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

Current Controversy: Spikes, Bursts, and Synchrony in Generalized Absence Epilepsy: Unresolved Questions Regarding Thalamocortical Synchrony in Absence Epilepsy

Absence epilepsy is a disorder of thalamocortical networks. Animal models have provided detailed information regarding the core cellular, synaptic, and network features that contribute to the electroencephalogram spike and wave discharge characteristic of typical absence epilepsy. Understanding of seizure networks and dynamics is a critical step toward improving treatments, yet competing conceptual models have evolved to explain seizure initiation and propagation. Recent studies have questioned 2 key model concepts: (1) T-type Ca²⁺ channel-dependent burst firing in thalamic relay neurons may not be essential for seizure generation, bringing into question the proposed mechanism for the antiepileptic drug ethosuximide in reducing thalamic bursting and (2) widespread synchronized neural activity may not be a core feature of the seizures, indicating that reductions in synchrony would not be a productive therapeutic goal. In this review, I will discuss these current findings, highlight the innovative approaches that have enabled these insights, and provide a unified framework that incorporates these sometimes-conflicting ideas. Finally, I lay out future work that will be necessary to finally resolve the remaining issues.

Spatiotemporal propagation patterns of generalized ictal spikes in childhood absence epilepsy

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

The relationship between epileptiform discharges and background activity in the visual analysis of electroencephalographic examinations in dogs with seizures of different etiologies

Electroencephalographic (EEG) recordings in 125 outpatient dogs with various epileptiform encephalopathies were acquired under medetomidine sedation using subdermal wire electrodes. The features of canine EEG (background activity [BGA] and epileptiform discharges [EDs]) were assessed, described and compared. The dogs included neurologically healthy controls (N, n = 19), dogs with portosystemic shunt (PSS, n = 9), dogs with intracranial pathologies (IP, n = 27) and dogs with idiopathic epilepsy (IE, n = 70). A visual EEG analysis revealed significantly more pronounced high voltage, low-frequency BGA in the PSS and IP groups in comparison to the N and IE groups (PSS vs. N, PSS vs. IE P <0.0001; IP vs. N, IP vs. IE P = 0.043). At least one ED in the recording was found in 47.37% (n = 9/19) of the individuals in the N group, 88.9% (n = 8/9) of the dogs in the PSS group, 77.78% (n = 21/27) of the dogs in the IP group and 61.43% (n = 43/70) of the dogs in the IE group. The presence of bilateral symmetric triphasic (BST) waves was significantly higher in the PSS group than in the remaining groups. There was a strong prevalence of spike-waves in dogs with idiopathic epilepsy and of BST waves in dogs with portosystemic shunt. None of the dogs in group N had spike-waves or BST activity. EDs were observed more frequently in high and very high voltage, low frequency BGA than in low voltage, high frequency BGA.

Altered visual contrast gain control is sensitive for idiopathic generalized epilepsies

OBJECTIVE

Visual hyperexcitability in the form of abnormal contrast gain control has been shown in photosensitive epilepsy and idiopathic generalized epilepsies. We assessed the accuracy and reliability of measures of visual contrast gain control in discerning individuals with idiopathic generalized epilepsies from healthy controls.

METHODS

Twenty-four adult patients with idiopathic generalized epilepsy and 32 neurotypical control subjects from two study sites participated in a prospective, cross-sectional study. We recorded steady-state visual evoked potentials to a wide range of contrasts of a flickering grating stimulus. The resultant response magnitude vs. contrast curves were fitted to a standard model of contrast response function, and the model parameters were used as input features to a linear classifier to separate patients from controls. Additionally we compared the relative contribution of model parameters towards the classification using a sparse feature-selection approach.

RESULTS

Classification accuracy was 80% or better. Sensitivity and specificity both were 80-85%. Cross validation confirmed robust classifier performance generalizable across the data from the two samples. Patients' relative lack of gain control at high contrasts was the most important information distinguishing patients from controls.

CONCLUSIONS

Individuals with idiopathic generalized epilepsy were distinguishable from the neurotypical with a high degree of accuracy and reliability by a reduction in gain control at high contrasts.

SIGNIFICANCE

Gain control is an essential neural operation that regulates neuronal sensitivity to stimuli and may represent a novel biomarker of hyperexcitability.

Neocortical gamma oscillations in idiopathic generalized epilepsy

OBJECTIVE

Absence seizures in patients with idiopathic generalized epilepsy (IGE) may in part be explained by a decrease in phasic GABAA (type-A γ-aminobutyric acid) receptor function, but the mechanisms are only partly understood. Here we studied the relation between ictal and interictal spike-wave discharges (SWDs) and electroencephalography (EEG) gamma oscillatory activity (30-60 Hz) in patients with IGE.

METHODS

EEG recordings were obtained of 14 children with IGE (mean age, 8.5 ± 5 years) and 14 age- and sex-matched controls. Time-frequency analysis of each seizure and seizure-free control epochs was performed and cross-coherences of neocortical gamma oscillations were calculated to describe interictal and ictal characteristics of generalized seizures.

RESULTS

SWDs were characterized with an abrupt increase of oscillatory activity of 3-4 and 13-60 Hz, peaking at 3-4 and 30-60 Hz, and with a simultaneous decrease in the 8-12 Hz frequency band. The rise in EEG gamma oscillations was short-lasting and decreased before activity declined at lower frequency ranges. Compared to control patients, patients with epilepsy also showed higher interictal values of mean coherence of gamma activity, but this interictal increase was not significant after post hoc analysis.

SIGNIFICANCE

Our data support the hypothesis that gamma oscillatory activity increase concomitantly with rises in activity of lower EEG frequencies during absence seizures and that the activity starts to cease earlier than lower EEG frequencies. The data did not support a change in gamma activity preceding the 3-4 Hz SWDs. SWDs are hypothetically generated by the synchronous interaction between the thalamus and the cortex, whereas the production of gamma activity is the result of activity in local inhibitory networks. Thus, the modification of SWD by gamma activity may be understood in terms of the cellular and synaptic mechanisms involved.

Retrospective multicenter evaluation of the "fly-catching syndrome" in 24 dogs: EEG, BAER, MRI, CSF findings and response to antiepileptic and antidepressant treatment

The fly-catching syndrome (FCS) is a rare canine condition of sudden, occasional, or constant episodes of biting the air. It may be accompanied by jumping, licking, and swallowing. The etiology of FCS is unknown and controversial. Various explanations for its occurrence have included epileptoid disorders such as visual cortex epileptiform disturbances and simple and complex partial seizures as well as compulsive disorders, hallucinatory behavior, and stereotypy. A retrospective multicenter analysis of 24 dogs with clinical symptoms of FCS is presented. Clinical signs at the time of presentation, the mean age at onset of the disease, the response to treatment, and the clinical outcome were recorded and analyzed in all patients. All dogs underwent clinical, neurological, and otoscopic examinations. Complete blood cell counts (CBCs) and serum chemistry panels were obtained from each dog. Diagnostic testing included MRI and EEG examinations in 21 cases, BAER in 19 cases, and CSF analysis in 20 cases. The EEG revealed spike activity in 8 (38%) of the 21 cases, 7 of which had activity in the occipital lobes. The brainstem auditory evoked response (BAER) revealed three cases of bilateral deafness. The MRI revealed six cases of Chiari malformation (CM), one case of syringohydromyelia (SM), and one case of a falx cerebri meningioma. The dogs were divided into groups according to their treatment protocol. Group A included dogs treated with phenobarbital (PB), and group B consisted of dogs treated with fluoxetine (FLX). Thirty-six percent of the dogs in group A responded to PB, while 100% of the dogs in group B responded to FLX. The results suggest that FCS is more responsive to FLX than PB. However, the etiology of this behavior remains unclear in most cases.

Idiopathic generalized epilepsy: Phenotypic and electroencephalographic observations in a large cohort from South India

PURPOSE

We studied the phenotype and electroencephalographic (EEG) features, and therapeutic aspects of idiopathic generalized epilepsies (IGEs) in South Indian population.

PATIENTS AND METHODS

This prospective cross-sectional hospital-based study was carried out on non-consecutive 287 patients (age 22.2 ± 7.7 years; M:F = 139:148) with IGE syndrome. Their clinical and EEG observations were analyzed.

RESULTS

Majority of the patients had onset of seizures <20 years of age (n = 178; 62%). Thirty one patients (10.8%) had family history of epilepsy. Nearly half of them (49.9%) had <5 years of duration of seizures. The type of IGEs included Juvenile myoclonic epilepsy (JME): 115 (40.1%); IGE with generalized tonic-clonic seizures (GTCS) only: 102 (39.02%); childhood absence epilepsy (CAE): 35 (12.2%); GTCS on awakening: 15 (5.2%); Juvenile absence epilepsy (JAE): 11 (3.8%); and unclassified seizures: 9 (3.1%). The triggering factors noted in 45% were sleep deprivation (20%), non-compliance and stress in 5% each. The EEG (n = 280) showed epileptiform discharges in about 50% of patients. Epileptiform discharges during activation was observed in 40/249 patients (16.1%): Hyperventilation in 32 (12.8%) and photic stimulation in 19 (7.6%). The seizures were well controlled with anti-epileptic drugs (AEDs) in 232 (80.8%) patients and among them, 225 (78.4%) patients were on monotherapy. Valproate (n = 131) was the most frequently prescribed as monotherapy.

CONCLUSIONS

This is one of the largest cohort of patients with IGE. This study reiterates the importance of segregating IGE syndrome and such analysis will aid to the current understanding and management.

Evidence that temporal lobe is a default area in absence epilepsy

Correctly classifying seizures is essential for appropriate epilepsy management. Focal and generalized epilepsy rarely occur independently in the same patient. Cases of focal ictal evolution during seizures that are generalized in onset have been reported though these have included a small heterogeneous series of patients with generalized epilepsy and features on the EEG. We wish to report two patients with absence epilepsy that were noted on video-EEG monitoring to manifest a focal temporal electroclinical transformation from a typical absence seizure. Defining the electroclinical spectrum of absence seizures could add to our understanding of the selective cortical and subcortical networks that are involved in patients with "prototypic" generalized and focal seizures.

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.

Distinct white matter abnormalities in different idiopathic generalized epilepsy syndromes

PURPOSE

By definition idiopathic generalized epilepsy (IGE) is not associated with structural abnormalities on conventional magnetic resonance imaging (MRI). However, recent quantitative studies suggest white and gray matter alterations in IGE. The purpose of this study was to investigate whether there are white and/or gray matter structural differences between controls and two subsets of IGE, namely juvenile myoclonic epilepsy (JME) and IGE with generalized tonic-clonic seizures only (IGE-GTC).

METHODS

We assessed white matter integrity and gray matter volume using diffusion tensor tractography-based analysis of fractional anisotropy and voxel-based morphometry, respectively, in 25 patients with IGE, all of whom had experienced generalized tonic-clonic convulsions. Specifically, 15 patients with JME and 10 patients with IGE-GTC were compared to two groups of similarly matched controls separately. Correlations between total lifetime generalized tonic-clonic seizures and fractional anisotropy were investigated for both groups.

KEY FINDINGS

Tractography revealed lower fractional anisotropy in specific tracts including the crus of the fornix, body of corpus callosum, uncinate fasciculi, superior longitudinal fasciculi, anterior limb of internal capsule, and corticospinal tracts in JME with respect to controls, whereas there were no fractional anisotropy differences in IGE-GTC. No correlation was found between fractional anisotropy and total lifetime generalized tonic-clonic seizures for either JME or IGE-GTC. Although false discovery rate-corrected voxel-based morphometry (VBM) showed no gray matter volume differences between patient and control groups, spatial extent cluster-corrected VBM analysis suggested a trend of gray matter volume reduction in frontal and central regions in both patient groups, more lateral in JME and more medial in IGE-GTC.

SIGNIFICANCE

The findings support the idea that the clinical syndromes of JME and IGE-GTC have unique anatomic substrates. The fact that the primary clinical difference between JME and IGE-GTC is the occurrence of myoclonus in the former raises the possibility that disruption of white matter integrity may be the underlying mechanism responsible for myoclonus in JME. The cross-sectional study design and relatively small number of subjects limits the conclusions that can be drawn here; however, the absence of a correlation between fractional anisotropy and lifetime seizures is suggestive that the white matter abnormalities observed in JME may not be secondary to seizures.

Single-channel amplitude integrated EEG recording for the identification of epileptic seizures by nonexpert physicians in the adult acute care setting

OBJECTIVE

Although several studies have shown the potential of amplitude integrated electroencephalography (aEEG) in detecting neonatal seizures, no publications have evaluated the diagnostic use of aEEG for the detection of seizures in adult patients.

METHODS

In this prospective blinded observational study, bifrontal single-channel electroencephalography (EEG) recordings were performed with a portable EEG monitor (CSM M3 ICU, Danmeter-Goalwick Holdings Limited, Odense, Denmark) during the out-of-hospital care of emergency cases. Four intensive care unit (ICU) physicians received training in the interpretation of aEEG recordings. After the training they evaluated the stored aEEG traces for the presence of epileptic seizure activity during the recording time. The physicians were blinded to the clinical data of the patients. The results obtained were compared with the clinical diagnosis and the evaluation of the raw EEG signal. The level of interrater agreement was quantified using Fleiss' ĸ.

RESULTS

The aEEG traces from 10 patients with generalized epileptic seizures and 46 patients without seizures were analysed. Overall, the nonexpert ICU physicians failed to identify recordings obtained from patients with seizures reliably, when compared with clinical diagnosis and the single-channel EEG results (mean sensitivity 40%, range 40-60%; mean specificity 89%, range 87-93%). Agreement between observers was high for the cases with seizures ( ĸ = 0.80 ± 0.13). Patients who suffered status epilepticus during the recordings were difficult to identify by most raters.

CONCLUSION

Recording of aEEG without access to the raw EEG data is not a reliable diagnostic tool for the identification of epileptic seizures in the hands of nonexpert ICU physicians.

Antiepileptic drugs withdrawal in patients with idiopathic generalized epilepsy

OBJECTIVES

To estimate the risk of seizure recurrence after antiepileptic drugs (AED) withdrawal and to identify related predictive features in patients with idiopathic generalized epilepsy (IGE) commencing at developing age (up to 16 year).

METHODS

Medical records of consecutive patients with IGE from two refferal hospitals were evaluated between 2001 and 2009. Inclusion criteria were clinical and EEG diagnosis of IGE and follow up for at least 2years after the AED withdrawal. The cohort consisted of 59 patients (38 females, 21 males). Follow up after withdrawal lasted 2-10years (median 3) Time to seizure relapse and predictive factors were analyzed by survival methods.

RESULTS

There were 21 (35.6%) patients with childhood absence epilepsy (CAE), 11 (18.6%) with juvenile absence epilepsy (JAE), 10 (16.9%) with isolated primary GTC seizures, and 17 (28.8%) with juvenile myoclonic epilepsy (JME). The relapses occured in 23 (52.2%) patients: one (6.2%) with CAE, 4 (50%) with JAE, 8 (80%) with IGE with GTC seizures and all with JME. During the first 6 months 54.5% patients relapsed (20% during withdrawal), 63.6% within 12 months, 81.8% within18 months and 95.4% within 24 months after withdrawal. Female gender, age at onset of seizures, seizure types, EEG worsening during/after AED withdrawal and age at withdrawal were significantly associated with relapse risk according to univariate analysis. In multivariate analysis, retained significant factors were: seizure types and EEG worsening.

CONCLUSION

Diagnosis of the specific IGE syndrome strongly affects relapse rate: the lowest was in CAE, the highest in JME. Independent risk factors for seizure relapse were: seizure type and EEG worsening during and/or after withdrawal.

A new locus for autosomal dominant generalized epilepsy associated with mild mental retardation on chromosome 3p

PURPOSE

Generalized epilepsies are clinically and genetically heterogeneous syndromes. Idiopathic generalized epilepsy (IGE), which has a strong genetic background, is not associated with any additional clinical features, such as mental retardation (MR). Herein we report results of linkage analysis in a large family with autosomal dominant (AD) generalized epilepsy associated with MR.

METHODS

We identified a four-generation kindred with several affected members with generalized epilepsy without any evidence for secondary causes. Electroencephalography (EEG) studies and magnetic resonance imaging (MRI) results were reviewed when available. We performed a genome-wide linkage analysis.

KEY FINDINGS

Fourteen individuals were classified as affected and an additional three were considered as nonpenetrant obligatory carriers. Thirteen affected individual had a history of generalized tonic-clonic seizures, and absence seizures were reported in nine affected individuals. There was no history of preceding febrile seizures. MR was present in nine affected individuals with epilepsy but the other affected individuals had normal intelligence. Neuroimaging did not reveal any structural abnormalities and EEG studies were consistent with IGE rather than symptomatic generalized epilepsy. Genetic analysis detected a group of markers with logarithmic (base 10) of odds (LOD) score >3 on chromosome 3p spanning a 5.5 Mbp region. Sequencing of several candidate genes, including dynein light chain-A, golgin subfamily a4, leucine rich repeat (in FLII) interacting gene, serine/threonine-protein kinase DCAMKL3 (doublecortin- like and CAM kinase-like 3), laforin (EPM2A) interacting protein 1 (EPM2AIP1, programmed cell death 6 interacting protein, and CLIP-associating protein 2 (cytoplasmic linker-associated protein 2) (hOrbit2) genes did not identify the disease-causing mutations.

SIGNIFICANCE

We report the identification of a genetic locus for generalized epilepsy associated with MR on chromosome 3p. Affected individuals have a form of genetic epilepsy with generalized seizures variably associated with MR. Despite the presence of MR in several affected patients, epilepsy phenotype was not fully consistent with symptomatic epilepsy and suggests a biologic continuum between symptomatic epilepsies and IGE.

Ictal patterns in children: an illustrated review

Detailed knowledge of electroencephalographic patterns accompanying epileptic seizures in children is paramount to the correct identification of epileptic seizures and syndromes. In this article, we present a review of ictal patterns of different seizure types in children, illustrating with examples collected in our video-EEG laboratory at Pequeno Príncipe Hospital.

Polyspike ictal onset absence seizures

Polyspike ictal-onset absence seizures may predict an unfavorable response to treatment in patients with epilepsy. The authors assessed absences in adults with idiopathic generalized epilepsy (IGE) associated with polyspike onset before classic 3-Hz generalized spike-and-waves (GSW). Seven adults with absences undergoing video EEG were accompanied by 3-Hz GSW, preceded by polyspike-ictal onset by >1 second in two or more seizures. The clinical profile, interictal, and ictal EEG noted had at least 1-year follow-up. A total of 1,164 patients underwent video EEG, with 58 (5%) receiving a diagnosis of IGE or subsyndrome. All seven patients with absence seizures had an ictal EEG pattern of polyspike onset prior to 3-Hz GSW. Four female and three male adults (mean age, 28.9 years) had absence as their primary seizure type. All but one had seizure onset between 4 and 20 years and failed at least two broad-spectrum antiepileptic drug trials. Typical features of IGE were normal neurologic examination, brain MRI, and 3- to 3.5-Hz GSW and generalized polyspike-and-waves on interictal EEG. Atypical features included learning disability (2 of 7), absence status (1 of 7), and paroxysmal fast activity during nonrapid eye movement sleep (3 of 7).

CONCLUSIONS

Polyspikes are common during video EEG in adults with IGE. Absence seizures with polyspike onset 3-Hz GSW suggest an intermediary form of IGE that may be drug resistant.

Suicide attempts in adult patients with idiopathic generalized epilepsy

AIMS

To study clinical features of adult patients with idiopathic generalized epilepsy with special attention to suicidal behavior.

METHODS

We reviewed the medical records of 145 consecutive adult patients with electro-clinically confirmed idiopathic generalized epilepsy and identified those with a history of at least one attempted suicide. Clinical variables in relation to their epilepsy and psychiatric conditions were analyzed.

RESULTS

Seven patients (4.8%) had a history of suicide attempts with drug overdose, and one of these patients committed suicide after multiple attempts. All attempts were made interictally without direct relation to their epileptic seizures. All had at least one co-morbid mental disorder (two with dual diagnosis). Although their psychiatric diagnoses varied, they all appeared to have increased emotional instability and poor impulse control. Only one patient's attempt was directly associated with her co-morbid depression.

CONCLUSIONS

Physicians managing people with epilepsies should be aware of psychiatric disturbances and suicidal behavior in idiopathic 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.

Psychiatric comorbidity in adult patients with idiopathic generalized epilepsy

We reviewed the medical records of 157 adult (18 years) patients with firmly diagnosed idiopathic generalized epilepsy (IGE) to investigate the extent and the type of psychiatric comorbidity and its relationship to various IGE syndromes and other epilepsy-related neurobiological factors. Forty-one patients (26.1%, 14 men and 27 women, median age: 34.0 years, range: 18-68, mean: 36.5) had comorbid mental disorders according to the 10th revision of the International Classification of Diseases (ICD-10) criteria, with four patients having a dual diagnosis. Mood disorders were the most common comorbid mental disorder (46.7%), followed by anxiety-panic disorder (26.7%). Comorbid psychiatric disorders occurred in all syndromes and in association with all seizure types, and, as in focal epilepsies, seizure control was significantly better in patients without psychiatric comorbidity (40.5% vs 19.5%, chi(2)(1)=5.873, P=0.015).

Usefulness of a morning routine EEG recording in patients with juvenile myoclonic epilepsy

OBJECTIVE

To evaluate if a standard awake EEG recording in the morning is superior to afternoon awake EEG session in detecting generalized epileptiform discharges (GEDs) in patients with juvenile myoclonic epilepsy (JME).

METHODS

The study group included 29 consecutive patients (23 women; mean age 22.3+/-6.3 years; age at onset of JME 15.4+/-3.4 years) with JME. Out of 29 patients 5 were untreated, 9 patients were treated with valproate, 8 with lamotrigine, 6 with levetiracetam and 1 patient with valproate plus phenobarbital. Two routine consecutive interictal EEG recordings were performed at 9a.m. and at 3p.m., respectively, while the subject was awake, on the same day after a a regular nocturnal sleep at own home.

RESULTS

The morning EEG recording showed GEDs (i.e., generalized polispike and waves, photoparoxysmal response, or both). in 20/29 patients. In 15 of these 20 patients, the afternoon recording was normal and this difference was statistically significant (p < or = 0.001). Moreover, there was a striking reduction of GEDs in three of the remaining five patients. Nine/29 patients had both morning and afternoon EEG recording normal.

CONCLUSIONS

The results of this study have illustrated a significant greater rate of detection of generalized epileptiform abnormalities by performing standard awake EEG in the morning in comparison with an afternoon session.

Electroencephalograms in the diagnosis and management of the epilepsies

The generic term ‘epilepsy’ embraces a particular group of disorders of the CNS but by itself is of limited clinical value. Intense clinical and genetic research over the last few decades has identified a large number of well-defined epilepsy syndromes with different clinical, electroencephalograms (EEG), neuropsychological and neuroimaging profiles, natural history and prognosis, conditions that ultimately require different management. There is evidence that early treatment can reduce the risk of seizure recurrence (First Seizure Trial Group, 1993), and its efficacy depends largely on the appropriate drug choice in relation to the particular clinical syndrome. Therefore, a diagnosis of epilepsy is no longer sufficient; identification of the particular form or syndrome is the cornerstone of meaningful, optimal management.