Test-retest IQ changes of epilepsy patients: assessing the influence of practice effects

Mechanisms for Cognitive Impairment in Epilepsy: Moving Beyond Seizures

There has been a major emphasis on defining the role of seizures in the causation of cognitive impairments like memory deficits in epilepsy. Here we focus on an alternative hypothesis behind these deficits, emphasizing the mechanisms of information processing underlying healthy cognition characterized as rate, temporal and population coding. We discuss the role of the underlying etiology of epilepsy in altering neural networks thereby leading to both the propensity for seizures and the associated cognitive impairments. In addition, we address potential treatments that can recover the network function in the context of a diseased brain, thereby improving both seizure and cognitive outcomes simultaneously. This review shows the importance of moving beyond seizures and approaching the deficits from a system-level perspective with the guidance of network neuroscience.

Longer duration of epilepsy and earlier age at epilepsy onset correlate with impaired cognitive development in infancy

We assessed the impact of age at onset of epilepsy and duration and frequency of seizures on cognitive development in children less than 3 years old. Retrospective analysis was conducted on clinical data and neuropsychological testing of 33 infants with epilepsy. Developmental quotients were calculated and were correlated with age at epilepsy onset, duration of epilepsy, seizure frequency, brain pathology, and types of seizures (with/without spasms) as potential predictors. Infants with longer duration and earlier onset of epilepsy performed worse on developmental neuropsychological testing. Regression analyses showed that age at epilepsy onset and percentage of life with epilepsy were both strongly associated (regression model P<0.0001) with developmental quotient. There was no correlation with seizure frequency. Infants with spasms had worse developmental quotients than infants without spasms (P<0.001). These results suggest that duration of epilepsy and age at onset may be the best developmental predictors during the first years of life in patients with epilepsy. Early aggressive intervention should be considered.

Antiepileptic drug-induced cognitive adverse effects: potential mechanisms and contributing factors

Cognitive dysfunction is frequently observed in patients with epilepsy and represents an important challenge in the management of patients with this disorder. In this respect, the relative contribution of antiepileptic drugs (AEDs) is of relevance. The fact that a considerable number of patients require AED therapy for many years, or perhaps even a lifetime, emphasizes the need to focus on the long-term adverse effects of these drugs on cognition. The most prevalent of the CNS adverse effects observed during AED therapy are sedation, somnolence, distractibility, insomnia and dizziness. Sedation, in particular, is associated with most of the commonly used AED therapies. Nevertheless, cognitive function in individuals with epilepsy may also be influenced by several factors, of which AEDs constitute only one of many putative causes. In general terms, most studies agree that some differences exist among the older AEDs with regard to the effects on cognition, and some newer generation molecules may have a better cognitive profile than older AEDs. The mechanisms of action are an obvious determinant; however, there is still a lack of evidence for differentiation between available drugs with regard to cognitive effects. Some authors have suggested that there may be different cognitive effects associated with individual drugs; however, the question as to whether there are more specific deficits related to the action of individual drugs remains unsolved. There seems to be agreement that polytherapy and high-dose treatment can produce cognitive adverse effects and when high dosages or adjunctive polytherapy is needed, the balance between benefits and disadvantages may be negatively biased against drug treatment. Thus, drug treatment requires careful balancing in the attempt to reach maximal seizure control while avoiding neurotoxic adverse effects. Finally, the mood status of the patient and clinical relevance of the information obtained by neuropsychological testing represent important variables that need to be taken into account when discussing cognitive adverse effects of AEDs.

Intellectual impairment in patients with epilepsy in Ile-Ife, Nigeria

INTRODUCTION

Epilepsy is the most common non-infectious neurologic disease in developing countries such as Africa, including Nigeria. This study was designed to assess the intellectual performance of patients with epilepsy (PWE) in Nigeria hoping that the result will serve as the basis for educational, vocational, and social counseling.

METHODS

Forty-one PWE were studied along with 41 age-, sex- and education-matched healthy controls. A questionnaire was developed and applied to all subjects and history was taken from patients and eyewitness. The intellectual function of each subject was assessed with the aid of Wechsler Adult Intelligence Scale adapted for Nigerians. All patients subsequently had electroencephalography (EEG) performed and the EEG findings were noted. SPSS statistical package was used to analyze the data.

RESULT

The PWE performed poorly on the verbal IQ, performance IQ, and full scale IQ scores when compared with controls (P < 0.05) and 20% of PWE had mental retardation. Long duration of epilepsy, long duration of antiepileptic drug therapy, younger age at onset of epilepsy, increased frequency of seizures, and low educational status were found to have negative impacts on intellectual performance in PWE (P < 0.05) while seizure types and type of antiepileptic drugs (carbamazepine or phenytoin) did not influence intellectual performance.

CONCLUSION

This study shows that PWE had significant intellectual impairment when compared with controls. In addition, long duration of epilepsy, long duration of AED therapy, earlier age of onset, increased seizure frequency, and low educational status had a negative impact on intellectual functioning in PWE.

Verbal cognition and attention deficits do not explain the verbal memory decline associated with pharmacoresistant partial epilepsy

The aim of this study was to explore whether change in verbal memory with time in patients with epilepsy is influenced by performance on tasks assessing verbal cognition or attention/processing speed. Thirty-six patients and twenty-five healthy controls were tested twice with median retest intervals of 4.8 and 3.1 years, respectively. Aspects of verbal memory, verbal cognition, and attention/processing speed were assessed. Decline in one verbal memory variable (Cronholm-Molander Memory Test Paired Associates -- Delayed Recall) was the strongest correlate of epilepsy. The second strongest correlate was a decrease in one attention/processing speed variable (Digit Symbol). The relationship between decline in verbal memory and epilepsy was not influenced by the decline in attention/processing speed, and the results did not support the notion that limited mental reserves as reflected in impaired verbal cognition or attention/processing speed can explain the relationship between verbal memory and epilepsy.

Do practice effects on Wechsler's Performance subtests relate to children's general ability, memory, learning ability, or attention?

The nature of practice effects on the Wechsler Intelligence Scale-Third Edition (WISC-III) Performance Scale was examined for 51 middle-class White children ages 11 to 13 years. The participants were tested twice on the six WISC-III Performance subtests (mean interval = 13 days) to determine whether the gain scores were significantly related to the children's ability level, memory, learning ability, and attention and motivation. Measures of these constructs were administered during the initial evaluation. Results indicated that retest gains on the separate subtests were uncorrelated with each other. Multiple regression analyses yielded some significant and meaningful results (e.g., a measure of long-term memory was a significant predictor of gains on Object Assembly), but, in general, few meaningful relations were yielded in these analyses.

Multidisciplinary approach to childhood epilepsy: exploring the scientific rationale and practical aspects of implementation

The management of childhood epilepsy requires attention to more than seizure control because children with epilepsy often suffer from comorbidities that lead to an increased frequency of psychiatric disease, learning difficulties, and other problems of psychosocial development. These comorbidities can stem in part from the same genetic traits that determine seizure susceptibility. Thus, mutations affecting potassium, calcium, and sodium channels have been linked with epilepsy syndromes and affective and behavioral abnormalities. It is important to consider the effect of antiepilepsy drugs on comorbid conditions and the effect on seizures of drugs used to treat comorbidities. A number of antiepilepsy drugs are available that have minimal adverse cognitive effects, and some can have positive effects on mood and behavior. Epilepsy in a child is a condition that affects and is affected by the entire family situation. In addition to appropriate neuropsychologic evaluation, optimal management of childhood epilepsy also can require the involvement of the social worker, advanced practice nurse, and educational specialist. Many elements of the multidisciplinary team approach can be instituted by the child neurologist in community practice and at large, specialized epilepsy centers.

The relative influence of epileptic EEG discharges, short nonconvulsive seizures, and type of epilepsy on cognitive function

PURPOSE

This study addressed whether cognitive impairment in children with epilepsy is caused by disease-related stable factors, such as the type of epilepsy, or by acute effects of paroxysmal epileptic activity such as epileptic EEG discharges. We studied a nonselected group with short nonconvulsive seizures, as these seizures may elude detection and may therefore persist over a longer period. In this group, the diagnostic issue is to differentiate between the combined effects of several epilepsy-related factors on cognition.

METHODS

All children were assessed with 32-channel EEG, synchronized with a computerized cognitive test system and a video-monitoring system. Recording time was 2 h. The primary inclusion criteria were unclear seizures and fluctuations in cognitive performance and/or frequent epileptic EEG discharges in a recent EEG.

RESULTS

One hundred fifty-two patients met the inclusion criteria; 31 patients appeared not to have a diagnosis of epilepsy and were used as a nonepilepsy control group. Our results show that type of epilepsy has an impact on stable cognitive functions, such as educational achievement. Paroxysmal epileptic activity (acute effects of seizures and epileptic EEG discharges) affects primarily transient mechanistic cognitive processes (alertness, mental speed).

CONCLUSIONS

These results suggest that the effects of paroxysmal epileptic activity on transient cognitive mechanisms may accumulate over time and consequently affect the more stable aspects of cognitive function such as educational achievement. The clinical relevance is that early detection of the cognitive impact of seizure-related activity and subsequent treatment may prevent its detrimental impact on cognitive and educational development.

Effects of epileptiform EEG discharges on cognitive function: is the concept of "transient cognitive impairment" still valid?

In this article we review the existing evidence on the cognitive impact of interictal epileptiform EEG discharges. Such cognitive impairment occurs exclusively in direct relation to episodes of epileptiform EEG discharges and must be distinguished from (post) ictal seizure effects and from the nonperiodic long-term "stable" interictal effects caused by the clinical syndrome or the underlying etiology. Especially in patients with short nonconvulsive seizures, characterized often by difficult-to-detect symptoms, the ictal or postictal effects may be overlooked and the resulting cognitive effects may be erroneously related to the epileptiform EEG discharges. The existing epidemiological data show that the prevalence of cognitive impairment during epileptiform EEG discharges is low. In one study 2.2% of the patients referred to a specialized epilepsy center for EEG recording showed a definite relationship between epileptiform EEG discharges and cognitive impairments ("transient cognitive impairment"). Several studies have sought to analyze to what extent cognitive impairment can be attributed to epileptiform EEG discharges among the other epilepsy factors (such as the effect of the clinical syndrome). These studies show that epileptiform EEG discharges have an additional and independent effect, but this effect is mild and limited to transient mechanistic cognitive processes (alertness, mental speed). This finding concurs with clinical studies that also reported only mild effects. In only exceptional cases are epileptiform EEG discharges the dominant factor explaining cognitive impairment. In addition, some studies have indicated that such mild effects may accumulate over time (when frequent epileptiform EEG discharges persist over years) and consequently result in effects on stable aspects of cognitive function such as educational achievement and intelligence. Hence, the clinical relevance is that early detection of cognitive effects of epileptiform EEG discharges and subsequent treatment may prevent a definite impact on cognitive and educational development. The disruptive effects of epileptiform EEG discharges on long-term potentiation, as established in animal experiments, may be one of the neurophysiological mechanisms underlying this accumulation. In conclusion the concept of "transient cognitive impairment" is still valid, but refinement of methodology has shown that a large proportion of presumed transient cognitive impairment can be attributed to subtle seizures, while interictal epileptic activity accounts for a much smaller part of the cognitive effects than previously thought. In particular cryptogenic partial epilepsies are associated with the risk of cognitive impairment. We hope that increased clinical awareness of this need for early detection will stimulate longitudinal and prospective research that eventually also will provide an answer to the questions of when and how epileptiform discharges that are not part of a seizure need to be treated.

Minimal model to document psychometric change after standard anterior temporal lobectomy for intractable seizure disorder

Neuropsychological assessment of persons with epilepsy is recommended whenever neurosurgery is considered as an alternative therapy for seizure disorders refractory to ordinary medical management. Although psychological assessment is common in centers specialized in the care of epilepsy patients, standardized protocols are not common. This study addresses the question of the optimal minimal test battery necessary to differentiate groups of right-handed patients with refractory, complex partial seizure disorder who receive either right or left anterior temporal lobectomy or no surgery. No variable differentiated the groups before surgery. Only Logical Memory-Immediate of the Wechsler Memory Scale differentiated the groups following surgery. This finding is consistent with the literature.

Relative influence of epileptic seizures and of epilepsy syndrome on cognitive function

Cognitive impairment is frequently observed in children with epilepsy. We aimed at addressing to what extent cognitive function is affected by paroxysmal epileptiform activity with or without clinical seizures or by clinical features characteristic of the epilepsy syndrome. To this purpose, combined electroencephalographic (EEG) recording and cognitive testing (IQ and reaction times) were performed in 28 children. Frequent epileptiform EEG discharges significantly reduced reaction time, as did the occurrence of seizures during cognitive testing. Syndrome-related factors tended to affect cognitive functions as well: children with generalized epilepsy and high average seizure frequency obtained lower scores. Linear regression analysis showed that stable aspects of cognitive function, as reflected in intelligence level, are most closely related to the severity of the epilepsy syndrome (average seizure frequency), whereas transient aspects of cognitive function, such as reaction times, are related to the occurrence of epileptiform EEG discharges. This suggests that seizures have a direct effect on transient cognitive aspects, which can accumulate and result in effects on intelligence level.

Acute cognitive effects of nonconvulsive difficult-to-detect epileptic seizures and epileptiform electroencephalographic discharges

This study compares the acute cognitive effects of short nonconvulsive seizures with the effects of interictal epileptiform electroencephalographic (EEG) discharges in children. The study is a prospective, standardized, nonrandomized, and open clinical comparative study. Eligible patients were included when they had (a) unclear seizures and fluctuations in cognitive performance and (b) frequent epileptiform EEG discharges in a recent EEG. All children were assessed with EEG/video (Brainlab) simultaneously with computerized neuropsychologic testing (FePsy) assessing motor speed/alertness, mental speed/attention, and memory function. Eleven patients with short nonconvulsive seizures during cognitive testing were included and compared with 11 matched patients with interictal epileptiform EEG discharges during cognitive testing but without seizures. Patients included in both groups had a reconfirmed diagnosis of epilepsy. Cognitive performance for both groups was compared. Statistical analysis showed significant correlations between the number of seizures (during cognitive testing) and impaired alertness and between the duration of the ictal period and memory impairment. Interictal epileptiform EEG discharges do not have an additional independent effect on cognitive function. The results demonstrate the accumulating cognitive effect of seizures and illustrate that frequent seizures, even when these are short in duration and with subtle symptomatology, can have a substantial impact on daily life and can lead to state-dependent learning impairment. Alertness and short-term memory appeared to be the functions that are most vulnerable for the acute effects of seizures.

Prospective follow-up of intellectual development in children with a recent onset of epilepsy

In this study the intellectual development of children with a recent onset of epilepsy was compared to that of children without epilepsy. Eleven children aged 7-15 years and with mean duration of epilepsy of 2 years and 38 children without epilepsy performed three times the dutch Wechsler intelligence scale for children-revised and the Beery developmental test for visuo-motor integration. The children with epilepsy did show a significantly less gain in FSIQ score over the 11 years of follow-up. Performance intelligence scores and Beery standardized scores showed a trend towards this effect. Findings partly support the hypothesized cascadic model of deterioration, in which children with epilepsy are supposed to show a process of mental deterioration shortly after the onset of epilepsy. The lack of evidence of an absolute mental deterioration are discussed in terms of methodology, mental age and premorbid intelligence level.

Effect of seizures and epileptiform discharges on cognitive function

Several relationships have been obtained between cognitive impairment and epilepsy-related or treatment-related factors. One of these factors is treatment-related: the central cognitive side effects of the antiepileptic drugs (AEDs). The second and third factors are disease-related factors, i.e., the effect of the seizures and underlying epileptiform discharges in the brain and the localization of the epileptogenic focus in specific areas of the brain. Although most cognitive problems have a multifactorial origin and often several factors combined are responsible for the "make-up" of a cognitive problem, we have attempted to isolate one factor: the effect of seizures and epileptiform EEG discharges on cognitive function. Several studies show the impact of ictal activity, but special attention is required for the postictal and interictal effects of epilepsy on cognitive functions. This may explain substantial cognitive impairments in children with subclinical epileptiform discharges or with infrequent subtle seizures.

Issues associated with repeated neuropsychological assessments

Distinguishing practice effects from other factors in repeated neuropsychological assessments are discussed in the context of research studies and clinical/forensic assessments. Potential methodological procedures for reducing the impact of practice effects in research settings are outlined. In contrast, the potential clinical utility and interpretation of practice effects in clinical assessments and forensic evaluations are highlighted.

Wechsler adult intelligence scale-revised in the evaluation of anterior temporal lobectomy candidates

We wished to (a) determine the ability of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) to discriminate between patients with epilepsy of left or right temporal lobe (LTLE, RTLE) origin and (b) examine the ability of Kaufman's (1990) WAIS-R short forms to estimate actual Full-Scale IQ (FSIQ). We administered the WAIS-R to 215 nonretarded, left hemisphere dominant patients with invasively verified epilepsy of unilateral TL origin without lesions demonstrated by magnetic resonance imaging (MRI) (excluding mesial temporal sclerosis, MTS). LTLE (n = 106) and RTLE (n = 109) groups were compared on the WAIS-R subtests and summary IQ scores. Verbal-Performance IQ (VIQ-PIQ) discrepancies of various magnitudes, and Verbal Comprehension (VC) and Perceptual Organization (PO) scores derived by factor analysis. The LTLE group scored significantly lower on the Vocabulary subtest, and none of the other indexes reliably distinguished LTLE from RTLE patients. The Kaufman 2, 3, and 4 subtest short forms were significant predictors of FSIQ, with the 4 subtest short form having the highest correlation and lowest error of estimate.

Epilepsy surgery: non-invasive versus invasive focus localization. What is needed from a neuropsychological point of view

This article discusses the neuropsychological aspects of surgery for epilepsy, and what is needed in EEG evaluation to permit the best use of neuropsychological data to help identify the most promising surgical candidates. Neuropsychological changes after surgery are first discussed, and it is noted that changes in memory are most important with less important fluctuations in intelligence and language and with other areas showing few or no changes. Emotional and psychosocial outcomes of surgery are dependent upon relief from seizures, with substantial relief being essential for improvement to be observed. Finally, it is noted that a combination of EEG and neuropsychological variables results in the best prediction of seizure relief, but reliable EEG data are critical to this effort. Obtaining such data frequently necessitates EEG monitoring, frequently with invasive electrodes. Such information often provides the clearest information and the best chance of assisting patients with epilepsy.

Mental deterioration at epilepsy onset: a hypothesis

In this study, we hypothesized a type of mental deterioration in epilepsy, characterized as a discontinued, cascading process, i.e. a sudden mental decline in a limited time interval, immediately after the onset of the seizures. The posttraumatic epilepsy model (PTE) may appear to be exceptionally useful in avoiding one of the major methodological obstacles for testing this hypothesis, i.e. the unavailability of test results obtained with the same battery of tests prior to and directly after the onset of the seizures. We propose a multicentre study in which a large group of patients are assessed, after recovering from the direct aftermath of head injury, but before the onset of PTE. This baseline provides an opportunity for longitudinal follow-up. Full recovery from head injury before the onset of PTE is to be expected in the mild and moderate groups of closed head injury patients. In this category, approximately 2000 head injured patients have to be assessed to obtain a reasonable group of approximately 100-200 PTE patients. This group will be followed during the critical period of 2-3 years after the onset of epilepsy.

Neuropsychological aspects of learning disabilities in epilepsy

Cognitive impairment is regarded as the link between epileptic conditions and the inability to learn in school. The neuropsychological approach to learning disabilities in epilepsy, therefore, first concentrates on analyzing the differential effects of epileptic factors on cognitive function. The impact of seizure activity, localization of epileptogenic foci, and antiepileptic treatment on cognitive functioning can be evaluated based upon the results of continuous assessment with a computerized neuropsychological test system. Second, learning disabilities may be evaluated on observations made during classroom performance. Three issues seem to predominate in learning studies among disabled children with epilepsy: test-retest variability, deterioration, and the supposed specificity of the learning disabilities.

Test-retest variability in children with epilepsy--a comparison of WISC-R profiles

Reports of test-retest variability appear recurrently in relation to epilepsy. To date, the amount of information available on the stability of cognitive profiles over a number of years is limited. In this study, 45 children were assessed, using the Wechsler Intelligence Test for Children - Revised (WISC-R). The children were retested after a period of at least 2 years. A group of 20 children was tested 3 times. The average follow-up period was 4.2 years. Although most subjects in our sample had a high seizure frequency and continued to have their seizures during the period of follow-up, a marked stability of cognitive profiles is found over a period of time. These profiles show low scores for the subtests Information, Coding, Digit Span, Vocabulary and resemble profiles reported in other studies on subjects with intractable epilepsies.

Intelligence test performance of patients with partial and generalized seizures

The intellectual performance of 350 patients with seizures was examined. Seizures were classified according to the revised International Classification of Epileptic Seizures as partial (simple or complex), generalized, or partial secondarily generalized. Performance on the Wechsler Intelligence subtests served to measure intellectual ability. Patients with partial seizures performed better on Digit Span, Digit Symbol, Block Design, and Object Assembly than those with either generalized or partial secondarily generalized seizures. These subtests are functionally associated with abilities such as attention, visuospatial problem-solving, and sequencing ability.