Epilcpsio. 31(6):740-746. 1990

Raven Ress, Ltd., New York 0 International League Against Epikpsy

Lateralized Effects of Subclinical Epileptiform EEG Discharges on Scholastic Performance in Children D. G. A. Kasteleijn-Nolst TrenitC, B. M. Siebelink, S. G. C. Berends, J. W.van Strien, and H. Meinardi Znstituut voor Epilepsiebestrijding, “Meer en Bosch” and “De Cruquiushoeve,” Heemstede; and Department of Child Neuropsychology, Free University, Amsterdam, The Netherlands

Summary: The interaction between lateralization of subclinical epileptiform discharges and cognitive tasks was investigated in 21 children (12 girls and 9 boys, mean age 10.6 years). Seventeen had a diagnosisof epilepsy (partial or secondarily generalized). Testing was by reading, arithmetic, and intelligence subtests during continuous telernetric EEG and video monitoring. Children with leftsided discharges had significantly lower reading performance than children with right-sided discharges. During reading, epileptiform discharges occurred relatively less

frequently and with a shorter total duration over the left hemisphere than the right. This supports the view that cognitive tasks suppress epileptiform discharges when they activate a region of the brain within the epileptogenic zone. Discharges from other epileptogenic zones not directly activated by the tasks are increased, however. Key Words: Epilepsy-Children-ElectroencephalograrnEducational status-Educational measurement-Cognition.

Short-lasting generalized epileptiform EEG discharges without obvious clinical signs can interfere with cognitive performance, as was shown by Schwab (1939) and many other investigators (for review, see Aarts et al., 1984). Aarts et al. (1984) and Binnie et al. (1987) reported that not only spontaneous generalized epileptiform activity, but also focal discharges can disrupt cognitive function in patients of many ages. Furthermore, by using spatial and verbal material in tests of short-term memory, they showed right-sided discharges to be associated with impairment of spatial and left-sided discharges to be associated with errors in verbal memory. Kasteleijn-Nolst Trenitk et al. (1988) investigated the effects of subclinical discharges on reading, mental arithmetic, and motor dexterity in children. Reading performance was significantly impaired during discharges, resulting in repetitions, corrections, hesitations, omissions, and additions. In the same group of children, Siebelink et al. (1988) showed that subclinical epileptiform EEG dis-

charges impaired performance on intelligence subtests that required short-term learning. Although previous studies (Stores and Hart, 1976; Camfeld et al., 1984) showed that children with left-sided epileptic foci have lower performance on reading and arithmetic tests than children with right-sided foci, these investigations were not performed with simultaneous EEG and video monitoring. Furthermore, in comparison to reading, arithmetic is a complex task involving multiple cognitive operations, both verbal and visuospatial (Aldenkamp, 1983; Levin and Spiers, 1985; Seidenberg, 1986) and therefore requiring activity of both hemispheres. In general, cognitive activity is believed to reduce the frequency of spontaneous epileptiform EEG discharges (Guey et al., 1965; Vidart and Geier, 1967). Hutt et al. (1977) reported that the frequency of epileptiform discharges was lowest when patients performed psychological tasks at their own level of performance as compared with tasks of greater or lesser difficulty. In contrast, we showed that discharge rates in children were lower at rest than during the performance of different scholastic tasks (Kasteleijn-NolstTrenitC et al., 1988). Therefore, we investigated the relationship be-

Received July 1989; revision accepted December 1989. Address correspondence and reprint requests to Dr. D. G. A. Kasteleijn-Nolst Trenitt at Postbus 21, 2100 AA Heemstede, The Netherlands.

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SUBCLINICAL EPILEPTIFORM DISCHARGES

tween the lateralization of subclinical epileptiform discharges and cognitive tasks. We wished to determine if lateralized discharges have differential effects on individual tasks and if separate tasks affect discharge rates over the two hemispheres differentially. In particular, we tested the following hypotheses: Children with left-sided epileptiform EEG discharges will show poorer performance on reading tasks and on some predominantly verbal subtests of a general intelligence test. Arithmetic performance, a task suggested to involve both hemispheres, will not be influenced by the lateralization of discharges. Epileptiform EEG discharges will occur less frequently over the left than the right hemisphere during reading and during some predominantly verbal subtests of a general intelligence test.

METHODS Subjects were recruited from various outpatient clinics of the lnstituut voor Epilepsiebestrijding, Heemstede, and from the Department of Pediatric Neurology of the Academic Hospital Utrecht. The criteria for subject selection included a minimum and maximum rate of occurrence of epileptiform discharges of at least once every 10 min and at most once every 2 s. Children were of at least low average intelligence (WISC-R IQ > 80) and able to perform reading and arithmetic tasks of at least second grade level; however, they were not yet attending high school. Complaints of behavioral or educational dfliculties, although not leading to exclusion, were not sought as criteria for admission. Twenty-nine children who had shown frequent epileptiform discharges in the eyes-open waking state on routine EEG were eventually referred for study. Informed consent was obtained in writing from parents according to a protocol approved by an ethical review committee. Eight subjects were shown on subsequent telemetric EEG examination to have either insufficient (less than one every 20 min) or nearly continuous epileptiform discharges. These children were excluded. The remaining 21 children (12 girls and 9 boys) had a mean age of 10.6 years (range 7.1-15.2 years, SD 1.83). Of the 21, 17 had a clear history of epilepsy: partial epilepsy in 9 and secondary generalized epilepsy in 8. The other 4 had frequent EEG epileptiform discharges but no clear history of epilepsy and were referred to the outpatient clinics because of learning and behavioral problems. Five children re-

741

ceived no antiepileptic drugs (AEDs). Eleven received monotherapy (valproate6, carbamazepine 3, phenytoin 1, and ethosuximide 1); 5 received polytherapy. Monitoring The EEG was recorded by 16-channel cable telemetry, and the child’s behavior was simultaneously registered on video. The child worked at a table in a small room with one investigator sitting directly opposite and another at the side. A microphone on the table recorded the investigators’ voices and the child’s responses (for details, see Kasteleijn-Nolst Trenitt? et al., 1988).

Test materials Reading and arithmetic tasks were presented at three levels of difficulty after the child’s current level in reading and arithmetic was determined (level 0) using a Dutch standardized reading test (Brus et al., 1973) and standardized arithmetic tests from the “50-toetsen boek” (van der Lei et al., 1982), the results of which relate the observed level of functioning to the successive steps in reading and arithmetic curricula. The BNS reading test requires the child to read out loud as many words of increasing difficulty as possible in 2 min. It assesses the level of technical reading ability and is in common use in primary schools of the Netherlands. The arithmetic tests, used for assessment of arithmetic ability, include simple additions and subtractions, as well as multiplication and division sums. Each reading level corresponded to material appropriate to children with 10 months’ exposure to formal education in school, whereas each arithmetic level corresponded to material of -5 months’ educational exposure. These different activities lasted 10 min. Both reading and arithmetic were performed aloud to permit continuous monitoring. In addition, a rest period was included in which the children were told merely that there would be a 10-min break and were offered a drink. The children were required to remain seated but otherwise could do what they chose, such as reading comics and drawing. Six subtests, in the Revised Amsterdamse Kinder Intelligentie Test (RAKIT) were used. This Dutch intelligence test for children has extensive normative data, each subtest giving a mean normalized standard score of 15 with a standard deviation of five (Bleichrodt et al., 1984). The subtests were:

-

Exclusion (subtest 2), a perceptual reasoning test; the task is to choose from four abstract figures one that does not follow a principle common to the other three. Epikpsia. Vd.31. No.6,1990

D. G . A . KASTELEIJN-NOLST TRENITL?ET AL.

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Meanings (subtest 4), a test of long-term verbal learning and recall testing knowledge of word meanings; a word is presented orally and the child selects immediately from four alternativesa picture that illustrates the meaning of the word. Discs (subtest I?),a task involving visual perception, spatial orientation, motor dexterity and speed; 18 discs with two, three, or four holes must be fitted over corresponding pegs on a board. Learning names (subtest 9), a paired associates task in which proper names are presented orally with pictures of animals and must later be reproduced in response to the picture. Two response sessions are performed, the second with feedback of correct responses. Hidden figures (subtest lo), a test for perceptual reasoning; a complex figure is presented together with six smaller figures, one of which is also concealed in the complex figure and must be identified. Concept-production (subtest 1I), a divergent production task with a strong verbal element as a measure of verbal fluency; the child is required, within a limited time, to name as many objects or situations as possible that belong to a fairly broadly described category.

AU tests were performed in the morning hours in a standardized way. Reading and arithmetic tests were not performed in one boy. Data on the intelligence tests were available in 15 children. Analysis

The long-term EEG was evaluated by two investigators without knowledge of the test results, who noted the nature, localization, lateralization, time of onset, and duration of every epileptiform discharge. The EEG discharge characteristics are shown in Table 1. Most discharges lasted 1-2 s. The maximum duration of discharges was 10 s (2 children). TABLE 1. EEG discharge characteristics in 21 children Topography of discharge

(Po1y)spike waves or spikes

Sharp waves (theta or delta waves)

Focal only

R L Focal with secondary bilateral synchrony

R L R=L Bilaterally synchronous Generalized ~~

a

A few R temporal spikes. A few R frontocentroparietal spikes.

Epilepsia, Vd.31, No. 6.1990

~~~

Total

The 21 children were divided into three groups according to the localization and lateralization of epileptiform discharges in the entire EEG recorded during the test sessions: Group I had generalized or multifocal epileptiform discharges involving both hemispheres (5 girls, 4 boys). Group I1 had localized or clearly lateralized right-sided epileptiform discharges with or withput secondary bilateral synchrony (4 girls, 4 boys). &oup I11 had localized or clearly lateralized left-sided discharges with or without secondary bilateral synchrony (3 girls, 1 by). Kruskal-Wallis one-way analyses of variance (ANOVAs) revealed no differences in age, IQ, diagnosis of epilepsy, or age at onset of epilepsy between groups. In group I, 1 of 9 patients was lefthanded in writing. In group I11(left-sided) all 4 were right-handed, whereas in group I1 (right-sided), surprisingly, 4 of 8 were left-handed in writing. Reading and arithmetic quotients were calculated on the basis of the child's current attainment minus the expected achievement (level of functioning that should be reached after the number of months of formal education the child has had) divided by the expected achievement. Differences in the reading and arithmetic quotients for the three groups were analyzed with the Kruskal-Wallis one-way ANOVA. The same procedure was used for group differences in subtests' scores (RANT). In each patient and for each task, the number and duration of EEG discharges over the two hemispheres were compared, and differences were analyzed with the Wilcoxon matched-pairs signed-ranks test.

RESULTS Influence of lateralization of subclinical epileptiform discharges on cognitive tasks

Reading and arithmetic quotients There were signifcant between-group differences in reading quotients (Kruskal-Wallis one-way ANOVA, chi-square = 5.94, p < 0.05). Subsequent analyses showed that a significant difference in reading existed only between group I1 (right-sided discharges) and I11 (left-sided discharges), MannWhitney U test, u = 1, p < 0.01; the other comparisons between groups were not statistically significant. Thus, children with left-sided discharges performed significantly poorer on reading tasks than children with right-sided discharges, i.e., children with left-sided discharges performed at a level of -2 years below and children with right-sided discharges performed at a level 1 year below their expected school level. The Kruskal-Wallis one-way ANOVA showed no significant differences in arith-

SUBCLINICAL EPILEPTIFORM DISCHARGES

metic quotients between groups (chi-square = 1.90, NS). Table 2 shows the mean reading and arithmetic quotients for the three groups. For arithmetic, all three groups performed on levels of -1 year below expected school level. The Kruskal-Wallis one-way ANOVA indicated that no differences existed between reading and arithmetic quotients within patients, in any group (chi-square = 0.28, df = 2,

NS). Intelligence test (RAKIT)

No group differences in performance on the various subtests of the RAKIT were found (KruskalWallis one-way ANOVA). Pearson correlation coefficients were determined between total IQ scores (RAKIT), subtests' scores of the RAKIT, and reading and arithmetic quotients (Table 3). This showed that total IQ scores were significantly correlated with the arithmetic quotient ( r = 0.77, p < 0.001) but not with the reading quotient (r = 0.35, NS). The reading quotient did not correlate with any of the different subtests. The arithmetic quotient, however, correlated significantly (r between 0.58 and 0.87, p < 0.05) with subtest 2 (Exclusion) and subtest 9 (Learning names), as well as with subtest 8 (Discs), 10 (Hidden figures), and 4 (Meanings). Subtest 11 (Concept production), measure of verbal fluency, did not correlate with either the reading or the arithmetic quotient. Because the subtests intercorrelated significantly, we could not divide the subtests into two independent sets of predominantly verbal and nonverbal tests.

Effects of cognitive tasks on frequency of epileptiform discharges Nearly all children showed an increase in epilep tiform discharge rates during reading (n = 20) or arithmetic (n = 19) as compared with the resting control period. The mean frequency of epileptiform discharges (number per 100 s) over the left and right hemispheres was determined during rest and during performance on the different scholastic tasks and intelligence subtests for every child Uable 4). The difference in discharge rate between the two hemi-

TABLE 3. Pearson correlation coefficients between ZQ or subtest scores and reading or arithmetic quotients

MCiUl

reading

Groups

quotient (SD)

I, both-sided 11, R-sided 111, L-sided

-0.29 (0.37) -0.12 (0.35) - 0.55 (0.08)

Mean arithmetic quotient

(SD) -0.29 (0.36)

-0.17 (0.23)

- 0.43 (0.19)

A significant dserence in reading quotients was present between groups I1 and I11 (Mann-WhitneyU test: U = 1. p < 0.01).

ReadiDg quotient

Arithmetic quotient

0.35

0.77"

0.17

0.870 0.586 0.63' 0.W 0.81" 0.28 0.486

IQ Subtest Exclusion Discs Hidden figures Meanings Learning names Concept production Reading quotient Arithmetic quotient

" p < 0.001.

p

C

0.06 0.48 0.48 0.38 0.16

-

-

0.05, p < 0.02.

spheres during rest and during arithmetic was not significant. During reading, however, epileptiform discharges occurred significantly less frequently over the left hemisphere than the right. Between the three conditions (rest, reading, and arithmetic), there were no signifcant differences in discharge rate either for the epileptiform discharges over the left hemisphere (Friedman two-way ANOVA, chisquare = 2.042, df = 2, p > 0.05) or over the right (Friedman two-way ANOVA, chi-square = 2.844, df = 2, p > 0.05). Thus, during reading,the left and right hemispheric discharges were increased in comparison with rest but the left-sided discharges were increased to a lesser extent than those on the right. The data of left-handed patients did not influence the results in either a positive or negative direction. There were no signifcant differences in discharge rates between the two hemispheres for the various subtests of the RAKIT (Table 4). Differences in the relative duration of discharges over the two hemiTABLE 4. Mean number of localized discharges per 100 s occurring during pe6ormance of a spec8c task or subtest Mean number of discharges Performance

RAKIT subtests Exclusion

TABLE 2. Mean reading and arithmetic quotients in the three groups

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DiSCS

Hidden figures

Meanings Leaming names Concept production Scholastic skills Reading Arithmetic Rest

L-sided

R-sided

z statistic

1.58 2.19 1.59 1.46 1.36 1.33

2.70 2.82 2.64 2.12 2.02 2.17

-0.62 -0.30 - 0.71 - 0.56 -0.53 -0.41

0.63 0.97 0.57

2.27 2.65 2.04

- 1.87" - 1.57 - 1.40

Analysis of differences in the frequency of right (R) and kft (L) sided discharges for all children by Wilcoxon matched-pairS signed ranks test (z statistic). a

p

< 0.05.

Epilepsia. Vd.31, No. 6,19W

D . G . A . KASTELEIJN-NOLST TRENITg ET AL.

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spheres for each subtest or scholastictask were also determined (Table 5). Only the reading task showed a trend for a relative increase in the duration of discharges over the right hemisphere as compared with the left. DISCUSSION

Our findings confim the hypothesis that children with localized or clearly lateralized left-sided epi-

leptiform discharges show poorer reading performance than children with localized or clearly lateralized right-sided discharges and that arithmetic is not influenced by the lateralization of discharges. These findings agree with those of Stores and Hart (1976), who showed that children with left-sided epileptic foci had lower reading performance than children with right-sided foci. Our results, however, did not confim those of Camfeld et al. (1984) concerning arithmetic performance; they reported that children with left temporal foci had lower scores on mental arithmetic than children with right temporal foci. Neither of these previous studies simultaneously correlated epileptiform discharges in the EEG with test performance, unlike the present study, but relied only on a diagnostic routine EEG. Our findings are consistent with current understanding that at the age of investigation of our children, reading is generally supported in the left hemisphere (Bakker and Vinke, 1985) whereas arithmetic is a function involving both hemispheres (Levin and Spiers, 1985). Performance levels on the subtests of the RAKIT were about equal in the three groups. No definite conclusions could be drawn about the relation between localization or lateralization of epileptiform TABLE 5. Percentages of time of the task taken by localized discharges during performance of that specific task and analysis of differences in duration of right (R) and left (L) sided discharges for all children with the Wilcoxon matched-pairs signed ranks test (z statistic) Percentage of time of task taken by discharges Performance

Lefi-sided

Right-sided

z statistic ~~

RAKIT subtests Exclusion DiSCS

Hidden f5gures Meanings Learning names Concept production Schokstic skills

Reading Arithmetic a

p < 0.05.

E p i b s i a . Vd.31, No. 6, 1990

1.54 3.38 1.71 0.74 1.07 0.90

1.30 1.05 1.38 0.81 0.74 0.78

-0.09 -0.42 -0.53 -0.76 -0.26 - 0.15

0.67 1.25

2.79 2.26

- 1.59” - 1.25

EEG discharges and performance on the individual subtests. Our findings support the second hypothesis that during reading epileptiform discharges occur relatively less frequently over the left hemisphere than the right. The total duration of discharges was also relatively longer over the right hemisphere as compared with the left during reading. Such differences were not found for the different subtests of the RAKIT and for arithmetic or during rest. The finding of a nonsignificant predominance of right-sided discharges during rest can be explained by the fact that most children preferred reading comics. In our previous study (Kasteleijn-NolstTrenite et al., 1988) we showed that when the results of all children were analyzed together, epileptiform discharges increased during the performance of scholastic tasks. The present findings provide additional evidence for an interaction between the nature of the cognitive task and the lateralization of discharges and suggest a greater increase in discharge rate over the right hemisphere than over the left hemisphere during reading as compared with rest. Apparently, the increase in epileptiform discharges during the performance of scholastic tasks found in our previous study resulted from a selectively higher increase over the hemisphere less activated by a specific task. Cognitive tasks that activate regions of the brain within an epileptogenic zone suppress discharges within that zone but facilitate discharges from other epileptogenic regions in the contralateral hemisphere. Results are somewhat at variance with reports in the literature concerning seizures induced by mental activity. Wilkins et al. (1982) reported a patient who had generalized convulsions precipitated by arithmetic, and Aarts et al. (1984) described an intelligent librarian with a specific history of difficulties in concentration when cataloguing. In both patients, EEG testing revealed epileptiform discharges that appeared only during specific intellectually demanding activities. Wilkins (1986) postulated the idea that in patients with localized epileptiform EEG activity its incidence is increased by cognitive tasks activating that specific region of the brain and decreased by cognitive activity that involves other brain regions. In this study only one child, a 7-year-old girl with left-sided discharges, showed an increase in discharges when reading and not during arithmetic. These discharges remained subclinical. Therefore, the literature reports may concern exceptional cases only. The interaction between cognitive tasks and the frequency, duration, and localization and lateralization of the epileptiform EEG discharges is complex.

S UBCLlNlCAL EPlLEPTlFORM DISCHARGES

Long-term EEG and video monitoring with simultaneous psychological testing remains indispensable for the study of cognitive function in patients with epilepsy. In agreement with our previous investigation (Kasteleijn-Nolst TrenitC et al., 1988), the present study stresses the value of a reading test as a sensitive diagnostic tool for detecting the influence of epileptiform discharges on cognitive function. Acknowledgment: D.G.A.K.-N.T. and B.M.S. were supported by a grant from CLEO (Commissie Landelijk Epilepsie Onderzoek). We thank Professor J. Willemse who referred most of the patients and Norman So and A. J. Wilkins for critical comments. We thank K. Brandsen-Schipper for help in preparing the text, and A. Smit and P. van Egmond for technical assistance.

REFERENCES Aarts JHP. Binnie CD. Smit AM, et al. Selective cognitive im-

pairment during focal and generalized epileptiform EEG activity. Brain Dev 19&6;107:293-308. Aldenkmp AP. Epilepsy and learning behaviour. In: Parsonage M. Grant RHE. Craig AG. Ward AA Jr. eds. Advances in epileprology: the XIVrh epilepsy internariowl symposium. New York: Raven Press, 1983:2214. Bakker DJ, Vinke J. Effects of hemispheric-specific stimulation on brain activity and reading in dyslectics. Clin Exp Neuropsychol 1985;7;5:505-25. Binnie CD, Kasteleijn-NolstTrenitt DGA. Smit AM, et al. Interaftions of epileptiform EEG dischargesand cognition. E p ilepsy Res 1987;1:239-45. Bleichrodt N, Drenth PJD, Resing WCM, et al. R.A.K.I.T.. Instructie, Normen en Psychometrische Gegevens. Lisse: Swets & Zeithger, 1984. Brus BT, Voeten MJM.Een-Minuur Tesr. Nijmegen: Berkhout, 1973. Camfleld PR, Gates R, Ronen G, et al. Comparison of cognitive ability, personality profile and school success in epileptic children with pure right versus left temporal lobe EEG foci. Ann Neurol 1984;15:122-6. Guey J, Tassinari CA, Charles C, et al. Variations du niveau d'eficience en relation avec des dtcharges tpileptiques paroxystiques. Rev Neurol 1%5;112:311-17. Hutt SJ, Newton S, Fairweather H. Choice reaction time and EEG activity in children with epilepsy. Neuropsychologia 1977;15:25747. Kasteleijn-Nolst Trenitt DGA, Bakker DJ, Binnie CD, et al. Psychological effects of epileptiform EEG discharges. I. Scholastic skills. Epilepsy Res 1988;2:1114. van der Leij A, Struiksma AJC. Her 50-Toersenboek. Amsterdam: PI-vu, 1982. Levin HS, Spiers PA. Acalculia. In: Heilman KM,Valenstein E, eds. Clinical Neuropsychol. New Yo& Oxford University Press, 1985:97-1 IS. Schwab RS. A method of measuring consciousness in petit mal epilepsy. I N e w Menr Dis 1939;89:690-1. Seidenbeg M,Beck N, Geisser M,et al. Academic achievement of children with epilepsy. Epilepsia 1986:27:75>9. Siebelink BM,Bakker DJ, Binnie CD, et al. Psychological effects of subclinical epileptiform EEG discharges in children. 11. General intelligence tests. Epilepsy Res 1%8;2:117-21. Stores G, Hart J. Reading skills of children with generalized or

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focal epilepsy attending ordinary school. Dev Med Child Neurol 1976;18:705-15. Vidart L, Geier S. Enreaistrements ttlt-enctohalmuhiaues chex des sujets tpdepiiques pendant le tra& Rev Neurol 1%7;117:47~. W i s AJ, Zitkin 9 , Andermann F, et al. Seizures induced by thinking. Ann Neurol 1982;11:608-12. Wilkins AJ. On the manner in which sensory and cognitive processes contribute to epileptogenesis,and are disrupted by it. Acra Neurol Scand 1986;74(suppl 109):91-5.

- . .--

L'interaction entre la lattralisationdes dtcharges tpileptiques infracliniques et les performances aux taches cognitives a ttc evalute chez 21 enfants (12 filles, 9 garcons, b e moyen 10.6 ans). Chez 17 enfants, le diagnostic d'tpilepsie partielle ou secondairement gtntraliste avait Ctt port& 11s ont beneficit de tests de lecture, d'arithmbtique et des sous-tests des Cchelles d'intelligence pendant une surveillance continue EEG ttltmttrique et video. Les enfants qui prtsentaient des dtcharges lattralistes B gauche avaient, par rapport A ceux qui prtsentaient des dtcharges lattralistes B droite, des performances sigruficativement diminutes pour la lecture. Pendant la lecture, les dtcharges paroxystiques survenaient de f q o n relativement moins frtquente, et avaient une dw6e globalement plus faible sur I'htmisphh gauche que sur Ie droit. Ces d o n n h semblent confirmer que les taches cognitives suppriment les dtcharges paroxystiques parce qu'elles activent une rCgion du cerveau qui est incluse dans la zone tpileptogkne. Cependant. les dtcharges provenant d'autres zones tpileptoghes qui ne sont pas directement activtes par ces taches sont augmentces. (P. Genton, Marseille)

RESUMEN En 21 ninos (12h a s y 9 nhios con edad media de 10.6 afios) ha sido investlgada la interacci6n entre la lateralizaci6n de las descargas subclinicas epileptiformes y las pruebas cognitivas. Diecisiete tenian un diagn6stico de epilepsia partial o secundariamente generalizada. Los estudios consistian en lectura y subtests de aritmttica e inteligencia durante un registro telemttrico de EEG continuo y monitorizaci6n con video. Los nhios con descargas en el lado izquierdo mosharon una reducci6n significativa mAs importante en su facilidad para la lectura que 10s que tenian descargas en el lado derecho. Durante la lectum, las descargas epileptiformes aparecieron con una freuiencia relativamente mAs reducida y con una duraci6n total m6.s corta en el hemisferio izquierdo que en el derecho. Estos hallazgos apoyan la opini6n de que las pruebas cognitivas reducen las descargas epileptiformes cuando activan UM regi6n del cerebro que se encuentra en el interior de la ZOM epileptogenica. S i n embargo se incrementan las descargasen otras ulnas epileptogenicas que no estan directamente activadas por las pruebas cognitivas.

(A. Portera-sbnchez, Madrid)

ZUSAMMENFASSUNG Die Interaktion zwischen Lateralisienmg von subklinischen epileptischen Entladungen und kognitiven Aufgaben wurde bei Epilepsia,

Vd.31, No. 6,1990

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D . G. A . KASTELEIJN-NOLST TRENITl? ET AL..

21 Kindern (12 Miidchen, 9 Jungen, mittleres Alter 10.6 Jahre) untersucht. 17 hatten eine Epilepsie mit partialen oder sekund&

generalisierten Anfaen. Getestet wurden Lesen, Rechnen, InteUigenz-Unterteste wghrend der kontinuierlichen telemetrischen EEG- und Video-Ableitung. Kinder mit linksseitigen Entladungen zeigten slgnifikant schlechtere Leseleistungen als diejenigen mit rechtsseitigen Entladungen. W h n d des Lesens erschienen die epileptischen Entladungen relativ weniger Mufig und mit geringerer Gesamtdauer iiber der linken Hemisphiire als

Epilepsia. Vol. 31, No. 6, 1990

iiber der rechten. Diese Befunde stiitzen die Ansicht, da6 kognitive Aufgaben epileptische Entladungen unterdriikken, wenn dadurch Himareale in der epileptischen Zone aktiviert werden. Dagegen nehmen die epileptischen Entladungen anderer Regionen, die nicht direkt aktiviert werden, w W n d der Aufga-

ben zu. (C. G. Lipinski, HeidelberglNecknrgemlind)