Estimates of the prevalence of motor speech disorders in children with idiopathic speech delay

Abstract

The goal of this research was to obtain initial estimates of the prevalence of each of four types of motor speech disorders in children with idiopathic Speech Delay (SD) and to use findings to estimate the population-based prevalence of each disorder. Analyses were completed on audio-recorded conversational speech samples from 415 children recruited for research in idiopathic SD in six USA cities during the past three decades. The speech and motor speech status of each participant was cross-classified using standardized measures in the finalized version of the Speech Disorders Classification System described in the Supplement. Population-based prevalence estimates for the four motor speech disorders were calculated from epidemiological studies of SD conducted in Australia, England, and the USA. A total of 82.2% of the 415 participants with SD met criteria for No Motor Speech Disorder at assessment, 12% met criteria for Speech Motor Delay, 3.4% met criteria for Childhood Dysarthria, 2.4% met criteria for Childhood Apraxia of Speech, and 0% met criteria for concurrent Childhood Dysarthria and Childhood Apraxia of Speech. The estimated population-based prevalence of each of the first three motor speech disorders at 4 to 8 years of age were Speech Motor Delay: 4 children per 1,000; Childhood Dysarthria: 1 child per 1,000; and Childhood Apraxia of Speech: 1 child per 1,000. The latter finding cross-validates a prior prevalence estimate for Childhood Apraxia of Speech of 1–2 children per 1,000. Findings are interpreted to indicate a substantial prevalence of motor speech disorders in children with idiopathic SD.

A frequent acoustic sign of speech motor delay (SMD)

“…As proposed in the first three articles in the present research series, the precision and stability deficits in SMD are posited to result from processing constraints at the execution stage of speech production (Shriberg, Kwiatkowski, & Mabie, 2019, Figure 1). The present findings, however, are more consistent with the conclusion in Shriberg, Campbell, et al (2019) that there likely are common neurodevelopmental pathways underlying the four SDCS classifications of motor speech disorder phenotypes -SMD, CD, CAS, and CD & CAS.…”

“…Comparative research is needed to determine if the increased durations of /ɪ/ and /ɛ/ in children with SMD are similar to the increased durations of these phonemes in the speech of children with CAS, perhaps reflecting developmental constraints in feedforward processes in speech motor development (Terband, Maassen, Guenther, & Brumberg, 2014). As described in Shriberg, Kwiatkowski, and Mabie (2019) and Shriberg, Campbell, et al (2019), a speculation is that false positive diagnoses of CAS could be due, in part, to such overlaps in the phenotypes of childhood apraxia of speech and SMD. Although they did not meet the arbitrary criterion for a frequent sign of SMD (i.e., >50% occurrence in participants in all three research groups), other findings in Figure 2 support the potential deficits in temporal processes implied in the significant findings for PSI Sign No.…”

“…The lower three rows include information on participants in three databases of speakers with typically-developing speech used to standardize measures. USA group Participants in the USA group were identified from a database of 415 children recruited for research in SD in six USA cities (Shriberg, Kwiatkowski, & Mabie, 2019). All participants met criteria for idiopathic SD using Speech Disorders Classification System (SDCS) software (Shriberg, 1993, Appendix).…”

“…Four research specialists completed narrow phonetic transcription, prosody-voice coding, and acoustic analyses of the audio-recorded conversational speech samples and the two word-imitation tasks in the USA and CND groups using procedures developed for research in speech sound disorders (Shriberg et al, 2010b). For the three types of data reduction, randomly selected, 20% intrajudge and interjudge point-to-point percentages of agreements for 26 perceptual and acoustic variables ranged from 74.9% to 97.3% for the USA samples (Shriberg, Kwiatkowski, & Mabie, 2019) and 69.7% to 97.5% for the CND samples (Shriberg, Strand, et al, 2019).…”

“…Participants in the USA and CND groups met perceptual-based criteria for Normal Speech Acquisition, SD, or Persistent SD (if older than 9 years of age), using a prior version of the Speech Disorders Classification System (Shriberg, Austin, Lewis, McSweeny, & Wilson, 1997, Appendix A). Participants in both groups also met perceptual and acoustic criteria for one of five concurrent, mutually exclusive motor speech classifications described in a previous paper in this issue (Shriberg, Kwiatkowski, & Mabie, 2019) Figure 1 is a manual copy of the PSI assessment form, the measure used to identify speakers with early or persistent SMD. The PSI includes 13 perceptual and 19 acoustic signs of imprecise and/or unstable speech, prosody and voice in continuous speech.…”