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Biomedical subjects

C Helmstaedter

Publications and source records attributed to C Helmstaedter.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1997

Human temporal lobe potentials in verbal learning and memory processes.

Animal experiments and lesion studies have shown the importance of temporal lobe structures for language and memory. We recorded intracranial cognitive potentials from the human lateral and medial temporal lobe in 26 patients with temporal lobe epilepsy undergoing presurgical evaluation, using a word- and a picture-recognition paradigm. Neuropsychological testing included word fluency, verbal reasoning, sustained attention and a verbal learning memory test (VLMT), which was an adapted version of the Rey auditory verbal learning test. Word-specific N400-potentials elicited in the middle temporal gyrus of the dominant left hemisphere (LTL-N400) predicted immediate recall performance after learning, whereas N400s, elicited by words but not pictures in the left anterior medial temporal lobe (AMTL-N400), predicted delayed recall. The number of words that were learned but forgotten after a 30-min delay correlated only with N400s elicited by words in the left anterior medial temporal lobe. Thus, intracranial recordings indicated that different electrophysiological responses in different temporal lobe structures were linked to memory scores from specific neuropsychological tests.

Adolescent↗
PubMed1997

Nonconvulsive status epilepticus with generalized 'fast activity'.

We report the case of a 55-year-old patient with infrequent generalized tonic-clonic seizures since the age of 40 years and additional frequent episodes of disturbed behaviour and impaired cognition. The latter last from several hours up to one day with sudden onset and end of electroencephalographic (EEG) changes and clinical manifestations. They occurred about once a week before they were successfully treated with valproate and lamotrigine. From clinical, therapeutic and EEG findings we conclude that the patient suffers from nonconvulsive status epileptici, although the ictal EEG showed an untypical pattern of monomorphic generalized alpha rhythm. Many EEG characteristics point towards a primary generalized seizure disorder but a focal origin with secondary bilateral synchrony has to be considered as well. However, this is obviously a rare type which has not been described previously.

Alpha Rhythm↗
PubMed1997

Pre- and postoperative socioeconomic development of 151 patients with focal epilepsies.

PURPOSE: We evaluated retrospectively the socioeconomic development of epilepsy patients after temporal or extratemporal epilepsy surgery and analyzed the relationship to clinical and neuropsychological data. METHODS: 151 patients (from ages 11-65 years; mean postoperative followup: 3 years) replied to a structured questionnaire, which referred to objective data of the patient's educational and vocational development. Neuropsychological data were obtained from pre- and postoperative (1-year follow-up) examinations. RESULTS: The preoperative development data indicated that patients exposed to epilepsy at any developmental stage had a higher prevalence of educational/vocational difficulties as compared with patients with a later onset of epilepsy. Postoperatively, the integration of the formerly unemployed improved and the unemployment rate decreased from 33 to 16%. Out of those patients who had been schooled or who were employed, 79%-91% made progress in development, or were at least able to keep their status. Only 2 of 14 patients, who had been retired early because of their epilepsy, returned to employment. In general, a deterioration of the socioeconomic status was significantly related to insufficient seizure control. A reemployment of patients who were formerly unemployed depended mainly on age and neuropsychological outcome. CONCLUSIONS: Our results suggest that early and successful surgical intervention improves or at least maintains the socioeconomic situation, especially the employment status.

Adolescent↗
PubMed1997

Safety of intrahippocampal depth electrodes for presurgical evaluation of patients with intractable epilepsy.

PURPOSE: Intracerebral depth electrodes are used in preoperative evaluation of selected patients with intractable epilepsies. In spite of their usefulness, safety of depth electrodes is disputed, and the number of insertions is decreasing. This study examined retrospectively possible deleterious effects such as perioperative complications, induction of epileptogenesis, and neuropsychologic deficits. METHODS: Clinical course and neuroradiologic findings of 115 patients with bilaterally inserted longitudinal intrahippocampal depth electrodes (IDEs) were analyzed. Hippocampal resection specimens were examined histopathologically. To detect newly developed epileptogenic areas, EEG recordings, seizure control, and semiology after standardized resection procedures were compared between patients who received IDEs and those who did not. To demonstrate functional deficits caused by IDE insertion into an unaffected hippocampus of the speech-dominant hemisphere, changes of verbal learning and memory performances before and after right amygdalohippocampectomy were compared between patients evaluated with and without IDEs. RESULTS: Five significant complications without any permanent neurologic deficit were noted, and only one was specifically linked to IDE insertion. The tissue damage associated with the insertion was minimal and sharply circumscribed. No differences of seizure outcome after standardized resections were identified between patients with and without IDEs. In postoperative EEG recordings, there was no evidence of new epileptogenic areas. No verbal memory deficit caused by IDE implantation into the hippocampus of the speech-dominant hemisphere was detectable. CONCLUSIONS: Results indicate that it is safe to implant these IDEs in selected patients.

Adult↗
PubMed1996

Neuropsychological aspects of frontal lobe epilepsy.

While most neuropsychological studies in focal epilepsies are concerned with temporal lobe epilepsy (TLE), only few investigations aim cognitive functioning in unresected patients with frontal lobe epilepsy (FLE). Following functional models arising from lesional studies, we evaluated patients with TLE (21 left, 17 right) and FLE (6 left, 17 right) with respect to attention and speed, motor coordination, verbal/nonverbal fluency, concept formation, response inhibition, anticipatory behavior and memory span. The following results were obtained. When compared to TLE, FLE was associated with significantly poorer results in almost all tests, fluency tests being the exception. No group differences were found with respect to the lateralization of the epileptic focus or the presence or absence of cerebral lesions. Factor analysis of the tests indicated that different subfunctions (speed, STM, motor coordination, response maintenance and inhibition) were assessed. A particular cognitive pattern of impaired motor coordination or response inhibition appeared to be characteristic for patients with FLE.

Adult↗
PubMed1996

Verbal working memory components can be selectively influenced by transcranial magnetic stimulation in patients with left temporal lobe epilepsy.

The aim of this study was to investigate whether transcranial magnetic stimulation (TMS) can be used for a lateralization of verbal and non-verbal memory functions in candidates for epilepsy surgery by inducing focal, material-specific memory deficits. Twenty patients who underwent presurgical epilepsy evaluation with chronically implanted subdural strip electrodes were submitted to focal TMS over the temporal lobes and the vertex while sequences of items of the Digit Span and the Corsi Block test were presented on a computer screen. TMS was applied synchronously or 200 msec following presentation of each item. The effects of TMS on the memory span and the serial position curve were analysed in comparison to baseline levels. The following results were obtained: the quantitative effects on the verbal (Digit Span) and non-verbal (Corsi Block) memory span were not significant, but there were significant qualitative changes of serial position effects. In the group of six patients with left temporal epilepsy, TMS over the left temporal lobe induced a significant recency effect in the Digit Span test, while TMS over the vertex significantly increased the recency errors. The absolute number of errors remained unchanged. No such effects were observed in the group of nine patients with right temporal lobe epilepsy. These results suggest that in the presence of a left temporal lobe focus TMS can induce qualitative, material specific changes in verbal working memory (phonological loop) which become apparent in the serial position curve. The dissociation of TMS effects for temporal and vertex stimulation imply that TMS can selectively influence specific phonological loop components and that the phonological loop has a functionally and neuroanatomically multimodular structure.

Adolescent↗
PubMed1996

Cognitive consequences of two-thirds anterior temporal lobectomy on verbal memory in 144 patients: a three-month follow-up study.

Previous studies have shown that left temporal lobectomy for intractable epilepsy can lead to verbal memory deficits. However, patients with left temporal lobe epilepsy (LTLE) frequently have impaired verbal memory preoperatively. The present analysis of 144 patients who underwent temporal lobe resections for either left (n = 68) or right (n = 76) temporal lobe epilepsy (LTLE, RTLE) addressed the questions of (a) whether a left two-thirds anterior temporal lobectomy (ATL) increases deficits in these qualitative aspects of verbal memory already impaired preoperatively, and (b) whether other aspects of verbal memory are additionally affected. We also evaluated possible determinants of preoperative abilities and postoperative changes, using multiple regression analysis. Preoperatively, patients with LTLE differed from patients with RTLE only in poorer performance on measures of long-term consolidation/retrieval (delayed recall). This is related to hippocampal pathology and seizure severity. Only left temporal lobe resections resulted in significant deterioration in verbal learning and memory. Acquisition over learning trials and recognition deteriorated most markedly, whereas performance in long-term consolidation/retrieval showed only minor changes. Preoperative performance levels, chronological age, the extent of the en bloc resection, preoperative performance on figural memory, and preoperative seizure severity were valuable determinants of postoperative changes in acquisition and recognition. In contrast, changes in consolidation/retrieval related only to preoperative ability. Left two-thirds ATL leads to new impairment in addition to preexisting memory deficits. The finding that left temporal lobectomy affects verbal acquisition and recognition more than long-term consolidation/retrieval, including the different determinants of these changes, most likely reflects the differential effects of surgery on mesial temporal and neocortical temporal functions.

Adult↗
PubMed1995

Relations between verbal and nonverbal memory performance: evidence of confounding effects particularly in patients with right temporal lobe epilepsy.

Confounding left hemisphere verbalization strategies can be suggested as being a major problem in the evaluation of the assumed involvement of right temporo-limbic structures in "nonverbal" visual/figural memory processing. We addressed this issue by evaluating the easily-verbalized Benton-visual-retention-test in 60 patients with either left (LTLE) or right temporal lobe epilepsy (RTLE) and 30 healthy controls. We formally estimated the informational (verbal) content of each item which hypothetically would be needed to solely retain the item from verbal memory. The results indicated confounding of verbal learning and figural memory only in the presence of right temporal lobe dysfunctions. Selective visual/figural learning deficits in RTLE patients became obvious when the verbal load of the figural material exceeded their verbal learning capacity. Instead of excluding verbalization by the use of abstract figural items, its inclusion provides a possibility to control compensatory strategies which overshadow the presence of visual/figural memory deficits.

Adult↗
PubMed1994

Quantitative and qualitative evaluation of patterns of cerebral language dominance. An amobarbital study.

As a part of presurgical evaluation, 173 patients received bilateral intracarotid amobarbital tests for determination of cerebral language dominance. Language testing during intracarotid amobarbital procedures (IAP) consisted of the following tasks: automatic speech, sentence comprehension, body commands, naming, repetition, reading, and spontaneous speech. Patterns of cerebral language dominance were evaluated and discussed on five levels of analysis: (1) quantification of language dominance on the basis of a lateralization index derived from the total language scores in each IAP; (2) determination of five dominance subpatterns (left or right dominant, strongly bilateral, and incomplete left or right dominant) according to quantification performed on level (1) and clinical judgement; (3) qualitative differentiation of three kinds of bilaterality (positive, negative, and general) according to total language performance in left and right IAP; (4) analysis of grouped linguistic subfunctions extracted from performance in specific IAP subtests; (5) extraordinary individual case histories. The distribution of lateralization indices revealed only partially continuous degrees of lateralization, especially between the left-dominant and bilateral subgroups. As for the clinically oriented classification, incomplete left dominance is frequent (16.2%), while incomplete right dominance does not occur at all. Atypical dominance patterns are mostly correlated to bilateral and/or extratemporal foci. Concerning grouped subfunctions, a rotated factor matrix statistic yields an analysis of clusters of IAP subtests, where functions involving expressive language capacities are separated from those that are purely receptive. Further analyses of bilaterality subpatterns suggest that there are mainly four bilaterality phenomena, namely interhemispheric dissociation, double representation, unilateral representation of subfunctions, and partial representation of subfunctions in either hemisphere. Application of these differentiations to individual cases yields additional evidence that can be used in patient selection for operation in order to avoid postoperative neuropsychological deficits, especially in candidates for extratemporal surgery. In conclusion, a multilevel analysis of IAP language data is recommended since it permits a detailed account of varieties of language dominance patterns and contributes to more adequate presurgical decision-making in planned operations in cognitively relevant brain areas.

Adolescent↗
PubMed1994

Right hemisphere restitution of language and memory functions in right hemisphere language-dominant patients with left temporal lobe epilepsy.

Concomitant with the right hemispheric restitution of language functions after early left hemisphere lesions, suppression effects on originally right hemispheric visuospatial/constructional functions have repeatedly been reported. The present study evaluated this issue in 10 right hemisphere language-dominant patients with temporal lobe epilepsy. Left hemisphere language-dominant patients with left (n = 10) or right (n = 10) temporal lobe epilepsy served as controls. The following results were obtained: in all but one of the right dominant patients, left hemisphere lesions, left hemisphere foci and histories of early left brain damage indicated that secondary language transfer rather than a genetically determination is the more likely cause of the right hemisphere dominance. Despite this transfer, the language functions (comprehension, fluency, reasoning) of the right dominant patients remained significantly impaired. Language generally appeared to be better preserved in patients with an onset of epilepsy before the third year of life or a circumscribed left hemisphere lesion. No suppression effects could be detected on the level of complex cortical language and non-language functions. In contrast, on the level of temporo-limbic memory functions, verbal learning and recognition were left largely intact, albeit mostly at the expense of visuo-spatial learning and memory. The findings of the study thus indicate that the cerebral plasticity of the right hemisphere differs according to the extent of the left-hemisphere lesion, the onset of structural/functional damage and the complexity of the functions requiring restitution. Assuming that language and memory represent neocortical and palaeocortical functions, respectively, the restitution process is seemingly governed by their status in a phylogenetically determined hierarchy of functional importance.

Brain Diseases↗
PubMed1993

Differential effects of first antiepileptic drug application on cognition in lesional and non-lesional patients with epilepsy.

It has been shown that carbamazepine (CBZ) and valproic acid (VPA) have no significant negative or even positive side effects upon cognition in patients with epilepsy. The present study evaluated cognitive effects of CBZ or VPA in 16 patients with newly diagnosed epilepsy. Twelve patients had complex partial seizures, four patients primarily generalized seizures. Special attention was directed towards seizure type, presence of structural lesions and seizure control. Neuropsychological testing was carried out prior to medication and when drugs were within therapeutic ranges. Nineteen untreated healthy subjects served as controls. The following results were obtained: first of all, no general effect of antiepileptic drugs upon cognition could be detected. Only a subgroup with lesion (n = 8) and pre-existing cognitive deficits showed a significant decrease in memory performance during medication. This group additionally obtained poor seizure control. In conclusion, adverse cognitive changes under medication cannot be explained by antiepileptic drugs alone. The presence of cerebral lesions and obtained seizure control have to be considered as essential risk factors.

Attention↗
PubMed1993

[A special case of frontal lobe epilepsy].

We present clinical, electrophysiological and neuropsychological data of a patient with an extraordinary type of frontal lobe epilepsy. In addition to complex partial and secondary generalized seizures the patient had 183 non-convulsive states per day. Chronical electrocorticography via subdural electrodes clearly revealed that the complex partial seizures and the secondary generalized seizures originated within the right frontal lobe. During the non-convulsive states a constantly increasing spike frequency which showed characteristics of secondary bilateral synchrony was noticed within both frontal lobes. After a period of 20-40 min a sudden transition into a clinically generalized seizure occurred. In contrast to the clinical generalization the onset of bilateral motor phenomena was paralleled by a "secondary focalisation" of the pre-existent high frequency interictal bifrontal epileptiform activity within the right frontal lobe.

Adult↗
PubMed1992

Interhemispheric dissociation of expressive and receptive language functions in patients with complex-partial seizures: an amobarbital study.

Bilateral intracarotid amobarbital procedures (IAP) were performed in 144 patients with medically intractable complex-partial seizures. As a result of language testing, 29 patients (20.1%) were found to have bilateral language representation to different degrees. In four (2.8%) of these patients--all right-handers with early onset of epilepsy and/or evidence of early brain damage--there was strong evidence of an interhemispheric dissociation of expressive and receptive language functions. Two of these patients had circumscribed temporal foci (one left, one right), and receptive language functions were represented in the hemisphere contralateral to the focus. One patient with a right frontal focus showed left-hemisphere dominance for expressive functions, while the fourth patient exhibited left-hemisphere dominance for receptive functions associated with a right temporo-parietal focus. It is argued that in these four cases the circumscribed functional and/or structural impairments have led to a shift of the anatomically associated language functions to the opposite hemisphere (rather than to neighboring regions of the same hemisphere). These findings substantiate the hypothesis that in special circumstances the anterior (expressive) language area can be located in one hemisphere and the posterior (receptive) area in the other.

Adolescent↗
PubMed1992

Early signs of cognitive deficits among human immunodeficiency virus-positive hemophiliacs.

A total of 181 human immunodeficiency virus (HIV)-seropositive hemophiliacs and 28 hemophilic controls were evaluated by psychometric tests and by electroencephalogram (EEG). Patients were classified from stages 1-6 according to the immunological criteria of the Walter Reed staging system. Statistical analysis of psychometric data showed an effect of the stage of the disease on test performances, indicating a decline in attention, accumulation of perceptual interferences, decline in visuoperceptual speed and visuomotor response speed and reduced verbal memory performance, especially in stage 6 patients. Comparison of performance levels with normative test data already revealed cognitive deficits in about 20-30% of the patients in stages 2-5. As regards verbal memory, especially learning and recognition of new verbal information were impaired. In contrast, there was no significant deficit for nonverbal memory processing. Compared with the controls, patients exhibited an increasing number of abnormal EEG findings in stages 2-6. As a conclusion, in the stages before acquired immunodeficiency syndrome (AIDS) develops, EEG findings as well as psychometric findings indicate central nervous system involvement of AIDS in about 20-30% of cases, whereas in full-blown AIDS there is a marked increase to 80%. Besides a more general deficit of attention and psychomotor speed as is seen in subcortical dementia, there is evidence for a particular verbal learning disorder, suggesting additional selective impairment of the brain.

AIDS Dementia Complex↗
PubMed1992

[Stage-independence and individual outcome of neuro-cognitive deficits in HIV. A follow-up study of 62 HIV-positive hemophilic patients].

62 of a series of 188 HIV-positive hemophiliacs, who had been neuropsychologically evaluated already in 1988 (T1), were re-examined 1 1/2 years later (T2). The aims of the study were to confirm the cross-sectional results of the 1988 study and to compare cross-sectional and longitudinal aspects of HIV infection and associated neurocognitive deficits. Patients were staged at T1 and T2 according to CDC classification criteria and retested using parallel tests of attention, verbal/nonverbal memory performance and depression. The following results were observed: (i) Data at T2 paralleled the findings from 1988, indicating increased deficits in attention and verbal learning and memory at an advanced stage of the disease. No association with the T4/T8 ratio was found. (ii) Between T1 and T2, 65% of the patients showed no change in stage, 27% changed one stage and only 8% showed a rapid progression through two stages. (iii) Only this latter group showed a significant cognitive deterioration over time. The remaining groups exhibited inconsistent performance changes which did not correlate with depression of changes of the T4/T8 ratio. Conclusively, the longitudinal data support the assumption of stage independent and individual different courses of the neurocognitive manifestations of HIV. A small minority of patients, however, manifested a rapid progression of the disease during the T1-T2 interval.

AIDS Dementia Complex↗
PubMed1991

Visual learning deficits in nonresected patients with right temporal lobe epilepsy.

A visual learning test Diagnostikum für Zerebralschäden (DCS) was revised and applied to three matched patient groups defined by interictal and ictal EEG findings: 24 patients with left temporal lobe epilepsy (LTE), 19 patients with right temporal lobe epilepsy (RTE) and 34 patients with a bitemporal epileptic involvement (BTE). Fifty seven healthy subjects served as controls. Performance on a measure of sustained attention and visual construction was also assessed. Results were as follows: (1) In contrast to controls and LTE patients, patients with right temporal epileptic involvement (RTE/BTE) showed a significantly reduced immediate recall as well as a reduced learning capacity and mean learning performance. (2) Patients made significantly more errors than controls, with RTE patients exhibiting the most visuo-spatial errors. (3) RTE/BTE patients additionally showed impaired performances on visuo-construction, but when visual construction scores were used as covariate, they did not diminish the strong group effects upon learning. (4) Attentional deficits were independent from memory deficits and rather reflected the bitemporal extention of epilepsy. As a conclusion, the data suggest an impairment of visual-spatial consolidation processes in patients with right temporal lobe epilepsy.

Adult↗