Katherine C. Hustad

Estimating the Intelligibility of Speakers with Dysarthria

Many speakers with dysarthria have reduced intelligibility[,] and improving intelligibility is often a primary intervention objective. Consequently, measurement of intelligibility provides important information that is useful for clinical decision-making. The present study compared two different measures of intelligibility obtained in audio-only and audio-visual modalities for 4 different speakers with dysarthria (2 with mild-moderate dysarthria; 2 with severe dysarthria) secondary to cerebral palsy. A total of 80 college-aged listeners provided word-by-word transcriptions and made percent estimates of intelligibility which served as dependent variables. Group results showed that transcription measures were higher than percent estimates of intelligibility overall. There was also an interaction between speakers and measures of intelligibility, indicating that the difference between transcription scores and percent estimates varied among individual speakers. Results revealed a significant main effect for presentation modality, with the audio-visual modality having slightly higher scores than the audio-only modality; however, presentation modality did not interact with speakers or with measures of intelligibility. Results suggest that standard clinical measurement of intelligibility using orthographic transcription may be more consistent than the use of more subjective percent estimates.

Effects of Speech Stimuli and Dysarthria Severity on Intelligibility Scores and Listener Confidence Ratings for Speakers with Cerebral Palsy

This study examined differences among transcription intelligibility scores and listener confidence ratings for three different types of speech stimuli – single words, unrelated sentences, and sentences forming a narrative – all produced by speakers with dysarthria. Twelve speakers with dysarthria of varying severity secondary to cerebral palsy and 144 listeners participated in this study. Results showed that both intelligibility scores and confidence ratings were differentially affected by both stimuli and severity. For speakers with mild, moderate, and severe dysarthria, intelligibility scores were higher for narratives than for either of the other two types of speech stimuli. For speakers with mild dysarthria, sentences were substantially more intelligible than single words. However, for speakers with moderate, severe, and profound dysarthria, the difference in intelligibility scores for sentences and single words was small or nonsignificant. Confidence ratings did not follow the same pattern as intelligibility data, suggesting a mismatch between listeners’ perception of their performance and their actual performance on intelligibility tasks.

Predicting speech intelligibility with a multiple speech subsystems approach in children with cerebral palsy.

PURPOSE Speech acoustic characteristics of children with cerebral palsy (CP) were examined with a multiple speech subsystems approach; speech intelligibility was evaluated using a prediction model in which acoustic measures were selected to represent three speech subsystems. METHOD Nine acoustic variables reflecting different subsystems, and speech intelligibility, were measured in 22 children with CP. These children included 13 with a clinical diagnosis of dysarthria (speech motor impairment [SMI] group) and 9 judged to be free of dysarthria (no SMI [NSMI] group). Data from children with CP were compared to data from age-matched typically developing children. RESULTS Multiple acoustic variables reflecting the articulatory subsystem were different in the SMI group, compared to the NSMI and typically developing groups. A significant speech intelligibility prediction model was obtained with all variables entered into the model (adjusted R2 = .801). The articulatory subsystem showed the most substantial independent contribution (58%) to speech intelligibility. Incremental R2 analyses revealed that any single variable explained less than 9% of speech intelligibility variability. CONCLUSIONS Children in the SMI group had articulatory subsystem problems as indexed by acoustic measures. As in the adult literature, the articulatory subsystem makes the primary contribution to speech intelligibility variance in dysarthria, with minimal or no contribution from other systems.

Unfamiliar listeners' evaluation of speech supplementation strategies for improving the effectiveness of severely dysarthric speech

This study examined listener attitudes toward three speech supplementation strategies (topic cues, alphabet cues, and combined topic and alphabet cues) associated with the speech of four individuals with severe dysarthria. Listeners saw experimentally imposed visual images of each strategy in conjunction with auditory presentation of the habitual speech of four individuals with dysarthria. Using a 7-point Likert scale, listeners rated how effective they thought the speakers were, how willing they would be to communicate with the speakers, and how persistent they were in trying to understand the speakers in each strategy condition and a control condition in which no cues were provided. The results revealed that ratings of communication effectiveness, willingness to communicate with the speakers, and listener persistence were each more favorable in the combined cues condition than in any other cue condition. The results suggest that augmentative and alternative communication strategies providing frequent and specific cues regarding the content and constituent words of a message may enhance the attitudes of listeners.

Augmentative and alternative communication for preschool children: intervention goals and use of technology.

This study sought to describe speech-language interventions for preschool-aged children who required augmentative and alternative communication (AAC) as provided by AAC experts and by general speech-language pathologists who were not AAC experts. The study also examined the types of technology used in AAC intervention by AAC experts. A retrospective chart review was conducted in which clinic records of 38 preschool-aged children who received expert AAC services were examined. Results showed that interventions provided to the children by general speech-language pathologists (who were not AAC experts) tended to be broader in scope, focusing on reducing underlying impairments. Interventions provided by AAC experts tended to focus on improving activities and participation and were oriented toward improving functional communication. The most commonly used AAC intervention tools by AAC experts were low-tech tools and simple digitized devices.

Speech and language development in 2-year-old children with cerebral palsy

Objective: We examined early speech and language development in children who had cerebral palsy. Questions addressed whether children could be classified into early profile groups on the basis of speech and language skills and whether there were differences on selected speech and language measures among groups. Methods: Speech and language assessments were completed on 27 children with CP who were between the ages of 24 and 30 months (mean age 27.1 months; SD 1.8). We examined several measures of expressive and receptive language, along with speech intelligibility. Results: Two-step cluster analysis was used to identify homogeneous groups of children based on their performance on the seven dependent variables characterizing speech and language performance. Three groups of children identified were those not yet talking (44% of the sample); those whose talking abilities appeared to be emerging (41% of the sample); and those who were established talkers (15% of the sample). Group differences were evident on all variables except receptive language skills. Conclusion: 85% of 2-year-old children with CP in this study had clinical speech and/or language delays relative to age expectations. Findings suggest that children with CP should receive speech and language assessment and treatment at or before 2 years of age.

A Preliminary Investigation of Longitudinal Changes in Speech Production over 18 Months in Young Children with Cerebral Palsy

Objective: This study examined longitudinal change in speech intelligibility, vowel space, and word duration over 18 months among children with cerebral palsy (CP) who varied in the severity of their speech motor involvement. The study also examined relationships among variables at each time point. Method: Twenty-two children with CP participated in the study (mean age = 50 months at the first time point). Speech samples were collected at four time points that were 6 months apart. Children were separated into four severity groups based on intelligibility scores. Results: Change over time varied by severity. Children with CP who did not have speech motor involvement and children in the mild group showed gains in intelligibility, but no changes in vowel space area or word duration. Children in the moderate group showed no significant change, and children in the severe group showed increased vowel space and decreased word durations. Significant positive correlations between intelligibility and vowel space were noted at each time point for data pooled across all children. Conclusion: Children showed different patterns of change over time in intelligibility, vowel space, and word duration based on their speech motor abilities. The relationship between intelligibility and vowel space across severity groups was constant, suggesting a robust relationship between these variables.

Longitudinal changes in feeding among children with cerebral palsy Between the ages of 4 and 7 years

Objective: To examine differences in feeding among children with cerebral palsy (CP) who varied in the severity of their oral motor involvement; to examine longitudinal change in feeding behaviours for different severity groups. Method: Twenty-three children with CP participated (mean age = 4.53 years at the first time point). Feeding data were collected from parent questionnaires at 6 month intervals over 30 months. Results: Significant differences were observed among severity groups for all feeding variables except coughing and choking during meals. Only one variable, coughing, showed significant change over time. Conclusions: Children with CP who had severe oral-motor involvement had marked and pervasive feeding difficulties which showed some fluctuation with time, but generally were stable. Children with CP who did not have oral motor involvement and those who had mild–moderate involvement also showed little-to-no change over time and had fewer problems than those in the severe group.

Alignment of classification paradigms for communication abilities in children with cerebral palsy

We examined three communication ability classification paradigms for children with cerebral palsy (CP): the Communication Function Classification System (CFCS), the Viking Speech Scale (VSS), and the Speech Language Profile Groups (SLPG). Questions addressed interjudge reliability, whether the VSS and the CFCS captured impairments in speech and language, and whether there were differences in speech intelligibility among levels within each classification paradigm.

Impact of sentence length and phonetic complexity on intelligibility of 5-year-old children with cerebral palsy

Abstract Reduced speech intelligibility is a barrier to effective communication for many children with cerebral palsy (CP). Many variables may impact intelligibility, yet little research attention has sought to quantify these variables. This study examined the influence of sentence characteristics on intelligibility in two groups of children with CP (those with and without dysarthria) and typically-developing children. Questions addressed effects of sentence length on transcription intelligibility among groups; effects of phonetic complexity on intelligibility; and differences in the relationship between sentence characteristics and intelligibility across individual children with dysarthria. Speech samples varying in length from 2–7 words were elicited from 16 children with CP (mean age 59.6 months) and eight typically-developing children (mean age = 59.8 months). One hundred and nineteen naïve listeners made orthographic transcriptions of the childrens sentence productions. Sentence length and phonetic complexity affected intelligibility for all groups of children, but had a greater impact on intelligibility for children with dysarthria than those without speech motor impairment. Variable relationships between sentence characteristics and intelligibility were found across individual children with dysarthria. Results suggest that reducing both the length and phonetic complexity of utterances may enhance intelligibility for children with dysarthria. However, there may be important individual differences in the impact of one or both types of sentence characteristics. This highlights the importance of considering individual speech motor profiles when deciding on treatment strategies.