Ictal very low frequency oscillation in human epilepsy patients

Using intracranial electroencephalographic recordings, we identified a distinct brain activity in 3 patients with refractory epilepsy characterized by very early occurrence from 8 minutes 10 seconds to 22 minutes 40 seconds prior to clinical seizure onset, periodical appearance of slow negative baseline shift, long interpeak interval of 40 to 120 seconds, and disappearance after clinical seizure. We named this activity "very low frequency oscillation" (VLFO), which reflected a dynamic process during the preictal state. This observation may render new insight into epileptogenesis and provide additional information concerning the epileptogenic zone as well as prediction of epileptic seizures.     

Transition from cortical slow oscillations of sleep to spike-wave seizures

ObjectiveIn cats, spike-wave (SW) seizures have been observed to emerge from cortical slow oscillations (CSOs) and spindles in sleep. We examined a patient’s generalized SW seizures that appeared to emerge from CSOs in sleep.MethodsDense array (256-channel) electroencephalographic (dEEG) data were recorded during long-term monitoring for localizing seizure onset for neurosurgical planning. CSOs were identified on the basis of topographic criteria from dEEG studies of normal human sleep. SW discharges were identified in the surface dEEG and examined with distributed linear inverse neural source estimation.ResultsThis patient’s SW discharges appeared to emerge from a series of CSOs that engaged the left frontal pole. Furthermore, 12 Hz sleep spindles in this patient were often synchronized in time with the CSOs, and in some instances they shared a similar localization over the left frontal pole at the point of seizure onset.ConclusionsThe initial discharges of each seizure engaged both the left frontal pole, which was the primary neural source of this patient’s CSOs, and the left temporal lobe, which seemed critical for the evolution of this patient’s seizures.SignificanceThe correlation of SW seizures with CSOs in animal studies may be observed in humans as well, providing clues to the pathology of arousal regulation in some cases of nocturnal epilepsy.     

Effects of seizure type and waveform abnormality on memory and attention

Deficits in memory, learning, and attention were examined in a sample of 57 patients admitted for investigation of intractable seizure disorder. The patients were grouped according to seizure type and nature of electroencephalographic abnormality. Patients with complex partial seizures were impaired in comparison with controls. Patients with spike-and-wave abnormalities were more impaired on some tests, while those with slow-wave abnormalities were impaired on other tests. These results suggest that, contrary to previous studies, patients with complex partial seizures have greater deficits than other seizure types in some areas of cognitive function.     

Absence seizures in children: clinical and electroencephalographic features

The clinical and electroencephalographic (EEG) features of absence seizures in children were evaluated using EEG frequency modulation radiotelemetry and videotape monitoring. The only seizures evaluated were those with a spike-and-wave or multiple spike-and-wave duration lasting at least 3 seconds. A total of 926 absence seizures (426 typical, 500 atypical) were reviewed in 54 patients. Abnormal interictal EEGs, multiple seizure types, mental retardation, or developmental delay were more likely in patients with atypical absence seizures than in patients with typical absence seizures. Both types of absence seizures usually had a clear onset and cessation. Atypical absence seizures lasted significantly longer than did typical absence seizures. Automatisms occurred more frequently in typical absence seizures than in atypical ones, while decreases in postural tone or tonic activity occurred more frequently in atypical absence seizures. Receptive and expressive speech were retained in some patients during both types of seizures. This study demonstrates that typical and atypical absence seizures are not discrete entities but rather form a continuum. No single clinical feature can adequately distinguish the two seizure types.     

Localization of extratemporal epileptic foci during ictal single photon emission computed tomography.

We obtained single photon emission computed tomography (SPECT) scans with technetium-99M-hexamethyl-propylene-amine-oxime in 11 patients during 12 extratemporal partial seizures (9 simple partial, 3 complex partial). Ten ictal SPECT studies in 9 patients showed a focal region of hyperperfusion, which agreed with electrical seizure onset in 5 and with clinical seizure localization in 4 in whom ictal electroencephalography was not localized. Contralateral cerebellar and ipsilateral basal ganglia hyperperfusion was seen in 3 patients with a frontal lobe seizure focus. Ictal hyperperfusion was well circumscribed, unlike the diffuse hyperperfusion changes reported during temporal lobe seizures. This observation may indicate a different degree of seizure spread in temporal as opposed to extratemporal epilepsy. Because electroencephalographic localization is often elusive in extratemporal seizures, ictal SPECT may be very helpful for the localization of extratemporal foci.     

Operationale Klassifikation der Anfallsformen durch die Internationale Liga gegen Epilepsie: Positionspapier der ILAE-Klassifikations- und Terminologiekommission

The International League Against Epilepsy (ILAE) presents a revised operational classification of seizure types. The purpose of this revision is to recognize that some seizure types can have either a focal or generalized onset, to enable a classification when the onset is unobserved, to include some missing seizure types and to implement a more transparent and understandable nomenclature. Because current knowledge is insufficient to form a scientifically based classification, the 2017 classification is operational (practical) and based on the 1981 classification with the amendments from 2010. The changes include the following: (1) “partial” becomes “focal”; (2) awareness (disturbance of consciousness) is used as a classification criterion of focal seizures; (3) the terms dyscognitive, simple partial, complex partial, psychic and secondarily generalized are eliminated, (4) new focal seizure types include automatisms, behavior arrest, hyperkinetic, autonomic, cognitive, and emotional, (5) epileptic spasms as well as atonic, clonic, myoclonic and tonic seizures can have a focal or generalized onset, (6) focal (seizure with progression) to (a) bilateral tonic-clonic seizure replaces secondarily generalized seizure, (7) new generalized seizure types are absence with eyelid myoclonia, myoclonic absence, myoclonic-atonic, myoclonic-tonic-clonic seizures and (8) seizures of unknown onset may have features that can still be classified. The new classification does not represent a fundamental change but enables greater flexibility and transparency in naming seizure types.     

A possible role for gap junctions in generation of very fast EEG oscillations preceding the onset of, and perhaps initiating, seizures

PURPOSE: We propose an experimentally and clinically testable hypothesis, concerning the origin of very fast (> approximately 70 Hz) EEG oscillations that sometimes precede the onset of focal seizures. These oscillations are important, as they may play a causal role in the initiation of seizures. METHODS: Subdural EEG recordings were obtained from children with focal cortical dysplasias and intractable seizures. Intra- and extracellular recordings were performed in rat hippocampal slices, with induction of population activity, as follows: (a) bath-applied tetramethylamine (an intracellular alkalinizing agent, that opens gap junctions); (b) bath-applied carbachol, a cholinergic agonist; and (c) focal pressure ejection of hypertonic K+ solution. Detailed network simulations were performed, the better to understand the cellular mechanisms underlying oscillations. A major feature of the simulations was inclusion of axon-axon gap junctions between principal neurons, as supported by recent experimental data. RESULTS: Very fast oscillations were found in children before seizure onset, but also superimposed on bursts during the seizure, and on interictal bursts. In slice experiments, very fast oscillations had previously been seen on interictal-like bursts; we now show such oscillations before, between, and after epileptiform bursts. Very fast oscillations were also seen superimposed on gamma (30-70 Hz) oscillations induced by carbachol or hypertonic K+, and in the latter case, very fast oscillations became continuous when chemical synapses were blocked. Simulations replicate these data, when axonal gap junctions are included. CONCLUSIONS: Electrical coupling between principal neurons, perhaps via axonal gap junctions, could underlie very fast population oscillations, in seizure-prone brain, but possibly also in normal brain. The anticonvulsant potential of gap-junction blockers such as carbenoxolone, now in clinical use for treatment of ulcer disease, should be considered.     

Lissencephaly type I: electroencephalographic findings and neuroradiological classification]

Lissencephaly type I is a diffuse type of migration disorder that contains agyria and/or pachygyria on the brain surface. We experienced 5 cases of this disease and evaluated their electroencephalographic findings and seizure types based on the neuroradiological classification of lissencephaly. Ages at seizure onset ranged from 2 months to 4 months (mean 3.2 months). The patients with complete agyria had generalized tonic seizures, and those with pachygyria partial seizures or tonic spasms. The characteristic findings of complete agyria in electroencephalogram were high-voltage alfa activity. The amount of high-voltage slow waves increased with the ratio of pachygyria on the brain surface. The appearance of multifocal spikes and sharp waves suggested irregular arrangement of pachygyria on the brain surface.     

EEG nonstationarity during intracranially recorded seizures: statistical and dynamical analysis.

OBJECTIVE: The investigation of nonstationarity in complex, multivariable signals, such as electroencephalographic (EEG) recordings, requires the application of different and novel approaches to analysis. In this study, we have divided the EEG recordings during epileptic seizures into sequential stages using spectral and statistical analysis, and have as well reconstructed discrete-time models (maps) that reflect dynamical (deterministic) properties of the EEG voltage time series. METHODS: Intracranial human EEG recordings with epileptic seizures from three different subjects with medically intractable temporal lobe epilepsy were studied. The methods of statistical (power spectra, wavelet spectra, and one-dimensional probability distribution functions) and dynamical (comparison of dynamical models) nonstationarity analysis were applied. RESULTS: Dynamical nonstationarity analysis revealed more detailed inner structure within the seizures than the statistical analysis. Three or four stages with different dynamics are typically present within seizures. The difference between interictal activity and seizure events was also more evident through dynamical analysis. CONCLUSIONS: Nonstationarity analysis can reveal temporal structure within an epileptic seizure, which could further understanding of how seizures evolve. The method could also be used for identification of seizure onset. SIGNIFICANCE: Our approach reveals new information about the temporal structure of seizures, which is inaccessible using conventional methods.     

Parietal lobe epilepsy: diagnostic considerations and results of surgery.

Eleven patients, evaluated between 1983 and 1988, with parietal lobe seizure origin as determined by circumscribed lesion detection in all and successful surgery in 10, were retrospectively evaluated in terms of clinical seizure characteristics and electroencephalographic (EEG) findings. Seven of 11 patients reported auras prior to seizures. In 4 patients, auras were lateralized somatosensory sensations, but in 1 they were ipsilateral to the side of seizure origin, and in 2 they had only occurred many years previously when seizures began. Other auras were either nonspecific or suggested seizure origin outside of the parietal lobe. Observed seizures were of two types: asymmetrical tonic seizures with or without clonic activity and complex partial seizures with loss of contact and automatisms. Four patients had only the first type of seizure and an equal number had only the second type. Three patients had both types of seizures during different episodes. Scalp EEGs correctly localized the side and region of seizure onset in only 1 patient. Three additional patients with congruent parietal localization on scalp EEG had additional misleading EEG findings. All patients had lesions detected with neuroimaging, but in 5 this detection occurred after they had been initially evaluated. These 5 patients had intracranial EEG studies designed to localize the region of seizure origin, and correct seizure onset localization was achieved in 2. Of the other 3 patients, false localization occurred in 1, and 2 could not be localized. Four patients with known lesions and 2 of the patients in whom lesions were detected after initial intracranial evaluations were studied with subdural grid electrodes placed over the lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

The “Connectivity Epileptogenicity Index ” (cEI), a method for mapping the different seizure onset patterns in StereoElectroEncephalography recorded seizures

ObjectiveLocalization of epileptogenic brain regions is a crucial aim of pre-surgical evaluation of patients with drug-resistant epilepsy. Several methods have been proposed to identify the seizure onset zone, particularly based on the detection of fast activity. Most of these methods are inefficient to detect slower patterns of onset that account for 20–30% of commonly observed Stereo-Electro-Encephalography (SEEG) patterns. We seek to evaluate the performance of a new quantified measure called the Connectivity Epileptogenicity Index (cEI) in various types of seizure onset patterns.MethodsWe studied SEEG recorded seizures from 51 patients, suffering from focal drug-resistant epilepsy. The cEI combines a directed connectivity measure (“out-degrees”) and the original epileptogenicity index (EI). Quantified results (Out-degrees, cEI and EI) were compared to visually defined seizure onset zone (vSOZ). We computed recall (sensitivity) and precision (proportion of correct detections within all detections) with vSOZ as a reference. The quality of the detector was quantified by the area under the precision-recall curve.ResultsBest results (in terms of match with vSOZ) were obtained for cEI. For seizures with fast onset patterns, cEI and EI gave comparable results. For seizures with slow onset patterns, cEI gave a better estimation of the vSOZ than EI.ConclusionsWe observed that cEI discloses better performance than EI when seizures starts with slower patterns and equal to EI in seizures with fast onset patterns.SignificanceThe cEI is a promising new tool for epileptologists, that helps characterizing the seizure onset zone in sEEG, in a robust way despite variations in seizure onset patterns.     

Automated classification of five seizure onset patterns from intracranial electroencephalogram signals

ObjectiveThe electroencephalographic (EEG) signals contain information about seizures and their onset location. There are several seizure onset patterns reported in the literature, and these patterns have clinical significance. In this work, we propose a system to automatically classify five seizure onset patterns from intracerebral EEG signals.MethodsThe EEG was segmented by clinicians indicating the start and end time of each seizure onset pattern, the channels involved at onset and the seizure onset pattern. Twelve features that represent the time domain characteristics and signal complexity were extracted from 663 seizures channels of 24 patients. The features were used for classification of the patterns with support vector machine - Error-Correcting Output Codes (SVM-ECOC). Three patient groups with a similar number of seizure segments were created, and one group was used for testing and the rest for training. This test was repeated by rotating the testing and training data.ResultsThe feature space formed by both time domain and multiscale sample entropy features perform well in classification of the data. An overall accuracy of 80.7% was obtained with these features and a linear kernel of SVM-ECOC.ConclusionsThe seizure onset patterns consist of varied time and complexity characteristics. It is possible to automatically classify various seizure onset patterns very similarly to visual classification.SignificanceThe proposed system could aid the medical team in assessing intracerebral EEG by providing an objective classification of seizure onset patterns.     

Operational classification of seizure types by the International League Against Epilepsy: Position Paper of the ILAE Commission for Classification and Terminology

The International League Against Epilepsy (ILAE) presents a revised operational classification of seizure types. The purpose of such a revision is to recognize that some seizure types can have either a focal or generalized onset, to allow classification when the onset is unobserved, to include some missing seizure types, and to adopt more transparent names. Because current knowledge is insufficient to form a scientifically based classification, the 2017 Classification is operational (practical) and based on the 1981 Classification, extended in 2010. Changes include the following: (1) “partial” becomes “focal”; (2) awareness is used as a classifier of focal seizures; (3) the terms dyscognitive, simple partial, complex partial, psychic, and secondarily generalized are eliminated; (4) new focal seizure types include automatisms, behavior arrest, hyperkinetic, autonomic, cognitive, and emotional; (5) atonic, clonic, epileptic spasms, myoclonic, and tonic seizures can be of either focal or generalized onset; (6) focal to bilateral tonic–clonic seizure replaces secondarily generalized seizure; (7) new generalized seizure types are absence with eyelid myoclonia, myoclonic absence, myoclonic–atonic, myoclonic–tonic–clonic; and (8) seizures of unknown onset may have features that can still be classified. The new classification does not represent a fundamental change, but allows greater flexibility and transparency in naming seizure types.     

Resolution of catatonia by successful seizure induction via electroconvulsive therapy with electrodes applied bilaterally to the parietotemporal region

Electroconvulsive therapy (ECT) has been shown to be effective in cases of medically intractable mood disorder and schizophrenia. However, some patients receiving ECT have only a short electroencephalographic seizure or no seizure at the maximum stimulus intensity and thus fail to obtain a therapeutic effect. A new treatment option is needed to induce therapeutic seizures in such patients. We report a case of catatonic schizophrenia that was resolved by successful seizure induction by means of ECT with electrodes applied bilaterally to the parietotemporal region after bifrontotemporal ECT failed to induce adequate seizure. We note that parietotemporal ECT can induce therapeutic seizures in patients with a high seizure threshold because more current penetrates the brain due to a decrease in shunted current.     

EEG patterns at the time of focal seizure onset.

We studied the electroencephalographic pattern at the time of focal seizure onset in 41 patients. Progressive rhythmic EEG activity was characteristic of spontaneous focal seizures in man. Focal hypersynchrony was present in 49% of cases and served as an accurate localizing indication of cortical irritability. Interictal sharp or spike discharges were absent in 34% of cases. When present, spike and sharp discharges characteristically attentuate at the onset of rhythmic ictal activity. Recognition of the pattern of rhythmic ictal transformation is often essential for the electroencephalographic diagnosis of focal seizures.     

Seizure onset location shapes dynamics of initiation

ObjectiveIctal electrographic patterns are widely thought to reflect underlying neural mechanisms of seizures. Here we studied the degree to which seizure patterns are consistent in a given patient, relate to particular brain regions and if two candidate biomarkers (high-frequency oscillations, HFOs; infraslow activity, ISA) and network activity, as assessed with cross-frequency interactions, can discriminate between seizure types.MethodsWe analyzed temporal changes in low and high frequency oscillations recorded during seizures, as well as phase-amplitude coupling (PAC) to monitor the interactions between delta/theta and ripple/fast ripple frequency bands at seizure onset.ResultsSeizures of multiple electrographic patterns were observed in a given patient and brain region. While there was an increase in HFO rate across different electrographic patterns, there are specific relationships between types of HFO activity and onset region. Similarly, changes in PAC dynamics were more closely related to seizure onset region than they were to electrographic patterns while ISA was a poor indicator for seizure onset.ConclusionsOur findings suggest that the onset region sculpts neurodynamics at seizure initiation and that unique features of the cytoarchitecture and/or connectivity of that region play a significant role in determining seizure mechanism.SignificanceTo learn how seizures are initiated, researchers would do well to consider other aspects of their manifestation, in addition to their electrographic patterns. Examination of onset pattern in conjunction with the interactions between different oscillatory frequencies in the context of different brain regions might be more informative and lead to more reliable clinical inference as well as novel therapeutic approaches.     

Characterization of epileptic seizure dynamics using Gabor atom density.

OBJECTIVE: The study of epileptic electroencephalograph (EEG) dynamics can potentially provide insights into seizure onset, evolution and termination. We propose a new synthetic measure based on time-frequency decomposition to provide detailed characterization of these dynamic changes. METHODS: The matching pursuit (MP) method allows for continuous time-frequency decomposition. We have developed a derivative of the MP method, the Gabor atom density method (GAD) that facilitates interpretation during the dynamic ictal period. The GAD analysis was applied to intracranial recordings of complex partial seizures (n = 43) of mesial temporal origin in 7 patients. RESULTS: Complex partial seizure occurrence is systematically associated with a GAD increase of 400 +/- 150%. The GAD increase coincides with the electrographical evidence of seizure onset. The similarity between seizures in a given patient is very high with uniform onset slope, maximum level and termination pattern. Global GAD responses over all channels can reveal detailed seizure propagation patterns including secondary independent foci and secondary generalization. CONCLUSIONS: The GAD measure based on the MP decomposition is a reliable tool to detect seizure occurrence in long-term recordings, to differentiate seizures from artifacts on a multi-channel basis and to examine patterns of seizure propagation. The reproducible GAD pattern suggests consistent changes in signal inner structure and may provide new clues about seizure dynamics and evolution. SIGNIFICANCE: The GAD method can provide information about seizure dynamics that can contribute to methods of seizure detection. These analyses may lead to better understanding of seizure termination and help facilitate application of responsive seizure control devices in humans.     

Bitemporal form of partial reading epilepsy: Further evidence for an idiopathic localization-related syndrome

Idiopathic partial reading epilepsy (RE) is a rare syndrome. We report the clinical and electroencephalographic characteristics of two right-handed patients with the following: reading-induced independent bilateral temporal lobe seizures, accompanied by alexia in left (dominant) sided seizures recorded on video-EEG (electroencephalography); subclinical activation over left posterior temporal and occipital electrodes during reading; no spontaneous seizure and no other trigger than reading; onset in adolescence; and history of varying resistance to treatment. Bilateral independent temporal lobe reflex seizures are part of the clinical spectrum of RE. It may result from hyperexcitability of bilateral cortical networks involved in the early steps of the reading process.     

Seizure control and educational outcome in childhood-onset epilepsy.

Patients with epilepsy are more prone to have learning disabilities. This study investigated the therapeutic and educational outcome of 102 epileptic children. Analyzed data included age at onset, etiology, presence of underlying brain lesions, seizure type, and electroencephalographic (EEG) patterns. Cryptogenic seizures, remote symptomatic seizures, and underlying brain lesions were found in 29, 26, and 14 patients, respectively, whereas 47 patients had idiopathic seizures. Eighty-three patients achieved seizure control (46 remained seizure free), and 19 patients remained poorly controlled. Sixty-five patients were in regular schools, and 37 required special education (17 with mental retardation). Predictors for poor seizure control were remote symptomatic seizures, underlying brain lesions, and (when grouped together) hypsarrhythmia and mixed EEG patterns (P < .001). Predictors for special education needs were young age at onset, remote symptomatic seizures, underlying brain lesions, hypsarrhythmia and mixed EEG patterns, and poor seizure control (P < .001). We conclude that in childhood epilepsy, the need for special education is substantial and more common than treatment failure.     

卒中后癫发作时间分布及影响因素的研究

目的 分析卒中后癫发作时间分布特点,并对其影响因素进行研究。 方法 将122例卒中后癫发作患者分为早发性癫发作组（卒中后2周内出现癫发作）60例;晚发性癫发作组（卒中2周后出现癫发作）62例。进行单因素及多因素分析,研究患者的基础情况、卒中的危险因素、卒中的类型、癫发作的类型、发作频次、治疗等情况与早发及晚发的关系。 结果 性别、年龄、卒中危险因素以及脑电图改变在两组间无差异。缺血性卒中出血转化是卒中后癫发作早发的危险因素;早发性癫发作倾向于表现为全面性强直阵挛发作,晚发性癫发作倾向于表现为部分性发作;颞叶病变是卒中后癫发作晚发的危险因素;晚发性癫发作倾向于复发。早发性癫发作患者接受短期治疗的比例较高,晚发性癫发作患者接受长期治疗的比例较高。Logistic多元回归提示糖尿病是卒中后癫发作早发的危险因素（OR＝2.664,95%CI=1.143～6.210,P=0.259）。 结论 糖尿病和缺血性卒中出血转化为卒中后癫发作早发的危险因素;而颞叶病变是卒中后癫痫发作晚发的危险因素,且晚发性癫发作更倾向于复发。