FMRI lateralization of expressive language in children with cerebral lesions

Summary: Purpose: Lateralization of language function is cru- \ud cial to the planning of surgery in children with frontal or tempo- \ud ral lobe lesions. We examined the utility of functional magnetic \ud resonance imaging (f MRI) as a determinant of lateralization of \ud expressive language in children with cerebral lesions. \ud Methods: f MRI language lateralization was attempted in 35 \ud children (29 with epilepsy) aged 8–18 years with frontal or tem- \ud poral lobe lesions (28 left hemisphere, five right hemisphere, \ud two bilateral). Axial and coronal f MRI scans through the frontal \ud and temporal lobes were acquired at 1.5 Tesla by using a block- \ud design, covert word-generation paradigm. Activation maps were \ud lateralized by blinded visual inspection and quantitative asym- \ud metry indices (hemispheric and inferior frontal regions of inter- \ud est, at p < 0.001 uncorrected and p < 0.05 Bonferroni corrected). \ud Results: Thirty children showed significant activation in the \ud inferior frontal gyrus. Lateralization by visual inspection was \ud left in 21, right in six, and bilateral in three, and concordant \ud with hemispheric and inferior frontal quantitative lateralization \ud in 93% of cases. Developmental tumors and dysplasias involving \ud the inferior left frontal lobe had activation overlying or abutting \ud the lesion in five of six cases. f MRI language lateralization was \ud corroborated in six children by frontal cortex stimulation or in- \ud tracarotid amytal testing and indirectly supported by aphasiology \ud in a further six cases. In two children, f MRI language lateral- \ud ization was bilateral, and corroborative methods of language lat- \ud eralization were left. Neither lesion lateralization, patient hand- \ud edness, nor developmental versus acquired nature of the lesion \ud was associated with language lateralization. Involvement of the \ud left inferior or middle frontal gyri increased the likelihood of \ud atypical language lateralization. \ud Conclusions: f MRI lateralizes language in children with cere- \ud bral lesions, although caution is needed in interpretation of indi- \ud vidual results