Abstracts

A small number of adult studies suggest that mesial temporal lobe epilepsy (TLE) is associated with poorer memory function than lateral TLE (Helmstaedter et al., 1997). This finding is consistent with theories of memory function, which emphasize the role of hippocampal structures. Whilst lateral TLE is relatively uncommon in adult cohorts, it is a more common presentation in childhood. The study examines differences in memory function in children with mesial and lateral TLE, which has largely been overlooked by previous pediatric research., Fourty three children aged between 5-16 years participated. All had TLE associated with a unilateral temporal lesion (mesial = 31, lateral = 12). No case had undergone previous neurosurgery. No restriction was placed on seizure frequency. Subjects were administered a range of verbal and non-verbal memory tasks that reflect different theoretical orientations., The mesial group performed more poorly on a range of memory tasks than the lateral group. These differences were particularly apparent on tasks with an associative component (arbitrary associative learning, [italic]p[/italic] = .01; complex figure recall, [italic]p[/italic] = .03). Group differences persisted once age at seizure onset had been controlled and were not related to seizure frequency. The lateral group displayed intact abilities relative to normative standards. There were no significant differences within the mesial and lateral groups as a function of laterality. Facial recognition did, however, tend to be poorer in the right as opposed to left mesial group ([italic]p[/italic] = .06)., This study demonstrates that children with mesial but not lateral TLE are at risk for memory impairment. This difference was most apparent on measures with an associative component, supporting an associative model of hippocampal function. Results indicate that future memory research should differentiate between mesial and lateral subgroups. From a clinical perspective, results suggest that mesial and lateral cases should be counselled differently in terms of risk to memory function. This study demonstrates that children with TLE are a heterogeneous clinical group in terms of risk to memory function., (Supported by Murdoch Childrens Research Institute Perpetual Foundation.)