The contribution of posterior circulation to memory function during the intracarotid amobarbital procedure.

The purpose of this study was to evaluate the contribution of posterior circulation to memory function by comparing memory scores between patients with and without a foetal-type posterior cerebral artery (FTP) during the intracarotid amobarbital procedure (IAP) in epilepsy patients. Patients undergoing bilateral IAP between January 2004 and January 2010 were retrospectively included. Pre-test angiograms were assessed for the presence of a FTP. Memory function scores (% correct) after right and left injections were obtained. Functional significance of FTP was affirmed by relative occipital versus parietal EEG slow-wave increase during IAP. Memory and EEG scores were compared between patients with and without FTP (Mann-Whitney U test). A total of 106 patients were included, 73 with posterior cerebral arteries (PCA) without FTP ('non-FTP'), 28 patients with unilateral FTP and 5 with a bilateral FTP. Memory scores were lower when amytal was injected to the hemisphere contralateral to the presumed seizure focus (on the right decreasing from 98.3 to 59.1, and on the left decreasing from 89.1 to 72.4; p < 0.001). When IAP was performed on the side of FTP memory scores were significantly lower (70.8) compared to non-FTP (82.0; p = 0.02). Relative occipital EEG changes were 0.44 for FTP cases and 0.36 for non-FTP patients (p = 0.01). A relationship between vasculature and brain function was demonstrated by lower memory scores and more slow-wave activity on occipital EEG during IAP in patients with foetal-type PCA compared to patients with non-FTP. This suggests an important contribution of brain areas supplied by the PCA to memory function.

The Wada test in Austrian, Dutch, German, and Swiss epilepsy centers from 2000 to 2005: a review of 1421 procedures.

Twenty-six Austrian, Dutch, German, and Swiss epilepsy centers were asked to report on use of the Wada test (intracarotid amobarbital procedure, IAP) from 2000 to 2005 and to give their opinion regarding its role in the presurgical diagnosis of epilepsy. Sixteen of the 23 centers providing information had performed 1421 Wada tests, predominantly the classic bilateral procedure (73%). A slight nonsignificant decrease over time in Wada test frequency, despite slightly increasing numbers of resective procedures, could be observed. Complication rates were relatively low (1.09%; 0.36% with permanent deficit). Test protocols were similar even though no universal standard protocol exists. Clinicians rated the Wada test as having good reliability and validity for language determination, whereas they questioned its reliability and validity for memory lateralization. Several noninvasive functional imaging techniques are already in use. However, clinicians currently do not want to rely solely on noninvasive functional imaging in all patients.

Standard versus tailored left temporal lobe resections: differences in cognitive outcome?

UNLABELLED: This study explores differences in cognitive outcome after a standard resection (SR) or tailored (TR) in 100 patients with left temporal lobe epilepsy, controlling for extent in the three lateral gyri. Comparing preoperative to 6-month postoperative performance on a battery of intelligence, language and verbal memory tests revealed the following: a differential effect of the procedure was found for digit span, a short-term memory and attention task, the SR group showing a gain and the TR group a loss postoperatively. This could be explained by a rather large improvement of the SR group with below average resection sizes in the superior temporal gyrus (STG) (<2.8 cm), which small resections are nearly absent in TR resections. Effect of larger extent on the STG in the SR group was related to a decrease in verbal intelligence and a tendency in auditory comprehension which poses a risk in 'large' standard resections. Differences in extent of resection on the other gyri did not cause differences in effects on language functioning or verbal memory. CONCLUSIONS: In standard anterior temporal lobe resections only (without intraoperative language mapping) up to a limit of 4.5 cm, large resections on the STG pose a risk for declining on verbal IQ and auditory comprehension. In general, tailored resections (with language mapping) result in decline on a task measuring short-term memory and attention.

Verbal memory decline after temporal epilepsy surgery?: A 6-year multiple assessments follow-up study.

OBJECTIVE: To assess the long-term effects of temporal lobe epilepsy surgery on verbal memory. METHODS: We assessed verbal memory performance as measured by a verbal learning test ("15 Words Test," a Dutch adaptation of Rey's Auditory Verbal Learning Test) before surgery and at three specific times after surgery: 6 months, 2 years, and 6 years in 85 patients (34 left temporal lobe [LTL] vs. 51 right temporal lobe [RTL]). An amygdalo-hippocampectomy and a neocortical temporal resection between 2.5 and 8 cm were carried out in all patients. RESULTS: LTL patients showed an ongoing memory decline for consolidation and acquisition of verbal material (both 2/3 SDs) for up to 2 years after surgery. RTL patients at first showed a gain in both memory acquisition and consolidation, which vanished in the long term. Breaking the group up into a mesiotemporal (MTS) group and a non-MTS group showed clear differences. The group with pure MTS showed an overall lower verbal memory performance than the group without pure MTS, in the LTL group more pronounced than in the RTL group. After surgery, both pathology groups showed an ongoing decline for up to 2 years, but the degree of decline was greater for the LTL patients with MTS compared with the non-MTS group. Becoming and remaining seizure-free after surgery does not result in a better performance in the long term. Predictors of postoperative verbal memory performance at 6 years after surgery were side of surgery, preoperative memory score, and age. CONCLUSIONS: The results provide evidence for a dynamic decline of verbal memory functions up to 2 years after left temporal lobectomy, which then levels off.

Relationships between epilepsy-related factors and memory impairment.

OBJECTIVES: In this study, we will explore the effect of epilepsy-related factors such as: 'type of epilepsy, 'site and side of focus localisation' and 'age at onset', as well as four seizure-related factors: 'years with continuing seizures', 'seizure type' and 'seizure frequency', and the treatment factor 'adverse effects of the medication', on memory impairment. Additionally, we explored whether these epilepsy factors are related to different aspects of memory, i.e. short-term recall vs long-term recall, learning, and verbal memory vs non-verbal memory. MATERIAL AND METHODS: A total of 252 patients with epilepsy and subjective memory complaints were consecutively included from the three epilepsy centres in the Netherlands. To assess memory functions the Wechsler Memory Scale-Revised (WMS-r), and the Dutch version of the California Verbal Learning Test for verbal list learning, was administered. RESULTS: A multivariate analysis of variance (MANOVA) did not show statistically significant effects of the epilepsy factors on memory for the total study sample. For the patients with a unilateral epileptogenic focus in the temporal lobes, MANOVA showed statistically significant effects of lateralisation, with most impairment for patients with left temporal lobe epilepsy and, independently, seizure frequency and 'years with seizures'. CONCLUSION: We may conclude that epilepsy-related dysfunctions in the temporal lobe are the dominant risk factor for developing memory problems, specifically verbal memory problems (verbal learning and problems consolidating verbal information), with more severe impairments with continuing seizures and when seizure frequency is high.

Long-term effects of temporal lobectomy on intelligence.

OBJECTIVE: To characterize the long-term effects of anterior temporal resection on intelligence. METHODS: Twenty-eight left temporal lobectomy (LTL) and 43 right temporal lobectomy (RTL) patients were followed at standard time points for at least 6 years after surgery. RESULTS: The average gain 6 years after operation was 3.6 Verbal IQ (VIQ) points and 10.3 Performance IQ (PIQ) points in LTL patients and 2.9 VIQ points and 7.7 PIQ points in RTL patients. A seizure-free outcome did not influence the increase in IQ, nor was the extent of resection related to IQ scores at the 6-year follow-up. Patients with exclusively mesial temporal sclerosis did not perform as well as patients with other pathologies, both before and after surgery. Major predictors of improved performance at 6 years were initial higher level of performance and lower age at surgery. Much of the observed improvement may be related to retest effects. CONCLUSIONS: The effects of epilepsy surgery on intelligence in the long term are limited. The largest gain in VIQ is seen from 2 to 6 years after surgery.

FMRI-determined language lateralization in patients with unilateral or mixed language dominance according to the Wada test.

Due to the reported variability of the language laterality index (LI) across fMRI studies, reliable distinction between patients with unilateral and mixed language dominance is currently not possible, preventing clinical implementation of fMRI as a replacement for the invasive Wada test. Variability of the LI may be related to differences in experimental and control tasks, and statistical methodology. The goal of this study was to improve detection power of fMRI for hemispheric language dominance by using a combined analysis of four different language tasks (CTA), that has previously shown more reliable and robust Lls in groups of normal volunteers than individual task analyses (see Ramsey et al). The CTA targets brain areas that are common to different language tasks, thereby focusing on areas that are critical for language processing. Further advantage of the CTA is that it is relatively independent of specific task and control conditions. 18 patients with typical (i.e., left-sided, n = 11) and atypical (i.e., right-sided or mixed, respectively, n = 3 and n = 4) language dominance according to the Wada test underwent fMRI (groups respectively denoted as WadaL, WadaR, and WadaM patients). Statistical methodology (including thresholding of activity maps) was fixed to assure a user-independent approach. CTA yielded better results than any of the individual task analyses: it was more robust (on average 2.5 times more brain activity was detected due to its higher statistical power) and more reliable (concordance for WadaL, WadaM and WadaR patients was respectively 10/11 (91%), 3/4 (75%), and 2/3 patients (67%)). Overall, a significant correlation was observed between frontal and temporoparietal LIs. Remarkably, brain activity for WadaM patients was significantly lower than for WadaL or WadaR patients, and a dissociation in lateralization was observed between frontal (right-sided) and temporoparietal (left-sided) activity in three of four patients. Of the individual task analyses, the verb generation task yielded best results for patients with unilateral language dominance (same concordance as CTA). However, in contrast to CTA results, the verb generation task was unable to identify WadaM patients (concordance in one of four patients). In conclusion, the CTA is a promising approach for clinical implementation of fMRI for the prediction of hemispheric language dominance.

Lateralization of auditory rhythm length in temporal lobe lesions.

In the visual modality, short rhythmic stimuli have been proven to be better processed (sequentially) by the left hemisphere, while longer rhythms appear to be better (holistically) processed by the right hemisphere. This study was set up to see if the same holds in the auditory modality. The rhythm task as originally designed by Seashore was computerized and is part of the Fepsy Neuropsychological battery. This task was performed by 85 patients with intractable temporal lobe epilepsy (left TLE = 32; right TLE = 53) enrolled in the Dutch Collaborative Epilepsy Surgery Program. They performed the task before and 6 months after surgery. The task consists of 30 pairs of rhythmic patterns in 3 series of 10 items. The series contains patterns of 5, 6, or 7 notes. The purpose is to indicate whether the two patterns are the same or different. Reaction times are also measured. If the hypothesis is true, the short-item sequence will be better processed by patients with right temporal lobe epilepsy (nonimpaired left temporal lobe), the longer sequence will be better processed by the left temporal epilepsy group (nonimpaired right temporal lobe). No overall laterality effect on rhythm perception could be found and no difference was found between both test moments. IQ did not correlate with rhythm performance. However, there was an interaction effect of laterality and rhythm length on performance and reaction time. This effect can be explained by the increase after the operation of the score of the left focus group and a decrease in the right focus group on the longer rhythms. This effect was somewhat less strong in the reaction times: a clear tendency for faster reaction times after surgery in the left and longer reaction times in the right focus group. The effect could not be explained for by the difference in extent of resection in either temporal lobe. This study showed that memory for and discrimination of auditory rhythm is dependent on which hemisphere is used in processing. The effect could be demonstrated for the right hemisphere, which uses a holistic processing of stimuli, which outperforms the left in rhythms consisting of a long sequence. In left temporal resections an improvement occurs on the longer rhythms and in right temporal resections the performance on the longest rhythms decreases.

Memory Complaints in Medically Refractory Epilepsy: Relationship to Epilepsy-Related Factors.

This study reports the results of a multicenter study on memory complaints in 252 patients with epilepsy who presented with subjective complaints about memory problems in daily life. Memory complaints were measured with a standardized memory questionnaire (GKLE). The main purpose was to analyze the type of memory complaints and to examine the relationship between subjective complaints and several epilepsy-related factors. These include seizure type, lateralization and location of the focus, etiology, duration, age at onset, and antiepileptic medication. As expected patients experienced significantly more memory complaints. In particular, patients of older age and higher intelligence level complained more about their memory functioning. Although the clinical significance is marginal, neuroticism showed a significant relationship to the total complaint score. The total amount of subjective complaints is not related to the localization or lateralization of the epileptic disturbances. Patients with a longer duration of epilepsy complained significantly more about memory problems, especially about retrieving information from memory. All other epilepsy-related factors showed no relationship to memory complaints.

The wada test: prediction of focus lateralization by asymmetric and symmetric recall.

PURPOSE: The intracarotid amytal test is commonly used as a predictor of memory dysfunctioning after anterior temporal lobe resection (ATL) for intractable epilepsy. Asymmetry in memory scores can provide focus lateralizing information. In this study the predictive value of a set of Wada test parameters was analyzed, including patients with symmetrical memory scores. METHODS: The Wada test was carried out in 226 patients undergoing ATL (94 L, 132 R). Data were collected on item recognition (five items), story recall, amytal dose, presentation time, EEG and arterial filling of amytal. A logistic regression analysis was performed on these data in order to find a set of variables which could best predict the side of seizure onset. RESULTS: The analysis yielded four variables, i.e. both memory scores, story recall after right-sided injection and presentation time of stimuli after left-sided injection which could correctly predict seizure lateralization in 85% of the cases. Misclassification was lower for right foci than for left foci. Seizure outcome was four times more favourable in the correctly classified patients. CONCLUSIONS: The results suggest that prediction of focus lateralization in temporal lobe epilepsy can be fairly exact even if left/right memory scores are equal. Performing the Wada test with only five memory items keeps the time window of active amytal short enough and gives accurate information about contralateral temporal lobe functioning. The classification scheme can be useful in predicting a lowered chance of seizure freedom.

[No adverse effects on intelligence 6 years after surgery for epilepsy]. / Geen nadelige effecten op de intelligentie 6 jaar na chirurgische behandeling wegens epilepsie.

OBJECTIVE: To evaluate the long-term effects of epilepsy surgery on intelligence. DESIGN: Prospective descriptive. METHOD: The group included 20 patients of the Instituut voor Epilepsiebestrijding, Heemstede, and the Epilepsiecentrum Kempenhaeghe, Heeze, the Netherlands, who suffered from medication-resistant epilepsy originating from the temporal lobe, in 9 patients from the left lobe (mean age: 33.1 years), in 11 from the right one (34.6 years). The epilepsy focus was removed surgically (Academic Hospital, Utrecht). The scores on the 'Wechsler adult intelligence scale' (WAIS) were determined before the operation and 6 months, 2 years and 6 years after operation. RESULTS: The mean WAIS IQs before operation were: verbal IQ (VIQ): 111.8 and performance IQ (PIQ): 117.7 in the group treated on the left and VIQ: 113.5 and PIQ: 112.4 in the group treated on the right. The mean gains 6 years after operation were 0.8 and 2.6 VIQ-points and 8.7 and 8.5 PIQ-points respectively. In the patients operated on the left the difference between VIQ and PIQ was significant 2 and 6 years after operation. The increase in IQs remained within what could be expected in retests. Only for the VIQ of patients treated on the left was a smaller retest effect found. CONCLUSION: These figures show that in the long term epilepsy surgery does not have an adverse outcome on the intelligence.

Antiepileptic drug-related cognitive complaints in seizure-free children with epilepsy before and after drug discontinuation.

The cognitive complaints reported by children and their parents, as subjectively associated with antiepileptic drug (AED) treatment, were evaluated in seizure-free children before and after drug discontinuation. The aim of the design was to isolate the cognitive side effects of AEDs from other factors, such as the effect of seizures. Our inventory explored the following areas: "alertness," "concentration," "activation/ tiredness," "memory," "drowsiness," "depression," "aggressiveness," and "hyperactivity," using a 5-point Likert scaling procedure. One hundred two eligible patients were selected, each matched with a healthy control and assessed when still on antiepileptic medication. All children were seizure free for at least 1 year. The medication was then discontinued gradually over a 3-month period. Four months after the children were completely medication free, a second assessment was carried out, but only in the 83 children who remained seizure free and in their matched controls. The results of the reports made by the children themselves did not show differences with the matched controls, and only showed improvement after drug discontinuation for complaints about "tiredness." Parents of the children with epilepsy reported significant improvement in all areas related to "alertness and activation" after discontinuation of the drugs. The finding that only a limited number of children have cognitive complaints, both when still on AEDs and after discontinuation, may be in line with the reports that the major factor contributing to quality of life is whether patients are seizure free or still have seizures. All patients in this study were seizure free for a period >1 year, which may have caused the favorable pattern of response in our patient group.

Cognitive effects of a new pyrrolidine derivative (levetiracetam) in patients with epilepsy.

1. A new pyrrolidine derivative (levetiracetam), resembling piracetam, was given as antiepileptic concomitant drug to patients with chronic epilepsy. 2. In a single-blind add-on rising-dose study the cognitive side-effects were investigated twice after one week of administration. 3. The results did not show any significant changes in cognitive performances.

Withdrawal of antiepileptic medication in children. Correlation of cognitive function and plasma concentration--the multicentre 'Holmfrid' study.

Eighty-three patients with epilepsy and 83 matched controls completed 12 computerized cognitive tests while on antiepileptic drugs and six months later when they had been medication-free for three to four months. All patients had been seizure-free for more than one year and were on monotherapy with carbamazepine (CBZ, n = 56), valproate (VPA, n = 17), or phenytoin (PHT, n = 10). The tests and plasma concentration collection were done at noon. The mean peak plasma concentrations in the CBZ patients were as follows: 31% below 30 mumol/l, 48% between 30 and 42 mumol/l and 21% above 42 mumol/l. No difference in performance could be detected between the groups. One significant correlation between plasma concentration and test results was found. The mean VPA concentration was 625 mumol/l (S.D. 189). A tendency towards a weak negative correlation between test results and plasma concentration was present. The PHT patients' therapeutic range had a mean concentration of 32.0 mumol/l (S.D. 18.5). One significant correlation between a memory test and plasma concentration could be detected. Overall, the patients in the different antiepileptic groups performed less good than the control group and in a few cases the differences were statistically significant when compared either before or after withdrawal. A comparison of the changes after withdrawal showed improvement in the majority of tests, but these changes were also present in the matched control group.

Cognitive side-effects of phenytoin compared with carbamazepine in patients with localization-related epilepsy.

In continuation of an earlier study of our group (Neurology, 43 (1) (1993) 41-51), we present the results of an investigation of the adverse effects of carbamazepine versus phenytoin on cognitive function. Two groups of twenty-five patients are compared in an open, parallel group and non-randomized clinical investigation: a group of patients on carbamazepine (CBZ) monotherapy versus a group of similar size on phenytoin (PHT) monotherapy. The two groups do not show significant differences on variables that could confound the comparison of drug-specific adverse effects: age, gender, intelligence, type of epilepsy, seizure type, seizure frequency, EEG focus and age at onset of the epilepsy. All patients were investigated with a comprehensive neuropsychological test battery ('FePsy'), assessing the cognitive domains of 'speed factors', memory and attention. The results show lower performance in the PHT group compared to the CBZ group on all tests measuring motor speed. Additionally, there is evidence that PHT also affects the speed of central 'higher cortical' processing systems. Our investigation also shows slower performance in tasks that measure speed of information processing ('mental speed'). The other investigated areas, i.e. short-term memory, long-term (verbal and non-verbal) memory and selective attention, do not reveal statistically significant differences between the two groups. These results reconfirm that patients on PHT may suffer from cognitive side-effects even when the medication is sufficiently controlled and the drugs are given within the assumed therapeutical interval.

Cognitive performance in learning disabled children with and without epilepsy.

Cognitive functioning and educational achievement were examined in learning disabled children with epilepsy (n = 65) and without epilepsy (n = 122) in order to explore whether children with epilepsy show unique types of learning problems, different from those in other learning disabled children. The learning disabled children with epilepsy tended to perform better on tests of verbal intelligence, certain achievement-related abilities and were better in one area of academic achievement, i.e. spelling. Despite their superior performance in these areas, the learning disabled children with epilepsy were slower than those without epilepsy and regular education controls (n = 100) on simple auditory and visual reaction tasks as well as on a multiple decision reaction task and a visual searching task. The results obtained with the school achievement tasks provide no clear evidence for specific types of learning impairment in children with epilepsy. Learning disabled children with epilepsy do not appear to have educational needs different from those of other learning disabled children.

[Results of the neurosurgical treatment of patients with drug-resistant epilepsy: psychosocial aspects]. / Resultaten van neurochirurgische behandeling bij patiënten met medicatieresistente epilepsie: psychosociale aspecten.

OBJECTIVE: Evaluation of psychological and social functioning of patients after neurosurgical treatment for pharmacologically intractable epilepsy. DESIGN: Descriptive study. SETTING: University Hospital Utrecht in collaboration with the Institute for Epilepsy in Heemstede, the Netherlands. METHOD: After two years' follow-up, social functioning, vocational adjustment and emotional stability were assessed in a group of 13 adult patients treated surgically between 1985 and 1992 for intractable seizures. RESULTS: The majority of the patients improved or at least maintained their social and employment status. Emotional functioning showed minor changes for anxiety and emotional stability. CONCLUSION: The outlook for improvement in psychosocial functioning for epileptic patients treated neurosurgically is promising. Minor changes were found in emotional stability.

Memory complaints in epilepsy: correlations with cognitive performance and neuroticism.

Subjective memory functioning was assessed by a questionnaire in 102 patients with epilepsy. Factor analysis of their responses yielded five factors: (1) Absentmindedness, (2) Retrieval, (3) Memory for Semantic Structures, (4) Childhood Memories and (5) Rote Memory. Scales representing the factors were constructed. On all scales, patients (n = 71) who had been specifically referred for an evaluation of subjective memory problems showed moderate to large differences from normal Controls (n = 111) in complaint scores, indicating adequate sensitivity of the scales to clinically significant complaint levels. By contrast, candidates for epilepsy surgery (n = 31) resembled the Controls in their perceived memory status, showing a moderately elevated complaint level on only one of the factor based scales. Relationships of subjective memory difficulties to performance on objective tests of memory and other relevant cognitive functions as well as neuroticism were examined. The two epilepsy groups were fairly similar in their test performance, but differed markedly in their subjective memory problems. Also, correlational analysis revealed only a single weak correlation between cognitive tests and subjective memory ratings. The present findings indicate that there is no simple relationship between subjective evaluations of memory and test performance. Patients' memory complaints do not accurately predict disturbances that can be measured on standard neuropsychological tests. Such complaints may be related more to neuroticism. Also, psychosocial difficulties which may accompany chronic disorders in general may have to be invoked to account for memory complaints in people with epilepsy. The epilepsy itself does not appear to be a critical factor in producing memory complaints.

Withdrawal of antiepileptic medication in children--effects on cognitive function: The Multicenter Holmfrid Study.

We present 100 children diagnosed with epilepsy who were seizure-free for more than 1 year and still on monotherapy of antiepileptic drugs (AEDs). We matched each child with a healthy classmate and performed neuropsychological testing and EEG before and after complete withdrawal of the AEDs. The withdrawal phase lasted 3 months, but the dose decrease was individualized for each patient. Three to 4 months after complete withdrawal of the drug all patients were reassessed. Patients with seizure relapse are excluded from the study. Seventeen patients are regarded as dropout, 11 because of seizure relapse and six because of protocol violation. The remaining 83 patients were treated with carbamazepine (n = 56), valproic acid (n = 17), or phenytoin (n = 10). Serum concentrations of the AEDs were measured using peak plasma levels that were taken immediately before or after psychological testing. We used neuropsychological tests to assess psychomotor function and "central" cognitive processing such as information processing or memory function. We found significant improvement attributable to drug withdrawal on only one of the cognitive tests, namely, psychomotor speed, suggesting that the impact of AED treatment on higher-order cognitive function is rather limited. In addition, we found group differences between the epilepsy group and the control group at baseline that persisted after drug withdrawal. Subsequent analysis showed some factors that may have contributed to these group differences. First, patients with a former diagnosis of absence seizures show lower scores both at baseline and after drug withdrawal. We may assume that the seizure propensity has not disappeared completely in these patients. Some evidence is found that phenytoin may have a different cognitive profile than carbamazepine, with more impairment on tests that measure motor and mental speed. Again, this impairment persists after drug withdrawal.

Subtest profiles of the WISC-R and WAIS in mentally retarded patients with epilepsy.

In this study, WISC-R and WAIS subtest profiles of mentally retarded patients with epilepsy are analysed with respect to the Verbal-Performance IQ Discrepancy scores and rank order of mean subtest scores. The relative strengths and weaknesses in cognitive patterns of this sample are compared with subtest profiles mentioned in the literature on mentally retarded populations and samples of normal intelligent patients with epilepsy in order to determine the impact of epilepsy factors on cognition. The results indicate that people with mental retardation have problems with the verbal subtests Arithmetic, Vocabulary and Information, while patients with epilepsy have problems with Coding (Digit Symbol), Digit Span and Information. For this sample of mentally retarded patients with epilepsy, the most difficult subtests are Digit Span and Coding. The results concerning subtest profiles in different populations are discussed in light of the deleterious impact of epilepsy on cognition, which may superimpose the general effect of brain damage in mentally retarded patients. It is suggested that especially attentional processes, as measured with the subtest Coding, are vulnerable for epilepsy factors.