Abstracts

Rationale: A previous study suggested that patients misclassified on magnetic source imaging (MSI) as right hemisphere dominant are more likely than those corcordant with Wada-confirmed left language dominance to evidence compromise of language functioning on baseline neuropsychological testing and experience an earlier age of seizure onset. The aim of this study was to examine language functioning or other factors that might account for bilateral activation on MSI in those who display uneviquocal left hemispheric dominance on the Wada. Methods: The sample included nineteen temporal lobe epilepsy and/or tumor patients ages 18-60 years who underwent both MSI for language lateralization and demonstrated unequivocal left hemisphere dominance on the intracarotid amobarbital procedure (IAP). Those who demonstrated MSI left dominance (MSI-L, n=13) were compared to those who demonstated MSI bilateral language (MSI-B, n=6) on tests of language (Boston Naming Test, Wechsler VC index), verbal memory (delayed recall on a list learning task), age of seizure onset, IAP hemispheric memory capacity, side of seizure onset, and presence of a temporal lobe structural lesion. Results were analyzed using the Fisher Exact Test and t-test. Results: Although short of statistical significance, there was a trend toward younger age at seizure onset among MSI-B (12.2 years) than MSI-L (23.7 years). Patients in the MSI-B group (67%) were somewhat more likely than MSI-L (23%) to display below normal language on BNT or Wechsler VC (Fisher exact Test p= .12). MSI-B and MSI-L did not differ significantly on presence or absence of a temporal lobe structural abnormality, IAP hemispheric memory capacity, or side of seizure onset, although a slightly larger proportion of MSI-B (100%) than MSI-L (69%) had a left temporal seizure origin. Conclusions: Although differences were not clinically significant, there was a trend toward greater likelihood of language compromise and earlier age of seizure onset among Wada-confirmed left dominant patients who displayed bilateral language activation on MSI. These data are consistent with previous findings suggesting that greater compromise of the left hemisphere may be associated with the appearance of increased right hemisphere activation on MSI.