Biomedical subjects

Péter Halász

Publications and source records attributed to Péter Halász.

At least 19 recordsLinked to original sources

PubMed2006

[Sudden death and mortality in epilepsy].

Mortality in epilepsy is 2-3 times higher than in the age- and sex-matched general population. It is the highest in young male epilepsy patients with generalised tonic-clonic seizures living in low socio-economical situation. The main factors of early mortality unrelated to seizures are the neurological conditions underlying epilepsy. Suicide is an important factor first of all in temporal lobe epilepsy. The group of mortality directly related to epilepsy is made up of the high-mortality grand mal status epilepticus rarely seen in treated epilepsy; the accidents related to seizures and sudden unexpected death (SUDEP). The reasons directly related to epilepsy make up about 40 per cent of epilepsy mortality. There is a 20-24-fold increase of the risk of sudden death in epilepsy compared to sudden death in the general population. The main risk of SUDEP is the "severity" of epilepsy signaled by generalized tonic-clonic seizures, resistance to antiepileptic drugs, polytherapy and frequent drug-modifications in adulthood epilepsy. Seizure-dependent autonomic changes as cardiac rhythm and breathing disturbances as well as some antiepileptic drugs and treatment modifications may contribute to the development of SUDEP. The data suggest that the main tools helping to decrease mortality in epilepsy nowadays are as follows: optimal seizure control, effective treatment of concomitant psychiatric conditions and monitoring for potentially dangerous heart dysrhythmias as well as respiration disorders.

Anticonvulsants↗

PubMed2006

[Temporal lobe epilepsy--state of art review].

The temporal lobe epilepsy (TLE) is the most important kind of partial epilepsy both from practical and research point of view, where studies brought many new results in the last years. This article is a state of art review with a special emphasis on medial temporal lobe epilepsy (MTLE). We show the clinical symptoms, EEG and neuroimaging signs, the psychiatric co-morbidities and psyhosocial consequences. Etiological factors, among them hippocampal sclerosis and hippocampal reorganisation is assessed in a more detailed form. The possibilities of pharmacological and surgical treatment are also shown, together with the brief outline of the Hungarian situation. TLE is presented as a model for the development of partial epilepsies.

Anterior Temporal Lobectomy↗

PubMed2006

[Predictive factors for the results of surgical treatment in temporal lobe epilepsy].

The most effective type of epilepsy surgery in adults is temporal lobe epilepsy (TLE) surgery. Three quarter of the patients become seizure free, however the remaining patients experience seizures after resection. In our study we analyzed retrospectively the possible electro-clinical, neuroimaging and surgery-related outcome predictors in 94 adult patients who had anterior temporal lobectomy (ATL) from the material of Epilepsy Centre of the National Institute of Psychiatry and Neurology, Budapest since the beginning of the surgery program in 1989 until 2001. Three outcome endpoints were chosen: the seizure status at the last visit, the longest seizure free period and the time to the first non-acute postoperative seizure. The predictors were assessed by multivariate and Cox regression methods. After one year of surgery 72% of the patients were seizure free, after two years 67% and after five years 59%. Factors predicting favorable outcome in TLE surgery were: typical temporomesial aura, strictly unilateral interictal anterotemporal spikes, unilateral ictal onset, slow contralateral propagation, hippocampal sclerosis (HS) as etiology. Factors predicting poor outcome in TLE surgery were: increase in seizure frequency in the last two preoperative years, presence of preoperative psychiatric disturbances, ictal contralateral propagation, MRI lesion distant from the surgery site, incongruency of data of preoperative investigations, postoperative sequels and non-HS type MR residuum.

Adolescent↗

PubMed2006

[The role of micro-arousals in the regulation of sleep].

This work give a short account about a three decades research of the sleep microstructure. The studies, executed by the Strassbourg, Budapest and Parma schools, paved the way of exploring the participation of micro-arousals in the sleep regulation. It was shown that micro-arousals, not leading to instant arousal but influencing the later course of sleep are weaved into the network of sleep. A certain class of micro-arousals differs from the traditional desyncronisation-type and in a paradox way result a rebound like mobilisation of sleep-like activity with deltas and K-complexes. The desynchronisation- and synchronisation-type micro-arousals show different distribution along the sleep cyclicity and may play different role in sleep regulation. On the basis of the studies dealing with micro-arousals we can assume that beside the traditional long time constant, brain stem driven tonic chemical regulation, an other phasic regulation, with shorter time constant, associated with the micro-arousals, also exists. This kind of phasic regulation makes sleep flexible and possible to adapt the actual sleep course to the inner and outer demands. An other important role of micro-arousals in pathological sleeps is to provide a gate for the different pathological events, pinpointing the key-points where these events could be expected in the sleep process.

Arousal↗

PubMed2006

[Executive dysfunction in frontal lesions and frontal epilepsy].

BACKGROUND: To explore the functions of the frontal lobe that are associated with high order cognitive and behavioral aspects such as the organization and execution of thoughts and behavior by neuropsychological methods is difficult. These so called executive functions are in close connection with the prefrontal thalamocortical circuits, damage of which can cause deficits in cognitive functions and even changes in personality. METHODS: The aim of this study is to present a neuropsychological battery for testing frontal lobe functions. 31 patients (with frontal epilepsy and/or frontal lesion) and 38 healthy control subjects participated in the study. The control subjects were matched to the patient group in age, gender and education. RESULTS: Comparing to the controls the patient group showed significant deficits in most of the measured executive functions, except two tests which show that the short time selective attention is preserved. We divided the patient group into three subgroups (frontal epilepsy only FLE, frontal lesion only FL, frontal lesion and epilepsy FLE+FL) and we found that except working memory deficits and problems in inhibition, there were no difference between the FLE patients and the control group. We found most frequently perseveration and errors in a strategy making task among the FL (mainly medial) patients. We didn't find any difference in these tests according to the lateralization of the lesion. CONCLUSION: In conclusion we found that working memory deficits and problems in inhibition differentiated the frontal patient group from the controls in all cases. We emphasize that in frontal epilepsy (with no reported MR lesion) there are the same type, however more limited neuropsychological alterations as in lesional frontal dysfunction.

Adult↗

PubMed2006

Thalamic lesion and epilepsy with generalized seizures, ESES and spike-wave paroxysms--report of three cases.

We report three patients, who have thalamic lesion and secondary generalized epilepsy with generalized spike wave pattern. The first two patients have unilateral perinatal lesion, one with generalized tonic-clonic seizures on awakening the other with Landau-Kleffner-like syndrome. During the course of the disease both children developed electrical status epilepticus in slow wave sleep (ESES). The third patient has a dominantly unilateral thalamic tumor and epilepsy that mimics juvenile myoclonic epilepsy. All the patients have a lesion located in the inferior-medial-posterior part of the thalamus. The role of some thalamic and subthalamic nuclei in the generalized spike-wave electrical pattern patophysiology is discussed, with emphasis on the possible role of the inhibitory system from the zona incerta.

Adult↗

PubMed2006

Twenty-four hours retention of visuospatial memory correlates with the number of parietal sleep spindles.

Recent evidence suggests that the sleep-dependent consolidation of declarative memories relies on the non-rapid eye movement (NREM) rather than the rapid eye movement (REM) phase of sleep. Moreover, a few studies both at the cellular and the behavioural levels have suggested the involvement of sleep spindles, the most synchronous oscillatory waveforms during NREM sleep stage 2, in this process. Our previous study showed that overnight verbal memory retention correlates with the total number of sleep spindles in left frontocentral areas, while spindling in other regions did not correlate with mnemonic retention. In the present study, we show that retention of visuospatial memories over a 24-h period correlates with the total number of sleep spindles detected over parietal regions during the intervening night-time sleep. This result provides further evidence for the association between sleep spindle activity and declarative memory consolidation, and suggests that visuospatial and verbal memory retention differ in the topographic distribution of the NREM spindle activity with which they are associated.

Adult↗

PubMed2005

Long-term outcome after temporal lobe surgery--prediction of late worsening of seizure control.

We analyzed possible predictors of late worsening of seizure control in 94 adult patients who had anterior temporal lobectomy (ATL) from the Epilepsy Center of the National Institute of Psychiatry and Neurology, Budapest between 1985 and 2001. We evaluated data regarding epilepsy, presurgical evaluation, pre- and postoperative EEG, structural imaging, histology and operative complications. The mean follow-up was 6.1 years (range: 2-17 years). The outcome was measured as Engel class, the time to the first seizure and the longest seizure free period. Multiple regression analysis was used to assess predictors. Seizure free outcome was achieved in 72% of the patients 1-year after surgery. Eighty-seven percent of them remained seizure free at the second year of follow-up, 74% at the fifth, and 67% at the tenth year of follow-up. After 2 years of follow-up improvement was present in 3%, worsening in 18% of the patients. Factors associated with long-term worsening were: postoperative ipsilateral EEG spikes over the resected side, preoperative bilateral interictal discharges, cortical dysplasia of Taylor's type, and ictal contralateral propagation. In these patients, even in seizure free state, therapy reduction might be inappropriate.

Adolescent↗

PubMed2005

[Somnambulism: clinical and eletrophysiological aspects].

The authors review the literature on the epidemiology, the clinical and electrophysiological symptoms of somnambulism. The disorder specified as "nREM parasomnia with awakening disorder" belongs to the nREM sleep (awakening) parasomnias. In most of the cases its occurence is familial with the highest prevalence at age 12 year. Above age 12 year most cases recover whereas 6% of prevalence is reported in adults. It is probable that most patients seek medical help only in severe cases associated with injuries, accidents or violence. Its etiology is unknown; in essence it is a sleep regulation disorder characterised by a dissociated state of partial awakening from nREM sleep: the motor system becomes awake while consciousness remains clouded. There are several medicines inducing somnambulism in patients otherwise free from this disorder. In somnambule patients the most important provoking factors are sleep deprivation as well as pathological states and circumstances evoking sleep loss. Somnambulism should be differentiated from complex partial epileptic seizures and REM behaviour disorder. As there is no specific treatment at the moment it is important to assure safe sleeping circumstances - ground flour, closed windows, and no fragile furniture. Clonazepam and selective serotonin reuptake inhibitors prove sometimes effective, but the most effective methods in decreasing the frequency of somnambule episodes are the regular sleep-wakefulness schedule and the avoidance of sleep deprivation.

Diagnosis, Differential↗

PubMed2005

[Supplementary sensory-motor seizures--symptomatology, etiology, and surgical management with illustrative case reports].

In the past decade, owing to the advance of epilepsy surgery, growing knowledge has accumulated on the role of the supplementary motor area, described by Penfield and coworkers in the early fifties, in movement regulation and on the characteristics of seizures involving this area. In the Hungarian neurological literature this topic--despite its neurophysiological and practical clinical importance--has been hardly touched. The authors, based on their own experience obtained from surgeries performed within the framework of the "Co-operative Epilepsy Surgery Program", describe the electrophysiological features of this area, its role in movement regulation and the symptoms of epileptic seizures stemmed from or spread onto this area. Using cases as illustrations, they demonstrate the reasoning and various algorithms of the multidisciplinary examination necessary to explore the seizure onset zone and the pathways of seizure spread. Details of the surgical solution are also described.

Adolescent↗

PubMed2005

Human parahippocampal activity: non-REM and REM elements in wake-sleep transition.

The covert-rapid-eye-movement (REM) sleep hypothesis of dreaming suggests that elements of REM sleep emerge during sleep onset, leading to vivid hypnagogic imagery. Based on parahippocampal electrocorticography of epileptic patients we found an increase in REM-like 1.5-3.0 Hz parahippocampal activity during wake-sleep transition, which peaks after on average 30s of sleep onset, and reaches 82% of REM sleep value. The increase in 1.5-3.0 Hz parahippocampal activity followed alpha dropout, but did not relate to short-term fluctuations in alpha waves or sleep spindles. Non-REM sleep-specific slow (<1.25 Hz) activity showed a continuous increase during wake-sleep transition in both temporal scalp and parahippocampal recordings. It is suggested that REM-like parahippocampal rhythmic slow activity is an after-effect of hypothalamic wake-promoting centers' switch-off at sleep onset, leading to an inhibited hippocampal functioning and hypnagogic hallucinations.

Cortical Synchronization↗

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↗

PubMed2005

K-complex, a reactive EEG graphoelement of NREM sleep: an old chap in a new garment.

This review summarises data gathered on the KC phenomenon over the past 70 yr. The following issues are discussed: definitions, morphology and topography of KC, the regular participation in NREM sleep, elicitability features of evoked KC, autonomic and motor concomitants, relationship of KC with information processing during NREM sleep, relationship of KC and deltas of NREM sleep, and relationship of KC with sleep cyclicity. KC is a complex multifunctional phenomenon of the sleeping brain involved in information processing and defence against the arousal effect of sensory stimuli. To put the old chap in a new garment, the relationship of KC with synchronisation-type and desynchronisation-type micro-arousals, and the 'cyclic alternating pattern', will be discussed, with an emphasis on the sleep-protecting role of KC and synchronisation-type answers in sleep regulation executed by phasic events. Lastly, the role of KC providing gating functions in idiopathic generalized epilepsies and other, different, sleep disorders are characterised. A 'theoretical epilogue' is appended to show some system theoretical and regulational aspects.

Arousal↗

PubMed2005

Prediction of general mental ability based on neural oscillation measures of sleep.

The usual assessment of general mental ability (or intelligence) is based on performance attained in reasoning and problem-solving tasks. Differences in general mental ability have been associated with event-related neural activity patterns of the wakeful working brain or physical, chemical and electrical brain features measured during wakeful resting conditions. Recent evidences suggest that specific sleep electroencephalogram oscillations are related to wakeful cognitive performances. Our aim is to reveal the relationship between non-rapid eye movement sleep-specific oscillations (the slow oscillation, delta activity, slow and fast sleep spindle density, the grouping of slow and fast sleep spindles) and general mental ability assessed by the Raven Progressive Matrices Test (RPMT). The grouping of fast sleep spindles by the cortical slow oscillation in the left frontopolar derivation (Fp1) as well as the density of fast sleep spindles over the right frontal area (Fp2, F4), correlated positively with general mental ability. Data from those selected electrodes that showed the high correlations with general mental ability explained almost 70% of interindividual variance in RPMT scores. Results suggest that individual differences in general mental ability are reflected in fast sleep spindle-related oscillatory activity measured over the frontal cortex.

Adult↗

PubMed2004

[Genetic background of epilepsies].

In this article we review epilepsies with monogenic inheritance. Most of these diseases are caused by abnormal function of ligand- and voltage gated ion channels caused by a genetic defect, therefore belonging to the channelopathies. From the inherited epilepsies the genetics of the autosomal dominant partial epilepsies is clarified the best. Mutations of the nicotinic acetylcholine receptor subunits are found in familial nocturnal frontal lobe epilepsy, while defects in the voltage gated potassium channels (KCNQ2 and KCNQ3) have been identified in benign familial neonatal convulsions. Familial temporolateral epilepsy was associated with mutations of a tumor suppressor gene. From the generalized epilepsies, the syndrome of generalized epilepsy with febrile seizures plus (GEFS+) can be caused by mutations of the sodium channel subunits and of the GABAA receptor subunits. These important results would probably lead to new findings in the genetics of the more common forms of idiopathic generalized epilepsies, which have presumed polygenic origin. Although without definite conclusions, sodium channel and GABA receptor dysfunction is presumed. The accumulated knowledge about channelopathies enables insight to the cellular mechanism of epileptogenesis as well.

Chromosomes, Human, X↗

PubMed2004

[Surgical treatment of epilepsy].

In this article the possibilities, indications, methods and results of surgery in epilepsy are summarized in general with the Hungarian experience emphasized. Surgery may provide effective treatment in about 5-10% of the epileptic population. Surgical solution nowadays became an essential treatment in medial temporal epilepsy, if hippocampal sclerosis or other lesion is present, in therapy resistant lesional extratemporal epilepsies and in catastrophic childhood epilepsies if the epileptic disorder is restricted to one hemisphere (Rasmussen syndrome, hemimegalencephaly, Sturge-Weber disease and posttraumatic or postencephalitic hemispherial epilepsies). The algorithms of the presurgical evaluation and the current methods for study the pacemaker area, forbidden zones, and hemispherial functions are treated. The currently used type and techniques of surgery, such as lesionectomy, temporal lobe resections, hemispherotomy, callosotomy, multiple subpial transsections and their indications are described. The newest surgical approaches, as deep brain stimulation, vagal nerve stimulation, and irradiation techniques are also briefly touched. Lastly, we deal with prognostical factors of the surgical outcome, reasons of surgical failures and complications. In a brief chapter the importance of postsurgical rehabilitation is emphasized.

Algorithms↗

PubMed2004

Epilepsy caused by retrosplenial tumor.

We present a patient in whom retrosplenial tumour was associated with epileptic symptoms characterized by complex partial seizures and widespread interictal and ictal epileptiform EEG abnormalities. The patient had verbal memory deficit symptoms as well. After surgical removal of the tumour (oligoastrocytome) the clinical symptoms and EEG signs disappeared. The characteristics of our patient demonstrate the possible role of the retrosplenial area in widespread epileptic symptoms and in the regulation of secondary bilateral synchrony, in addition to its recently described importance in the memory functions.

Adult↗