Clinical and genetic aspects of juvenile absence epilepsy

Typical absence seizures in children: Review with focus on EEG predictors of treatment response and outcome

Typical absence seizures (TAS) occur in idiopathic generalized epilepsy (IGE) syndromes and are a common presentation to paediatric neurologists. Considerable overlap in clinical features of IGE syndromes comprising TAS often complicates prognostication. Clinical and EEG diagnostic features in TAS are well known. However, knowledge of prognostic features for each syndrome, whether clinical or EEG-related, is less clear. Perpetuated impressions in clinical practice regarding the role of EEG when used for prognostication in TAS are known. Assumed prognostic features, particularly those relating to EEG have been rarely studied systematically. Despite rapid expansion in epilepsy genetics, the complex and presumed polygenic inheritance of IGE, means that clinical and EEG features are likely to remain the main guide to management and prognostication of TAS for the foreseeable future. We comprehensively reviewed available literature and hereby summarize current knowledge of clinical and EEG characteristics (ictal and interictal) in children with TAS. The literature focuses predominantly on ictal EEG. Where studied, interictal findings reported relate to focal discharges, polyspike discharges, and occipital intermittent rhythmic delta activity, with generalized interictal discharges not thoroughly studied. Furthermore, reported prognostic implications of EEG findings are often conflicting. Limitations of available literature include inconsistent clinical syndrome and EEG finding definitions, and variable EEG analysis methods, particularly lack of raw EEG data analysis. These conflicting findings coupled with varying study methodologies cause lack of clear information or evidence on features which may influence treatment response, outcome, or natural history of TAS.

Therapeutic approach to difficult-to-treat typical absences and related epilepsy syndromes

Introduction: typical absences (TAs), are brief, generalized epileptic seizures of abrupt onset and termination clinically manifesting with impairment of awareness and associated with 3 Hz spike-wave discharges on EEG. TAs may occur in different idiopathic generalized epilepsies (IGE). Despite treatment with adequate anti-seizure medications (ASMs), TAs may persist in ~25% of subjects. This narrative review focuses on the therapeutic approach to difficult-to-treat TAs occurring in the setting of IGE.Areas covered: a literature search was conducted on the topic of treatment of TAs.Expert opinion: ethosuximide (ESX), valproic acid (VPA) and lamotrigine (LTG), alone or in combination, are considered the first-choice drugs. In women of childbearing potential, VPA should be avoided. Alternative therapies (benzodiazepines, levetiracetam, topiramate, or zonisamide) should be considered in subjects unresponsive to monotherapy after the exclusion of pseudo-drug resistance. Newer ASMs such as brivaracetam and perampanel seem to be promising options. Well-conducted clinical trials aimed to evaluate the efficacy of alternative monotherapy (beyond ESX, VPA or LTG) or combination of ASMs on difficult-to-treat TAs, are warranted.

Clinical Significance of Incidental Rolandic Spikes in Children With Absence Epilepsy

PURPOSE

Absence epilepsy and benign epilepsy of childhood with central temporal spikes are common childhood epilepsy syndromes. Although 3-Hz generalized spike-wave discharges are almost always associated with absence seizures, rolandic spikes can be present in individuals without rolandic seizures. The co-occurrence of 3-Hz generalized spike-wave and rolandic spikes is very rare. Our objective was to compare clinical features of patients with absence epilepsy with and without rolandic spikes, to determine if the additional feature of rolandic spikes has any clinical significance.

METHODS

Clinical information of 17 children with absence epilepsy and rolandic spikes was compared to an age-matched control group of 90 children with absence epilepsy.

RESULTS

Although most patients had excellent seizure control at follow-up, epilepsy comorbidities (cognitive and emotional problems) were observed. Comparing study vs control groups, there was no difference with anxiety (2 [11.8%] vs 8 [9%]), behavioral issues (4 [23.5%] vs 10 [11%]), mood disorders (0 vs 2 [2%]), and attention-deficit hyperactivity disorder (4 [24%] vs 10 [11%]). Significant differences were also observed: more global-developmental (5 [29%] vs 5 [6%], P < .009) and expressive-language (4 [24%] vs 5 [6%], P < .034) delay and more difficulties with school performance (11 [65%] vs 32 [36%], P < .025), especially with language-related tasks (6 [35%] vs 5 [6%], P < .001).

CONCLUSION

Our results confirm the presence of additional epilepsy comorbidities in patients with absence epilepsy when rolandic spikes are present. Rolandic spikes in patients with absence epilepsy may be a marker of additional cognitive challenges that physicians should be aware of.

Publications pattern of clinical epilepsy research in Saudi Arabia

Objective:

To assess the progress in the field clinical epilepsy in Saudi Arabia, by analyzing in depth the research output productivity and publication pattern, and to identify the current situation of epilepsy research and offer solutions.

Method:

Literature search strategy was designed to retrieve accessible articles that are related to epilepsy utilizing PubMed, Google Scholar, and Embase. The retrieved articles were analyzed with several parameters, then evaluated using Oxford Center of Evidence Based Medicine level of evidence scale.

Results:

Of all identified articles, 90 were conducted in Kingdom of Saudi Arabia and therefore were included. The included articles had a frequency of only 3.5 publications per year, and growth of 24.4% between the periods of 1990-2003 and 2004-2016. Only 13.3% of the articles were related to surgical epilepsy but the majority (86.7%) were related to medical epilepsy. Many articles (53.3%) were level III studies. The most common study design was retrospective studies in 35.6%, and the citations number ranged from 1–289 (Mean=7).

Conclusion:

Pattern of publications in clinical epilepsy researches revealed a slow growth rate in the frequency and a lower significance in the quality throughout the past 26 years. Active institutional and national promotion of clinical research is needed to help assess and therefore improve the quality of the provided epilepsy services.

Generalized epilepsies

Idiopathic generalized epilepsies (IGE) are characterized by normal background EEG activity and generalized interictal spike-and-wave discharges in the absence of any evidence of brain lesion. Absence epilepsies are the prototypes of IGEs. In childhood and juvenile absence epilepsies, by definition, all patients manifest absence seizures associated with an EEG pattern of generalized spike-wave (GSW) discharges. In juvenile myoclonic epilepsy, myoclonic jerks, usually affecting shoulders and arms bilaterally and appearing upon awakening, are the most characteristic clinical feature. Myoclonic jerks are accompanied on the EEG by generalized spike/polyspike-and-wave (GSW, GPWS) complexes at 3.5-6Hz. Idiopathic generalized epilepsy with generalized tonic-clonic seizures only is a broad and nonspecific category including all patients with generalized tonic-clonic seizures and an interictal EEG pattern of GSW discharges. Despite the strong heritability and the recent advances in genetic technology, the genetic basis of IGEs remains largely elusive and only in a small minority of patients with classic IGE phenotypes is a monogenic cause identified. Early myoclonic encephalopathy (EME), early infantile encephalopathy with suppression bursts, West syndrome, and Lennox-Gastaut syndrome, once classified among the generalized epilepsies, are now considered to be epileptic encephalopathies. Among them, only Lennox-Gastaut syndrome is characterized by prominent generalized clinical and EEG features.

Co-existence of Rolandic and 3 Hz Spike-Wave Discharges on EEG in Children with Epilepsy

OBJECTIVE

Benign epilepsy of childhood with central temporal spikes (BECTS) and absence epilepsy are common epilepsy syndromes in children with similar age of onset and favorable prognosis. However, the co-existence of the electrocardiogram (EEG) findings of rolandic spike and 3 Hz generalized spike-wave (GSW) discharges is extremely rare, with few cases reported in the literature. Our objective was to characterize the EEG findings of these syndromes in children in our center and review the electro-clinical features.

METHODS

All EEGs at BC Children's Hospital are entered in a database, which include EEG findings and clinical data. Patients with both centro-temporal spikes and 3 Hz GSW discharges were identified from the database and clinical data were reviewed.

RESULTS

Among the 43,061 patients in the database from 1992 to 2017, 1426 with isolated rolandic discharges and 528 patients with isolated 3 Hz GSW discharges were identified, and 20 (0.05%) patients had both findings: 3/20 had BECTS, and subsequently developed childhood absence epilepsy and 17/20 had no seizures characteristic for BECTS. At follow-up, 17 (85%) were seizure-free, 1 (5%) had rare, and 2 (10%) had frequent seizures.

CONCLUSIONS

This is the largest reported group of patients to our knowledge with the co-existence of rolandic and 3 Hz GSW discharges on EEGs in one institution, not drug-induced. As the presence of both findings is extremely rare, distinct pathophysiological mechanisms are likely. The majority had excellent seizure control at follow-up, similar to what would be expected for each type of epilepsy alone.

Compensatory reduction of Cav3.1 expression in thalamocortical neurons of juvenile rats of WAG/Rij model of absence epilepsy

Absence seizures are the non-convulsive form of generalized epilepsy critically dependent on T-type calcium channels (Cav3) in thalamic neurons. In humans, absences accompany only childhood or adolescent epileptic syndromes--though in its polygenic rat models WAG/Rij and GAERS the opposite developmental pattern is observed. Hereby we address this issue by transcriptional and functional study of thalamic Cav3 in juvenile (i.e., free of seizures) rats of the absence-prone WAG/Rij strain and their coevals of the maternal Wistar strain. First, we measured the low voltage-activated (LVA) Ca(2+) current in freshly isolated thalamocortical neurons from laterodorsal nucleus of thalamus. The difference between current densities in control (12.9 ± 1.8pA/pF) and absence epilepsy (7.9 ± 1.8pA/pF) groups reached ∼ 39%. Second, we assessed the contribution of different T-channel isoforms into the reduction of Cav3-mediated current in WAG/Rij juveniles by means of RT PCR. The expression of all three LVA calcium channels was revealed with the prevalence of G and I isoforms. The expression level of G isoform (Cav3.1) was 35% smaller in WAG/Rij strain if compared to the control animals while that of H and I isoforms (Cav3.2 and Cav3.3, respectively) remained stable. The weakened expression of Cav3.1 in juveniles of WAG/Rij rats could represent a compensatory mechanism determining the pattern of the age dependency in the disease manifestation by this model of absence epilepsy.

Idiopathic generalized epilepsy: Phenotypic and electroencephalographic observations in a large cohort from South India

PURPOSE

We studied the phenotype and electroencephalographic (EEG) features, and therapeutic aspects of idiopathic generalized epilepsies (IGEs) in South Indian population.

PATIENTS AND METHODS

This prospective cross-sectional hospital-based study was carried out on non-consecutive 287 patients (age 22.2 ± 7.7 years; M:F = 139:148) with IGE syndrome. Their clinical and EEG observations were analyzed.

RESULTS

Majority of the patients had onset of seizures <20 years of age (n = 178; 62%). Thirty one patients (10.8%) had family history of epilepsy. Nearly half of them (49.9%) had <5 years of duration of seizures. The type of IGEs included Juvenile myoclonic epilepsy (JME): 115 (40.1%); IGE with generalized tonic-clonic seizures (GTCS) only: 102 (39.02%); childhood absence epilepsy (CAE): 35 (12.2%); GTCS on awakening: 15 (5.2%); Juvenile absence epilepsy (JAE): 11 (3.8%); and unclassified seizures: 9 (3.1%). The triggering factors noted in 45% were sleep deprivation (20%), non-compliance and stress in 5% each. The EEG (n = 280) showed epileptiform discharges in about 50% of patients. Epileptiform discharges during activation was observed in 40/249 patients (16.1%): Hyperventilation in 32 (12.8%) and photic stimulation in 19 (7.6%). The seizures were well controlled with anti-epileptic drugs (AEDs) in 232 (80.8%) patients and among them, 225 (78.4%) patients were on monotherapy. Valproate (n = 131) was the most frequently prescribed as monotherapy.

CONCLUSIONS

This is one of the largest cohort of patients with IGE. This study reiterates the importance of segregating IGE syndrome and such analysis will aid to the current understanding and management.

Idiopathic Generalized Epilepsy with Absences: Syndrome Classification

In a cohort of 275 Caucasians with a broad IGE phenotype, patients with absences were classified. Criteria of the 1989 Commission on Classification of the International League Against Epilepsy for Childhood Absence Epilepsy (CAE 1989 criteria) were compared with the stricter criteria of the ILAE Task Force for Classification and Terminology (CAE 2005 criteria). Among the 129 patients with absences without significant myoclonus, 50 had juvenile absence epilepsy 44 had CAE according to the CAE 1989 criteria and only 30 had CAE according to the CAE 2005 criteria. We found a significantly better outcome in patients considered as CAE by the CAE 2005 criteria, compared with those excluded. Strict criteria for classification of absence syndromes leave many patients unclassified. However, diagnostic criteria used to classify CAE patients have prognostic significance. We propose that patients are classified as having benign CAE or as having CAE with the adverse prognostic factors indicated.

[Typical absence seizure: epidemiological and clinical characteristics and outcome]

OBJECTIVE

To analyze the epidemiological and clinical characteristics and outcome of absence epilepsy in the pediatric age group with the aim of facilitating its diagnosis in clinical practice.

PATIENTS AND METHODS

Information on epidemiological and clinical characteristics, complementary investigations, and outcome was collected from the medical records of 51 children with absence epilepsy. The criteria defined by the International League Against Epilepsy (ILAE) were used in the diagnosis.

RESULTS

Fifty-one percent of the patients had simple absence seizures and 49% had complex absence seizures. A total of 70.6% of the patients were school-aged children and the prevalence was greater among girls (72.5%). The mean age at onset was 7.5 +/- 2.7 years. In 80%, there were multiple seizures per day with a mean duration of 12 seconds. School performance was impaired in 19.6%. Ictal electroencephalogram showed generalized 3 Hz spike and slow wave complexes in 84.3%. Hyperventilation was positive in 98%, and intermittent photic stimulation was positive in 15.7%. The seizures were controlled by sodium valproate (mean dosage: 26 mg/kg/day) in 84.3% of the patients. In 43 patients antiepileptic drugs were withdrawn (mean duration: 3.3 +/- 0.6 years) but 3 patients relapsed.

CONCLUSIONS

Typical absences are a common type of epilepsy in the pediatric age group and generally begin in school-aged children. Absences may be difficult to detect and can impair learning. Treatment response is excellent. Nevertheless, because absences may be the first manifestation of severe forms of epilepsy syndromes, strict follow-up of these patients is essential.

Seizures of idiopathic generalized epilepsies

Idiopathic generalized epilepsies (IGEs) comprise at least 40% of epilepsies in the United States, 20% in Mexico, and 8% in Central America. Here, we review seizure phenotypes across IGE syndromes, their response to treatment and advances in molecular genetics that influence nosology. Our review included the Medline database from 1945 to 2005 and our prospectively collected Genetic Epilepsy Studies (GENESS) Consortium database. Generalized seizures occur with different and similar semiologies, frequencies, and patterns, ages at onset, and outcomes in different IGEs, suggesting common neuroanatomical pathways for seizure phenotypes. However, the same seizure phenotypes respond differently to the same treatments in different IGEs, suggesting different molecular defects across syndromes. De novo mutations in SCN1A in sporadic Dravet syndrome and germline mutations in SCN1A, SCN1B, and SCN2A in generalized epilepsies with febrile seizures plus have unraveled the heterogenous myoclonic epilepsies of infancy and early childhood. Mutations in GABRA1, GABRG2, and GABRB3 are associated with absence seizures, while mutations in CLCN2 and myoclonin/EFHC1 substantiate juvenile myoclonic epilepsy as a clinical entity. Refined understanding of seizure phenotypes, their semiology, frequencies, and patterns together with the identification of molecular lesions in IGEs continue to accelerate the development of molecular epileptology.

Practical Management Issues for Idiopathic Generalized Epilepsies

The idiopathic generalized epilepsies (IGE) are a group of epilepsies that are genetically determined, have no structural or anatomic cause, and usually begin early in life. Neurologic examination, intelligence, and imaging studies are normal, and EEG shows only epileptiform abnormalities (i.e., no abnormal slow activity or evidence for diffuse encephalopathy). In some IGE, the genetic substrate has been identified, whereas in most, it remains unknown. Depending on the age at onset and predominant seizure type, individual subtypes of IGE (syndromes) are defined. However, overall, there are more similarities than there are differences among the various subtypes, and the IGE are best viewed as a spectrum or continuum of conditions. In general, IGE respond to treatment, with 80-90% becoming fully controlled. However, not all antiepileptic drugs (AED) are equally effective in IGE. Some AED are ill advised because they either do not work or exacerbate seizure types other than generalized tonic-clonic (GTC) seizures, that is, absence and myoclonic seizures. These include carbamazepine, oxcarbazepine, phenytoin, gabapentin, and tiagabine. Their use is the main cause of "pseudo-intractability," and at least in the United States where PHT and CBZ are the most commonly used AEDs, patients with IGE are often on inadequate medications. For patients with clear IGE, the drug of choice is generally valproic acid because it effectively controls absence myoclonic seizures and GTC seizures. Second-line drugs (when first-line drugs fail or are not tolerated) may include benzodiazepines, but the use of second-line drugs is evolving rapidly. Some of the newer AEDs are considered broad spectrum, meaning that they work in IGE and focal epilepsies, although the evidence is largely preliminary at this point. These newer AEDs include lamotrigine, topiramate, levetiracetam, and zonisamide.

Absence seizures in succinic semialdehyde dehydrogenase deficient mice: a model of juvenile absence epilepsy

The succinic semialdehyde dehydrogenase (SSADH) null mouse represents a viable animal model for human SSADH deficiency and is characterized by markedly elevated levels of both gamma-hydroxybutyric acid (GHB) and gamma-aminobutyric acid (GABA) in brain, blood, and urine. GHB is known to induce absence-like seizures and absence seizures have been reported to occur in children with SSADH deficiency. We tested the hypothesis that the phenotype of the SSADH(-/-) mouse shows absence-like seizures because of the inordinately high levels of GHB in the brain of this mutant animal. Sequential electrocorticographic (ECoG) and prolonged video ECoG recordings from chronically implanted electrodes were done on SSADH(-/-), SSADH(+/-), and SSADH(+/+) mice from postnatal day (P) 10 to (P) 21. Spontaneous, recurrent absence-like seizures appeared in the SSADH(-/-) during the second week of life and evolved into generalized convulsive seizures late in the third week of life that were associated with an explosive onset of status epilepticus which was lethal. The seizures in SSADH null mice were consistent with typical absence seizures in rodent with 7 Hz spike-and-wave discharge (SWD) recorded from thalamocortical circuitry, the onset/offset of which was time-locked with ictal behavior characterized by facial myoclonus, vibrissal twitching and frozen immobility. The absence seizures became progressively more severe from P14 to 18 at which time they evolved into myoclonic and generalized convulsive seizures that progressed into a lethal status epilepticus. The absence seizures in SSADH(-/-) were abolished by ethosuximide (ETX) and the GABA(B)R antagonist CGP 35348. The seizure phenotype in the SSADH(-/-) recapitulates that observed in human SSADH deficiency. Hence, SSADH(-/-) may be used to investigate the molecular mechanisms that underpin the pathogenesis of absence and generalized tonic-clonic seizures associated with SSADH deficiency. As well, the SSADH(-/-) may represent a unique animal model of the transition from absence to myoclonic and generalized convulsive seizures that is observed in up to 80% of patients with juvenile absence epilepsy.

Clinical trials for treatment of primary generalized epilepsies

PURPOSE

To review the current state of knowledge of the treatment of primary (idiopathic) generalized epilepsy syndromes based on the efficacy results of clinical trials, to highlight obstacles in the design of these trials, and to suggest solutions for future research.

METHODS

Published reports of controlled clinical trials, as well as large or significant uncontrolled trials of treatments for these syndromes, were reviewed. Trials were selected for discussion based on their importance or their illustration of design issues.

RESULTS

Only a few randomized, controlled trials of therapy for these syndromes exist. Conclusions based on this Class I data include efficacy in absence epilepsies for ethosuximide, valproate, and lamotrigine, and for eight drugs for primary generalized tonic-clonic seizures. Many commonly accepted therapeutic strategies are not based on formal data. No controlled data exist for uncommon syndromes.

CONCLUSIONS

More clinical trials of therapies for primary generalized epilepsies are needed. To overcome design obstacles, better funding, multicenter cooperation, inclusion of children, study designs requiring fewer patients, equivalent-control designs, use of EEG and video seizure counting, and better syndrome identification will be required.

Syndromic classification of patients with typical absence seizures

The aim of this study is to compare ILAE classification (1989) and Panayiotopoulos' criteria (1997) for absence epilepsies. We studied 455 typical absences (ILAE, 1981) by video-EEG in 43 patients with normal neurological and neuroradiological examinations and interictal EEG with spike-wave complexes higher than 2.5Hz. Syndromic diagnosis was possible in 60.5% and 67.4% of the patients using ILAE classification and Panayiotopoulos' proposal, respectively. According to ILAE criteria 19 patients had childhood absence epilepsy (CAE), five juvenile absence epilepsy (JAE), one juvenile myoclonic epilepsy (JME) and one epilepsy with specific modes of seizure precipitation. According to Panayiotopoulos' proposal, 10 had CAE, 14 JAE, one JME, three myoclonic absence epilepsy and one eyelid myoclonia with absences. We conclude that Panayiotopoulos' criteria and ILAE classification for absence epilepsies, which did not allow for the classification of 32.6% and 39.5% of cases, respectively, were still insufficient to classify all patients under specific diagnosis.

Natural history of absence epilepsy in children

Absence seizures may be seen in a variety of epileptic syndromes in childhood. Identification of the specific syndrome is important to determine medical prognosis. With childhood absence epilepsy, approximately two thirds of children can be expected to enter long-term remission, while in juvenile absence epilepsy, seizure control is often achieved, however, lifelong treatment is usually required. Other absence syndromes have a poorer prognosis, with lower rates of seizure control and remission. Psychosocial outcome is often poor, even in patients with more benign forms of absence epilepsy. Remission of epilepsy does not preclude psychosocial morbidity.

Treatment of typical absence seizures and related epileptic syndromes

Typical absences are brief (seconds) generalised seizures of sudden onset and termination. They have 2 essential components: clinically, the impairment of consciousness (absence) and, generalised 3 to 4Hz spike/polyspike and slow wave discharges on electroencephalogram (EEG). They differ fundamentally from other seizures and are pharmacologically unique. Their clinical and EEG manifestations are syndrome-related. Impairment of consciousness may be severe, moderate, mild or inconspicuous. This is often associated with motor manifestations, automatisms and autonomic disturbances. Clonic, tonic and atonic components alone or in combination are motor symptoms; myoclonia, mainly of facial muscles, is the most common. The ictal EEG discharge may be consistently brief (2 to 5 seconds) or long (15 to 30 seconds), continuous or fragmented, with single or multiple spikes associated with the slow wave. The intradischarge frequency may be constant or may vary (2.5 to 5Hz). Typical absences are easily precipitated by hyperventilation in about 90% of untreated patients. They are usually spontaneous, but can be triggered by photic, pattern, video games stimuli, and mental or emotional factors. Typical absences usually start in childhood or adolescence. They occur in around 10 to 15% of adults with epilepsies, often combined with other generalised seizures. They may remit with age or be lifelong. Syndromic diagnosis is important for treatment strategies and prognosis. Absences may be severe and the only seizure type, as in childhood absence epilepsy. They may predominate in other syndromes or be mild and nonpredominant in syndromes such as juvenile myoclonic epilepsy where myoclonic jerks and generalised tonic clonic seizures are the main concern. Typical absence status epilepticus occurs in about 30% of patients and is more common in certain syndromes, e.g. idiopathic generalised epilepsy with perioral myoclonia or phantom absences. Typical absence seizures are often easy to diagnose and treat. Valproic acid, ethosuximide and lamotrigine, alone or in combination, are first-line therapy. Valproic acid controls absences in 75% of patients and also GTCS (70%) and myoclonic jerks (75%); however, it may be undesirable for some women. Similarly, lamotrigine may control absences and GTCS in possibly 50 to 60% of patients, but may worsen myoclonic jerks; skin rashes are common. Ethosuximide controls 70% of absences, but it is unsuitable as monotherapy if other generalised seizures coexist. A combination of any of these 3 drugs may be needed for resistant cases. Low dosages of lamotrigine added to valproic acid may have a dramatic beneficial effect. Clonazepam, particularly in absences with myoclonic components, and acetazolamide may be useful adjunctive drugs.