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.