98s C o m m u n i c a t i o n s affichdes/Posters

P180

TELEMETRY RECORDING WITH FORAMEN OVALE ELECTRODES: A SERIES OF 100. Chesterman L.P., Binnie C.D., Polkey C.E. The Maudsley Hospital, U.K.

Seizure foci are most accurately localised with stereo EEG (SEEG) but this is an expensive procedure with a significant morbidity. Accurate iocalisation is essential if highly selective procedures such as amygdalo-hippocampectomy are being considered and improves prognosis even with traditional en-bloc resection of the temporal lobe.

Foramen ovale telemetry (FOT) significantly reduces the need for SEEG, in our series to approximately one-third. In a quarter inoperability could be demonstrated with FOT, either because there was more than one focus or because its location was unsuitable. In just under a half, information from FOT was sufficient to allow operation. Our series included patients that had been previously rejected for surgery because of the likelihood of producing an unacceptable cognitive deficit.

Some centres use only en-bloc resection in those patients where the clinical history, radiological, psychological and interictal EEGs are though to have provided looalising information. We have found with F0T that this is likely to be accurate in less than 50% of such patients.

Morbidity has proved to be acceptable. We suggest that this procedure should become routine in assessment for epilepsy surgery as it is safe, reduces the need for more. invasive procedures and corrects localisation based on classical criteria.

P181

TEMPORAL MESIOLIMBIC VERSUS TEMPORAL NEOCORTICAL COMPLEX

PARTIAL SEIZURES; ELECTROCLINICAL CORRELATES RECORDED BY COMBINED DEPTH AND SUBDURAL ELECTRODES

G.J.F. Brekelmans, W. van Emde Boas, D.N. Velis and C.W.M. van Veelen*. Dept. Clin. Neurophysiol., Epilepsy Center "Meer en Bosch/De Cruquiushoeve", Heemstede and *Dept. Neurosurgery, University Hospital, Utrecht (The Netherlands).

Advanced knowledge about temporal lobe epilepsies mainly obtained by intracranial seizure recording has resulted in the distinction of two separate clinical entities: temporal lobe seizures of mesiolimbic origin and lateral temporal seizures. We retrospectively compared seizure records, obtained from 25 patients with proven unilateral temporal lobe seizures, documented by CC-TV monitoring and intracranial seizure recording using combined bilateral depth and subdural electrodes. Fourteen patients had focal or regional mesio- limbic seizure onset and ii had widespread neocortical or neocortinal and mesiolimbic seizure onset. Seizures with mesiolimbic origin showed longer intervals between EEG and clinical onset competed to seizures with widespread onset, involving the lateral temporal neo- cortex. Despite major inter-individual differences in the pattern of seizure spread certain common characteristics of the two seizure types appeared to exist. Furthermore the duration of strictly mesiolimbic seizures tended to be shorter than the neocortical seizures while postictal EEG slowing was more pronounced in the latter. Our results contribute additional information about the different temporal lobe seizure entities and provide better insight in the electrophysiological processes involved, notably regarding inter-hemispheric relations.

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PARTIAL COMPLEX STATUS: CLINICOELECTRICAL ICTAL SYMPTOMATOLOCY. Daif AK, Tahan AR, Yaqub B, AbdulJabbar M, Waheed G. Neurology and NeurophysioloKy Divisions, P.O.Box 7805(38), Riyadh 11472, Saudl Arabia.

We present ictal clinical and EEG findings of 2 patients with partial complex status.

22 years old female known to have cryptogenic partial complex seizure, stopped medication because she is pregnant, presented with fugue state. Her VEEG long monitoring showed almost continuous discharges of high voltage spikes slow wave at 6-7 c/sec independently on the left and right temporal regions. This was resistant to treatment but a combination of diazepam, phenytoin, phenobarbitone arrested the status. The second patient is 28 years old female, known to have partial complex seizure, presented with acute confusional state. The VEEG showed frequent Reneralised suppression of the background activity for 5-7 secs alternating with discharges of spikes and slow waves at 3-4 c/see, occurring at times in longer runs or brief bursts in the right mid- temporal re,ions. Durin~ the status, she had frequent automatism which occurred at the temrination of the suppression of the background activity. All were clinically and electrically stereotyped. These two cases will be discussed and shown.

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TOPOGRAPHIC STUDY OF INTERICTAL PAROXYSMS IN PARTIAL

EPILEPSY USING SCALP CURENT DENSITY FIELDS AND SCALP

POTENTIAL MAPPING.

L. Garcfa-Larrea, Ph. Ryvlin, M. Revel, F. Maugui~re, CERMEP, Lyon

(France)

We have studied the topographical scalp distribution of interictal paroxysms in

50 patients with complex partial seizures and normal CT scan. A combined

approach was used, with direct obtention of isopotential maps and subsequent

estimation of their corresponding scalp current density fields (SCD) using the

technique of Perrin et al. (IEEE trans. Biomed. Eng., 1987, 34: 283). With

respect to potential maps, SCD fields have the advantage of being reference-

free, i.e. their maxima and minima, and their zero lines are the same whatever

the reference used for potential recording. In addition, their higher spatial

resolution enables individualization of sources overlapping in potential maps.

in a first time individual spikes with similar topography were averaged. Then

topographical potential maps and their corresponding SCD fields were studied

and possible anatomical origins of the spikes considered with the aid of

physical models of the head and anatomical plates. Localization hypothesis

were compared with those proposed by other anatomical or functional non

invasive techniques (MRI, PET, SPECT). The combined approach of

potential maps and the corresponding SCD fields proved particularly

satisfactory a) in case of bilateral, simultaneously active sources; b) during the

sequential activation of different generators within a single epileptic paroxysm,

and c) in case of rapid bilateralization (<100 msec) of epileptiform activities

with focal origin. The electrophysiological approach yielded significant

information on the dynamics of epileptic paroxysms, not readily available with

other imaging techniques.