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  • 1
    ISSN: 1432-0533
    Keywords: Epilepsy ; Pathology ; Tumor ; Malformation ; Inflammation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The surgical treatment of chronic pharmacoresistant epilepsies is increasing rapidly. Although several studies have reported on histopathological findings in temporal lobe epilepsy, little is known about the surgical pathology of other seizure disorders. Here we report the histopathological fingings in 63 consecutive surgical specimens of patients who were operated for chronic pharmacoresistant epileptic seizures other than temporal lobe epilepsy (37 corticectomies, 19 functional hemispherectomies, 5 lobectomies, 1 multilobectomy, and 1 frontal lobe deafferentiation combined with a temporal lobectomy). There were structural lesions in 85.7% of the specimens. In 16 cases (25.4%) the predominant lesions were malformative (focal glioneuronal hamartias and hamartomas, vascular malformations, abundant ectopic neurons in the white matter, microgyria, and arachnoid cyst). Lesions indicating preor perinatal necrosis such as porencephaly, ulegyria, and congenital hemiatrophy were present in 7 cases (11.1%). Twelve specimens (19.0%) contained low-grade neoplasms (7 gangliogliomas, 3 astrocytomas, 1 oligoden-droglioma and 1 oligoastrocytoma). There were 3 cases of Rasuussen encephalitis, 1 specimen with atrophy and gliosis due to previous herpetic encephalitis and 1 case with an old abscess wall. Posttraumatic or postoperative changes were the predominant finding in 7 specimens (11.1%). In 7 patients there were only nonspecific changes such as cortical atrophy and gliosis or old hemorrhage. No structural alterations were identified in 9 specimens (14.3%). The findings suggest that the structural lesions observed in the great majority of the specimens were closely related to the pathogenesis of intractable seizures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 237 (1990), S. 416-419 
    ISSN: 1432-1459
    Keywords: Transcranial magnetic stimulation ; Motor evoked potentials ; Cortico-spinal system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Different physiological mechanisms of facilitation of latencies and amplitudes of magnetic motor evoked potentials (MEPs) were evaluated in a cohort of 140 healthy volunteers. The potentials were induced at the vertex and recorded at the abductor pollicis brevis. The aim of the present investigation was to compare physiological mechanisms which presumably facilitate motor pathways at the cortical level with those known to occur during contraction of small hand muscles. When compared with MEPs at rest, the maximum average decrease of latencies (1.5, SD 1.1 ms) as well as the highest increase of peak to peak amplitudes (2.6, SD 2.1 mV) was observed during exertion of a voluntary background force, at the muscle recorded from. Pre-innervation of a neighbouring muscle (abductor digiti minimi) led to a lesser average decrease of latencies by 1.0, SD 1.1 ms and an average increase of amplitudes by only 0.5, SD 1.5 mV. Non-specific manoeuvres, like sticking out the tongue or counting aloud, reduced mean latencies slightly by 0.4 ms, SD 0.8 ms and 0.3 SD 0.85 ms respectively, but increased amplitudes markedly by an average of 1.0, SD 1.6 mV and 0.8, SD 1.4mV respectively. It is concluded that facilitation of MEPs by non-specific manoeuvres occurs and must be taken into account when evaluating MEPs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1459
    Keywords: Key words Transcranial magnetic stimulation ; Repetitive ; Safety ; Intracranial EEG recording ; Epilepsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The safety of single and repetitive (paired and quadruple) focal transcranial magnetic stimuli as possible inducers of epileptic discharges or clinically manifest seizures was investigated in 21 patients with intractable epilepsy during invasive presurgical monitoring. Subdural and/or intracerebral depth electrodes had been implanted in close proximity to the suspected epileptogenic zone, and the anticonvulsant medication had been reduced. Focal transcranial magnetic stimuli were applied by a Magstim QuadroPulse magnetic stimulator over the hand area of the motor cortex ipsilateral to the epileptogenic focus at intensities of 120% and 150% of motor threshold and additionally as close as possible to the suspected epileptogenic zone at 40–100% of maximal stimulator output. Stimulation did not induce any complex partial or secondary generalized tonic-clonic seizures. One patient with hippocampal sclerosis experienced an aura associated with rhythmic electroencephalographic discharges restricted to the ipsilateral intrahippocampal depth electrode after stimulation over his left temporal lobe. This patient, however, also had frequent spontaneously occurring auras with focal ictal discharges originating from this hippocampus. Interictal discharges were not influenced significantly by single or repetitive magnetic stimuli. In conclusion, from this study there is no evidence that single or serial focal transcranial magnetic stimuli activate epileptogenic foci. At least four high-frequency repetitive stimuli of high intensity may thus be applied with a low risk of seizure induction even in patients with low seizure threshold.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1084
    Keywords: Brain, electrode position ; Epilepsy ; Three-dimensional MRI ; Three-dimensional reconstructions, MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Subdural strip electrodes or intracerebral electrodes are used to localise epileptic foci, which is imperative in epilepsy surgery. The precise positioning of the subdural electrodes, which is performed via a bore-hole, is difficult. Therefore their location in relation to the gyri and sulci has to be determined by radiological techniques. In this study, a three-dimensional (3D) MRI technique was used for the localisation of intracranial EEG electrodes in 17 patients suffering from severe epilepsy. A 3D gradient echo sequence with slices of 1 mm thickness was required for the assessment of the gyral anatomy of the brain surface. A short repetition time of 30 ms leads to diagnostic image quality and to an acceptable measurment time of about 15 min. Postprocessing with 3D surface reconstruction was performed using a Sun workstation. Three-dimensional reconstruction allows a more precise registration of the localisation of the EEG elctrodes and the simultaneous display of the adjacent brain structures. The incorrect placement of intracranial electrodes was readily detected in 3 patients. Three-dimensional MRI with 3D surface reconstruction proved superior for the assessment of electrocorticogram electrode localisation compared with two-dimensional imaging and CT.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Cortico-spinal connections in the rat ; Cortical motor areas ; Fast cortico-spinal fibres ; Cervical motoneurons ; Monosynaptic EPSP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rats the fast cortico-spinal pathway and its linkage to motoneurons of the distal portions of the forelimbs were examined by electrophysiological techniques: 1. Unilateral epicortical stimulation with a single pulse led to “flick”-like movements of corresponding muscle groups in the ipsi- and contralateral limbs. The effective stimulation points of the forelimbs were localized in fronto-central areas, those of the hindlimbs in centroparietal regions of the cortex. 2. After a single epicortical stimulus a cord dorsum potential appeared in all cervical, thoracal and lumbar segments, the early part of which could be shown to reflect the activity of fast cortico-spinal fibres conducting with a velocity of 60 m/s. The sites of origin of the cortical-spinal fibres mapped by antidromic stimulation exceeded the cortical regions determined as motor areas by orthodromic stimulation in parietal and occipital direction. 3. Single stimuli applied to the ipsi- and contralateral cortical surface caused a sequence of EPSP in all studied cervical motoneurons of the distal forearm. In nearly half of the impaled neurons the first EPSP was monosynaptic. Postsynaptic reactions following ipsi- and contralateral epicortical stimulation did not show significant differences both in flexor and extensor motoneurons. A minimum increase of the stimulus intensity beyond threshold level of the first EPSP led to action potentials in the early part of the synaptic response. The results demonstrate that in non-primates, showing skilled movements of the hand and digits, a powerful direct cortico-motoneuronal connection exists which is of predominant functional significance.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Cortico-spinal connections in the rat ; Lumbar motoneurons ; Oligosynaptic EPSP ; Oligosynaptic IPSP ; High frequency stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In rats the connections between cerebral cortex and lumbar motoneurons were studied by intracellular recording techniques: 1. After a single stimulus applied to the surface of the ipsi- and contralateral motor cortex (Elger et al., 1977) a sequence of postsynaptic potentials occurred consisting in an early and in a late component. 2. The early component of the postsynaptic response most often represented EPSP mediated by a pathway in which two or more neurons were interposed. In a minority of units monosynaptic EPSP appeared as well. In the case of disynaptic transmission interneurons were located at the segmental level. 3. In some motoneurons di- and multisynaptic IPSP were evoked by single ipsi- and contralateral stimuli. 4. The late component of the synaptic response represented by EPSP exceeded usually the early component in amplitude and often led to action potentials. 5. With increasing stimulus frequency the polysynaptic component fused to a sustained depolarization shift which was superimposed by the early part of the synaptic response. Parallel to the sustained neuronal depolarization the discharge frequency was transiently enhanced until spike generation failed. The results indicate that in lumbar motoneurons the polysynaptic PSP elicited by epicortical stimulation are of predominent functional significance.
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  • 7
    ISSN: 0942-0940
    Keywords: Epilepsy ; epilepsy surgery ; subdural electrode ; dept-electrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary From 1987 to 1992, invasive EEG studies using subdural strips, grids or depth electrodes were performed in a total of 160 patients with medically intractable epilepsy, in whom scalp EEG was insufficient to localize the epileptogenic focus. Dependent on the individual requirements, these different electrode types were used alone or in combination. Multiple strip electrodes with 4 to 16 contacts were implanted in 157 cases through burrholes, grids with up to 64 contacts in 15 cases via boneflaps, and intrahippocampal depth electrodes in 36 cases using stereotactic procedures. In every case, localization of the electrodes with respect to brain structures was controlled by CT scan and MRI. Visual and computerized analysis of extra-operative recordings allowed the localization of a resectable epileptogenic focus in 143 patients (89%), who subsequently were referred for surgery, whereas surgery had to be denied to 17 patients (11%). We did not encounter any permanent morbidity or mortality in our series. In our experience, EEG-monitoring with chronically implanted electrodes is a feasible technique which contributes essentially to the exact localization of the epileptogenic focus, since it allows nearly artefact-free recording of the ictal and interictal activity. Moreover, grid electrodes can be used for extra-operative functional topographic mapping of eloquent brain areas.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Limbic P300 potentials can be recorded within the mesial temporal lobes of patients with temporal lobe epilepsy (TLE). To delineate possible mechanisms of their generation and pathological alteration, we analysed limbic P300s in 55 TLE patients with and 29 without Ammon’s horn sclerosis (AHS) and correlated their amplitudes with neuronal cell counts in 30 histopathological specimens. Limbic P300 amplitudes were reduced on the side of the epileptogenic focus only in patients with AHS. Moreover, in AHS patients, limbic P300 latencies were prolonged bilaterally; and in patients with left-sided AHS, amplitudes were reduced bilaterally. Both findings suggest bilateral functional deficits in TLE with unilateral AHS. Limbic P300 areas correlated significantly with neuronal densities of dentate gyrus granule cells but not hippocampal pyramidal cells in the CA1–4 (cornu ammonis) subfields. This finding points to a potential mechanism for the bilateral effects of unilateral AHS as both dentate gyri exhibit strong reciprocal contralateral connectivity.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Epilepsiechirurgie ; Neuropsychologie ; Langzeitverlauf ; Psychosoziale Entwicklung ; Keywords Epilepsy ; Surgery ; Outcome Neuropsychology ; Long-term follow-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Little is known about the differential long-term outcome from surgical and nonsurgical therapy in patients with chronic epilepsy. In the present study, 161 surgically or nonsurgically treated patients with drug-resistant temporal lobe epilepsy (TLE) were re-evaluated according to a detailed clinical, neuropsychological, and psychosocial protocol with a mean follow-up interval of 58 months. Freedom from seizures was achieved in 64% of the surgical group; yet 23% of the nonsurgical patients became seizure-free as a result of modifications in drug therapy. Generally, socioeconomic development was poorer in nonsurgical than in surgical patients. Freedom from seizures, employment, and the absence of depression were significant determinants of better quality of life. As for neuropsychological outcome, verbal memory impairment was common after left-sided temporal resection; however, there was no evidence of a marked progression of cognitive impairment after the first postoperative year. In nonsurgical patients, too, cognitive capacities were surprisingly stable over time, although persisting seizures and good baseline performance predicted a poorer neuropsychological outcome.
    Notes: Zusammenfassung Über den differentiellen Langzeitverlauf operativ und konservativ behandelter Patienten mit Temporallappenepilepsie liegen bislang nur wenig Studien vor. Die vorliegende Arbeit stellt den klinischen, neuropsychologischen und psychosozialen Langzeitverlauf (mittleres Retestintervall: 58 Monate) von 161 operativ oder medikamentös behandelten Patienten dar. Bezüglich der Anfallskontrolle zeigt sich wie im Kurzzeitverlauf eine deutliche Überlegenheit der operativen Therapie (64% Anfallsfreiheit), allerdings wurde auch bei immerhin 23% der konservativ behandelten Patienten durch Umstellung der Antikonvulsiva ebenfalls noch Anfallsfreiheit erreicht. Auch die sozioökonomische Entwicklung war in der operativen Gruppe generell günstiger. Anfallsfreiheit, Arbeitstätigkeit und das Fehlen einer depressiven Symptomatik waren entscheidende Determinanten einer besseren Lebensqualität. In neuropsychologischer Hinsicht kommt dem verbalen Gedächtnisdefizit nach links temporaler Resektion die größte Bedeutung zu, es findet sich jedoch keine progrediente kognitive Verschlechterung nach dem ersten postoperativen Jahr. Auch die konservativ behandelten Patienten bleiben in ihrer kognitiven Leistungsfähigkeit recht stabil, wenn auch persistierende Anfälle und gute Leistungen in der Ausgangsuntersuchung als Prädiktoren einer kognitiven Verschlechterung im Langzeitverlauf identifiziert werden können.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1459
    Keywords: Prolactin ; Luteinizing hormone ; Magnetic stimulation ; Epileptic focus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Transient elevation of serum levels of prolactin has been observed following several types of epileptic seizures and after electrical stimulation of limbic temporal lobe structures via implanted electrodes. Transcranial magnetic stimulation has been found to selectively induce epileptiform afterdischarges in the epileptic focus of candidates for epilepsy surgery who suffered from temporal lobe epilepsy. Lateralized serial transcranial magnetic stimulation was therefore used and serum levels of prolactin or luteinizing hormone were measured to find if it could be used as a non-invasive diagnostic tool. The investigation was performed on six patients and five healthy volunteers. In the patients the induction of epileptiform potentials was continuously monitored via subdural electrodes. A transient surge of prolactin and luteinizing hormone was found in only one patient, in whom a complex partial seizure was induced. Thus, transcranial magnetic stimulation appeared not to be helpful for the lateralization of the (primary) epileptic focus during presurgical evaluation.
    Type of Medium: Electronic Resource
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