Electroencephalography in the Diagnosis of Genetic Generalized Epilepsy Syndromes

Neuronal rhythmicity and cortical arousal in a mouse model of absence epilepsy

OBJECTIVES

Absence seizures impair psychosocial function, yet their detailed neuronal basis remains unknown. Recent work in a rat model suggests that cortical arousal state changes prior to seizures and that single neurons show diverse firing patterns during seizures. Our aim was to extend these investigations to a mouse model with studies of neuronal activity and arousal state to facilitate future fundamental investigations of absence epilepsy.

METHODS

We performed in vivo extracellular single unit recordings on awake head-fixed C3H/HeJ mice. Mice were implanted with tripolar electrodes for cortical electroencephalography (EEG). Extracellular single unit recordings were obtained with glass micropipettes in the somatosensory barrel cortex, while animals ambulated freely on a running wheel. Signals were digitized and analyzed during seizures and at baseline.

RESULTS

Neuronal activity was recorded from 36 cortical neurons in 19 mice while EEG showed characteristic 7-8 Hz spike-wave discharges. Different single neurons showed distinct firing patterns during seizures, but the overall mean population neuronal firing rate during seizures was no different from pre-seizure baseline. However, the rhythmicity of neuronal firing during seizures was significantly increased (p < 0.001). In addition, beginning 10s prior to seizure initiation, we observed a progressive decrease in cortical high frequency (>40 Hz) EEG and an increase in lower frequency (1-39 Hz) activity suggesting decreased arousal state.

SIGNIFICANCE

We found that the awake head-fixed C3H/HeJ mouse model demonstrated rhythmic neuronal firing during seizures, and a decreased cortical arousal state prior to seizure onset. Unlike the rat model we did not observe an overall decrease in neuronal firing during seizures. Similarities and differences across species strengthen the ability to investigate fundamental key mechanisms. Future work in the mouse model will identify the molecular basis of neurons with different firing patterns, their role in seizure initiation and behavioral deficits, with ultimate translation to human absence epilepsy.

Developmental Cajal-Retzius cell death contributes to the maturation of layer 1 cortical inhibition and somatosensory processing

The role of developmental cell death in the formation of brain circuits is not well understood. Cajal-Retzius cells constitute a major transient neuronal population in the mammalian neocortex, which largely disappears at the time of postnatal somatosensory maturation. In this study, we used mouse genetics, anatomical, functional, and behavioral approaches to explore the impact of the early postnatal death of Cajal-Retzius cells in the maturation of the cortical circuit. We find that before their death, Cajal-Retzius cells mainly receive inputs from layer 1 neurons, which can only develop their mature connectivity onto layer 2/3 pyramidal cells after Cajal-Retzius cells disappear. This developmental connectivity progression from layer 1 GABAergic to layer 2/3 pyramidal cells regulates sensory-driven inhibition within, and more so, across cortical columns. Here we show that Cajal-Retzius cell death prevention leads to layer 2/3 hyper-excitability, delayed learning and reduced performance in a multi-whisker-dependent texture discrimination task.

Does Hyperventilation Increase the Diagnostic Yield of the Routine Electroencephalogram: A Retrospective Analysis of Adult and Pediatric Cohorts

PURPOSE

While hyperventilation (HV) increases the diagnostic yield of EEG in children, there is conflicting evidence to support its application in adults. For the first time in history, a large cohort of patients has undergone EEGs without HV during the COVID-19 pandemic. Utilizing this opportunity, we sought to investigate whether HV increases the diagnostic yield of EEG in children compared with adults.

METHODS

Patients aged six years and above who had routine EEGs at Monash Health between January 2019 and December 2020 were studied. The cohort was divided into two, pediatric (younger than 18 years) and adult (18 years or older). Epileptiform abnormalities (ictal and interictal) were the outcomes investigated. The effect of HV was examined with logistic regression to determine odds ratios with 95% confidence intervals.

RESULTS

In total, we studied 3,273 patients (pediatric = 830, adult = 2,443). In the pediatric cohort, HV significantly increased the diagnostic yield of absence seizures (p = 0.01, odds ratios 2.44, 95% confidence intervals 1.21-4.93). In adults, HV did not increase the yield of absence seizures (p = 0.34, odds ratios 0.36, 95% confidence intervals 0.05-2.88). Interictal epileptiform discharges during HV were significantly more frequent in children compared with adults (p < 0.001, odds ratios 3.81, 95% confidence intervals 2.51-5.77).

CONCLUSIONS

Hyperventilation is useful to increase the yield of interictal epileptiform discharges and absence seizures in pediatric patients but not in adults. Hence, routine EEG may be recorded in adults without HV when it is unsafe to perform.

The Pre-Interictal Network State in Idiopathic Generalized Epilepsies

Generalized spike wave discharges (GSWDs) are the typical electroencephalographic findings of Idiopathic Generalized Epilepsies (IGEs). These discharges are either interictal or ictal and recent evidence suggests differences in their pathogenesis. The aim of this study is to investigate, through functional connectivity analysis, the pre-interictal network state in IGEs, which precedes the formation of the interictal GSWDs. A high-density electroencephalogram (HD-EEG) was recorded in twenty-one patients with IGEs, and cortical connectivity was analyzed based on lagged coherence and individual anatomy. Graph theory analysis was used to estimate network features, assessed using the characteristic path length and clustering coefficient. The functional connectivity analysis identified two distinct networks during the pre-interictal state. These networks exhibited reversed connectivity attributes, reflecting synchronized activity at 3-4 Hz (delta2), and desynchronized activity at 8-10.5 Hz (alpha1). The delta2 network exhibited a statistically significant (p < 0.001) decrease in characteristic path length and an increase in the mean clustering coefficient. In contrast, the alpha1 network showed opposite trends in these features. The nodes influencing this state were primarily localized in the default mode network (DMN), dorsal attention network (DAN), visual network (VIS), and thalami. In conclusion, the coupling of two networks defined the pre-interictal state in IGEs. This state might be considered as a favorable condition for the generation of interictal GSWDs.

Hyperventilation and Seizures: Not a New Sense: A Literature Review

Hyperventilation and seizures have a long association in the clinical literature and were known to have a relationship long before the electroencephalogram (EEG) was used to record changes in brain activity. As the use of EEG recording progressed, hyperventilation was the first activation method used to assist with diagnosis of epilepsy. Along with slowing of brain activity, hyperventilation can activate epileptiform spiking activity in patients with epilepsy. Currently, hyperventilation is used in standard practice to assist with the diagnosis of epilepsy during EEG recording. Hyperventilation activates epileptiform spiking activity more often than seizures but can trigger clinical seizures in up to 50% of patients with generalized epilepsy. It is more likely to trigger events in children with absence seizures than adults, and it acts as a trigger in patients with focal epilepsy far less often. However, while some clinicians suggest that its diagnostic value is limited, especially in adults with focal epilepsies, others suggest that it is simple, safe, and an important diagnostic tool, even in these patients. This review presents the history of hyperventilation and seizures, its use in the clinical practice, and possible mechanisms involved.

Spike and wave discharges detection in genetic absence epilepsy rat from Strasbourg and patients with genetic generalized epilepsy

OBJECTIVE

Generalised spike and wave discharges (SWDs) are pathognomonic EEG signatures for diagnosing absence seizures in patients with Genetic Generalized Epilepsy (GGE). The Genetic Absence Epilepsy Rats from Strasbourg (GAERS) is one of the best-validated animal models of GGE with absence seizures.

METHODS

We developed an SWDs detector for both GAERS rodents and GGE patients with absence seizures using a neural network method. We included 192 24-hour EEG sessions recorded from 18 GAERS rats, and 24-hour scalp-EEG data collected from 11 GGE patients.

RESULTS

The SWDs detection performance on GAERS showed a sensitivity of 98.01% and a false positive (FP) rate of 0.96/hour. The performance on GGE patients showed 100% sensitivity in five patients, while the remaining patients obtained over 98.9% sensitivity. Moderate FP rates were seen in our patients with 2.21/hour average FP. The detector trained within our patient cohort was validated in an independent dataset, TUH EEG Seizure Corpus (TUSZ), that showed 100% sensitivity in 11 of 12 patients and 0.56/hour averaged FP.

CONCLUSIONS

We developed a robust SWDs detector that showed high sensitivity and specificity for both GAERS rats and GGE patients.

SIGNIFICANCE

This detector can assist researchers and neurologists with the time-efficient and accurate quantification of SWDs.

A cross-sectional investigation of cognition and epileptiform discharges in juvenile absence epilepsy

OBJECTIVES

Despite the prevalence of cognitive symptoms in the idiopathic generalized epilepsies (IGEs), cognitive dysfunction in juvenile absence epilepsy (JAE), a common yet understudied IGE subtype, remains poorly understood. This descriptive study provides a novel, comprehensive characterization of cognitive functioning in a JAE sample and examines the relationship between cognition and 24-h epileptiform discharge load.

METHOD

Forty-four individuals diagnosed with JAE underwent cognitive assessment using Woodcock Johnson III Test of Cognitive Abilities with concurrent 24-h ambulatory EEG monitoring. Generalized epileptiform discharges of any length, and prolonged generalized discharges ≥3 s were quantified across wakefulness and sleep. The relationship between standardized cognitive scores and epileptiform discharges was assessed through regression models.

RESULTS

Cognitive performances in overall intellectual ability, acquired comprehension-knowledge, processing speed, long-term memory storage and retrieval, and executive processes were 0.63-1.07 standard deviation (SD) units lower in the JAE group compared to the population reference mean, adjusted for educational attainment. Prolonged discharges (≥3 s) were recorded in 20 patients (47.6%) from 42 available electroencephalography (EEG) studies and were largely unreported. Duration and number of prolonged discharges were associated with reduced processing speed and long-term memory storage and retrieval.

SIGNIFICANCE

Cognitive dysfunction is seen in patients with JAE across various cognitive abilities, including those representing more stable processes like general intellect. During 24-h EEG, prolonged epileptiform discharges are common yet underreported in JAE despite treatment, and they show moderate effects on cognitive abilities. If epileptiform burden is a modifiable predictor of cognitive dysfunction, therapeutic interventions should consider quantitative 24-h EEG with routine neuropsychological screening. The growing recognition of the spectrum of neuropsychological comorbidities of IGE highlights the value of multidisciplinary approaches to explore the causes and consequences of cognitive deficits in epilepsy.

EEG Markers of Treatment Resistance in Idiopathic Generalized Epilepsy: From Standard EEG Findings to Advanced Signal Analysis

Idiopathic generalized epilepsy (IGE) represents a common form of epilepsy in both adult and pediatric epilepsy units. Although IGE has been long considered a relatively benign epilepsy syndrome, a remarkable proportion of patients could be refractory to treatment. While some clinical prognostic factors have been largely validated among IGE patients, the impact of routine electroencephalography (EEG) findings in predicting drug resistance is still controversial and a growing number of authors highlighted the potential importance of capturing the sleep state in this setting. In addition, the development of advanced computational techniques to analyze EEG data has opened new opportunities in the identification of reliable and reproducible biomarkers of drug resistance in IGE patients. In this manuscript, we summarize the EEG findings associated with treatment resistance in IGE by reviewing the results of studies considering standard EEGs, 24-h EEG recordings, and resting-state protocols. We discuss the role of 24-h EEG recordings in assessing seizure recurrence in light of the potential prognostic relevance of generalized fast discharges occurring during sleep. In addition, we highlight new and promising biomarkers as identified by advanced EEG analysis, including hypothesis-driven functional connectivity measures of background activity and data-driven quantitative findings revealed by machine learning approaches. Finally, we thoroughly discuss the methodological limitations observed in existing studies and briefly outline future directions to identify reliable and replicable EEG biomarkers in IGE patients.

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.

Home-cage behavior in the Stargazer mutant mouse

In many childhood-onset genetic epilepsies, seizures are accompanied by neurobehavioral impairments and motor disability. In the Stargazer mutant mouse, genetic disruptions of Cacng2 result in absence-like spike-wave seizures, cerebellar gait ataxia and vestibular dysfunction, which limit traditional approaches to behavioral phenotyping. Here, we combine videotracking and instrumented home-cage monitoring to resolve the neurobehavioral facets of the murine Stargazer syndrome. We find that despite their gait ataxia, stargazer mutants display horizontal hyperactivity and variable rates of repetitive circling behavior. While feeding rhythms, circadian or ultradian oscillations in activity are unchanged, mutants exhibit fragmented bouts of behaviorally defined "sleep", atypical licking dynamics and lowered sucrose preference. Mutants also display an attenuated response to visual and auditory home-cage perturbations, together with profound reductions in voluntary wheel-running. Our results reveal that the seizures and ataxia of Stargazer mutants occur in the context of a more pervasive behavioral syndrome with elements of encephalopathy, repetitive behavior and anhedonia. These findings expand our understanding of the function of Cacng2.

Pseudoresistance in idiopathic/genetic generalized epilepsies - Definitions, risk factors, and outcome

OBJECTIVE

The aim of the study was to determine risk factors associated with pseudoresistance in a large, representative cohort of patients with Idiopathic/Genetic Generalized Epilepsy (IGE) and the impact of pseudoresistance on socioeconomic parameters.

METHODS

We performed a literature review on definitions of pseudoresistance in IGE. In an established cohort of patients with IGE from Funen, patients with current or previous pseudoresistant seizures were retrospectively identified based on a comprehensive evaluation of the patients' medical records and direct patient contact, if required. In addition, clinical characteristics, socioeconomic, and demographic data were assessed. Personal interviews were used to determine the brief version of Barratts (BIS-8) impulsivity score.

RESULTS

The literature review provided the following definition of pseudoresistance: Seizures due to (I) lacking adherence to antiseizure medication (ASM), (II) incompliance to general rule of conduct, (III) psychogenic nonepileptic seizures (PNES), (IV) inadequate choice of ASM/dosage, and (V) incorrect classification of epilepsy. Applying criteria I-III to a cohort of patients with IGE (n = 499), 73 patients (14.6%) were currently pseudoresistant and 62 (12.4%) were previously pseudoresistant, but currently seizure free. Current pseudoresistance was associated with younger age, drug/alcohol abuse, lower rate of full-time employment, and higher BIS-8 scores. We found no associations of pseudoresistance with juvenile myoclonic epilepsy, psychiatric disease, specific seizure types, or number of seizure types. Patients with previously pseudoresistant seizures have tried more ASMs and were characterized by male preponderance, higher BIS-8, and higher rates of abuse. Surrogate markers for social outcome did not differ.

SIGNIFICANCE

In IGE, pseudoresistance may be defined as PNES or insufficient adherence to medication/conduct and is associated with younger age, drug/alcohol abuse, and higher scores for impulsivity. If transient, its impact on socioeconomic status remains limited but may be associated with a risk of overtreatment with ASM.

Significance of Polyspikes on Electroencephalography in Children with Focal Epilepsy

Purpose: Epilepsy is one of the most common neurological disorders in both adults and children. After detailed history-taking, electroencephalography (EEG) is the most important investigation in the evaluation of epilepsy patients. Polyspikes, defined as a sequence of two or more spikes, are among the findings that can be seen on EEGs of epilepsy patients, but the literature on their significance in focal epilepsy patients is scarce. Therefore, in the current study, we investigated the significance of polyspikes on EEG in childhood focal epilepsy. Methods: A retrospective analysis was conducted of data from children who were diagnosed with focal epilepsy and received anti-seizure medications at Pusan National University Children’s Hospital. Results: Among the 1,125 children included in this study, 468 (41.6%) showed interictal polyspikes on their EEGs. In the multivariate analysis, only the presence of brain magnetic resonance imaging (MRI) abnormalities was significantly associated with the presence of interictal polyspikes on EEGs. Among patients with brain MRI abnormalities, localized polyspikes were significantly associated with focal cortical dysplasia, while multifocal polyspikes were significantly associated with perinatal insults (hypoxic-ischemic encephalopathy and destructive encephalomalacia). Conclusion: Focal epilepsy patients with interictal polyspikes were more likely to have a structural etiology. Furthermore, patients with localized polyspikes were more likely to have focal cortical dysplasia as the structural etiology, while patients with multifocal polyspikes were more likely to have perinatal insults as the structural etiology. This study demonstrates that focal polyspikes can be used as markers of the possible presence of a structural etiology in routine practice.

Hospital-Based Prevalence, Electroencephalogram (EEG), and Neuroimaging Correlation in Seizures Among Children in Odisha, India

Background: Febrile seizures are very common in pediatric practice. We need to differentiate between febrile seizures and other seizures due to central nervous system (CNS) infection by various means of investigation. Though approximately 30% of patients with febrile seizure have later epilepsy and the risk is around 20% even if electroencephalogram (EEG), and neuro-imagings are normal. But data regarding this is laking in developing countries like India.

Aim: The primary objective of this study is to determine the hospital-based prevalence among various types and etiologies of seizures in children admitted to the pediatric department in a teaching hospital of a developing country, India. Besides, the different types of seizures were correlated with the EEG and neuroimaging findings along with the acute onset of seizures among children.

Methods: In this prospective observational study, children from two months to 15 years of age admitted to the Pediatrics Department, KIMS, Bhubaneswar in India between September 2017 and September 2019 were taken. The patients having seizures were included in the study based on the inclusion criteria. Neurological and systemic examinations of the children were recorded and the neuroimaging reports were analyzed.

Results: A total of 19,553 patients aged two months to 15 years were admitted during the study period. Of that, 1,192 cases were diagnosed with febrile and unprovoked seizures. It was observed that the hospital-based prevalence of seizures among children in Odisha was 6%. Besides, it is found that generalized seizure disorder was the most common among the children. It was found that abnormal EEG, magnetic resonance imaging (MRI), and computed tomography (CT) brain in 60% (202/340), 49% (113/230), and 47% (136/288) of cases, respectively. MRI is a better modality of investigation in partial seizure cases 22 (64%) to detect CNS abnormality. Also, MRI of the brain is better in evaluating CNS abnormality in complex febrile cases 4 (31%) than CT brain (0%).

Conclusion: The study concluded that EEG must be the standard modality of test for patients' diagnosis of seizure in children with seizures. CT/MRI scan can give a better supplement to the results but MRI findings are more accurate in cases of complex febrile seizures.

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.

Are medical students adequately prepared to provide quality care for patients with epilepsy? A cross-sectional study of their knowledge and attitude

OBJECTIVE

This study assessed preparedness of Palestinian medical students as future physicians to care for patients with epilepsy through assessing their knowledge and attitude.

METHODS

The current study was conducted in a cross-sectional design. A pre-validated study tool was used to collect sociodemographic and academic details of the students, test their knowledge using a 16-item test, and test their attitude using a 13-item test.

RESULTS

A total of 386 medical students completed the study tool. The median knowledge score was 75.0% (range: 62.5% to 87.5%). The median attitude score was 81.5% (range: 73.8% to 89.2%). Knowledge and attitude scores correlated positively (Spearman's rho = 0.25, p-value < 0.001). Students who were in their clinical training stage (OR = 4.22, 95% CI of 2.54 to 7.01), who had received a course/part of a course on epilepsy (OR = 2.55, 95% CI of 1.26 to 5.17), who perceived their knowledge of epilepsy as moderate (OR = 3.14, 95% CI of 1.87 to 5.28), and those who perceived their knowledge of epilepsy as high (OR = 11.91, 95% CI of 2.47 to 57.41) were more likely to score ≥ 70% in the knowledge test compared to those who were in their basic training stage, who had not received a course/part of a course on epilepsy, and who perceived their knowledge of epilepsy as low, respectively.

CONCLUSION

Findings of the current investigation may indicate that inclusion of courses on epilepsy early in the medical curriculum might promote knowledge of medical students with regard to epilepsy.

You Snooze You Seize: GABAergic Potentiation of Genetic Generalized Seizures During NREM

Impaired State-Dependent Potentiation of GABAergic Synaptic Currents Triggers Seizures in a Genetic Generalized Epilepsy Model Zhang C-Q, Catron MA, Ding L, Hanna CM, Gallagher MJ, Macdonald RL, Zhou C. Cereb Cortex . 2021;31(2):768-784. doi:10.1093/cercor/bhaa256. https://pubmed.ncbi.nlm.nih.gov/32930324/ Epileptic activity in genetic generalized epilepsy (GGE) patients preferentially appears during sleep and its mechanism remains unknown. Here, we found that sleep-like slow-wave oscillations (0.5 Hz SWOs) potentiated excitatory and inhibitory synaptic currents in layer V cortical pyramidal neurons from wild-type (wt) mouse brain slices. In contrast, SWOs potentiated excitatory, but not inhibitory, currents in cortical neurons from a heterozygous (het) knock-in (KI) Gabrg2+Q/390X model of Dravet epilepsy syndrome. This created an imbalance between evoked excitatory and inhibitory currents to effectively prompt neuronal action potential firings. Similarly, physiologically similar up-/down-state induction (present during slow-wave sleep) in cortical neurons also potentiated excitatory synaptic currents within brain slices from wt and het KI mice. Moreover, this state-dependent potentiation of excitatory synaptic currents entailed some signaling pathways of homeostatic synaptic plasticity. Consequently, in het KI mice, in vivo SWO induction (using optogenetic methods) triggered generalized epileptic spike-wave discharges (SWDs), being accompanied by sudden immobility, facial myoclonus, and vibrissa twitching. In contrast, in wt littermates, SWO induction did not cause epileptic SWDs and motor behaviors. To our knowledge, this is the first mechanism to explain why epileptic SWDs preferentially happen during non-rapid eye-movement sleep and quiet-wakefulness in human GGE patients.

Ambulatory EEG Usefulness in Epilepsy Management

SUMMARY

Long-term video-EEG monitoring has been the gold standard for diagnosis of epileptic and nonepileptic events. Medication changes, safety, and a lack of recording EEG in one's habitual environment may interfere with diagnostic representation and subsequently affect management. Some spells defy standard EEG because of ultradian and circadian times of occurrence, manifest nocturnal expression of epileptiform activity, and require classification for clarifying diagnostic input to identify optimal treatment. Some patients may be unaware of seizures, have frequent events, or subclinical seizures that require quantification before optimal management. The influence on antiseizure drug management and clinical drug research can be enlightened by long-term outpatient ambulatory EEG monitoring. With recent governmental shifts to focus on mobile health, ambulatory EEG monitoring has grown beyond diagnostic capabilities to target the dynamic effects of medical and nonmedical treatment for patients with epilepsy in their natural environment. Furthermore, newer applications in ambulatory monitoring include additional physiologic parameters (e.g., sleep, detection of myogenic signals, etc.) and extend treatment relevance to patients beyond seizure reduction alone addressing comorbid conditions. It is with this focus in mind that we direct our discussion on the present and future aspects of using ambulatory EEG monitoring in the treatment of patients with epilepsy.

Long-term Home Video EEG for Recording Clinical Events

SUMMARY

Around 50 years after the first EEG acquisition by Hans Berger, its use in ambulatory setting was demonstrated. Ever since, ambulatory EEG has been widely available and routinely used in the United States (and to a lesser extent in Europe) for diagnosis and management of patients with epilepsy. This technology alone cannot help with semiological characterization, and absence of video is one of its main drawbacks. Addition of video to ambulatory EEG potentially improves diagnostic yield and opens new aspects of utility for better characterization of patient's events, including differential diagnosis, classification, and quantification of seizure burden. Studies evaluating quality of ambulatory video EEG (aVEEG) suggest good quality recordings are feasible. In the utilization of aVEEG, to maximize yield, it is important to consider pretest probability. Having clear pretest questions and a strong index of suspicion for focal, generalized convulsive or non-epileptic seizures further increases the usefulness of aVEEG. In this article, which is part of the topical issue "Ambulatory EEG," the authors compare long-term home aVEEG to inpatient video EEG monitoring, discuss aVEEG's use in diagnosis and follow-up of patients, and present the authors' own experience of the utility of aVEEG in a teaching hospital setting.

Prognostic Value of Generalized Polyspike Trains and Prolonged Epileptiform EEG Runs

INTRODUCTION

A considerable proportion of patients with genetic/idiopathic generalized epilepsy (IGE) suffer from persistent seizures. In this study, it was questioned if generalized polyspike trains (GPT) or prolonged epileptiform EEG runs allow identification of difficult-to-treat patients in a first seizure clinic setting or after recurrent seizures.

METHODS

The first routine outpatient EEGs from untreated patients (later diagnosed with IGE) and routine EEGs from IGE patients with persistent seizures despite medical treatment were analyzed. Seizure outcome and clinical characteristics were retrospectively assessed based on the patients' records.

RESULTS

In routine EEGs recorded after first seizure in untreated patients (n = 79), the prevalence of GPT (n = 1; 1.3%) and prolonged epileptiform EEG runs (n = 13; 16.5%) was low. At follow-up, 24 patients (30.4%) were not seizure free, and 3 (3.8%) of them developed drug-resistant IGE. None of the interictal discharges studied was associated with long-term seizure outcome. Treated IGE patients with recurrent seizures (n = 69) had a similar prevalence of GPT (n = 3; 4.3%) and prolonged epileptiform EEG runs (n = 7; 10.1%). At follow-up, 42 patients (60.8%) suffered persistent seizures, and 18 (26%) were drug resistant. Generalized polyspike train and prolonged epileptiform EEG runs had a higher prevalence in patients with drug-resistant epilepsy (GPT: 11.1% vs. 2%; P = 0.1; prolonged epileptiform EEG runs: 27.8% vs. 3.9%; P = 0.004) and persistent seizures (GPT: 7.1% vs. 0%; P = 0.16; prolonged epileptiform EEG runs: 16.7% vs. 0%; P = 0.03) as compared with nonresistant patients.

CONCLUSIONS

Generalized polyspike train and prolonged epileptiform EEG runs were associated with persistent seizures and drug-resistant IGE, but the overall prevalence was low. In a first seizure clinic setting, the diagnostic value of these biomarkers was limited.

The Role and Controversies of Electroencephalogram in Focal versus Generalized Epilepsy

As early in 1935, Gibbs et al described electroencephalogram (EEG) features of large slow waves seen in “petit mal” seizures and change in background rhythm to a higher frequency, greater amplitude pattern in “grand mal” seizures. Studies have shown many typical EEG features in focal onset as well as generalized epilepsies.2 3 It is usually easy to delineate focal epilepsy cases when EEG onset of seizures is clear as seen in Benign focal epileptiform discharges of childhood.4 However, it is not uncommon to see cases where epileptiform discharges are not very clear. For example, there can be secondary bilateral synchrony or generalized onset of epileptiform discharges in some cases of focal epilepsy5 and nongeneralized EEG features is cases of generalized epilepsy like absence seizures.6

The awareness of occurrence of focal clinical and EEG features in generalized epilepsy is particularly important to help to select appropriate AEDs and also to avoid inappropriate consideration for epilepsy surgery.7 Lüders et al8 have shown that multiple factors like electroclinical seizure evolution, neuroimaging (both functional and anatomical) have to be analyzed in depth before defining an epileptic syndrome. Here, we are providing few examples of different situations where it is still mysterious to figure out focal onset seizures with secondary generalization versus primary generalized epilepsy.

Electrocorticographic description of the effects of anticonvulsant drugs used to treat lidocaine-induced seizures

INTRODUCTION

Local anesthetics are widely used in clinical practice. While toxicity is rare, these drugs can cause potentially lethal seizures.

OBJECTIVE

In the present study, we investigated the electrocorticographic (ECoG) and electromyographic patterns of seizures induced by acute lidocaine (LA) toxicity and treated with anticonvulsant drugs. The study used adult male Wistar rats to describe of the seizure-related behavior of LA and investigated the treatment with anticonvulsant drugs.

RESULTS

The use of LA resulted in clear changes in the ECoG pattern, which presented characteristics of Status epilepticus, with increased intensity in all brainwaves. The decomposition of the cerebral waves showed an increase in the beta and gamma waves that may be related to tonic-clonic seizure. Although the treatment with anticonvulsants drugs reduces the power of brainwaves at frequencies between 1 and 40 Hz compared to the LA group, but only diazepam (DZP) was able to decrease the intensity of oscillations. The muscle contraction power also indicated a difference in the effectiveness of the three treatments.

CONCLUSION

The sum of the evidence indicates that LA causes status epilepticus and that DZP is the most effective treatment for the control of these seizures, by restoring the systemic values to levels close to those recorded in the control group.

Case Report: A Case of Eyelid Myoclonic Status With Tonic-Clonic Seizure and Literature Review

Eyelid myoclonus with or without absence epilepsy is a rare and usually misdiagnosed disease in the neurology department. It is an idiopathic general epileptic syndrome, the onset period is 6-8 years, and is more common in girls. It is characterized by rapid abnormal eye blinking, accompanied by upward rolling of the eye and slight backward movement of the head, with eye closure sensitivity and photosensitivity. The seizure is frequent and short, dozens or even hundreds of times a day; a small number of patients may have eyelid myoclonus status. We report a patient who visits the hospital for the first time with eyelid myoclonic problem; the patient continued to wink the eyes, eye rolled up, and backward movement of the head, accompanied by impairment of consciousness. Video electroencephalography (VEEG) suggests continued spike slow-wave, polyspike slow-wave. After the patient had 2, 4, 6, 8, 10, 12, and 14 Hz of intermittent photic stimulation (IPS), her seizures and epileptic discharges reduced or stopped. Seven min after giving stimulation at 20 Hz, the child developed an occipital-initiated tonic-clonic seizure, which demonstrated that after sufficient IPS stimulation, the occiput cortex became excited and initiated a brain network, leading to diffuse brain discharge and tonic-clonic seizures. At 1 h after onset, the child developed a nonconvulsive state, with impairment of consciousness despite no eyelid myoclonic movements, and VEEG suggested a large number of epileptic discharges. After 10 min of administrating midazolam, the patient's EEG immediately became normal, and the patient regained consciousness. Therefore, this paper presents an eyelid myoclonus status patient with occipital origin seizure, we recorded the whole course of the disease and the treatment effect, and reviewed the literature accordingly.

Investigating how electroencephalogram measures associate with delirium: A systematic review

Delirium is a common neurocognitive disorder in hospital settings, characterised by fluctuating impairments in attention and arousal following an acute precipitant. Electroencephalography (EEG) is a useful method to understand delirium pathophysiology. We performed a systematic review to investigate associations between delirium and EEG measures recorded prior, during, and after delirium. A total of 1,655 articles were identified using PsycINFO, Embase and MEDLINE, 31 of which satisfied inclusion criteria. Methodological quality assessment was undertaken, resulting in a mean quality score of 4 out of a maximum of 5. Qualitative synthesis revealed EEG slowing and reduced functional connectivity discriminated between those with and without delirium (i.e. EEG during delirium); the opposite pattern was apparent in children, with cortical hyperexcitability. EEG appears to have utility in differentiating those with and without delirium, but delirium vulnerability and the long-term effects on brain function require further investigation. Findings provide empirical support for the theory that delirium is a disorder of reduced functional brain integration.

Neural diffusivity and pre-emptive epileptic seizure intervention

The propagation of epileptic seizure activity in the brain is a widespread pathophysiology that, in principle, should yield to intervention techniques guided by mathematical models of neuronal ensemble dynamics. During a seizure, neural activity will deviate from its current dynamical regime to one in which there are significant signal fluctuations. In silico treatments of neural activity are an important tool for the understanding of how the healthy brain can maintain stability, as well as of how pathology can lead to seizures. The hope is that, contained within the mathematical foundations of such treatments, there lie potential strategies for mitigating instabilities, e.g. via external stimulation. Here, we demonstrate that the dynamic causal modelling neuronal state equation generalises to a Fokker-Planck formalism if one extends the framework to model the ways in which activity propagates along the structural connections of neural systems. Using the Jacobian of this generalised state equation, we show that an initially unstable system can be rendered stable via a reduction in diffusivity–i.e., by lowering the rate at which neuronal fluctuations disperse to neighbouring regions. We show, for neural systems prone to epileptic seizures, that such a reduction in diffusivity can be achieved via external stimulation. Specifically, we show that this stimulation should be applied in such a way as to temporarily mirror the activity profile of a pathological region in its functionally connected areas. This counter-intuitive method is intended to be used pre-emptively–i.e., in order to mitigate the effects of the seizure, or ideally even prevent it from occurring in the first place. We offer proof of principle using simulations based on functional neuroimaging data collected from patients with idiopathic generalised epilepsy, in which we successfully suppress pathological activity in a distinct sub-network prior to seizure onset. Our hope is that this technique can form the basis for future real-time monitoring and intervention devices that are capable of treating epilepsy in a non-invasive manner.

Epilepsy is a disease that affects over 50 million people worldwide. Current treatments include dangerous surgical procedures in which brain connections are severed, or even in which entire problem brain regions are removed. Pharmaceutical options are available, but only about one third of patients are responsive. However, even in these cases the drugs can cause such severe side effects that the patients sometimes choose to suffer seizures. We are proposing an innovative treatment of epilepsy that could be achieved by using non-invasive electrical stimulation. Specifically, we show that stimulation should be applied in such a way as to mirror the activity in a problem brain region, by targeting its neighbouring areas. This counterintuitive approach is based on a mathematical model in which this mirroring strategy is applied pre-emptively, i.e. long before the seizure has a chance to set in. The hope is that future clinical trials will be able to use this model to lessen the effect of seizures, or even prevent them from occurring in the first place.

Electrocorticographic patterns dominated by low-frequency waves in camphor-induced seizures

Camphor is an aromatic terpene compound found in the essential oils of many plants, which has been used for centuries as a herbal medicine, especially in children. However, many studies have shown that camphor may have major side effects, including neurological manifestation, such as seizures. In the present study, we investigated the electrocorticographic patterns of seizures induced by camphor in male adult Wistar rats. Each rat received 400 mg/kg (i.p.) of camphor prior to monitoring by electrocorticography. The application of camphor resulted a rapid evolution to seizure and marked changes in the electrocorticographic readings, which presented characteristics of epileptiform activity, with an increase in the total power wave. The decomposition of the cerebral waves revealed an increase in the delta and theta waves. The analysis of the camphor traces revealed severe ictal activity marked by an increase in the polyspike wave. Our data thus indicate that camphor may cause seizures, leading to tonic–clonic seizures. Clearly, further studies are necessary to better elucidate the mechanisms through which camphor acts on the brain, and to propose potential treatments with anticonvulsant drugs that are effective for the control of the seizures.

Interstitial ions: A key regulator of state-dependent neural activity?

Throughout the nervous system, ion gradients drive fundamental processes. Yet, the roles of interstitial ions in brain functioning is largely forgotten. Emerging literature is now revitalizing this area of neuroscience by showing that interstitial cations (K+, Ca2+ and Mg2+) are not static quantities but change dynamically across states such as sleep and locomotion. In turn, these state-dependent changes are capable of sculpting neuronal activity; for example, changing the local interstitial ion composition in the cortex is sufficient for modulating the prevalence of slow-frequency neuronal oscillations, or potentiating the gain of visually evoked responses. Disturbances in interstitial ionic homeostasis may also play a central role in the pathogenesis of central nervous system diseases. For example, impairments in K+ buffering occur in a number of neurodegenerative diseases, and abnormalities in neuronal activity in disease models disappear when interstitial K+ is normalized. Here we provide an overview of the roles of interstitial ions in physiology and pathology. We propose the brain uses interstitial ion signaling as a global mechanism to coordinate its complex activity patterns, and ion homeostasis failure contributes to central nervous system diseases affecting cognitive functions and behavior.

Accurate detection of spontaneous seizures using a generalized linear model with external validation

OBJECTIVE

Seizure detection is a major facet of electroencephalography (EEG) analysis in neurocritical care, epilepsy diagnosis and management, and the instantiation of novel therapies such as closed-loop stimulation or optogenetic control of seizures. It is also of increased importance in high-throughput, robust, and reproducible pre-clinical research. However, seizure detectors are not widely relied upon in either clinical or research settings due to limited validation. In this study, we create a high-performance seizure-detection approach, validated in multiple data sets, with the intention that such a system could be available to users for multiple purposes.

METHODS

We introduce a generalized linear model trained on 141 EEG signal features for classification of seizures in continuous EEG for two data sets. In the first (Focal Epilepsy) data set consisting of 16 rats with focal epilepsy, we collected 1012 spontaneous seizures over 3 months of 24/7 recording. We trained a generalized linear model on the 141 features representing 20 feature classes, including univariate and multivariate, linear and nonlinear, time, and frequency domains. We tested performance on multiple hold-out test data sets. We then used the trained model in a second (Multifocal Epilepsy) data set consisting of 96 rats with 2883 spontaneous multifocal seizures.

RESULTS

From the Focal Epilepsy data set, we built a pooled classifier with an Area Under the Receiver Operating Characteristic (AUROC) of 0.995 and leave-one-out classifiers with an AUROC of 0.962. We validated our method within the independently constructed Multifocal Epilepsy data set, resulting in a pooled AUROC of 0.963. We separately validated a model trained exclusively on the Focal Epilepsy data set and tested on the held-out Multifocal Epilepsy data set with an AUROC of 0.890. Latency to detection was under 5 seconds for over 80% of seizures and under 12 seconds for over 99% of seizures.

SIGNIFICANCE

This method achieves the highest performance published for seizure detection on multiple independent data sets. This method of seizure detection can be applied to automated EEG analysis pipelines as well as closed loop interventional approaches, and can be especially useful in the setting of research using animals in which there is an increased need for standardization and high-throughput analysis of large number of seizures.

Neurophysiological and Genetic Findings in Patients With Juvenile Myoclonic Epilepsy

Objective

Transcranial magnetic stimulation (TMS), a non-invasive procedure, stimulates the cortex evaluating the central motor pathways. The response is called motor evoked potential (MEP). Polyphasia results when the response crosses the baseline more than twice (zero crossing). Recent research shows MEP polyphasia in patients with generalized genetic epilepsy (GGE) and their first-degree relatives compared with controls. Juvenile Myoclonic Epilepsy (JME), a GGE type, is not well studied regarding polyphasia. In our study, we assessed polyphasia appearance probability with TMS in JME patients, their healthy first-degree relatives and controls. Two genetic approaches were applied to uncover genetic association with polyphasia.

Methods

20 JME patients, 23 first-degree relatives and 30 controls underwent TMS, obtaining 10–15 MEPs per participant. We evaluated MEP mean number of phases, proportion of MEP trials displaying polyphasia for each subject and variability between groups. Participants underwent whole exome sequencing (WES) via trio-based analysis and two-case scenario. Extensive bioinformatics analysis was applied.

Results

We identified increased polyphasia in patients (85%) and relatives (70%) compared to controls (47%) and significantly higher mean number of zero crossings (i.e., occurrence of phases) (patients 1.49, relatives 1.46, controls 1.22; p < 0.05). Trio-based analysis revealed a candidate polymorphism, p.Glu270del,in SYT14 (Synaptotagmin 14), in JME patients and their relatives presenting polyphasia. Sanger sequencing analysis in remaining participants showed no significant association. In two-case scenario, a machine learning approach was applied in variants identified from odds ratio analysis and risk prediction scores were obtained for polyphasia. The results revealed 61 variants of which none was associated with polyphasia. Risk prediction scores indeed showed lower probability for non-polyphasic subjects on having polyphasia and higher probability for polyphasic subjects on having polyphasia.

Conclusion

Polyphasia was present in JME patients and relatives in contrast to controls. Although no known clinical symptoms are linked to polyphasia this neurophysiological phenomenon is likely due to common cerebral electrophysiological abnormality. We did not discover direct association between genetic variants obtained and polyphasia. It is likely these genetic traits alone cannot provoke polyphasia, however, this predisposition combined with disturbed brain-electrical activity and tendency to generate seizures may increase the risk of developing polyphasia, mainly in patients and relatives.

The Molecular Genetic Interaction Between Circadian Rhythms and Susceptibility to Seizures and Epilepsy

Seizure patterns observed in patients with epilepsy suggest that circadian rhythms and sleep/wake mechanisms play some role in the disease. This review addresses key topics in the relationship between circadian rhythms and seizures in epilepsy. We present basic information on circadian biology, but focus on research studying the influence of both the time of day and the sleep/wake cycle as independent but related factors on the expression of seizures in epilepsy. We review studies investigating how seizures and epilepsy disrupt expression of core clock genes, and how disruption of clock mechanisms impacts seizures and the development of epilepsy. We focus on the overlap between mechanisms of circadian-associated changes in SCN neuronal excitability and mechanisms of epileptogenesis as a means of identifying key pathways and molecules that could represent new targets or strategies for epilepsy therapy. Finally, we review the concept of chronotherapy and provide a perspective regarding its application to patients with epilepsy based on their individual characteristics (i.e., being a “morning person” or a “night owl”). We conclude that better understanding of the relationship between circadian rhythms, neuronal excitability, and seizures will allow both the identification of new therapeutic targets for treating epilepsy as well as more effective treatment regimens using currently available pharmacological and non-pharmacological strategies.

Rapid eye movement (REM) sleep and seizure control in idiopathic generalized epilepsy

BACKGROUND

Sleep and epilepsy are bedfellows, and they affect each other reciprocally. Despite the well-known relationship between sleep and epilepsy, data about the impact of sleep on seizure control and responsiveness to therapy are scarce.

OBJECTIVE

The aim of this work was to study the impact of sleep architecture in drug-naïve patients with idiopathic generalized epilepsy (IGE) on seizure control and responsiveness to treatment.

METHODS

This is a prospective cohort study conducted on thirty newly diagnosed patients with IGE attending the epilepsy clinic in Alexandria University Hospital in Egypt and thirty healthy controls. All recruited subjects had a baseline overnight polysomnographic study, then patients were given sodium valproate in therapeutic doses and followed up for six months for assessment of seizure control. After follow-up, they were classified into fully controlled and inadequately controlled patients, and a comparison between them was made.

RESULTS

Of the recruited patients, 13 were fully controlled. Rapid eye movement (REM) sleep % was significantly lower among inadequately controlled patients (9.01 ± 6.23) than fully controlled group (19.6 ± 9.01) and controls (18.17 ± 4.85) (p = 0.002), and the REM sleep latency was significantly longer among the inadequately controlled patients (115.7 ± 72.8 min) than fully controlled patients (54.6 ± 77.3 min) and controls (68.75 ± 37.95 min) (p = 011). On univariate regression analysis, the Odd's ratio (OR) for REM sleep percentage was 3.04 (p = 0.001).

CONCLUSION

Rapid eye movement sleep percentage and latency can contribute to seizure control in IGE.

GABAA receptor β3 subunit mutation D120N causes Lennox-Gastaut syndrome in knock-in mice

The Lennox-Gastaut syndrome is a devastating early-onset epileptic encephalopathy, associated with severe behavioural abnormalities. Its pathophysiology, however, is largely unknown. A de novo mutation (c.G358A, p.D120N) in the human GABA type-A receptor β3 subunit gene (GABRB3) has been identified in a patient with Lennox-Gastaut syndrome. To determine whether the mutation causes Lennox-Gastaut syndrome in vivo in mice and to elucidate its mechanistic effects, we generated the heterozygous Gabrb3^+/D120N knock-in mouse and found that it had frequent spontaneous atypical absence seizures, as well as less frequent tonic, myoclonic, atonic and generalized tonic-clonic seizures. Each of these seizure types had a unique and characteristic ictal EEG. In addition, knock-in mice displayed abnormal behaviours seen in patients with Lennox-Gastaut syndrome including impaired learning and memory, hyperactivity, impaired social interactions and increased anxiety. This Gabrb3 mutation did not alter GABA type-A receptor trafficking or expression in knock-in mice. However, cortical neurons in thalamocortical slices from knock-in mice had reduced miniature inhibitory post-synaptic current amplitude and prolonged spontaneous thalamocortical oscillations. Thus, the Gabrb3^+/D120N knock-in mouse recapitulated human Lennox-Gastaut syndrome seizure types and behavioural abnormalities and was caused by impaired inhibitory GABAergic signalling in the thalamocortical loop. In addition, treatment with antiepileptic drugs and cannabinoids ameliorated atypical absence seizures in knock-in mice. This congenic knock-in mouse demonstrates that a single-point mutation in a single gene can cause development of multiple types of seizures and multiple behavioural abnormalities. The knock-in mouse will be useful for further investigation of the mechanisms of Lennox-Gastaut syndrome development and for the development of new antiepileptic drugs and treatments.

Advances in genetic testing and optimization of clinical management in children and adults with epilepsy

Introduction: Epileptic disorders are a heterogeneous group of medical conditions with epilepsy as the common denominator. Genetic causes, electro-clinical features, and management significantly vary according to the specific condition.Areas covered: Relevant diagnostic advances have been achieved thanks to the advent of Next Generation Sequencing (NGS)-based molecular techniques. These revolutionary tools allow to sequence all coding (whole exome sequencing, WES) and non-coding (whole genome sequencing, WGS) regions of human genome, with a potentially huge impact on patient care and scientific research.Expert opinion: The application of these tests in children and adults with epilepsy has led to the identification of new causative genes, widening the knowledge on the pathophysiology of epilepsy and resulting in therapeutic implications. This review will explore the most recent advancements in genetic testing and provide up-to-date approaches for the choice of the correct test in patients with epilepsy.

Low-Power High-Input-Impedance EEG Signal Acquisition SoC With Fully Integrated IA and Signal-Specific ADC for Wearable Applications

This paper presents a low-power high-input-impedance analog-front-end (AFE) design including an instrumentational-amplifier (IA) and a neural-signal-specific ADC (NSS-ADC) for continuous acquisition of electroencephalography (EEG) signals. In the proposed AFE, low-voltage low-power design techniques are used to reduce the power consumption of the whole system. Furthermore, by utilizing the proposed NSS-ADC, high-amplitude EEG spikes, which convey more important information, are converted with higher resolutions, while the background-noise (B-Noise) of the EEG signal is converted with the lowest resolution. Hence, when the NSS-ADC enters the inactive region, the resolution- and DAC- controlling-units (RCU and DCU) set the analog and digital components of the NSS-ADC into off mode, which leads to power reduction. Based on measurement results, the AFE consumes a power of 3.7 μW under the sampling rate of 20 KS/s. In the proposed AFE, to avoid signal attenuation, active-electrodes (AEs) are utilized to enhance the input impedance of the AFE up to 102 GΩ and 5.2 GΩ at 1 Hz and 20 Hz, respectively. In addition, by using circuit-design techniques the input-referred-noise is reduced as low as 1.5 μV_rms over 0.5-1.2 kHz. Finally, by using a transconductance-driven-right-leg (TDRL) and a common-mode-feedback (CMFB) blocks, a common-mode-rejection-ratio (CMRR) of 108 dB is achieved.

Management and attitudes toward patients with epilepsy in general practice: How far have we come in three decades?

BACKGROUND

Previous surveys of Australian primary care physicians' attitudes regarding epilepsy and persons with epilepsy (PWE), conducted 20-30 years ago, identified the need for further education in epilepsy care for frontline clinicians. This follow-up study of general practitioners (GPs) in Sydney was conducted to determine the degree of changes in knowledge, attitudes, and management of PWE, with the purpose of evaluating if there had been significant improvement during this period.

METHODS

A questionnaire, evaluating various aspects of epilepsy care, including investigations, preferred healthcare provider (HCP), and attitudes toward epilepsy was developed, largely based on the previous work, piloted, and completed by a representative sample of Sydney GPs.

RESULTS

A total of 52 completed responses were received. Thirty-six out of 47 GPs (77%) chose neurologists as the most important HCP followed by the GP (9/47; 18.7%). Almost half of the GPs (25/51; 49%) mentioned that they never initiated antiepileptic medication (AEM) therapy by themselves yet half of these GPs would alter the neurologist's regimen, without necessitating referral back to that neurologist. Another 27% (14/51 GPs) rarely commenced AEM therapy. Six out of 50 GPs did not mention an electroencephalogram (EEG) as a routine investigation, and 21/50 did not mention magnetic resonance imaging (MRI) as routine for PWE. The five most commonly used AEMs, identified by at least 10% of respondents, were sodium valproate (42), carbamazepine (37), levetiracetam (31), lamotrigine (16), and phenytoin (15). Emotional, behavioral, and psychosocial issues were perceived to be more common among PWE; however, they could contribute equally well to society as people without epilepsy.

CONCLUSION

The results of the study indicate a perceptual shift regarding GP's attitudes to epilepsy; however, there remain deficiencies in knowledge, particularly with regard to investigations and management. The study highlights the need for more formal training of GPs in caring for PWE.

The effect of antiepileptic drugs on epileptiform discharges in genetic generalized epilepsy: A systematic review

OBJECTIVE

The objective of this study was to evaluate the current evidence regarding the effect of antiepileptic drugs (AEDs) on epileptiform discharge (ED) burden in genetic generalized epilepsy (GGE).

METHODS

We conducted a comprehensive literature search of PubMed, Embase, PsycINFO, and the Web of Science Core Collection databases using the keywords 'genetic generalized epilepsy', 'antiepileptic drugs' and 'epileptiform discharge'. Primary human studies published in English that reported the effect of AEDs on EDs captured on electroencephalogram (EEG) recordings of at least 24 h in duration in patients with GGE were included.

RESULTS

Six studies published between 1984 and 2017, which reported the effect of AEDs on EDs, involving a total of 116 patients with GGE, were analyzed. Our systematic review found a tendency for AEDs to reduce ED density, frequency, cumulative duration, and burst duration in GGE. Furthermore, we found evidence that the AED-mediated reduction in ED burden was associated with improved seizure control and cognitive outcomes.

CONCLUSIONS

Antiepileptic drugs tend to reduce ED burden in GGE, but the significance of this association remains uncertain.

Can absence seizures be predicted by vigilance states?: Advanced analysis of sleep-wake states and spike-wave discharges' occurrence in rats

Spike-wave discharges (SWDs) are the main manifestation of absence epilepsy. Their occurrence is dependent on the behavioral state, and they preferentially occur during unstable vigilance periods. The present study investigated whether the occurrence of SWDs can be predicted by the preceding behavioral state and whether this relationship is different between the light and the dark phases of the 24-h day. Twenty-four-hour (12:12 light/dark phases) electroencephalographic (EEG) recordings of 12 Wistar Albino Glaxo, originally bred in Rijswijk (WAG/Rij) rats, a well-known genetic model of absence epilepsy, were analyzed and transformed into sequences of 2-s length intervals of the following 6 possible states: active wakefulness (AW), passive wakefulness (PW), deep slow-wave sleep (DSWS), light slow-wave sleep (LSWS), rapid eye movement (REM) sleep, and SWDs, given discrete series of categorical data. Probabilities of all transitions between states and Shannon entropy of transitions were calculated for the light and dark phases separately and statistically analyzed. Common differences between the light and the dark phases were found regarding the time spent in AW, LSWS, DSWS, and SWDs. The most probable transitions were that AW was preceded and followed by PW and vice versa regardless of the phase of the photoperiod. A similar relationship was found for light and deep slow-wave sleep. The most probable transitions to and from SWDs were AW and LSWS, respectively, with these transition likelihoods being consistent across both circadian phases. The second most probable transitions around SWDs appeared more variable between light and dark. During the light phase, SWDs occurred around PW and participated exclusively in sleep initiation; in the dark phase, SWDs were seen on both, ascending and descending steps towards and from sleep. Conditional Shannon entropy showed that AW and DSWS are the most predictable events, while the possible prediction horizon of SWDs is not larger than 4 s and despite the higher occurrence of SWDs in the dark phase, did not differ between phases. It can be concluded that although SWDs show a stable, strong circadian rhythm with a peak in number during the dark phase, their occurrence cannot be reliably predicted by the preceding behavioral state, except at a very short time base.

Robust closed-loop control of spike-and-wave discharges in a thalamocortical computational model of absence epilepsy

In this paper, we investigate the abatement of spike-and-wave discharges in a thalamocortical model using a closed-loop brain stimulation method. We first explore the complex states and various transitions in the thalamocortical computational model of absence epilepsy by using bifurcation analysis. We demonstrate that the Hopf and double cycle bifurcations are the key dynamical mechanisms of the experimental observed bidirectional communications during absence seizures through top-down cortical excitation and thalamic feedforward inhibition. Then, we formulate the abatement of epileptic seizures to a closed-loop tracking control problem. Finally, we propose a neural network based sliding mode feedback control system to drive the dynamics of pathological cortical area to track the desired normal background activities. The control system is robust to uncertainties and disturbances, and its stability is guaranteed by Lyapunov stability theorem. Our results suggest that the seizure abatement can be modeled as a tracking control problem and solved by a robust closed-loop control method, which provides a promising brain stimulation strategy.

EEG changes in patients on antipsychotic therapy: A systematic review

OBJECTIVES

The objective of the study was to characterize the electroencephalogram (EEG) changes associated with different antipsychotic medications based on the evidence from the literature.

METHODS

A systematic search of the databases Medline, PsycINFO, and PubMed was conducted. The Preferred Items Reporting for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in the construction of this systematic review. Primary research articles that reported descriptive EEG results, included comparisons of subjects with and without antipsychotic therapy, and excluded patients with epilepsy were included in the analysis. The outcome was the presence of epileptiform discharges or slowing on EEG. We analyzed pooled data, where possible, from studies with a similar intervention and methodology.

RESULTS

Fourteen articles reporting on a total of 665 patients were reviewed. Among the publications, clozapine was the drug most consistently accompanied by EEG slowing and epileptiform discharges, with an odds ratio of 16.9 (95% confidence intervals (CI): 5.4 to 53.2) and 6.2 (95% CI: 3.4 to 11.3), respectively in the analysis of pooled data. Only one study reported a significant increase in epileptiform discharges with phenothiazine antipsychotic therapy as a group, but the impact of individual drugs was not analyzed separately.

CONCLUSIONS

This systematic review suggests that, among antipsychotics, clozapine most frequently induces EEG slowing and epileptiform discharges. There remains limited data with respect to other individual antipsychotic agents and covariates including drug dose, plasma levels, dose adjustments, and treatment duration that influence EEG changes.

Seizure detection devices for use in antiseizure medication clinical trials: A systematic review

OBJECTIVE

This study characterizes the current capabilities of seizure detection device (SDD) technology and evaluates the fitness of these devices for use in anti-seizure medication (ASM) clinical trials.

METHODS

Through a systematic literature review, 36 wireless SDDs featured in published device validation studies were identified. Each device's seizure detection capabilities that addressed ASM clinical trial primary endpoint measurement needs were cataloged.

RESULTS

The two most common types of seizures targeted by ASMs in clinical trials are generalized tonic-clonic (GTC) seizures and focal with impaired awareness (FIA) seizures. The Brain Sentinel SPEAC achieved the highest performance for the detection of GTC seizures (F₁-score = 0.95). A non-commercial wireless EEG device achieved the highest performance for the detection of FIA seizures (F₁-score = 0.88).

DISCUSSION

A preliminary assessment of device capabilities for measuring selected ASM clinical trial secondary endpoints was performed. The need to address key limitations in validation studies is highlighted in order to support future assessments of SDD fitness for ASM clinical trial use. In tandem, a stepwise framework to streamline device testing is put forth. These suggestions provide a starting point for establishing SDD reporting requirements before device integration into ASM clinical trials.

Generalized polyspike train: An EEG biomarker of drug-resistant idiopathic generalized epilepsy

OBJECTIVE

To identify clinical and EEG biomarkers of drug resistance in adults with idiopathic generalized epilepsy.

METHODS

We conducted a case-control study consisting of a discovery cohort and a replication cohort independently assessed at 2 different centers. In each center, patients with the idiopathic generalized epilepsy phenotype and generalized spike-wave discharges on EEG were classified as drug-resistant or drug-responsive. EEG changes were classified into predefined patterns and compared between the 2 groups in the discovery cohort. Factors associated with drug resistance in multivariable analysis were tested in the replication cohort.

RESULTS

The discovery cohort included 85 patients (29% drug-resistant and 71% drug-responsive). Their median age at assessment was 32 years and 50.6% were female. Multivariable analysis showed that higher number of seizure types ever experienced (3 vs 1: odds ratio [OR] = 31.1, 95% confidence interval [CI]: 4.5-214, p < 0.001; 3 vs 2: OR = 14.6, 95% CI: 2.3-93.1, p = 0.004) and generalized polyspike train (burst of generalized rhythmic spikes lasting less than 1 second) during sleep were associated with drug resistance (OR = 10.8, 95% CI: 2.4-49.4, p = 0.002). When these factors were tested in the replication cohort of 80 patients (27.5% drug-resistant and 72.5% drug-responsive; 71.3% female; median age 27.5 years), the proportion of patients with generalized polyspike train during sleep was also higher in the drug-resistant group (OR = 4.0, 95% CI: 1.35-11.8, p = 0.012).

CONCLUSION

Generalized polyspike train during sleep may be an EEG biomarker for drug resistance in adults with idiopathic generalized epilepsy.