Memory after epilepsy surgery in children

Learning is a central activity for children. Infants and toddlers learn about their body and their physical and social environment through exploration and play. Schoolchildren spend many hours per week learning academic skills and memorizing facts. In addition to learning as an activity, memory and learning are likely to have an integral function in (cognitive) development as a whole. It can be reasoned, therefore, that interventions that affect memory and learning early in life may have cumulative effects for cognitive function generally. Yet, despite the centrality of memory and learning, the effects of childhood epilepsy surgery on development of memory and learning are unclear. Given the results obtained in adults, we hypothesized that epilepsy surgery (and in particular temporal resection) would affect memory and learning in at least some – but probably not all – children. We further theorized that surgery might affect some aspects of memory and learning in one child, and other aspects in another child. To test these hypotheses, we performed a prospective, longitudinal, controlled study with consecutive inclusion of childhood epilepsy surgery patients. All patients aged 18 years or younger at surgery participated in extensive, age-appropriate neuropsychological assessments including – but not limited to – tests of memory and learning, both before surgery and six, 12 and 24 months after surgery (note that though all patients aged 18 or younger were included in the project, not all of the studies include the entire age range). For each patient, two age- and sex-matched children without a history of neurological disease were tested at the same intervals to control for effects of aging (i.e., development) and repeated testing. In addition, we performed a retrospective study of medical files to identify variables associated with cognitive outcome in this population. The results show that while – like in adults – verbal memory is particularly vulnerable to left temporal surgery, the vulnerability of visual memory – though clearly present – does not follow anatomical (or etiological) categories. The impact of surgery on semantic memory in children appears to be mediated by reduced efficiency in retrieving the required information, rather than a deficit in semantic memory per se. In very young children, a measure of habituation suggests a close correspondence between memory and general cognitive development, although important caveats remain regarding the interpretation of recognition memory tests - which typically subsumes habituation measures. The observed association between parental education and intelligence quotient (IQ) change after surgery reinforces the suggestion that the environment may influence general cognitive development through learning (though a genetic contribution cannot be ruled out).