How to diagnose and classify idiopathic (genetic) generalized epilepsies.

Idiopathic or genetic generalized epilepsies (IGE) constitute an electroclinically well-defined group that accounts for almost one third of all people with epilepsy. They consist of four well-established syndromes and some other rarer phenotypes. The main four IGEs are juvenile myoclonic epilepsy, childhood absence epilepsy, juvenile absence epilepsy and IGE with generalized tonic-clonic seizures alone. There are three main seizure types in IGE, namely generalized tonic-clonic seizures, typical absences and myoclonic seizures, occurring either alone or in any combination. Diagnosing IGEs requires a multidimensional approach. The diagnostic process begins with a thorough medical history with a specific focus on seizure types, age at onset, timing and triggers. Comorbidities and family history should be questioned comprehensively. The EEG can provide valuable information for the diagnosis, including specific IGE syndromes, and therefore contribute to their optimal pharmacological treatment and management.

Seizures, syndromes, and etiologies in childhood epilepsy: The International League Against Epilepsy 1981, 1989, and 2017 classifications used in a population-based cohort.

OBJECTIVE: The study provides updated information about the distribution of seizures, epilepsies, and etiologies of epilepsy in the general child population, and compares the old and new classification systems from the International League Against Epilepsy (ILAE). METHODS: The study platform was the Norwegian Mother and Child Cohort Study. Cases of epilepsy were identified through registry linkages and sequential parental questionnaires. Epilepsy diagnoses were validated using a standardized protocol, and seizures, epilepsies, and etiologies were classified according to the old (ILAE 1981/1989) and new (ILAE 2017) classifications. Information was collected through medical record reviews and/or parental telephone interviews. RESULTS: The study population included 112,744 children aged 3-13 years at the end of follow-up on December 31, 2012. Of these, there were 606 children with epilepsy (CWE). Distribution of seizure types varied by age of onset. Multiple seizure types were common with early onset. Focal epilepsies were the most common, occurring in 317 per 100,000 children in the study population and in 59% of CWE. Generalized epilepsies were found in 190 per 100,000 (35% of CWE). CWE with onset during the first 2 years of life had an even distribution of focal and generalized epilepsies, whereas focal epilepsies became dominant at later ages of onset. A definite cause of epilepsy had been demonstrated in 33% of CWE. The ILAE 1989 classification allowed for a broad syndrome category in 93% of CWE and a defined epileptic syndrome in 37%. With the ILAE 2017 classification, 41% of CWE had a defined epileptic syndrome and 63% had either a defined syndrome or structural-metabolic etiology. SIGNIFICANCE: The distribution of seizures and epilepsies is strongly dependent on age of onset. Despite diagnostic advances, the causes of epilepsy are still unknown in two-thirds of CWE. The ILAE 2017 classifications allow for a higher precision of diagnoses, but at the expense of leaving more epilepsies classifiable only at the mode of onset level.

Clasificación de las epilepsias generalizadas idiopáticas en mayores de 16 años / Classification of idiopathic generalised epilepsies in patients over 16 years of age

Introducción. Las epilepsias generalizadas idiopáticas (EGI) son un conjunto de síndromes electroclínicos con distintos fenotipos. Nuestro objetivo es analizar dichos fenotipos en pacientes mayores de 16 años. Pacientes y métodos. Analizamos retrospectivamente una serie de pacientes con EGI. Los clasificamos en epilepsia de ausencias infantil (EAI), epilepsia de ausencias juvenil (EAJ), epilepsia mioclónica juvenil (EMJ), epilepsia con crisis tonicoclónicas sólo (ECTC), epilepsia con ausencias y mioclonías palpebrales (EAM) y epilepsia fotogénica pura (EF). Resultados. Incluimos 308 pacientes, mayoritariamente mujeres (56,8%). La EMJ fue más prevalente (40,9%), seguida de la ECTC (30%), la EAJ (10%), la EAM (8,7%), la EAI (7,7%) y la EF (1,6%). Los tipos de crisis que presentaron más pacientes fueron las tonicoclónicas (89,6%), las mioclónicas (45,4%), las ausencias (31,4%), las crisis reflejas (13,3%), las mioclonías palpebrales (12,6%), las crisis psicógenas no epilépticas (3,6%) y el estado epiléptico (1,9%). Todos tenían descargas punta-onda generalizada en el electroencefalograma (EEG). El 19,2% presentó descargas asimétricas y el 28,2%, respuesta fotoparoxística. Observamos diferencias entre síndromes en politerapia (p < 0,0001), retirada de tratamiento (p = 0,01) y estar libres de crisis por encima de los 50 años (p = 0,004). Conclusiones. La EMJ fue la EGI más frecuente. Las crisis tonicoclónicas generalizadas fueron el tipo de crisis que presentaron más pacientes, seguidas de las mioclónicas, las ausencias y las crisis reflejas. El EEG mostró en más de una cuarta parte de los pacientes una respuesta fotoparoxística, y en uno de cada cinco, anomalías asimétricas. Se observaron diferencias según el síndrome en politerapia, persistencia de crisis y retirada de tratamiento (AU)

Introduction. Idiopathic generalised epilepsies (IGE) are a set of electroclinical syndromes with different phenotypes. Our aim is to analyse those phenotypes in patients over 16 years of age. Patients and methods. We conducted a retrospective analysis of a series of patients with IGE. They were classified as childhood absence epilepsy (CAE), juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), epilepsy with tonicclonic seizures only (TCSE), epilepsy with eyelid myoclonias and absences (EMA) and pure photogenic epilepsy (PE). Results. We included 308 patients, the majority females (56.8%), in our study. JME was the most prevalent (40.9%), followed by TCSE (30%), JAE (10%), EMA (8.7%), CAE (7.7%) and PE (1.6%). The types of seizures presented by the most patients were tonic-clonic (89.6%), myoclonic (45.4%), absence (31.4%), reflex seizures (13.3%), eyelid myoclonias (12.6%), non-epileptic psychogenic seizures (3.6%) and status epilepticus (1.9%). They all had generalised spike-and-wave discharges in the electroencephalogram (EEG). 19.2% presented asymmetrical discharges and 28.2% showed a photoparoxysmal response. We observed differences between syndromes in polytherapy (p < 0.0001), withdrawal of therapy (p = 0.01) and being seizure-free beyond the age of 50 (p = 0.004). Conclusions. JME was the most frequent. Generalised tonic-clonic seizures were the type of seizures presented by the most patients, followed by myoclonic, absent and reflex seizures. The EEG showed a photoparoxysmal response in over a quarter of the patients, and one in five displayed asymmetrical anomalies. Differences were observed according to the syndrome in polytherapy, persistence of seizures and withdrawal of treatment (AU)

The classification and differential diagnosis of absence seizures with short-term video-EEG monitoring during childhood.

Absence seizures are idiopathic epilepsies characterized by impairment of consciousness and generalized 2.5-4 Hz spike and slow wave discharges. This prospective study was performed to classify and define properties of subgroups of absence epilepsies. We included 31 patients, of whom seven were in the differential diagnosis group. On admission, absence epilepsy provisional diagnosis was considered in 16 patients clinically and in the other 15 patients based on routine EEG findings. Ictal EEGs were recorded by video-EEG monitoring in 23 of the patients (totally 202 ictal recordings). Patients were diagnosed as childhood absence epilepsy (n=8), juvenile absence epilepsy (n=10), juvenile myoclonic epilepsy (n=3), eyelid myoclonia with absences (n=2), and perioral myoclonia with absences (n=1). Neuroimaging, video-EEG monitoring and especially ictal recordings are important for classification of epilepsies in addition to history, physical examination and routine EEG findings. Video-EEG monitoring is required to classify, to make differential diagnosis and to determine the treatment plan and prognosis.

Early-onset pure absence epilepsy: a distinct epileptic syndrome.

UNLABELLED: Early-onset pure absence epilepsy has not yet considered in the International League Against Epilepsy classification, but several reports have supported its existence as a distinct epileptic syndrome primarily manifesting with typical absences in early childhood. This review summarizes the current understanding on this epilepsy. CONCLUSIONS: Early-onset pure absence epilepsy is a distinct epilepsy characterized by absences starting from a few months to 4 years of age, normal early psychomotor development, good antiepileptic drug seizure control and normal intellectual outcome.

Absence seizures: a review of recent reports with new concepts.

Absence seizures with bilateral spike-wave (SW) complexes at 3Hz are divided into the childhood form, with onset at around 6 years of age, and the juvenile form, with onset usually at 12 years of age. These seizures typically last 9-12s and, at times, are activated by hyperventilation and occasionally by photic stimulation. Generalized tonic-clonic (GTC) seizures may also occur, especially in the juvenile form. There may be cognitive changes, in addition to linguistic and behavioral problems. Possible mechanisms for epileptogenesis may involve GABAergic systems, but especially T-calcium channels. The thalamus, especially the reticular nucleus, plays a major role, as does the frontal cortex, mainly the dorsolateral and orbital frontal areas, to the extent that some investigators have concluded that absence seizures are not truly generalized, but rather have selective cortical networks, mainly ventromesial frontal areas and the somatosensory cortex. The latter network is a departure from the more popular concept of a generalized epilepsy. Between the "centrencephalic" and "corticoreticular" theories, a "unified" theory is presented. Proposed genes include T-calcium channel gene CACNA1H, likely a susceptible gene in the Chinese Han population and a contributory gene in Caucasians. Electroencephalography has revealed an interictal increase in prefrontal activity, essential for the buildup of the ictal SW complexes maximal in that region. Infraslow activity can also be seen during ictal SW complexes. For treatment, counter to common belief, ethosuximide may not increase GTC seizures, as it reduces low-threshold T-calcium currents in thalamic neurons. Valproic acid and lamotrigine are also first-line medications. In addition, zonisamide and levetiracetam can be very helpful in absence epilepsy.

[Current clinical-neurophysiological findings in absence epilepsies]. / Aktuelle klinisch-neurophysiologische Befunde bei Absence-Epilepsien.

According to the international classification of epileptic seizures (1981) generalized seizures present ictal signs indicating seizure onset in both hemispheres whereas focal seizures present ictal signs pointing to one hemisphere at seizure onset. Recent neurophysiological studies using MEG, EEG, and fMRI suggest that in case of idiopathic generalized absence epilepsies, activity predominates in specific networks, which include frontoparietal cortical as well as subcortical areas of both hemispheres. In these network regions, epileptic activity can occur circumscribed and focal as spike or spike-wave activity but also widely distributed, bilateral, and homologous. As a consequence to the classification of "generalized" epileptic seizures and syndromes, it might be possible to distinguish a subgroup: regional bilateral homologous epilepsies. These must be distinguished from a pure culture of focal frontal lobe epilepsies, which can also be accompanied by the lead symptom of absences.

The evaluation of interictal focal EEG findings in adult patients with absence seizures.

PURPOSE: To investigate the focal interictal EEG abnormalities in adult patients with absence seizures (ASs) and to identify their clinical, EEG and semiological correlates. METHODS: Fifty patients older than 18 years, diagnosed as having IGE with AS documented with ictal recordings. Interictal focal sharp or spike-waves and strictly focal paroxysmal slow activity were considered as focal EEG features. The patients having focal EEG features were classified as "Group I", whereas the remaining of them was classified as "Group II". RESULTS: We observed focal findings in 34% of the patients, mainly in frontotemporal (41%), and frontal (29%) regions. There were no significant differences with respect to the clinical parameters such as sex, epilepsy duration, positive family history and the age of the onset between the groups. Psychiatric co-morbidities were significantly higher in Group I when compared to Group II (P=0.00). Accompanying automatisms were higher in Group I, whereas eye deviation during absences was higher in Group II. In Group I, the asymmetry of the ictal discharges was more frequently observed. Focal EEG features were more frequently seen in juvenile absence epilepsy syndrome, without reaching a significance level. CONCLUSION: The focal findings in adult absence epilepsy patients could have some unknown etio-pathogenetic and prognostic implications. We emphasize the cautious interpretation of isolated interictal focal EEG abnormalities to prevent a wrong diagnosis of focal epilepsy in patients who may indeed suffer from generalized epilepsy.

Frontal-onset absences in children: associated with worse outcome? A replication study.

We studied the clinical and electroencephalographic features in 30 children who were diagnosed with childhood absence epilepsy. According to their EEG pattern we divided the 30 children into two groups: group A: 11 children with classical absences whose ictal EEG showed primary generalized spikes and waves and group B: 19 children with frontal onset of the EEG epileptic abnormalities ('frontal group'). In the frontal group, more frequently complex absences were seen. Although the majority of children responded very well to valproate monotherapy, ethosuximide has to be added in 3 children of the frontal group to achieve seizure freedom. In the frontal group, also more learning and behavioural problems were encountered. This study largely confirms a previous study of Lagae et al. [Lagae L, Pauwels J, Monte B, Verhelle J, Vervisch J. Frontal absences in children. Eur J Pediatr Neurol 2001;5:243-251]. It seems that frontal onset absences constitute a specific subtype within the childhood absence epilepsies.

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.

Absence epilepsy in childhood: electroencephalography (EEG) does not predict outcome.

Absence epilepsy is a form of generalized epilepsy commonly seen in children. The clinician is often presented with a patient whose electroencephalogram does not fit the typical absence pattern. The purpose of this study is to more closely examine both typical and atypical absence variants and their outcome. A retrospective chart review was performed on children diagnosed with absence epilepsy over the past 5 years at the University of Alberta. A total of 119 patients were reviewed. Patients were classified with typical or atypical absence seizures following International League Against Epilepsy criteria and electroencephalography (EEG) characteristics. Clinical seizure characteristics, magnetic resonance imaging (MRI), initial response to treatment, and outcome were examined. Seizure characteristics were similar in both the typical and atypical absence groups. Aura, complex automatisms, changes in tone, and incontinence were seen in both groups, although status epilepticus was found only in the atypical group. Associated comorbid conditions such as attention-deficit hyperactivity disorder (ADHD), learning disorders, and enuresis were found equally in both groups. Developmental delay was found more often in the atypical group. Of the typical group, 83% responded to an initial antiepileptic drug (either valproic acid or ethosuximide), whereas only 51% of the atypical group came under control. Remission at 2 years however, was similar between groups, with 76% of the typical group and 71% of the atypical group completely seizure free. Absence seizures in childhood, both typical and atypical, share similar clinical and electroencephalographic features and appear to be part of a continuum. Associated comorbid features such as ADHD, learning disorders, and developmental delay are also seen in both groups. The outcome for both types is excellent, although the atypical variants may be initially more difficult to control.

Typical versus atypical absence seizures: network mechanisms of the spread of paroxysms.

PURPOSE: Typical absence seizures differ from atypical absence seizures in terms of semiology, EEG morphology, network circuitry, and cognitive outcome, yet have the same pharmacological profile. We have compared typical to atypical absence seizures, in terms of the recruitment of different brain areas. Our initial question was whether brain areas that do not display apparent paroxysmal discharges during typical absence seizures, are affected during the ictal event in terms of synchronized activity, by other, distant areas where seizure activity is evident. Because the spike-and-wave paroxysms in atypical absence seizures invade limbic areas, we then asked whether an alteration in inhibitory processes in hippocampi may be related to the spread seizure activity beyond thalamocortical networks, in atypical seizures. METHODS: We used two models of absence seizures in rats: one of typical and the other of atypical absence seizures. We estimated phase synchronization, and evaluated inhibitory transmission using a paired-pulse paradigm. RESULTS: In typical absence seizures, we observed an increase in synchronization between hippocampal recordings when spike-and-wave discharges occurred in the cortex and thalamus. This indicates that seizure activity in the thalamocortical circuitry enhances the propensity of limbic areas to synchronize, but is not sufficient to drive hippocampal circuitry into a full paroxysmal discharge. Lower paired-pulse depression was then found in hippocampus of rats that displayed atypical absence seizures. CONCLUSIONS: These observations suggest that circuitries in brain areas that do not display apparent seizure activity become synchronized as seizures occur within thalamocortical circuitry, and that a weakened hippocampal inhibition may predispose to develop synchronization into full paroxysms during atypical absence seizures.