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Biomedical subjects

J P Lieb

Publications and source records attributed to J P Lieb.

At least 19 recordsLinked to original sources
PubMed1988

Computer enhancement of scalp-sphenoidal ictal EEG in patients with complex partial seizures.

Color topographic maps of scalp/sphenoidal ictal EEG records were computer-generated in 5 patients with medically refractory complex partial seizures of suspected temporal lobe origin. Seven ictal EEG records were analyzed by parsing them into a series of 1.28 sec epochs. User-interactive, computer techniques were utilized to replace eye movement and other artifactual segments in the peri-ictal records with nearby uncontaminated EEG segments. Artifact replacement techniques were designed to minimize or eliminate EEG discontinuities in those epochs in which artifact was removed. Significance probability maps consisting of z scores were constructed by comparing theta band power for each 1.28 sec epoch composing the peri-ictal period with the mean and standard deviation of theta power computed from a pre-ictal baseline period consisting of 50-75 epochs. The resulting maps were compared with available independent clinical measures in order to validate their usefulness. The independent measures consisted of non-invasive data (visual impressions of raw scalp/sphenoidal ictal EEGs and positron emission tomography) and invasive data (depth ictal recordings, pathological findings in resected temporal lobes, and surgical outcome). Ictal topographic maps appeared to either confirm or provide new localizing information in all 5 patients. In 3 of 5 patients, several seconds of localized theta suppression preceded localized theta augmentation during the peri-ictal period. The transition between the 2 states was very rapid (approximately 2 sec). The spatial locus of suppression was always in agreement with the spatial locus of augmentation. In general, the maps were considerably easier to interpret than the raw scalp/sphenoidal ictal EEGs: (1) Localized theta suppression in the maps was not evident from visual inspection of the raw ictal scalp/sphenoidal EEG. (2) Clear localized theta augmentation in the maps occurred well before the appearance of unambiguous phase reversals in the raw scalp/sphenoidal ictal EEG. (3) Mapping data were correctly lateralizing in 1 patient in whom visual interpretation of the raw scalp/sphenoidal ictal EEGs was considered non-localizing but often suggestive of a seizure origin in the hemisphere contralateral to that implicated by depth recordings, PET, and pathological data. These results suggest that topographic mapping of scalp/sphenoidal ictal EEGs in patients with complex partial seizures may eventually prove to be a useful adjunct to the interpretation of raw ictal recordings.

Brain↗
PubMed1987

Inter-hemispheric propagation of human mesial temporal lobe seizures: a coherence/phase analysis.

Intra- and inter-hemispheric propagation of ictal discharges was analyzed with computer techniques in 10 patients with complex partial seizures of mesial temporal lobe origin in whom depth electrodes had been stereotaxically implanted. Coherence and phase analysis of seizure discharges was used to detect the emergence of linear relationships between all possible pairs of surface and depth recording derivations both between and within hemispheres. This analysis included mesial temporal, lateral temporal, and frontal lobe sites during both the onset and inter-hemispheric propagation of 28 ictal episodes. Although strong intra-hemispheric coherences and linear phase spectra reliably emerged in both the epileptogenic and non-epileptogenic hemispheres during seizure onset and contralateral spread, these relationships were usually not observed for inter-hemispheric comparisons. Only 3 of 10 patients demonstrated some degree of consistency in the emergence of significant wideband coherences and linear phase spectra between left and right mesial temporal sites during the inter-hemispherics propagation of ictal discharges. Mesial temporal lobe sites which demonstrated such a relationship included the amygdala, pes hippocampi, and parahippocampal gyrus. In 7 of 10 patients, lateral temporal derivations were sampled during ictal events; the emergence of linear relationships between left and right lateral temporal derivations during inter-hemispheric propagation was observed for only two. Various frontal lobe sites were monitored in 3 of the 10 patients; the emergence of linear relationships was observed only between left and right orbitofrontal derivations in the one patient for whom this region was sampled. These results suggest that the hippocampal commissure, parts of the corpus callosum, and parts of the anterior commissure may be relatively unimportant for the inter-hemispheric propagation of mesial temporal seizures in man. Future studies in non-human primates may reveal that ictal discharges which originate in the mesial temporal region propagate preferentially via brain-stem pathways to contralateral homologous regions.

Amygdala↗
PubMed1986

Visual versus computer evaluation of thiopental-induced EEG changes in temporal lobe epilepsy.

Thiopental-induced EEG beta activity was analyzed both visually and by computer in 33 patients with complex partial epilepsy. Studies were done in 16 patients with depth electrodes in limbic structures and 17 patients with scalp and sphenoidal electrodes. The percentage of drug-induced change in beta activity was quantified by computer using spectral analysis. The statistical significance of asymmetries between homologous sites in the amount of change was determined. The spatial distribution of significant asymmetries was used for localization and compared with the results of independent visual analysis of the thiopental EEG. Concordance between computer and visual evaluation occurred in 10 of 17 scalp/sphenoidal and 10 of 16 depth electrode tests. The accuracy of visual and computer localization was determined by comparing them with locus of itcal EEG onset, interictal spikes, and positron emission tomography. In scalp/sphenoidal studies, computer analysis indicating asymmetry appeared more likely to correlate with independent clinical criteria than visual analysis. In depth studies the reverse appeared to be true. Scalp/sphenoidal tests yielded positive results in 25-30% of patients whereas depth electrode tests were positive in 50-70% of patients. The results indicate that computer analysis of surface thiopental tests is an accurate and useful supplement to visual evaluation of these tests.

Brain↗
PubMed1984

Distribution of pyramidal cell density and hyperexcitability in the epileptic human hippocampal formation.

Pyramidal cell densities in various regions of the anterior and posterior hippocampal formation were measured from en bloc temporal lobe resections and compared with presurgical stereoelectroencephalography (SEEG) data derived from depth electrodes in 12 patients with temporal lobe epilepsy. These data were compared with cell densities observed in four nonepileptic control patients. Patients who consistently exhibited anterior focal changes in the SEEG accompanying onset of ictus had cell densities that were selectively reduced in the anterior hippocampal formation but normal with respect to controls in the posterior hippocampal formation. Patients who exhibited more regional changes in the SEEG at onset of ictus had reduced cell densities in both the anterior and posterior hippocampal formation. Patients who exhibited focal spike activity in the anterior hippocampal formation as their predominant interictal SEEG pattern also had selectively reduced cell densities in the anterior hippocampal formation, while patients with widespread spiking throughout the hippocampal formation had reduced cell densities both anteriorly and posteriorly. These data support the concept that epileptogenesis occurs in or near those areas of epileptic hippocampus that are most damaged. Hippocampal sclerosis must be viewed as related to adjacent hyperexcitable or epileptogenic neurons and not solely as a passive result of repeated anoxia or ischemia.

Cerebral Cortex↗
PubMed1984

Temporal lobe volumetric cell densities in temporal lobe epilepsy.

Volumetric cell densities in 13 different subfields of the temporal lobe were calculated to test various hypotheses about mesial and lateral temporal lobe sclerosis in patients with complex partial epilepsy. In patients benefitting (primary group) from anterior temporal lobectomy (ATL), sclerosis was greater (fewer cells) in anterior than in posterior hippocampus. By contrast, the patients lacking full benefit (nonprimary group) from ATL had decreased numbers of neurons equally distributed from anterior to posterior hippocampus, indicating that zones of mesial temporal cell loss are linked to zones of epileptogenicity. These data support a model of focal hippocampal epilepsy originating from zones of cell loss and synaptic reorganization that is epileptic. There were no differences in cell densities in gyrus hippocampi or in lateral temporal gyri when patients with temporal lobe epilepsy and controls were compared. Hippocampal cell densities in mesial temporal lobe were not reduced in psychomotor epileptic patients with extrahippocampal foci consisting of foreign tissue. Variables in seizure histories were not correlated with Ammon's horn cell densities, indicating that most of the sclerosis preceded the seizures, which did virtually no significant further damage to hippocampus with repeated partial or generalized seizures.

Brain Diseases↗
PubMed1983

Temporo-spatial patterns of pre-ictal spike activity in human temporal lobe epilepsy.

The statistical properties of pre-ictal EEG spike activity in medial temporal lobe sites were analyzed in 6 patients with medically refractory complex partial seizures. A total of 24 1 h pre-ictal periods (2-6 periods per patient) were evaluated by quantifying the rate of occurrence of individual spatial patterns of spike activity derived from a subset (n = 6) of the recording channels. The channels chosen for analysis always included those medial temporal lobe sites which were documented to be most likely to initiate seizures, as well as their respective contralateral homologues. Each 1 h pre-ictal period was divided into 360 10 sec bins which were then visually classified into 1 of 64 possible spatial patterns of spike activity. These patterns, in turn, were grouped into 1 of 5 general spatial patterns and evaluated for trends across 3 20 min pre-ictal segments. Pooling these data across patients yielded the following results: (1) Focal patterns of spike activity tended to decline significantly in rate of occurrence several minutes prior to seizures, while the rate of independent contralateral patterns did not change. (2) The rate of occurrence of patterns of bilateral loosely coupled spike activity (involving focal and contralateral sites) increased significantly across the 20 min pre-ictal segments and was clearly augmented during the 20 min prior to seizures. These findings indicate that the degree of bilateral independence in medial temporal lobe spike activity tends to decrease several minutes prior to the localized onset of temporal lobe seizures; such changes may reflect the mechanisms responsible for the inter-ictal-ictal transition.

Action Potentials↗
PubMed1982

Changes in intelligence following temporal lobectomy: relationship to EEG activity, seizure relief, and pathology.

Pre- and posttemporal lobectomy measures of intelligence and memory in 36 patients with medically refractory complex partial seizures were compared with (1) various aspects of presurgical ictal and interictal EEG activity derived from surface and deep electrodes, (2) postlobectomy seizure relief, and (3) pathological findings in the resected lobe. With respect to interictal EEG data, bilaterally synchronous surface spikes (accompanied or unaccompanied by simultaneous deep spikes) and sharp waves were significantly correlated with lower prelobectomy intelligence scores and a drop in these scores following lobectomy. With respect to ictal EEG data, bilaterally synchronous and multifocal onsets were significantly correlated with a postlobectomy drop in intelligence scores. Patients with poor postlobectomy seizure relief tended to have lower presurgical intelligence scores and a drop in intelligence scores following lobectomy. The patients most likely to show a postlobectomy drop in intelligence were those demonstrating some combination of poor seizure relief, an absence of pathology in the resected specimen, or EEG signs indicative of poor seizure relief. Postlobectomy changes in intellectual status are therefore not necessarily exclusively attributable to the amount of postlobectomy seizure relief experienced by these patients, but might be due to a combination of factors.

Adult↗
PubMed1981

Correlation of criteria used for localizing epileptic foci in patients considered for surgical therapy of epilepsy.

Criteria for anterior temporal lobectomy, performed on seven patients with partial complex seizures, were derived from a battery of fourteen presurgical tests. Seven tests were routine studies aimed at identifying a focus of epileptic excitability, while seven were designed to reveal areas of focal functional deficit. Conflicting information was frequently obtained from the tests of epileptic excitability, suggesting that it is probably inaccurate to view patients with partial complex seizures as having a single epileptogenic focus. Presurgical evaluation must therefore be aimed at identifying the focus most responsible for the patient's habitual seizures. Tests of focal functional deficit provided useful nonconflicting confirmatory information in each of the seven patients studied. The most reliable information was obtained from depth electrode implantation, and this procedure should be considered essential except when all evidence of surface-recorded epileptic excitability, including ictal onset, and evidence of focal functional deficit agree.

Adult↗
PubMed1981

Surface and deep EEG correlates of surgical outcome in temporal lobe epilepsy.

Interictal and ictal EEG characteristics derived from limited surface montages and medial temporal lobe sites were compared with long-term seizure relief following anterior temporal lobectomy in 52 epileptics. Patients were classified into one of four surgical outcome groups, ranging from seizure free to no clinical improvement. For each patient, interictal records were analyzed according to deep and surface spike characteristics and background activity. Ictal records were analyzed according to the proportion of episodes initiated in a unilateral or bilaterally synchronous fashion, the proportion of surface or deep onsets, the variability of onset location, and the morphology of seizures onsets. Interictal EEG variables that correlates with surgical outcome included: (a) various types of bilaterally synchronous surface/deep spikes; (b) diffuse background slowing; (c) sharp waves; and (d) the presence of multiple independent deep spike patterns in the lobe chosen for resection. Relevant ictal EEG variables included: (a) episodes initiated in a bilaterally synchronous fashion; (b) variability in seizure onset location; (c) the proportion of precisely focal onsets from deep sites; (d) the proportion of surface onsets; and (e) the proportion of onsets from the side chosen for resection. Multivariate analysis of these data with linear, stepwise, discriminate analysis and adaptive, nonlinear, distribution-free pattern recognition demonstrated that: (a) both interictal and ictal EEG characteristics can independently predict surgical outcome at levels significantly better than chance; (b) ictal and interictal EEG data contain nonredundant information for making such predictions; and (c) nonlinear pattern recognition techniques are capable of deriving the most accurate rules for predicting the effects of surgery.

Adolescent↗
PubMed1981

Neuropathological findings following temporal lobectomy related to surface and deep EEG patterns.

Interictal and ictal characteristics of preoperative EEG recordings, derived from limited surface montages, and medial temporal lobe sites, were compared with the results of pathological studies done on resected lobes obtained from 44 patients with complex partial seizures. Pathological material was divided into four groups: (a) sclerosis (mesial temporal or restricted to pes hippocampi); (b) neoplasia (mainly hamartomas); (c) miscellaneous lesions; and (d) no significant lesions. Interictal EEG correlates of no pathology included bilaterally synchronous surface spikes (with or without simultaneous deep spikes) and independent surface spikes (with or without simultaneous deep spikes) on the sides of lobectomy. Ictal EEG correlates of no pathology included unilateral surface or surface/deep onsets, bilaterally synchronous surface onsets, more than one onset location, and suppression at onset. Focal onsets correlated with sclerosis. Frequent interictal spike activity in the nonlobectomized lobe and fast buildup at onset of ictus suggested neoplasia. Many of the EEG correlates of no pathology are known to correlate with poor postsurgical seizure relief, due probably in part to the fact that absence of pathology in the resected specimen is a negative prognostic sign. Patients with sclerosis could be distinguished from patients with no demonstrable pathology with 81% cross-validation classification accuracy using a distribution-independent, nonlinear classifier. Both interictal and ictal EEG measures were used by the classifier, and one may conclude that ictal and interictal EEG recordings contain nonredundant information for predicting the presence and type of underlying pathology.

Brain Neoplasms↗
PubMed1980

Sleep state and seizure foci related to depth spike activity in patients with temporal lobe epilepsy.

Depth spike activity was evaluated from medial temporal lobe sites using computer spike recognition techniques in all-night sleep records derived from 10 patients with medically refractory complex partial seizures. Sleep stages were classified into 1 of 4 groups: wakefulness, REM sleep, light sleep and deep sleep. Some disturbance in the periodicity of the sleep cycle was noted in most patients, but the relative proportions of REM sleep, light sleep and deep sleep were close to that reported for normals. Depth spike activity was observed to be most frequent in a majority of sites during deep sleep in 6 patients and during light sleep in 3 patients. In 1 patient equal numbers of sites showed maximal activation during light sleep and deep sleep. In 4 patients, certain sites in the more epileptogenic lobe demonstrated a maximal rate during waking or REM sleep. All patients reported in this study were considered to be suitable for temporal lobectomy. In contrast to the results obtained from a previous study, the side with the site demonstrating maximal mean spike rate did not necessarily correspond to the side chosen for lobectomy. Significant correspondence across patients between the more epileptogenic lobe and maximal spike rate was not found during waking and was further reduced during light sleep and deep sleep. The correspondence was, however, significant during REM sleep and for the side containing the site demonstrating the smallest activation in mean spike rate during light sleep or deep sleep relative to waking. These results indicate that an analysis of sleep induced changes in depth spike activity can be useful in improving predictions concerning epileptogenicity. Quantification of other aspects of the interictal EEG, such as background activity, may further improve such predictions.

Adolescent↗
PubMed1979

Procaine-induced seizures in epileptic monkeys with bilateral hippocampal foci.

Intravenous procaine HCl given at low doses (0.5-2.5 mg/kg) to two monkeys with bilateral alumina hippocampal foci depressed interictal spiking or had little effect. At 5.0 mg/kg unilateral limbic activation occurred. At 10.0 mg/kg unilateral or bilateral limbic activation and generalized seizures could be evoked within 3-10 min. At higher doses (15 and 20 mg/kg) bilateral limbic activation or brief (one min) generalized seizures occurred. The unilateral-onset psychomotor seizures were not identical to spontaneous psychomotor seizures, and the generalized seizures never occurred spontaneously in these monkeys. However, these results do indicate that procaine challenges may selectively activate limbic epileptogenic areas without activation of debilitating generalized tonic-clonic seizures.

Animals↗
PubMed1979

Effects of chronic cerebellar stimulation on chronic limbic seizures in monkeys.

No influences of chronic cerebellar stimulation were found in 10 different controlled experiments in 5 different monkeys with chronic alumina-induced psychomotor seizures. The stimulation parameters used were comparable to those used in human epileptics, and continuous daily EEG and behavioral monitoring allowed all seizures to be measured for daily frequency and duration over the several weeks of the experiments. Nocturnal seizures were similarly quantified in 3 monkeys to verify that cerebellar stimulation did not affect them. Motor cortex potentials evoked by cerebellar pulses confirmed that the stimulations were activating the cerebellum throughout the experiments, and measures of electrode access resistance and impedance verified that the electrodes remained in contact with the cerebellum. In one monkey given phenobarbital medication, interictal morbid behavior appeared to be improved by chronic stimulation of either cerebellum or dorsolateral frontal cortex, thus indicating an arousal influence of brain stimulation not due to cerebellum per se.

Aluminum Hydroxide↗
PubMed1978

Neuropsychologic correlates of depth spike activity in epileptic patients.

The statistical properties of depth spiking in the interictal EEG were assessed in 12 patients with intractable temporal lobe epilepsy in whom electrodes had been stereotactically implanted for diagnostic purposes. Prior to the implantation surgery each patient was administered a battery of neuropsychologic tests. Correlational analyses showed that the total amount of depth spike activity (TA) negatively correlated with measures of intelligence, while the laterality of the spike activity (LAT) appeared to be positively related to a memory score and the degree of psychologic independence. The results of this study are consistent with previous findings of a significant relationship between surface EEG recordings and performance. In addition, our data suggest a relationship between specific neuropsychologic functions and the patterns of in-depth EEG epileptiform discharges.

Adult↗
PubMed1978

A sample and hold amplifier system for stimulus artifact suppression.

A sample and hold amplifier system has been described which is capable of eliminating stimulus artifacts from a variety of biological recordings which would otherwise be impossible to interpret during electrical stimulation. Factors contributing to the prolongation of stimulus artifact are discussed in relation to the design requirements of this system. The application of this artifact suppression circuit to monitoring EEG seizures during electrical stimulation is demonstrated.

Amplifiers, Electronic↗