Abstracts

Rationale: Temporal lobe epilepsy patients with early age of seizure onset (AoSO; early = age 6 or less) of the disease are well-known to present an increased risk for language reorganization. It is unknown, however, whether language, when it reorganizes, involves a full shift of all language skills to the contralateral hemisphere, or a partial shift involving only a subset of language skills. In this study, we report rates of atypical language representation in temporal lobe epilepsy (TLE) patients and examine the association and concordance rates for five separate aspects of language functioning.Methods: We tested participants (n=110; 76 left seizure focus; mean age = 38.9, SD = 11.8; 73.7% right handed; 55.4% female) for language dominance in each of Comprehension, Repetition, Speech, Reading, and Naming, through the Intracarotid Amobarbital Procedure (IAP). We compared the rates of typicality (left sided dominance) and atypicality (right or bilateral dominance) between the five language components to determine their level of interdependence through Spearman correlations. In addition, through analyses of variance (ANOVA) and tests of proportions, we compared a laterality index (LI) and rates of atypicality respectively among four patients groups broken down by seizure focus and AoSO: left/early (n=24), left/late (n=52), right early (n=6), and right/late (n=28).Results: The data showed that only 33% of atypical cases were atypical for one of the five language components, while 33% were atypical for at least four of the five. Within the subjects atypical for a given language skill, the intercorrelations among the language components were quite high (laterality index measure). Cases with atypical representation for Repetition showed the highest overall concordance rates with the other four components. The ANOVA’s on the LI for Repetition and Speech found main effects for seizure focus with early onset patients showing higher atypicality. The ANOVA on the Naming LI revealed a main effect for AoSO with the left TLE patients showing higher rates of aytpicality. The greatest disparity among the four patient groups was found for Reading with the left/early group showing significantly higher rates of atypicality. Tests of proportions on a composite measure (mean of all 5 language components) clearly revealed a general effect such that the left/early group had the highest rates of atypicality.Conclusions: Our results suggest that the distinct language components are non-independent in terms of language representation, suggesting that when there is pressure toward atypical representation in the brain, those pressures work equally and not separately on individual language skills. In addition, consistent with prior literature, our results indicate high rates of atypicality in both left TLE and early AoSO patients. The principles that govern language reorganization are unknown and our data are important in suggesting that when atypical representation is present and shifts in representation may have occurred, the separate skills of language tend to behave as one and do not re-organize independently. (Non-funded)