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Biomedical subjects

C Helmstaedter

Publications and source records attributed to C Helmstaedter.

At least 19 recordsLinked to original sources
PubMed1999

Pre- and postoperative neuropsychological profiles in children and adolescents with temporal lobe epilepsy.

PURPOSE: To evaluate the neuropsychological performance of children before and after temporal lobe resection (TLR). METHODS: Memory, attention, language, and visuoconstructive abilities were examined in 20 children (age 10-16 years) before, and 3 and 12 months after TLR (right, n = 10; left, n = 10; two-thirds anterior resection, n = 16; amygdalohippocampectomy, n = 4). Preoperative performance was compared with data of 30 age-matched healthy children; changes in performance after surgery were determined by repeated-measurement multivariate analysis of variance (MANOVA) and by use of reliable change indices (RCI). RESULTS: Preoperatively, no differences were observed between patients and controls in verbal and figural memory performance. Children with temporal lobe epilepsy (TLE), however, and particularly those with a left temporal focus, showed significantly reduced language performance. Repeated-measurement statistics indicated that memory performance did not change after surgery, whereas language performance and attention significantly improved 3 months and 1 year after surgery, respectively. Individual evaluations of memory showed gains in five children and deterioration in four children. Poor seizure control appeared the decisive variable characterizing children with losses in memory. CONCLUSIONS: Compared with adults, pre- and postoperative memory data suggest less pronounced hemispheric differences in school-age children with TLE. The results raise the possibility that children have a lower risk of memory deterioration after TLR, which may be due to their larger potential for cerebral plasticity.

Adolescent↗
PubMed1999

Surgical outcome in a group of low-IQ patients with focal epilepsy.

PURPOSE: Because a low IQ score indicates global brain damage, several authors consider it a contraindication for resective epilepsy surgery. This study reports the postoperative results of a small group of subaverage-intelligence patients with epilepsy who underwent focal resections. METHODS: We report on 16 patients who underwent focal resections (no callosotomy or hemispherectomy). All had IQ's <85 and were >13 years of age at the time of surgery. Low IQ was psychometrically assessed (mean IQ = 70) and confirmed by the patients' educational/occupational status. Clinical characteristics, findings from the preoperative workup, and the surgical treatment are described in detail. Postoperative outcome was evaluated with respect to seizure relief and cognitive/ socioeconomic development. RESULTS: Three months after surgery, 14 (87%) of 16 patients were completely seizure free, and nine (64%) of 14 were seizure free at the 1-year follow-up. Patients' cognitive abilities and socioeconomic status were mostly unchanged and in some cases improved. Seizure outcome was not related to IQ level, and there was no evidence of multiple epileptic foci in the patients with continued seizures. CONCLUSIONS: A low IQ level does not entail the presence of extended epileptogenic regions or multiple epileptic foci. Seizure-relief rates in our group concurred with the rates in patients of average intelligence, and the cognitive/socioeconomic outcome was favorable. We conclude that focal surgery in intellectually impaired patients can be recommended if the preoperative diagnostics confirm a circumscribed seizure onset.

Adolescent↗
PubMed1999

Clinical relevance of amygdala sclerosis in temporal lobe epilepsy.

OBJECT: The goal of this study was to define the incidence and clinical significance of amygdala sclerosis (AS) in patients with temporal lobe epilepsy (TLE). METHODS: Surgical specimens of the lateral amygdaloid nucleus and the hippocampus excised from 71 patients who were treated for medically intractable TLE were quantitatively evaluated using a computer-assisted image-analysis system and compared with 10 normal autopsy specimens. Densities of neurons and reactive astrocytes in the patients with TLE were correlated with clinical, neuropsychological, and depth-electroencephalography data. The neuron counts of the lateral amygdaloid nucleus did not correlate with various presumed etiological factors of TLE including hereditary seizures, birth complications, febrile convulsions, traumatic brain injury, infections, seizure semiology, and epileptological outcome. However, patient age at surgery was significantly higher (mean difference 10 years) when AS was present, as compared with patients without AS (p < 0.01). Seizure origin, as determined by using amygdalohippocampal depth electrodes, did not correlate with the presence or absence of AS. Neuropsychologically, there was a significant correlation between the neuronal densities of the lateral amygdaloid nucleus and both preoperative visual recognition and postoperative deterioration of short-term verbal memory performance (p < 0.05). CONCLUSIONS: Except for the relatively long history of epilepsy, the presence of AS is not associated with specific clinical or electrocorticographic features of mesial TLE. However, patients without AS are particularly at risk for deterioration of short-term verbal memory following amygdalohippocampectomy.

Adolescent↗
PubMed1998

Limbic ERPs predict verbal memory after left-sided hippocampectomy.

Surgical removal of the dominant medial temporal lobe regions runs a considerable risk of verbal memory deficits which may be compensated for postoperatively by corresponding regions in the non-dominant medial temporal lobe. We examined this possibility by recording event-related potentials (ERPs) to words from the medial temporal lobes of patients with left-sided temporal lobe epilepsy (TLE) undergoing presurgical evaluation. N400 amplitudes in the right anterior medial temporal lobe predicted the postoperative verbal recall performance of individual patients with surprising accuracy, indicating that intracranial recordings can be used to quantify the functional capacities of the right hemisphere that can compensate for the verbal memory deficits after loss of medial temporal lobe structures in the left hemisphere.

Adolescent↗
PubMed1998

Verbal novelty detection within the human hippocampus proper.

Animal studies and neuropsychological tests of patients with temporal lobe epilepsy have demonstrated the importance of human medial temporal lobes for memory formation. In addition, more recent studies have shown that the human hippocampal region is also involved in novelty detection. However, the exact contribution of the hippocampus proper to these processes is still unknown. To examine further its role we compared event-related potentials recorded within the medial temporal lobes in 29 temporal lobe epilepsy patients with and 21 without hippocampal sclerosis. While in patients with extrahippocampal lesions but without hippocampal sclerosis event-related potentials to first presentations and repetitions of words were reduced on the side of the epileptogenic focus, in patients with hippocampal sclerosis only those to first presentations but not to repetitions were affected. Because sclerosis of the hippocampus proper selectively reduced event-related potentials to new but not old verbal stimuli, it can be concluded that the human hippocampus proper contributes to verbal novelty detection.

Adolescent↗
PubMed1998

Neuropsychological consequences of epilepsy surgery in frontal lobe epilepsy.

The present study investigated the effect of frontal lobe surgery on "cognitive functions", which have previously been shown to be discriminative in the evaluation of non-resected patients with frontal lobe epilepsy (FLE). The cognitive outcome was evaluated with particular consideration of the side (left/right), the site (lateral, orbital, mesial, premotor/SMA), the type of surgery (resections vs. resections plus multiple subpial transections; MST), and seizure outcome. The evaluation is based on 33 patients with left (n = 17) or right (n = 16) frontal surgery. Forty-five patients who underwent successful left (n = 21) or right (n = 24) temporal lobectomy served as controls. The neuropsychological examination covered speed/attention, motor sequencing/coordination, response maintenance/inhibition, short-term memory, and language. With the exception of short-term memory, the chosen tests were discriminative in determining preoperative frontal lobe dysfunctions but they did not differentiate patients with a different lateralization or localization of the frontal focus. At the 3 month follow-up examination, patients with temporal lobectomy had improved frontal functions, whereas patients with frontal lobe surgery showed a mild deterioration. Within the frontally resected group, completely seizure-free patients had significantly improved short-term memory. Further consideration of the side, site and the type of the frontal resection indicated that patients with premotor/SMA surgery and patients with precentral/central MST had additional impairment after surgery. Premotor/SMA resections led to a deterioration in response maintenance/inhibition and if performed left sided also to deteriorated language functions. The latter impairment could be clearly related to transient aphasia directly after surgery. Irrespective of pareses observed immediately after surgery, patients with MSTs of the precentral/central areas displayed additional problems in motor coordination at the follow-up examination. In this group the seizure outcome was also less favourable. In summing up, frontal lobe surgery does not cause any considerable additional impairment in the short-term follow-up. However, caution is recommended when surgery or MST affect functional relevant cortex (here the prefrontal/SMA and precentral/central area). Finally, a release of functions associated with frontal areas not affected by surgery is suggested, when seizures are successfully controlled by surgery.

Adult↗
PubMed1998

Neuropsychological consequences of epilepsy surgery in frontal lobe epilepsy.

The present study investigated the effect of frontal lobe surgery on "cognitive functions", which have previously been shown to be discriminative in the evaluation of non-resected patients with frontal lobe epilepsy (FLE). The cognitive outcome was evaluated with particular consideration of the side (left/right), the site (lateral, orbital, mesial, premotor/SMA), the type of surgery (resections vs resections plus Multiple Subpial Transections), and seizure outcome. The evaluation is based on 33 patients with left (n = 17) or right (n = 16) frontal surgery. Forty-five patients who underwent successful left (n = 21) or right (n = 24) temporal lobectomy served as controls. The neuropsychological examination covered speed/attention, motor sequencing/coordination, response maintenance/inhibition, short-term memory, and language. With the exception of short term memory, the chosen tests were discriminative in determining preoperative frontal lobe dysfunctions but they did not differentiate patients with a different lateralization or localization of the frontal focus. At the three month follow-up examination, patients with temporal lobectomy had improved frontal functions, while patients with frontal lobe surgery showed a mild deterioration. Within the frontally resected group, completely seizure free patients had significantly improved short-term memory. Further consideration of the side, site and the type of the frontal resection indicated that patients with premotor/SMA surgery and patients with precentral/central MST had additional impairment after surgery. Premotor/SMA resections led to a deterioration in response maintenance/inhibition and if performed left sided also to deteriorated language functions. The latter impairment could be clearly related to transient aphasia directly after surgery. Irrespective of pareses observed immediately after surgery, patients with MST's of precentral/central areas displayed additional problems in motor coordination at the follow-up examination. In this group the seizure outcome was also less favorable. In summing up, frontal lobe surgery does not cause any considerable additional impairment in the short term follow-up. However, caution is recommended when surgery or MST affect functional relevant cortex (here the prefrontal/SMA and precentral/central area). Finally, a release of functions associated to frontal areas not affected by surgery is suggested, when seizures are successfully controlled by surgery.

Adolescent↗
PubMed1998

The performance-complaint relationship in patients with epilepsy: a matter of daily demands?

Weak relationships have been reported between subjective complaints of memory deficits and memory performance in neuropsychological tests in patients with temporal lobe epilepsy (TLE). This study investigated whether the individual exposure to cognitive demands in daily life contributes to cancel out the performance-complaint relationship in such a way that cognitive deficits are more likely experienced by patients in 'high demand' than in 'low demand' situations. Neuropsychological performance, subjective complaints and daily demands were assessed in 57 TLE-patients 1 year after a temporal lobe surgery. Data were analyzed using non-parametric statistical techniques. Results indicated surprisingly close relationships between subjective complaints and memory performance in standardized tests. The highest correlations were found for the non-verbal memory test. Cognitive demands did not counteract this result. Contrary to our expectation, lower demands were associated with stronger subjective complaints. Cognitive demands thus appeared not as a modulating factor that weakens the relationship between test deficits and subjective complaints in patients with TLE.

Activities of Daily Living↗
PubMed1998

Ecological validity of list-learning tests and self-reported memory in healthy individuals and those with temporal lobe epilepsy.

We evaluated in patients with temporal lobe epilepsy (TLE) and healthy volunteers whether list-learning tests of episodic verbal/figural memory and subjective self-reports reliably indicate "Memory in Reality" (MIR). MIR was assessed by the incidental memory of the neuropsychological test event one week after testing. Subjective Memory was assessed by a questionnaire (SMQ). Patients achieved poorer results than controls in all measures of memory. Correlation and multiple regression analysis indicates that list-learning is highly predictive regarding performance in MIR. MIR predominantly relied on verbal memory in patients and on visual/figural memory in controls. Subjective memory differentiated patients and controls but it correlated to MIR only in subjects with unimpaired memory. In conclusion, the data indicate a high ecological validity of list-learning paradigms and they seriously question the diagnostic value of self-reported memory. They also indicate that incidentally acquired knowledge might be differentially represented in patients with a memory disorder and healthy persons.

Adult↗
PubMed1998

Functional plasticity after left anterior temporal lobectomy: reconstitution and compensation of verbal memory functions.

PURPOSE: This study investigated the functional plasticity of the brain to reconstitute and compensate for verbal memory functions after epilepsy surgery of left temporocortical and temporomesial structures. We hypothesized that memory outcome would be best when surgery is performed within the period of cerebral plasticity, and that the outcome should be worst when fluid intelligence starts to decrease with physiologic aging. We also raised the question of different plasticity and compensation mechanisms for temporomesial and temporocortical memory functions. METHODS: We evaluated preoperative and 1-year-postoperative memory data and other verbal functions in 104 patients with epilepsy, who underwent a standard left anterior temporal lobe resection. We used memory measures that had been previously shown to be most selective for mesial and lateral functions, respectively. Determinants of postoperative memory outcome were evaluated by multiple regression analysis. Group statistics were calculated on the basis of the periods that are usually assumed to be significant for plasticity and behavioral compensation. Individual postoperative changes in memory functions were evaluated on the basis of test-retest data obtained in a group of 100 nonsurgical patients with localization-related epilepsies (mean retest interval >12 months). RESULTS: Only changes in cortically represented learning and data acquisition were related to age, plasticity, and capacities for behavioral compensation. No patient in the youngest group (younger than 15 years), 33% of patients who had surgery between the ages of 15 and 30 years, and 61% of the patients undergoing surgery older than age 30 years had significant deterioration in verbal learning. In contrast, postoperative changes in temporomesial consolidation/retrieval processes were independent of age at the time of surgery, plasticity, and capacities for behavioral compensation. CONCLUSIONS: Our data indicate different time windows for the reconstitution and compensation of mesial and cortical aspects of memory. Whereas the reconstitution of and compensation for cortical functions appear restricted by decreasing plasticity and physiological aging, mesial functions seem to be reconstituted by contralateral mesial structures over a much longer period. Concerning drug-resistant localization-related epilepsies, our results justify early consideration of surgery, especially when cortical structures are affected.

Adolescent↗
PubMed1998

Right hippocampal contribution to visual memory: a presurgical and postsurgical study in patients with temporal lobe epilepsy.

OBJECTIVES: Existing speculations regarding the cognitive functions of the right hippocampus suggest a special involvement in non-verbal memory functions. However, all supporting evidence in epileptic patients came from postoperative studies that did not consider the preoperative functioning level. The present study investigates in patients with right temporal lobe epilepsy (RTLE), both preoperatively and postoperatively, the role of the right hippocampus for visual memory, visuoconstruction, and spatial visualisation. METHODS: Two groups of patients with RTLE with and without right hippocampal damage (HC+/n=15 v HC-/n=13) were set up retrospectively thereby taking into account the surgical treatment (selective amygdalohippocampectomy v temporal resections sparing the hippocampus), the postoperative pathological findings (hippocampal sclerosis in the HC+ group) and the seizure outcome (all seizure free). The two groups were compared with regard to their neuropsychological performance preoperatively and 3 months after temporal lobe surgery. RESULTS: The preoperative results indicated impaired visual memory performance only for the HC+ patients, whereas the HC- patients exhibited no deficiencies in any of the assessed functions. Postoperatively, both groups exhibited partially improved performances. The type of surgical treatment had no different effects on the postoperative performance changes. CONCLUSIONS: The results suggest that hippocampal damage is the major cause of non-verbal memory deficiencies in preoperative patients with right temporal lobe epilepsy. Hence the results support and extend findings from previous postoperative studies. Right hippocampal resections did not increase the preoperative visual memory deficiencies, thus supporting the view that right temporal lobe resection in general bears only small risks for cognitive deteriorations.

Adult↗
PubMed1997

Evidence of very fast memory consolidation: an intracarotid amytal study.

This study provides evidence from intracarotid amobarbital tests (IAT) in patients with epilepsy that complete suppression of the electrophysiological activity of the left language-dominant hemisphere through left IAT does not impair memory for verbal information given 1 min or immediately before the injection of the barbiturate. Although language functions were completely disrupted and patients were unable to encode new information during the left IAT, pre/post memory was as good as in the right IAT. This lack of retrograde amnesia leads to the conclusion that a relatively stable representation of events is achieved within seconds after encoding. The results contradict models which assume that short-term memory is based on purely electrophysiological processes.

Amobarbital↗
PubMed1997

Rey Auditory-Verbal Learning Test: structure of a modified German version.

The Auditory Verbal Learning Test (AVLT) is widely used in scientific research as well as in clinical practice. But there exists little research on the structure of the AVLT. We investigated the structure of a German version of the AVLT and VLMT, in 232 patients of a psychiatric clinic and in 872 patients of an epileptologic clinic. First we stated a theoretical LISREL model relating the observed variables of the VLMT to short-term memory (STM) and long-term memory (LTM) as latent variables. Then we estimated the postulated LISREL model in the two samples. The proposed model showed excellent fit in both samples, and there were no significant deviations between the estimated and the observed covariance matrices. Thus, STM and LTM suffice to explain the structure of the VLMT, and the proposed structural equations model can be used to estimate STM and LTM capacity from VLMT data.

Adult↗
PubMed1997

Patterns of language dominance in focal left and right hemisphere epilepsies: relation to MRI findings, EEG, sex, and age at onset of epilepsy.

The present study evaluates results of language testing during intracarotid amobarbital procedures in 167 patients with either left (LHE, n = 81) or right hemisphere epilepsies (RHE, n = 86). In both groups there was a high rate of deviance from complete left hemisphere dominance of 24 and 31%, respectively. Whilst complete right hemisphere or incomplete left hemisphere language dominance were the prominent atypical patterns in LHE, RHE was associated with either bilateral dominance or incomplete left dominance. In LHE, atypical language dominance was frequently associated with an extratemporal localization of lesions or epileptic foci. The age at onset of epilepsy and the degree of right hemisphere language dominance correlated significantly in LHE but not in RHE. Finally, atypical dominance in LHE but not in RHE was associated with poorer language and nonlanguage functions, the latter being negatively correlated with the degree of right hemisphere language dominance. Conclusions are: (1) The data contradict the assumption of equipotentiality and favor the supposition of a predetermined left hemisphere superiority in language processing. (2) Atypical language dominance in LHE can largely be explained in terms of a plasticity dependent language shift as a consequence of early left hemisphere epilepsies and lesions. (3) Atypical dominance patterns in RHE appear to reflect the prevalence of genetically determined variants and the possibility of a language transfer from the right to the left hemisphere.

Age of Onset↗
PubMed1997

Differential involvement of left temporolateral and temporomesial structures in verbal declarative learning and memory: evidence from temporal lobe epilepsy.

A wealth of animal and human research has pointed to a significant involvement of the temporal lobes in memory processing, and yet the different functional roles of temporal cortical vs. mesial structures remain unclear. We studied verbal declarative memory, by using a word list paradigm that differentiates among learning (immediate recall), memory (delayed recall), and recognition, in epilepsy patients being considered for surgical resection of the left temporal lobe. Verbal memory was evaluated preoperatively and during the recording of intracranial event related potentials and postoperatively after selective hippocampectomy, temporal cortical lesionectomy, or anterior two-thirds en bloc temporal lobe resection procedures. Preoperative differences in verbal memory performance as a function of differences in underlying neuropathology, concurrent event-related potentials, and specific patterns of postoperative memory impairments lead to converging evidence that verbal declarative memory relies on a synergistic interaction of at least two functionally distinct brain systems. Material-specific data acquisition, or working memory, is mediated by neocortical temporal structures, whereas long-term consolidation/retrieval is particularly mediated by temporomesial structures. In contrast to the left temporal neocortex, the function of the temporomesial system appears to be material nonspecific. Apparently, its preferential involvement in verbal memory is due to its close interaction with overlying neocortical structures that are specialized for language processing.

Adult↗
PubMed1997

Relational verbal memory processing in patients with temporal lobe epilepsy.

Patients with left temporal lobe epilepsy (LTLE) have been shown to demonstrate impaired categorization in semantic memory tasks leaving open the question whether this is due to problems with active categorization or to problems with consolidation/retrieval of relations. 35 patients with left or right temporal lobe epilepsy (LTLE, RTLE) and 20 healthy controls performed three verbal learning and memory tests differing in the relational distance between the items to be learned (unrelated, low associative, high associative). In order to separate the memory component in relational memory processing, we avoided problems in active categorization and perception of semantic relations by presenting category members already clustered in the order of category membership, and by checking whether the patients had actually noticed the categories. In controls and in patients with RTLE, both semantic conditions significantly improved the test performance. LTLE-patients showed the worst test performance independent of the test condition. Their performance improved under the high associative condition, but they did not at all profit from the low associative condition. Although the semantic tasks had no demand on active clustering and although all LTLE-patients noticed the relational properties very well, they could not make use of the offered clusters. They demonstrated significantly more "item specific" than "relational" encoding than the other groups. This was pronounced in the low associative condition but became evident also in the high associative condition. In contrast to the other groups, the order in recall (clustering) deteriorated with passing time in LTLE-patients. In conclusion the data provide evidence of impaired semantic relational processing in LTLE. The impairment depends on the relational properties of the material to be learned, in that it increases with the relational distance between the memory contents. Because the tasks did not demand active clustering, we can attribute this impairment to deficits in relational encoding/retrieval which would be consistent with current opinions of the role of temporolimbic structures in relational memory processing.

Adult↗