PS-28-6 EEG topographic mapping and dipole source modeling of ictal localized epileptic activities

PS-28-6 EEG topographic mapping and dipole source modeling of ictal localized epileptic activities

Postersession 28. Epilepsy (1) S154 decreased tracer accumulation in ~231-1omazenil SPECT indicate decreased BZr binding, we speculate that decrease...

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Postersession 28. Epilepsy (1)

S154

decreased tracer accumulation in ~231-1omazenil SPECT indicate decreased BZr binding, we speculate that decreased GABAA/BZr is related to the basic mechanism of temporal lobe epilepsy.

I PS-28-31 On the relationship between spect findings and epileptic EEG foci in temporal lobe epilepsy Teruhiko Shimizu, J un Yoshikawa, Matu6 Miyasaka, Takashi Nakano. Department of Psychiatry, Dokkyo University

School of Medicine, Tochigi, Japan The regional cerebral blood flow was investigated by IMP-SPECT in 42 temporal lobe epilepsy cases for the detection of the neurobiological background of epileptogenic foci. Twenty seven cases showed the localized abnormalities on SPECT. In all cases showed the hypoperfusion. In 17 out of the 27, the lateralities of localized hypoperfusion areas were consistent with those of spike foci recorded immediately after the SPECT examination. Seven cases in the 27 with no focal spike in the investigated day showed the localized hypoperfusion areas consistent with the spike foci recorded in the past EEG. 15 cases showed the normal perfusion. Six of these 15 cases showed the focal spikes on EEG recorded on the same day. 9 cases showed no spike and no basic abnormality on EEG in the investigated day. We thought the SPECT-scanning was a useful functional examination in the assessment of the neuro-biological background of epileptogenic focus in the brain, because SPECT was more sensitive than CT-scanning on detection of localized abnormalities corresponding to epileptic E E G foci. From the viewpoint of the prognosis, the decrease in seizure frequency was longitudinally associated with the normal SPECT finding, normal basic activity and disappeared spikes on EEG on temporal lobe epilepsy.

IPS-28-41

"Cavernous sinus" EEG: a new method for preoperative evaluation of temporal lobe epilepsy

Nobuhiro Mikuni 1, Kouji Matsumoto 1, Naoki Oogata 1, Kenichi Murao 1, lchiro Nakahara l, Naoki Oogata l, Waro Taki i, Haruhiko Kikuchi l, Kiyohito Terada 2, Akio Ikeda 2, Hiroshi Sibasaki 2. 1Departments of Neurozurgery, 2Brain

Pathophysiology, Kyoto University, School of Medicine, Kyoto, Japan In the surgical treatment of temporal lobe epilepsy (TLE), the invasive methods are necessary if various noninvasive evaluations are not convergent enough to identify the epileptogenic area accurately. We placed Tracker-10 system Seeker Lite-10 guide wireR into the cavernous sinus (CS) via the internal jugular vein bilaterally to record EEG (CS-EEG) in 4 intractable TLE patients, and scalp E E G and ECoG were simultaneously recorded in 4 and 3 patients, respectively. CS-EEG demonstrated clear epileptiform discharges frequently in spite of the absence of spikes at the scalp EEG recorded simultaneously. The spikes on CS-EEG was seen simultaneously with spikes at the mesial temporal area on ECoG. Ictal EEG pattern was also clearly documented on CS-EEG. This new, semi-invasive method can detect epileptiform discharge originating from the mesial temporal area, and we suggest that clinically it is as useful as, or complements the current invasive techniques such as foramen ovale or depth recording.

I P8-28-5

1 Dipole source estimation of focal epileptic spikes: correlation with stereo-electroencephalographic findings

G. Rubboli, S. Francione 1, L. Parmeggiani, L. Tassi 1, J.J. Carbonell, P. Kahane 1, S. Meletti, C. Munari 1, C.A. Tassinari.

Department of Neurology, Universityof Bologna, Bellaria Hospital, Bologna, Italy; 1Neurosciences Department, INSERM U 318, CHU, Grenoble, France Dipole source estimation (DSE) was performed, using a multiple spatio-temporal dipole approach, to define the epileptic spikes generator(s) in four patients undergoing presurgical evaluation; the results were correlated with stereo-electroencephalographic (SEEG) findings. Scalp E E G showed: fronto-temporal spikes (four patients) associated with ipsilateral independent temporo-parietooccipital spikes (one patient), or with contralateral asynchronous fronto-temporal spikes (one patient). S E E G demonstrated the activation of multiple, spatially distinct cerebral structures in the generation of each spike type. Dipole locations, located slightly dorsal to a position approximately corresponding to the "center of gravity" of the cerebral structures generating each spike type, were in the correct hemisphere in all cases. In three patients, four frontotemporal spike foci (one patient showed bilateral asynchronous fronto-temporal foci) were modeled by a single dipole, with orientation intermediate between radial and tangential. In the fourth patient, with fronto-temporal and independent ipsilateral temporoparieto-occipital spikes we obtained two different source configurations, in accordance with SEEG findings. Our data suggest that DSE methods seem to be able to identify the correct side of the focus and to discriminate between different generators; however, compression of the complex geometry of the generator, as demonstrated by SEEG, in a single equivalent dipole limits the anatomic definition of the generator.

I PS'28-61 EEG topographic mapping and dipole source modeling of ictal localized epileptic activities Katsuhiro Kobayashi, Harumi Yoshinaga, Takashi Asano, Hironobu Hata, Yoko Ohtsuka, Eiji Oka, Shunsuke Ohtahara.

Department of Child Neurology, Okayama UniversityMedical School Since EEG topographic mapping and the dipole source modeling could not be reliably applied to ictal localized epileptic activities, we newly developed a method to enable this application employing matrix algebra including singular value decomposition (SVD). Ictal epileptic activity, especially during the beginning part of a seizure, in an EEG data matrix was separated from the background as 1or 2-dimensional data by SVD which was intentionally biased to increase variance of the epileptic activity with subsequent correction. The extracted epileptic component was expressed as product of the waveform, the amplitude and the field distribution. This field distribution was shown as a map reflecting the geometry of the epileptic generator and led to the position and the orientation of the corresponding equivalent current dipole by the dipole localization method. This method was applied to 18 data epochs from six ictal EEGs of complex partial seizures of four patients to yield successfully the maps and the dipole parameter estimates of the epileptic activities. The obtained maps and dipole parameters were quite consistent in each patient, indicating usefulness and reliability of this method. Dimensionality of the epileptic data tended to increase from 1 at the beginning part of the seizures to 2 with seizure progression, suggesting the spatially expanding tendency of the epileptic generators.