Effect of epilepsy, seizures and epileptiform EEG discharges on cognitive function

Abstract

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 epilepto-genic focus in specific areas of the brain. Although most cog-nitive problems have a multifactorial origin and often several factors combined are responsible for the "make-up" of a cog-nitive problem, we have attempted to isolate one factor: the effect of seizures and epileptiform EEG discharges on cog-nitive 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. Cognition can be defined as the capacity of the brain to process information accurately and to program adaptive behavior (1). Cognition involves the ability to solve problems, to memorize information, or to focus attention. On a higher level, it involves dealing with complex situations creatively by transcending from the immediate circumstances to anticipate future acting (2). Epilepsy is a symptom of ictal and intenctal brain dysfunction, and the possibility that cognitive impairment may develop as a secondary symptom is therefore obvious. A considerable body of research exists with regard to the general issue of cognitive functioning in epilepsy. Speed of information processing, memory, vigilance, alertness, sustained and focused attention, and motor fluency appear to be particularly vulnerable areas of functioning in epilepsy (3-9). Although the complex relationships between daily life function, underlying cognitive impairment, and epilepsy-related or treatment-related factors have not been fully explored, the existing literature clearly shows the impact of several factors. One factor is treatment-related: the central cognitive side effects of antiepileptic Address correspondence and reprint requests to Dr. A. Aldenkamp at Epilepsiecentrum Kempenhaeghe, PO Box 6 I , NL-5590 AB Heeze, The Netherlands. drugs (AEDs). The second and third factors are disease-related, i.e., the effect of the seizures and underlying epileptiform discharges in the brain and the localization of the epileptogenic focus in specific brain areas. This article highlights one of these factors, the effect of seizures and epileptiform EEG discharges on cognitive function. In evaluating this factor, it is imperative to realize that, in practice, most cognitive problems have a multifactorial origin and the three factors combined are usually responsible for the characteristics of a cog-nitive problem. IMPACT OF SEIZURES AND EPILEPTIFORM EEG DISCHARGES ON COGNITIVE FUNCTION Seizures Diurnal seizures are reported to directly ef...

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