Abstracts

Rationale: Atypical language localization frequently occurs in pediatric patients with temporal lobe epilepsy (TLE). Previous studies have not analyzed potential cognitive differences related to type of underlying structural pathology nor have they explored organization of receptive language networks. The aim of our study was to evaluate differences in language organization between children with intractable epilepsy caused by temporal lobe focal cortical dysplasia (FCD) and those with dual pathology (i.e., temporal lobe FCD plus hippocampal sclerosis, HS).Methods: We analyzed clinical, neurological, neuropsychological and histopathological data of 46 pediatric patients with structural lesions in temporal lobes, who underwent excisional epilepsy surgery at Miami Children's Hospital. Seventeen patients had temporal lobe FCD and 29 subjects had dual pathology (FCD+HS). All children presurgically underwent comprehensive neuropsychological testing; functional magnetic resonance using receptive language paradigms was available in 29 and using expressive paradigms in 26 subjects.Results: The two histopathological groups differed significantly in hand dominance (24% of patients with FCD+HS were left-handed, contrasted with none of the FCD patients, p=0.036). Left-handers had significantly earlier onset of epilepsy (p=0.046) and lower results in verbal abstract reasoning (p=0.026).We then excluded 7 left-handed patients and all further analyses were done in a group of 39 right-handed subjects. FCD patients had higher scores than FCD+HS subjects only for immediate visual memory for faces; all other neuropsychological domains did not differ between the histopathological groups. Patients with atypical localization of receptive language had significantly more lesions in the left hemisphere (p=0.034), higher incidence of status epilepticus (p=0.024) and (in cognitive profile) lower general intellectual capacity, especially the capacity of verbal abstract conceptualization (p=0.004), lower receptive language abilities (p=0.003) and lower verbal working memory (p=0.012). Other variables showed no differences between patients with typical and atypical receptive language network laterality. We identified only 3 subjects with atypical localization of expressive language center; they tended to differ from patients with typical localization in similar neuropsychological variables as patients with atypical localization of receptive language.Conclusions: We found only minor influence of histopathological type of temporal lobe lesion (FCD vs. FCD+HS) on neuropsychological profiles of pediatric temporal lobe epilepsy patients. Atypical language localization represented a more significant risk factor for cognitive morbidity than additional hippocampal damage. Subjects with atypical representation of receptive language centers had more impaired verbal comprehension and capacity which may reflect larger reorganization of receptive language networks in these patients. Supported by MH CZ DRO, University Hospital Motol, Prague,Czech Republic 00064203 and GAUK 1162/13, Faculty of Arts, Charles University, Prague.