Abstracts

The configuration of language cortex in the left dominant hemisphere based on electrocortical stimulation has been described in detail in the literature. However, language representation in the right hemisphere remains unclear in patients classified with bilateral language based on the intracarotid amobarbital procedure (IAP). Herein, we report 5 patients with bilateral language who underwent placement of a right subdural electrode array (SEA) and subsequent electrocortical stimulation for language. The right hemisphere language maps of 5 patients with bilateral language, who underwent SEA placement at Minnesota Epilepsy Group between January 1996 and February 2004, were reviewed. In each case, data were critically compared to the colored photograph of the brain and SEA implant taken intraoperatively for anatomical verification. Expressive and receptive language areas were defined based on language errors produced by electrical brain stimulation during the presentation of a formal language protocol, which included assessment of automatic speech, naming, reading, repetition and auditory comprehension. Three of the 5 patients studied demonstrated the presence of language cortex in the right frontal and/or temporal lobe analogous to the localization of classical language areas in the left hemisphere. In each of these cases, data from the IAP suggests the left hemisphere remains primary for language processing. One patient had a widespread distribution of single site language errors over the right lateral hemisphere. The language map of the remaining patient was completely silent. Our results identify the presence of language cortex in the right hemisphere in 4/5 patients classified with bilateral language in IAP. These areas are presumed to be accessory language zones to the primary language processing areas of the left hemisphere. Further exploratory studies are needed to clarify these specific findings. The clinical significance of these language areas remains to be determined.