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Andreas Schulze-Bonhage

Publications and source records attributed to Andreas Schulze-Bonhage.

At least 19 recordsLinked to original sources
PubMed2006

Seizure prediction: the impact of long prediction horizons.

Several procedures have been proposed to be capable of predicting the occurrence of epileptic seizures. Up to now, all proposed algorithms are far from being sufficient for a clinical application. This is, however, often not obvious when results of seizure prediction performance are reported. Here, we discuss impacts of long prediction horizons with respect to clinical needs and the strain on patients by analyzing long-term continuous intracranial electroencephalography data.

Adolescent↗
PubMed2006

Spatio-temporal patient-individual assessment of synchronization changes for epileptic seizure prediction.

OBJECTIVE: Abnormal synchronization of neurons plays a central role for the generation of epileptic seizures. Therefore, multivariate time series analysis techniques investigating relationships between the dynamics of different neural populations may offer advantages in predicting epileptic seizures. METHODS: We applied a phase and a lag synchronization measure to a selected subset of multicontact intracranial EEG recordings and assessed changes in synchronization with respect to seizure prediction. RESULTS: Patient individual results, group results, spatial aspects using focal and extra-focal electrode contacts as well as two evaluation schemes analyzing decreases and increases in synchronization were examined. Averaged sensitivity values of 60% are observed for a false prediction rate of 0.15 false predictions per hour, a seizure occurrence period of half an hour, and a prediction horizon of 10 min. For approximately half of all 21 patients, a statistically significant prediction performance is observed for at least one synchronization measure and evaluation scheme. CONCLUSIONS: The results indicate that synchronization changes in the EEG dynamics preceding seizures can be used for seizure prediction. Nevertheless, the underlying pathogenic mechanisms differ and both decreases and increases in synchronization may precede epileptic seizures depending on the structures investigated. SIGNIFICANCE: The prediction method, optimized values of intervention times, as well as preferred brain structures for the EEG recordings have to be determined for each patient individually offering the chance of a better patient-individual prediction performance.

Adolescent↗
PubMed2006

Hippocampal and neocortical gamma oscillations predict memory formation in humans.

Functional magnetic resonance imaging (fMRI) of the human brain has shown that the hippocampus and the left temporal and frontal cortices play a key role in the formation of new verbal memories. We recorded electrical activity from 2349 surgically implanted intracranial electrodes in epilepsy patients while they studied and later recalled lists of common words. Using these recordings, we demonstrate that gamma oscillations (44-64 Hz) in the hippocampus and the left temporal and frontal cortices predict successful encoding of new verbal memories. This increase in gamma oscillations was not seen in other frequency bands, whose activity generally decreased during successful memory formation. These findings identify a role for gamma oscillations in verbal memory formation with the hippocampus and the left temporal and frontal cortices, the same regions implicated using noninvasive fMRI recording methods.

Adaptation, Physiological↗
PubMed2006

Clinical characteristics in focal cortical dysplasia: a retrospective evaluation in a series of 120 patients.

Focal cortical dysplasias (FCDs) are increasingly diagnosed as a cause of symptomatic focal epilepsy in paediatric and adult patients. However, little is known about the clinical characteristics of epilepsy in these patients. In order to elucidate the clinical characteristics of their epilepsy, 120 pharmacoresistant patients including children and adults with histologically proven FCD were studied retrospectively. Age at seizure onset was analysed in the total group and compared between subgroups with different localization and different histological subtypes of FCD. The role of febrile seizures with respect to dual pathology was investigated. Seizure semiology was analysed focusing on initial seizure type and change of seizure semiology during the course of disease. Finally, transient responsiveness to antiepileptic drug therapy was studied. In the majority of patients, epilepsy began in the first 5 years of life. However, onset of epilepsy could also occur in the second or third decade until the age of 60. Age at epilepsy onset was not significantly different between temporal, extratemporal and multilobar localization of FCD. Patients without cytoarchitectural abnormalities (mild malformations of cortical development, FCD 1a according to Palmini) had significantly later epilepsy onset (P= 0.001) compared with patients with cytoarchitectural abnormalities (FCD 1b, 2a and 2b according to Palmini). In patients with additional hippocampal sclerosis (dual pathology) febrile seizures were significantly more frequently reported (P = 0.02) than in patients without dual pathology. Moreover, patients with dual pathology and febrile seizures significantly more frequently presented with severe hippocampal sclerosis (Wyler Grade 3-4) as compared with patients with dual pathology in the absence of febrile seizures (P = 0.03). First observed seizures were mainly tonic or generalized tonic-clonic. A change of seizure semiology seemed to be age-dependent and occurred between the age of >1 and 14 years. About 15.8% of the patients presented with status epilepticus during the course of disease. About 17% of the patients showed transient responsiveness (> or =1 year seizure freedom) to antiepileptic drug therapy either after initial therapy (50%) or later in the course of epilepsy (50%). Patients with FCD represent a heterogeneous group. Different age at epilepsy onset and transient responsiveness to antiepileptic drugs in approximately 17% of patients may reflect different dynamics in epileptogenicity of the underlying FCD. Dual pathology may be associated with different pathomechanisms in patients with and without febrile seizures.

Adolescent↗
PubMed2006

Gender-related differences in lateralization of hippocampal activation and cognitive strategy.

Gender-related differences in brain activation patterns and their lateralization associated with cognitive functions have been reported in the field of language, emotion, and working memory. Differences have been hypothesized to be due to different cognitive strategies. The aim of the present study was to test whether lateralization of brain activation in the hippocampi during memory processing differs between the sexes. We acquired functional magnetic resonance imaging data from healthy female and male study participants performing a spatial memory task and quantitatively assessed the lateralization of hippocampal activation in each participant. Hippocampal activation was significantly more left lateralized in women, and more right lateralized in men. Correspondingly, women rated their strategy as being more verbal than men did.

Adult↗
PubMed2006

Human neocortical oscillations exhibit theta phase differences between encoding and retrieval.

We analyzed intracranial brain activity recorded from human participants during the performance of a working-memory task. We show that 6-13 Hz activity exhibits consistent phase across trials following experimental stimuli, and that this phase significantly differs between study and test stimuli. These findings suggest that oscillatory phase reflects the encoding-retrieval state of neural networks, supporting predictions of recent models of memory.[Hasselmo, M.E., Wyble, B.P., and Bodelon, C., 2002. A proposed function for hippocampal theta rhythm: Separate phases of encoding and retrieval enhance reversal of prior learning. Neural Comput. 14 793-817.; Judge, S.J., Hasselmo, M.E., 2004. Theta rhythmic stimulation of stratum lacunosum-moleculare in rat hippocampus contributes to associative LTP at a phase offset in stratum radiatum. J. Neurophys. 92 1516-1624.].

Adolescent↗
PubMed2006

Seizure anticipation by patients with focal and generalized epilepsy: a multicentre assessment of premonitory symptoms.

PURPOSE: To assess subjective seizure anticipation in patients with focal and generalized epilepsy. METHODS: Five hundred consecutively recruited out-patients (251 male, 249 female, mean age 38.1 year) from three German tertiary epilepsy referral centres filled out questionnaires regarding subjective anticipation of seizures by at least 30 min and to timing and semiologic characteristics of their premonitory symptoms versus those of ictal phenomena. Patients were not regarded as having prodromi if the semiology of symptoms reported long before a seizure was identical to auras. RESULTS: 6.2% of patients reported that they were able to anticipate seizures. Premonitory symptoms were classified as stereotyped in all but one patient. An intraindividual semiologic analysis showed that the majority of these patients had symptoms, which were distinct from ictal experiences during auras. Seizure anticipation was reported both by patients with focal and idiopathic generalized epilepsy. The median estimated time interval between occurrence of premonitory symptoms and seizure onset was 90 min. CONCLUSIONS: This study gives evidence that both patients with focal and idiopathic generalized epilepsy may subjectively anticipate the occurrence of epileptic seizures. Premonitory symptoms are distinct from auras in terms of semiology and time of occurrence. The lower percentage of patients regarded as having premonitory symptoms as compared to some earlier reports may be related to stricter criteria and to the exclusion of auras, which could directly evolve into seizures, and other ictal events. Premonitory symptoms occur at similar periods prior to seizures as anticipatory EEG-changes have been reported using methods from time series analysis.

Adult↗
PubMed2006

Precuneus is involved in allocentric spatial location encoding and recognition.

Using a declarative memory paradigm, the anatomical correlates of spatial location encoding and retrieval in the healthy human brain as reflected by BOLD fMRI were investigated. During encoding, subjects were instructed to view and keep in mind different locations of an object on a platform seen from different viewpoints in virtual 3D. In retrieval trials, subjects had to recognize previously learned object locations. Comparing activation patterns associated with encoding and recognition on a voxel-by-voxel basis, we found regions in the precuneus bilaterally activated by both processes. To our knowledge, this is the first study that directly compared human brain activation patterns associated with allocentric encoding and retrieval of spatial locations in virtual 3D. Our results provide further information concerning the role of the precuneus in declarative memory processes, pointing to precuneus involvement in encoding and retrieval of spatial locations.

Adult↗
PubMed2006

Testing statistical significance of multivariate time series analysis techniques for epileptic seizure prediction.

Nonlinear time series analysis techniques have been proposed to detect changes in the electroencephalography dynamics prior to epileptic seizures. Their applicability in practice to predict seizure onsets is hampered by the present lack of generally accepted standards to assess their performance. We propose an analytic approach to judge the prediction performance of multivariate seizure prediction methods. Statistical tests are introduced to assess patient individual results, taking into account that prediction methods are applied to multiple time series and several seizures. Their performance is illustrated utilizing a bivariate seizure prediction method based on synchronization theory.

Algorithms↗
PubMed2006

Noninvasive source localization of interictal EEG spikes: effects of signal-to-noise ratio and averaging.

Source localization using single current dipoles estimates equivalent centers of the spiking gray matter. The extent of the active cortex, however, is difficult to assess from scalp EEG because of the unknown individual volume conduction. The spatial scatter of dipole localizations of single spikes has been proposed as a measure of extent. Single spike localization, however, is strongly dependent on the signal-to-noise ratio (SNR), that is, the ratio of spike and background EEG amplitudes. On the other hand, averaging of all spikes yields only the localization of equivalent centers of activity. We investigated the influence of SNR and multiple subaverages on the estimation of spatial extent by comparing the localization scatter of 100 single spikes in 27 spike types of 25 epilepsy patients with 1000 different subaverages computed by random sampling and bootstrapping. Averaging increased SNR and therefore allowed for localization not only at the spike peak but also during spike onset when less cortex is active. In several subjects with known cortical lesions, the single spike scatter considerably exceeded the lesion. Single dipole scatter was highly correlated with SNR (r = -0.83, P < 0.0001) and was greatly reduced when analyzing multiple subaverages of 10, 25, 50, and 100 spikes. Thus, we found a dominant role of the SNR on the estimated extent and improvement by scatterplots based on the dipole localization of randomly sampled subaverages.

Action Potentials↗
PubMed2006

Cognitive functions in juvenile and adult patients with gelastic epilepsy due to hypothalamic hamartoma.

PURPOSE: To describe extend and severity of cognitive deficits in juvenile and adult patients with gelastic seizures and hypothalamic hamartoma (HH) and to analyze the impact of epilepsy-related variables on cognitive performance. METHODS: Thirteen juvenile and adult patients (mean age, 25 years; seven men) underwent comprehensive neuropsychological testing assessing intellectual performance, attention and executive functions, verbal and visual memory, and visuospatial abilities. RESULTS: Intellectual abilities ranged from moderate mental retardation to good average performance; 54% of the patients displayed below-average global intellectual abilities. Attentional and executive functions were impaired in 23% to 46% of the patients. Below-average visuospatial capabilities were observed in 39% of the cases. Memory functions were impaired regarding both visual (77%) and verbal learning (62%). Nonparametric correlation analysis revealed a significant relation between monthly partial seizure frequency and reduced cognitive flexibility and reduced performance in mental rotation. In addition, HH volume was significantly negatively correlated with cognitive flexibility, whereas age at onset and duration of epilepsy did not show significant correlation to cognitive performance. CONCLUSIONS: More than half of the adult patients with gelastic seizures and HH displayed deficits in a broad range of cognitive functions, expressed mostly in visual and verbal learning and memory. Some of the deficits could be shown to correlate with disease-related characteristics representing the severity of the epilepsy or the size of the underlying lesion. These findings prompt for a longitudinal investigation of the development of these cognitive deficits to analyze further the relevant factors contributing to this wide spectrum of cognitive impairments.

Adolescent↗
PubMed2006

Assessment of the long-term effects of epilepsy surgery with three different reference groups.

PURPOSE: It is difficult to validly assess the long-term effect of epilepsy surgery. Here, this is attempted by comparing the outcome of surgically treated pharmacoresistant epilepsy patients to three different nonoperated comparison groups regarding seizure control, antiepilepsy drug (AED) usage, and health related quality of life (QOL). METHODS: One hundred thirty-one operated patients (group 1, mean follow-up since presurgical assessment 6.9 years), 105 patients awaiting presurgical assessment (group 2, mean follow-up after assignment to waiting list 0.8 years), 99 patients considered to be presurgical candidates who chose to withdraw from waiting for presurgical assessment (group 3, mean follow-up after assignment to waiting list 5.5 years), and 49 patients who were not deemed to be eligible for surgery after comprehensive assessment (group 4, mean follow-up since presurgical assessment 6.5 years) were studied. The patients completed a questionnaire on seizures, AED usage, and QOL (ESI-55). RESULTS: The surgical patients had a better outcome than all three comparison groups regarding seizure frequency, seizure freedom rate, and number of AEDs used. They scored higher than groups 2, 3, and 4 on 7/11, 6/11, and 3/11 ESI-55 domains, respectively. CONCLUSIONS: The superior long-term outcome of the operated patients was most marked if compared to the patients awaiting surgery. This is compatible with the assumption that patients present for presurgical candidacy selection and assessment at a "nadir" of their disease course. After several years, a regression to the mean occurs which reduces (but does not abolish) the differences between nonoperated and operated patients.

Adult↗
PubMed2006

Do false predictions of seizures depend on the state of vigilance? A report from two seizure-prediction methods and proposed remedies.

PURPOSE: Available seizure-prediction algorithms are accompanied by high numbers of false predictions to achieve high sensitivity. Little is known about the extent to which changes in EEG dynamics contribute to false predictions. This study addresses potential causes and the circadian distribution of false predictions as well as their relation to the sleep-wake cycle. METHODS: In 21 patients, each with 24 h of interictal invasive EEG recordings, two methods, the dynamic similarity index and the mean phase coherence, were assessed with respect to time points of false predictions. Visual inspection of the invasive EEG data and additional scalp electroencephalogram data was performed at times of false predictions to identify possible correlates of changes in the EEG dynamics. RESULTS: A dependency of false predictions on the time of day is shown. Renormalized to the duration of the period patients are asleep and awake, 86% of all false predictions occurred during sleep for the dynamic similarity index and 68% for the mean phase coherence, respectively. Combining two reference intervals, one during sleep and one in an awake state, the dynamic similarity index increases its performance by reducing the number of false predictions by almost 50% without major changes in sensitivity. No obvious dependence of false predictions was noted on visible epileptic activity, such as spikes, sharp waves, or subclinical ictal patterns. CONCLUSIONS: Changes in the EEG dynamics related to the sleep-wake cycle contribute to limits of specificity of both seizure-prediction methods investigated. This may provide a clue for improving prediction methods in general. The combination of reference states yields promising results and may offer opportunities to increase further the performance of prediction methods.

Adolescent↗
PubMed2005

Epileptogenicity of cortical dysplasia in temporal lobe dual pathology: an electrophysiological study with invasive recordings.

Hippocampal sclerosis is often associated with macroscopic or microscopic dysplasia in the temporal neocortex (TN). The relevance of such a dual pathology with regard to epileptogenesis is unclear. This study investigates the role of both pathologies in the generation of ictal and interictal activity. Ictal (113 seizures) and interictal data from invasive EEG recordings with simultaneous depth electrodes in the hippocampus and subdural electrodes over the TN were analysed retrospectively in 12 patients with variable degrees of hippocampal sclerosis and different types of histologically confirmed temporal cortical dysplasia [all male, age at epilepsy onset <1-29 years (mean 9.6 years), age when invasive recordings were performed 6-50 years (mean 28.2 years)]. Of the seizures 41.3% arose from the amygdala/hippocampus complex (AHC), 34.7% from the TN, 22% were simultaneously recorded from AHC and TN (indeterminate seizure onset), and 2% from other regions. In three patients, seizure onset was recorded only from the AHC. In patients with severe hippocampal sclerosis only 12% of the seizures arose from the TN, whereas in patients with mild hippocampal sclerosis 58% arose from the TN. The type of cortical dysplasia, however, did not predict seizure onset in the AHC or TN. Propagation time from the TN to the AHC tended to be shorter (mean 7.4 s) than vice versa (mean 13.7 s). The most common initial ictal patterns in the AHC were rhythmic beta activity (<25 Hz) and repetitive sharp waves, and in the TN were fast activity (>25 Hz) and repetitive sharp waves. The interictal patterns over the TN were similar to those seen over extratemporal focal cortical dysplasias. Simultaneous recordings from the hippocampus and the TN strongly suggest that dysplastic tissue in the TN is often epileptogenic. The quantitative contribution of the hippocampus to seizure generation corresponded with the degree of hippocampal pathology, whereas different subtypes of cortical dysplasia did not affect its relative contribution to seizure generation and even mild forms of dysplasia were epileptogenic.

Adolescent↗
PubMed2005

Comparing information about arm movement direction in single channels of local and epicortical field potentials from monkey and human motor cortex.

Cortical field potentials have been used for decades in neurophysiological studies to probe spatio-temporal activity patterns of local populations of neurons. Recently, however, interest in these signals was spurred as they were proposed as potential control signals for neuronal motor prostheses, i.e., for devices fit to record and decode brain activity to restore motor functions in paralyzed patients. Little is known, however, about the functional significance of these cortical field potentials. Here we compared information about arm movement direction in two types of movement related cortical field potentials, obtained during a four direction center-out arm reaching paradigm: local field potentials (LFPs) recorded with intracortical micro-electrodes from monkey motor cortex, and epicortical field potentials (EFPs) recorded with macro-electrode arrays subdurally implanted on the surface of the human cerebral cortex. While monkey LFPs showed a typical sequence of positive and negative potential peaks, an initial negative peak was the most salient feature of human EFPs. Individual contralateral LFPs from the monkey motor cortex carried approximately twice as much decoded information (DI) about arm movement direction (median 0.27 bit) as did individual EFPs from the contralateral hand/arm area of primary motor cortex in humans (median 0.12 bit). This relation was similar to the relation between median peak signal-to-noise ratios for directional modulation of movement related potentials (MRPs) of both types of signals. We discuss possible reasons for the observed differences, amongst them epi- vs. intracortical recording and the different electrode dimensions used to measure EFPs and LFPs.

Action Potentials↗
PubMed2005

Trigeminal pain under vagus nerve stimulation.

Three epilepsy patients treated by cyclic continuous vagus nerve stimulation (VNS) experienced trigeminal pain during the periods of stimulation, which was reported as toothache in the left lower jaw, ipsilateral to the side of stimulation. The symptom occurred with a latency of days to weeks following an increase in stimulation current intensity (SCI). Trigeminal pain was reversible with decrease in SCI, or subsided due to habituation. These findings show that clinically relevant effects of VNS on nociception may occur. Because of the late onset and variable form of this side effect, trigeminal pain may not be regarded as VNS-related which may result in unnecessary diagnostic and therapeutic procedures.

Aged↗
PubMed2005

Enhanced visualization of blurred gray-white matter junctions in focal cortical dysplasia by voxel-based 3D MRI analysis.

PURPOSE: Focal cortical dysplasia (FCD), a frequent cause of partial epilepsy, is often associated with blurring of the gray-white matter junction in magnetic resonance images (MRI). To improve the recognition and delineation of FCD we developed a novel voxel-based image post-processing method for enhanced visualization of blurred gray-white matter junctions. METHODS: Using standard algorithms of statistical parametric mapping software (SPM99) a T1-weighted MRI volume data set is normalized and segmented. The distribution of gray and white matter is analyzed on a voxelwise basis and compared with a normal database. Based on this analysis, a three-dimensional feature map is created which highlights brain areas with blurred gray-white matter transition. This method was applied to the MRI data of 25 epilepsy patients with histologically proven FCD. RESULTS: In 18/25 patients the new feature maps clearly showed that the dysplastic lesions were accompanied by blurring of the gray-white matter junction. Combined with a formerly published method of voxel-based 3D MRI analysis, 21/25 FCD lesions were shown to be associated with either blurring or abnormal extension of gray matter beyond the normal cortical ribbon, including four cases with lesions not or incompletely recognized on conventional MRI. CONCLUSIONS: The MRI post-processing presented here improves the visualization of FCD and may increase the diagnostic yield of MRI. Thereby, it provides a valuable additional diagnostic tool in the presurgical evaluation of epilepsy patients.

Adolescent↗