Autosomal recessive rolandic epilepsy with paroxysmal exercise-induced dystonia and writer's cramp: delineation of the syndrome and gene mapping to chromosome 16p12-11.2

Paroxysmal exercise-induced dyskinesia and epilepsy is due to mutations in SLC2A1, encoding the glucose transporter GLUT1

Paroxysmal exercise-induced dyskinesia (PED) can occur in isolation or in association with epilepsy, but the genetic causes and pathophysiological mechanisms are still poorly understood. We performed a clinical evaluation and genetic analysis in a five-generation family with co-occurrence of PED and epilepsy (n = 39), suggesting that this combination represents a clinical entity. Based on a whole genome linkage analysis we screened SLC2A1, encoding the glucose transporter of the blood-brain-barrier, GLUT1 and identified heterozygous missense and frameshift mutations segregating in this and three other nuclear families with a similar phenotype. PED was characterized by choreoathetosis, dystonia or both, affecting mainly the legs. Predominant epileptic seizure types were primary generalized. A median CSF/blood glucose ratio of 0.52 (normal >0.60) in the patients and a reduced glucose uptake by mutated transporters compared with the wild-type as determined in Xenopus oocytes confirmed a pathogenic role of these mutations. Functional imaging studies implicated alterations in glucose metabolism in the corticostriate pathways in the pathophysiology of PED and in the frontal lobe cortex in the pathophysiology of epileptic seizures. Three patients were successfully treated with a ketogenic diet. In conclusion, co-occurring PED and epilepsy can be due to autosomal dominant heterozygous SLC2A1 mutations, expanding the phenotypic spectrum associated with GLUT1 deficiency and providing a potential new treatment option for this clinical syndrome.

Paroxysmal dyskinesias in mice

Animal models of human disease are important tools for revealing the underlying mechanisms of pathophysiology and developing therapeutic strategies. Several unique mouse calcium channel mutants have been identified with nonepileptic, episodic dyskinetic movements that are phenotypically similar to human paroxysmal dyskinesias. In this report, video demonstrations of these motor attacks are provided for two previously described mouse mutants, tottering and lethargic, as well as a new one, rocker. Semiquantitative comparisons using two different rating scales reveal differences in attack morphology, severity, and duration among the strains. These mice provide three independent models of paroxysmal dyskinesia and support for prior proposals that channelopathies may underlie the human disorders.

Evaluating candidate genes in common epilepsies and the nature of evidence

Very few genetic associations for idiopathic epilepsy have been replicated and this has tempered enthusiasm for the results of genetic studies in epilepsy. What are the reasons for lack of replication? While type 1 error, population stratification, and multiple testing have been discussed extensively, the importance of genetic heterogeneity has been relatively neglected. In the first part of this review, we explore the sources of genetic heterogeneity and their importance for epilepsy genetic studies. In the second part, we review alternatives to the simple law of replication, revisiting Bradford Hill's guidelines for evidence of causality. A coherence perspective is applied to three examples. We conclude that adopting the perspective of integrating coherent and consistent evidence from different experimental approaches is a more appropriate requirement for proceeding to functional studies.

An autosomal dominant genetically heterogeneous variant of rolandic epilepsy and speech disorder

We report a three generation pedigree with 11 of 22 affected with a variant form of rolandic epilepsy, speech impairment, oromotor apraxia, and cognitive deficit. The core features comprised nocturnal rolandic seizures, interictal centrotemporal spike waves with early age of onset and late age of offset. The transmission of the phenotype was consistent with autosomal dominant inheritance, with variable expressivity but no evidence of anticipation. We found evidence that the seizure and speech traits may be dissociated. No abnormalities were found by cytogenetic analysis. Linkage analysis excluded loci at 11p, 15q, 16p12, and Xq22 for related phenotypes, suggesting genetic heterogeneity.

Nicotine-induced dystonic arousal complex in a mouse line harboring a human autosomal-dominant nocturnal frontal lobe epilepsy mutation

We generated a mouse line harboring an autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE) mutation: the alpha4 nicotinic receptor S248F knock-in strain. In this mouse, modest nicotine doses (1-2 mg/kg) elicit a novel behavior termed the dystonic arousal complex (DAC). The DAC includes stereotypical head movements, body jerking, and forelimb dystonia; these behaviors resemble some core features of ADNFLE. A marked Straub tail is an additional component of the DAC. Similar to attacks in ADNFLE, the DAC can be partially suppressed by the sodium channel blocker carbamazepine or by pre-exposure to a very low dose of nicotine (0.1 mg/kg). The DAC is centrally mediated, genetically highly penetrant, and, surprisingly, not associated with overt ictal electrical activity as assessed by (1) epidural or frontal lobe depth-electrode electroencephalography or (2) hippocampal c-fos-regulated gene expression. Heterozygous knock-in mice are partially protected from nicotine-induced seizures. The noncompetitive antagonist mecamylamine does not suppress the DAC, although it suppresses high-dose nicotine-induced wild-type-like seizures. Experiments on agonist-induced 86Rb+ and neurotransmitter efflux from synaptosomes and on alpha4S248Fbeta2 receptors expressed in oocytes confirm that the S248F mutation confers resistance to mecamylamine blockade. Genetic background, gender, and mutant gene expression levels modulate expression of the DAC phenotype in mice. The S248F mouse thus appears to provide a model for the paroxysmal dystonic element of ADNFLE semiology. Our model complements what is seen in other ADNFLE animal models. Together, these mice cover the spectrum of behavioral and electrographic events seen in the human condition.

Neuroanatomical substrates for paroxysmal dyskinesia in lethargic mice

The paroxysmal dyskinesias are a group of neurological disorders described by intermittent attacks of involuntary abnormal movements superimposed on a relatively normal baseline. The neuroanatomical substrates for these attacks are not fully understood, though available evidence from studies of affected people and animal models points to dysfunction in the basal ganglia or cerebellum. In the current studies, the anatomical basis for paroxysmal dyskinesias in lethargic mice was determined via histochemical methods sensitive to changes in regional brain activity followed by surgical elimination of the suspected source. Cytochrome oxidase histochemistry revealed increased activity in the red nucleus. Surgical removal of the cerebellum worsened ataxia but eliminated paroxysmal dyskinesias. These studies support the hypothesis that abnormal cerebellar output contributes to paroxysmal dyskinesias.

[A family with exercise-induced paroxysmal dystonia and childhood absence epilepsy]

INTRODUCTION

The boundary between epilepsy and paroxysmal dyskinesia appears to be less easy to delineate than previously believed. Reports of families showing both phenomena suggest a shared pathophysiology.

PATIENTS AND METHOD

A new family with autosomal dominant exercise-induced paroxysmal dystonia is reported.

RESULTS

Two family members also had childhood absence epilepsy, and one of them suffered from acute transient hemiplegia at age 10.

CONCLUSION

The association of epilepsy and paroxysmal dyskinesia has been rarely reported in the literature, and several loci have been identified. Absence epilepsy and exercise-induced paroxysmal dystonia appear to be very uncommon, although some reports mentioned the association in sporadic and familial cases. The involvement of ion channel genes in several transient neurological disorders supports the hypothesis of a common pathophysiological process underlying both the childhood absence seizure and the later paroxysmal dystonia.

Genetic Focal Epilepsies: State of the Art and Paths to the Future

The concept of genetic focal epilepsies is relatively new as compared to awareness of the importance of genetic factors in the generalized epilepsies. However, in the past decade, there has been increasing recognition of families with dominantly inherited partial epilepsies. Better definition of the phenotypes allows identification of distinct syndromes. The main familial focal epilepsies are autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE), familial mesial TLE (FMTLE), familial lateral TLE (FLTLE), and familial partial epilepsy with variable foci (FPEVF). The only genes identified so far are those for ADNFLE and FLTLE. In these disorders, functional studies are the next step and could provide advances leading to clarification of the pathophysiology as well as to new therapeutic strategies. At present, we can provide genetic counseling and a more accurate prognosis for most of the familial focal epilepsies. Greater awareness of the genetic basis in this group of disorders by the treating physicians is essential for identification of new families. This will allow further linkage studies, candidate gene screening, and identification of new genes, which will hopefully result in genetically based prevention and treatment.

No evidence of ATP1A2 involvement in 12 multiplex Italian families with benign familial infantile seizures

A missense mutation in the gene encoding the alpha(2) subunit of the Na(+),K(+) ATPase pump (ATP1A2) was found in a family with both familial hemiplegic migraine (FHM) and Benign Familial Infantile Seizures (BFIC). As it is still unclear whether ATP1A2 is responsible for pure BFIC syndromes, we checked mutations of the ATP1A2 gene in probands of 12 Italian multiplex families with pure BFIC, who were negative for mutations in the SCN2A gene. We screened the ATP1A2 gene by denaturing high performance liquid chromatography (D-HPLC) and direct sequencing of DNA fragments showing an aberrant elution pattern. We found one exonic variant and five intronic variants, none leading to significant amino acid changes or causing a modification of the physiological mRNA maturation. The ATP1A2 gene does not appear to be involved in the ethiopathogenesis of pure BFIC syndromes, at least in the explored Italian multiplex families. It could be either responsible of a minority of cases, or of complex syndromes where BFIC and FHM co-occur.

Clinical evaluation of idiopathic paroxysmal kinesigenic dyskinesia: new diagnostic criteria

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is a rare disorder characterized by short episodes of involuntary movement attacks triggered by sudden voluntary movements. Although a genetic basis is suspected in idiopathic cases, the gene has not been discovered. Establishing strict diagnostic criteria will help genetic studies.

METHODS

The authors reviewed the clinical features of 121 affected individuals, who were referred for genetic study with a presumptive diagnosis of idiopathic PKD.

RESULTS

The majority (79%) of affected subjects had a distinctive homogeneous phenotype. The authors propose the following diagnostic criteria for idiopathic PKD based on this phenotype: identified trigger for the attacks (sudden movements), short duration of attacks (<1 minute), lack of loss of consciousness or pain during attacks, antiepileptic drug responsiveness, exclusion of other organic diseases, and age at onset between 1 and 20 years if there is no family history (age at onset may be applied less stringently in those with family history). In comparing familial and sporadic cases, sporadic cases were more frequently male, and infantile convulsions were more common in the familial kindreds. Females had a higher remission rate than males. An infantile-onset group with a different set of characteristics was identified. A clear kinesigenic trigger was not elicited in all cases, antiepileptic response was not universal, and some infants had attacks while asleep.

CONCLUSIONS

The diagnosis of idiopathic paroxysmal kinesigenic dyskinesia (PKD) can be made based on historical features. The correct diagnosis has implications for treatment and prognosis, and the diagnostic scheme may allow better focus in the search for the PKD gene(s).

Calcium-sensitive potassium channelopathy in human epilepsy and paroxysmal movement disorder

The large conductance calcium-sensitive potassium (BK) channel is widely expressed in many organs and tissues, but its in vivo physiological functions have not been fully defined. Here we report a genetic locus associated with a human syndrome of coexistent generalized epilepsy and paroxysmal dyskinesia on chromosome 10q22 and show that a mutation of the alpha subunit of the BK channel causes this syndrome. The mutant BK channel had a markedly greater macroscopic current. Single-channel recordings showed an increase in open-channel probability due to a three- to fivefold increase in Ca(2+) sensitivity. We propose that enhancement of BK channels in vivo leads to increased excitability by inducing rapid repolarization of action potentials, resulting in generalized epilepsy and paroxysmal dyskinesia by allowing neurons to fire at a faster rate. These results identify a gene that is mutated in generalized epilepsy and paroxysmal dyskinesia and have implications for the pathogenesis of human epilepsy, the neurophysiology of paroxysmal movement disorders and the role of BK channels in neurological disease.

Channelopathy: hypothesis of a common pathophysiologic mechanism in different forms of paroxysmal dyskinesia

Paroxysmal dyskinesias are a rare heterogeneous group of neurologic disorders, characterized by transient sudden choreoathetoid or dystonic attacks without loss of consciousness. This study reports a family with six affected members in three generations, and two sporadic cases of paroxysmal dyskinesia. Familial cases of paroxysmal dyskinesia are affected by idiopathic long-lasting paroxysmal exertion-induced dyskinesia and the sporadic cases by idiopathic short-lasting paroxysmal kinesigenic dyskinesia. Familial cases also suffer from epilepsy, mainly of generalized type, with benign outcome; one sporadic case is affected by migraine. Results presented in this neurophysiologic study include electromyography, somatosensory evoked potentials by median nerve stimulation, somatosensory evoked potentials by posterior tibial nerve stimulation, motor evoked potentials by magnetic transcranial cortical stimulation, visual evoked potentials, brainstem auditory evoked potentials, blink reflex, reflex H, and electroencephalography. The clinical and neurophysiologic findings presented here suggest a condition of hyperexcitability at the muscular and brain level, perhaps as a result of an ion channel disorder, which is in agreement with reports in the literature.

Benign familial infantile convulsions: linkage to chromosome 16p12-q12 in 14 families

PURPOSE

Benign familial infantile convulsions (BFIC) is a form of idiopathic epilepsy. It is characterized by clusters of afebrile seizures occurring around the sixth month of life. The disease has a benign course with a normal development and rare seizures in adulthood. Previous linkage analyses defined three susceptibility loci on chromosomes 19q12-q13.11, 16p12-q12, and 2q23-31. However, a responsible gene has not been identified. We studied linkage in 16 further BFIC families.

METHODS

We collected 16 BFIC families, without an additional paroxysmal movement disorder, of German, Turkish, or Japanese origin with two to eight affected individuals. Standard two-point linkage analysis was performed.

RESULTS

The clinical picture included a large variety of seizure semiologies ranging from paleness and cyanosis with altered consciousness to generalized tonic-clonic seizures. Interictal EEGs showed focal epileptiform discharges in six patients, and three ictal EEGs in three distinct patients revealed a focal seizure onset in different brain regions. In all analyzed families, we found no evidence for linkage to the BFIC loci on chromosomes 19q and 2q, as well as to the known loci for benign familial neonatal convulsions on chromosomes 8q and 20q. In 14 of the families, the chromosome 16 locus could be confirmed with a cumulative maximum two-point lod score of 6.1 at marker D16S411, and the known region for BFIC could be narrowed to 22.5 Mbp between markers D16S690 and D16S3136.

CONCLUSIONS

Our data confirm the importance of the chromosome 16 locus for BFIC and may narrow the relevant interval.

Autosomal recessive idiopathic epilepsy in an inbred family from Turkey: identification of a putative locus on chromosome 9q32-33

PURPOSE

The study describes the clinical features of an inbred family from Turkey with three members affected by seizures and tests possible autosomal recessive (AR) inheritance by means of linkage analysis.

METHODS

Personal and family history was obtained from each subject, and general physical, neurologic, and EEG examinations were performed. A set of 382 fluorescence-labeled markers was used for the initial genome-wide search. A further set of 83 markers was used to map the locus precisely and to exclude the remaining genome.

RESULTS

Twelve individuals from three generations were examined. Two subjects were affected by idiopathic epilepsy, whereas, their brother experienced a single unprovoked generalized seizure. Two siblings affected by idiopathic epilepsy and their unaffected sister showed a photoparoxysmal response to photic stimulation. Nine family members reported migraine. The genome-wide search led to the identification of a unique homozygous, 15.1-cM region shared by subjects with seizures on chromosome 9q32-33 and providing a lod score of 2.9. This locus, however, was not associated with migraine in this pedigree.

CONCLUSIONS

The study suggests that idiopathic epileptic traits with AR inheritance might be underestimated in the general population and that inbred pedigrees may represent powerful tools for the identification of AR genes.

Monogenic idiopathic epilepsies

Major advances have recently been made in our understanding of the genetic bases of monogenic inherited epilepsies. Direct molecular diagnosis is now possible in numerous inherited symptomatic epilepsies. Progress has also been spectacular with respect to several idiopathic epilepsies that are caused by mutations in genes encoding subunits of ion channels or neurotransmitter receptors. Although these findings concern only a few families and sporadic cases, their potential importance is great, because these genes are implicated in a wide range of more common epileptic disorders and seizure types as well as some rare syndromes. Functional studies of these mutations, while leading to further progress in the neurobiology of the epilepsies, will help to refine genotype-phenotype relations and increase our understanding of responses to antiepileptic drugs. In this article, we review the clinical and genetic data on most of the idiopathic human epilepsies and epileptic contexts in which the association of epilepsy and febrile convulsions is genetically determined.

Genetics in epilepsy: transcultural perspectives

In the last two decades there have been many significant advances with regard to the genetics of human epilepsies. Knowledge of the mutations responsible for inherited human epilepsies not only will help in a better diagnosis and understanding of the mechanisms involved in epileptogenesis and their inheritance, but also will result in the development of better and safer antiepileptic drugs, discovery of novel therapeutic modalities, improved genetic counseling, and perhaps even prevention of epilepsies. The overall impact of these genetic discoveries across different populations and cultures will perhaps be beneficial to improving the lives of the millions affected by these diverse but common brain disorders.

[Movement disorders in childhood: classification and genetic update]

Abnormal movements are not unusual in childhood. Recent genetic progresses provide a new approach of childhood movement disorders. Several loci have been identified in paroxysmal dyskinesia, or in Gilles de la Tourette syndrome. A gene has been cloned in Hallervorden-Spatz syndrome, and a gene has recently been implicated in benign hereditary chorea. Considerable advances concern the genetic of dystonic syndromes: several chromosomal localizations have been identified, and several genes have been cloned. Genetic advances allow nosographic reclassification of some entities and offer new molecular tools for a more appropriate diagnosis. The increasing wealth of genetic knowledge will provide further insight in the understanding of abnormal movement disorders in childhood.

Post-traumatic paroxysmal exercise-induced dystonia: case report and review of the literature

A young Chinese man sustained a back injury in a motorcycle accident in 2000 and had left lower limb weakness due to a lumbosacral plexopathy, diagnosed clinically and electromyographically. With rehabilitation, he recovered full function, but developed paroxysmal dystonia of the left leg only with prolonged exertion. He responded well to oral baclofen, relapsed when he stopped taking it, and remains well on low dose maintenance therapy. Dystonia occurring after trauma is well documented, but paroxysmal exercise-induced dystonia occurring after trauma has yet to be described. Paroxysmal exercise-induced dystonia responds variably to anticonvulsant therapy, but the literature does not report response to baclofen, especially in low doses.

Paroxysmal dyskinesias in childhood

We report on clinical features of a large series of patients with paroxysmal dyskinesias. Fourteen patients had paroxysmal kinesigenic dyskinesia, with a mean age at onset of 7.1 years. In thirteen children the condition was idiopathic and nine of them had a positive family history; the remaining one had a Chiari malformation. Response to antiepileptic drugs was good in 60% of the treated patients. Six children had paroxysmal non-kinesigenic dyskinesia, with a mean age at onset of 8.1 years. Five children were symptomatic because of cerebral palsy (two patients), basal ganglia stroke (one patient), and acute inflammatory encephalopathy (one patient); the remaining patient's condition was familial with autosomal-dominant mode of inheritance. Response to medical treatment was unsuccessful contrasting with paroxysmal kinesigenic dyskinesia. Six children had paroxysmal exercise-induced dyskinesia, with a mean age at onset of 5 years. Their condition was idiopathic, with a positive family history in four. Two of these patients had also rolandic epilepsy and writer's cramp, and the syndrome had been previously mapped to chromosome 16. Although there have been great advances in the genetics of paroxysmal dyskinesias in which an ion channel dysfunction has been hypothesized, the diagnosis is still based on clinical grounds. The precise classification of the patients with paroxysmal dyskinesias is important for therapeutic decisions.

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.

Paroxysmal dyskinesias in the lethargic mouse mutant

Lethargic mutant mice carry a mutation in the CCHB4 gene, which encodes the beta4 subunit of voltage-regulated calcium channels. These mutants have been shown to display a complex neurobehavioral phenotype that includes EEG discharges suggestive of absence epilepsy, chronic ataxia, and hypoactivity. The current studies demonstrate a fourth element of their phenotype, consisting of transient attacks of severe dyskinetic motor behavior. These attacks can be triggered by specific environmental and chemical influences, particularly those that stimulate locomotor activity. Behavioral and EEG analyses indicate that the attacks do not reflect motor epilepsy, but instead resemble a paroxysmal dyskinesia. The lethargic mutants provide additional evidence that calcium channelopathies can produce paroxysmal dyskinesias and provide a novel model for studying this unusual movement disorder.

Early-onset absence epilepsy and paroxysmal dyskinesia

PURPOSE

To report on the association of childhood absence epilepsy and paroxysmal dyskinesia (PD).

METHODS

We describe six patients aged 6 to 27 years (mean, 14 years) who were identified in five centers participating in a European study group. Patients had been followed up clinically from the first symptoms and had been studied with video-EEG recordings of absence seizures, videotaping of dyskinetic attacks, and brain magnetic resonance imaging (MRI).

RESULTS

Four patients were sporadic, and two were siblings. Age at onset of absence seizures was unusually early (range, 3 months to 3 years 6 months; mean, 16 months), with four children having their first episodes within the first year of life, and the remaining two by age 3 years 6 months. Resistance to multiple appropriate drugs was seen in five children, in four of whom absences improved remarkably when ethosuximide was added. Absences remitted between age 8 and 13 years in the three patients in whom follow-up was long enough. Different types of PD were seen including paroxysmal kinesigenic dyskinesia (one patient), paroxysmal exercise-induced dystonia (three patients), and paroxysmal tonic upgaze (two siblings). In most patients, PD appeared at a later age than, co-occurred with, and outlasted absence seizures. Only in the two siblings with tonic upgaze, dyskinetic attacks had an earlier onset. PD improved with increasing age and did not usually produce severe disability.

CONCLUSIONS

There is a widening spectrum of epilepsy and PD syndromes, within which epilepsy has the characteristics of the common idiopathic syndromes, with some atypical features.

Benign familial infantile seizures: further delineation of the syndrome

Benign familial infantile seizures are an autosomal dominant epilepsy disorder that is characterized by convulsions, with onset at age 3 to 12 months and a favorable outcome. Benign familial infantile seizures have been linked to chromosome 19q whereas infantile convulsions and choreoathetosis syndrome, in which benign familial infantile seizure is associated with paroxysmal choreoathetosis, has been linked to chromosome 16p 12-q12. Many additional families from diverse ethnic backgrounds have similar syndromes that have been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Moreover, in one large pedigree with paroxysmal kinesiogenic dyskinesias only, the syndrome has also been linked to the same genomic area. Families with pure benign familial infantile seizures may be linked to chromosome 16 as well. In this study, we present a series of 19 families and 24 otherwise healthy infants with benign familial infantile seizures. Two of these families include members affected with benign familial infantile seizures and paroxysmal choreoathetosis. We included patients with normal neurologic examinations, who started having simple partial seizures, complex partial seizures, or apparently generalized seizures without recognized etiology between 2 months and 2 years of age. Neurologic studies were normal, but in all patients, there was a history of similar seizures and age at onset in either the father or the mother. Twenty-four patients (14 girls and 10 boys) were evaluated at our hospital between February 1990 and February 2001. Age at onset, sex, family history of epilepsy and/or paroxysmal dyskinesias, neurologic examination, semiology, distribution, and frequency and duration of seizures were evaluated. Electroencephalographic (EEG) and neuroradiologic studies were also performed. Seizures began between 3 and 22 months of life, with a median age of 5 1/2 months. Nine patients (37.5%) had only apparently generalized seizures, 5 patients (20.8%) had only partial seizures, and 10 patients had both partial and apparently generalized seizures (41.6%). Seizures were invariably brief, occurred during the waking state (100%), and presented mainly in clusters in 12 patients (50%). Interictal EEG was normal in 23 patients (95.8%). Sixteen patients (66.6%) had a confirmed history of convulsions in family members other than parents. Twenty-two patients became seizure free after 30 months of life. Two brothers in the same family had brief paroxysmal episodes of choreoathetosis in the hemibody triggered by stress while awake at 15 and 17 years old, respectively. One of them had paroxysmal choreoathetosis only, and the other was associated with benign familial infantile seizures. One father had brief spontaneous episodes of paroxysmal choreoathetosis when awake at age 18 years. All of them had a good response to antiepilepsy drugs, and neurologic examination and EEG and neuroradiologic studies were normal. Benign familial infantile seizure is a genetic epilepsy syndrome with autosomal dominant inheritance. It may be associated with paroxysmal choreoathetosis (infantile convulsions and choreoathetosis syndrome), which has been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Patients in families with infantile convulsions and choreoathetosis syndrome could display either benign familial infantile seizures or paroxysmal choreoathetosis or both. It is likely that the disease in families with pure benign familial infantile seizures may be linked to the infantile convulsions and choreoathetosis region as well. We cannot exclude the possibility that the youngest patients may develop choreoathetosis or other dyskinesias later in life.

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.

Partial epilepsy with pericentral spikes: a new familial epilepsy syndrome with evidence for linkage to chromosome 4p15

The genetic analysis of simple Mendelian epilepsies remains a key strategy in advancing our understanding of epilepsy. In this article, we describe a new family epilepsy syndrome, partial epilepsy with pericentral spikes, which we map to chromosome 4p15. We distinguish it clinically, electrophysiologically, and genetically from previously described Mendelian epilepsies. The family described is a large Brazilian kindred of Portuguese extraction in which affected family members manifest a variety of seizure types, including hemiclonic, hemitonic, generalized tonic-clonic, simple partial (stereotyped episodes of epigastric pain), and complex partial seizures consistent with temporal lobe epilepsy. The syndrome is benign, either requiring no treatment or responding to a single antiepileptic medication. Seizure onset is in the first or second decades of life, with seizures in individuals up to the age of 71 years and documented encephalogram changes up to the age of 30 years. A key feature of partial epilepsy with pericentral spikes is a characteristic encephalogram abnormality of spikes or sharp waves in the pericentral region (centroparietal, centrofrontal, or centrotemporal). This distinctive encephalogram abnormality of pericentral spikes unites these several seizure types into a discrete family epilepsy syndrome. As with other familial epilepsies, the inherited nature of this new syndrome may be overlooked because of the variability in penetrance and seizure types among affected family members.

The genetics of primary dystonias and related disorders

Dystonias are a heterogeneous group of disorders which are known to have a strong inherited basis. This review details recent advances in our understanding of the genetic basis of dystonias, including the primary dystonias, the 'dystonia-plus' syndromes and heredodegenerative disorders. The review focuses particularly on clinical and genetic features and molecular mechanisms. Conditions discussed in detail include idiopathic torsion dystonia (DYT1), focal dystonias (DYT7) and mixed dystonias (DYT6 and DYT13), dopa-responsive dystonia, myoclonus dystonia, rapid-onset dystonia parkinsonism, Fahr disease, Aicardi-Goutieres syndrome, Hallervorden-Spatz syndrome, X-linked dystonia parkinsonism, deafness-dystonia syndrome, mitochondrial dystonias, neuroacanthocytosis and the paroxysmal dystonias/dyskinesias.

Genetics of the epilepsies

Recent molecular insights into the human idiopathic epilepsies have suggested the central role of ligand-gated and voltage-gated ion channels in their etiology. So far, genes coding for sodium and potassium channel subunits as well as a nicotinic cholinergic receptor subunit have been identified for mendelian idiopathic epilepsies. In vitro and in vivo studies of mutations demonstrate functional changes, allowing new insights into mechanisms underlying hyperexcitability. Similarly, spontaneous murine epilepsy models have been associated with calcium channel molecular defects. The major challenge before us in understanding the genetics of the epilepsies is to identify genes for common forms of epilepsy following complex inheritance. Once such genes are discovered, the gene-gene-environmental interactions producing specific epilepsy syndromes can be explored.

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.

Paroxysmal Dyskinesia

This group of disorders is characterized by periodic sudden events of involuntary movement. The clinical range of these involuntary movements is wide including tonic spasms, choreiform and athetoid movements and sustained dystonic postures. Confusion with reflex forms of epilepsy has been common in the past, but in general, paroxysmal dyskinesias are not associated with alterations in consciousness or epileptiform activity on electroencephalogram. The underlying basis of the paroxysmal dyskinesia is under active investigation as is their relationship to epilepsy and other paroxysmal disorders.

Idiopathic epilepsy and paroxysmal dyskinesia

Although some motor manifestations of epilepsy and of paroxysmal dyskinesia may be difficult to differentiate clinically, the current understanding is that the two disorders are clinically distinct. However, there are several recent reports of families in which different individuals had either disorder or both manifestations, with age-related expression. Co-occurrence makes it likely that a common, genetically determined, pathophysiologic abnormality is variably expressed in the cerebral cortex and in basal ganglia. A rather homogeneous syndrome of autosomal dominant infantile convulsions and paroxysmal (dystonic) choreoathetosis (ICCA) was described in six families from France, China and Japan. Linkage analysis in the French and Chinese families allowed the mapping of the disease gene in a 10-cM interval within the pericentromeric region of chromosome 16. An Italian pedigree in which three members in the same generation were affected by rolandic epilepsy, paroxysmal exercise-induced dystonia (PED), and writer's cramp was subsequently reported. Linkage analysis showed a common homozygous haplotype in a critical region spanning 6 cM and entirely included within the ICCA critical region. Clinical analogies and linkage findings suggest that the same gene could be responsible for rolandic epilepsy, PED, writer's cramp (WC), and ICCA, with specific mutations accounting for each of these mendelian disorders. Evidence for a major gene or a cluster of genes for epilepsy and paroxysmal dyskinesia to the pericentromeric region of chromosome 16 is reinforced by the recent linkage of a family with autosomal dominant paroxysmal dyskinesia to a critical region partially overlapping with ICCA and contiguous to the RE-PED-WC regions. Additional autosomal dominant pedigrees are on record, from Australia and Italy, in which epilepsy was variably associated with paroxysmal kinesigenic or exercise-induced dystonia. Ion channel genes are potentially interesting candidates for syndromes featuring both these paroxysmal neurologic disorders. Increased awareness of their possible co-occurrence will certainly increase the number of observations in the next few years.

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.

Linkage of benign familial infantile convulsions to chromosome 16p12-q12 suggests allelism to the infantile convulsions and choreoathetosis syndrome

The syndrome of benign familial infantile convulsions (BFIC) is an autosomal dominant epileptic disorder that is characterized by convulsions, with onset at age 3-12 mo and a favorable outcome. BFIC had been linked to chromosome 19q, whereas the infantile convulsions and choreoathetosis (ICCA) syndrome, in which BFIC is associated with paroxysmal dyskinesias, had been linked to chromosome 16p12-q12. BFIC appears to be frequently associated with paroxysmal dyskinesias, because many additional families from diverse ethnic backgrounds have similar syndromes that have been linked to the chromosome 16 ICCA region. Moreover, one large pedigree with paroxysmal kinesigenic dyskinesias only, has also been linked to the same genomic area. This raised the possibility that families with pure BFIC may be linked to chromosome 16 as well. We identified and studied seven families with BFIC inherited as an autosomal dominant trait. Genotyping was performed with markers at chromosome 19q and 16p12-q12. Although chromosome 19q could be excluded, evidence for linkage in the ICCA region was found, with a maximum two-point LOD score of 3.32 for markers D16S3131 and SPN. This result proves that human chromosome 16p12-q12 is a major genetic locus underlying both BFIC and paroxysmal dyskinesias. The unusual phenotype displayed by one homozygous patient suggests that variability of the ICCA syndrome could be sustained by genetic modifiers.

Genetics of the epilepsies

Recent molecular insights into the human idiopathic epilepsies have suggested the central role of ligand-gated and voltage-gated ion channels in their etiology. So far, genes coding for sodium and potassium channel subunits as well as a nicotinic cholinergic receptor subunit have been identified for Mendelian idiopathic epilepsies. In vitro and in vivo studies of mutations demonstrate functional changes, allowing new insights in mechanisms underlying hyperexcitability. Similarly, spontaneous murine epilepsy models have been associated with calcium channel molecular defects. The major challenge before us in understanding the genetics of the epilepsies is to identify genes for common forms of epilepsy following complex inheritance. Once such genes are discovered, the gene-gene-environmental interactions producing specific epilepsy syndromes can be explored.

Co-segregation of benign infantile convulsions and paroxysmal kinesigenic choreoathetosis

We report seven families and two sporadic cases in which benign infantile convulsions and paroxysmal kinesigenic choreoathetosis were co-segregated. Clinical investigations included physical and neurological examinations, blood electrolyte values, interictal and ictal electroencephalograms, and computed tomography or magnetic resonance imaging of the brain. The family pedigree was confirmed and the clinical history of the relatives was obtained. Seventeen individuals developed infantile convulsions followed by paroxysmal dyskinesias during childhood or adolescence. Six had only infantile convulsions, and two had only paroxysmal dyskinesias. The seizures never persisted into childhood or recurred in adulthood. The seizure type was a complex partial seizure, with or without secondary generalization, in nine of 14 patients. Paroxysmal dyskinesias, a subgroup of paroxysmal kinesigenic choreoathetosis, occurred for less than 5 min. The attacks of dyskinesias began at age 5-12 years in most patients, and tended to remit in adulthood. The mode of inheritance was apparently autosomal dominant in four of the families (17 affected individuals), who were diagnosed with ICCA syndrome (infantile convulsions and paroxysmal choreoathetosis). However, the condition occurred only among siblings in three families (six patients), and sporadically in two patients, suggesting genetic heterogeneity in this distinct co-segregation.

Familial aphasic episodes: another variant of partial epilepsy with simple inheritance?

We report on a family having partial epilepsy with simple inheritance. The affected members commonly have aphasic episodes with secondary generalization; onset occurred either in adolescence or adulthood. Patients' response to medication has varied greatly. No neurological defects or decline in intelligence were found. The case represents another variety of rare familial partial epilepsy with neocortical epilepsy features.

Paroxysmal dyskinesias as a paradigm of paroxysmal movement disorders

Paroxysmal dyskinesias are genetically and clinically heterogeneous. Paroxysmal kinesigenic choreoathetosis is frequently familial, with autosomal-dominant transmission. Benign infantile convulsions can be observed in these families and both diseases as linked to the pericentromeric region of chromosome 16. Two different forms of paroxysmal dystonic choreoathetosis are distinguished on clinical grounds, by the presence or absence of spasticity, and genetically, as they are linked with loci on different chromosomes. Among the paroxysmal disorders, these diseases may belong to the group of channelopathies.

A new family with paroxysmal exercise induced dystonia and migraine: a clinical and genetic study

OBJECTIVE

To characterise the phenotype of a family with paroxysmal exercise induced dystonia (PED) and migraine and establish whether it is linked to the paroxysmal non-kinesigenic dyskinesia (PNKD) locus on chromosome 2q33-35, the familial hemiplegic migraine (FHM) locus on chromosome 19p, or the familial infantile convulsions and paroxysmal choreoathetosis (ICCA syndrome) locus on chromosome 16.

METHODS

A family, comprising 30 members, was investigated. Fourteen family members in two generations including three spouses were examined. Haplotypes were reconstructed for all the available family members by typing several microsatellite markers spanning the PNKD, FHM, and ICCA loci. Additionally, the four exons containing the known FHM mutations were sequenced.

RESULTS

Of 14 members examined four were definitely affected and one member was affected by history. The transmission pattern in this family was autosomal dominant with reduced penetrance. Mean age of onset in affected members was 12 (range 9-15 years). Male to female ratio was 3:1. Attacks of PED in affected members were predominantly dystonic and lasted between 15 and 30 minutes. They were consistently precipitated by walking but could also occur after other exercise. Generalisation did not occur. Three of the affected members in the family also had migraine without aura. Linkage of the disease to the PNKD, FHM, or ICCA loci was excluded as no common haplotype was shared by all the affected members for each locus. In addition, direct DNA sequential analysis of the FHM gene (CACNL1A4) ruled out all known FHM point mutations.

CONCLUSIONS

This family presented with the classic phenotype of PED and is not linked to the PNKD, FHM, or ICCA loci. A new gene, possibly coding for an ion channel, is likely to be the underlying cause of the disease.

Genetics of the epilepsies

Molecular genetic analysis of mendelian epilepsies in humans and mice has revealed a diversity of underlying genes in symptomatic epilepsies associated with disordered brain development and neuronal survival. In contrast, the idiopathic mendelian epilepsies have emerged as a new category of channelopathies. New epilepsy loci have been mapped and one new epilepsy gene isolated. Functional analysis of epilepsy genes is providing new insights into the pathways that lead from mutant gene to hyperexcitable neurones. The major challenge for the future is the analysis of genetic epilepsies with complex inheritance.

Paroxysmal kinesigenic choreoathetosis locus maps to chromosome 16p11.2-q12.1

Paroxysmal kinesigenic choreoathetosis (PKC), the most frequently described type of paroxysmal dyskinesia, is characterized by recurrent, brief attacks of involuntary movements induced by sudden voluntary movements. Some patients with PKC have a history of infantile afebrile convulsions with a favorable outcome. To localize the PKC locus, we performed genomewide linkage analysis on eight Japanese families with autosomal dominant PKC. Two-point linkage analysis provided a maximum LOD score of 10.27 (recombination fraction [theta] =.00; penetrance [p] =.7) at marker D16S3081, and a maximum multipoint LOD score for a subset of markers was calculated to be 11.51 (p = 0.8) at D16S3080. Haplotype analysis defined the disease locus within a region of approximately 12.4 cM between D16S3093 and D16S416. P1-derived artificial chromosome clones containing loci D16S3093 and D16S416 were mapped, by use of FISH, to 16p11.2 and 16q12.1, respectively. Thus, in the eight families studied, the chromosomal localization of the PKC critical region (PKCR) is 16p11.2-q12.1. The PKCR overlaps with a region responsible for "infantile convulsions and paroxysmal choreoathetosis" (MIM 602066), a recently recognized clinical entity with benign infantile convulsions and nonkinesigenic paroxysmal dyskinesias.

Recent advances in the genetics of epilepsy: insights from human and animal studies

Progress in understanding the genetics of epilepsy is proceeding at a dizzying pace. Due in large part to rapid progress in molecular genetics, gene defects underlying many of the inherited epilepsies have been mapped, and several more are likely to be added each year. In this review, we summarize the available information on the genetic basis of human epilepsies and epilepsy syndromes, and correlate these advances with rapidly expanding information about the mechanisms of epilepsy gained from both spontaneous and transgenic animal models. We also provide practical suggestions for clinicians confronted with families in which multiple members are afflicted with epilepsy.

A locus for febrile seizures (FEB3) maps to chromosome 2q23-24

Febrile seizures are the most common form of childhood seizures, occurring in 2% to 5% of North American children. We report a large Utah family with 21 members affected by febrile seizures inherited as an autosomal dominant trait. All had generalized tonic-clonic seizures with onset associated with fever, consistent with the consensus febrile seizure phenotype, and none had febrile seizures beyond 6 years of age. Eighteen affected individuals had recurrent febrile seizures. Eight individuals developed afebrile seizures between ages 5 and 13 years. Afebrile seizures consisted of generalized tonic-clonic, generalized tonic, generalized atonic, simple partial, and partial complex seizure types and were associated with abnormal electroencephalographic findings in 5 individuals, all of whom were intellectually normal. We undertook linkage analysis in this family, defining the disease phenotype as febrile seizures alone. Linkage analysis in epilepsy candidate gene/loci regions failed to show evidence for linkage to febrile seizures. However, a genomewide scan and subsequent fine mapping revealed significant evidence for a new febrile seizure locus (FEB3) on chromosome 2q23-24 with linkage to the marker D2S2330 (LOD score 8.08 at theta = 0.001). Haplotype analysis defined a critical 10-cM region between markers D2S141 and D2S2345 that contains the FEB3 locus.