Background and Purpose—Previous studies have suggested that patients’ potential for post- stroke language recovery is related to lesion size; however, lesion location may also be of importance, particularly when fiber tracts that are critical to the sensorimotor mapping of sounds for articulation (e.g. the arcuate fasciculus [AF]) have been damaged. In this study, we tested the hypothesis that lesion loads of the AF (i.e. volume of AF that is affected by a patient’s lesion) and of two other tracts involved in language processing (the extreme capsule [EmC] and the uncinate fasciculus [UF]) are inversely related to the severity of speech production impairments in stroke patients with aphasia. Methods—Thirty chronic stroke patients with residual impairments in speech production underwent high-resolution anatomical MR imaging and a battery of cognitive and language tests. Impairment was assessed using three functional measures of spontaneous speech (e.g. rate, informativeness, and overall efficiency) as well as naming ability. To quantitatively analyze the relationship between impairment scores and lesion-load along the three fiber tracts, we calculated tract–lesion overlap volumes for each patient using probabilistic maps of the tracts derived from diffusion tensor images of ten age-matched healthy subjects. Results—Regression analyses showed that AF-lesion load, but not EmC- or UF-lesion load or lesion size, significantly predicted rate, informativeness, and overall efficiency of speech, as well as naming ability. Conclusions—A new variable, AF-lesion load, complements established voxel-based lesion- mapping techniques and, in the future, may potentially be used to estimate impairment and recovery potential after stroke and refine inclusion criteria for experimental rehabilitation programs.
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