in the basal ganglia was a mixture of low-voltage beta activity and medium-voltage alpha-theta activity. When the ictal paroxysmal activity remained localized to the seizure-onset zone, the activity of the basal ganglia did not change. The spread of epileptic activity to other cortical structures was associated with the basal ganglia EEG slowing to a theta-delta range of 3-7 Hz. This slowing was dependent on the spread of ictal discharge within the ipsilateral temporal lobe (related to the investigated basal ganglia structures); alternatively, the slowing occurred in association with the regional spread of ictal activity from the mesiotemporal region to the temporal neocortex contralaterally to the investigated basal ganglia. Secondary generalization was associated with a further slowing of basal ganglia activity.

CONCLUSIONS

The basal ganglia do not generate specific epileptic EEG activity. Despite the absence of spikes, the basal ganglia participate in changing or reflect changes in the distribution of the ictal epileptic activity.

Co-occurrence of infantile epileptic seizures and childhood paroxysmal choreoathetosis in one family: clinical, EEG, and SPECT characterization of episodic events

The co-occurrence of infantile convulsions and childhood paroxysmal choreoathetosis (ICCA syndrome) has recently been reported in several families. The pattern of familial clustering observed is consistent with a single locus mutation which has been mapped onto the pericentromeric region of chromosome 16. We studied the main clinical, electroencephalogram (EEG), and single photon emission computed tomography (SPECT) characteristics of episodic events in a new family presenting clinical features similar to that described in the ICCA syndrome. In the first year of life, a mother and her two daughters suffered from rare afebrile seizures lasting from 30 seconds to 15 minutes. Ictal EEG recording in one daughter at 7 months of age showed bilateral polyspikes with a posterior predominance. In the three patients, epileptic seizures regressed within a few weeks, and never reoccurred. At the age of 7 and 12 years, respectively, the two daughters presented daily brief (20 seconds to 1 minute) involuntary choreoathetotic episodes. In 10 of these attacks, EEG did not show any epileptiform abnormalities. In both sisters, an ictal SPECT was performed during a choreoathetotic episode. Subtracting the ictal SPECT from the interictal SPECT coregistered to magnetic resonance imaging (MRI) revealed significant modifications in the local cerebral perfusion in the sensorimotor cortex, the supplementary motor areas, and pallidum. Carbamazepine completely suppressed paroxysmal dyskinesias. These observations, together with literature data, suggest that in this syndrome, depending on brain maturation, the same genetic abnormality may result in different paroxysmal neurological symptoms.

Gait epilepsy. A case report of gait-induced seizures

Reflex epilepsy includes a group of epileptic syndromes in which seizures are induced by a stimulus, either simple (visual, somatosensory, olfactory, auditory) or more complex (e.g., eating, thinking, reading). We document a case of reflex epilepsy in which focal seizures are triggered exclusively by gait. The patient is a young boy whose walking was impaired by abnormal motor phenomena on the left side. These phenomena were elicited by gait and were accompanied by a distinctive ictal pattern with centro-temporal discharges. After comparing this patient with others reported in the literature, we determined that he has an unusual type of reflex epilepsy for which we coined the term "gait epilepsy." This disorder must be considered when physicians are making a differential diagnosis in patients who have symptoms that suggest paroxysmal kinesigenic dystonia (PKD) or selective epileptic gait disorder.

Familial paroxysmal exercise-induced dyskinesia, epilepsy, and mental retardation in a family with autosomal dominant inheritance

Only few sporadic and familial cases of paroxysmal exercise-induced dyskinesia (PED) have been described in literature. PED associated with familial epilepsy has been rarely reported. We describe a family in which six members in different generations were affected by a long-lasting PED, with childhood onset in five cases. Fasting and stress were also precipitating factors. All the subjects, moreover, showed epileptic seizures during childhood and adolescence. In addition, in all cases a condition of mild mental retardation was also documented, associated in some cases, with irritable and impulsive behaviour. Clinical, neurophysiological, neuroimaging and neuropsychological findings were reported. The homogeneous recurrence of this particular clinical picture in members of three generations emphasised a common genetic basis. In our patients, PED is transmitted as an autosomal dominant trait, with age-dependent penetrance, without evidence of genetic anticipation. The neurophysiological findings suggest a condition of hyperexcitability in the muscular and brain membrane, due to a ion channels disorder.

Paroxysmal kinesigenic dyskinesia and infantile convulsions: clinical and linkage studies

OBJECTIVE

To clinically characterize affected individuals in families with paroxysmal kinesigenic dyskinesia (PKD), examine the association with infantile convulsions, and confirm linkage to a pericentromeric chromosome 16 locus.

BACKGROUND

PKD is characterized by frequent, recurrent attacks of involuntary movement or posturing in response to sudden movement, stress, or excitement. Recently, an autosomal dominant PKD locus on chromosome 16 was identified.

METHODS

The authors studied 11 previously unreported families of diverse ethnic background with PKD with or without infantile convulsions and performed linkage analysis with markers spanning the chromosome 16 locus. Detailed clinical questionnaires and interviews were conducted with affected and unaffected family members.

RESULTS

Clinical characterization and sampling of 95 individuals in 11 families revealed 44 individuals with paroxysmal dyskinesia, infantile convulsions, or both. Infantile convulsions were surprisingly common, occurring in 9 of 11 families. In only two individuals did generalized seizures occur in later childhood or adulthood. The authors defined a 26-cM region using linkage data in 11 families (maximum lod score 6.63 at theta = 0). Affected individuals in one family showed no evidence for a shared haplotype in this region, implying locus heterogeneity.

CONCLUSIONS

Identification and characterization of the PKD/infantile convulsions gene will provide new insight into the pathophysiology of this disorder, which spans the phenotypic spectrum between epilepsy and movement disorder.

Reciprocal inhibition between the forearm muscles in patients with paroxysmal kinesigenic dyskinesia

We measured the changes of forearm flexor H reflexes produced by conditioning radial nerve stimulation at delays of -2, 0, 2, 4, 7.5, 10, 25 and 75 ms in 10 patients with PKD and six with generalized seizure disorder. We compared the results with 12 normal volunteers. In the patients with PKD, we compared the amounts of reciprocal inhibition between the severely and the asymptomatic or mildly affected sides of arms. Follow-up studies were done in eight PKD patients after they responded to the anticonvulsant treatment. At each delay, patients with seizure disorders showed comparable amounts of changes with controls. Patients with PKD showed paradoxical facilitation at a delay of 0 ms, enhanced facilitation between 2 to 7.5 ms delays and attenuated inhibition at a delay of 75 ms. There were no significant differences in the amount of reciprocal inhibition according to the severity of clinical symptoms. Follow-up studies showed no significant changes of reciprocal inhibition compared to the baseline data. In PKD, paradoxical facilitation and enhanced first relative facilitation period may be caused by defective spinal interneurons. In addition to the defective reciprocal inhibition, abnormalities of supraspinal inputs seem to be involved in the genesis of PKD.

A 16-year-old with episodic hemisdystonia

The paroxysmal dyskinesias are a subset of the hyperkinetic movement disorders characterized by their episodic nature. Classification based on precipitating factors is helpful in considering treatment and prognosis. The clinical similarities with partial seizures are discussed. An approach to differential diagnosis, diagnostic evaluation, and treatment options are presented.

Multicenter study of paroxysmal dyskinesias in Japan--clinical and pedigree analysis

To investigate the clinical features of paroxysmal dyskinesias and carry out a pedigree analysis, we conducted a multicenter survey in Japan. A questionnaire was mailed to 229 medical institutions. A total of 150 patients with paroxysmal kinesigenic choreoathetosis (PKC), including 53 sporadic cases and 97 affected individuals from 32 pedigrees, were identified. The mean age of onset of PKC was 8.8 years, and 80% of the cases were men. Of the 32 pedigrees with familial occurrence, 18 (56%) were compatible with an autosomal-dominant inheritance (AD) with complete penetrance, and seven (22%) had AD with incomplete penetrance; the remaining seven were sibling recurrence cases with apparently healthy parents. In six of seven familial cases with incomplete penetrance, the disease gene was thought to be transmitted by clinically unaffected females. Paroxysmal dystonic choreoathetosis (PDC) was found in five cases, including two sporadic cases and three affected individuals from two pedigrees; the mean age of onset was 0.6 years, and a male predominance was noted (male:female = 4:1). There was one case of paroxysmal hypnogenic dyskinesia and one case of paroxysmal exertion-induced dyskinesia. There is an unexplained male predominance for paroxysmal dyskinesias. When the genetic defect of patients with paroxysmal dyskinesias is identified, the pathophysiology of the disease will become more clear.

Familial paroxysmal kinesigenic choreoathetosis: an electrophysiologic and genotypic analysis

PURPOSE

We report a pedigree of familial paroxysmal kinesigenic choreoathetosis (PKC) in which five of 18 members are affected. The pathophysiologic basis for PKC is still uncertain; reflex epilepsy versus dysfunction of basal ganglia. We examined (a) whether there were ictal discharges during the attacks, and (b) a linkage between PKC and possible DNA markers linked to several familial epileptic or movement disorders.

METHODS

Video-monitoring EEG was performed in two patients with PKC during attacks elicited by movements of the lower extremities. Blood samples for DNA studies were obtained from 15 members of the pedigree. Fourteen polymorphic markers on chromosomes 1p, 2q, 6p, 10q, and 20q were genotyped, and two-point lod scores were calculated for each marker under a dominant model.

RESULTS

No ictal discharges were found during the attacks in both patients. We could not obtain significant linkage of PKC with any marker examined.

CONCLUSIONS

The video-monitoring EEG findings in our cases strongly suggested that the etiology of PKC should be considered distinct from that of reflex epilepsy. However, the patients in this pedigree had experienced generalized convulsions in their infancies; thus we could not deny the possibility of an epileptogenic basis for PKC. There was no strong evidence for a linkage of the gene for PKC with the candidate regions on 1p, 2q, 6p, 10q, or 20q.

Clinical manifestations of 20 Taiwanese patients with paroxysmal kinesigenic dyskinesia

INTRODUCTION

We compared the clinical manifestations and response to medications between familial and sporadic patients with paroxysmal kinesigenic dyskinesia (PKD), and also between patients with autosomal dominant (AD) and autosomal recessive (AR) inheritance.

MATERIAL AND METHODS

This retrospective cohort study included 9 familial and 11 sporadic Taiwanese patients with PKD diagnosed during a 10-year period at one of two hospitals. The mean duration of follow-up was 3.8 +/- 2.7 years. Each patient was interviewed and their medical records, as well as videotape recordings of PKD attacks in 6 patients, were used for analysis. Patients were treated with either carbamazepine or phenytoin, and the efficacy of sodium valproate was tested in 5 patients.

RESULTS

No single distinguishing feature in terms of clinical manifestations or therapeutic response was found to differentiate among familial, and sporadic cases, or between AD and AR inheritance. Carbamazepine and phenytoin were superior to sodium valproate in treating both familial and sporadic PKD patients, and both drugs resulted in almost complete remission of attacks.

CONCLUSION

Our findings indicate that the sporadic and familiar forms of PKD, as well as the AR and AD inherited types, are similar in terms of clinical manifestations and response to treatment. The functional status and prognosis of our Taiwanese patients suggest that PKD is a relatively benign entity.

Paroxysmal kinesigenic choreoathetosis in Singapore and its relationship to epilepsy

OBJECTIVES

To study the clinical characteristics of paroxysmal kinesigenic choreoathetosis (PKC) in our local population and its relationship to epilepsy.

METHODS

We reviewed retrospectively 15 patients who were managed by neurologists in our department from 1982 to 1996. The literature was also reviewed to study the association between PKC and epilepsy.

RESULTS

In our study, all the cases were idiopathic. The male to female ratio was 14:1 with all major races represented. Sixty percent of our patients suffered dystonic posturing rather than chorea, during the attacks. Twenty-one percent had a family history of a similar disorder which appeared to be of autosomal dominant inheritance. The sporadic form (79%) predominated in Singapore. One had a history of febrile fits while two had a history of epilepsy. We reviewed the available literature and found five other patients with idiopathic PKC also suffering from epilepsy. Of the 83 patients reviewed, 8% had epilepsy. This further strengthens the relationship between the two conditions. All our patients responded well to phenytoin at doses between 100 and 400 mg/day.

CONCLUSION

PKC affected all three major races in our population with a high male to female ratio of 14:1. Seventy-nine percent of our cases were sporadic and 60% suffered dystonic posturing during attacks. Of the cases reviewed, 8% of patients with idiopathic PKC also had epilepsy.

Quantitative EEG analysis of depth electrode recordings from several brain regions of mutant hamsters with paroxysmal dystonia discloses frequency changes in the basal ganglia

Computerized EEG spectral analyses of depth electrode recordings from striatum (caudate/putamen; CPu), globus pallidus (GP), and parietal cortex (pCtx) were performed before and after dystonic attacks in freely moving mutant dt(sz) hamsters with paroxysmal dystonia. In these hamsters, sustained attacks of abnormal movements and postures can be reproducibly induced by stress, such as placing the animals in a new environment. Data recorded from mutant hamsters were compared with recordings from age-matched nondystonic control hamsters. The predominant EEG changes in CPu and GP of dystonic hamsters were significant decreases in the high-frequency beta2 range and there was a tendency to increase in delta and theta activities. These changes were seen both before and after onset of dystonic attacks, indicating a permanent disturbance of neural activities in the basal ganglia of dystonic animals. No such changes were seen in the pCtx. Furthermore, no epileptic or epileptiform activity was seen in any of the recordings, substantiating a previous notion from cortical and hippocampal recordings that paroxysmal dystonia in these mutant hamsters has no epileptogenic basis. The present finding of abnormal synchronization of neural activity in the CPu and GP of dystonic hamsters adds to the belief that the striatopallidal-thalamocortical circuit is the most likely site in which to search for the unknown defect in primary (idiopathic) dystonia. As suggested by this study, quantitative EEG analysis can increase the likelihood of detecting subtle EEG abnormalities in different types of idiopathic dystonia and thereby improves our understanding of the pathogenetic mechanisms of this movement disorder.

Proton MR spectroscopic findings in paroxysmal kinesigenic dyskinesia

Although paroxysmal kinesigenic dyskinesia (PKD) has characteristic clinical features, the pathophysiology of PKD has remained unknown. The purpose of this study was to investigate the pathophysiology of idiopathic PKD by performing proton magnetic resonance spectroscopy (1H-MRS) in five patients with idiopathic PKD. Three patients were familial and two sporadic. Single-voxel 1H-MRS was performed on a GE 1.5-T SIGNA MR system. Localized 1H-MR spectra were obtained from the basal ganglia (n = 5), thalamus (n = 3), and supplementary motor area (SMA; n = 4) using STEAM sequence (stimulated echo acquisition mode; TR = 3.0 sec, TE = 30 msec, 64 AVG, volume = 8 mL) or PRESS (point resolved spectroscopy; TR = 3.0 sec, TE = 135 msec, volume = 4 mL). Peak ratios of Cho/Cr (Cho: choline, Cr: creatine) and mI/Cr (mI: myoinositol) were decreased significantly in the unilateral basal ganglia of two patients. In one, decreased peak ratio of mI/Cr in the unilateral basal ganglia was the only abnormality. In the remaining two, there was no significant abnormality. 1H-MR spectra obtained from the thalamus and SMA were all within normal limits. In conclusion, these results suggest that underlying pathophysiological mechanism of PKD may be at least partially associated with the dysfunction of cholinergic system in the basal ganglia.

Familial infantile convulsions and paroxysmal choreoathetosis: a new neurological syndrome linked to the pericentromeric region of human chromosome 16

Benign infantile familial convulsions is an autosomal dominant disorder characterized by nonfebrile seizures, with the first attack occurring at age 3-12 mo. It is one of the rare forms of epilepsy that are inherited as monogenic Mendelian traits, thus providing a powerful tool for mapping genes involved in epileptic syndromes. Paroxysmal choreoathetosis is an involuntary-movement disorder characterized by attacks that occur spontaneously or are induced by a variety of stimuli. Classification is still elusive, and the epileptic nature of this movement disorder has long been discussed and remains controversial. We have studied four families from northwestern France in which benign infantile convulsions was inherited as an autosomal dominant trait together with variably expressed paroxysmal choreoathetosis. The human genome was screened with microsatellite markers regularly spaced, and strong evidence of linkage for the disease gene was obtained in the pericentromeric region of chromosome 16, with a maximum two-point LOD score, for D16S3133, of 6.76 at a recombination fraction of 0. Critical recombinants narrowed the region of interest to a 10-cM interval around the centromere. Our study provides the first genetic evidence for a common basis of convulsive and choreoathetotic disorders and will help in the understanding and classification of paroxysmal neurological syndromes.

Channelopathies: ion channel disorders of muscle as a paradigm for paroxysmal disorders of the nervous system

Some of the most common diseases in humans occur intermittently in people who are otherwise healthy and active. Such disorders include migraine headache, epilepsy, and cardiac arrhythmias. Because electrical signals are critical to the function of neurons, muscle cells, and heart cells, proteins that regulate electrical signaling in these cells are logical sites where abnormalities might lead to disease. All of these diseases have prominent genetic components. Difficulty in understanding these diseases arises from the complexity of the clinical phenotypes as well as from the genetic heterogeneity that is almost certain to exist. Therefore, early work in may laboratory was aimed at understanding the pathogenesis of rare disorders that are similar in their episodic nature. These disorders of muscle (the periodic paralyses), lead to attacks of weakness that occur intermittently in otherwise normal people. We, and others, have shown that hyperkalemic periodic paralysis (hyperKPP) and paramyotonia congenita (PC) result from mutations in a gene encoding a skeletal muscle sodium channel. We have also shown that hypokalemic periodic paralysis (hypoKPP) is caused by mutations in a gene encoding a voltage-gated calcium channel. The characterization of these diseases as channelopathies has served as a paradigm for other episodic disorders. One example is periodic ataxia, which results from mutations in voltage-gated potassium calcium channels. Long QT syndrome, an episodic cardiac dysrhythmia syndrome, is known to result from mutations in either voltage-gated sodium or potassium channels. We have recently mapped genes that cause a familial paroxysmal dyskinesia (non-kinesiogenic paroxysmal dystonia/choreoathetosis) in humans and a reflex epilepsy in mice. The similarities among all these disorders, including their episodic nature, precipitating factors, and therapeutic responses, are striking. Understanding gained from work in these rare monogenic episodic disorders is not only allowing characterization of the molecular and physiologic basis of these diseases, but may ultimately shed light on our understanding of the pathophysiology of more common and genetically complex disorders of the central nervous system.

Antidyskinetic drug therapy for pediatric movement disorders

The pharmacologic armamentarium used to treat dyskinesias in childhood is increasing. Anticonvulsant drugs as a class are still some of the broadest-spectrum antidyskinetic agents, probably because the class includes so many differently acting drugs or because dyskinesias are manifestations of subcortical electrical events. This group is enhanced by recent developments in gamma-aminobutyric acid and glutamate receptor pharmacology, which promise new antidyskinetic drugs. Other drugs acting at receptors for monoamines (dopamine, norepinephrine, and serotonin), acetylcholine, opioids, or histamine may provide symptomatic improvement. Fewer pharmacotherapies address the underlying pathophysiology of movement disorders. Of these, drugs or biologicals for immunomodulation are the most developed, but the group also includes antioxidants, cofactors, metabolic inhibitors, and chelators. There is potential for drugs that block the neurotoxic effects of glutamate to treat movement disorders and reverse or prevent brain injury. Peripheral blockade of focal dyskinesias through botulinum toxin offers a useful alternative to drugs in some patients.

Epilepsy or paroxysmal kinesigenic choreoathetosis?

Epileptic seizures induced by sudden movement and paroxysmal kinesigenic choreoathetosis (PKC) have often been confused in the past, owing to the close similarity of the attacks, the equally good response to anticonvulsants, and the frequent occurrence of epilepsy and PKC in the same family, or even in the same patient. The pathophysiology of PKC is still unclear and its relationship with epilepsy open to discussion. The sparing of consciousness and the lack of postictal phenomena are constant features of PKC, thus differentiating this syndrome from epilepsy. We report the case of an 8-year-old boy with frequent brief tonic attacks, without loss of consciousness, triggered by sudden movement. The neurologic examination, EEG and MRI did not help to differentiate between epilepsy and PKC. Only the occurrence of a longer seizure with clouding of consciousness and the recording of the postictal abnormalities on the EEG supported a diagnosis of reflex epilepsy induced by movement.

Paroxysmal choreoathetosis: an epileptic or non-epileptic disorder?

The pathophysiology of paroxysmal kinesigenic choreoathetosis (PKC) is controversial. Some classify it as a non-epileptic movement disorder, others consider PKC as a form of reflex-epilepsy but postulate that the epileptogenic source is within basal ganglia rather than in the cortex. An extensive invasive longterm monitoring in a girl with PKC demonstrated a consistent ictal discharge arising focally from the supplementary sensory-motor cortex (SMC), with a concomitant discharge recorded from the ipsilateral caudate nucleus, without significant spread to other neocortical areas. An hypothesis is presented to explain how a focal discharge within the supplementary motor cortex, demonstrated for the first time to occur in a patient with PKC, might cause phenomenologies distinct from the habitual SMC seizures and strongly suggesting a basal ganglia semeiology.

Paroxysmal kinesigenic choreoathetosis associated with prenatal brain damage

We describe a 15 year old patient with paroxysmal kinesigenic choreoathetosis. Neurological examinations revealed a paresis of the right arm and hand that was similar to ulnar nerve palsy, a right homonymous hemianopsia and an ocular movement disturbance of smooth pursuit to left. Attacks of dystonic spasms began abruptly, usually following running, and lasted less than 5 min. Magnetic resonance imaging displayed a linear area of increased signal in the T2-weighted images along the lateral margin to the left putamen, atrophies of the frontal and temporal opercula and a large porencephalic cyst in the left parieto-temporo-occipital region. A cerebral blood flow study with single photon emission computed tomography showed hypoperfusion of the lenticular nucleus and the regions corresponding to the atrophies and the porencephalic cyst. Electroencephalograms during the attacks could not demonstrate epileptic abnormality. Only the neuronal plasticity of an immature brain could explain the discrepancy between the observed huge lesions of the brain and the minor neurological symptoms present. Attacks of paroxysmal kinesigenic choreoathetosis might occur when the basal ganglia maturate to some extent, even if the lesions in the brain were caused before birth.

Diagnosis of childhood seizure disorders

Convulsive epilepsies are generally unmistakable. Absence epilepsies, which are easily recognized by the provocation of an episode during hyperventilation and by the typical features of the EEG, can be overdiagnosed, especially in the child who daydreams in class and has scattered, asymptomatic, epileptogenic EEG changes. As in adults, complex partial seizures in children can be difficult to distinguish from certain behaviors. Several types of benign childhood epilepsies need to be distinguished from the more intractable and lesional childhood epilepsies. Two common examples, benign rolandic epilepsy and benign occipital epilepsy, can be recognized by their unique EEG changes and clinical features. Juvenile myoclonic epilepsy generally does not remit spontaneously but should be recognized because it appears to respond to valproate. Some recurrent nonepileptic events seen in children can be mistaken for seizures, including shuddering attacks, paroxysmal vertigo, breath-holding spells, cardiogenic syncope, night terrors, and movement disorders, such as paroxysmal kinesigenic choreoathetosis.

Concurrent nocturnal and diurnal paroxysmal dystonia

The authors describe a case of a 15-year-old girl who presented with a progressive sequence of nocturnal dystonic episodes, generalized seizures, and diurnal dystonic episodes. A diagnosis of nocturnal paroxysmal dystonia has been proposed in view of the association between nocturnal episodes and epileptic seizures, while the diurnal episodes are atypical. Neurophysiological data recorded during critical episodes are reported. A linkage between dystonic attacks and epilepsy is hypothesized.