Interhemispheric transfer of language in patients with left frontal cerebral arteriovenous malformation

Cerebral arteriovenous malformations (AVMs) are frequently evaluated before therapeutic embolization by superselective injection of anesthetics into i ndividual arterial branches so as to determine whether permanent occlusion would affect eloquent function. In Experiment 1, we used this adaptation of the Wada procedure to study three right-handed adult patients with left fr ontal cerebral AVMs by injecting vessels in Wernicke's and Broca's areas, r espectively, and assessing language functions. The results showed that supe rselective testing in the inferior division of the left MCA in all three pa tients produced a dense Wernicke's aphasia. Injections into the left fronta l regions, however, resulted in right paresis in all patients, but no langu age deficits including no loss of fluency. In Experiment 2, Patient 2 under went fMRI activation for spontaneous word-list generation using multi-slice echo planar BOLD techniques at 1.5 Tesla. A voxel-by-voxel comparison of r est vs activation for each task was performed with a Z-score threshold of 2 .5 SD for activated voxels. There was activation in the right hemisphere in the insula, frontal operculum pars opercularis, and inferior frontal gyrus , an area homologous to Broca's area in the left hemisphere. There was also activation in the left hemisphere in the Rolandic region, but language fun ction was unaffected during Wada testing in this area. These data suggested that features of expressive language were no longer controlled by the left frontal lobe where the AVM was located, and provided new evidence for inte rhemispheric re-organization under conditions of chronic neurovascular dise ase. (C) 2000 Elsevier Science Ltd. All rights reserved.