Development after epilepsy surgery in children

The aim of this thesis was to explore the development of children who underwent epilepsy surgery, based on a series of questions that arose from the clinical care for these patients. Different aspects of cognitive outcome following epilepsy surgery in children, in particular hemispherectomy, were explored. The study addressing the influence of AED withdrawal on intelligence quotient (IQ) was performed on data from a large European multicenter group of pediatric epilepsy surgery patients (TimeToStop study). The other studies are based on standardized longitudinal assessment performed in a cohort of Dutch children who underwent epilepsy surgery in the UMCU between 1992 and 2009. Chapter 2 provides a critical review of the literature with respect to predictors of cognitive change and eventual cognitive outcome after epilepsy surgery. Early surgical intervention may halt deterioration and open the possibility for appropriate development relative to the pre-surgical situation. It is, however, unlikely that surgery results in major improvement of MDI/DQ/IQ values. True developmental decline, in the sense of permanent deterioration, is rare. Multiple variables, of which many mutually dependent, determine cognitive development after epilepsy surgery. Unraveling their respective impacts requires studies in large cohorts and advanced statistical methodology. Chapter 3 reports on the attempt to detect change in mental development or intelligence over two years following functional hemispherectomy. Measuring mental age as a marker of development allows one to at least unveil and quantify minor change in poor cognitive functioning. Such change may go unnoticed when relying on intelligence quotients. We found that MRI-abnormalities in the ‘healthy’ contralateral hemisphere are significantly associated not only with seizure recurrence but also with severe mental delay and less increase in IQ-scores after functional hemispherectomy. Chapter 5 reports on functioning of patients five to eleven years after childhood hemispherectomy. At least half a decade after hemispherectomy, cognition, behavior and daily functioning vary from profound retardation and almost complete dependence on others to relatively unproblematic functioning. We retrospectively evaluated the impact of post-surgical antiepileptic drug (AED) withdrawal on psychomotor speed (chapter 6) as well as on intelligence (chapter 7), in seizure-free children who had been operated on for pharmacoresistant epilepsy. We concluded that drug reduction after surgery improves psychomotor speed and IQ. Our findings are promising and add to the growing body of knowledge with respect to AED effects on several aspects of functioning. In Chapter 8 we report that Children of higher educated parents had on average a larger increase in IQ after surgery and a higher post-surgical – but not pre-surgical – IQ than children whose parents had completed at most lower secondary education. Environmental variables such as parental education should be considered in the prognosis of cognitive change after childhood epilepsy surgery. In Chapter 9 we report how parents and patients evaluate the decision to agree with epilepsy surgery in their children. With the benefit of hindsight, even epilepsy surgery that does not result in seizure freedom is felt to be beneficial. Most patients and their parents would opt again for epilepsy surgery. Main conclusions are discussed (Chapter 10).