MR diffusion tensor imaging documented arcuate fasciculus lesion in a patient with normal repetition performance

Background: The pathophysiology of the syndrome of conduction aphasia has been thought to involve a disconnection between posterior and anterior language areas. The arcuate fasciculus has been one of the principal candidates for an anatomical link between Wernicke's and Broca's area, but direct evidence for its involvement in conduction aphasia has been difficult to obtain. Aims: The purpose of this study was to examine white matter tract integrity, using the novel magnetic resonance imaging technique of diffusion tensor imaging, in a patient with transcortical aphasia. Methods & procedures: A case study of a 55-year-old, right-handed man with aphasia following a left hemisphere stroke is reported. The patient's language performance was assessed with the Boston Diagnostic Aphasia Examination twice: at 10 days and at 2 years after his stroke. An MR diffusion tensor imaging study was obtained approximately 2 years after his stroke using the 1.5 T Phillips Gyroscan NT system. White matter fibre tracts maps were reconstructed using the "FACT" algorithm. Outcomes and results: Ten days after his stroke, the patient had a non-fluent aphasia with marked impairment of both auditory comprehension and spontaneous speech. However, repetition was relatively intact. By 2 years, when the MR diffusion tensor imaging study was performed, repetition was completely normal and the patient had only subtle deficits in areas of naming and auditory comprehension. The MR diffusion tensor imaging study revealed a lesion of the dominant hemisphere arcuate fasciculus. Conclusions: This study documents normal repetition performance in a patient who on subsequent MR diffusion tensor imaging was found to have a lesion involving the dominant hemisphere arcuate fasciculus lesion. This case adds to previously published cases of normal repetition performance despite a documented lesion of the arcuate fasciculus, and thus further challenges the traditional model of conduction aphasia invoking a critical role of this white matter tract. Our case also suggests that MR diffusion tensor imaging may be a potentially useful technique to evaluate regional involvement of specific white matter tract projections in patients with aphasia.