Abstracts

Functional MRI (fMRI) at 1.5T in normal children and children with neurological disorders yields reliable patterns of lateralised activation in inferior frontal and lateral temporal areas during language tasks. We report the findings of high-field fMRI at 3T in children evaluated for epilepsy surgery. Twenty children (age 7-14 years, median 12) with uncontrolled partial epilepsy and concerns about cerebral language dominance underwent language fMRI as part of a presurgical evaluation. Seizures were temporal in 13, frontal in four, central in two and parietal in one (left 14, right 5, bilateral 1). Fifteen had cerebral lesions including cortical dysplasia in three, tumor in six, vascular malformation in two and hippocampal sclerosis in three. Two patients were left-handed. Ten underwent surgery, four with prior language mapping.
Whole-brain, multi-slice EPI was performed at 3T in the axial plane. A covert verb-generation task was employed using visually-presented nouns in four task blocks alternating with five rest blocks of 36 seconds (total scan time 5.5 min). Data was analyzed with SPM2 and iBrain[reg]. Language activation maps were generated and overlaid on raw EPI images for independent blinded visual rating by two neurologists. A laterality index (LI = L-R/L+R) was calculated from the total voxels activated in the typical language areas, considering greater than +/- 0.2 as lateralized Cortical activation in typical frontal areas was seen in all patients. On visual rating, language activation was left lateralized in 18 (90%), right lateralized in one and bilateral in one (100% concordance on independent blinded review). LIs were in the bilateral range in the two with atypical lateralization and the two with left lateralisation, being in the left lateralised range for the remainder. fMRI lateralization was corroborated by cortical stimulation in three. No operated patient had language compromise following surgery. Surgery was not performed in three patients with co-localization of seizures, lesion and language activation. High-field fMRI provides clinically-useful information on lateralization and localization of critical language cortex in children with intractable focal epilepsy, guiding surgical decision-making and operative approaches. In this selected series which contained an over-representation of left foci, lesions and handedness, language was left lateralised in nearly all patients.