Coexistence of temporal lobe and idiopathic generalized epilepsies

EEG in focal and generalized epilepsies: Pearls and perils

Correctly diagnosing and classifying seizures and epilepsies is vital to ensure a tailored approach to patients with epilepsy. The ILAE seizure classification consists of two main groups: focal and generalized. Establishing if a seizure is focal or generalized is essential to classify the epilepsy type and the epilepsy syndrome, providing more personalized treatment and counseling about prognosis. EEG is one of the most essential tools for this classification process and further localization of the epileptogenic focus. However, some EEG findings are misleading and may postpone the correct diagnosis and proper treatment. Knowing the most common EEG pitfalls in focal and generalized epilepsies is valuable for clinical practice, avoiding misinterpretations. Some atypical features can be challenging in focal epilepsies, such as secondary bilateral synchrony, focal epileptiform activity induced by hyperventilation and photic stimulation, and non-focal slowing. On the other hand, more than 60 % of persons with idiopathic generalized epilepsies have at least one type of atypical abnormality. In this manuscript, we describe and illustrate some of the most common EEG findings that can make even experienced epileptologists question not only where the epileptogenic focus is but also if the patient has focal or generalized epilepsy. This review summarizes the perils and provide some pearls to assist EEG readers.

Focal electroclinical features in generalized tonic-clonic seizures: Decision flowchart for a diagnostic challenge

OBJECTIVE

Bilateral tonic-clonic seizures with focal semiology or focal interictal electroencephalography (EEG) can occur in both focal and generalized epilepsy types, leading to diagnostic errors and inappropriate therapy. We investigated the prevalence and prognostic values of focal features in patients with idiopathic generalized epilepsy (IGE), and we propose a decision flowchart to distinguish between focal and generalized epilepsy in patients with bilateral tonic-clonic seizures and focal EEG or semiology.

METHODS

We retrospectively analyzed video-EEG recordings of 101 bilateral tonic-clonic seizures from 60 patients (18 with IGE, 42 with focal epilepsy). Diagnosis and therapeutic response were extracted after ≥1-year follow-up. The decision flowchart was based on previous observations and assessed concordance between interictal and ictal EEG.

RESULTS

Focal semiology in IGE was observed in 75% of seizures and 77.8% of patients, most often corresponding to forced head version (66.7%). In patients with multiple seizures, direction of head version was consistent across seizures. Focal interictal epileptiform discharges (IEDs) were observed in 61.1% of patients with IGE, whereas focal ictal EEG onset only occurred in 13% of seizures and 16.7% of patients. However, later during the seizures, a reproducible pattern of 7-Hz lateralized ictal rhythm was observed in 56% of seizures, associated with contralateral head version. We did not find correlation between presence of focal features and therapeutic response in IGE patients. Our decision flowchart distinguished between focal and generalized epilepsy in patients with bilateral tonic-clonic seizures and focal features with an accuracy of 96.6%.

SIGNIFICANCE

Focal semiology associated with bilateral tonic-clonic seizures and focal IEDs are common features in patients with IGE, but focal ictal EEG onset is rare. None of these focal findings appears to influence therapeutic response. By assessing the concordance between interictal and ictal EEG findings, one can accurately distinguish between focal and generalized epilepsies.

Coexistence of temporal lobe epilepsy and idiopathic generalized epilepsy

OBJECTIVE

We investigated the frequency of coexistence of temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) in a retrospective database study. We also explored the underlying pathomechanisms of the coexistence of TLE and IGE based on the available information, using bioinformatics tools.

METHODS

The first phase of the investigation was a retrospective study. All patients with an electro-clinical diagnosis of epilepsy were studied at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 until 2023. In the second phase, we searched the following databases for genetic variations (epilepsy-associated genetic polymorphisms) that are associated with TLE or syndromes of IGE: DisGeNET, genome-wide association study (GWAS) Catalog, epilepsy genetic association database (epiGAD), and UniProt. We also did a separate literature search using PubMed.

RESULTS

In total, 3760 patients with epilepsy were registered at our clinic; four patients with definitely mixed TLE and IGE were identified; 0.1% of all epilepsies. We could identify that rs1883415 of ALDH5A1, rs137852779 of EFHC1, rs211037 of GABRG2, rs1130183 of KCNJ10, and rs1045642 of ABCB1 genes are shared between TLE and syndromes of IGE.

CONCLUSION

While coexistence of TLE and IGE is a rare phenomenon, this could be explained by shared genetic variations.

Electron microscopic GABA evaluation in hippocampal mossy terminals of genetic absence epilepsy rats receiving kindling stimulations

Objective: The hypotheses related to the fact of epileptic mechanisms are mainly based on excitation-inhibition imbalance in central nervous system. GAERS (Genetic Absence Epilepsy Rats from Strasbourg) is a well-known animal model of absence epilepsy, and frequently used in experimental studies. In the present study, we aimed to examine possible morphological and gamma-aminobutyric acid (GABA) density changes in GAERS hippocampus after electrical kindling stimulations. Methods: All control and test group rats received 6 kindling stimulations. Rats were decapitated 1 h after the last stimulation. Ultrastructural GABA immunocytochemistry was used to evaluate GABA density quantitatively in mossy terminals of hippocampal CA3 region. Results: GABA levels were less in kindling groups compared to their controls, and in GAERS groups compared to Wistar groups; mitochondrial and dendritic spine area ratios were greater in GAERS groups compared to Wistar groups, although all these evaluations were statistically nonsignificant. Depletion of synaptic vesicles was evident in the mossy terminals of kindling groups. Conclusion: The reason of decreased levels of GABA found in the present study might be that GABA has been released from the synaptic pool rapidly at an early time period after the last stimulation, for compansation mechanisms. Depletion of synaptic vesicles observed in kindling groups shows that even 6 kindling stimulations have an impact of changing hippocampal morphology in trisynaptic cycle. The increased mitochondrial area in GAERS might be related to the increased mitochondrial activity. The increased dendritic spine area might be related to the increased performance of learning in GAERS. Our findings indicating that absence epilepsy and temporal lobe epilepsy have different mechanisms of epileptogenesis might be a basis for further experimental studies

Investigation of Neurogenesis in Kindled Wistar and Genetic Absence Epilepsy Rats

Objective: The most common type of epilepsy affecting about 50 million people worldwide is temporal lobe epilepsy (TLE). Chemical and electrical kindling methods in animals can be used to form TLE model. In the present study, it was aimed to investigate neurogenesis in the hippocampus of adult kindled Wistar rats and genetic absence epilepsy rats from Strasbourg (GAERS) rats by immunofluorescence methods. Methods: Adult Wistar and GAERS albino rats weighing 250-300 gr were injected pentylenetetrazole (PTZ) (35 mg/kg, s.c.) every other day to produce chemical kindling. Animals having 5 times grade 5 seizures were considered to be kindled. Intracardiac perfusion was performed under deep anesthesia on the 7th and 14th days after the last grade 5 seizure. Immunofluorescence methods were used to demonstrate newly formed neurons, astroglial cells, and mature neurons, by using anti-doublecortin (DCX), anti-glial fibrillary acidic protein (GFAP), and anti- neuronal nuclear antigen (NeuN) primary antibodies, respectively. Sections were then examined under a fluorescence microscope. Results: DCX (+) cells were found to be increased in GAERS control groups compared to the Wistar control groups; and in Wistar PTZ groups compared to the Wistar control groups. DCX (+) cells were decreased in GAERS PTZ groups compared to their controls and to Wistar PTZ groups. Conclusion: The findings of the present study suggest that the resistance to electrical kindling of GAERS reported in previous studies might be related to the increased neurogenesis in this strain.

Are Absence and Limbic Seizures Mutually Exclusive?: An Experimental Approach to Enigmatic Clinical Concept

The impressive advances in the several disciplines including neurophysiology, molecular biology, neuroimmunology, neurogenetics, neuroimaging, and neuropharmacology of epilepsies have been stimulating a mutual interaction among basic scientists, clinicians, and professionals from other disciplines, leading to the identification of clinical questions and then the design of basic science paradigms to test enigmatic clinical issues. Based on a clinical observation that the coexistence of genetic (idiopathic) generalized typical absence and mesial temporal lobe epilepsy in the same patient is extremely rare and debatable, we addressed the rare coexistence in the same individual, designed an experimental approach to test the validity of this clinical concept and to study the underlying mechanisms involved. Here we presented evidence of a mutual cross-interaction in the circuits involved in typical absence and temporal lobe epilepsy. This article delineates a phenomenological picture and comprehends a theoretical understanding of a mutual cross-interaction in typical absence as a representative of genetic generalized epilepsies and limbic epilepsy in which seizures often start from the mesial temporal lobe.

Genetic generalized epilepsies with frontal lesions mimicking migratory disorders on the epilepsy monitoring unit

Objective

Some patients with genetic generalized epilepsy (GGE) may present with ambiguous and atypical findings and even focal brain abnormalities. Correct diagnosis may therefore be difficult.

Methods

We retrospectively collected six patients investigated on the epilepsy monitoring unit with MRI abnormalities mimicking focal cortical dysplasia (FCD-like) or heterotopias, but with semiology and EEG features of GGE. We compared them to four additional patients with GGE and nonmigratory abnormalities.

Results

All six patients presented with frontal MRI lesions: radial ("transmantle," n = 4), cortical-subcortical (n = 1), and periventricular heterotopia (n = 1). Five had positive family histories. Semiologic lateralizing signs compatible with the lesion were seen in four. Five patients had 3/s spike-wave complexes, with an asymmetric appearance in three. Regional EEG changes matched with the side of the abnormality in three patients. Invasive EEG (n = 2) or postoperative outcomes (n = 3) argued against an ictogenic role of the MRI abnormalities. Histology showed mild malformation of cortical development, but no focal cortical dysplasia. The six patients were finally diagnosed with juvenile myoclonic epilepsy (n = 2), juvenile absence epilepsy (n = 2), or GGE not further specified (nfs, n = 2). Compared to these patients, the other four (final diagnoses: childhood absence epilepsy, n = 1; perioral myoclonia with absences, n = 1; and GGE nfs, n = 2) had no lateralizing EEG findings.

Significance

Patients with GGE may have coincidental MRI abnormalities. These cases are challenging as frontal epilepsy and GGE can present with similar semiologies. GGE with coincidental FCD-like lesions/heterotopias is in particular difficult to diagnose as patients have more lateralizing features (in semiology and EEG) than those with tumors. A detailed noninvasive presurgical evaluation may be justified. We point out red flags that may help to distinguish GGE from frontal epilepsy, even in the presence of brain abnormalities: 3/s spike waves (even if asymmetric), changing lateralizing signs at different times, and a positive family history hinting at GGE.

Outcomes of low-dose valproic acid treatment in patients with juvenile myoclonic epilepsy

PURPOSE

There are conflicting data regarding the drug dose that is sufficient to achieve seizure control as well as the parameters of seizure remission in juvenile myoclonic epilepsy (JME). The present study aimed to identify factors that contribute to seizure control in JME and to evaluate factors associated with JME remission and the efficacy of low-dose valproic acid (VPA) therapy.

METHODS

This retrospective, cross-sectional study included a total of 215 patients (121 female and 94 male; mean age: 28.03 ± 8.43 [14-59] years) diagnosed with JME. The patients were divided into remission and refractory groups. Remission was defined as a seizure-free (myoclonic, absence, and/or generalized tonic-clonic) period of at least 2 years. Patients in whom remission was achieved with VPA monotherapy were further divided into two groups according to the use of low-dose VPA therapy (VPA ≤ 750 mg/day and >750 mg/day). Potential contributing factors were evaluated in terms of the relationship between the dose and the remission parameters.

RESULTS

Remission was achieved with VPA monotherapy in 116 patients (87.9%) in the remission group; the VPA dose was ≤750 mg in 77.6% of the patients. The dose of VPA was higher in patients with absence seizure who achieved remission (p = 0.026). Remission was achieved with a lower dose of VPA in females than in males (p = 0.004).

CONCLUSIONS

Low-dose VPA can be used to achieve remission in JME. However, identification at follow-up visits of the factors that may affect remission may change the planned effective dose of VPA.

Phenotypic analysis of 303 multiplex families with common epilepsies

Gene identification in epilepsy has mainly been limited to large families segregating genes of major effect and de novo mutations in epileptic encephalopathies. Many families that present with common non-acquired focal epilepsies and genetic generalized epilepsies remain unexplained. We assembled a cohort of 'genetically enriched' common epilepsies by collecting and phenotyping families containing multiple individuals with unprovoked seizures. We aimed to determine if specific clinical epilepsy features aggregate within families, and whether this segregation of phenotypes may constitute distinct 'familial syndromes' that could inform genomic analyses. Families with three or more individuals with unprovoked seizures were studied across multiple international centres. Affected individuals were phenotyped and classified according to specific electroclinical syndromes. Families were categorized based on syndromic groupings of affected family members, examined for pedigree structure and phenotypic patterns and, where possible, assigned specific familial epilepsy syndromes. A total of 303 families were assembled and analysed, comprising 1120 affected phenotyped individuals. Of the 303 families, 117 exclusively segregated generalized epilepsy, 62 focal epilepsy, and 22 were classified as genetic epilepsy with febrile seizures plus. Over one-third (102 families) were observed to have mixed epilepsy phenotypes: 78 had both generalized and focal epilepsy features within the same individual (n = 39), or within first or second degree relatives (n = 39). Among the genetic generalized epilepsy families, absence epilepsies were found to cluster within families independently of juvenile myoclonic epilepsy, and significantly more females were affected than males. Of the 62 familial focal epilepsy families, two previously undescribed familial focal syndrome patterns were evident: 15 families had posterior quadrant epilepsies, including seven with occipito-temporal localization and seven with temporo-parietal foci, and four families displayed familial focal epilepsy of childhood with multiple affected siblings that was suggestive of recessive inheritance. The findings suggest (i) specific patterns of syndromic familial aggregation occur, including newly recognized forms of familial focal epilepsy; (ii) although syndrome-specificity usually occurs in multiplex families, the one-third of families with features of both focal and generalized epilepsy is suggestive of shared genetic determinants; and (iii) patterns of features observed across families including pedigree structure, sex, and age of onset may hold clues for future gene identification. Such detailed phenotypic information will be invaluable in the conditioning and interpretation of forthcoming sequencing data to understand the genetic architecture and inter-relationships of the common epilepsy syndromes.

Evaluation of GAD67 immunoreactivity in the region of substantia nigra pars reticulata in resistance to development of convulsive seizure in genetic absence epilepsy rats

OBJECTIVE:

Nonconvulsive absence epilepsy and convulsive epilepsy seizures are rarely seen in the same patient. It has been demonstrated that there is a resistance to development of convulsive seizures in genetic absence epilepsy models. The present study investigated glutamic acid decarboxylase (GAD) immunoreactivity in the brain region related to the interaction of these two seizure types, namely substantia nigra pars reticulata (SNR) subregions, SNR_anterior and SNR_posterior.

METHODS:

Nonepileptic adult male Wistar rats and Genetic Absence Epilepsy Rats from Strasbourg (GAERS) were used. Experimental groups of Wistar and GAERS were electrically stimulated for kindling model to induce convulsive epileptic seizures. An electrical stimulation cannula was stereotaxically implanted to the basolateral amygdala and recording electrodes were placed on the cortex. Sagittal sections of SNR were used to evaluate immunohistochemical reaction. Sections were incubated with anti-GAD67 antibody. Densitometric analysis of GAD67 immunoreactive neurons was performed using photographs of stained sections. One-way analysis of variance and post hoc Bonferroni test were used for statistical analysis of the data.

RESULTS:

There was no difference in GAD67 immunoreactivity of SNR subregions of control Wistar and control GAERS. An increase in GAD67 immunoreactivity was detected in SNR_posterior subregion of stimulated Wistar rats, whereas there was a decrease in GAD67 immunoreactivity in SNR_posterior of stimulated GAERS. The difference in GAD67 immunoreactivity between these two groups was statistically significant.

CONCLUSION:

Level of synthetized gamma-aminobutyric acid in SNR_posterior subregion plays an important role in the interaction of nonconvulsive absence epilepsy seizures and convulsive epilepsy seizures.

The role of the substantia nigra pars reticulata in kindling resistance in rats with genetic absence epilepsy

OBJECTIVE

Genetic Absence Epilepsy Rats from Strasbourg (GAERS) show a resistance to secondary generalization of focal limbic seizures evoked by kindling. The substantia nigra pars reticulata (SNR) is involved in the propagation and modulation of seizures in kindling. We first examined the role of the SNRanterior and SNRposterior subregions in the resistance to the development of kindling in GAERS. Subsequently, to determine whether kindling resistance relates to differential sensitivity of γ-aminobutyric acid γ-aminobutyric acid (GABA)ergic or dopaminergic SNR neurons to kindling, we studied the effects of kindling-inducing stimulations on parvalbumin (PRV; GABAergic neuron marker) or tyrosine hydroxylase (TH; dopaminergic neuron marker) immunoreactivity (ir), respectively, in GAERS and in nonepileptic control (NEC) Wistar rats that lack kindling resistance.

METHODS

Adult male GAERS were implanted with a stimulation electrode in the amygdala, and bilateral injection cannulas for lidocaine or saline injection (30 min before each kindling stimulation until the animals reached three stage 5 seizures or the 22 stimulations) into the SNRanterior or SNRposterior . In another experiment, PRV-ir in SNRanterior and SNRposterior and TH-ir in SNRposterior only were densitometrically compared in GAERS-SHAM, NEC-SHAM GAERS-STIM, and NEC-STIM animals (6 kindling stimulations).

RESULTS

Bilateral SNRposterior infusions of lidocaine eliminated the kindling resistance and resulted in stage 5 generalized motor seizures in all kindled rats. Bilateral lidocaine infusions in the SNRanterior failed to alter the kindling resistance in GAERS. PRV-ir in the SNRposterior was unaltered in GAERS-STIM but increased in NEC-STIM group. Cellular TH-ir in the SNRposterior significantly increased by kindling stimulations in both NEC-STIM and GAERS-STIM groups.

SIGNIFICANCE

The kindling resistance in GAERS is mediated by the SNRposterior in a lidocaine-sensitive manner. The insensitivity to kindling stimulation of PRV-ir in SNRposterior of GAERS but not NEC rats, implicate GABAergic SNRposterior neurons in kindling resistance. In contrast, the observed stimulation-specific increase in TH-ir in the SNRposterior is unrelated to kindling resistance.

A unique ictal EEG pattern in a patient with the coexistence of generalized and focal epilepsy

The coexistence of focal and generalized epilepsy is rare. We report on a 17-year-old male with drug-resistant focal epilepsy and idiopathic generalized epilepsy (IGE). He began to experience generalized tonic-clonic seizures (GTCS) at the age of 3 years, with a good response to phenobarbital. At the age of 14 years, he began to experience complex partial seizures (CPS). Video-electroencephalography (video-EEG) telemetry showed the coexistence of right temporal spikes and bursts of generalized spike-wave (GSW). The ictal EEG showed a unique EEG pattern characterized by a 4- to 5-second burst of GSW followed by rhythmic delta activity over the right temporal region. A magnetic resonance image (MRI) showed right hippocampal sclerosis. The patient underwent a right temporal lobectomy that significantly improved his seizure control. He was rendered seizure free of the complex partial seizures and improvement of the GTCS. This case illustrates a very uncommon ictal EEG pattern, and shows that the decision for surgery in patients with focal drug-resistant epilepsy should not be affected by coexistent generalized epilepsy.

Clinical aspects of juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME) is a recognizable, frequent epileptic syndrome. The most typical ictal phenomenon is bilateral myoclonia without loss of consciousness (M), with most patients also presenting with generalized tonic-clonic seizures (GTCSs) and some with absence seizures (ASs). The most striking features of JME are its onset around the time of puberty and the fact that seizure episodes occur after awakening from a sleep period or in the evening relaxation period and are facilitated by sleep deprivation and sudden arousal. Photic sensitivity is common in the EEG laboratory but uncommon or unrecognized in daily life. The clinical features of JME make it easy to diagnose. In recent years, awareness of JME has increased, and patients are often accurately diagnosed clinically before confirmation by EEG. The typical circumstance at diagnosis is a first GTCS episode, and one learns during the interview that the patient has had M in the morning for some time before the GTCS episode. There are only few differential diagnoses: the adolescent-onset progressive myoclonus epilepsies, or other forms of idiopathic generalized epilepsies of adolescence. With JME being so common, we propose that a first GTCS episode in a teenager should be considered as revealing JME until proven otherwise.

Lifetime prognosis of juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME) is among the most common types of genetic epilepsies, displaying a good prognosis when treated with appropriate drugs, but with a well-known tendency to relapse after withdrawal. The majority of patients with JME have continuing seizures after a follow-up of two decades. However, 17% are able to discontinue medication and remain seizure-free thereafter. Clinicians should remember that there is a small but still considerable subgroup of JME patients whose seizures are difficult to treat before informing patients with newly-diagnosed JME about their "benign" prognosis. This resistant course is not fully explained, though there are many suggested factors. The dominating myoclonic seizures disappear or diminish in severity in the fourth decade of life. Despite the favorable seizure outcome in most of the cases, 3/4 of patients with JME have at least one major unfavorable social outcome. The possible subsyndromes of JME, its genetic background, and its pathophysiological and neuroimaging correlates should be further investigated.

Surgically proven coexistence of focal and generalized epilepsy: a case report

The coexistence of focal and idiopathic generalized epilepsy (IGE) is rarely observed, and the mechanism underlying this situation remains unknown. We report a 13-year-old girl with well-controlled generalized epilepsy and medically-refractory left temporal lobe epilepsy. She underwent intracranial EEG recording, which demonstrated two characteristic seizure patterns of generalized ictal onset and left mesial temporal onset. In addition, two types of interictal spike distribution, including the left mesial temporal region and generalized spikes, were also supportive of the coexistence of left mesial temporal lobe epilepsy and IGE. Thereafter, a left anterior temporal lobectomy and post-surgical medication significantly improved her seizure outcome. This case illustrates the importance of considering surgical management for patients with medically-intractable focal epilepsy coexisting with generalized epilepsy.

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

PURPOSE

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

METHODS

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

KEY FINDINGS

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

SIGNIFICANCE

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

Long term outcomes in patients with preoperative generalized interictal epileptiform abnormalities following amygdalohippocampectomy

We evaluated long term surgical outcomes in 21 patients with temporal lobe epilepsy and presurgical generalized interictal epileptiform discharges (IEDs). Following amygdalohippocampectomy, 12 patients (57.1%) were noted to have favorable outcomes (Engel classification of I-II). Favorable outcomes were significantly associated with a history of auras prior to seizure onset (p=0.021), the absence of generalized IEDs on postoperative EEG (p=0.024), and the presence of focal slowing on postoperative EEG (p=0.045).

Coexistence of idiopathic generalized epilepsy among surgically treated patients with drug-resistant temporal lobe epilepsy

INTRODUCTION

Failure to identify the association antiepileptic drug (AED)-resistant temporal lobe epilepsy (TLE) with idiopathic generalized epilepsy (IGE) can interfere with decision for anterior temporal lobectomy (ATL) and prediction of post-ATL seizure outcome.

METHODS

Out of the 664 consecutive patients who underwent ATL between March 1995 and December 2007, 12 (1.8%) had coexisting IGE. The decision for ATL was made after a thorough discussion in the multidisciplinary patient management conference based upon the concordance between the clinical, electroencephalographic and magnetic resonance imaging data. All of them underwent epilepsy surgery for AED-resistant TLE.

RESULTS

In seven of the 12 patients, IGE was not identified until post-ATL. During a median follow-up period of 8.5 years, 8 of our 12 patients were seizure-free; the remaining 4 patients only had infrequent myoclonus. In two them, AEDs were discontinued; others were on montherapy for IGE.

CONCLUSIONS

Our study highlights the rare association of IGE with TLE, the most common AED-resistant focal epilepsy syndrome. As the seizure outcome following ATL is similar in AED-resistant TLE patients with and without IGE, their co-existence is not a contraindication for ATL. Future studies should explore the molecular genetic basis of the rare association between these two epilepsy syndromes.

Carisbamate has powerful disease-modifying effects in the lithium-pilocarpine model of temporal lobe epilepsy

Lithium-pilocarpine, a relevant model of temporal lobe epilepsy was used to test the neuroprotective and antiepileptogenic effects of carisbamate. Status epilepticus (SE) was induced in adult rats by lithium and pilocarpine. Carisbamate (30, 60, 90, and 120 mg/kg) was injected at 1 and 9 h after SE onset and continued twice daily for 6 additional days. The reference groups received diazepam instead of carisbamate. Neuroprotection was assessed during the first 24 h of SE with Fluoro-Jade B and after 14 days with thionine staining. SE severity and epileptic outcome were assessed by video, and surface and depth electroencephalographic recordings. At the two highest doses, carisbamate treatment reduced SE severity; produced strong neuroprotection of hippocampus, ventral cortices, thalamus, and amygdala; prevented mossy fiber sprouting in the dentate gyrus of the hippocampus; and delayed or suppressed the occurrence of spontaneous motor seizures. Rats with no spontaneous motor seizures displayed spike-and-wave discharges that share all the characteristics of absence seizures. In conclusion, carisbamate is able to induce strong neuroprotection and affect the nature of epileptogenic events occurring during and after lithium-pilocarpine status epilepticus, reflecting marked insult- and disease-modifying effects.

Ultrastructural GABA immunocytochemistry in the mossy fiber terminals of Wistar and genetic absence epileptic rats receiving amygdaloid kindling stimulations

The existence of absence epilepsy and temporal lobe epilepsy in the same patient is not common in clinical practice. The reason why both types of seizures are rarely seen in the same patient is not well understood. Therefore, we aimed to investigate kindling in a well known model of human absence epilepsy, genetic absence epilepsy rats from Strasbourg (GAERS). In the present study, we analyzed whether the GABA content of GAERS that received kindling stimulations was altered in the hippocampal mossy fiber terminals compared to non-epileptic control (NEC) Wistar rats. For this purpose, we used an immunocytochemical technique at the ultrastructural level. Ultrathin sections were immunolabeled with anti-GABA antibody and transmission electron microscopy was used for the ultrastructural examination. The number of gold particles per nerve terminal was counted and the area of the nerve terminal was determined using NIH image analysis program. The GABA density was found to be higher in sham-operated GAERS than sham-operated Wistar rats. The density was increased in kindling Wistar group compared to sham-operated Wistar and kindling GAERS groups. No statistical difference was observed between sham-operated GAERS and kindling GAERS groups. The increase in GABA levels in stimulated Wistar rats may be a result of a protective mechanism. Furthermore, there may be strain differences between Wistar rats and GAERS and our findings addressing different epileptogenesis mechanisms in these strains might be a basis for future experimental studies.

Localized cortical injections of ethosuximide suppress spike-and-wave activity and reduce the resistance to kindling in genetic absence epilepsy rats (GAERS)

Models of genetic absence epilepsy are resistant to secondary generalization of focal limbic seizures. This correlates with the postnatal development of spike-and-wave discharges (SWDs), a hallmark of absence seizures arising from a cortical focus in the perioral region of somatosensory cortex. Ethosuximide injected at this site suppresses SWDs. The effect of this suppression on kindling in "Genetic Absence Epilepsy Rats from Strasbourg" (GAERS), has been compared for postnatal 30 day (PN30) rats having immature SWDs and adult (>4 months) rats having mature SWDs. Non-epileptic Wistar and GAERS rats were implanted with a basolateral amygdaloid stimulation electrode, bilateral injection cannulas into the cortical perioral focus, and cortical recording electrodes. Following recovery cortical injections of ethosuximide or saline were made and after 30min rats were given 36 stimulations or until Racine's stage 5 seizures were produced. All Wistar rats (PN30 and adult) treated with saline or ethosuximide reached stage 5. Of GAERS given saline, 33% (PN30) and 43% (adults) were resistant to kindling; after ethosuximide pups behaved like Wistars, but adults showed a delay in kindling relative to Wistars. These findings imply that mechanisms underlying kindling resistance are related but not limited to SWD activity in animals with genetic absence epilepsy.

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

PURPOSE

To investigate the focal interictal EEG abnormalities in adult patients with absence seizures (ASs) and to identify their clinical, EEG and semiological correlates.

METHODS

Fifty patients older than 18 years, diagnosed as having IGE with AS documented with ictal recordings. Interictal focal sharp or spike-waves and strictly focal paroxysmal slow activity were considered as focal EEG features. The patients having focal EEG features were classified as "Group I", whereas the remaining of them was classified as "Group II".

RESULTS

We observed focal findings in 34% of the patients, mainly in frontotemporal (41%), and frontal (29%) regions. There were no significant differences with respect to the clinical parameters such as sex, epilepsy duration, positive family history and the age of the onset between the groups. Psychiatric co-morbidities were significantly higher in Group I when compared to Group II (P=0.00). Accompanying automatisms were higher in Group I, whereas eye deviation during absences was higher in Group II. In Group I, the asymmetry of the ictal discharges was more frequently observed. Focal EEG features were more frequently seen in juvenile absence epilepsy syndrome, without reaching a significance level.

CONCLUSION

The focal findings in adult absence epilepsy patients could have some unknown etio-pathogenetic and prognostic implications. We emphasize the cautious interpretation of isolated interictal focal EEG abnormalities to prevent a wrong diagnosis of focal epilepsy in patients who may indeed suffer from generalized epilepsy.

Characteristics of generalised epileptiform activity

OBJECTIVE

To study the age-related occurrence of specific features of generalised epileptiform activity (GEA), their correlation with EEG background activity (BA), and their internal correlation.

METHODS

17,723 consecutive routine EEGs from 12,511 patients were annotated and categorised into a database. The first EEG containing GEA from all 325 patients with such activity were selected and categorised for GEA features. The BA was studied in multivariable fractional polynomial regression models including intervening variables. The GEA features were studied in similar models for age-dependency and internal correlation.

RESULTS

High GEA-amplitude and low GEA-frequency correlated with BA slowing. The occurrence of 'irregular spike/sharp slow wave' pattern increased with age (p=0.003). Hyperventilation sensitivity was not age-related. There was no correlation between hyperventilation sensitivity and photoparoxysmal response. The age-related probability for specific GEA-types was established.

CONCLUSIONS

High GEA-amplitude and low GEA-frequency correlate with BA slowing, indicating cerebral cortical dysfunction. Hyperventilation sensitivity and photoparoxysmal response independently increase the yield of EEG. There is no age-dependency for hyperventilation sensitivity showing that an upper age threshold for hyperventilation provocation is inappropriate.

SIGNIFICANCE

The results extend our understanding of GEA and help the electroencephalographer in weighing the various GEA components.

Intra-amygdaloid injection of kainic acid in rats with genetic absence epilepsy: the relationship of typical absence epilepsy and temporal lobe epilepsy

We showed previously that genetic absence epilepsy rats from Strasbourg (GAERS) resist secondary generalization of focal limbic seizures after electrical kindling. We now investigate the effect of intra-amygdaloid injection of kainic acid, as another model of temporal lobe epilepsy, focusing on epileptogenesis, spike-and-wave discharges (SWDs), and the transition from basal to SWD states in GAERS. The EEG was recorded from the hippocampus and cortex of adult GAERS and Wistar rats before kainic acid injections into the basolateral amygdala and for 3 months thereafter. EEG and video recordings monitored SWDs and convulsive seizures. We analyzed spectral changes of the EEG during kainic acid-induced status epilepticus, SWDs, for 10 s before (silent period) and for 2 s before (transition period) SWDs. After the injection of kainic acid, all animals experienced convulsive seizures for at least 3 h. The first convulsive seizure was significantly delayed in GAERS compared with Wistar rats. SWDs and increases in power of the delta, alpha, and beta frequency ranges during the transition period disappeared after the kainic acid injection for 1-3 d and gradually reappeared. Power increases in the delta and alpha ranges were significantly correlated with the number of SWDs, in the beta and alpha ranges with their mean duration. Neo-Timm's staining at the end of experiments demonstrated that mossy fiber sprouting in GAERS is less pronounced than in Wistar rats. Our findings show that mechanisms underlying absence epilepsy and temporal lobe epilepsy interact with each other, although a site of this interaction remains to be defined.

Hippocampal kindling in rats with absence epilepsy resembles amygdaloid kindling

PURPOSE

WAG/Rij and GAERS rats show delays or resistance to secondary generalization of limbic seizures during amygdaloid kindling. In this study, we aimed to evaluate the kindling from a different limbic site, hippocampus, and to compare its effects on spike-and-wave discharges (SWDs) with that of amygdaloid kindling.

METHODS

Recording electrodes were implanted epidurally and a stimulation/recording electrode was implanted into the ventral hippocampus in the WAG/Rij, GAERS and Wistar rats. Animals received kindling stimulation twice daily at their afterdischarge thresholds until they reached stage 5 seizures, or the maximum number of stimulations (50) had been delivered. The EEG was recorded to analyze SWDs and afterdischarge durations.

RESULTS

All Wistar rats reached stage 5 by the 34th stimulation. 4 of 8 WAG/Rij rats and 3 of 6 GAERS rats displayed stage 4/5 seizures (kindling-prone rats); the rest stayed at stage 2 seizures (kindling-resistant rats) even after 50th stimulations. The cumulative duration and number of SWDs decreased in the post-stimulation period after the first stage 2 seizures, whereas these parameters increased after the first stage 3 seizures in the kindling-prone WAG/Rij and GAERS. The peak frequency of SWDs and its harmonics decreased significantly only in the GAERS group after stage 4 seizures.

CONCLUSION

Hippocampal kindling resembles amygdaloid kindling in showing a delay of or resistance to secondary seizure generalization, which supported the interaction of thalamo-cortical and limbic circuitry in GAERS and WAG/Rij.

Effect of stage 2 kindling on local cerebral blood flow rates in rats with genetic absence epilepsy

PURPOSE

Genetic absence epilepsy rats from Strasbourg (GAERS) are resistant to the progression of kindling seizures. We studied local cerebral blood flow (LCBF) changes in brain regions involved in seizures in both GAERS and nonepileptic rats (NEC) to map the differences that may be related to the resistance to kindling.

METHODS

Electrodes were implanted in the amygdala of adult NEC and GAERS male rats, which were stimulated to reach stage 2. Quantitative autoradiographic measurements of LCBF were performed by the [(14)C]-iodoantipyrine ([(14)C]IAP) autoradiographic technique allowing the precise mapping of regional perfusion changes. LCBF rates were measured bilaterally in 43 brain regions. The tracer infusion lasted for 60 s and started at 15 s before seizure induction.

RESULTS

Rates of LCBF increased in stimulated GAERS and NEC groups compared to nonstimulated controls. The LCBF increase in stimulated GAERS was larger and more widespread than that observed in stimulated NEC. The LCBF increase in the somatosensory cortex, ventrobasal and anterior thalamic nuclei, hypothalamus, subthalamic nucleus, piriform, entorhinal and perirhinal cortex, amygdala, CA2 region of hippocampus, and substantia nigra was statistically significantly larger in stimulated GAERS compared to stimulated NEC rats.

CONCLUSION

The results show that more brain regions are activated by kindling stimulation in GAERS. This widespread activation in GAERS involves the somatosensory cortex and thalamus, which are both known to be involved in the expression of absence seizures as well as numerous limbic regions thought not to play a role in the expression of absence seizures, suggesting an interaction between corticothalamocortical and limbic circuitries.

The role of the inherited genetic background on the consequences of lithium-pilocarpine status epilepticus: study in Genetic Absence Epilepsy Rats from Strasbourg and Wistar audiogenic rats

The susceptibility of rats with genetically inherited epilepsy to the genesis and consequences of secondary temporal lobe epilepsy is unknown. Here, we induced lithium-pilocarpine status epilepticus (SE) in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) or in Wistar audiogenic sensitive (AS) rats. Wistar AS needed less pilocarpine than GAERS and Non-Epileptic Rats (NERs) to develop SE. Sixty six, 40 and 5% of Wistar AS, GAERS and NERs, respectively, died within 24 h after SE. In GAERS, SE prevented the occurrence of absence seizures for 5 days. Thereafter a limited number of absence seizures with low amplitude and short duration were recorded. Wistar AS developed limbic epilepsy within 9 days after SE while GAERS and NERs needed 36-39 days to develop spontaneous motor seizures. Neuronal loss consecutive to SE was similar in the three strains and particularly marked in limbic forebrain and parahippocampal cortices. In conclusion, the development of focal limbic epilepsy in GAERS largely impairs the expression of absence seizures. The genetic background underlying the expression of audiogenic seizures sensitizes strongly the rats to a further insult and compromises their survival.

Interictal EEG in Temporal Lobe Epilepsy in Childhood

The authors clarified the value of interictal discharges and verified which extratemporal regions may also show epileptiform activity in temporal lobe epilepsy (TLE) in childhood. Thirty consecutive patients aged 3 to 18 years (mean age = 12.16 years; 16 male) with TLE associated with hippocampal atrophy were studied. Each patient had 1 to 15 interictal EEG recordings (mean: 5.6; total = 192 EEGs). Video-EEG monitoring was performed in 20 patients. All patients had MRI. The findings were compared with a control group of 53 consecutive TLE adult outpatients with hippocampal atrophy. Each adult patient underwent 3 to 21 routine EEGs (mean: 10.67; total = 566). Interictal EEGs of children with TLE showed extratemporal epileptiform discharges more frequently than EEGs of adults with TLE. Frontal, parietal, and occipital discharges were more frequently seen in children (P < 0.05). These results suggest a close interaction between temporal and other cerebral regions in children with epilepsy and provide further evidence of the existence of neural networks.

Idiopathic generalized epilepsies: clinical and electroencephalogram diagnosis and treatment

This review concentrates on the principles of the clinical and electroencephalogram diagnosis of idiopathic generalized epilepsies and their treatment. The electroclinical variability of the main seizure types is detailed and particular emphasis is placed on the differential diagnosis from other seizures and nonepileptic conditions that is essential for the optimal management of these patients. The authors review the various idiopathic generalized epilepsy subsyndromes and conditions that are included in both the 1989 International League Against Epilepsy classification system and the recently proposed International League Against Epilepsy scheme, but also syndromes and forms that have not been formally recognized. Finally, the authors describe the principles of antiepileptic drug treatment with the old and newer drugs, and their specific indications and contraindications in the various syndromes and seizure types.

Amygdala kindling in the WAG/Rij rat model of absence epilepsy

PURPOSE

The kindling model in rats with genetic absence epilepsy is suitable for studying mechanisms involved in the propagation and generalization of seizure activity in the convulsive and nonconvulsive components of epilepsy. In the present study, we compared the amygdala kindling rate and afterdischarge characteristics of the nonepileptic Wistar control rat with a well-validated model of absence epilepsy, the WAG/Rij rat, and demonstrated the effect of amygdala kindling on spike-and-wave discharges (SWDs) in the WAG/Rij group.

METHODS

Electrodes were stereotaxically implanted into the basolateral amygdala of rats for stimulation and recording and into the cortex for recording. After a recovery period, the animals were stimulated at their afterdischarge thresholds. EEG was recorded to analyze SWDs and afterdischarge durations. The seizure severity was evaluated by using Racine's 5-stage scale.

RESULTS

All nonepileptic control and four of seven WAG/Rij animals reached a stage 5 seizure state, whereas three animals failed to reach stage 3, 4, or 5 and stayed at stage 2 after application of 30 stimulations. Interestingly, WAG/Rij rats, resistant to kindling, demonstrated a significantly longer duration of SWDs on the first day of the experiment before kindling stimulation than did the kindled WAG/Rij animals. Additionally, the cumulative total duration and the number of SWDs after the kindling stimulation were statistically increased compared with SWDs before kindling stimulation.

CONCLUSIONS

The results of our study demonstrate that the progress of amygdala kindling is changed in rats with genetic absence epilepsy, perhaps as a consequence of the hundreds of daily SWDs.

Coexistence of focal and idiopathic generalized epilepsy in the same patient population

PURPOSE

To review the clinical, electrographic, radiological, and pathological findings of patients with coexistent idiopathic generalized and partial epilepsy syndromes.

METHODS

We performed a medical record review and a phone interview with all patients hospitalized to the Cleveland Clinic epilepsy monitoring unit (EMU) between 1992 and 2002 who fulfilled clinical and EEG criteria of coexistent partial and generalized epilepsy syndromes.

RESULTS

Seven patients were identified. Two (29%) were men with a mean age of 26 years. Four had a history of febrile seizures. Family history was positive in five. Mean duration of the generalized epilepsy syndrome was 11 years, and of the focal epilepsy 18 years. An equal number of patients developed focal versus generalized epilepsy first. Interictal EEG activity was predominantly generalized. Four had video-EEG documentation of both types of seizures. In the rest, only focal seizures were recorded but interictal activity strongly suggested a coexistent generalized epilepsy. MRI showed hippocampal atrophy in all, and hippocampal dysplasia in three. Five patients had PET imaging, all with hypometabolism in areas corresponding to the ictal onset on EEG. Four patients underwent epilepsy surgery with good surgical outcome and pathological confirmation of hippocampal sclerosis in all.

CONCLUSION

We found a 0.2% incidence of coexistent focal and primary generalized epilepsy. Febrile seizures and a positive family history were common. Good seizure control was achieved after temporal lobectomy, even when interictal generalized activity predominated.

Idiopathic generalized epilepsies imitating focal epilepsies

Classification of epileptic seizures and epilepsy syndromes as either focal or generalized is a fundamental and early part in the diagnostic process and is generally fairly easily accomplished. However, in patients with idiopathic generalized epilepsies, seizure and EEG features may suggest, particularly to the unwary, the occurrence of focal rather than generalized seizures. Misinterpretation of typical absence seizures as focal seizures, especially as temporal lobe seizures and of myoclonic seizures as focal clonic seizures, is a relatively common error and focal features during generalized tonic-clonic seizures may also be quite common. Sequences of seizures in idiopathic generalized epilepsies (such as absences or jerks followed by generalized tonic-clonic seizures) may also cause confusion. Versive and circling seizures are seizure types whose ictal semiology is clearly focal; nevertheless such seizures are described in idiopathic generalized epilepsies accompanied by generalized EEG discharges. The occurrence of focal EEG abnormalities in certain idiopathic generalized epilepsy syndromes is common. This is best known in juvenile myoclonic epilepsy.

Use and Abuse of EEG in the Diagnosis of Idiopathic Generalized Epilepsies

This article concentrates on the role of electroencephalograms (EEGs) in the diagnosis and management of patients with idiopathic generalized epilepsies (IGEs). We review the morphologic and behavioral characteristics of the interictal and ictal EEG markers of IGE that should guide recording strategies to augment its diagnostic yield, and we attempt to delineate those particular features that may be relevant to different IGE syndromes. We also explore the electrographic boundaries between IGEs and cryptogenic/symptomatic generalized and focal epilepsies, and focal/secondary generalized epilepsies, with particular relevance to the phenomena of focal abnormalities and secondary bilateral synchrony, commenting on possible diagnostic pitfalls and areas of uncertainty.

Status epilepticus in immature rats leads to behavioural and cognitive impairment and epileptogenesis

It remains under dispute whether status epilepticus (SE) in the perinatal period or early childhood or the underlying neuropathology is the cause of functional impairment later in life. The present study examined whether SE induced by LiCl-pilocarpine in normal immature brain (at the age of 12 or 25 days; P12 or P25) causes cognitive decline and epileptogenesis, and the data were compared to those of rats undergoing SE as adults. Rats in the P12 group had impaired memory (repeated exposure to open-field paradigm) and emotional behaviour (lower proportion of open-arm entries and higher incidence of risk assessment period in elevated plus-maze) when assessed 3 months after SE, although not as severe as in the older age groups. Importantly, video-electroencephalography monitoring 3 months after SE demonstrated that 25% of rats in the P12 and 50% in P25 group developed spontaneous seizures. Only nonconvulsive seizures (ictal activity in hippocampus accompanied by automatisms) were recorded in the P12 group whereas rats in the P25 group exhibited clonic convulsions. The present findings indicate that SE is harmful to the immature brain as early as P12, which might be compared with early infancy in humans.

Clinical, electroencephalographic, and behavioral features of temporal lobe epilepsy in childhood

This study describes the clinical, electroencephalographic, and behavioral features of 36 children with temporal lobe epilepsy. Patients were divided into two groups: group A, with 6 patients (< 6 years), and group B, with 30 patients (6-18 years). Statistical analysis was performed considering the significance level of .05. Regarding the clinical features of the focal seizures, motor components were more frequently seen in children younger than 6 years of age (P < .01), whereas automatisms were more frequently seen in patients older than 6 years of age (P < .05). Associated myoclonic seizures were more frequent in the younger age group (P < .01). Behavioral disorders such as hyperactivity and aggressiveness and speech delay were more common in the younger age group (P < .05). Temporal lobe epilepsy in children younger than 6 years of age is more frequently associated with motor components, myoclonic seizures, behavioral disorders, and speech delay. Conversely, temporal lobe epilepsy in older patients has frequent automatisms.

The Coexistence of Idiopathic Generalized Epilepsy and Partial Epilepsy

PURPOSE

To describe the clinical, EEG, and imaging data of a series of patients with features of both idiopathic generalized epilepsy (IGE) and partial epilepsy.

METHODS

A computerized database of all patients attending the regional epilepsy clinic was used to identify all patients with IGE. Case notes were reviewed, and cases with clinical evidence of co-existing partial epilepsy identified.

RESULTS

Nine cases with clinical features of a partial and generalized-onset epilepsy and with electrophysiological evidence of IGE are presented. This represented <1% of the overall IGE population in the clinic. Five (55.6%) patients are currently in remission, with successful epilepsy surgery in one patient.

CONCLUSIONS

The coexistence of IGE and partial epilepsy is uncommon, and if appropriate treatment with a broad-spectrum antiepileptic drug is given, then the prognosis can be good. Surgery should be considered for those cases with medically intractable partial-onset seizures as part of this syndrome.

Clinical and electroencephalographic follow-up after a first unprovoked seizure

We studied the role of clinical and electroencephalographic factors in the follow-up of children and adolescents after a first unprovoked seizure, and their correlation with recurrence and risk for epilepsy. We conducted a 24-month follow-up of 109 patients aged 1 month to 16 years who had a first unprovoked seizure. We analyzed the characteristics of the first seizure, perinatal history, family history of seizures, electroencephalographic patterns and their influence on seizure recurrence, and calculated risk for subsequent epilepsy. Fifty-six patients (51.4%) had recurrent seizures. The bivariate statistical analysis revealed that maternal prenatal disease (relative risk = 2.02, P = 0.03) and an abnormal electroencephalogram (relative risk = 2.89, P = 0.0003) were significantly associated with seizure recurrence. Other factors (male sex, partial first seizure, vaginal delivery, family history of seizures, and sleep state) approached statistical significance. Logistic regression revealed that the only variable significantly associated with recurrence was an abnormal electroencephalographic pattern on the first examination (relative risk = 2.48, P = 0.003). Cumulative risk ranged from 50-68% at 24 months when the first electroencephalogram was abnormal, and from 26-36% when it was normal. We concluded that the electroencephalogram may have an important diagnostic value in the prognosis of epileptic seizure recurrence in children and adolescents.

Resistance to propagation of amygdaloid kindling seizures in rats with genetic absence epilepsy

PURPOSE

The existence of absence epilepsy and temporal partial seizure pattern in the same patient is an uncommon state. In the present study, we aimed to evaluate whether the process of kindling as a model of complex partial seizures with secondary generalization is altered in rats with genetic absence epilepsy.

METHODS

Six- to 12-month-old nonepileptic control Wistar rats and genetic absence epileptic rats from Strasbourg (GAERS) were used in the experiments. One week before the experiments, bilateral stimulation and recording electrodes were implanted stereotaxically into the basolateral amygdala and cortex, respectively. Animals were stimulated at their afterdischarge threshold current twice daily for the process of kindling and accepted as fully kindled after the occurrence of five grade 5 seizures. Bilateral EEGs from amygdala and cortex were recorded continuously during 20 min before and 40 min after each stimulus.

RESULTS

All control Wistar rats were fully kindled after stimulus 12 to 15. Although the maximal number of stimulations had been applied, GAERS remained at stage 2, and no motor seizures were observed. The afterdischarge duration in bilateral amygdala and the cortex after the kindling stimulus was shorter in GAERS when compared with control rats.

CONCLUSIONS

Occurrence of only grade 2 seizures and no observation of grade 3-5 seizures in GAERS with the maximal number of stimulations would suggest that the generalized absence seizures may be the reason of the resistance in the secondary generalization of limbic seizures during amygdala kindling.

Prognostic factors in the surgical treatment of medically intractable epilepsy associated with mesial temporal sclerosis

OBJECTIVES

To assess the prognostic factors determining seizure remission after temporal lobectomy for intractable epilepsy associated with mesial temporal sclerosis (MTS) at pathology.

METHODS

The clinical and investigative features of 116 consecutive patients who had temporal lobe surgery for drug-resistant epilepsy and MTS at pathology were assessed using actuarial statistics and logistic regression analysis.

RESULTS

At a median follow-up of 63 months the probability of achieving at least a 1-year period of continuous seizure freedom was 67%. Factors contributing to a favourable outcome were interictal EEG localization to the operated lobe and the absence of secondarily generalized seizures. These were also selected in the multivariate analysis, although at lower statistical significance (P=0.08 and 0.09, respectively). Perinatal complications were associated with a significantly worse outcome but overall, complicated febrile convulsions and congruent neuropsychological deficits were not significantly predictive variables.

CONCLUSIONS

The present findings may aid in the non-invasive presurgical assessment of patients with intractable TLE and clinical and neuroimaging evidence of MTS.

Ictal single photon emission computed tomography in absence seizures: apparent implication of different neuronal mechanisms

Absence seizures represent a complex group of epilepsy, characterized by lapse of consciousness with staring. Bilateral, synchronous, and symmetric bursts of 3-Hz spike-and-wave discharges are observed on the electroencephalogram, whereas interictal background activity is normal. This kind of epilepsy has to be differentiated from other generalized epilepsies such as juvenile absence epilepsy and juvenile myoclonic epilepsy. Moreover, absence seizures, together with generalized spike-and-wave discharges, may coexist with other types of epilepsy such as frontal lobe epilepsy, temporal lobe epilepsy, benign epilepsy with centrotemporal spikes, and childhood epilepsy with occipital paroxysms. We have carried out ictal single photon emission computed tomography (SPECT) in 10 patients with clinical evidence of absence seizures with the aim to better understand and to distinguish this kind of seizure as primarily or secondarily generalized to a specific area and to obtain more information on the neuronal mechanisms involved in the different types of seizures, usually not identifiable at the first appearance. During the long follow-up period (9 months to 14 years), 7 of the 10 examined patients underwent interictal SPECT when they became seizure free. Our data permitted, in two patients, the diagnosis of childhood absence seizures; in three patients, they suggested the possibility of later appearance of other seizure types, on the basis of focal hyperperfusion indicating a possible focal firing. In three of the examined patients, the diagnosis of idiopathic localization-related epilepsies mimicking childhood absence seizures could be performed. In the last two patients, the hypothesis of a coexistence of absences with partial and generalized seizures was considered. From our results, it can be presumed that ictal SPECT findings may contribute to the physiopathologic classification of the different types of epilepsies. Moreover, anticonvulsant treatment more appropriate to the different forms of seizures can be used.