Abstracts

Rationale: Functional lateralization of medial temporal structures for memory has been shown to frequently correspond to language lateralization. However, the impact of structural lesions and epilepsy on this relationship has not been studied. The goal of our study was to explore the relationship between language and memory lateralization in a large cohort of epilepsy patients with or without MRI-identifiable lesions undergoing intracarotid amobarbital procedure (IAP). Methods: 386 consecutive patients with IAP, epilepsy workup and MRI results were reviewed. Language and memory lateralization as determined by laterality index were calculated and correlated to each other separately for groups with different types and localizations of lesions. Results: 138 patients had hippocampal sclerosis, 51 neoplasms, 41 cortical dysplasia, 66 had rare structural lesions (13 subgroups) and 90 patients had a normal MRI. Epilepsy was left in 206 (53.4%), right in 145 (37.6%), bilateral in 24 (6.2%) and unspecified in 11 (2.8%) patients. Regardless of side of epilepsy and lesion characteristics, language lateralization and memory lateralization were positively correlated (r=0.344, p<0.01). The degree of this correlation, however, differed depending on the presence and type of lesion (chi-square = 7.98 (2df), p<0.05). Post-hoc tests revealed that laterality indices correlated significantly higher (z-value = 2.82; p<0.05) in patients with cortical dysplasia (n=41; r=0.61, p<0.01) compared to the non-lesional group (n=90; r=0.16, p>0.05.) with patients with hippocampal sclerosis falling between these two groups. Both, memory (t(267)=9.8; p<0.01) and language (t(261)= 4.68; p<0.01) laterality index were significantly higher, that is more left lateralized, in right compared to left sided lesions. Conclusions: Although our results are limited due to retrospective analysis these findings support the notion that language and memory lateralization is influenced and their correlation is more pronounced in patients with structural lesions as compared to patients with non-lesional MRI.