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P224 Artificial neural network approach to EEG analysis
Poster Session: EEG and EEG Related Techniques - Epilep~.
[P•-•
COMPUTER ANALYSIS OF EEG BACKGROUNDACTIVITY DURING CARBAMAZEPINE INTRODUCTION
R. Naumovski, V. Nikolovski, M. Pashu, E. Cvetkovska. Skopje, R.
Macedonia In order to minimize the effects on the basic activity of the central nervous system (CNS) being evoked by the epilepsy, we made a research of the spectral power in 21 patients whose EEGs were evaluated in two parameters as normals: (a) visually, and (b) by comparing the finding of quantitative analysis of each single EEG with statistical bases of normative findings, obtained by 50 healthy volunteers. The group of patients consisted of 12 women and 9 men (the average age of 32.9 ~ 5.7 yr); all having a short history of the disease and did not receive any antiepileptic drugs. Their neurologic, somatic and CT finding were normal. The first registrate was made before the start of the rnonotherapy for CBZ, and the control after 30 days since a stable therapeutic serum drug level was achieved. In later analysis the spectral power was calculated in four frequency areas: (1) 1--4, 4-8, 8--13 and 13-23 Hz; (2) 4-6, 6-8, 8-13 and 13-23 Hz; (3) 3-5, 5-7, 7-9, and 9-11 Hz; and (4) 2-5, 5-8, 8-11 and 11-14 Hz. Significant increase of the spectral power in frequency areas under 8 Hz was found. They were symmetrical and evenly distributed over all scalp leads.
[--P-~
ARTIFICIAL NEURAL NETWORK APPROACH TO EEG ANALYSIS
D. Furund~.i6 I, V. Radivojevi6 2, D. Rakovi63 p. Djurdjevi~ I. i Mihajlo
Pupin Institute, Knowledge Engineering Laboratory; Belgrade, Yugoslavia; 2 Institute for Mental Health. Dept. of Clinical Neurophysiology, Belgrade, Yugoslavia; 3 Faculty of Electrical Engineering, University of Belgrade, Yugoslavia Artificial neural network-multilayer perceptron with Back Propagation learning algorithm, after the training (identification) phase was used in muhichannel human EEG for: a) Elimination of artifacts by reconstruction of scalp electrical field from signal registered from uncontaminated channels; b) Automatic segmentation of EEG signal to segments with stationary dynamics, as a pre-processing for further analysis; c) Identifying influence of EEG signal from occipital channels during visual stimulation (flash VEP) to induced signal changes in other channels and their time delays. We also showed that a variety of responses to visual stimulus exist in all channels, and that their characteristics depends on the channel observed and spontaneous activity short time before the stimulus onset.
NONLINEAR DYNAMICS APPROACH TO THE ANALYSISOF EEG M. Rajkovid i, V. Radivojevi6 2 M. Car 2, D. Timotijevi6 3. i Institute of Nuclear Sciences VINCA, Belgrade, Yugoslavia; : Institute for Mental Health, Belgrade, Yugoslavia; 3 Institute of Physics, Belgrade, Yugoslavia Analysis of human multichannel EEG signals is performed using a original method based on the nonlinear dynamics theory, chaos and differential topology. Each set of spatial and temporal recordings defines an attractor (a topological object) in phase space. Topological characteristics are inspected locally and functional relationship is established between the information content and local geometric features of an attractor. In this manner transients and signal characteristics not detectable by other methods are analyzed. We demonstrate the method on one set of normal EEG signals and one set from pathological cases. Particular attention is paid to the local Lyapunov exponents in detecting transients which reflect the local topological curvatures on the attractor, and the difference in the information content of analyzed signals, both locally and globally in phase space.
- ~ - 2 - ~ MATCHED FILTER IN BRAIN EVOKED POTENTIALS CHARACTERIZATION D. Veljkovi~ i, V. Radivojevi6 2, D. Rakovi6 i. 1 Faculty of Electrical Engineering, University of Belgrade, Yugoslavia; ~-Institute for Mental Health, Dept. of Clinical Neurophysiology, Belgrade, Yugoslavia This article describes original matched filter model suitable for the evaluation of time delay and shape of evoked potentials. This filter is based on principles of signal detecting from communication theory applied to human
325
multichannel EEG signal during sensory stimulation. The model differs from classical averaging methods for evoked potentials extraction since it requires less epochs for analysis and provides an opportunity to analyze individual responses independently of averaged response. The complete algorithm of the model is given, as well as examples from the application on the visual evoked potentials.
~2~1
PHOTOPAROXYSMALRESPONSE (STUDY AND REVIEW IN 66 PATIENTS)
D. Pinto, C.P. Sousa, I. Pires, J.A. Ribeiro, G. Sousa, M.L. Guimar~es.
Neurophysiology Department, H.S. Jolt, Porto, Portugal In order to investigate the significance of the photoparoxysmal response (PPR) and its relation with the Epileptic Syndromes in our patients, we performed a retrospective analysis between Jan. 1990 and Oct. 1995. The records of 66 patients, that had a PPR (prolonged or self limited) in our Laboratory during a routine EEG with a photic stimulation using a standardized technique, were reviewed. We found 46 females and 20 males, aged 5-73 years, mean 22.63 years. The clinical charts of epileptic patients were also reviewed and the syndromes classified according to the International Classification of Epileptic Syndromes (1989): 31 had Generalized Epilepsies; 20 Partial Epilepsies; 2 Special Syndromes; 2 Reflex Epilepsies; 9 not classified (whether GEp. or P Ep); and 2 patients had no crisis. Others characteristics noted were: different pathologies, family incidence of epilepsy, clinical photosensitivity, neuroimage and antiepileptic drugs (AED). The EEG charts were examined also for other epileptiform abnormalities: 56/66 had these abnormalities. A follow-up EEG with intermittent photic stimulation (IPS) and pattern sensitivity was performed with a follow-up period of 6 months-6 years, with the purpose of evaluate the outcome of PPR as well to determine the pattern sensitivity in these patients.
[-P-~
THE RELATIONSHIP BETWEEN THE ABNORMALITIES IN THE ELECTROENCEPHALOGRAM AND COGNITIVE DYSFUNCTIONS IN PATIENTSWITH UREMIC ENCEPHALOPATHY
R.Dj. Suji6 l, M.G. Vukovi6 2. ] Institute of Neurology, Zvezdara Clinical
Center; 2 Faculty of Defectology, University of Belgrade, Yugoslavia We examined 30 adult patients with uremic encephalopathy (10 uremic patients and 20 chronic haemodialysis patients). The main goal of this examination was to estimate the relationship between the abnormalities in electroencephalogram and disorders of cognitive functions. In this research we used method of the standard electroencephalo-graphy and neuropsychological tests for attention, perception, memory and language. The obtained results showed abnormal EEG in 5 of 10 uremic patients and only in 2 of 20 chronic haemodialysis patients. On the other hand, all uremic patients had noticeable disorders of all cognitive functions, while chronic dialysis patients had only disorders of memory and language. Attention and perception were significantly better preserved than in uremic patients. We showed correlation between abnormal EEG and profile of disorder cognitive functions in chronic uremic patients.
[ - ~ 9 - ~ APPENDICULAR PAIN AS A SIGN OF EPILEPSY L.K. Kaitazki. Central Clinical Hospital, Sofia, Bulgaria The diagnosis of epilepsy sometimes is very difficult because of existence of atypical clinical forms of the disease. In some cases it may even be misdiagnosed with internal or surgical disorders. In this context a case of 19-years-old soldier can be considered. The patient had sudden attacks of sharp appendicular pain, followed by headache, nausea, dizziness, pallor, sweating, and sometimes tonic-clonic fits with unconsciousness. From medical history was uncovered the patient had had such crisis since childhood, no investigations and therapy had been provided. Interictal EEG showed paroxysms in left temporal and occipital region, and during the onset of attack EEG record showed generalized paroxysmal bursts with left temporal maximum. The patient had undergone appendectomy for such complains during active military service, but no improvement was observered. After beginning anti-convulsant therapy
[P•-•
COMPUTER ANALYSIS OF EEG BACKGROUNDACTIVITY DURING CARBAMAZEPINE INTRODUCTION
R. Naumovski, V. Nikolovski, M. Pashu, E. Cvetkovska. Skopje, R.
Macedonia In order to minimize the effects on the basic activity of the central nervous system (CNS) being evoked by the epilepsy, we made a research of the spectral power in 21 patients whose EEGs were evaluated in two parameters as normals: (a) visually, and (b) by comparing the finding of quantitative analysis of each single EEG with statistical bases of normative findings, obtained by 50 healthy volunteers. The group of patients consisted of 12 women and 9 men (the average age of 32.9 ~ 5.7 yr); all having a short history of the disease and did not receive any antiepileptic drugs. Their neurologic, somatic and CT finding were normal. The first registrate was made before the start of the rnonotherapy for CBZ, and the control after 30 days since a stable therapeutic serum drug level was achieved. In later analysis the spectral power was calculated in four frequency areas: (1) 1--4, 4-8, 8--13 and 13-23 Hz; (2) 4-6, 6-8, 8-13 and 13-23 Hz; (3) 3-5, 5-7, 7-9, and 9-11 Hz; and (4) 2-5, 5-8, 8-11 and 11-14 Hz. Significant increase of the spectral power in frequency areas under 8 Hz was found. They were symmetrical and evenly distributed over all scalp leads.
[--P-~
ARTIFICIAL NEURAL NETWORK APPROACH TO EEG ANALYSIS
D. Furund~.i6 I, V. Radivojevi6 2, D. Rakovi63 p. Djurdjevi~ I. i Mihajlo
Pupin Institute, Knowledge Engineering Laboratory; Belgrade, Yugoslavia; 2 Institute for Mental Health. Dept. of Clinical Neurophysiology, Belgrade, Yugoslavia; 3 Faculty of Electrical Engineering, University of Belgrade, Yugoslavia Artificial neural network-multilayer perceptron with Back Propagation learning algorithm, after the training (identification) phase was used in muhichannel human EEG for: a) Elimination of artifacts by reconstruction of scalp electrical field from signal registered from uncontaminated channels; b) Automatic segmentation of EEG signal to segments with stationary dynamics, as a pre-processing for further analysis; c) Identifying influence of EEG signal from occipital channels during visual stimulation (flash VEP) to induced signal changes in other channels and their time delays. We also showed that a variety of responses to visual stimulus exist in all channels, and that their characteristics depends on the channel observed and spontaneous activity short time before the stimulus onset.
NONLINEAR DYNAMICS APPROACH TO THE ANALYSISOF EEG M. Rajkovid i, V. Radivojevi6 2 M. Car 2, D. Timotijevi6 3. i Institute of Nuclear Sciences VINCA, Belgrade, Yugoslavia; : Institute for Mental Health, Belgrade, Yugoslavia; 3 Institute of Physics, Belgrade, Yugoslavia Analysis of human multichannel EEG signals is performed using a original method based on the nonlinear dynamics theory, chaos and differential topology. Each set of spatial and temporal recordings defines an attractor (a topological object) in phase space. Topological characteristics are inspected locally and functional relationship is established between the information content and local geometric features of an attractor. In this manner transients and signal characteristics not detectable by other methods are analyzed. We demonstrate the method on one set of normal EEG signals and one set from pathological cases. Particular attention is paid to the local Lyapunov exponents in detecting transients which reflect the local topological curvatures on the attractor, and the difference in the information content of analyzed signals, both locally and globally in phase space.
- ~ - 2 - ~ MATCHED FILTER IN BRAIN EVOKED POTENTIALS CHARACTERIZATION D. Veljkovi~ i, V. Radivojevi6 2, D. Rakovi6 i. 1 Faculty of Electrical Engineering, University of Belgrade, Yugoslavia; ~-Institute for Mental Health, Dept. of Clinical Neurophysiology, Belgrade, Yugoslavia This article describes original matched filter model suitable for the evaluation of time delay and shape of evoked potentials. This filter is based on principles of signal detecting from communication theory applied to human
325
multichannel EEG signal during sensory stimulation. The model differs from classical averaging methods for evoked potentials extraction since it requires less epochs for analysis and provides an opportunity to analyze individual responses independently of averaged response. The complete algorithm of the model is given, as well as examples from the application on the visual evoked potentials.
~2~1
PHOTOPAROXYSMALRESPONSE (STUDY AND REVIEW IN 66 PATIENTS)
D. Pinto, C.P. Sousa, I. Pires, J.A. Ribeiro, G. Sousa, M.L. Guimar~es.
Neurophysiology Department, H.S. Jolt, Porto, Portugal In order to investigate the significance of the photoparoxysmal response (PPR) and its relation with the Epileptic Syndromes in our patients, we performed a retrospective analysis between Jan. 1990 and Oct. 1995. The records of 66 patients, that had a PPR (prolonged or self limited) in our Laboratory during a routine EEG with a photic stimulation using a standardized technique, were reviewed. We found 46 females and 20 males, aged 5-73 years, mean 22.63 years. The clinical charts of epileptic patients were also reviewed and the syndromes classified according to the International Classification of Epileptic Syndromes (1989): 31 had Generalized Epilepsies; 20 Partial Epilepsies; 2 Special Syndromes; 2 Reflex Epilepsies; 9 not classified (whether GEp. or P Ep); and 2 patients had no crisis. Others characteristics noted were: different pathologies, family incidence of epilepsy, clinical photosensitivity, neuroimage and antiepileptic drugs (AED). The EEG charts were examined also for other epileptiform abnormalities: 56/66 had these abnormalities. A follow-up EEG with intermittent photic stimulation (IPS) and pattern sensitivity was performed with a follow-up period of 6 months-6 years, with the purpose of evaluate the outcome of PPR as well to determine the pattern sensitivity in these patients.
[-P-~
THE RELATIONSHIP BETWEEN THE ABNORMALITIES IN THE ELECTROENCEPHALOGRAM AND COGNITIVE DYSFUNCTIONS IN PATIENTSWITH UREMIC ENCEPHALOPATHY
R.Dj. Suji6 l, M.G. Vukovi6 2. ] Institute of Neurology, Zvezdara Clinical
Center; 2 Faculty of Defectology, University of Belgrade, Yugoslavia We examined 30 adult patients with uremic encephalopathy (10 uremic patients and 20 chronic haemodialysis patients). The main goal of this examination was to estimate the relationship between the abnormalities in electroencephalogram and disorders of cognitive functions. In this research we used method of the standard electroencephalo-graphy and neuropsychological tests for attention, perception, memory and language. The obtained results showed abnormal EEG in 5 of 10 uremic patients and only in 2 of 20 chronic haemodialysis patients. On the other hand, all uremic patients had noticeable disorders of all cognitive functions, while chronic dialysis patients had only disorders of memory and language. Attention and perception were significantly better preserved than in uremic patients. We showed correlation between abnormal EEG and profile of disorder cognitive functions in chronic uremic patients.
[ - ~ 9 - ~ APPENDICULAR PAIN AS A SIGN OF EPILEPSY L.K. Kaitazki. Central Clinical Hospital, Sofia, Bulgaria The diagnosis of epilepsy sometimes is very difficult because of existence of atypical clinical forms of the disease. In some cases it may even be misdiagnosed with internal or surgical disorders. In this context a case of 19-years-old soldier can be considered. The patient had sudden attacks of sharp appendicular pain, followed by headache, nausea, dizziness, pallor, sweating, and sometimes tonic-clonic fits with unconsciousness. From medical history was uncovered the patient had had such crisis since childhood, no investigations and therapy had been provided. Interictal EEG showed paroxysms in left temporal and occipital region, and during the onset of attack EEG record showed generalized paroxysmal bursts with left temporal maximum. The patient had undergone appendectomy for such complains during active military service, but no improvement was observered. After beginning anti-convulsant therapy