Mapping the gene for juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy and narcolepsy: A series of three cases

OBJECTIVE

This paper sets out to demonstrate the coexistence of juvenile myoclonic epilepsy (JME) and narcolepsy that raises the possibility of a shared genetic predisposition to both conditions.

METHODS

The electronic medical records (EMRs) were searched for narcolepsy and JME over 10years.

RESULTS

We identified three young adult women diagnosed with JME in their teenage years, with myoclonic, generalized tonic-clonic, and absence seizure semiologies, along with psychiatric comorbidity, well managed on lamotrigine and/or levetiracetam. Our patients were also found to have disturbed sleep preceding the diagnosis of JME by many years, including excessive daytime sleepiness (EDS), fragmented nocturnal sleep, hypnagogic vivid hallucinations, and REM behavior disorder along with daytime cataplexy. They were ultimately diagnosed with coexisting narcolepsy, confirmed by sleep studies and multiple sleep latency testing, along with positive genetic testing for HLA-DQB1*0602 in all three patients. Stimulants, selective serotonin receptor inhibitors, and/or sodium oxybate were used to successfully treat their narcolepsy.

SIGNIFICANCE

The coexistence of JME and narcolepsy has not been well recognized and may be clinically relevant. In addition, it raises the possibility of a shared genetic predisposition to both conditions.

Genetic epilepsies. Remarks on the proposed “Organization of the Epilepsies”

Introduction.Genetic findings in several epilepsy syndromes provide insights into the pathophysiology of specific subtypes of epilepsy and into mechanisms of epileptogenesis, because the genes encoding ion channels, and proteins associated to the vesical synaptic cycle, or involved in energy metabolism, influence neuronal excitability.

Aim.The following aspects of genetic epilepsies will be discussed: new proposed “organization of the epilepsies”, genetic and other etiologies, electroclinical syndromes and their genetics and genetic testing in the epilepsies.

Methods.The updated review is based on OMIM™ (Online Mendelian Inheritance in Man).

Review and remarks.Because of the vast genetic and phenotypic heterogeneity, bridging genotype and phenotype remains a major challenge in epilepsy genetics. The so-called “idiopathic” epilepsies are genetically determined. The new ILAE proposal on the “organization” of the epilepsies takes into account the genetic advances. However, despite proposed changes in the nomenclature, the concept of the electroclinical syndrome, i.e. seizure types, age-dependent onset, electroencephalographic criteria, and concomitant symptoms, such as movement disorders or developmental delay, remain important criteria to group the epilepsies. Although also the differentiation “generalized” versus “focal” is nowadays discussed critically, for practical reasons these categories remain valid. Similarly the categories “benign” syndromes of early childhood, epileptic encephalopathies, and fever-associated syndromes, have their utility.

Conclusions.The large number of genetic defects in the epilepsies complicates their analysis. However, it is anticipated that novel genetic methods, that are able to analyze all known genes at a reasonable price, will help identify novel diagnostic and therapeutic avenues, including prognostic and genetic counseling. Today it is already possible to include into genetic testing genes responsible for the side effects of AEDs. In addition, for some epilepsy phenotypes it has became possible to predict the most efficacious antiepileptic drugs for patients based on their genetic makeup. Thus, the development of individualized medicine is expected to greatly improve the management of epilepsy patients.

Dimorphism of TAP-1 gene in Caucasian with juvenile myoclonic epilepsy and in Tunisian with idiopathic generalized epilepsies

Juvenile myoclonic epilepsy (JME) is the most common form of idiopathic generalized epilepsies (IGE) that account for about 5-10% of all types of epilepsies. The first putative locus termed EJM1 is on the human leucocyte antigen (HLA-II) region of chromosome 6p21.3. Interestingly, the EJM1 region includes the Transporter associated with antigen processing 1 (TAP-1) gene encoding the TAP-1, and previous studies have reported associations between HLA-II polymorphisms and different types of epilepsy. In this study, we report an association between two TAP-1 functional polymorphisms the I333V and the D637G and most common IGE in Tunisian population, but we fail to find significant results in Caucasian with JME.

Neuropsychological deficits in childhood epilepsy syndromes

Seizure disorders are relatively common in childhood, and the International League Against Epilepsy (ILAE) provides a hierarchical classification system to define seizure types. At the final level of classification, specific epilepsy syndromes are defined that represent a complex of signs and symptoms unique to an epilepsy condition. The present review discusses the issues related to several of these epilepsy syndromes in childhood, including those classified as generalized idiopathic epilepsies (e.g., childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy), focal epilepsies (benign rolandic epilepsy, occipital epilepsy, temporal lobe epilepsy, frontal lobe epilepsy) and the "epileptic encephalopathies," including Dravet's Syndrome, West Syndrome, Lennox-Gastaut Syndrome, Myoclonic Astatic Epilepsy, and Landau-Kleffner Syndrome. For each syndrome, the epidemiology, clinical manifestations, treatments, and neuropsychological findings are discussed.

Neuropsychological deficits in childhood epilepsy syndromes

Seizure disorders are relatively common in childhood, and the International League Against Epilepsy (ILAE) provides a hierarchical classification system to define seizure types. At the final level of classification, specific epilepsy syndromes are defined that represent a complex of signs and symptoms unique to an epilepsy condition. The present review discusses the issues related to several of these epilepsy syndromes in childhood, including those classified as generalized idiopathic epilepsies (e.g., childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy), focal epilepsies (benign rolandic epilepsy, occipital epilepsy, temporal lobe epilepsy, frontal lobe epilepsy) and the "epileptic encephalopathies," including Dravet's Syndrome, West Syndrome, Lennox-Gastaut Syndrome, Myoclonic Astatic Epilepsy, and Landau-Kleffner Syndrome. For each syndrome, the epidemiology, clinical manifestations, treatments, and neuropsychological findings are discussed.

Clinical and electroencephalographic study of first-degree relatives and probands with juvenile myoclonic epilepsy

PURPOSE

Juvenile myoclonic epilepsy (JME) is a common, well-defined epileptic syndrome. This study aims to examine the clinical and EEG features of probands with JME and to identify the incidence of different types of idiopathic generalized epilepsies (IGEs) and IGE trait in first-degree relatives.

METHODS

Clinical and EEG data were collected from 132 first-degree relatives and 31 probands with JME. The data were analyzed using descriptive statistics, chi-square test, t-test and ANOVA.

RESULTS

All probands had a history of generalized tonic clonic seizures (GTCS) and myoclonic jerks; 25.8% had a history of absence seizures. Family history of epilepsy was noted in 42% and epilepsy in first-degree relatives was reported in 38.7%. We found JME in 44% of the symptomatic first-degree relatives. The incidence of epilepsy was higher in siblings (19%) than in offspring (8%) or parents (4%), the difference between the groups being significant (p < 0.05). IGE trait was noted in 6% of the asymptomatic first-degree relatives. Finally, IGE features were found in 61%. Subjects with IGE features were younger (mean age 19.6 years) than those without IGE features (mean age 32.4 years) and the difference between the groups was significant.

CONCLUSION

The incidence of different kinds of IGEs and typical EEG trait is high in first-degree relatives of JME probands. IGE features were noted in 61% of the families. JME is the most common type of IGE and IGE features were found to be more frequent among siblings than parents. These findings confirm familial susceptibility to IGE.

Juvenile myoclonic epilepsy--a generalized epilepsy syndrome?

Juvenile myoclonic epilepsy (JME) has been classified as a syndrome of idiopathic generalized epilepsy and is characterized by specific types of seizures, showing a lack of pathology using magnetic resonance imaging (MRI) and computed tomography scanning. However, JME is associated with a particular personality profile, and behavioral and neuropsychologic studies have suggested the possible involvement of frontal lobe dysfunction. The development of highly sensitive neuroimaging techniques has provided a means of elucidating the underlying mechanisms of JME. For example, positron emission tomography has demonstrated neurotransmitter changes in the cerebral cortex, quantitative MRI has revealed significant abnormalities of cortical gray matter in medial frontal areas, and 1H-magnetic resonance spectroscopy has shown evidence of thalamic dysfunction, which appears to be progressive. Such techniques provide evidence of multi-focal disease mechanisms, suggesting that JME is a frontal lobe variant of a multi-regional, thalamocortical 'network' epilepsy, rather than a generalized epilepsy syndrome.

Phenotypic analysis of juvenile myoclonic epilepsy in Indian families

OBJECTIVES

Phenotypic analysis of juvenile myoclonic epilepsy (JME) is presented to document the variations in disease expression.

MATERIAL AND METHODS

Information on seizure type and frequency, seizure precipitating factors, electro-encephalographic (EEG) data, response to antiepileptic drugs (AEDs) and family history was collected on 500 Indian probands and 61 relatives with JME.

RESULTS

The overall clinical features, EEG characteristics, and familial occurrence were similar to other reports. JME probands and relatives having absences (56 of 561, 10%), those with only myoclonic jerks (MJ) or MJ with one generalized tonic clonic seizure (GTCS) in remission without treatment (five of 561, 1%) and those who required valproic acid (VPA) and another AED for seizure control (19 of 561, 3%) are examples of differential disease expression within JME. Seizures among those having photoparoxysmal response (PPR) on EEG responded very well to VPA alone while those with all three seizure types (MJ, GTCS and absences) were poor responders.

CONCLUSIONS

Recognition of clinical 'subtypes' among JME could have therapeutic implications and help improve JME phenotypic characterization for molecular studies.

Clinical expression and EEG features of patients with juvenile myoclonic epilepsy (JME) from North India

We aimed to characterize the clinical profile, EEG features and response to treatment of juvenile myoclonic epilepsy (JME) patients. We studied 103 JME probands with a standard protocol recording age of onset, type, frequency of seizures, EEG data, detailed family history and response to treatment in a superspeciality university hospital in New Delhi. The mean age of onset of disease was 14.01 +/- 3.14 years with a male to female ratio of 1.19 : 1. The myoclonic jerks were present in all the probands, generalized tonic-clonic seizures (GTCS) were present in 75.72% and 11.65% probands had absence seizures. The incidence of febrile convulsion (FC) was higher (9.7%) in our JME probands reflecting some ethnic variation or ascertainment bias. There was a considerable delay (of approximately 5.26 +/- 4.61 years) in the diagnosis of JME in our probands because most of the patients were referred from private physicians who were possibly not familiar with this epileptic syndrome in this part of the world or thought it was a milder variety of GTCS. The family history was positive in 25.24% JME probands among first- and second-degree relatives. An interictal EEG was found to be abnormal in 81 (78.64%) patients with the predominant abnormality being generalized polyspike and wave (PSW) discharges (39.80% probands). The majority of patients (80.58%) showed a good response to treatment with valproate alone. There was a subset of patients (11.65%) who required the addition of other antiepileptic drugs (AEDs) for control of GTCS: 7.76% of JME patients were diagnosed as cases of GTCS by private practitioners before they were registered in our study and their seizures were well controlled on other AEDs (without valproate) prescribed by the referring physicians (carbamazepine-4, phenytoin-2, clobazam-2). It is concluded that the clinical features and EEG data of JME probands were comparable to reports from other parts of the world except for the fact that the incidence of FC was higher in our JME patients. There was a delay in the diagnosis of JME due to unfamiliarity with the epileptic syndrome among private practitioners in this part of the world. There was a subset of JME patients who had complete seizure control on other AEDs besides valproate.

Juvenile myoclonic epilepsy--an experience from north western India

OBJECTIVES

The clinical data on cases of Juvenile Myoclonic Epilepsy (JME) were analysed. Response to initial small dosages (lower than usual) of sodium valproate and further lower maintenance dosages in patients who were seizure free for 2 years on drug were assessed.

MATERIAL AND METHODS

Seventy-six patients who were diagnosed to have Juvenile Myoclonic Epilepsy on definite criteria were studied. All patients were put on sodium valproate in dosages (lower than usual) for initial control and further lower maintenance dosage and response evaluated.

RESULTS

The clinical profile was found to be similar as in other parts of India. There was a female preponderance and average delay of 4.9 years in final diagnosis. Forty-eight (63.1%) patients showed good control on 15 mg/kg/day dosages of sodium valproate. After a seizure free interval of 2 years, 58% of patients could be maintained on small dosages ranging from 3-5 mg/kg/day to 6-8 mg/kg/day.

CONCLUSION

The majority of JME patients responded well not only to sodium valproate in dosages lower than usually prescribed but required very small dosages for maintenance after a seizure free period of 2 years.

Epileptic seizures and syndromes

This article describes the main characteristics of the different types of seizures and their classifications. The main types of epilepsies are reviewed, including their main, clinical, and EEG features and an overview of their treatment.

Physiological basis: how NREM sleep components can promote and REM sleep components can suppress seizure discharge propagation

OBJECTIVES

To describe how the neural generators of different sleep components can provoke seizure discharge propagation during NREM sleep and can suppress it during REM sleep.

METHODS

Experimental manipulations of discrete physiological components were conducted in feline epilepsy models (n=64), mostly in the systemic penicillin epilepsy model of primary generalized epilepsy and the amygdala kindling model of the localization-related seizure disorder, temporal lobe epilepsy. Procedures included seizure induction as well as quantifying norepinephrine concentrations (microdialysis) and the sleep-waking state distribution of seizures before and after lesions, systemic and localized drug administration and/or photic stimulation.

RESULTS

(1) Neural generators of synchronous EEG oscillations, including tonic background slow waves and phasic 'arousal' events (sleep EEG transients such as sleep spindles, k-complexes), can combine to promote electrographic seizure propagation during NREM and drowsiness; anti-gravity muscle tone permits seizure-related movement. (2) Neural generators of asynchronous neuronal discharge patterns can reduce electrographic seizures during alert waking and REM sleep; skeletal motor paralysis blocks seizure-related movement during REM. (3) Etiology of the seizure disorder can interact with sleep and arousal mechanisms to determine sleep-waking state distribution of interictal and ictal events.

CONCLUSIONS

Differential effects of NREM versus REM sleep components on seizure discharge propagation are to some extent non-specific and in other ways specific to seizure etiology.

Univariate genetic analyses of epilepsy and seizures in a population-based twin study: the Virginia Twin Registry

The purpose of this study was to examine the roles of genetic and environmental factors in the etiology of epilepsy and seizures in twins ascertained from the Virginia Twin Registry. Health history information on twins was collected by questionnaire. Concordance rates were calculated and used to estimate degree of concordance for seizure types in monozygotic (MZ) and dizygotic (DZ) twin pairs. Univariate twin analyses were performed for each epilepsy and seizure type to determine models which best explained observed variation. Health history information concerning epilepsy and febrile seizure occurrences was provided by members of 8,655 twin pairs; 6,684 of these supplied additional information reporting absence, complex partial, tonic-clonic, and unspecified seizures. Models including additive genetic and unique environmental factors best explained febrile seizures, epilepsy, complex partial seizures, and unspecified seizures. For complex partial seizures, however, the contributions of genetic and environmental effects did not vary across gender. These results show that, under univariate analysis methods, genetic factors played an important role in the expression of seizures in epilepsy, febrile seizures, unspecified seizures, and complex partial seizures. Additional support for these findings was provided by the concordance results for all categories except male twins reporting complex partial seizure occurrence. However, environmental influences still remained an important factor in seizure expression in these specific categories.

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.

Human gamma-aminobutyric acid B receptor gene: complementary DNA cloning, expression, chromosomal location, and genomic organization

BACKGROUND

The 6p21.3 region of human chromosome 6 is a genetic locus for schizophrenia, juvenile myoclonic epilepsy, and dyslexia.

METHODS

Due to our interest in these disorders we performed complementary DNA (cDNA) hybridization selection on genomic DNA clones spanning this region to identify potential positional-candidate genes.

RESULTS

We identified a full-length cDNA with an open reading frame of 2883 bp corresponding to a predicted protein of 961 amino acids that shares greater than 95% homology with the rat gamma-aminobutyric acid B (GABAB) receptor. Northern blot hybridization identified a 4.4-kb transcript in human brain. The human gene mapped to two sites on 6p21.3 separated by 2 Mb. Sequence analysis of both sites showed that the centromeric gene is transcribed, whereas the telomeric site is likely a pseudogene. The transcribed gene is distributed over 22 exons spanning 18 kb of genomic DNA.

CONCLUSIONS

The genomic location, tissue expression, and function of the human GABAB receptor gene suggest that it is an important positional-candidate for the neurobehavioral disorders with a genetic locus on 6p21.3. In addition, delineation of the genomic organization will now permit it to be integrated as part of pharmacogenetic studies in trials of anxiolytic, narcotic, antiepileptic, and fluoxetine therapies.

Multilobar polymicrogyria, intractable drop attack seizures, and sleep-related electrical status epilepticus

BACKGROUND AND OBJECTIVE

Patients with cortical malformations often have intractable seizures and are candidates for epilepsy surgery. Within an unselected series of patients with various forms of cortical malformation, nine patients with multilobar polymicrogyria had electrical status epilepticus during sleep (ESES) accompanied by infrequent focal motor seizures. Eight patients also had intractable atonic drop attack seizures. Because ESES usually is accompanied by a good long-term seizure prognosis, the objective of this study was to examine ESES outcome among patients with a structural lesion that is usually highly epileptogenic and has a low seizure remission trend.

METHODS

The nine patients had follow-up periods lasting 4 to 19 years. All underwent brain MRI, serial sleep EEG recordings, and cognitive testing during and after ESES.

RESULTS

ESES and drop attack seizures appeared between the ages of 2 and 5 years (mean, 4 years) and ceased between the ages of 5 and 12 years (mean, 8 years). At the last visit patients were 8 to 23 years of age (mean, 14.5 years) and were either seizure free or had very infrequent focal motor seizures during sleep. Three patients were free from antiepileptic drugs. In no patient was definite cognitive deterioration apparent after ESES in comparison with earlier evaluations.

CONCLUSIONS

Age-related secondary bilateral synchrony underlying ESES may be facilitated in multilobar polymicrogyria. The good seizure outcome contrasts with that usually found in the presence of cortical malformations. For children with polymicrogyria and drop attack seizures, surgical treatment of the epilepsy should be considered cautiously, and sleep EEG recordings should be performed systematically.

Juvenile myoclonic epilepsy: clinical characteristics, treatment and prognosis in a Norwegian population of patients

Forty-three patients with juvenile myoclonic epilepsy (JME) is presented. The female to male ratio was 2.9:1. The patients answered a standardized questionnaire pertaining to social situation, medical history, onset of epilepsy, types and frequency of seizures, treatment, experienced control over seizures and consequences of having epilepsy. Myoclonic jerks, which are the hallmark of the condition, are often forgotten by the patients or not considered as epileptic seizures. This could be one reason why JME still seems underdiagnosed. JME may comprise absence, myoclonic and generalized tonic-clonic seizures (GTCS), proposed to occur in age-related sequence. We found that absence seizures may start after onset of other seizures. Our results confirm the need for medication since, during the last year, only 7% were seizure free without medication. Of patients on antiepileptic drugs (AEDs), 79.5% had no GTCS and 41% were seizure free during the last year, which confirms a relatively good response to appropriate treatment. Although most patients used AED daily and many still had one or more types of epileptic seizure, the epilepsy in general had very little impact on their lives.

Juvenile myoclonic epilepsy: disease expression among Indian families

OBJECTIVES

Juvenile myoclonic epilepsy (JME) is a common, age related, idiopathic generalized epileptic syndrome. We aimed to define the expression of JME in Indian probands and study the occurrence of seizures/epileptic syndromes in their family members.

METHODS

We studied 225 JME probands with a uniform protocol. recording the type and frequency of seizures, precipitating factors, EEG data, and family history. Detailed family pedigrees were drawn to include all the 1st- and 2nd-degree relatives of probands. The seizures/epileptic syndromes in relatives examined were classified in a uniform way.

RESULTS

The clinical and EEG characteristics of 225 JME probands from India were similar to those reported in probands from different ethnic backgrounds. The incidence of febrile convulsions in probands with JME was similar to that of the general population but was much lower (0.2%) among their relatives. A positive family history of seizures among 1st- or 2nd-degree relatives was noted in 79 of 225 (35%) probands. The risk of relatives being affected as well as their risk of expressing a type of idiopathic generalized epilepsy (IGE) varied as a function of the degree of relation with the probands.

CONCLUSIONS

The clinical expression of JME among probands from India is fairly similar to that reported in probands of different ethnic backgrounds. The risk of relatives being affected as well as their risk of expressing a type of IGE (including JME) varies as a function of the degree of relation with the probands. The reduced occurrence of febrile convulsions among the relatives of JME probands probably represents an ascertainment bias. A much larger database of this type should be helpful in understanding the interactions of different genes that are believed to be responsible for some of the inherited human epileptic syndromes like JME and other IGEs.

Myoclonus and epilepsies

The possible associations of myoclonic phenomenae, progressive or non-progressive encephalopathies and epileptic features are reviewed, with special emphasis on pediatric age. This leads to recognize the following five groups of conditions: (1) Myoclonus without encephalopathy and without epilepsy; (2) Encephalopathies with non-epileptic myoclonus; (3) Progressive encephalopathies presenting myoclonus seizures of epileptic syndromes (Progressive myoclonus epilepsies); (4) Epileptic encephalopathies with myoclonic seizures; (5) Myoclonic epilepsies. Within the first group, which also includes physiologic myoclonus, a more thorough description of "Benign sleep myoclonus of newborn" and "Benign myoclonus of early infancy" is given. Characteristics of group 2 are "Kinsbourne Syndrome" and certain types of "Hyperekplexia" which pose interesting differential diagnosis with stimulus-sensitive epilepsies. In group 3, the concept of progressive encephalopathies is stressed. The fourth group refers to severe epilepsies, mainly on infancy and childhood, which lead to mental retardation irrespective of their aetiology. Group 5 comprises the true myoclonic epilepsies, differentiating syndromes recognized as idiopathic--such as "Benign myoclonic epilepsy of infancy" and "Juvenile myoclonic epilepsy"--from those which are cryptogenic and carry a more cautious prognosis--as "Cryptogenic myoclonic and myoclonoastatic epilepsies" and "Severe myoclonic epilepsy of infancy". Other epileptic syndromes not usually considered as myoclonic epilepsies, but presenting sometimes as myoclonic seizures, are finally referred.

Hereditary epilepsy syndromes

This paper reviews the present knowledge on the genetics of the epilepsies. Main clinical features, gene localization and pattern of inheritance of the idiopathic epilepsies, the progressive myoclonus epilepsies, and some other genetic disorders often associated with epilepsy, are described.

Brain chimeras in birds: application to the study of a genetic form of reflex epilepsy

A strain of chicken, called here FEpi (for Fayoumi epileptic), bearing an autosomal recessive mutation, exhibits a form of reflex epilepsy with EEG interictal paroxysmal manifestations and generalized seizures in response to either light or sound stimulations. By using the brain chimera technology, we demonstrate here that the epileptic phenotype can be partially or totally transferred from an FEpi to a normal chick by grafting specific regions of the embryonic brain. The mesencephalon contains the generator of all epileptic manifestations whether they involve visual or auditory neuronal circuits, with the exception of the abnormal EEG which is transmitted exclusively by telencephalic grafts. This analysis supports the hypothesis that certain forms of human and mammalian epilepsies have a brainstem origin.

Circadian rhythm, sleep, and epilepsy

This review article: (1) describes the circadian distribution of ictal and interictal events; (2) differentiates transitional arousal, non-rapid eye movement and rapid eye movement sleep components and their substrates; (3) suggests the means by which the neural generators of these seizure-prone vs. seizure-resistant sleep and arousal states modulate the timing of different seizure manifestations; (4) considers clinical and mechanistic findings for the reciprocal effects of seizures and antiepileptic drugs upon the sleep-wake cycle; and (5) assesses clinical and basic mechanisms of sleep deprivation effects upon seizures.

Primary (idiopathic) generalized epilepsy and underlying mechanisms

Primary Generalized Epilepsy (PGE) has been more hotly debated over the past decades than other forms of epileptic seizure disorder. The sudden synchronous appearance of bilateral spikes and spike-waves (mainly with myoclonus resp. absence) used to perplex the earliest generation of electroencephalographers, and the enigmatic genesis of these discharges (and seizures) has not ceased to fascinate the investigators of this phenomenon. A "centrencephalic" concept with paroxysmal discharges arising from thalamic structures and "projecting" to the cortex was championed for many years and eventually laid aside. More recently, the role of the thalamic level has been re-emphasized, mainly on the basis of experimental work. In this article, the bulk of experimental work is critically reviewed: the simian model (Papio papio), the feline, and the rodent models (Wistar rat, tottering mouse). Stress is being laid on fundamental differences between all of these models and human PGE. EEG evidence indicates a superior frontal origin of bilateral-synchronous spikes and spike-waves; depth EEG recordings in patients have failed to demonstrate primary thalamic spike generation. The heart of the matter in PGE appears to be the mechanism underlying paroxysmal discharges; above all the role of arousal. It is not awakening from sleep but the ensuing period that is critical in its epileptogenic thrust caused by alternating periods of return to drowsiness and arousing stimuli. This biphasic process gradually escalates EEG bursts to myoclonus (or absences) and possibly to a generalized tonic-clonic convulsion. Most conducive to this crescendo is the state of tiredness following a night of poor sleep. Bilateral synchrony is not precise and small time differences exist. The line between primary and secondary bilateral synchrony (with a primary cortical focus) can become blurred. Genetic predisposition to generalized paroxysms must always be considered, even in the face of a primary focus with secondary bilateral synchrony. Photosensitivity is a second paroxysm-inducing mechanism in PGE; it is much less common than the abnormal arousal ("dyshormia"); both mechanisms can be present in the same patient. Therapy and prevention of seizures in PGE are finally discussed. The concept of abnormal arousal mechanisms can be put into practice in order to prevent seizures: avoidance of sleepless nights, not always an easy task in adolescents and young adults.

Juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy is a relatively common, though under diagnosed, form of epilepsy that commences in adolescence. The distinguishing symptoms, diagnosis and medical management are discussed.

Juvenile myoclonic epilepsy and human leukocyte antigens

The idiopathic generalized epilepsies (IGE) occur with a high aggregation within families. Juvenile myoclonic epilepsy (JME) is recognized as a commonly occurring form of idiopathic generalized epilepsy. A possible association between JME and HLA antigens was investigated by serological typing of human leukocyte antigens (HLA) class I antigens and by DNA oligotyping of class II antigens. Twenty-four patients and 129 controls, all Caucasians of Scandinavian descent, were tested. Uncorrected there was a significant positive association (Relative risk (RR) = 8.07) to B17 and a significant negative association (RR = 0.13) to B8 as well as DRB1*3. The negative association to DQ alleles DQA1*0501 and DQB1*0201, which are in strong linkage disequilibrium with the alleles B8 and DRB1*3, was weaker and not significant, thus giving no clue as to a primary HLA-DQ association of JME.

Reduced fertility and neuroendocrine dysfunction in women with epilepsy

A reduction of fertility in women with epilepsy has been reported since 1950 and is confirmed in recent epidemiological studies. This phenomenon has usually been attributed to the increase of medical and socioeconomic problems in these patients or to hyposexuality, which has been consistently observed in epileptic subjects. Recently, a higher occurrence of reproductive endocrine diseases has been reported in epileptic women and proposed as an important cause of reduced fertility. In particular, polycystic ovary syndrome and hypothalamic ovarian failure have been reported in epileptic women with increased frequency compared to the general population. Moreover, an abnormal pattern of luteinizing hormone (LH) pulsatility has been observed in normally cycling, drug-free epileptic women. We suggest that epilepsy may interfere with the functional activity of the gonadotropin releasing hormone (GnRH) pulse generator. It is possible that paroxysmal discharges spreading within the hypothalamus might affect the regularity of the GnRH pulse generator; alternatively, a neurotransmitter dysfunction might at the same time be responsible both for the lowering of the seizure threshold and for the dysfunction of GnRH secretion. The consequent alteration of LH pulsatility might in the long run, under the effect of additional factors, give rise to a clinical reproductive endocrine disorder.

Juvenile myoclonic epilepsy: a 5-year prospective study

We made a long term prospective study of 66 patients with juvenile myoclonic epilepsy (JME). Prevalence was 10.2% among 672 patients with epilepsies. Sex distribution was equal. Sixty-three were not diagnosed on referral; JME was not initially recognized in the epilepsy clinic in 22. Clinical typical absence seizures were reported in 33.3%, myoclonic jerks in 97% and generalized tonic-clonic seizures (GTC) in 78.8% of the patients. Mean age (+/- SD) at onset was 10.5 +/- 3.4 years (range 5-16 years) for absence seizures, 15 +/- 3.5 years (range 8-26 years) for myoclonic jerks, and 16 +/- 3.5 years (9-28) years (range 1-9 years) and GTC by 4.4 +/- 2.7 years (range 1-8 years) in 14 (21.2%) patients who manifested all three types of seizure. Absence were never antedated by myoclonic jerks or GTC. Myoclonic jerks occurred on awakening in 87.5% of the patients. GTC occurred mainly on awakening, but other patients had nocturnal or diurnal GTC with no circadian distribution. Neurologic examination was normal for all patients except for tremor of the hands similar to essential tremor, noted in 35% of patients. Computed tomography (CT) brain scans were normal: 93% of patients had precipitating factors: sleep deprivation (89.5%), fatigue (73.7%), photosensitivity (36.8%; television and video games 8.8%), menstruation (24.1% of women), mental concentration (22.8%), and stress (12.3%). Incidence of JME among siblings (13 of 41 examined families) implies an autosomal recessive mode of inheritance for this Arab population. EEGs were frequently normal in treated patients. At least one abnormal EEG was recorded in 56 (84.9%) patients. Abnormalities consisted mainly of generalized discharges of spike/double spike and/or polyspike and slow wave. Frequent multiple spikes and discharge fragmentations varied from 0.5- to 20-s duration (mean 6.8 s). Twenty (30.3%) had focal abnormalities, and 18 (27.3%) had photoconvulsive discharges. Eighty-eight percent of patients remained seizure-free for > or = 3 years of follow-up. Effective treatment was achieved with valproate (VPA); control of myoclonic jerks was improved with clonazepam (CZP). CZP monotherapy did not consistently prevent GTC. Adding small doses of CZP with simultaneous reduction of VPA was the most effective and better tolerated form of medication, particularly in patients demonstrating an adverse reaction or requiring a large VPA dosage. VPA dosage was successfully reduced in 15 patients who were seizure-free for > 2 years and had infrequent seizures before treatment, but 9 of 11 patients relapsed after VPA discontinuation.(ABSTRACT TRUNCATED AT 400 WORDS)

Progress in mapping human epilepsy genes

The chromosomal loci for seven epilepsy genes have been identified in chromosomes 1q, 6p, 8q, 16p, 20q, 21q, and 22q. In 1987, the first epilepsy locus was mapped in a common benign idiopathic generalized epilepsy syndrome, juvenile myoclonic epilepsy (JME). Properdin factor or Bf, human leukocyte antigen (HLA), and DNA markers in the HLA-DQ region were genetically linked to JME and the locus, named EJM1, was assigned to the short arm of chromosome 6. Our latest studies, as well as those by Whitehouse et al., show that not all families with JME have their genetic locus in chromosome 6p, and that childhood absence epilepsy does not map to the same EJM1 locus. Recent results, therefore, favor genetic heterogeneity for JME and for the common idiopathic generalized epilepsies. Heterogeneity also exists in benign familial neonatal convulsions, a rare form of idiopathic generalized epilepsy. Two loci are now recognized; one in chromosome 20q (EBN1) and another in chromosome 8q. Heterogeneity also exists for the broad group of debilitating and often fatal progressive myoclonus epilepsies (PME). The gene locus (EPM1) for both the Baltic and Mediterranean types of PME or Unverricht-Lundborg disease is the same and is located in the long arm of chromosome 21. Lafora type of PME does not map to the same EPM1 locus in chromosome 21. PME can be caused by the juvenile type of Gaucher's disease, which maps to chromosome 1q, by the juvenile type of neuronal ceroid lipofuscinoses (CLN3), which maps to chromosome 16p, and by the "cherry-red-spot-myoclonus" syndrome of Guazzi or sialidosis type I, which has been localized to chromosome 10. A point mutation in the mitochondrial tRNA(Lys) coding gene can also cause PME in children and adults (MERFF).

Concordance of clinical forms of epilepsy in families with several affected members. Italian League Against Epilepsy Genetic Collaborative Group

Evidence for genetic heterogeneity in epilepsy is strong. We evaluated the concordance of clinical forms in the same family in a series of families with several cases of idiopathic epilepsy, collected as part of the Study on the Genetics of Epilepsy of the Italian League against Epilepsy (LICE). The studied families had at least three members affected by an idiopathic form of epilepsy in one or more generations. Seventy-four families (with a total of 296 affected members) have been analyzed; two families had cases with benign neonatal familial convulsions (BNFC); in 25% of the remaining families all members were affected by the same clinical form, 13.9% had a prevalent clinical form with only one affected member with a different seizure type, 36.1% had two clinical forms, and 25% had three forms of epilepsy in the same family. There are no clinical differences in the form of epilepsy between the families concordant for one clinical form and families with two or three clinical forms of idiopathic epilepsies. The distribution of the clinical form in the affected relatives in our families showed the higher concordance with the proband in febrile convulsions (FC, 70.8%) and in epilepsy with generalized tonic-clonic seizures (EGTC, 63.0%). FC and EGTC were highly diffused in the affected relatives in the families with other forms of idiopathic epilepsy, above all in the more distantly related affected family members. In our families we observed a rare associated between childhood absence epilepsy (CAE) and juvenile myoclonic epilepsy (JME).(ABSTRACT TRUNCATED AT 250 WORDS)

Some excitatory and inhibitory factors involved in the epileptic state

Many factors are involved in the determination of the epileptic threshold and the precipitation of epileptic seizures. The balance between the underlying excitatory and inhibitory mechanisms are often imperfectly understood. However, some of these factors must be fully considered if the management of those with epilepsy is to be effective. This applies especially to children. Certain types of epilepsy are genetically determined, and others are age-related. Development of the brain plays a crucial role in the changing liability to epilepsy. If these processes are disturbed by various lesions and diseases, such as metabolic and toxic disorders, protective mechanisms may suffer. Kindling and mirror foci, the role of the cerebellum, and reflex epilepsy will be discussed. There are some seizure-inducing factors which are susceptible to change, and can be as important as anti-epileptic drugs in controlling seizures. The use and limitations of these measures, and of drugs, will be considered.

Seizure threshold in juvenile myoclonic epilepsy with Graves disease

Thyroxine lowers the seizure threshold in experimental animals and humans. We report juvenile myoclonic epilepsy (JME) in two female patients with Graves' disease who had exophthalmos at age 11 (patient 1) and age 12 years (patient 2) but remained untreated until onset of seizures at ages 15 and 13 years, respectively. Seizures were not controlled well despite administration of antiepileptic drugs (AEDs) during the periods of excess serum thyroid hormones in Graves disease. When the serum levels of T3 were reduced to < 220 ng/dl with antithyroid drug treatment, both clinical seizures and paroxysmal EEG abnormalities disappeared despite discontinuation of AEDs and sleep deprivation. JME was noted only during periods of excess thyroid hormone and low compliance with antithyroid drug treatment. The excessively high level of thyroid hormones may have been a factor in precipitating the onset of JME.

Characterization of intractable juvenile myoclonic epilepsy: new perspectives on primarily generalized seizures

Twelve patients were identified at an epilepsy center who had medically intractable juvenile myoclonic epilepsy. Significant characterization of this group included the long duration of their epilepsy (averaging 21 years) during which the diagnosis and appropriate treatment was delayed. A high percentage of these patients had asymmetries or focal discharges on scalp EEG (6 of 9 patients). A review of the literature and the findings in these 12 patients lead to the conclusion that juvenile myoclonic epilepsy is not necessarily a benign epilepsy. Alternative therapies, such as epilepsy surgery, may be indicated in such extreme cases.

Epileptic seizures in the 4p- syndrome: report of two cases

We report ictal phenomena in two patients with the 4p- syndrome captured on simultaneous video-EEG monitor. One patient, diagnosed as having partial epilepsy, had complex partial seizures and hemiconvulsive status epilepticus. This was associated with more severe mental retardation. The second patient was diagnosed as having the West syndrome and exhibited tonic spasms with a cluster formation. We conclude that various types of epileptic seizures may occur in patients with the 4p- syndrome, including grand mal and myoclonic seizures.

Gene mapping in the idiopathic generalized epilepsies: juvenile myoclonic epilepsy, childhood absence epilepsy, epilepsy with grand mal seizures, and early childhood myoclonic epilepsy

Idiopathic generalized epilepsies, i.e., juvenile myoclonic epilepsy (JME), childhood absence epilepsy, and epilepsy with grand mal [generalized tonic-clonic seizures (GTCS)], are the most common genetic epilepsies. Linkage studies using Bf, HLA serologic, and DNA markers by three independent investigators, one from Los Angeles and two from Berlin, have localized the JME locus to the short arm of chromosome 6 (6p). Because members of the same JME family have the same JME phenotype of childhood absence epilepsy, epilepsy with grand mal (GTCS) seizures, or early childhood myoclonic epilepsy (ECME), our observations give evidence for a single-locus etiology in 6p for JME and for at least some of the childhood absence seizures, epilepsy with grand mal (GTCS) seizures, and ECME. Studies should now address whether locus heterogeneity exists within childhood absence epilepsy, epilepsy with grand mal (GTCS) seizures, or ECME. Markers linked to JME (Bf, HLA serologic, and DNA markers in the DQ region) can be used to resolve etiologic heterogeneity. Using such markers, both linked and unlinked forms of phenotypes that are clinically indistinguishable may be detected and provide evidence for etiologic heterogeneity. Studies should also concentrate on narrowing the JME locus to 2 to 3 cm by screening families with recombinant events using RFLPs, candidate genes, and new expressed sequences on chromosome 6.