Conduction aphasia is defined as a fluent aphasia with paraphasic errors (especially phonemic/literal) during speech, repetition and naming. In its "pure" form, there is a dissociation between relatively preserved auditory and reading comprehension of language and impaired repetition (in which the phenomenon of conduit d’approche may occur) and naming. Reading comprehension is good or normal, and is better than reading aloud which is impaired by paraphasic errors.
Conduction aphasia was traditionally explained as due to a disconnection between sensory (Wernicke) and motor (Broca) areas for language, involving the arcuate fasciculus in the supramarginal gyrus. Certainly the brain damage (usually infarction) associated with conduction aphasia most commonly involves the left parietal lobe (lower postcentral and supramarginal gyri) and the insula, but it is variable, and the cortical injury may be responsible for the clinical picture.
Conduction aphasia is most often seen during recovery from Wernicke’s aphasia, and clinically there is often evidence of some impairment of comprehension. If isolated, the prognosis for conduction aphasia is good.
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