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Biomedical subjects

M Brázdil

Publications and source records attributed to M Brázdil.

14 recordsLinked to original sources
PubMed2006

Long-term levetiracetam treatment of epilepsy patients: clinical audit.

PURPOSE: The long-term efficacy and tolerability of levetiracetam (LEV) was analysed in 218 epilepsy patients. One hundred and ninety-nine patients were treated for at least 6 months. We evaluated LEV efficacy for all types of seizures together, and for simple partial, complex partial and secondary generalized seizures individually. RESULTS: A significant decrease in the number of seizures occurred after 6 months of treatment (p<0.001). Mean seizure frequency (irrespective of type) before LEV was 19.2 a month. The mean monthly frequency at 6, 12, 24 and 36 months dropped to 12.7, 10.5, 9.7 and 7.1 seizures a month, respectively. The mean percentage reduction in seizures at these times was 45.7, 52.1, 59.1 and 64.2% and the number of responding patients was 51.3, 54.2, 59.8 and 62.2%. The number of patients completely seizure free was 18.6, 16.7, 15.2 and 16.2%. We found similar results in the last three categories for partial simple, complex and secondary generalized seizures individually. Side effects in 18.3% of patients caused treatment discontinuation in 6.4%. The most frequent were somnolence, moodiness and dizziness. The retention rate at 6, 12, 24 and 36 months was 0.848, 0.72, 0.62 and 0.5, respectively. CONCLUSIONS: LEV is effective and well tolerated for long-term treatment of epilepsy.

Anticonvulsants↗
PubMed2006

An event-related fMRI study of self-paced alphabetically ordered writing of single letters.

The spatial location of activation for writing individual letters and for writing simple dots was studied using event-related functional MRI. Ten healthy right-handed subjects were scanned while performing two different protocols with self-paced repetitive movement. In the first protocol with self-paced dot writing, we observed significant activation in regions known to participate in motor control: contralateral to the movement in the primary sensorimotor and supramarginal cortices, the supplementary motor area (SMA) with the underlying cingulate, in the thalamus and, to a lesser extent, in the ipsilateral inferior parietal and occipital cortices. In the second protocol, we investigated an elemental writing feature--writing single letters. We observed statistically significant changes in the premotor, sensorimotor and supramarginal cortices, the SMA and the thalamus with left predominance, and in the bilateral premotor and inferior/superior parietal cortices. The parietal region that was active during the writing of single letters spanned the border between the parietal superior and inferior lobuli Brodmann area (BA 2, 40), deep in the intraparietal sulcus, with a surprising right-sided dominance. The direct comparison of the results of the two protocols was not significant with a confidence level of P<0.05 corrected for whole brain volume. Thus, the ROI approach was used, and we tried to find significant differences within the two predefined regions of interest (ROI) (BA 7, BA 37). The differences were found with a confidence level of P<0.05 corrected for the volume of these predicted areas. The ROI were located in the posterior parts of hemispheres, in the ventral and in the dorsal visual pathway. The right-sided posterior cortices may play a role in the elemental mechanisms of writing. It is possible that activation of this region is linked with the spatial dimension of the writing.

Adult↗
PubMed2005

Reorganization of language-related neuronal networks in patients with left temporal lobe epilepsy - an fMRI study.

To investigate the inter- and intrahemispheric reorganization of the language cortex in left temporal lobe epilepsy (TLE) with left-sided hippocampal sclerosis. A functional magnetic resonance imaging was performed on 13 right-handed patients suffering from medically intractable left TLE, and in 13 sex- and age-matched healthy controls. The activation paradigm used was a silent word generation task. A language laterality index (LI) was calculated from the number of activated voxels in the right and left anterior two-thirds of the hemispheres. Significant differences between the patients and the controls were observed in the activation of the left-sided inferior frontal gyrus. Less consistent findings in this region, as well as the relative protection of Broca's area from the activation, were revealed in the patients. In addition, different patterns of activation were proven in the cerebellum and other cortical as well as subcortical brain structures within both hemispheres. Significant differences were also found in the values of the language LIs between the investigated groups: these values suggested a more bihemispheric language representation in the patients. As anticipated, lateralization of the language functions in the epileptics significantly decreased in connection with an earlier age of initial insult. Our results support the hypothesis of a significant intra- and interhemispheric functional reorganization of language-related neuronal networks in left TLE.

Adult↗
PubMed2005

Lateralized ictal immobility of the upper limb in patients with temporal lobe epilepsy.

The primary aim of this study was to establish the incidence and the lateralizing value of 'lateralized ictal immobility of the upper limb' (LIL) in patients suffering from temporal lobe epilepsy (TLE), and to describe the connection between LIL and other clinical ictal signs. We retrospectively reviewed video records of 87 patients with TLE. We reviewed a total of 276 focal epileptic seizures with or without secondary generalization. We studied the incidence of LIL, its lateralizing value, and its relationship to other ictal clinical signs. Of the 87 patients, 49 had undergone a successful resective surgery at least 1 year prior to the study. LIL is a late sign in the course of partial seizure. It occurred in 25 of our 87 patients (28.7%), and in 47 of 276 seizures (17.1%). In all of the evaluated seizures, LIL occurred contralateral to the side of seizure onset (P < 0.001). LIL was always associated with ipsilateral upper limb automatisms, and in 63.1% of the occurrences, it was immediately followed by ictal dystonia. LIL is a more accurate term to describe what has previously been called 'ictal paresis' in the literature. Due to the inability to execute proper testing during a partial seizure, it is better to use the term LIL when making a visual analysis of a seizure. LIL is a more suitable term to describe the studied ictal sign. It is a relatively frequent sign in patients with TLE. LIL has an excellent lateralizing value for the contralateral hemisphere. It is a negative motor sign, and its genesis is probably associated with the epileptic involvement of the contralateral frontal lobe.

Adolescent↗
PubMed2003

A SEEG study of ERP in motor and premotor cortices and in the basal ganglia.

OBJECTIVE: Our intention was to study the electrical activity related to the cognitive processing of simple sensory stimuli in the brain structures that participate in motor control. We focused our interest on the 250-600 ms time window, in which cognitive activity most probably provides the basis for the activity recorded. METHODS: Intracerebral stereoelectroencephalography (SEEG) recordings were made from 15 epilepsy surgery candidates. We studied potentials that were recorded in a time window in which P300 usually could be recorded on the scalp and that were directly recorded from brain structures involved in motor control: the primary motor cortex (MC, Brodmann's area 4); the lateral and mesial (SMA) premotor cortices (Brodmann's area 6); and the basal ganglia. We evaluated the first distinctive potential to occur in the 250-600 ms time window that displayed an amplitude gradient in several adjacent contacts. Four protocols were performed: an auditory oddball (aP3); a visual oddball (vP3); and contingent negative variation (CNV) protocols, in which the potentials evoked by the auditory warning (aCNV) and visual imperative (vCNV) stimuli were evaluated. In the protocols aP3, vP3, and vCNV, the tested person responded by flexing his/her thumb or hand. In the aCNV paradigm, and in a further auditory oddball paradigm (aP3c), no motor response was required. We compared the presence of an event-related potential (ERP) with an amplitude gradient to the absence of a generator. RESULTS: The frequency of P3-like potential components was statistically significantly higher in the basal ganglia when compared with the explored cortical sites. Statistically non-significant latency differences between the basal ganglia and the cortex were displayed. The differences in the distribution of the potentials in the individual cortical areas were insignificant. The mean latency of vP3 was longer than the latencies of aP3, aP3c and vCNV. There was no significant difference between the distribution and latency of aP3 and aP3c. CONCLUSIONS: (1) ERPs are generated in cortical as well as in subcortical structures. (2) The cognitive processing of sensory information in all the tested protocols occurred in the basal ganglia; the occurrence in the investigated cortical areas was less frequent and more dependent on the task. The basal ganglia may play an integrative role in cognitive information processing, in motor and non-motor tasks.

Adolescent↗
PubMed2003

Identical event-related potentials to target and frequent stimuli of visual oddball task recorded by intracerebral electrodes.

OBJECTIVE: The shape of visually elicited event-related potentials (ERP) of epileptic patients during their presurgical evaluation with intracerebral electrodes was investigated in the study. METHODS: Twenty intractable epileptic patients with depth electrodes at several intracranial locations in the frontal, temporal, parietal lobes, and in the amygdalo-hippocampal complex participated in the study. To evoke the ERP, a standard visual oddball task was used with target stimuli, and frequent non-habituated and habituated stimuli. The averaged responses of the 3 groups were superimposed and visually analyzed whether the shape appeared identical or non-identical. RESULTS: The EEG response to target and frequent stimuli was recorded in 660 intra-cerebral sites. In 88 sites (14 different patients) localized in the amygdala, parahippocampal gyrus, superior, middle, and inferior temporal gyri, fusiform and lingual gyri, sensorimotor cortex, prefrontal cortex, hippocampus, and cingulated gyrus, the identical ERPs to target and both groups of frequent stimuli were observed. In 442 sites located in the above listed structures, and in the basal ganglia and parietal cortex, the shape of the ERP differed from 0.3 to 0.47 s on after the stimulus. The remaining 130 sites did not yield the task-specific potential change. CONCLUSIONS: The existence of identical ERPs to target and frequent stimuli in the oddball task suggests that a part of mental operations underlying the brain engagement in this task is not dependent on the way of responding.

Adult↗
PubMed2003

Effect of vagal nerve stimulation on patients with bitemporal epilepsy.

Patients with bitemporal epilepsy are characterized by the existence of independent bitemporal seizure onset zones. The aim of this study was to evaluate the effect of chronic vagal nerve stimulation (VNS) on eight patients with bitemporal epilepsy. We demonstrated the gradually increased effect of VNS on the reduction of seizures as compared with baseline seizure frequency in patients with bitemporal epilepsy. The average seizure reduction increased from 4.2% at the 3-month follow-up visit to 18.2, 34.4 and 42.2% at the 6, 12 and 18-month follow-up visits. Similarly, a >or=50% reduction of complex partial seizures was reported at the 3-month follow-up visit in no patients (0%); at the 6-month follow-up visit in one patient (12.5%); at the 12-month follow-up visit in three patients (37.5%); and at the 18-month follow-up visit in five patients (62.5%). These data demonstrate the positive and long-lasting effect of VNS on seizure reduction in patients with intractable bitemporal epilepsy. The main mechanism of this chronic effect is not fully understood.

Adult↗
PubMed2003

Ictal limb dystonia in temporal lobe epilepsy. an invasive video-EEG finding.

The aim of the investigation was to evaluate the ictal EEG in the putamen and the temporal and frontal lobes during contralateral ictal limb dystonia (ID). Ten epilepsy surgery candidates participated in the study. All of them were investigated using intracerebral and/or subdural electrodes. In four of the patients, the putamen was investigated with diagonal depth electrodes (patients 1-4), in six of the patients, both the temporal and frontal lobes were investigated (patients 5-10). All of the investigated contacts were located contralateral to the side of the ictal dystonia. All of the patients suffered from temporal lobe epilepsy (TLE); in patient 10, both temporal and frontal seizure types were recorded. A total of 20 complex partial seizures (CPS) were analysed. ID was never an early symptom in the course of CPS. Slow activity was recorded in the putamen in all 10 seizures of the four patients in whom the putamen was investigated (patients 1-4). In five of these seizures, there was a time-locked change in the ictal EEG in relation to the ID (slowing of activity in three seizures; acceleration in two seizures). At the time of the onset of ID, several cortical regions were involved in the ictal discharge, within both the contralateral temporal and frontal lobes. In all 10 seizures of the six patients in whom both the temporal and frontal lobes on the contralateral side were evaluated (patients 5-10), the ictal paroxysmal discharge was noted in both lobes (i.e. frontal and temporal) at the time of ID onset. We can conclude that ID is a late symptom in TLE. Widespread activation of the contralateral temporal and frontal lobes is needed for the appearance of ID; however, the critical region responsible for the genesis of ID was not revealed. Although there are some non-specific changes in the putamen contralateral to ID, the changes were never epileptic in type. The putamen probably collaborates in the genesis of ID, but it does not generate the epileptic discharge during its course.

Adult↗
PubMed2001

Intracerebral event-related potentials to subthreshold target stimuli.

OBJECTIVES: Event-related potentials (ERPs) elicited by subthreshold visual stimuli were recorded directly from human frontal and temporal lobe structures to study unconscious perception. METHODS: Thirteen intractable epileptic patients undergoing depth electrode recordings prior to their surgical treatment participated in the study. An original method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied, and the averaged responses to both kinds of stimuli were subsequently compared. RESULTS: The results clearly prove that, at least from an electrophysiological viewpoint, the mechanism of unaware processing of visual stimuli in the human brain does not differ substantially from the aware processing. Finding the subliminal P3 waveform in a number of cortical structures (hippocampus and parahippocampal gyrus bilaterally, and left-sided mesiofrontal, orbitofrontal and lateral temporal cortex) indicates their involvement in unconscious processing, in spite of the fact that typical large-scale neurocognitive networks are not completely activated. The absence of activation consistently observed bilaterally in dorsolateral prefrontal cortices, in connection with right-sided cortical frontal lobe structures and right-sided lateral temporal neocortex in unconscious perception, supports the importance of these structures for the awareness of visual stimuli. The proof of the significantly faster unaware information processing represents another distinctive feature of implicit visual perception. CONCLUSIONS: Based on the presented findings and comparisons with the results of previous ERP, functional magnetic resonance imaging, positron emission tomography, and clinical neuropsychological studies, a crucial role of the large-scale neural system for conscious experience of perception is suggested, which is distributed extensively among the dorsal posterior association areas and the prefrontal cortex, with the dominant part being that of the right hemisphere.

Adult↗
PubMed2001

Effect of vagal nerve stimulation on auditory and visual event-related potentials.

Chronic unilateral vagal nerve stimulation (VNS) has been recently introduced into the therapy for intractable epileptic seizures. Its effect on cognitive functions in VNS-treated patients remains controversial. The aim of the present study was to evaluate the possible impact of therapeutic VNS on cognitive functions by means of event-related potentials analysis. Ten patients with medically intractable epilepsy, who had been implanted with VNS devices, participated in the study. Auditory and visual event-related potentials (ERPs) were repeatedly recorded, first just before the implantation of VNS devices, and then again 3-6 months after the device activation. The effect of lower intensity stimulation on the P3 component of ERPs was assessed. No significant differences were found in auditory ERPs; the latencies of P3 as well as N2/P3 peak-to-peak amplitudes were virtually identical. The same was true for mean P3 latencies of visual ERPs. However, higher visual N2/P3 peak-to-peak amplitudes were observed in the responses to targets that followed VNS, with a significant finding at the electrodes investigated. When comparing the effect of VNS on visual N2/P3 amplitude in each electrode separately, the most expressive differences were found in the frontal region. This observation supports the theory of a possible positive effect of low-intensity VNS on the cognitive functions.

Adult↗
PubMed1999

The role of frontal and temporal lobes in visual discrimination task--depth ERP studies.

Visual event-related potentials were simultaneously recorded from different anatomical structures within frontal and temporal lobes in 12 epileptic patients. A simple discrimination task was performed to complement previous studies on the localization of P3 generators in the human brain. The role of multiple cortical structures in the generation of both P3a and P3b components was confirmed. Activities contemporary to a visual P3b were recorded in the hippocampus, amygdala and temporal pole. Anterior cingulate and orbitofrontal cortices-generated activities more closely related in time to the surface P3a. Earlier events related to visual discrimination took place in more lateral sites of the frontal lobe, but their contribution to the scalp P3 remains uncertain. Subsequently, mutual temporal relations among single generators were analyzed. The results suggested a processing-level hierarchy within the neural network for directed attention with a key role played by the dorsolateral prefrontal cortex.

Adult↗
PubMed1998

Effect of subthreshold target stimuli on event-related potentials.

OBJECTIVES: Event-related potentials (ERPs) elicited by subthreshold visual stimuli were studied to assess the relationship between unconscious cognitive processing and the electrical activity of the brain. METHODS: A new method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied. Prior to the experiment, the individual 'subjective' threshold for the conscious discrimination between frequent and target stimuli was established for each subject. Supraliminal and subliminal, frequent and target visual stimuli were then alternatively presented in random order to each subject. RESULTS: Both the individual and the grand average ERPs revealed a typical response (P3) in the parietal region after supraliminally presented target stimuli. In subliminal conditions an analogous positive deflection in the central-parietal region was observed, which was elicited by the target stimulus, but not the frequent stimulus. Its latency could be clearly distinguished from the latency of the classical P3, the time difference between the two waveforms was approximately 100 ms. RESULTS: The results of this study revealed the impact of unconscious processing to target stimuli on the configuration of event-related responses.

Adult↗