Magnetoencephalographic localization of a language processing cortical area adjacent to a cerebral arteriovenous malformation

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Abstract
✓ In order to accurately estimate the risk of surgery for dominant perisylvian arteriovenous malformations, the topographical relationship of the lesion to language cortex must be determined. A case is presented in which a magnetoencephalographic (MEG) study was used to map preoperatively and noninvasively an intracortical source of speech-receptive cortex in a 25-year-old right-handed man with a dominant left temporal lobe arteriovenous malformation. The speech-evoked magnetic field was analyzed at 36 positions over the left hemisphere in response to presentations of the consonant-vowel syllables “da” and “ga.” A topographical map of the magnetic component evoked at 110 msec after stimulus onset, which was negative going to the vertex in concurrent electrical recordings, was congruent with a superficial cortical neuronal current source. This source was displaced from that usually observed in normal individuals to tonal or click stimuli, being superior to the probable location of auditory cortex, and supe...