Comparative localization of auditory comprehension using functional magnetic resonance imaging and cortical stimulation

Abstract

The authors have previously described a functional magnetic resonance (fMR) imaging procedure for the localization of auditory comprehension in which focal activation of posterior temporal and inferior frontal regions of the left hemisphere was reliably demonstrated. Because this past study was conducted in neurologically normal volunteers, it was not possible to determine whether the activated regions were critical to the performance of language tasks; that is, whether the fMR imaging activations provided a rate measure of language processing. A direct comparison of fMR imaging language activation with cortical stimulation must be completed before the tool can be used with confidence in presurgical planning. Here the authors report a series of 33 consecutive patients who underwent dominant hemisphere resection in which fMR image mapping of auditory comprehension was performed at the Yale neurosurgical program. In 23 of the 33 patients reliable fMR imaging activation was shown. In 16 of these 23 patients language mapping was performed using either intra- or extraoperative cortical stimulation. Cortical stimulation failed to localize language areas in two of the 16 patients. Electrical stimulation that was performed in close proximity to the fMR image activations interfered with auditory comprehension, object naming, or speech production in 12 of the remaining 14 patients. Five of the 10 cases in which evocation reliable fMR imaging activation failed were attributable to technical problems and/or patient head movement. Cortical stimulation results and fMR imaging findings were consistent in all but two patients. However, the spatial extent of the activation produced by fMR imaging and the spatial extent of stimulation-induced language disruption that was caused by direct cortical stimulation did not always correspond. Problems in defining the extent of activation by both methods are discussed.