Estimates of the prevalence of speech and motor speech disorders in adolescents with Down syndrome

Abstract

Although there is substantial rationale for a motor component in the speech of persons with Down syndrome (DS), there presently are no published estimates of the prevalence of subtypes of motor speech disorders in DS. The goal of this research is to provide initial estimates of the prevalence of types of speech disorders and motor speech disorders in adolescents with DS. Conversational speech samples from a convenience sample of 45 adolescents with DS, ages 10 to 20 years old, were analysed using perceptual and acoustic methods and measures in the Speech Disorders Classification System (SDCS). The SDCS cross-classified participants into five mutually exclusive speech classifications and five mutually exclusive motor speech classifications. For participants meeting criteria for Childhood Dysarthria or for Childhood Dysarthria concurrent with Childhood Apraxia of Speech, the SDCS provided information on participants’ percentile status on five subtypes of dysarthria. A total of 97.8% of participants met SDCS criteria for Speech Disorders and 97.8% met criteria for Motor Speech Disorders, including Childhood Dysarthria (37.8%), Speech Motor Delay (26.7%), Childhood Dysarthria and Childhood Apraxia of Speech (22.2%), and Childhood Apraxia of Speech (11.1%). Ataxia was the most prevalent dysarthria subtype. Nearly all participants with DS in the present sample had some type of speech and motor speech disorder, with implications for theory, assessment, prediction, and treatment. Specific to treatment, the present findings are interpreted as support for motor speech disorders as a primary explanatory construct to guide the selection and sequencing of treatment targets for persons with DS.

Speech and motor speech disorders and intelligibility in adolescents with Down syndrome

“…The well-documented intelligibility deficits in persons with DS and the substantial prevalence of motor speech disorders in adolescents with DS recently reported in Wilson, Abbeduto, Camarata, and Shriberg (2019) motivated the questions posed in the present report. Findings in Wilson et al (2019) indicated that nearly all (97.8%) of the 45 classifiable adolescents with DS in the sample met diagnostic classification criteria for one of the four types of motor speech disorders described previously. In order of prevalence within the sample, 37.8% of the participants met criteria for CD, 26.7% met criteria for SMD, 22.2% met criteria for CD & CAS, and 11.1% met criteria for CAS.…”

“…Figure 1 is a display of the II scores and OII classifications for the original sample of all 50 children with DS, including the 5 participants whose motor speech status could not be classified due to insufficient data to complete the measure used to classify a speaker as having CAS (Wilson et al, 2019). Two of the five participants excluded from further analyses in the present paper met OII criteria for High intelligibility and the other three met criteria for Low intelligibility.…”

“…A total of 9 of the 20 participants had High intelligibility and 11 had Low intelligibility. Figure 2b includes the averaged percentile scores for the subtype indices, using the methods described in Wilson et al (2019) and in the Supplement. Scores are arranged from lowest to highest values in each panel, with lower scores/percentiles indicating greater support for the dysarthria subtype.…”

“…A previous report by Wilson et al (2019) describes the procedures used to recruit and assess an original sample of 50 American-English speaking adolescents with DS, the perceptual and acoustic procedures used by four transcribers and acoustic analysts to reduce the speech, prosody, and voice data, and reliability estimates within and among the transcribers and acoustic analysts. The Supplement for each of the six papers in the present issue of Clinical Linguistics & Phonetics [Supplementary Data] includes information on the methods and measures used to classify participants’ speech and motor speech status.…”

Estimates of the Prevalence of Speech and Motor Speech Disorders in Youth With 22q11.2 Deletion Syndrome

“…Conversational speech samples were available from three comparison groups totaling 104 participants studied in associated research in speech sound disorders. The three groups included 45 participants, 8–20 years old, with DS (Wilson, Abbeduto, Camarata, & Shriberg, 2018); 28 participants, 10–21 years old, with fragile X syndrome (FXS; Abbeduto et al, 2003); and 31 participants, 4–16 years old, with galactosemia (GAL; Shriberg, Potter, & Strand, 2011). As described later in Table 1, participants in these three groups were in the same approximate age range as the present participants with 22q, had a high prevalence of MSDs, and had medical issues and developmental delays, and participants with DS were at a similar greater risk for conductive hearing loss.…”