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Biomedical subjects

A Ebner

Publications and source records attributed to A Ebner.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1999

Long term effects of refractory temporal lobe epilepsy on cognitive abilities: a cross sectional study.

OBJECTIVE: Intractable epilepsy is related to various transient and chronic brain electric and neurochemical disturbances. There is increasing evidence that chronic epilepsy induces secondary neuronal metabolic and structural decline. However, there is no convincing evidence that the cognitive abilities of patients deteriorate with increasing duration of intractable epilepsy. METHODS: To examine whether duration of refractory temporal lobe epilepsy (TLE) is related to generalised cognitive impairment, psychometric intelligence based on the full scale intelligence quotient (FSIQ, WAIS-R) was determined in 209 patients with unilateral TLE. For analyses of variance (ANOVA) patients were grouped into three categories: <15, 15-30, and >30 years of refractory TLE. RESULTS: An ANOVA and a multiple regression analysis showed that duration of TLE affects FSIQ. Patients with >30 years of TLE performed worse than patients with 15 or 30 years of TLE. The factors side of seizure origin and type of lesion on MRI did not reach significance. A second ANOVA including education as factor showed that in patients with higher educational attainment, the mean FSIQ was stable for a longer duration of TLE than in less educated patients. Retesting 6 months after anterior temporal lobectomy seizure free patients (n=85 of 127) had an higher FSIQ but showed a similar duration effect before and after anterior temporal lobectomy. The variables age at epilepsy onset, education, frequency of interictal epileptiform discharges, frequency of habitual and generalised seizures, serum concentration of antiepileptic drugs, and polypharmacy were statistically controlled. CONCLUSIONS: Psychometric intelligence of patients with a longer duration of refractory TLE were most severely impaired. Consequently, refractory TLE seems to be associated with slow but ongoing cognitive deterioration. It is assumed that epilepsy related noxious events and agents exhaust the compensatory capacity of brain functions. However, as in dementia and Alzheimer's disease, higher educational attainment as an indicator of higher brain reserve might delay the cognitive decline.

Adult↗
PubMed1998

Genetic variation at the STR loci D12S391 and CSF1PO in four populations from Austria, Italy, Egypt and Yemen.

The short tandem repeat systems (STRs) D12S391 and CSF1P0 were amplified by the polymerase chain reaction (PCR) on blood samples from 100 to 158 unrelated Austrians, Italians, Yemenians and Egyptians. The samples were analyzed by both native and denaturing electrophoresis and two primer pairs were tested for the CSF1PO locus. Except for the CSF1PO data on the Egyptians, no deviations from the Hardy-Weinberg equilibrium were detected. For D12S391, no significant differences were found between the two Arab populations and between the two European populations, but the differences between both Arab populations and the Italians were significant. For CSF1PO, differences were only observed between the Yemenians and all three other populations. No evidence of linkage disequilibrium between the two STRs was found. The observation of a D12S391 allele consisting of only 14 repeats was confirmed by sequencing.

Alleles↗
PubMed1998

Hemispheric asymmetries in category-specific word retrieval.

We examined whether 53 adult non-aphasic patients with either left (22) or right temporal lobe lesions (31) demonstrate dissociable patterns of hemispheric asymmetries in category-specific word fluency tasks. The patients were asked to articulate as many appropriate words as possible within 60 or 90 s in response to six target categories. There was no effect of patient groups on the overall fluency. However, patients with a left-sided temporal lobe lesion were impaired retrieving words to 'initial letters' and to the category 'animals'. Right temporal lobe patients were impaired retrieving 'tools' and words referring to specific visual attributes. There were no fluency differences for 'food-supermarket goods' and 'flat interior'. We conclude that temporal lobe damage can result in category-specific impairments in word retrieval depending on the affected hemisphere.

Adolescent↗
PubMed1998

Prospective comparison of flecainide versus sotalol for immediate cardioversion of atrial fibrillation.

This study sought to compare the efficacy and safety of intravenous flecainide and sotalol for immediate cardioversion of atrial fibrillation. We performed a prospective, randomized, single-blind, multicenter trial, including 106 hemodynamically stable patients with atrial fibrillation, stratified according to duration of the arrhythmia. Exclusion criteria included severely reduced left ventricular systolic function, recent antiarrhythmic therapy, and hypokalemia. Patients were randomly assigned to receive either intravenous flecainide or intravenous sotalol. Trial medication was given at a dose of 1.5 mg/kg body weight (maximum 150 mg). Overall, 28 of 54 patients (52%) given flecainide and 12 of 52 patients (23%) given sotalol converted to sinus rhythm during the first 2 hours after start of the infusion (p = 0.003). Multivariate analysis confirmed that treatment allocation to flecainide, an arrhythmia duration of < or = 24 hours, higher plasma magnesium level at baseline, higher age for men, and lower age for women independently increases the probability of conversion. The frequency of adverse effects was not significantly different in the 2 treatment groups.

Age Factors↗
PubMed1998

[Semiologic classification of epileptic seizures].

Recent advances in epileptology and epilepsy surgery require revision of the currently used International Classification of Epileptic Seizures, which was published 1981. We present a classification of epileptic seizures which is based purely on the clinical seizure semiology. The advantages of a semiological seizure classification are stressed.

Brain Mapping↗
PubMed1998

Semiological seizure classification.

We propose an epileptic seizure classification based exclusively on ictal semiology. In this semiological seizure classification (SSC), seizures are classified as follows: a. Auras are ictal manifestations having sensory, psychosensory, and experiential symptoms. b. Autonomic seizures are seizures in which the main ictal manifestations are objectively documented autonomic alterations. c. "Dialeptic" seizures have as their main ictal manifestations an alteration of consciousness that is independent of ictal EEG manifestations. The new term "dialeptic" seizure has been coined to differentiate this concept from absence seizures (dialeptic seizures with a generalized ictal EEG) and complex partial seizures (dialeptic seizures with a focal ictal EEG). d. Motor seizures are characterized mainly by motor symptoms and are subclassified as simple or complex. Simple motor seizures are characterized by simple, unnatural movements that can be elicited by electrical stimulation of the primary and supplementary motor area (myoclonic, tonic, clonic and tonic-clonic, versive). Complex motor seizures are characterized by complex motor movements that resemble natural movements but that occur in an inappropriate setting ("automatisms"). e. Special seizures include seizures characterized by "negative" features (atonic, astatic, hypomotor, akinetic, and aphasic seizures). The SSC identifies in detail the somatotopic distribution of the ictal semiology as well as the seizure evolution. The advantages of a pure SSC, as opposed to the current classification of the International League Against Epilepsy (ILAE), which is actually a classification of electroclinical syndromes, are discussed.

Electroencephalography↗
PubMed1998

Noninvasive determination of language lateralization by functional transcranial Doppler sonography: a comparison with the Wada test.

BACKGROUND AND PURPOSE: Functional transcranial Doppler ultrasonography (fTCD) can assess event-related changes in cerebral blood flow velocities and, by comparison between sides, can provide a measure of hemispheric perfusional lateralization. It is easily applicable, insensitive to movement artifacts, and can be used in patients with less than perfect cooperation. In the present study we investigated the validity of fTCD in determining the hemispheric dominance for language by direct comparison of fTCD with intracarotid amobarbital anesthesia (Wada test). METHODS: fTCD and the Wada test were performed in 19 patients evaluated for epilepsy surgery. By the Wada test, 13 patients were classified as left-hemisphere dominant and 6 as right-hemisphere dominant for language. fTCD was based on the continuous bilateral measurements of blood flow velocities in the middle cerebral arteries and event-related averaging during a cued word generation task previously shown to activate lateralized language areas in normal adults. RESULTS: In 4 patients fTCD assessment was not possible because of lack of an acoustic temporal bone window. In the remaining 15 candidates, determination of language dominance was concordant with the Wada test in every case. Moreover, the correlation of the lateralization measures from both procedures was highly significant (r=.92, P<.0001). CONCLUSIONS: This strong correlation validates fTCD as a noninvasive and practical tool for the determination of language lateralization that can be applied for clinical and investigative purposes.

Adolescent↗
PubMed1997

Prefrontal asymmetric interictal glucose hypometabolism and cognitive impairment in patients with temporal lobe epilepsy.

Depressions of regional cerebral metabolism beyond the epileptogenic zone have been demonstrated in patients with intractable temporal lobe epilepsy. However, their clinical relevance, and the causes of prefrontal metabolic asymmetries are less well understood. We investigated 96 temporal lobe epilepsy patients by FDG-PET and neuropsychological assessment who had a corresponding unilateral temporal hypometabolism, left hemisphere speech dominance, full scale IQ of > 70 and no extratemporal lesion in MRIs. The regional glucose metabolism was determined in each patient in homologous regions including prefrontal cortex, and normalized to whole brain metabolism. Regional differences of > 10% were regarded as asymmetrical. Prefrontal metabolic asymmetries were more frequent in patients with left temporal lobe epilepsy (21 left, six right) and a history of secondarily generalized seizures. A multivariate analysis of variance revealed a main effect for prefrontal metabolic asymmetry on neuropsychological 'frontal lobe measures', including verbal and performance intelligence measures. Prefrontal metabolic asymmetry was not related to 'measures of episodic memory', presence of psychiatric symptoms or frontal interictal epileptiform discharges. We conclude that prefrontal metabolic asymmetry is associated with cognitive impairment. Patients with temporal lobe epilepsy of the left speech dominant hemisphere and a history of secondarily generalized seizures are at considerable risk of developing prefrontal metabolic asymmetry.

Adult↗
PubMed1997

Localization of epileptic auras induced on stimulation by subdural electrodes.

PURPOSE: This study evaluates the localization of stimulation-induced auras (SIA) and tries to determine whether the SIA can help to define the boundaries of resection in epilepsy surgery. METHODS: Using subdural grid electrodes, 31 patients with drug resistant focal epilepsy were examined in a retrospective and prospective study lasting 2 years. RESULTS: On stimulation by subdural electrodes, we elicited habitual auras in 16 patients (52%). The zone of SIA overlapped the epileptogenic lesion in 12 patients (75%), the EEG seizure onset zone in 12 patients (75%), and the irritative zone of interictal spikes in eight patients (50%). Postoperative results showed a significant correlation with the complete removal of the epileptogenic lesion (p < 0.001). Because the number of patients in the study was small, we could not find a significant correlation with the complete removal of the SIA zone, EEG seizure onset zone, and irritative zone. CONCLUSIONS: Our study confirms previous analyses which indicate that complete resection of the epileptogenic lesion is essential to achieve a good outcome. Frequent overlap of the SIA zone with the epileptogenic lesion and the EEG seizure onset zone indicates proximity of the SIA with the epileptogenic zone. Nevertheless, this study does not support the concept that the SIA zone and the EEG seizure onset zone have additional value in defining the boundaries of resection in epilepsy surgery. Three case presentations suggest that SIA result from facilitated pathways between the stimulated cortex, the epileptogenic zone around the lesion, and the symptomatogenic zone. Functional reorganization in the vicinity of the cortical lesion cannot be ruled out but was not seen in our patients. Thus, SIA often do not reflect the normal function of the stimulated underlying cortex.

Adolescent↗
PubMed1997

Cerebellar atrophy and prognosis after temporal lobe resection.

OBJECTIVE: Experimental data indicate inhibitory effects of the cerebellum on seizure activity. Structural damage such as cerebellar atrophy, which is a common finding in patients with chronic epilepsy, may reduce these effects. METHODS: Outcome after temporal lobectomy was studied in 78 consecutive patients, with or without cerebellar atrophy diagnosed by MRI. RESULTS: Thirty five patients (45%) showed cerebellar atrophy. At a mean follow up of 14.6 (range, 6-40) months, 50 patients (64%) had no postoperative seizures. In these patients, the frequency of cerebellar atrophy was significantly lower (34%) than in patients who relapsed (64%, p < 0.01). Occurrence of generalised tonic-clonic seizures (GTCS) within two years before surgery, occurrence of GTCS at any time preoperatively, long duration of epilepsy, and older age at surgery were also associated with recurrence of seizures. Multiple logistic regression analysis suggested occurrence of GTCS within two years before surgery and cerebellar atrophy as the main predictive indicators. When both factors were present, the percentage of patients remaining seizure free since surgery fell to 30%, compared with 60% when only GTCS were present, 78.6% when only cerebellar atrophy was present, and 87.5% when both factors were absent. CONCLUSIONS: Cerebellar atrophy shown by MRI was a frequent finding in surgically treated patients with temporal lobe epilepsy. The presence of cerebellar atrophy seems to worsen the prognosis after temporal lobe resection.

Adolescent↗
PubMed1997

Ictal motor signs and interictal regional cerebral hypometabolism.

Early motor manifestations are the main components of focal seizures involving the frontal lobe. We examined the relationship between the initial ictal motor manifestations and interictal abnormalities of cerebral glucose consumption (rCMRGlc) as assessed by PET in 48 consecutive patients with focal seizures of neocortical origin. Group data analysis revealed that patients with predominantly unilateral clonic seizures had a significant contralateral perirolandic hypometabolism and to a lesser degree a contralateral frontomesial hypometabolism. Patients with predominantly focal tonic manifestations showed a hypometabolism within the frontomesial and perirolandic regions that was unilateral in all patients with lateralized tonic seizures. Patients with versive seizures had mainly contralateral metabolic depressions without a consistent regional pattern. Patients with hypermotor seizures had metabolic depressions involving frontomesial, anterior cingulate, perirolandic, and anterior insular/frontal operculum areas. In all patient groups, bilateral and symmetric hypometabolism of the thalamus and cerebellum was observed. We propose that this pattern of distinctly abnormal metabolic brain regions demonstrates not only possible epileptogenic zones but also symptomatogenic brain regions as shown by the associations between clinical manifestations and sets of abnormal brain regions, particularly if epileptogenic zones are in a clinically silent neocortical brain region. The detection and possible differentiation of symptomatogenic and epileptogenic zones might improve the effectiveness of presurgical noninvasive studies.

Adult↗
PubMed1997

Individual prediction of change in delayed recall of prose passages after left-sided anterior temporal lobectomy.

Prognostic variables for individual memory outcome after left anterior temporal lobectomy (ATL) were studied in 27 patients with refractory temporal lobe epilepsy. The difference between pre- and postoperative performance in the delayed recall of two prose passages (Story A and B) from the Wechsler Memory Scale served as measure of postoperative memory change. Fifteen independent clinical, neuropsychological, and electrophysiological variables were submitted to a multiple linear regression analysis. Preoperative immediate and delayed recall of story content and right hemisphere Wada memory performance for pictorial and verbal items explained very well postoperative memory changes in recall of Story B. Delayed recall of Story B, but not of Story A, had high concurrent validity to other measures of memory. Patients who became seizure-free did not differ in memory change from patients who continued to have seizures after ATL. The variables age at epilepsy onset and probable age at temporal lobe damage provided complementary information for individual prediction but with less effectiveness than Wada test data. Our model confirmed that good preoperative memory functioning and impaired right hemispheric Wada memory performance for pictorial items predict a high risk of memory loss after left ATL. The analyses demonstrate that the combination of independent measures delivers more information than Wada test performance or any other variable alone. The suggested function can be used routinely to estimate the individual severity of verbal episodic memory impairment that might occur after left-sided ATL and offers a rational basis for the counseling of patients.

Adolescent↗
PubMed1996

Reorganization of memory functions after human temporal lobe damage.

Hemispheric (re-)organization of episodic memory functions after temporal lobe damage (TLD) was investigated by the intracarotid amobarbital procedure in patients suffering temporal lobe epilepsy. Memory of the speech-dominant left hemisphere was intact after right-sided TLD independent of the age at manifestation. In contrast, the right hemisphere mediated memory well only after early left-sided TLD. These findings suggest a predisposition of the speech-dominant left hemisphere for the encoding of episodic memory, and indicate that for left-sided TLD the right hemisphere may compensate memory encoding sufficiently only if the damage occurred within a critical period in childhood.

Brain Damage, Chronic↗
PubMed1996

Successive activation of both cerebral hemispheres during cued word generation.

Most humans have a left hemispheric dominance for language. However, during diagnostic language testing there also is activation of the right hemisphere, which is probably related to attention. To investigate further the role of attention during language production we monitored cerebral blood flow velocities in the middle cerebral arteries by continuous bilateral transcranial Doppler ultrasonography (TCD) in nine right-handed subjects. During cued word generation, a successive activation of the right hemisphere in the preparatory phase, and of the left hemisphere during word searching was demonstrated. These findings indicate that attentional processes precede verbal activation and that the two procedures can be separated by comparative blood flow velocity measurement.

Acoustic Stimulation↗