Memory functioning in children and adolescents with frontal and temporal lobe epilepsy

Working memory (WM) refers to a temporary mental „workspace‟ that allows individuals to register and manipulate information to solve complex problems. The WM system acts in concert with, and has direct influence on, other memory systems, such as long-term memory (LTM), to facilitate learning and development. Many studies indicate that WM skills are vital for acquiring basic academic skills. To date, the literature investigating the memory impairments in children with focal epilepsy has been biased toward populations with temporal lobe epilepsy (TLE), with little consideration to frontal lobe epilepsy (FLE). Given theories of WM (eg Baddeley, 1974) it would be reasonable to postulate greater deficits in FLE rather than TLE as frontal systems are more pertinent to WM than other brain regions. Similarly LTM would be expected to be more vulnerable in TLE, given the role of temporal lobe structures in memory, with both deficits influencing academic achievement. This study aimed to assess the memory functioning in well-characterised samples of children with TLE and FLE, by examining not only absolute levels of impairment, though also the relationships and factors which are important to efficient memory, learning, and academic achievement, using well-validated and standardised neuropsychological measures and parent ratings. Specifically, the study sample consisted of children aged six to sixteen years with well-controlled FLE (n=18) and TLE (n=21), recruited from Royal Children's Hospital, Melbourne, Australia. Children's WM, verbal and visual LTM, and academic skills were assessed Results indicate that in many domains of memory processing children with well-controlled FLE and TLE do not differ, and seizure variables were not significantly associated with memory performance. With respect to each syndrome, children with FLE do not demonstrate wide-ranging working memory impairment, though these children demonstrated frontal lobe inefficiencies indicated by higher frequency of learning errors and impaired strategy utilisation on the CVLT-C. In contrast, children with TLE demonstrate working memory impairment, indicated by impaired performance relative to normative standards on all measures of the WMTB-C, and inconsistent strength of relationships between subcomponents of working memory. Clinical indication of a central executive deficit in this group may in actuality reflect a more primary impairment of storage capacity. Academic skills were largely at expectation relative to normative standards in both groups. The central executive remained the strongest predictor of LTM, spelling, reading, math, and sentence comprehension in both groups. Parent ratings of memory performance in children were not predicted by seizure variables or objective memory performance, highlighting the need for further work to understand the predictive factors for everyday memory.