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Biomedical subjects

A Ebner

Publications and source records attributed to A Ebner.

At least 19 recordsLinked to original sources
PubMed2001

Lateralizing value of unilateral motor and somatosensory manifestations in frontal lobe seizures.

PURPOSE: To evaluate the lateralizing value of unilateral somatosensory aura, unilateral tonic posturing, head version, non-forced head turning, ictal cloni, dystonic posturing, and postictal nose wiping in seizures originating in the frontal lobe. METHODS: We included patients who had consecutively undergone presurgical evaluation with ictal video-EEG monitoring at our institution, had had resective epilepsy surgery involving the frontal lobe, and had remained seizure-free >1 year after operation. Twenty-seven patients aged 1-42 years (mean 18) met the inclusion criteria. Fifteen patients had right-sided, 12 patients had left-sided epileptogenic regions. Seizures recorded during EEG-video monitoring were re-evaluated by two investigators in order to identify lateralization signs in frontal lobe seizures. One of the investigators was blind to patients' clinical data. RESULTS: We analyzed 153 seizures of 27 patients. The most common unilateral phenomenon was the unilateral tonic posturing occurring in 48% of all the patients and in 25% of all seizures. Somatosensory aura and head version appeared exclusively contralateral whereas clonus occurred in 92% and unilateral tonic posturing in 89% of seizures contralateral to the epileptogenic region. Ictal non-forced head turning and postictal nose wiping showed no lateralizing significance. Dystonic posturing did not occur. CONCLUSIONS: Somatosensory aura, head version, ictal cloni, and tonic posturing are reliable lateralizing signs in frontal seizures. These signs may help in identifying the epileptogenic region during presurgical evaluation of patients suffering from frontal lobe epilepsy.

Adolescent↗
PubMed2001

Lack of aura experience correlates with bitemporal dysfunction in mesial temporal lobe epilepsy.

UNLABELLED: The diagnostic value of lack of aura experience in patients with temporal lobe epilepsy (TLE) is unclear. PURPOSE: To evaluate possible factors of bitemporal dysfunction in patients with mesial TLE who did not experience an aura in electroencephalography EEG/video monitoring for epilepsy surgery. METHODS: Ictal scalp EEG propagation patterns of 347 seizures of 58 patients with mesial temporal lobe sclerosis or non-lesional mesial TLE, interictal epileptiform discharges (IED), presence of unilateral mesial temporal lobe sclerosis in visual magnetic resonance imaging (MRI) analysis, prose memory performance, history or not of an aura, and postictal memory or absence of an aura were analyzed. The ictal EEG was categorized as follows. EEG seizure: (a) remaining regionalized, (b) non-lateralized, (c) showing later switch of lateralization or bitemporal asynchronous ictal patterns. RESULTS: Absent aura in monitoring was significantly correlated with absence of unitemporal MRI sclerosis (P=0.004), bitemporal IED (P=0.008), and propagation of the ictal EEG to the contralateral temporal lobe (P=0.001). Other historical data and interictal prose memory performance were not significantly correlated with absent aura. Ten of 11 patients without aura in monitoring also had absent or rare auras in their history. CONCLUSIONS: Lack of aura experience strongly correlates with indicators of bitemporal dysfunction such as bitemporal interictal sharp waves and bitemporal ictal propagation in scalp EEG, and absence of lateralized MRI sclerosis in patients with mesial TLE. The fact that absent auras are not correlated with episodic memory suggests a transient memory deficit, probably because of rapid propagation to the contralateral mesial temporal lobe.

Adolescent↗
PubMed2001

Transient lesion in the splenium of the corpus callosum: three further cases in epileptic patients and a pathophysiological hypothesis.

OBJECTIVE: Focal lesions limited to the splenium of the corpus callosum (SCC) are rare and little is known about their aetiology. Three patients were examined for presurgical evaluation in epilepsy with a transient lesion in the SCC and a pathophysiological hypothesis is presented. METHODS: Three patients were identified with a circumscribed lesion in the centre of the corpus callosum. Follow up MRI was performed, the medical records examined retrospectively, and the literature reviewed. RESULTS: The patients showed identical lesions in the SCC with reduced T1 and increased T2 signal intensity and an unaffected marginal hemline of a few mm. Patients were asymptomatic and control MRIs showed complete normalisation within 2 months. Patients had been treated with antiepileptic drugs (AEDs) without signs of toxicity. In all patients AEDs were rapidly reduced for diagnostic purposes, but only one had psychomotor seizures, 5 days before imaging. CONCLUSIONS: A transient lesion in the SCC has so far only been described in 13 patients with epilepsy and has been interpreted either as reversible demyelination due to AED toxicity or transient oedema after secondary generalised seizures. The data confirm neither of these hypotheses. A transient lesion in the SCC seems to be a non-specific end point of different disease processes leading to a vasogenic oedema. This suggests, in these patients, a multifactorial pathology triggered by transient effects of AEDs on arginine vasopressin and its function in fluid balance systems in a condition of vitamin deficiency. The complete and rapid reversibility in all cases without specific intervention is emphasised and any invasive diagnostic or therapeutic approach is discouraged.

Adult↗
PubMed2000

Amplitude envelope correlation detects coupling among incoherent brain signals.

Cognitive processing involves gamma-activation over broad cortical regions. Phase coupling of these activities has rarely been reported for areas far apart. Other forms of coupling are generally not detected by conventional measures. Here, we use amplitude envelope correlation (AEC), which can detect signal coupling without phase coherence, even among different frequencies. We apply it to subdural recordings from humans performing a visual delayed match-to-sample task and systematically compare it with spectral amplitude and coherence. The different measures often show divergent results. In particular, AEC reveals y-coupling completely missed by coherence. We argue that coherence and AEC are adapted to different cortical mechanisms of short- and long-range interactions, respectively.

Adult↗
PubMed2000

EEG predicts surgical outcome in lesional frontal lobe epilepsy.

BACKGROUND: Because of the relatively poor results of frontal lobe epilepsy (FLE) surgery, identification of prognostic factors for surgical outcome is of great importance. METHODS: To identify predictive factors for FLE surgery, we analyzed the data of 61 patients (mean age at surgery 19.2) who had undergone presurgical evaluation and resective surgery in the frontal lobe. Postoperative follow-up ranged from 0.5 to 5 years (mean 1.78). Fifty-nine patients had MRI-detectable lesions. Histopathologic examination showed dysplasia (57.4%), tumor (16.4%), or other lesions (26.2%). Thirty postoperatively seizure-free patients were compared with 31 non-seizure-free patients with respect to clinical history, seizure semiology, EEG and neuroimaging data, resected area, and postoperative data including histopathology. RESULTS: Three preoperative and two postoperative variables were related to poor outcome: generalized epileptiform discharges, generalized slowing, use of intracranial electrodes, incomplete resection detected by MRI, and postoperative epileptiform discharges. The only preoperative factor associated with seizure-free outcome was the absence of generalized EEG signs. Multivariate analysis showed that only the absence of generalized EEG signs predicts the outcome independently. Moreover, the occurrence of a somatosensory aura, secondarily generalized seizures, and negative MRI was identified as additional independent risk factors for poor surgical results. CONCLUSIONS: The absence of generalized EEG signs is the most predictive variable for a seizure-free outcome in FLE surgery. Furthermore, nonlesional MRI, somatosensory aura, and secondarily generalized seizures are risk factors for poor surgical results.

Adolescent↗
PubMed2000

[Anatomic substrate of epigastric aura: case report].

Epigastric sensations are the most frequent type of aura in medial temporal lobe epilepsy. Until now, the site of the symptomatogenic zone of the epigastric aura remains controversial. The temporal lobe has been discussed, as well as the insular cortex. The case presented here supports the assumption of an insular origin of the epigastric aura. A 44-year-old male suffered from typical psychomotor seizures preceded by an epigastric aura. Imaging revealed a cavernoma located in the right insular region, the ipsilateral temporal lobe being otherwise unremarkable. The lesion was surgically removed, leaving the temporal lobe untouched. Apart from one clinical episode that was unlike his habitual seizures, the patient remained free of seizures (including auras). We conclude that the insular cortex was most likely the symptomatogenic zone for this patient's epigastric auras. Although it can not be excluded that this patient's aura resulted from ictal activation of other brain structures, the successful lesionectomy is in favor of our hypothesis.

Abdomen↗
PubMed2000

Effects of nifedipine on rhythmic synchronous activity of human neocortical slices.

The antiepileptic effect of the dihydropyridine calcium channel blocker nifedipine was tested in neocortical slice preparations (n=27) from patients ranging in age from four to 46 years (mean=25) who underwent surgery for the treatment of intractable epilepsy. Epileptiform events consisted of spontaneously occurring rhythmic sharp waves as well as of untriggered epileptiform field potentials induced by omission of Mg(2+) from the superfusate, or epileptiform field potentials elicited by application of bicuculline and triggered by single electrical stimuli. (1) Spontaneous rhythmic sharp waves (n=6): with nifedipine (40micromol/l), the repetition rate was decreased down to 30% of initial value, whereas the area under the field potential remained nearly unchanged. (2) Untriggered low Mg(2+) epileptiform field potentials (n=6): with nifedipine (40micromol/l) the area under the field potentials was reduced while the action on the repetition rate was ambiguous. (3) Triggered bicuculline epileptiform field potentials (n=15): with nifedipine (40micromol/l; n=4), no antiepileptic effect was found. There was, however, a marked increase in the area under the epileptiform field potentials. The area under the field potentials was reduced only at a dosage of 60micromol/l (n=11). This effect was stronger when nifedipine was applied with a K(+) concentration raised from 4 to 8mmol/l. The results show that the calcium channel blocker nifedipine is able to reduce differential epileptiform discharges in human neocortical tissue. These observations are in line with previous findings, suggesting that calcium flux into neurons is involved in epileptogenesis. The present results therefore support the idea that some organic calcium antagonists may be useful in human epilepsy therapy, although the etiology of epileptic seizures seems to be a critical factor for the efficacy of the drug.

Adolescent↗
PubMed2000

Temporal lobe epilepsy with sensory aura: interictal glucose hypometabolism.

Patients with mesial temporal lobe epilepsy (mTLE) exhibit marked depressions of the regional cerebral glucose metabolism (rCMRGlu) in the mesiotemporal region. We hypothesised that patients with temporal lobe epilepsy (TLE) who have a bilateral somatosensory or acoustic ( = temporolateral/SII-) aura can be differentiated from mTLE by rCMRGlu depressions primarily involving temporo-perisylvian locations. We therefore used this ictal semiology as a clinical criterion to define a subgroup of such patients and measured the rCMRGlu in 16 patients with TLE as evident from interictal and ictal EEG-video monitoring. Clinically, they presented with medically refractory complex partial seizures and were subjected to presurgical evaluation. The pattern of the interictal rCMRGlu in the TLE patients was different from that observed in patients with mTLE and showed significant depressions ipsilateral to the epileptic focus in mesial temporal and lateral temporal regions but spared the thalamus. The neocortical metabolic depressions were spatially more extended in right than in left TLE patients. Magnetic resonance images (MRI) were either normal (n = 5) or revealed unilateral or bilateral hippocampal atrophy/sclerosis (n = 7), or temporal or extratemporal focal cortical dysplasia (n = 4). The selected TLE patients presented here comprise a heterogeneous group showing most pronounced metabolic depressions in the lateral temporal cortex. Thus, our data suggest that non-invasive metabolic imaging can assist in identifying the neocortical symptomatogenic zone in putative temporo-perisylvian lobe epilepsy.

Abdomen↗
PubMed2000

Interictal EEG and ictal scalp EEG propagation are highly predictive of surgical outcome in mesial temporal lobe epilepsy.

PURPOSE: Surgical outcome in patients with mesial temporal lobe sclerosis (MTS) is worse than that in patients with temporal lobe activity (TLE) with tumors. Previous studies of the ictal EEG focused on ictal EEG onset in scalp EEG or ictal EEG propagation in invasive recordings. Ictal EEG propagation with scalp electrodes has not been reported. METHODS: Ictal scalp EEG propagation patterns were studied in 347 seizures of 58 patients with MTS or nonlesional TLE. Interictal epileptiform discharges (IEDs) and the presence of unilateral mesial temporal lobe atrophy in magnetic resonance imaging (MRI) also were studied in these 58 patients. Forty-nine patients were operated on (minimal follow-up of 1 year). RESULTS: Postoperatively, seizure-free outcome was seen in (a) 82.8% of patients with regionalized EEG seizure without contralateral propagation, but in only 45.5% of patients with contralateral propagation (p = 0.007); (b) 84.6% of patients with 100% IED lateralized to one temporal lobe, but in only 52.2% with <100% unitemporal IED (p = 0.015); (c) 88.9% with 100% unitemporal IED and regionalized ictal EEG combined, 73.7% with one of both variables, and only 33.3% with <100% ipsitemporal IED combined with contralateral ictal EEG propagation (p = 0.007). CONCLUSIONS: Switch of lateralization or bitemporal asynchrony in the ictal scalp EEG and bitemporal IED are most probably an index of bitemporal epileptogenicity in MTS and are associated with a worse outcome.

Adolescent↗
PubMed2000

Are ictal vocalisations related to the lateralisation of frontal lobe epilepsy?

The purpose was to analyse whether non-speech vocalisations in seizures originating in the frontal lobe do have lateralising value. Patients were included who had undergone presurgical evaluation with ictal video-EEG monitoring at the Epilepsy Centre, had had resective epilepsy surgery involving the frontal lobe, and who had remained seizure free>1 year postoperatively. Twenty seven patients aged 1-42 years (mean 18) met the inclusion criteria. Age at epilepsy onset ranged from 1 month to 41 years (mean 7.1 years). All selected patients had a unilateral MRI detected lesion within the frontal lobe. Fifteen patients had right sided, 12 patients had left sided epileptogenic zones. Seizures recorded during EEG-video monitoring were re-evaluated to identify the occurrence of ictal vocalisations. Pure ictal vocalisations were distinguished from ictal sound productions due to motor or vegetative seizure activity (for example, cloni or respiratory sounds). Pure ictal vocalisation occurred in 11 patients of whom nine had a left frontal epileptogenic zone (p<0.01). It is concluded that ictal vocalisation could be an additional lateralising sign in frontal lobe epilepsy. The results suggest that not only speech, but vocalisation at a subverbal level also shows a left hemispheric dominance in humans.

Adolescent↗
PubMed2000

Optical monitoring of neuronal activity during spontaneous sharp waves in chronically epileptic human neocortical tissue.

Functional changes in neuronal circuitry reflected in spontaneously occurring synchronous sharp field potentials (SSFP) have been reported to occur in human brain suffering from chronic epileptogenicity but not in primary nonepileptic tissue from peritumoral resectates. Voltage sensitive dyes and fast imaging were used to visualize spontaneously occurring rhythmic depolarizations correlated to SSFP in chronically epileptic human neocortical slices obtained during epilepsy surgery. Localized and spatially inhomogeneous neuronal depolarizations were found to underlie spontaneous SSFP, which remained unchanged and spatially restricted to foci <750 micrometer diam even under epileptogenic (low-Mg(2+)) conditions. In cases where ictaform paroxysmal activity occurred in low-Mg(2+) medium, neuronal depolarizations were wide-spread but still spatially inhomogeneous, and the events were preferentially initiated at distinct foci. The findings suggest that small neuronal networks are able to establish and maintain synchronous rhythmic and epileptiform activity.

Action Potentials↗
PubMed2000

Prognostic factors in mesial temporal lobe epilepsy surgery.

Eighty-four patients submitted to anterior temporal lobectomy were evaluated retrospectively in order to correlate the different type of simple partial seizure (SPS) and their prognostic implications in patients with mesial temporal sclerosis. The patients were divided in two groups following the classification of Engel; Group 1 (53 patients) included patients Class I (without seizures or of good outcome) and Group 2 (31 patients) included Classes II, III and IV (with seizures or of bad outcome). The two groups were compared and results showed no statistical difference in relation to the demographic aspects as sex, side of surgery, age at onset of seizures and time of the patients' postoperative follow-up. Statistical analysis revealed no relationship between type of SPS and outcome. SPS did not show a statistical value in localizing the side of pathology. However, when the two groups were compared statistically in terms of patients' ages at the time of surgery, and the time elapsed from the onset of the seizures to the surgical intervention, it was observed that Group 1 (of good outcome) had seizures for smaller interval (p <0.05) and was operated at an earlier age (p<0.02) than Group 2 (of bad outcome). The presence or the type of SPS can not be used as a prognostic measure; surgical therapy must be considered as soon as clinical resistance is demonstrated.

Adolescent↗
PubMed1999

Population genetic studies on nine tetrameric short tandem repeat loci using fluorescence dye-labeled primers and capillary electrophoresis in the Austrian population.

The short tandem repeats (STR) D3S1358, VWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820 and a locus allowing sex discrimination (amelogenin) can be coamplified by the polymerase chain reaction using a commercially available kit, and subsequently typed using capillary electrophoresis. To establish databases for these loci for Austrian Caucasians, 115 unrelated persons were typed. All loci were in Hardy-Weinberg equilibrium. The combined mean paternity exclusion chance (MEC) was 0.999891 and the combined discriminating power (DP) was 3.08 x 10(-11). The allelic distributions showed no differences to those found for other Caucasian populations. Our data differed significantly from an Afro-American population at 5 loci and from a Chinese population at 4 loci. Linkage disequilibrium between any of the coamplified loci was not evident. Thus the combination of multiplex PCR and capillary electrophoresis can save time and yield excellent results for paternity testing and stain analysis.

Austria↗
PubMed1999

Bilateral reductions of hippocampal volume, glucose metabolism, and wada hemispheric memory performance are related to the duration of mesial temporal lobe epilepsy.

In refractory temporal lobe epilepsy (TLE) temporal lobe structures and functions are continuously or intermittently affected by abnormal brain electrical events, noxious neurochemical agents, and metabolic disturbances. There is conflicting evidence regarding the relationship between the duration of refractory mesial TLE and quantitative measures of temporal lobe functions and volumes of the hippocampi. Twenty patients (aged 28 +/- 7 years, 14 males) with an initial precipitating injury before the age of 5 years were subjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-d-glucose positron-emission tomography (PET), and the Wada test. We investigated whether the duration of unilateral refractory TLE (12 left, 8 right) affects hippocampal volume, glucose metabolism, or Wada hemispheric memory performance. Ipsilateral to the epileptogenic zone the hippocampal volume, metabolism, and Wada hemispheric memory performance were reduced compared to the corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and sex were negatively correlated with ipsi- and contralateral hippocampal volume, hippocampal metabolism, and Wada hemispheric memory performance. Moreover, ipsilateral Wada hemispheric memory performance and contralateral hippocampal glucose metabolism were correlated with the frequency of habitual seizures. Refractory TLE seems to be associated with a slow but ongoing bilateral temporal lobe damage. These cross-sectional results require verification by longitudinal studies carried out over a period of more than two decades.

Adolescent↗
PubMed1999

Reorganized cerebral metabolic interactions in temporal lobe epilepsy.

Patients with left temporal lobe epilepsy demonstrate language impairments that are not well understood. To explore abnormal patterns of brain functional connections with respect to language processing, we applied a principal component analysis to resting regional cerebral metabolic data obtained with positron emission tomography in patients with right- and left-sided temporal lobe epilepsy and controls. Two principal components were expressed differentially among the groups. One principal component comprised a pattern of metabolic interactions involving left inferior frontal and left superior temporal regions-corresponding to Broca's and Wernicke's areas, respectively-and right mesial temporal cortex and right thalamus. Functional couplings between these brain regions were abnormally enhanced in the left-sided epilepsy patients. The right thalamic left superior temporal coupling was also abnormally enhanced in the right-sided epilepsy patients, but differentially from that in the left-sided patients. The other principal component was characterized by a pattern of metabolic interactions involving right and left mid prefrontal and right superior temporal cortex. Although both the right- and left-sided epilepsy patients showed decreased functional couplings between left mid prefrontal and the other brain regions, a weaker right-left mid prefrontal coupling in the left-sided epilepsy patients best distinguished them from the right-sided patients. The two mutually independent, abnormal metabolic patterns each predicted verbal intelligence deficits in the patients. The findings suggest a site-dependent reorganization of two independent, language-subserving pathways in temporal lobe epilepsy.

Adolescent↗
PubMed1999

A new epileptic seizure classification based exclusively on ictal semiology.

Historically, seizure semiology was the main feature in the differential diagnosis of epileptic syndromes. With the development of clinical EEG, the definition of electroclinical complexes became an essential tool to define epileptic syndromes, particularly focal epileptic syndromes. Modern advances in diagnostic technology, particularly in neuroimaging and molecular biology, now permit better definitions of epileptic syndromes. At the same time detailed studies showed that there does not necessarily exist a one-to-one relationship between epileptic seizures or electroclinical complexes and epileptic syndromes. These developments call for the reintroduction of an epileptic seizure classification based exclusively on clinical semiology, similar to the seizure classifications which were used by neurologists before the introduction of the modern diagnostic methods. This classification of epileptic seizures should always be complemented by an epileptic syndrome classification based on all the available clinical information (clinical history, neurological exam, ictal semiology, EEG, anatomical and functional neuroimaging, etc.). Such an approach is more consistent with mainstream clinical neurology and would avoid the current confusion between the classification of epileptic seizures (which in the International Seizure Classification is actually a classification of electroclinical complexes) and the classification of epileptic syndromes.

Electroencephalography↗