How to cut the pie is no piece of cake: Toward a process-oriented approach to assessment and diagnosis of speech sound disorders.

BACKGROUND: 'Speech sound disorder' is an umbrella term that encompasses dysarthria, articulation disorders, childhood apraxia of speech and phonological disorders. However, differential diagnosis between these disorders is a persistent challenge in speech pathology, as many diagnostic procedures use symptom clusters instead of identifying an origin of breakdown in the speech and language system. AIMS: This article reviews typical and disordered speech through the lens of two well-developed models of production-one focused on phonological encoding and one focused on speech motor planning. We illustrate potential breakdown locations within these models that may relate to childhood apraxia of speech and phonological disorders. MAIN CONTRIBUTION: This paper presents an overview of an approach to conceptualisation of speech sound disorders that is grounded in current models of speech production and emphasises consideration of underlying processes. The paper also sketches a research agenda for the development of valid, reliable and clinically feasible assessment protocols for children with speech sound disorders. CONCLUSION: The process-oriented approach outlined here is in the early stages of development but holds promise for developing a more detailed and comprehensive understanding of, and assessment protocols for speech sound disorders that go beyond broad diagnostic labels based on error analysis. Directions for future research are discussed. WHAT THIS PAPER ADDS: What is already known on the subject Speech sound disorders (SSD) are heterogeneous, and there is agreement that some children have a phonological impairment (phonological disorders, PD) whereas others have an impairment of speech motor planning (childhood apraxia of speech, CAS). There is also recognition that speech production involves multiple processes, and several approaches to the assessment and diagnosis of SSD have been proposed. What this paper adds to existing knowledge This paper provides a more detailed conceptualisation of potential impairments in children with SSD that is grounded in current models of speech production and encourages greater consideration of underlying processes. The paper illustrates this approach and provides guidance for further development. One consequence of this perspective is the notion that broad diagnostic category labels (PD, CAS) may each comprise different subtypes or profiles depending on the processes that are affected. What are the potential or actual clinical implications of this work? Although the approach is in the early stages of development and no comprehensive validated set of tasks and measures is available to assess all processes, clinicians may find the conceptualisation of different underlying processes and the notion of potential subtypes within PD and CAS informative when evaluating SSD. In addition, this perspective discourages either/or thinking (PD or CAS) and instead encourages consideration of the possibility that children may have different combinations of impairments at different processing stages.