Differentiation of typical absence seizures in epileptic syndromes. A video EEG study of 224 seizures in 20 patients

Childhood Absence Epilepsy- Electroclinical Profile and Prevalence of Attention-Deficit/Hyperactivity Disorder Among a Cohort of 47 Children

BACKGROUND

We aimed to find the proportion of attention-deficit/hyperactivity disorder (ADHD) among children with childhood absence epilepsy (CAE) and to describe their electroclinical features.

METHODS

Video electroencephalography (EEG) was performed on 47 children who fulfilled International League Against Epilepsy criteria for CAE. These children were also assessed for the presence of ADHD.

RESULTS

Of the 47 children, 27 (57%) met criteria for the diagnosis of ADHD. Majority (74%) of them had inattentive type of ADHD. Age at onset of absences ranged from three to 12 years (mean 7.2 ± 2.47). We analyzed 219 seizures (154 electroclinical and 65 electrographic). The average seizure duration was 7.1 seconds (range 1 to 38 [S.D. 5.81]). Of the 154 clinical absences, ictal discharges were less than or equal to two seconds in nine of 154 (5.8%); greater than two to less than or equal to four seconds in 33 of 154 (21.4%), and longer than 20 seconds in 11 of 154 (7%). The longest duration of ictal discharge recorded was 38 seconds, and the shortest duration was one second. The onset of ictal discharge had a "lead in" focus in 81% (177 of 219).

CONCLUSIONS

The proportion of ADHD among children with CAE is high. A "lead in" focus of the generalized ictal discharges was observed frequently, lending support to the theory that the origin of seizure discharges in CAE is indeed cortical. The shortest ictal discharge recorded was one second.

Relationship Between Electroencephalography and Seizure Outcome in Typical Absence Seizures in Children

BACKGROUND

Typical absence seizures (TAS) are seen in idiopathic generalized epilepsy. Electroencephalography (EEG) contributes to syndrome characterization and counseling in an area where genetics does not currently play a significant role. Prominent interictal EEG findings are seen in juvenile absence epilepsy (JAE) and are thus thought to be associated with less favorable outcome in any TAS case despite lack of evidence. Our study evaluates EEG findings and their association with seizure outcomes in children with TAS.

METHODS

Retrospective cohort study of 123 children over 10 years with extensive EEG analysis and medical record review. Phone interviews ascertained longer-term outcomes. EEG reviewers were unaware of outcomes.

RESULTS

Total cohort included 123 children with phone review completed in 98. Median follow-up was 5 years 9 months. Seizure freedom was seen in 59% off antiseizure medicines (ASMs). Interictal findings included focal discharges in 29%, fragments of spike-wave (SW) discharges in 82.1%, and generalized interictal discharges in 63.4%. Interictal SW was more likely in those who slept (100%, 18 of 18) versus those who did not (57%, 60 of 105) (P < 0.001). Outcome analysis found no associations between focal or generalized interictal findings and seizure freedom, relapse off ASM, occurrence of other seizure types, or response to first ASM.

CONCLUSION

Focal and generalized interictal EEG discharges are common in children with TAS and are not associated with poorer outcomes. These interictal findings were traditionally associated with JAE rather than childhood absence epilepsy and were thus believed to be associated with potentially poorer outcome, which is probably not the case.

Quantitative EEG analysis in typical absence seizures: unveiling spectral dynamics and entropy patterns

A typical absence seizure is a generalized epileptic event characterized by a sudden, brief alteration of consciousness that serves as a hallmark for various generalized epilepsy syndromes. Distinguishing between similar interictal and ictal electroencephalographic (EEG) epileptiform patterns poses a challenge. However, quantitative EEG, particularly spectral analysis focused on EEG rhythms, shows potential for differentiation. This study was designed to investigate discernible differences in EEG spectral dynamics and entropy patterns during the pre-ictal and post-ictal periods compared to the interictal state. We analyzed 20 EEG ictal patterns from 11 patients with confirmed typical absence seizures, and assessed recordings made during the pre-ictal, post-ictal, and interictal intervals. Power spectral density (PSD) was used for the quantitative analysis that focused on the delta, theta, alpha, and beta bands. In addition, we measured EEG signal regularity using approximate (ApEn) and multi-scale sample entropy (MSE). Findings demonstrate a significant increase in delta and theta power in the pre-ictal and post-ictal intervals compared to the interictal interval, especially in the posterior brain region. We also observed a notable decrease in entropy in the pre-ictal and post-ictal intervals, with a more pronounced effect in anterior brain regions. These results provide valuable information that can potentially aid in differentiating epileptiform patterns in typical absence seizures. The implications of our findings are promising for precision medicine approaches to epilepsy diagnoses and patient management. In conclusion, our quantitative analysis of EEG data suggests that PSD and entropy measures hold promise as potential biomarkers for distinguishing ictal from interictal epileptiform patterns in patients with confirmed or suspected typical absence seizures.

Outcome of Absence Epilepsy With Onset at 8-11 Years of Age: Watershed Ages When Syndromes Overlap

Introduction: Absence seizures occur in various epilepsy syndromes, including childhood and juvenile absence epilepsy and juvenile myoclonic epilepsy. When children present with absence seizures at ages when syndromes overlap, initial syndrome designation is not always possible, making early prognostication challenging. For these children, the study objective is to determine clinical and initial electroencephalograph (EEG) findings to predict the development of generalized tonic-clonic seizures, which is a factor that affects outcome. Methods: Children with new-onset absence seizures between 8 and 11 years of age with at least 5 years of follow-up data were studied through the review of medical records and initial EEG tracings. Results: Ninety-eight patients were included in the study. The median age of absence seizure onset was 9 years (interquartile range [IQR] = 8.00, 10.00) and follow-up was 15 years (IQR = 13.00, 18.00). Forty-six percent developed generalized tonic-clonic seizures and 20% developed myoclonic seizures. On multiple regression analysis, a history of myoclonic seizures, anxiety, as well as bifrontal slowing and mild background slowing on initial EEG (P < .05) were associated with generalized tonic-clonic seizures. Although not statistically significant, a shorter duration of shortest EEG burst on baseline EEG was also associated with generalized tonic-clonic seizures. Conclusion: On initial EEG, bifrontal and background slowing and myoclonic seizures and anxiety are associated with developing generalized tonic-clonic seizures, which is of prognostic significance when early syndrome designation is difficult.

Thalamocortical circuits in generalized epilepsy: Pathophysiologic mechanisms and therapeutic targets

Generalized epilepsy affects 24 million people globally; at least 25% of cases remain medically refractory. The thalamus, with widespread connections throughout the brain, plays a critical role in generalized epilepsy. The intrinsic properties of thalamic neurons and the synaptic connections between populations of neurons in the nucleus reticularis thalami and thalamocortical relay nuclei help generate different firing patterns that influence brain states. In particular, transitions from tonic firing to highly synchronized burst firing mode in thalamic neurons can cause seizures that rapidly generalize and cause altered awareness and unconsciousness. Here, we review the most recent advances in our understanding of how thalamic activity is regulated and discuss the gaps in our understanding of the mechanisms of generalized epilepsy syndromes. Elucidating the role of the thalamus in generalized epilepsy syndromes may lead to new opportunities to better treat pharmaco-resistant generalized epilepsy by thalamic modulation and dietary therapy.

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.

Neurophysiological signatures reflect differences in visual attention during absence seizures

OBJECTIVE

Absences affect visual attention and eye movements variably. Here, we explore whether the dissimilarity of these symptoms during absences is reflected in differences in electroencephalographic (EEG) features, functional connectivity, and activation of the frontal eye field.

METHODS

Pediatric patients with absences performed a computerized choice reaction time task, with simultaneous recording of EEG and eye-tracking. We quantified visual attention and eye movements with reaction times, response correctness, and EEG features. Finally, we studied brain networks involved in the generation and propagation of seizures.

RESULTS

Ten pediatric patients had absences during the measurement. Five patients had preserved eye movements (preserved group) and five patients showed disrupted eye movements (unpreserved group) during seizures. Source reconstruction showed a stronger involvement of the right frontal eye field during absences in the unpreserved group than in the preserved group (dipole fraction 1.02% and 0.34%, respectively, p < 0.05). Graph analysis revealed different connection fractions of specific channels.

CONCLUSIONS

The impairment of visual attention varies among patients with absences and is associated with differences in EEG features, network activation, and involvement of the right frontal eye field.

SIGNIFICANCE

Assessing the visual attention of patients with absences can be usefully employed in clinical practice for tailored advice to the individual patient.

Higher-order thalamic nuclei facilitate the generalization and maintenance of spike-and-wave discharges of absence seizures

Spike-and-wave discharges (SWDs), generated by the cortico-thalamo-cortical (CTC) network, are pathological, large amplitude oscillations and the hallmark of absence seizures (ASs). SWDs begin in a cortical initiation network in both humans and animal models, including the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), where it is located in the primary somatosensory cortex (S1). The behavioral manifestation of an AS occurs when SWDs spread from the cortical initiation site to the whole brain, however, the mechanisms behind this rapid propagation remain unclear. Here we investigated these processes beyond the principal CTC network, in higher-order (HO) thalamic nuclei (lateral posterior (LP) and posterior (PO) nuclei) since their diffuse connectivity and known facilitation of intracortical communications make these nuclei key candidates to support SWD generation and maintenance. In freely moving GAERS, multi-site LFP in LP, PO and multiple cortical regions revealed a novel feature of SWDs: during SWDs there are short periods (named SWD-breaks) when cortical regions far from S1, such the primary visual cortex (V1), become transiently unsynchronized from the ongoing EEG rhythm. Inactivation of HO nuclei with local muscimol injections or optogenetic perturbation of HO nuclei activity increased the occurrence of SWD-breaks and the former intervention also increased the SWD propagation-time from S1. The neural underpinnings of these findings were explored further by silicon probe recordings from single units of PO which uncovered two previously unknown groups of excitatory neurons based on their burst firing dynamics at SWD onset. Moreover, a switch from tonic to burst firing at SWD onset was shown to be an important feature since it was much less prominent for non-generalized events, i.e. SWDs that remained local to S1. Additionally, one group of neurons showed a reverse of this switch during SWD-breaks, demonstrating the importance of this firing pattern throughout the SWD. In summary, these results support the view that multiple HO thalamic nuclei are utilized at SWD onset and contribute to cortical synchrony throughout the paroxysmal discharge.

Pretreatment electroencephalographic features in patients with childhood absence epilepsy

OBJECTIVE

To analyze the ictal and interictal electroencephalographic (EEG) features in newly diagnosed childhood absence epilepsy (CAE) and determine the association between seizure onset topography, interictal focal spike-wave discharges (FSWDs) and accompanying clinical features of absence seizures.

METHODS

The authors searched the EEG database for a definite diagnosis of CAE according to ILAE 2017 criteria. Video-EEGs of untreated pediatric patients during sleep and wakefulness were evaluated retrospectively.

RESULTS

The study included 47 patients (25 males, 22 females). Interictal FSWDs were observed in 49% of patients with CAE during wakefulness and in 85.1% during sleep (p = 0.001). Interictal FSWDs were most frequently observed in the frontal regions (awake: 34%; asleep: 74.5%), followed by the posterior temporoparietooccipital region (awake: 21.2%; asleep: 36.1%), and the centrotemporal region (awake: 6.4%; asleep: 8.5%). Eleven patients (23.4%) had polyspikes during sleep. Both bilateral symmetric and asymmetric seizure onset were noted in 32%, whereas focal seizure onset was observed in 14.9% of the patients. Absence seizures with and without motor components were seen in 72.3% and 61.7% of patients, respectively, and in 33% of patients both occurred. There were no associations between the existence of interictal FSWDs, focal/asymmetric seizure onset, and absence seizures with and/or without motor components.

CONCLUSION

Asymmetric and/or focal seizure onset, interictal FSWDs, and absence seizures with motor components are commonly observed in drug-naive CAE. This study found no association between seizure onset topography, interictal FSWDs, and semiological features of absence seizures.

Seizure semiology: ILAE glossary of terms and their significance

This educational topical review and Task Force report aims to address learning objectives of the International League Against Epilepsy (ILAE) curriculum. We sought to extract detailed features involving semiology from video recordings and interpret semiological signs and symptoms that reflect the likely localization for focal seizures in patients with epilepsy. This glossary was developed by a working group of the ILAE Commission on Diagnostic Methods incorporating the EEG Task Force. This paper identifies commonly used terms to describe seizure semiology, provides definitions, signs and symptoms, and summarizes their clinical value in localizing and lateralizing focal seizures based on consensus in the published literature. Video-EEG examples are included to illustrate important features of semiology in patients with epilepsy.

ILAE definition of the Idiopathic Generalized Epilepsy Syndromes: Position statement by the ILAE Task Force on Nosology and Definitions

In 2017, the International League Against Epilepsy (ILAE) Classification of Epilepsies described the "genetic generalized epilepsies" (GGEs), which contained the "idiopathic generalized epilepsies" (IGEs). The goal of this paper is to delineate the four syndromes comprising the IGEs, namely childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and epilepsy with generalized tonic-clonic seizures alone. We provide updated diagnostic criteria for these IGE syndromes determined by the expert consensus opinion of the ILAE's Task Force on Nosology and Definitions (2017-2021) and international external experts outside our Task Force. We incorporate current knowledge from recent advances in genetic, imaging, and electroencephalographic studies, together with current terminology and classification of seizures and epilepsies. Patients that do not fulfill criteria for one of these syndromes, but that have one, or a combination, of the following generalized seizure types: absence, myoclonic, tonic-clonic and myoclonic-tonic-clonic seizures, with 2.5-5.5 Hz generalized spike-wave should be classified as having GGE. Recognizing these four IGE syndromes as a special grouping among the GGEs is helpful, as they carry prognostic and therapeutic implications.

Genetic generalized epilepsies in adults - challenging assumptions and dogmas

Genetic generalized epilepsy (GGE) syndromes start during childhood or adolescence, and four commonly persist into adulthood, making up 15-20% of all cases of epilepsy in adults. These four GGE syndromes are childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy and epilepsy with generalized tonic-clonic seizures alone. However, in ~20% of patients with GGE, characteristics of more than one syndrome are present. Novel insights into the genetic aetiology, comorbidities and prognosis of the GGE syndromes have emerged and challenge traditional concepts about these conditions. Evidence has shown that the mode of inheritance in GGE is mostly polygenic. Neuropsychological and imaging studies indicate similar abnormalities in unaffected relatives of patients with GGE, supporting the concept that underlying alterations in bilateral frontothalamocortical networks are genetically determined. Contrary to popular belief, first-line anti-seizure medication often fails to provide seizure freedom in combination with good tolerability. Nevertheless, long-term follow-up studies have shown that with advancing age, many patients can discontinue their anti-seizure medication without seizure relapses. Several outcome predictors have been identified, but prognosis across the syndromes is more homogeneous than previously assumed. Overall, overlap in pathophysiology, seizure types, treatment responses and outcomes support the idea that GGEs are not separate nosological entities but represent a neurobiological continuum.

Brainwaves beyond diagnosis: Wider applications of electroencephalography in idiopathic generalized epilepsy

Electroencephalography (EEG) has long been used as a versatile and noninvasive diagnostic tool in epilepsy. With the advent of digital EEG, more advanced applications of EEG have emerged. Compared with technologically advanced practice in focal epilepsies, the utilization of EEG in idiopathic generalized epilepsy (IGE) has been lagging, often restricted to a simple diagnostic tool. In this narrative review, we provide an overview of broader applications of EEG beyond this narrow scope, discussing how the current clinical and research applications of EEG may potentially be extended to IGE. The current literature, although limited, suggests that EEG can be used in syndromic classification, guiding antiseizure medication therapy, predicting prognosis, unraveling biorhythms, and investigating functional brain connectivity of IGE. We emphasize the need for longer recordings, particularly 24-h ambulatory EEG, to capture discharges reflecting circadian and sleep-wake cycle-associated variations for wider EEG applications in IGE. Finally, we highlight the challenges and limitations of the current body of literature and suggest future directions to encourage and enhance more extensive applications of this potent tool.

Cerebellar contribution to absence epilepsy

The new aggregate data analyses revealed the earlier missing role of cerebellum long-term electrical stimulation in the absence epilepsy. Neurophysiologic data gained by authors favor that cerebellar serial deep brain stimulation (DBS) (100 Hz) causes the transformation of penicillin-induced cortical focal discharges into prolonged 3,5-3,75 sec oscillations resembling spike-wave discharges (SWD) in cats. Such SWDs were not organized in the form of bursts and persisted continuously after stimulation. Therefore, the appearance of prolonged periods of SWD is regarded as a tonic cerebellar influence upon pacemaker of SWD and might be caused by the long-lasting DBS-induced increase of GABA-ergic extrasynaptic inhibition in the forebrain networks. The absence seizure facilitation caused by cerebellar DBS was discussed with the reviewed data on optogenetic stimulation, neuronal activity of cerebellar structures, and imaging data.

When should we obtain a routine EEG while managing people with epilepsy?

More than eight decades after its discovery, routine electroencephalogram (EEG) remains a safe, noninvasive, inexpensive, bedside test of neurological function. Knowing when a routine EEG should be obtained while managing people with epilepsy is a critical aspect of optimal care. Despite advances in neuroimaging techniques that aid diagnosis of structural lesions in the central nervous system, EEG continues to provide critical diagnostic evidence with implications on treatment. A routine EEG performed after a first unprovoked seizure can support a clinical diagnosis of epilepsy and differentiate those without epilepsy, classify an epilepsy syndrome to impart prognosis, and characterize seizures for antiseizure management. Despite a current viral pandemic, EEG services continue, and the value of routine EEG is unchanged.

Polyspike ictal-onset absence seizures in a pediatric patient with Down syndrome

Polyspike ictal-onset absence seizure has been reported in adult patients with genetic generalized epilepsy but is a novel pattern in the pediatric population. Absence seizures are usually associated with generalized spike-and-wave on EEG. However, we present the case of a 10-year-old girl with Down syndrome and developmental delays who presented with atypical absence seizure associated with an unusual electroencephalographic (EEG) pattern of polyspike ictal-onset. Recognition of this ictal pattern in the pediatric population, as previously reported in adult populations, is important as it can have therapeutic and prognostic implications.

•

Absence seizures are usually associated with generalized spike and wave, but here we report a polyspike ictal-onset pattern.

•

The pattern appeared as purely a polyspike ictal-onset, or polyspikes intermixed or preceding the generalized spike and wave.

•

Polyspike ictal onset is differentiated from generalized paroxysmal fast activity (GPFA), by morphology & other features.

Hyperventilation-induced high-amplitude rhythmic slowing: A mimicker of absence seizures in children

PURPOSE

Hyperventilation (HV) in children can lead to HV-induced high-amplitude rhythmic slowing (HIHARS) on the EEG (electroencephalogram) which is sometimes associated with altered awareness (AA) and concomitant semiological features. Our aims were to determine the frequency of HIHARS in children, to assess if the associated semiological features were temporally related to HV, and to evaluate if specific semiological features can differentiate HIHARS with AA from absence seizures.

METHODS

Consecutive children with suspected new onset seizure(s) underwent HV and awareness testing during video-EEG acquisition. Hyperventilation-induced high-amplitude rhythmic slowing was defined as 2.5- to 5-Hz generalized rhythmic slowing with amplitude ≥100 μv lasting for ≥3 s. The associated semiological features were compared between the group of children with HIHARS and AA, an age- and gender-matched control group without HIHARS, and in children who experienced absence seizures during HV.

RESULTS

One hundred sixteen children with a mean age of 9.8 years were included. Hyperventilation-induced high-amplitude rhythmic slowing occurred in 39 children (33.6%) with AA documented in 30 (76.9%). The probability of developing AA during HIHARS was significantly and positively correlated with the HIHARS duration. The frequencies of HIHARS were not significantly different between children diagnosed with seizure(s) and those with nonepileptic spells. Hyperventilation cessation and staring did not occur in any child of the control group. Fidgeting and yawning were significantly more common in the group with HIHARS with AA while staring and blinking were significantly more frequent in the group of children with absence seizures.

CONCLUSIONS

We ascertained that HIHARS with AA is a relatively common occurrence in children and most likely represents an age-related nonepileptic phenomenon. When associated with fidgeting or yawning, it can help differentiate this phenomenon from absence seizures. However, recording the concomitant presence of generalized spike wave discharges on the EEG remains essential to confirm the diagnosis of absence seizures.

Driving status of patients with generalized spike-wave on EEG but no clinical seizures

Generalized spike-wave discharges (SWDs) are the hallmark of generalized epilepsy on the electroencephalogram (EEG). In clinically obvious cases, generalized SWDs produce myoclonic, atonic/tonic, or absence seizures with brief episodes of staring and behavioral unresponsiveness. However, some generalized SWDs have no obvious behavioral effects. A serious challenge arises when patients with no clinical seizures request driving privileges and licensure, yet their EEG shows generalized SWD. Specialized behavioral testing has demonstrated prolonged reaction times or missed responses during SWD, which may present a driving hazard even when patients or family members do not notice any deficits. On the other hand, some SWDs are truly asymptomatic in which case driving privileges should not be restricted. Clinicians often decide on driving privileges based on SWD duration or other EEG features. However, there are currently no empirically-validated guidelines for distinguishing generalized SWDs that are "safe" versus "unsafe" for driving. Here, we review the clinical presentation of generalized SWD and recent work investigating mechanisms of behavioral impairment during SWD with implications for driving safety. As a future approach, computational analysis of large sets of EEG data during simulated driving utilizing machine learning could lead to powerful methods to classify generalized SWD as safe vs. unsafe. This may ultimately provide more objective EEG criteria to guide decisions on driving safety in people with epilepsy.

A Practical Guide to Treatment of Childhood Absence Epilepsy

Childhood absence epilepsy (CAE) is a common pediatric epilepsy syndrome with distinct seizure semiology, electroencephalography (EEG) features, and treatment. A diagnosis of CAE can be obtained during an office visit with a careful history, physical exam including prolonged hyperventilation, and a routine EEG. The treatment of choice for CAE with absence seizures only is ethosuximide. Valproic acid and lamotrigine are also effective treatments for many patients, but when compared to ethosuximide, valproic acid has more adverse effects and lamotrigine is less effective. Attention to predictors of response to treatment, including clinical, electrographic, and genetic factors, is increasing. Refractory CAE occurs in fewer than half of patients, and treatment strategies are available, though efficacy data are lacking. Careful assessment and treatment of psychosocial comorbidities is essential in caring for patients with CAE.

Can EEG Differentiate Among Syndromes in Genetic Generalized Epilepsy?

PURPOSE

To evaluate EEG differences among syndromes in genetic generalized epilepsy based on quantified data.

METHODS

Twenty-four-hour ambulatory EEGs were recorded in consecutive patients diagnosed with genetic generalized epilepsy. All epileptiform EEG abnormalities were quantified into density scores (total duration of epileptiform discharges per hour). One-way analysis of variance was conducted to find out differences in EEG density scores among the syndromes. Generalized linear mixed models were also fitted to explore the association between the proportion of "pure" generalized spike-wave paroxysms and fragments (without intervening polyspikes/polyspike-waves) and the syndromes.

RESULTS

In total, 6,923 epileptiform discharges were analyzed from 105 abnormal EEGs. In the analysis of variance, six EEG variables were significantly different among syndromes: total spike density (P = 0.001), total polyspike and polyspike-wave density (P = 0.049), generalized spike-wave-only density (P < 0.001), generalized paroxysm density (P < 0.001), generalized paroxysm duration mean (P = 0.018), and generalized paroxysm duration maximum (P = 0.009). The density of epileptiform discharges and the paroxysm durations were the highest in juvenile absence epilepsy followed by juvenile myoclonic epilepsy, childhood absence epilepsy, and generalized epilepsy with tonic-clonic seizures only. Generalized linear mixed models revealed that "pure" generalized spike-wave discharges (without intervening polyspikes/polyspike waves) tended to be more frequent in absence epilepsies, although the difference was not statistically significant (P = 0.21).

CONCLUSIONS

The findings of this study suggest that the density and duration of epileptiform discharges can help differentiate among genetic generalized epilepsy syndromes.

Absence epilepsy beyond adolescence: an outcome analysis after 45 years of follow-up

OBJECTIVES

Depending on patient age at onset, absence epilepsy is subdivided into childhood and juvenile forms. Absence seizures can occur several times per day (pyknoleptic course) or less frequently than daily (non-pyknoleptic course). Seizures typically terminate before adulthood, but a quarter of patients need ongoing treatment beyond adolescence. Little is known about their long-term seizure and psychosocial outcome.

METHODS

Files of 135 outpatients with absence epilepsy (76 females; 123 had additional generalised tonic-clonic seizures) were retrospectively analysed after a median follow-up of 45.4 years (IQR: 31.9-56.2). Eighty-two subjects completed an additional interview. Patients were dichotomised according to age at epilepsy onset (childhood: n=82; juvenile: n=53) and course of absence seizures (pyknoleptic: n=80; non-pyknoleptic: n=55).

RESULTS

Among all patients, 53% achieved 5-year terminal seizure remission, 16% without antiepileptic medication. Median age at last seizure was lower in patients with childhood onset of absence epilepsy (37.7 years) versus juvenile onset (44.4 years; P≤0.01). However, rates and duration of terminal seizure remission were similar. Pyknoleptic versus non-pyknoleptic course of absence seizures made no difference for long-term seizure outcome. Multivariate analysis identified only higher age at investigation to be associated with terminal 5-year seizure remission. Regarding aspects of psychosocial outcome, there were no significant differences between the respective subgroups.

CONCLUSIONS

These data indicate that if absence epilepsy persists beyond adolescence, long-term seizure and psychosocial outcome do not differ between childhood and juvenile onset or between pyknoleptic and non-pyknoleptic course of absence epilepsy. However, higher patient age increases the chance of terminal seizure remission.

Generalized nonmotor (absence) seizures-What do absence, generalized, and nonmotor mean?

OBJECTIVE

Clinical absences are now classified as "generalized nonmotor (absence) seizures" by the International League Against Epilepsy (ILAE). The aim of this paper is to critically review the concept of absences and to put the accompanying focal and motor symptoms into the context of the emerging pathophysiological knowledge.

METHODS

For this narrative review we performed an extensive literature search on the term "absence," and analyzed the plethora of symptoms observed in clinical absences.

RESULTS

Arising from the localization and the involved cortical networks, motor symptoms may include bilateral mild eyelid fluttering and mild myoclonic jerks of extremities. These motor symptoms may also occur unilaterally, analogous to a focal motor seizure with Jacksonian march. Furthermore, electroencephalography (EEG) abnormalities may exhibit initial frontal focal spikes and consistent asymmetries. Electroclinical characteristics support the cortical focus theory of absence seizures. Simultaneous EEG/functional magnetic resonance imaging (fMRI) measurements document cortical deactivation and thalamic activation. Cortical deactivation is related to slow waves and disturbances of consciousness of varying degrees. Motor symptoms correspond to the spike component of the 3/s spike-and-wave-discharges. Thalamic activation can be interpreted as a response to overcome cortical deactivation. Furthermore, arousal reaction during drowsiness or sleep triggers spikes in an abnormally excitable cortex. An initial disturbance in arousal mechanisms ("dyshormia") might be responsible for the start of this abnormal sequence.

SIGNIFICANCE

The classification as "generalized nonfocal and nonmotor (absence) seizure" does not covey the complex semiology of a patient's clinical events.

Absence Seizures as a Feature of Juvenile Myoclonic Epilepsy in Rhodesian Ridgeback Dogs

Myoclonic epilepsy in Rhodesian Ridgeback (RR) dogs is characterized by myoclonic seizures occurring mainly during relaxation periods, a juvenile age of onset and generalized tonic‐clonic seizures in one‐third of patients. An 8‐month‐old female intact RR was presented for myoclonic seizures and staring episodes that both started at 10 weeks of age. Testing for the DIRAS1 variant indicated a homozygous mutant genotype. Unsedated wireless video‐electroencephalography (EEG) identified frequent, bilaterally synchronous, generalized 4 Hz spike‐and‐wave complexes (SWC) during the staring episodes in addition to the characteristic myoclonic seizures with generalized 4–5 Hz SWC or 4–5 Hz slowing. Photic stimulation did not evoke a photoparoxysmal response. Repeat video‐EEG 2 months after initiation of levetiracetam treatment disclosed a >95% decrease in frequency of myoclonic seizures, and absence seizures were no longer evident. Absence seizures represent another seizure type in juvenile myoclonic epilepsy (JME) in RR dogs, which reinforces its parallels to JME in humans.

Electroencephalography in the Diagnosis of Genetic Generalized Epilepsy Syndromes

Genetic generalized epilepsy (GGE) consists of several syndromes diagnosed and classified on the basis of clinical features and electroencephalographic (EEG) abnormalities. The main EEG feature of GGE is bilateral, synchronous, symmetric, and generalized spike-wave complex. Other classic EEG abnormalities are polyspikes, epileptiform K-complexes and sleep spindles, polyspike-wave discharges, occipital intermittent rhythmic delta activity, eye-closure sensitivity, fixation-off sensitivity, and photoparoxysmal response. However, admixed with typical changes, atypical epileptiform discharges are also commonly seen in GGE. There are circadian variations of generalized epileptiform discharges. Sleep, sleep deprivation, hyperventilation, intermittent photic stimulation, eye closure, and fixation-off are often used as activation techniques to increase the diagnostic yield of EEG recordings. Reflex seizure-related EEG abnormalities can be elicited by the use of triggers such as cognitive tasks and pattern stimulation during the EEG recording in selected patients. Distinct electrographic abnormalities to help classification can be identified among different electroclinical syndromes.

Spatiotemporal propagation patterns of generalized ictal spikes in childhood absence epilepsy

OBJECTIVE

This work investigates the spatial distribution in time of generalized ictal spikes in the typical absences of childhood absence epilepsy (CAE).

METHODS

We studied twelve children with CAE, who had more than two typical absences during their routine video-EEG. Seizures were identified, and ictal spikes were marked over the maximum electronegative peak, clustered, waveform-averaged and spatiotemporaly analyzed in 2D electrode space.

RESULTS

Consistency of spatiotemporal patterns of ictal spikes was high between the absences of the same child, but low between children. Three main discharge patterns were identified: of anterio-posterior propagation, of posterio-anterior propagation and confined to the frontal/prefrontal regions. In 4 patients, the propagation patterns transformed during the seizure into either a lateralized diminished or a non-lateralized reverse direction form. Most spikes originated fronto-temporaly, all maximized over the frontal/prefrontal electrodes and mostly decayed prefrontaly. In 4 patients, lateralized propagation patterns were identified.

CONCLUSIONS

Ictal spike propagation patterns suggest that epileptogenic CAE networks are personalized, interconnect distal areas in the brain - not the entire cortex - with a tendency to generate bilateral symmetrical discharges, sometimes unsuccessfully. The transformation of propagation patterns during the seizure indicates the existence of dynamic interplay within epileptogenic networks.

SIGNIFICANCE

Our results support the revised concept of ictogenesis of ILAE definition in genetic (also known as idiopathic) generalized epilepsies. Understanding the focal features in CAE avoids misdiagnosis as focal epilepsy and inappropriate treatment.

Absence seizure susceptibility correlates with pre-ictal β oscillations

Absence seizures are generalized, cortico-thalamo-cortical (CTC) high power electroencephalographic (EEG) or electrocorticographic (ECoG) events that initiate and terminate suddenly. ECoG recordings of absence seizures in animal models of genetic absence epilepsy show a sudden spike-wave-discharge (SWD) onset that rapidly emerges from normal ECoG activity. However, given that absence seizures occur most often during periods of drowsiness or quiet wakefulness, we wondered whether SWD onset correlates with pre-ictal changes in network activity. To address this, we analyzed ECoG recordings of both spontaneous and induced SWDs in rats with genetic absence epilepsy. We discovered that the duration and intensity of spontaneous SWDs positively correlate with pre-ictal 20-40Hz (β) spectral power and negatively correlate with 4-7Hz (Ø) power. In addition, the output of thalamocortical neurons decreases within the same pre-ictal window of time. In separate experiments we found that the propensity for SWD induction was correlated with pre-ictal β power. These results argue that CTC networks undergo a pre-seizure state transition, possibly due to a functional reorganization of cortical microcircuits, which leads to the generation of absence seizures.

Increased inhibitory synaptic activity in the hippocampus (CA1) of genetic absence epilepsy rats: Relevance of kindling resistance

PURPOSE

Genetic absence epilepsy rats from Strasbourg (GAERS), a well-validated genetic rat model for typical absence epilepsy, are known to manifest a resistance to secondary generalization of abnormal focal electrical activity evoked by kindling. The mechanism of this resistance is still unclear. In order to understand the possible mechanism of kindling resistance, we investigated for the first time, the differences of short-term synaptic plasticity by using a paired-pulse paradigm as an indicator of GABAergic activity in CA1 region of hippocampus in GAERS and non-epileptic Wistar rats in-vivo.

METHODS

Rats were subjected to kindling process, basolateral amygdala was stimulated twice a day, with a supra-threshold current, until they displayed limbic or convulsive seizures. One hour after the last kindling stimulation, evoked field potentials from CA1 pyramidal layer of hippocampus were recorded in-vivo under urethane anesthesia.

RESULTS

In response to supra-threshold kindling stimulations GAERS showed a significantly delayed kindling progression and displayed a significant increase in hippocampal excitability at early stages of kindling that is the critical for the development of convulsive seizures. In control rats that were not received kindling stimulation, paired-pulse depression (PPD) was significantly pronounced in GAERS with respect to the Wistar group. During the kindling course, PPD was gradually reduced in the Wistar rats as kindling progression was advanced. However in GAERS, PPD ratios were not significantly changed at early stages of kindling. When GAERS reached convulsive stage, their PPD ratios became similar to that of Wistar rats.

DISCUSSION

The increased inhibition in paired-pulse responses at early stages of kindling in GAERS suggests the role of augmented GABAergic activity as one of the underlying mechanisms of kindling resistance observed in genetic rat models of absence epilepsy.

Paroxysmal eyelid movements in patients with visual‐sensitive reflex seizures

Aim. Paroxysmal eyelid movements (PEM) are non‐epileptic episodes characterized by eyelid closure, upturning of the eyes, and rapid eyelid flutter. The aim of this study was to report clinical and EEG data of patients with PEM and its relationship with visual sensitivity.

Methods. We studied 26 patients with epilepsy (12 males and 14 females; mean age: 14.0±6.9 years) who presented PEM. The epilepsy was idiopathic generalized (eight cases), idiopathic focal (six cases), symptomatic focal (five cases), and reflex epilepsy (seven cases). PEM and blinking were analysed by video‐EEG recordings at rest and during intermittent photic stimulation, pattern stimulation, and TV watching. Blink rate was evaluated during three different conditions: at rest, during a TV‐viewing period, and at the occurrence of PEM. Analysis of variance (ANOVA) was used for statistical comparisons.

Results. Repeated episodes of PEM were recorded in all patients. The frequency of PEM ranged from 8 to 12.5 Hz (average: 9.6±1.5). PEM were accompanied by a significant increase in blinking compared to the rest condition and TV watching (blink rate: 56.5±21.1 vs 25.0±16.2 vs 11.3±11.8, respectively; p<0.0001). Photoparoxysmal EEG responses (measured as sensitivity to photic stimulation) were found in 25 cases, associated with pattern sensitivity in 22; only one patient was sensitive to pattern but not photic stimulation. Visually‐induced seizures were recorded in 20 cases, triggered by both stimuli (photic and pattern stimulation) in 11 patients; seizures were triggered by pattern stimulation (but not photic stimulation) in five, photic stimulation (but not pattern stimulation) in three, and TV watching (but not photic or pattern stimulation) in one. Epileptic eyelid myoclonia was noted in 17 patients.

Conclusion. The coexistence of PEM, photoparoxysmal EEG responses, increased blinking, and epileptic eyelid myoclonia suggests an underlying dysfunction involving cortical‐subcortical neural networks, according to the recent concept of system epilepsies. [Published with video sequences]

Jeavons syndrome – updated review

Introduction. Eyelid myoclonia and absences (ELMA) was first described by Jeavons in 1977 as a separate type of photosensitive epilepsy.

Aim and method. The aim is to consider the updated electro-clinical pathophysiology and to discuss terminology, classification and differential diagnosis. The review includes our own research and relevant papers on the subject of Jeavons syndrome (JS).

Review and differential diagnosis. Definition: Jeavons syndrome is a generalized idiopathic (genetic) epilepsy syndrome (IGE) characterized by eyelid myoclonia, other seizures (absences, myoclonic and or generalized tonic-clonic) and EEG paroxysms induced by voluntary or on command eye closure, in the light and photosensitivity. Demographical data: The prevalence of JS has been reported to vary from 7.3% to 12.9% among idiopathic generalized epilepsies and 2.5% to 2.7% among all patients with epileptic disorders.

Etiology: JS, as is the case for all idiopathic generalized epilepsies, is genetic and the familial preponderance and concordance is high. Pathophysiology: Three factors are important in order for JS to manifest clinically; the genetic predisposition, the voluntary or on command eye closure and the light input. Clinical forms of JS: we have identified four forms of JS; early onset (< 4 years), mild form, classical form and an ELMA-JME form. Diagnosis: the diagnosis of JS is based on the history, clinical observation and provocation and the confirmation with an EEG. Differential diagnosis: is easily made from tics, other idiopathic generalized or focal cryptogenic/symptomatic epilepsies.

Conclusion. JS is characterized by unique electro-clinical features evoked by voluntary or on command eye closure in the light and photosensitivity.

Current advances in childhood absence epilepsy

BACKGROUND

Childhood absence epilepsy is an age-dependent, idiopathic, generalized epilepsy with a characteristic seizure appearance. The disorder is likely to be multifactorial, resulting from interactions between genetic and acquired factors, but the debate is still open. We review recent studies on different aspects of childhood absence epilepsy and also to describe new concepts.

METHODS

Data for this review were identified using Medline and PubMed survey to locate studies dealing with childhood absence epilepsy. Searches included articles published between 1924 and 2013.

RESULTS

The diagnosis comprises predominant and associated seizure types associated with other clinical and electroencephalographic characteristics. Many studies have challenged the prevailing concepts, particularly with respect to the pathophysiological mechanisms underlying the electroencephalographic seizure discharges. Childhood absence epilepsy fits the definition of system epilepsy as a condition resulting from the persisting susceptibility of the thalamocortical system as a whole to generate seizures. This syndrome, if properly defined using strict diagnostic criteria, has a good prognosis. In some cases, it may affect multiple cognitive functions determining risk for academic and functional difficulties; the detection of children at risk allows tailored interventions. Childhood absence epilepsy is usually treated with ethosuximide, valproate, lamotrigine, or levetiracetam, but the most efficacious and tolerable initial empirical treatment has not been well defined.

CONCLUSIONS

We review recent studies and new concepts on the electroclinical features and pathophysiological findings of childhood absence epilepsy in order to highlight areas of consensus as well as areas of uncertainty that indicate directions for future research.

Long-term seizure remission in childhood absence epilepsy: might initial treatment matter?

OBJECTIVE

Examine the possible association between long-term seizure outcome in childhood absence epilepsy (CAE) and the initial treatment choice.

METHODS

Children with CAE were prospectively recruited at initial diagnosis and followed in a community-based cohort study. Children presenting with convulsive seizures, significant imaging abnormalities, or who were followed <5 years were excluded. Early outcomes included success of initial medication, early remission, and pharmacoresistance. The primary long-term outcome was complete remission: ≥5 years both seizure free and medication free. Survival methods were used for analyses.

RESULTS

The first medication was ethosuximde (ESM) in 41 (69%) and valproic acid (VPA) in 18 (31%). Initial success rates were 59% (ESM) and 56% (VPA). Early remission and pharmacoresistance were similar in each group. Apart from atypical electroencephalography (EEG) features (61% [VPA], 17% [ESM]), no clinical features varied substantially between the treatment groups. Complete remission occurred in 31 children (76%) treated with ESM and 7 (39%) who received VPA (p = 0.007). Children with versus without atypical EEG features were less likely to enter complete remission (50% vs. 71%, p = 0.03). In a Cox regression, ESM was associated with a higher rate of complete remission than VPA (hazards ratio [HR] 2.5, 95% confidence interval [CI] 1.1-6.0; p = 0.03). Atypical EEG features did not independently predict outcome (p = 0.15). Five-year and 10-year remission, regardless of continued treatment, occurred more often in children initially treated with ESM versus VPA.

SIGNIFICANCE

These findings are congruent with results of studies in genetic absence models in rats and provide preliminary evidence motivating a hypothesis regarding potential disease-modifying effects of ESM in CAE. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.

Prognostic value of EEG asymmetries for development of drug-resistance in drug-naïve patients with genetic generalized epilepsies

OBJECTIVE

Previous studies based solely on visual EEG analysis reported equivocal results regarding an association of pharmaco-resistance with EEG asymmetries in genetic generalized epilepsies (GGE). We addressed this issue by applying both visual and quantitative methods to the pretreatment EEG of GGE patients.

METHODS

Socio-demographic/disease characteristics and response to treatment/discontinuation trial for these patients were recorded at 6months and at last follow up. The first EEG was retrospectively, blindly, and visually assessed for focal slowing, focal discharges and also quantitatively analyzed for amplitude or latency asymmetries of generalized discharges. Association between these variables and development of drug-resistance was evaluated.

RESULTS

Out of 51 subjects, 40% had some type of EEG asymmetry by visual, 37% by quantitative and 54% by combined analysis. Drug-resistance was identified in 52% of patients after 6months and in 24% at the end of the follow up period (∼4.2years). 27% of patients underwent a discontinuation trial; 43% unsuccessfully. There was no association between baseline EEG asymmetries of any type and refractoriness to medical therapy, regardless of analytical method used.

CONCLUSIONS

In a carefully selected cohort of medication-naïve GGE patients, visual and quantitative asymmetries in the first EEG were not associated with the development of pharmaco-resistance.

SIGNIFICANCE

These findings do not provide support for utilization of EEG asymmetries as a prognostic tool in GGE.

Genetic generalized epilepsies

In the International League Against Epilepsy's most recent revision of classification and terminology, the term idiopathic epilepsy, previously used to describe those epilepsies whose cause was unknown, but presumed genetic, has been removed. It has been replaced by the term genetic epilepsy, only to be used to describe epilepsy in which the etiology has a known or presumed genetic defect in which seizures are the core symptom of the disorder. The purpose of this article was to review the electroclinical spectrum of those epilepsies that would fall under this new designation of genetic epilepsies in the context of specific generalized epilepsy syndromes providing an update in the clinical, electroencephalographic, and genetic findings in these syndromes.

Phase space approach for modeling of epileptic dynamics

Epileptic electroencephalography recordings can be described in terms of four prototypic wave forms: fast sinusoidal oscillations, large slow waves, fast spiking, and spike waves. On the macroscopic level, these wave forms have been modeled by different mechanistic models which share canonical features. Here we derive a minimal model of excitatory and inhibitory processes with features common to all previous models. We can infer that at least three interacting processes are required to support the prototypic epileptic dynamics. Based on a separation of time scales we analyze the model in terms of interacting manifolds in phase space. This allows qualitative reverse engineering of all epileptic wave forms and transitions between them. We propose this method as a complement to traditional approaches to modeling epileptiform rhythms.

Focal and generalized EEG paroxysms in childhood absence epilepsy: topographic associations and distinctive behaviors during the first cycle of non-REM sleep

PURPOSE

  To better understand the nature of the focal spike-wave discharges (FSWDs) and focally led generalized spike-wave discharges (GSWDs) in typical childhood absence epilepsy (CAE) and by implication their nosologic and taxonomic significance.

METHODS

  Twenty-four abnormal video-electroencephalography (EEG) studies from 13 consecutive children with CAE and good response to appropriate antiepileptic drugs (AEDs) were analyzed. We studied the association between the topography of absence onset and the ictal automatisms, and the topographic correlation between FSWDs and GSWDs and their respective behavior during hyperventilation and the different states of phasic and nonphasic non-rapid eye movement (NREM) sleep. GSWDs were considered as of "focal" onset if a lead-in could be visibly recognized at a paper speed of 60 mm/s, and were classified by their topography.

KEY FINDINGS

  (1) Multifocal absences occurred in 10 children; anterior onset was noted in 81 absences (73.6%) from 12 children and posterior in 18 (16.4%) from 7 children; there was no association between topography of absence onset and ictal automatisms; (2) FSWDs occurred in 85% of children and were multifocal in 73% of them; 85% of FSWDs were anterior and 14% posterior; (3) there was good topographic association between FSWDs and the leading spike of GSWDs of "focal" onset in all children with FSWDs; (4) both FSWDs and GSWDs increased during hyperventilation; (5) FSWDs occurred mainly during noncyclical NREM sleep and during periods of reduced vigilance of cyclical NREM sleep, whereas GSWDs occurred during the periods of enhanced vigilance of NREM sleep; GSWDs occurred significantly more frequently than FSWDs at the transition from reduced to enhanced vigilance of NREM sleep.

SIGNIFICANCE

  Our findings suggest that in CAE focal EEG paroxysms reflect a system of multifocal nonlocalizing electrically unstable cortical areas that under the facilitatory influence of exogenous or endogenous factors like sleep instability can foster a corticothalamic response of sufficient strength to generate 3-Hz GSWDs that are conditionally sustainable and potentially ictal. FSWDs can be viewed as incomplete forms of the GSWDs; together they define the EEG identity of idiopathic "generalized" epileptogenesis.

Vision-based absence seizure detection

In order to diagnose epilepsy, neurologists rely on their experience, performing an equal assessment of the electroencephalogram and the clinical image. Since misdiagnosis reaches a rate of 30% and more than one-third of all epilepsies are poorly understood, a need for leveraging diagnostic precision is obvious. With the aim at enhancing the clinical image assessment procedure, this paper evaluates the suitability of certain facial expression features for detecting and quantifying absence seizures. These features are extracted by means of time-varying signal analysis from signals that are gained by applying computer vision techniques, such as face detection, dense optical flow computation and averaging background subtraction. For the evaluation, video sequences of four patients with absence seizures are used. The classification performance of a C4.5 decision tree shows accuracies of up to 99.96% with a worst percentage of incorrectly classified instances of 0.14%.

The electroencephalogram of idiopathic generalized epilepsy

Idiopathic generalized epilepsy (IGE) is classified into several subsyndromes based on clinical and electroencephalography (EEG) features. The EEG signature of IGE is bisynchronous, symmetric, and generalized spike-wave complex; although focal, irregular, and so called "fragments" of discharges are not uncommon. Other characteristic EEG features include polyspikes, polyspike-wave discharges, occipital intermittent rhythmic delta activity, and photoparoxysmal response. Both human and animal data suggest involvement of the thalamus and the cortex in the generation of spike-wave discharges in IGE. Circadian variations of generalized epileptiform discharges are well described, and these can be useful in diagnostic confirmation. Those discharges tend to occur more often after awakening and during cyclic alternating pattern phase-A of non-rapid eye movement sleep. Activation procedures such as hyperventilation, intermittent photic stimulation, eye closure, and fixation-off are useful techniques to increase the yield of both interictal and ictal EEG abnormalities. Although not in routine use, specific triggers such as pattern stimulation and cognitive tasks may also be of value in eliciting rare reflex seizure-related EEG abnormalities. Variations of EEG abnormalities are evident between different electroclinical syndromes. EEG is also affected by certain external as well as internal factors, which should be borne in mind when interpreting EEG studies in IGE.

Epilepsy and the consciousness system: transient vegetative state?

Recent advances have shown much in common between epilepsy and other disorders of consciousness. Behavior in epileptic seizures often resembles a transient vegetative or minimally conscious state. These disorders all converge on the "consciousness system" -the bilateral medial and lateral fronto-parietal association cortex and subcortical arousal systems. Epileptic unconsciousness has enormous clinical significance leading to accidental injuries, decreased work and school productivity, and social stigmatization. Ongoing research to better understand the mechanisms of impaired consciousness in epilepsy, including neuroimaging studies and fundamental animal models, will hopefully soon enable treatment trails to reduce epileptic unconsciousness and improve patient quality of life.