Down Syndrome Speech Intelligibility Diagnostic Treatment Study

Overview

The 'Down syndrome speech intelligibility diagnostic treatment study' is a pilot clinical intervention study assessing the efficacy of an integrative speech treatment approach for individuals with Down syndrome (DS). This study will use a single-subject design with 10 male participants with DS, aged 7 to 16 years. The proposed intervention, combines two treatment approaches that are documented to be efficacious with other speech disorders: 1) The Cycles Phonological Remediation Approach, designed for highly unintelligible speech, as guided by the Hodson Assessment of Phonological Patterns (HAPP-3); and 2) Script training, a functional speech motor intervention that promotes phrase-level productions. During the twelve-week intensive intervention period, both approaches will be adapted to prioritize the production of words with low vowels to incorporate increased practice of the low-front and low-back vowels. This modification is based on the investigator's perceptual, acoustic and anatomic research findings. Outcome measures will include perceptual, intelligibility, and acoustic analyses obtained from acoustic recordings. These measures will be used to assess treatment efficacy, and to gain insight into the motoric versus anatomic limitations in speech production commonly present in individuals with DS.

The 'Down syndrome speech intelligibility diagnostic treatment study' is a pilot clinical intervention study assessing the efficacy of an integrative speech treatment approach for individuals with Down syndrome (DS). The clinical management of communication disorders in individuals with DS is a priority for NIH's National Institute on Deafness and Other Communicative Disorder. This priority is well-justified, as DS is a common genetic disorder that causes lifelong intellectual disability where speech intelligibility is typically compromised affecting quality of life. A number of factors affect speech intelligibility, including difficulties in the production of consonants and vowels. The investigator's research (see references) has identified specific challenges in the production and perception of select vowels, specifically the vowels/æ/ and /ɑ/ (as in hat and hot) that are produced with the tongue in the low/vertical position, with /æ/ in a front horizontal position and /ɑ/ in a back horizontal position. Such findings are indicative of difficulties and/or limitations in regulating tongue height and advancement/retraction likely due to motoric factors and/or craniofacial differences. The DS phenotype commonly includes an underdeveloped midface with maxillary hypoplasia, small hard palate, and relative macroglossia which can restrict tongue movements. Furthermore, the investigator's findings revealed that males are less intelligible than females. Based on Vocal Tract Development Laboratory's (VTLab) research findings on anatomic, acoustic and perceptual studies from speakers with DS (see references), the proposed intervention combines and adapts two well-established speech treatment approaches on articulatory accuracy and motor learning while adapting each approach to prioritize the production of the low-front /æ/ and low-back /ɑ/ vowels over other vowels to provide increased practice in regulating tongue position. The articulatory accuracy treatment uses the Cycles phonological approach designed for highly unintelligible speech, as guided by the Hodson Assessment of Phonological Patterns (HAPP-3); and the motor learning treatment uses Script training using functional common conversational topics with short phrase level productions. Given the wide range of individual differences in individuals with DS, a single-subject design is employed with 10 male participants with DS, aged 7 to 16 years. Each participant will receive a 12-week period of individualized intensive speech-intervention (2-3 hours per week). Data collection will include intake information such as hearing screening, mean length of utterance, receptive vocabulary and oral motor exam. Baseline and outcome measure assessments will follow, comprising perceptual, intelligibility and acoustic analyses derived from acoustic recordings of speech productions (recording and analysis methods similar to procedures described in listed references). Acoustic recordings of the Hodson Assessment of Phonological Patterns-Third Edition (HAPP-3) stimuli will be used for outcome measures 1, 2 and 5; VTLab Speech Production stimuli for outcome measures 3 and 4; and script phrases for outcome measure 6. Finally, the Intelligibility in Context Scale, as rated by parents, for outcome measure 7. An overview of methods for outcome measures data collection follows: I. The Hodson Assessment of Phonological Patterns-Third Edition (HAPP-3) is a valid, reliable, standardized test designed for children with highly unintelligible speech. It aims to: 1) determine phonological disorder severity (first outcome measure); 2) identify phonological patterns for treatment using the Cycles Phonological Approach (described below, second outcome measure); and 3) track progress through pre- and post- intervention scores (1- and 6-month follow-ups are incorporated in this study design). The test uses 50 words (32 monosyllabic + 18 multisyllabic) for a comprehensive phonological evaluation to determine the severity of the phonological disorder that impacts communication. In addition, the test categorizes the phonological deviations/errors into two main patterns (omissions and substitutions): 'Word/Syllable Structure Omissions', and 'Consonant Category Deficiencies'. The test offers 129 instances of omissions of: syllables, consonant clusters, or single consonants; and 144 instances of deficiencies/substitutions that include: consonant substitutions and/or assimilations or consonant harmony. Instances of phonological deviations/errors are added, and higher incidence of error pattern/types are targeted first during intervention. The combined total sum of the two phonological deviation patterns (Word/Syllable Omissions Sum plus Consonant Category Deficiencies Sum) yields the Total Occurrences of Major Phonological Deviations (TOMPD) score that is used to determine the severity rating of the phonological disorder in children. Although the total number of Omissions and Deficiencies add up to 273, the TOMPD uses a score range 0-to-150 to rate the severity of the phonological deviation using the following ratings: 0: No errors; 1-50: Mild; 51-100: Moderate; 101-150: Severe; \>150: Profound. A decrease in TOMPD score after intervention suggests improvement in speech production/fewer phonological deviations and improved communication/speech intelligibility. A decrease in the sum of the 'Word/Syllable Structure Omissions' and/or the 'Consonant Category Deficiencies' implies fewer errors in that specific pattern of phonological deviation. Furthermore, if the specific type of deviation (omission/substitution) is an intervention target, then the decreased score implicates responsiveness to the Cycles intervention provided (described next). Basically, smaller score/sum indicate fewer errors and higher score/sums reflects more errors/phonological deviations. The Cycles Phonological Approach is a treatment guidance with focus on assessing and treating speech sound disorders in targeted patterns based on developmental phonology. 'Cycles' refers to periods where all phonological error patterns are facilitated in succession per target phoneme with gradual increase in complexity per cycle. The approach uses a developmental hierarchy of phonological treatment is syllable units, consonant vowel (CV), VC, CVC or VCV, /s/ clusters and alveolars in words, then phrases. The Cycles approach accounts for a number of deficits (such as motoric, phonologic and hearing loss) that are commonly present in individuals with DS. Cycles approach uses production drills and sound practice (i.e. repeating sounds, syllables, \& words as practice), in facilitated context to yield accurate productions, where repeat practice may assist with motor control planning (e.g., apraxia, dysarthria). Cycles also uses headphones with amplification, for auditory bombardment of the target sounds, which may assist with hearing loss given likely fluctuating history of otitis media in DS. Adapting the Cycles approach for the proposed treatment plan by prioritizing the low vowels to establish distinct contrasts between /ɑ/ and /æ/, while following the targeted cycles of phonological intervention, adheres to the Cycles program design. II. The Vocal Tract Development Lab (VTLab) Stimuli were originally designed for lifespan studies of vowel acoustics and included the following considerations: 1) Familiarity to young children; 2) preference to words containing sounds that typically emerge earlier in development, such as bilabial and alveolar consonants versus velars (e.g., 'bat' was chosen over 'cat'); 3) Selection of words with high phonological neighborhood density to maximize vowel acoustic space, an acoustic measure related to speech intelligibility. VTLab stimuli consist of 25 monosyllabic monosyllabic words. Word stimuli include five words for each of the four extreme vowels (/i, u, æ, ɑ/) and the central vowel (/ə/) as in 'eat', 'hoot', 'hat', 'hot', and 'hug' with two of the five words, denoted with the subscript 2, produced twice. The stimuli for the five vowels included the following words: /i/: bead2, eat2, bee, sheep, feet; /u/: boot2, hoot2, boo, shoe, zoo; /æ/: bat2, hat2, bath, cat, sad; /ɑ/: pot2, hot2, top, hop, dot; and /ə/: bug2, hug2, bus, duck, tub. Acoustic recordings of all word stimuli will be used for perceptual and intelligibility assessments. Additionally, the vowel portions of recorded words containing the low vowels /æ/ and /ɑ/ will be subjected to acoustic analysis using TF32 software analyzed for outcome measures 3 and 4. Focus on vowel assessment was in part because vowels contribute to speech intelligibility. Yet, most formalized speech assessments, including HAPP-3 that we employed, focus predominantly on consonants. Outcome measure 3 was employed for perceptual assessment of vowels. Additionally, vowel acoustic analysis, specifically the first and second formant frequencies (F1 and F2), i.e. the resonant frequencies of the vocal tract, will be used to infer information and gain insight on displacement of articulators, such as tongue advancement-retraction and/or tongue height based on mouth/jaw opening when producing the vowels /æ/ and /ɑ/ (i.e. dimensionality of tongue movement/position). F1 corresponds to tongue height and jaw opening (lower F1 indicates higher tongue position and less jaw opening), while F2 relates to tongue advancement (higher F2 corresponds to a more fronted tongue position). The F2-F1 difference correlates with tongue advancement. Given the complex nature of the speech disorder in DS and the presence of craniofacial anomalies, acoustic modification post intervention - which may not be perceptually salient - could provide insight on the effectiveness of vowel-focused intervention on speech intelligibility despite craniofacial anomalies. III. The Script program is a motor training treatment guidance. Script templates are common conversational topics with short phrase level productions that are practiced in unison, with prompting (fading unison), and then independently. The script training with visual support aims to improve the motor production/planning of vowels /ɑ/ and /æ/ in sentences while supporting the learning style of individuals with cognitive disabilities. Additionally, productions with variable communication partners may aid generalization. Script topics choices will include a conversation starter, ordering at a restaurant, movie or video game (favorite parts) description, and/or how to invite a friend over. One script will be used per treatment session to practice the production of /ɑ/ and /æ/ vowel contrasts in phrases. Once the vowels are mastered in the initial script, an additional one or two scripts will be chosen by participants and used as home practice. Blocked practice of script phrases motivates their use outside of treatment sessions. To ensure effective intervention, age appropriate activities and materials will be used during treatment while accounting for individual needs and interests. Production of script phrases will be used for outcome measure 6. IV. Intelligibility in Context Scale is a reliable and valid parent-report tool used for outcome measure 7. It consists of seven items, for parents to rate on a 5-point scale, on how well their child's speech is understood in various social contexts. The outcome measures listed in the Results will be used to: a) Assess the efficacy of intervention in improving accuracy of speech production and speech intelligibility; and b) Gain insight on motoric limitations versus anatomic constraints on speech accuracy. Findings from this clinical intervention study are expected to pave the path towards identifying optimal management of speech clarity in speakers with DS and provide the preliminary data needed to bridge the gap towards a clinical trial on functional anatomy as an early intervention strategy to promote speech clarity in young children with DS.