Biomedical subjects

Béla Clemens

Publications and source records attributed to Béla Clemens.

10 recordsLinked to original sources

PubMed2006

Quantitative EEG effects of carbamazepine, oxcarbazepine, valproate, lamotrigine, and possible clinical relevance of the findings.

UNLABELLED: Quantitative EEG (QEEG) effects of therapeutic doses of carbamazepine (CBZ), oxcarbazepine (OXC), valproate (VA) and lamotrigine (LA) monotherapy were investigated in patients with beginning epilepsy. Baseline waking EEG (EEG1) was recorded in the untreated state, the second EEG (EEG2) was done after 8 weeks of reaching the therapeutic dose. Left occipital data were used for analysis. QEEG target parameters were absolute band-power (delta: AD, theta: AT, alpha: AA, beta: AB), and alpha mean frequency (AMF). Group effects (untreated versus treated condition in the CBZ, VA, OXC, LA groups) were computed for each target parameter. One group with benign rolandic epilepsy remained untreated for clinical reasons and served to estimate the QEEG test-retest differences. In addition, the individual QEEG response to each drug was calculated as (EEG2-EEG1). RESULTS: statistically significant (p<0.05) group differences indicated the QEEG domain systematically affected by the drugs. CBZ caused AT increase and AMF decrease. OXC caused AMF decrease. VA and LA did not decrease AMF (LA even increased it), but reduced broad-band power. Individual power and AMF changes showed considerable variability in each group. >0.5 Hz AMF decrease (that was reported to predict cognitive impairment in prior studies) occurred in 10/41 patients in the CBZ group but never in the OXC, VA, LA groups. The results may be utilized in planning further studies addressing the relationship between antiepileptic drugs and their CNS effects. In addition, the relationship of AED-related cognitive impairment and AMF changes was discussed.

Adolescent↗

PubMed2005

Forced normalisation precipitated by lamotrigine.

PURPOSE: To report two patients with lamotrigine-induced forced normalization (FN). METHODS: Evaluation of the patient files, EEG, and video-EEG records, with special reference to the parallel clinical and EEG changes before, during, and after FN. RESULTS: This is the first documented report of lamotrigine-induced FN. The two epileptic patients (one of them was a 10-year-old girl) were successfully treated with lamotrigine. Their seizures ceased and interictal epileptiform events disappeared from the EEG record. Simultaneously, the patients displayed de novo occurrence of psychopathologic manifestations and disturbed behaviour. Reduction of the daily dose of LTG led to disappearance of the psychopathological symptoms and reappearance of the spikes but not the seizures. CONCLUSIONS: Lamotrigine may precipitate FN in adults and children. Analysis of the cases showed that lamotrigine-induced FN is a dose-dependent phenomenon and can be treated by reduction of the daily dose of the drug.

Adolescent↗

PubMed2005

The perisylvian epileptic network. A unifying concept.

In this work the authors provide evidences for a unifying concept of the syndromes of benign focal childhood epilepsies, Landau-Kleffner syndrome, and electrical status epilepticus in sleep treating them as a spectrum of disorders with a common transient, age dependent, non lesional, genetically based epileptogenic abnormality, the nature of which is still not known. The electro-clinical features of these syndromes are congruent with the different degree involvement of the perisylvian cognitive network and with the involvement of the thalamo-cortical associative system of variable degree. These epilepsies are characterized by the abundance of regional epileptiform discharges in sharp contrast with the rare and in several cases lacking seizures. The nature and severity of interictal cognitive symptoms are closely related to localization within the network and amount of epileptic interictal discharges. Spike-wave discharges are attributed to an alternation of overexcitation (spikes) and overinhibition (waves). The recurrent overinhibition represented by the wave of the discharges may interfere with the continuous depolarization of the cells of a large population of neurons, which is a requirement of the overt seizures. The overinhibition also interfere with cognitive processes which are correlated with the continuous presence of the fast (gamma) activity, binding the required cortical areas. Hence the recurrent inhibition works against the existence of the binding fast frequency activity. This is the assumed reason for the co-existence of the relative lack of overt seizures and in the same time for the frequently observed epileptogenic cognitive deficit symptoms ("cognitive epilepsies"). The time course of these syndromes overlaps with important developmental milestones. The frequent epileptic discharges alters the evolution of the perisylvian network developing late after early childhood and is very vulnerable for any interference in this imprinting time for speech and other cognitive functions. This spectrum of disorders represents a type of age linked, mild to severe 'epileptic encephalopathy' limited to the perisylvian network, where the cognitive impairment is caused by epileptic discharges interfering with cognitive development.

Cognition↗

PubMed2005

Factors affecting spiking related to sleep and wake states in temporal lobe epilepsy (TLE).

The aim of the study was to investigate the influence of different clinical factors on spiking during sleep and wakefulness in temporal lobe epilepsy. The study included 38 temporal lobe epilepsy (TLE) patients who underwent long-term electroencephalography (EEG) monitoring. In addition to traditional sleep scoring, waking was subdivided into eyes opened (WEO) and eyes closed (WEC) states. The following spike measures were investigated: spiking rates for each state, mean spike rate, spiking stability across wake and sleep states and relative spike density for each state. These measures were investigated according to clinical variables, such as age, age at epilepsy onset, duration of epilepsy, seizure frequency, the presence of secondarily generalised tonic-clonic (SGTC) seizures and the data on epileptogenic lesions based on MRI. Spiking rates during most states and spiking stability showed a significant positive correlation with epilepsy duration. Relative spike density during sleep stage NREM3,4 significantly increased with age at epilepsy onset. Relative spike density during WEC was significantly higher in the presence of hippocampal sclerosis (HS). Spiking rate during REM was significantly higher if a patient had SGTC seizures. Our data provide evidence that different aspects of spiking are associated with different aspects of TLE. We suggest that spike behaviour analysis offer new aspects both for diagnosis and research.

Adult↗

PubMed2004

Pathological theta oscillations in idiopathic generalised epilepsy.

OBJECTIVE: To investigate spectral power, inter- and intra-hemispheric coherence in the interictal scalp electroencephalography (EEG) of 41 patients with idiopathic generalised epilepsy. METHODS: Two minutes of eyes-closed waking interictal EEG activity was analysed. Fast Fourier transformation was performed. Raw and age-regressed, Z-transformed values were computed for 19 electrodes and 4 frequency bands: absolute power (AP, ZAP), percent power (RP, ZRP), band mean frequency (MF, ZMF), inter-hemispheric (CO, ZCO) and intra-hemispheric (IC, ZIC) coherence. Compressed values (scalp averages) were computed for each parameter and 4 frequency bands. Compressed data of the patients (GE group) and the healthy controls (C group) were compared. RESULTS: ZAP across the entire 1.5-25.0 Hz range was greater in the GE than in the C group. Delta and theta ZRP was greater, alpha ZRP was less in GE than in C. ZMF and ZIC was about the same in the GE and C groups. The crucial, band-specific finding was significantly greater theta-ZCO in the GE group, in contrast to normal or decreased ZCO in the other bands. In addition, within-group correlation between ZAP of the frequency bands, correlation of ZAP and ZCO, correlation of ZIC and ZCO were different for the two groups. CONCLUSIONS: The pattern of enhanced ZAP, ZRP, ZCO, together with normal ZIC and ZMF in the theta range was a peculiar, novel finding in GE. It was incompatible with any of the known patterns of altered power and coherence due to lesional or metabolic aetiology. This pattern presumably indicates the presence of a powerful, diffuse, hypersynchronous, hypercoherent theta oscillation at the thalamo-cortical level of the brain. The role of inter-hemispheric connections in maintaining this oscillation was suggested. The other findings suggest disturbed central regulation of EEG power and coherence in the interictal state.

Adolescent↗

PubMed2004

Abnormal quantitative EEG scores identify patients with complicated idiopathic generalised epilepsy.

OBJECTIVE: To investigate the relationship between quantitative EEG (QEEG) scores and "complicating factors" (psychopathology, true pharmacoresistance, neurological symptoms) in idiopathic generalised epilepsy (IGE). METHODS: 35 newly referred, newly diagnosed, unmedicated IGE patients were collected in a prospective and random manner. Standard neuro-psychiatric and EEG examination was done. The patients were treated and controlled at regular visits. After 2 years of follow-up, clinical data were summarised and were compared to QEEG results. Clinical target items were neurologic and psychiatric abnormalities, proven pharmacoresistance. Patients with at least one of these items were labelled "complicated", whereas patients without these additional handicap were labelled as "uncomplicated". The 12 QEEG target variables were: Z-transformed absolute power values for three (anterior, central, posterior) brain regions and four frequency bands (1.5-3.5; 3.5-7.5; 7.5-12.5; 12.5-25.0 Hz). QEEG scores outside the +/- 2.5 Z range were accepted as abnormal. The overall QEEG result was classified as normal (0-2 abnormal scores), or pathological (3 or more abnormal scores). Clinical and QEEG results were correlated. RESULTS: All patients with psychopathology showed 4-8 positive pathological scores (power excess not confined to a single cortical region or frequency band). The two patients with pure pharmacoresistance showed pathological negative values (delta power deficit) all over the scalp. Statistically significant (P < 0.001) association was found between patients with uncomplicated IGE and normal QEEG, and between complicated IGE and pathological QEEG. Patients with neurological items had normal QEEG. CONCLUSION: Higher degree of cortical dysfunction (as assessed in the clinical setting) is reflected by higher degree of QEEG abnormalities. QEEG analysis can differentiate between IGE patients with or without psychopathology. Forecasting psychopathology may be the practical application of the findings.

Adolescent↗

PubMed2003

[Occipital spectral EEG parameters in newly diagnosed, untreated patients with epilepsy].

INTRODUCTION: Minor spectral EEG alterations hidden to the naked eye may be of interest in the field of epileptology, cognitive performances, and drug effects. In order to introduce new scientific results of brain wave research into the clinical field of epilepsy- and drug-related cognitive problems, a normative quantitative EEG database for epilepsy was constructed. PATIENTS AND METHODS: 171 newly referred, five to 50 years old patients with untreated "new" epilepsy (that is, clinical, EEG, MRI investigations had been done in 24 months after the first unprovoked seizure) were collected. EEG was recorded with closed eyes, in the waking-relaxed state. Effects that are known to influence EEG spectra (nearby seizures, drugs, etc.) were excluded as far as possible. A total of two minutes of waking-resting EEG activity was chosen for spectral analysis. Fast Fourier transformation of the selected samples were calculated resulting in absolute power, percent power and mean alpha frequency (AA, RA, and AMF respectively) for the right and left occipital derivations. For each patient (and also for 37 healthy controls), the deviation of the individual values from the age-adjusted normative mean was expressed in Z-score. Main diagnostic epilepsy categories were compared to the control group as well as to each other. In addition, effects of MRI-defined cerebral lesions and interictal spiking on spectral EEG parameters were investigated. RESULTS: All group averages were within the 95 per cent confidence interval. Overwhelming majority of the individual data fell within a 3Z range. Statistically significant differences were found for AA and RA, but seldom for AMF. Right and left alpha-parameters were surprisingly symmetrical in all groups. The main difference between epilepsy groups and controls was less AA and RA power in the epilepsy groups. MRI-defined lesions and interictal epileptiform activity did not significantly influence EEG spectral variables. CONCLUSION: These results might serve as reference data and might help planning of further quantitative EEG studies in the triangle of epilepsy, cognitive problems, and drug effects.

Adolescent↗

PubMed2003

Interictal epileptic spiking during sleep and wakefulness in mesial temporal lobe epilepsy: a comparative study of scalp and foramen ovale electrodes.

PURPOSE: To assess distribution of temporal lobe spikes across different states of sleep and wakefulness in simultaneous scalp and foramen ovale (Fo) recordings. METHODS: The study included 12 patients with mesial temporal lobe epilepsy (MTLE). As part of their presurgical evaluation, patients underwent long-term video-EEG monitoring with combined scalp and foramen ovale electrodes (FoEs). In addition to traditional sleep scoring, waking was subdivided into eyes-opened and eyes-closed states, and rapid-eye-movement (REM) sleep was divided into phasic and tonic states. Spike counts were carried out visually for scalp and FoEs, and spiking rates were determined for each state. A ratio between FoE and scalp spiking rates also was calculated for each state. RESULTS: Scalp spiking showed a significant increase during NREM3,4, whereas FoE spiking increased during NREM2. The scalp/FoE ratio significantly increased during NREM3,4. A significant difference in spiking rate also was found between phasic and tonic REM states as well as between waking with eyes opened and closed in FoE recordings. CONCLUSIONS: Our data provide evidence of a discrepancy in spike distribution across different states of sleep and waking monitored by scalp and FoE recordings. We suggest that these discrepancies may reflect differences in archicortical and neocortical spike synchronization.

Adult↗

PubMed2002

[Effect of flumazenil on the regional cerebral blood flow measured by [15O]-butanol PET scan and transcranial Doppler ultrasonography].

The authors investigated the role of the cBZD/GABA-A receptor-complex in the regulation of rCBF by simultaneously applying [15O]-butanol-PET and TCD in therapy-resistant TLE patients. It is known that the density of the cBZD/GABA-A-receptors is reduced in the epileptogenic area of the temporal lobe, but there are no data available about the impact of this phenomenon on rCBF. FMZ is a well-known BZD-receptor antagonist which can be used to inhibit the effect mediated by cBZD/GABA-A-receptors, offering a way to study the contribution of these receptors in the determination of rCBF. The authors examined the possible correlation between the rCBF values obtained by PET and the blood flow speed readings measured by TCD in MCAs. The results show that FMZ does not cause any change in rCBF on the side of the epileptogenic focus but it significantly raises rCBF (p < 0.001) in the intact brain tissue on the other side. The TCD measurements showed no significant differences between the blood flow in the MCAs supplying the affected and the contralateral lobe.

Adult↗

PubMed2002

Ictal electroencephalography in a case of benign centrotemporal epilepsy.

The purpose of this research was to publish a complete ictal electroencephalographic (EEG) record of a child with benign centrotemporal epilepsy. The record includes a brief description of the patient's epilepsy syndrome, analysis of interictal and ictal EEG records, and a description of corresponding clinical ictal events. Ictal EEG activity appeared over the right rolandic cortex and spread to adjacent sites. Initial rhythmic activity was followed by bilateral series of sharply contoured slow waves. The electric field of the seizure discharge changed during the seizure. Tangentially oriented dipolar field was found in the middle part of the seizure. Evolution of clinical seizure phenomena roughly corresponded to propagation of the ictal discharge. In terms of topography and electromorphology, this ictal record was similar but not completely identical with those reported previously. Collection of further ictal records in benign rolandic or centrotemporal epilepsy of childhood and other epilepsy syndromes is necessary.

Child↗