Relatively normal repetition performance despite severe disruption of the left arcuate fasciculus.

The arcuate fasciculus (AF) is believed to be fundamental to the neural circuitry behind many important cognitive processes. Connecting Wernicke's and Broca's area, these fibers are thought to be especially important for repetition. In this case study we present evidence from a patient that set doubt on these assumptions. We present structural imaging, diffusion tensor imaging, and language data on a patient with a large left-sided stroke and severely damaged left AF who showed intact word repetition and relatively intact sentence repetition performance. Specifically, his sentence repetition is more fluent and grammatical, with less hesitation than spontaneous speech, and with rare omissions only during the longest sentences. These results challenge classical theories that maintain the left AF is the dominant language processing pathway or mechanism for repetition.