Subtypes of speech sound disorders (SSDs) with a sensorimotor origin are known as motor speech disorders (MSDs). The symptoms can be diverse, and the causes of the disorders in children are in many cases unknown. Examples of MSD are childhood apraxia of speech and dysarthria. MSD is often seen in neurodevelopmental disorders such as cerebral palsy, developmental coordination disorder (DCD) or autism spectrum disorders (ASD), or it is seen with no obvious diagnosis but usually with comorbid problems. Within all existing comorbidity dysfunctions, the motor and sensory systems are of interest for identifying possible underlying mechanisms of MSD. Namely, soft neurological signs such as hypotonia, decreased speed and low accuracy of motor skills and delayed motor development are given consideration by many researchers for better understanding of underlying motor mechanisms of MSD. Results from comorbidity studies highlight the relationship of MSD with complex sensorimotor tasks and sequential motor tasks. In this chapter, our aim is to frame findings from studies about comorbidity of sensory and motor dysfunctions in MSD in order to theorise affected mechanisms and propose an underlying global motor deficit. We will conclude with implications for therapy models.
Part of the book: Advances in Speech-language Pathology