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Biomedical subjects

H G Wieser

Publications and source records attributed to H G Wieser.

At least 19 recordsLinked to original sources
PubMed1992

[Indications for surgical treatment of epilepsy].

The evaluation of drug-resistant epileptics in view of causal surgical epilepsy therapy aims at accurate identification of the 'epileptogenic area'. Definition of the 'epileptogenic area', which is not synonymous or coexistent with the 'lesional area', as a positively defined area of seizure onset is obtained through the recording and analysis of spontaneous habitual seizures with electrodes placed in or close to the presumed epileptogenic brain areas. Interictal epileptiform field potentials are important too. Long-term intracranial recording techniques include direct intracerebral stereotactic depth-recording (stereo-electroencephalography, SEEG) and epicortical recordings with the use of foramen ovale as well as subdural strip and grid electrodes. The use of SEEG requires rigorous criteria, and the anatomy and vessels of the individual brain must be known in terms of a stereotactic reference system. Multi-contact flexible hollow-core electrodes are stereotactically implanted into strategically important targets, according to the evaluation strategy for a given patient. For presurgical assessment of potential candidates for selective amygdalo-hippocampectomy we have developed a less invasive extracerebral recording technique. It consists of bilateral insertion of solid four-contact electrodes via the foramen ovale, with positioning of the tips of the electrodes at the end of the ambient cistern. This technique permits stable and excellent recording from the mediobasal limbic structures of both temporal lobes. Personal experience with long-term extra-operative intracranial recording and stimulation now includes 131 patients evaluated with SEEG and 109 patients evaluated with foramen ovale electrodes.

Anticonvulsants↗
PubMed1992

123I-iomazenil: a quantitative study of the central benzodiazepine receptor distribution.

Fourteen patients with temporal lobe epilepsy, 9 patients after amygdalohippocampectomy and 3 healthy volunteers were examined with the new benzodiazepine receptor marker 123I-Iomazenil and SPECT. For comparison perfusion SPECT studies with 99mTc-HMPAO were done and a quantitative ROI analysis of the data performed. This quantitative analysis consisted of calculation of right-to-left ratios for 123I-Iomazenil SPECTs, whereby values of 1 were obtained with narrow standard deviations. ROI measurements of the medial occipital, frontal and parietal cortex, the cerebellum and white matter showed a pattern of benzodiazepine receptor concentration in concordance with that previously found in PET and autoradiographic studies, if 123I-Iomazenil ROIs were normalized to the corresponding 99mTc-HMPAO ROIs. The abnormal distribution in the temporal lobes will not be discussed in this paper.

Adult↗
PubMed1992

[Preoperative localization diagnosis in focal epilepsy using PET].

We present results of studies in which positron emission tomography was applied to the presurgical evaluation of epileptics. Emphasis is placed on results of PET studies with various tracers in partial epilepsies and on the use of PET in age-related epileptic syndromes in children.

Deoxyglucose↗
PubMed1991

[Variability of seizure phenomenology in the light of stereo-EEG studies].

The demonstration of a largely stable electroclinical semiology in the early phase of seizures is a main prerequisite for successful causative surgery of epilepsy. A few experiences with analysis of similarities during seizures are presented and discussed regarding their fundamental pathogenetic but also practical clinical significance. The primary data stem from candidates for selective surgery of the temporal lobe, mainly afflicted by psychomotor seizures. These seizures were recorded either by invasive stereoelectroencephalography or by semi-invasive foramen ovale electrodes.

Electroencephalography↗
PubMed1991

Comparison of valproate concentrations in human plasma, CSF and brain tissue after administration of different formulations of valproate or valpromide.

The concentration of valproate was measured in plasma, CSF and brain tissue of patients who underwent resective surgical treatment because of severe temporal lobe epilepsy after pretreatment with either a sustained release formulation of valproate (Depakine Chrono; 5 patients), the conventional formulation of valproate (Depakine; 6 patients) or valpromide (Depamide; 2 patients). With a mean serum value for all 13 patients of 32.3 micrograms/g valproate, the mean brain/serum ratio was 15.1% (SD 6.1%). The valproate concentration of the hippocampus was significantly higher than that of the amygdala and patients who had the sustained release formulation had significantly higher valproate concentration in the CSF and in the hippocampal formation than those patients who had the conventional valproate. Since a few patients had tumors, whereas others had varying degrees of gliosis, it cannot be ruled out that these differences are the result of different histopathological conditions with related differences in blood-brain barrier functions.

Adolescent↗
PubMed1991

Selective amygdalohippocampectomy: indications and follow-up.

Selective amygdalohippocampectomy (AHE) offers a real chance of cure only in patients with well-defined, precisely localized "epileptogenic area", i.e. seizure focus. Therefore, a priori only a small proportion of all patients with epilepsy can meet the criteria for selective surgical interventions. From the evidence in patients meeting the criteria for AHE, we conclude that this technique is to be preferred to the "standard" anterior temporal lobectomy and represents a more selective but still effective surgical treatment of epilepsy.

Adult↗
PubMed1991

Temporal lobe epilepsy, sleep and arousal: stereo-EEG findings.

By means of combined surface and depth EEG recordings (32 channels) and split-screen video-monitoring (infra red light), complete all-night sleep studies were carried out in drug-resistant epileptics suffering from complex partial seizures. These data were supplemented by (1) all-night sleep recordings from three patients who had chronically implanted electrodes in the periaqueductal grey matter because of severe pain problems, and (2) incomplete sleep recordings (day-time or only partial night) from other drug-resistant epileptics, who underwent chronic stereo-electroencephalographic (SEEG) examination in view of the surgical therapy. The following questions of importance were studied and the results were compared between different patient groups. 1. Relationship between overt clinical seizures or subclinical seizure discharges and the time course of night sleep. 2. Topic behavior of the epileptogenic area and different propagation phenomena of interictal spikes and ictal seizure discharges in different sleep stages. 3. Influence of arousal on the average spike incidence of any location with special attention to the different (slow and fast) components of the K-complex and their association with spiky elements, thus testing the hypothesis that the K-complex might serve as a vehicle for the seizure discharge. 4. Incidence and time-relationship of seizure discharges with clinical overt awakenings.

Adult↗
PubMed1990

Selection criteria for surgery--clinical features and EEG including invasive techniques.

Preconditions, selection criteria for surgical treatment of epilepsy and some aspects of the presurgical evaluation are discussed. Identification of those patients who will profit from epilepsy surgery, exact localization of the seizure generating structures, and evaluation of the potential risks of the proposed operation are the main goals of the preoperative diagnostic procedures. The localizational value of certain seizure patterns and ictal clinical signs and symptoms is reviewed and illustrated with symptoms provoked by electrical stimulation of the brain.

Brain Mapping↗
PubMed1990

The Zürich amygdalo-hippocampectomy series: a short up-date.

Selective amygdalohippocampectomy was developed as a surgical treatment for temporal lobe epilesy with a well-defined unilateral mesiobasal limbic seizure onset. Since 1975, 236 patients have been operated on in Zürich. We briefly summarize recent studies on the seizure outcome with analysis of the postoperative long-term fluctuations in relation to postoperative anticonvulsant drug treatment, on the underlying neuropathology, and on the relationships between magnetic resonance scanning estimates of total volume of the removed tissue and the resection scores of amygdala, hippocampus and parahippocampus gyrus.

Adult↗
PubMed1990

Neuropathology of a human hippocampus following long-term treatment with vigabatrin: lack of microvacuoles.

Vigabatrin (gamma-vinyl-GABA), an irreversible inhibitor of gamma-aminobutyric acid transaminase, has been reported to be effective in the treatment of refractory epilepsies. Animal toxicology studies have shown that long-term application of vigabatrin induces intramyelinic edema and microvacuolation of the white matter in non-primate species. However, clinical and neuropathological studies of patients exposed to long-term vigabatrin treatment have, so far, provided no evidence for microvacuolation in the human brain. We report on the histopathological findings of selective amygdalohippocampectomy specimens from a 36-year-old female patient treated with vigabatrin for a period of 11.5 months, and from 2 control patients with chronic refractory temporal lobe seizures. All specimens showed changes associated with chronic epileptic seizures including focal neuronal loss and hippocampal gliosis. Microvacuoles, intramyelinic edema or other manifestations of neurotoxic damage were not observed in vigabatrin exposed tissue, supporting the view that this compound may not exert hippocampal neurotoxicity in humans.

Adult↗
PubMed1990

[Obstructive sleep apnea syndrome in a child with trisomy 21].

Pulmonary hypertension without any cardiovascular malformation was diagnosed by heart catheterization in a 4 year old girl with trisomy 21. A suspected obstructive sleep apnea syndrome was confirmed by polysomnography which revealed numerous obstructive apneas and hypopneas (apnea-index 23/h) with marked oxygen desaturation and a disturbed sleep pattern. Three months after adenotonsillectomy the mother reported her daughter having a quiet sleep without snoring. Polysomnography did not show any apnea nor any oxygen desaturation below 90%. A decrease of the pulmonary artery pressure was documented. Facial dysmorphias and muscle hypotonia predispose patients with trisomy 21 to obstructive sleep apnea, especially if hypertrophy of tonsills and adenoids coexist. Frequent arousals and hypoxia during sleep can result in failure to thrive and pulmonary hypertension. These consequences can be prevented by early diagnosis and treatment.

Adenoidectomy↗
PubMed1989

[Long-term electroencephalography follow-up of patients with selective amygdaloid-hippocampectomy].

The EEGs of 149 patients with drug-resistant psychomotor epilepsy were analysed before and after amygdalohippocampectomy. The extent of the pre- and postoperative EEG abnormalities was compared. In particular we were interested whether there is a difference in patients with a structural lesion compared to those with no structural lesion, and if so, in which EEG-parameters the difference lies (background activity, homo- and contralateral focal slowing, homo- and contralateral epileptogenic focus, generalized epileptiform abnormalities). Furthermore we studied whether the postoperative clinical outcome correlates with the pre- and postoperative EEG-parameters. In patients with a structural lesion the homolateral focal slowing is preoperatively more pronounced than in patients with no structural lesion. In patients with no structural lesion all other preoperative EEG-parameters are more pathological. The preoperative EEG-parameters are only of limited predictive value for the clinical outcome. The amount of the improvement of postoperative EEG-parameters correlates well with the clinical outcome.

Adult↗
PubMed1989

[Long-term EEG follow-up of 30 patients with large resections in severe extra-temporal epilepsy].

This study presents postoperative scalp EEG-findings of 30 patients operated on for drug resistant epilepsies of extratemporal origin. The primary epileptogenic area was preoperatively defined by means of stereo-electroencephalography (SEEG). The amount and the distribution of postoperatively recorded epileptiform abnormalities were compared to the seizure outcome, to the location and extent of the resection and to the preoperative SEEG results. Furthermore the relations between results of preoperative SEEG-evaluation, the location and size of the therapeutic resection, and the clinical outcome were studied. The clinical outcome does not correspond with the amount of the epileptiform abnormalities in the postoperative scalp-EEGs. In most cases the location of the persisting epileptiform discharges is related to the borders of the resection. The retrospective evaluation of the preoperative SEEG-findings with a view towards their relation to the size of the resection revealed the following result: the better the preoperative definition of the epileptogenic area in terms of location and size, and the more radical the surgical excision of the preoperatively defined primary epileptogenic area, the better the clinical seizure outcome.

Adult↗
PubMed1988

Selective amygdalo-hippocampectomy for temporal lobe epilepsy.

Greater precision in the identification of seizure-initiating structures and preferential pathways of seizure spread has enabled us to classify complex partial seizures into subtypes. The mediobasal limbic subtype is the most important of these. Because of the paramount importance of amygdala and hippocampus in the majority of patients with temporal lobe epilepsy, we initiated so-called "selective" amygdalo-hippocampectomy (AHE) as an alternative to conventional temporal lobectomy for the treatment of medically intractable mediobasal temporal lobe epilepsy. To date, 181 patients have been operated on using this microsurgical approach. Fifty-two of them had no detectable morphological lesion preoperatively. These were studied either by stereoelectroencephalography (SEEG) (n = 42) or using foramen-ovale (FO) electrodes (n = 10). Mean follow-up for this group was 47 (6-143) months. Sixty-two percent are seizure-free, 10% have only rare seizures, and worthwhile improvement occurred in another 15%. There was no improvement in 13%. Antiepileptic drugs have been discontinued in 21%; the remainder receive one or more drugs. Good postoperative seizure outcome related to the initial seizure-onset locus being exclusively within the resected structures. "Palliative" AHE is nevertheless an option in those cases in whom the primary focus lies in or close to indispensable neocortex (e.g., speech area) and in whom a secondary pacemaker role of the amygdala-hippocampus complex has been demonstrated. Further factors influencing outcome include the presence of structural abnormality (especially of hippocampal sclerosis), age at seizure onset, preoperative duration of seizures, and postoperative EEG findings. In patients with a good seizure outcome, learning and memory performance increased, especially for material specific for the nonoperated hemisphere. We conclude that temporal lobe epilepsy with mediobasal limbic seizures is preferably treated surgically by selective amygdalo-hippocampectomy rather than "standard" temporal lobectomy.

Amygdala↗