Abstracts

The effect of age at seizure onset on language lateralization is well known: individuals with early seizure onset are more likely to demonstrate atypical (right or bilateral) language representation than those with later injury. It is unclear, however, whether pathology related to early seizures plays a role in determining language dominance. In the only other report on effects of pathology on language laterality, Duchowny [italic]et al[/italic]. (Ann Neurol., 1996), observed atypical language lateralization in the context of [italic]acquired[/italic], but not [italic]developmental[/italic] pathologies of the left hemisphere. Unfortunately, the small sample (n = 34) and exclusive use of extraoperative stimulation mapping (ESM) for lateralization (insensitive to bilateral representation) precludes definitive conclusions about pathology-laterality relationships. We retrospectively analyzed findings from 108 consecutive cases of children who underwent intracarotid amobarbital procedure (IAP), fMRI, and/or ESM for language lateralization/localization. Subjects were investigated at the Hospital for Sick Children (Toronto, ON) to determine candidacy for surgical treatment of refractory epilepsy. Ninety Ss had conclusive language assessments and categorically developmental (n=40) or acquired (n=50) pathologies [ndash] only findings from conclusive investigations were analyzed. Where Ss underwent multiple language assessments, findings from only one mode of investigation were analyzed; IAP was preferred over fMRI, which was preferred over ESM. Atypical language lateralization was documented in 13 Ss with developmental pathologies (32.5%), and in 12 Ss with acquired pathologies (24.0%); the difference was not statistically significant, [chi]²=.80, 1 df, [italic]p[/italic][gt].05.
Sixty two Ss had left hemisphere epilepsies (28 developmental, 34 acquired pathologies). Within this subset, atypical language lateralization was documented in 12 Ss with developmental (42.9%) and 12 Ss with acquired (35.3%) pathologies; the difference was not statistically significant, [chi]²=.37, 1 df, [italic]p[/italic][gt].05.
Thirty-six Ss had left hemisphere epilepsies with onset on or before age 5 yrs (22 developmental, 14 acquired pathologies). Within this subset, atypical language lateralization was documented in 12 Ss with developmental (54.5%) and 7 Ss with acquired (50.0%) pathologies; the difference was not statistically significant, [chi]²=.39, 1 df, [italic]p[/italic][gt].05. Atypical language representation is equally likely to occur in the context of developmental and acquired pathologies. Knowledge of developmental versus early acquired pathology is not useful in predicting language lateralization. (Supported through a [italic]Studentship[/italic] to DSK from the [italic]Ontario Student Opportunity Trust Fund [ndash] Hospital for Sick Children Foundation Student Scholarship Program[/italic], and through a [italic]Doctoral Research Award[/italic] to DSK from the [italic]Canadian Institutes of Health Research (CIHR) [/italic]in partnership with[italic] Epilepsy Canada[/italic].)