Abstracts

The intracarotid amobarbital procedure (IAP) has historically been the gold standard for lateralization in language function. Localization of language cortex has previously been performed through cortical stimulation studies and more recently with functional neuroimaging procedures. Good concordance has been reported in lateralizing language. Systematic comparison of techniques that localize language cortex has been limited. The current study reports our preliminary experience comparing fMRI, magnetoencephalography (MEG) and electrocortical stimulation in patients with language dominance established by IAP. The subjects were 13 patients who were candidates for epilepsy surgery (8 M; 5 F). Ages ranged from 7 to 47 yrs. Eleven patients were right-handed, one was left-handed and one was ambidextrous. Eleven of the patients were left-hemisphere dominant by IAP and two were undetermined. Eight patients underwent fMRI with language testing in multiple modalities and also underwent cortical stimulation mapping using subdural electrode array. Four patients underwent mapping with MEG and cortical stimulation. One patient underwent all procedures. Anatomical localization of language cortex was compared between techniques. Eleven patients demonstrated left hemisphere language lateralization on all procedures. One patient yielded discordant data, with the IAP undetermined, fMRI suggesting right dominance, and stimulation identifying expressive language in the left hemisphere. For the remaining patient, language lateralization was undetermined on IAP, but clearly left on fMRI and cortical stimulation. When the localization of language areas was compared across techniques, fMRI activation suggested larger areas of language cortex compared to results of stimulation mapping for a majority of cases. In contrast, MEG appeared to under-represent language cortex compared to stimulation mapping in two of four patients. Language areas appeared more consistent in the remaining two cases. The patient who underwent all procedures demonstrated consistent localization of language areas. Reliance on functional neuroimaging alone to guide surgical resection remains uncertain. Continued language mapping using electrocortical stimulation is essential to the application and interpretation of function neuroimaging.