The assessment of auditory function in CSWS: lessons from long-term outcome

In Landau-Kleffner syndrome (LKS), the prominent and often first symptom is auditory verbal agnosia, which may affect nonverbal sounds. It was early suggested that the subsequent decline of speech expression might result from defective auditory analysis of the patient's own speech. Indeed, despite normal hearing levels, the children behave as if they were deaf, and very rapidly speech expression deteriorates and leads to the receptive aphasia typical of LKS. The association of auditory agnosia more or less restricted to speech with severe language decay prompted numerous studies aimed at specifying the defect in auditory processing and its pathophysiology. Long-term follow-up studies have addressed the issue of the outcome of verbal auditory processing and the development of verbal working memory capacities following the deprivation of phonologic input during the critical period of language development. Based on a review of neurophysiologic and neuropsychological studies of auditory and phonologic disorders published these last 20 years, we discuss the association of verbal agnosia and speech production decay, and try to explain the phonologic working memory deficit in the late outcome of LKS within the Hickok and Poeppel dual-stream model of speech processing.