Abstracts

Rationale: Impaired verbal and non-verbal memory has been correlated with temporal white matter (WM) integrity in adults with temporal lobe epilepsy. There is a paucity of data on the relation of WM with cognitive function in children with epilepsy. The aim of this study was to determine if there was a correlation between diffusion tensor imaging (DTI) measures of WM in children with intractable epilepsy and cognition.Methods: 24 patients with MRI-negative localization related epilepsy (mean age 13.7 years, age range 7.0 17.4 years; 10 males and 14 females), who were being investigated for epilepsy surgery and 17 healthy controls (mean age 14.6 years, age range 8.6 17.2 years; 9 males and 8 females) were recruited into the study. Nine had perirolandic epilepsy; six had frontal, four had fronto-temporal, and four had temporal lobe epilepsy. MRI and DTI were done on a 3T magnet. Fractional anisotropy (FA) and mean diffusivity (MD) maps were co-registered to the JHU MNI template. Subsequently a WM parcellation map was applied to the FA and MD maps using the ROIEditor (Johns Hopkins Medical Institute, Laboratory of Brain Anatomical MRI, http://lbam.med.jhmi.edu/) to define the lobar WM (frontal, parietal, temporal and occipital lobes) of the right and left hemisphere, and genu, body, and splenium of corpus callosum. A comprehensive neuro-cognitive test battery was carried out in all patients and controls to measure intelligence, language, memory, executive function and motor function. Neuro-cognitive test results were compared between patients and controls using Mann-Whitney U test. The relation between DTI measures of WM and neuro-cognitive performance was assessed using Spearman s correlation. A p-value of ?0.01 was considered statistically significant.Results: There were significant differences in the following cognitive functions between patients and controls: verbal and nonverbal IQ, full scale IQ, psychomotor speed, fine motor dexterity, response inhibition, divided attention, verbal memory, receptive language, expressive naming and confrontation naming. There were significant negative correlations between left and right temporal WM MD with verbal IQ, expressive naming, confrontation naming and receptive language (Table 1); left and right parietal WM MD with verbal IQ, expressive naming, and confrontation naming; left frontal WM MD with verbal IQ and confrontation naming; right frontal WM MD with confrontation naming; and left occipital WM MD with confrontation naming. There were significant positive correlations between splenium of corpus callosum FA with mental flexibility and immediate verbal recall; body of corpus callosum with immediate verbal recall; as well as between left parietal WM FA with verbal IQ.Conclusions: We have found impaired intelligence, language, memory and executive function in children with intractable epilepsy correlated with regional WM structure as measured by DTI. These findings assist in our understanding of the structural correlates of cognitive impairment in children with intractable epilepsy.