Space-oriented segmentation and 3-dimensional source reconstruction of ictal EEG patterns

OBJECTIVES Characterization of the EEG pattern during the early phase of a seizure is crucial for identifying the epileptic focus. The purpose of the present investigation was to evaluate a method that divides ictal EEG activity into segments of relatively constant surface voltage distribution, and to provide a 3-dimensional localization of the activity during the different segments. METHODS For each timepoint the electrical voltage distribution on the scalp (the voltage map) was determined from the digitized EEG recording. Through a spatial cluster analysis time sequences where the maps did not change much (segments) were identified, and a 3-dimensional source reconstruction of the activity corresponding to the different mean maps was performed using a distributed linear inverse solution algorithm. RESULTS Segments dominating early in seizure development were identified, and source reconstruction of the EEG activity corresponding to the maps of these segments yielded results which were consistent with the results from invasive recordings. In some cases a sequence of consecutive segments was obtained, which might reflect ictal propagation. CONCLUSIONS Segmentation of ictal EEG with subsequent 3-dimensional source reconstruction is a useful method to non-invasively determine the initiation and perhaps also the spread of epileptiform activity in patients with epileptic seizures.

[1]  I. Osorio,et al.  Real‐Time Automated Detection and Quantitative Analysis of Seizures and Short‐Term Prediction of Clinical Onset , 1998, Epilepsia.

[2]  C M Michel,et al.  Microstate segmentation of spontaneous multichannel EEG map series under diazepam and sulpiride. , 1995, Pharmacopsychiatry.

[3]  R M Leahy,et al.  EEG source localization and imaging using multiple signal classification approaches. , 1999, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[4]  F Wendling,et al.  A method to quantify invariant information in depth-recorded epileptic seizures. , 1997, Electroencephalography and clinical neurophysiology.

[5]  C M Michel,et al.  42-channel potential map series to visual contrast and stereo stimuli: perceptual and cognitive event-related segments. , 1992, International journal of psychophysiology : official journal of the International Organization of Psychophysiology.

[6]  S. Gonzalez-Andino,et al.  A critical analysis of linear inverse solutions to the neuroelectromagnetic inverse problem , 1998, IEEE Transactions on Biomedical Engineering.

[7]  T Landis,et al.  Spatio-temporal analysis of electric brain activity during semantic and phonological word processing. , 1998, International journal of psychophysiology : official journal of the International Organization of Psychophysiology.

[8]  A. C. Sanderson,et al.  Hierarchical modeling of EEG signals , 1980, IEEE Transactions on Pattern Analysis and Machine Intelligence.

[9]  C. N. Guy,et al.  Intracerebral propagation of interictal activity in partial epilepsy: implications for source localisation. , 1994, Journal of neurology, neurosurgery, and psychiatry.

[10]  Michael Unser,et al.  A review of wavelets in biomedical applications , 1996, Proc. IEEE.

[11]  D. Lehmann,et al.  Segmentation of brain electrical activity into microstates: model estimation and validation , 1995, IEEE Transactions on Biomedical Engineering.

[12]  G. Bergey,et al.  Time-frequency analysis using the matching pursuit algorithm applied to seizures originating from the mesial temporal lobe. , 1998, Electroencephalography and clinical neurophysiology.

[13]  L F Quesney,et al.  Depth electrode investigations in patients with bitemporal epileptiform abnormalities , 1989, Annals of neurology.

[14]  D Michael,et al.  Automatic EEG analysis: a segmentation procedure based on the autocorrelation function. , 1979, Electroencephalography and clinical neurophysiology.

[15]  C. Elger,et al.  Spatio-temporal dynamics of the primary epileptogenic area in temporal lobe epilepsy characterized by neuronal complexity loss. , 1995, Electroencephalography and clinical neurophysiology.

[16]  D Lehmann,et al.  Event-related electric microstates of the brain differ between words with visual and abstract meaning. , 1998, Electroencephalography and clinical neurophysiology.

[17]  I. Gath,et al.  On the tracking of rapid dynamic changes in seizure EEG , 1992, IEEE Transactions on Biomedical Engineering.

[18]  C M Michel,et al.  Intracerebral dipole source localization for FFT power maps. , 1990, Electroencephalography and clinical neurophysiology.

[19]  P. Hazemann,et al.  Handbook of Electroencephalography and Clinical Neurophysiology , 1975 .

[20]  Christoph M. Michel,et al.  Spatiotemporal Dynamics of Human Cognition. , 1999, News in physiological sciences : an international journal of physiology produced jointly by the International Union of Physiological Sciences and the American Physiological Society.

[21]  M. Fuchs,et al.  Linear and nonlinear current density reconstructions. , 1999, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[22]  J Gotman,et al.  Segmentation and classification of EEG during epileptic seizures. , 1998, Electroencephalography and clinical neurophysiology.

[23]  G Lantz,et al.  Frequency domain EEG source localization of ictal epileptiform activity in patients with partial complex epilepsy of temporal lobe origin , 1999, Clinical Neurophysiology.

[24]  F. H. Lopes da Silva,et al.  Chaos or noise in EEG signals; dependence on state and brain site. , 1991, Electroencephalography and clinical neurophysiology.

[25]  D Lehmann,et al.  EEG alpha map series: brain micro-states by space-oriented adaptive segmentation. , 1987, Electroencephalography and clinical neurophysiology.

[26]  a.R.V.,et al.  Clinical neurophysiology , 1961, Neurology.

[27]  Gregor Thut,et al.  Evidence for interhemispheric motor-level transfer in a simple reaction time task: an EEG study , 1999, Experimental Brain Research.

[28]  J. Ebersole,et al.  Localization of Temporal Lobe Foci by Ictal EEG Patterns , 1996, Epilepsia.

[29]  E T Bullmore,et al.  Fractal analysis of electroencephalographic signals intracerebrally recorded during 35 epileptic seizures: evaluation of a new method for synoptic visualisation of ictal events. , 1994, Electroencephalography and clinical neurophysiology.

[30]  D. Lehmann,et al.  Adaptive segmentation of spontaneous EEG map series into spatially defined microstates. , 1993, International journal of psychophysiology : official journal of the International Organization of Psychophysiology.

[31]  S. Spencer,et al.  Morphological Patterns of Seizures Recorded Intracranially , 1992, Epilepsia.

[32]  P. Viviani,et al.  Internally driven vs. externally cued movement selection: a study on the timing of brain activity. , 2000, Brain research. Cognitive brain research.

[33]  G. Pfurtscheller.  Handbook of electroencephalography and clinical neurophysiology , 1978 .

[34]  J. Ebersole,et al.  Intracranial EEG Substrates of Scalp Ictal Patterns from Temporal Lobe Foci , 1997, Epilepsia.

[35]  C. M. Michel,et al.  Temporal and spatial determination of EEG-seizure onset in the frequency domain , 2000, Clinical Neurophysiology.

[36]  J Gotman,et al.  Frequency of the Electroencephalographic Discharge in Seizures of Focal and Widespread Onset in Intracerebral Recordings , 1995, Epilepsia.

[37]  Demetrios N. Velis,et al.  Mesial temporal versus neocortical temporal lobe seizures: Demonstration of different electroencephalographic spreading patterns by combined use of subdural and intracerebral electrodes , 1995 .

[38]  E Bar-On,et al.  Fuzzy clustering of EEG signal and vigilance performance. , 1983, The International journal of neuroscience.

[39]  J. Nedzelski.  Advances in Audiology , 1985 .

[40]  Jun Kawasaki,et al.  The lateralizing value of scalp ictal eeg patterns in temporal lobe epilepsy with unilateral hippocampal atrophy with special attention to the initial slow waves , 1997 .

[41]  J S Ebersole,et al.  Continuous Source Imaging of Scalp Ictal Rhythms in Temporal Lobe Epilepsy , 1997, Epilepsia.

[42]  D Lehmann,et al.  Data-determined window size and space-oriented segmentation of spontaneous EEG map series. , 1993, Electroencephalography and clinical neurophysiology.

[43]  P J Franaszczuk,et al.  Analysis of mesial temporal seizure onset and propagation using the directed transfer function method. , 1994, Electroencephalography and clinical neurophysiology.

[44]  C. Adam,et al.  Dipole Modeling in Epilepsy Surgery Candidates , 1997, Epilepsia.

[45]  F. H. Lopes da Silva,et al.  Chaos or noise in EEG signals , 1995 .

[46]  T Landis,et al.  Non-invasive epileptic focus localization using EEG-triggered functional MRI and electromagnetic tomography. , 1998, Electroencephalography and clinical neurophysiology.

[47]  P H Crandall,et al.  Ictal localization of temporal lobe seizures with scalp/sphenoidal recordings , 1989, Neurology.

[48]  C M Michel,et al.  Spatiotemporal EEG analysis and distributed source estimation in presurgical epilepsy evaluation. , 1999, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[49]  C. Michel,et al.  Unraveling the cerebral dynamics of mental imagery , 1997, Human brain mapping.