The impact of the speech systems approach on intelligibility for children with cerebral palsy: a secondary analysis

Background The motor speech disorder, dysarthria, is common in cerebral palsy. The Speech Systems Approach therapy programme, which focuses on controlling breath supply and speech rate, has increased children’s intelligibility.

Objective To ascertain if increased intelligibility is due to better differentiation of the articulation of individual consonants in words spoken in isolation and in connected speech.

Design Secondary analysis.

Setting University.

Participants Forty-two children with cerebral palsy and dysarthria aged 5–18 years, Gross Motor Function Classification System I–V.

Intervention The Speech Systems Approach is a motor learning therapy delivered to individuals by a speech and language therapist in 40-minute sessions, three times per week for 6 weeks. Intervention focuses on production of a strong, clear voice and speaking at a steady rate. Practice changes from single words to increasingly longer utterances in tasks with increasing cognitive load.

Main outcome measures Unfamiliar listeners’ identification of singleton consonants (e.g. nap) and clusters of consonants (e.g. stair, end) at the start and end of words when hearing single words in forced choice tasks and connected speech in free transcription tasks. Acoustic measures of sound intensity and duration.

Data sources Data collected at 1-week pre- and 1-week post-therapy from three studies: two interrupted time series design, one feasibility randomised controlled trial.

Results Word initial and word final singleton consonants and consonant clusters were better identified post-therapy. The extent of improvement differed across word initial and word final singleton consonant subtypes. Improvement was greater for single words than connected speech. Change in sound identification varied across children, particularly in connected speech. Sound intensity and duration increases also were inconsistent.

Limitations The small sample size did not allow for analysis of cerebral palsy type. Acoustic data were not available for all children, limiting the strength of conclusions that can be drawn. The different but phonetically balanced word lists, used in the original research, created variability in single words spoken across recordings analysed. Low frequencies of plosives, fricatives and affricates necessitated their combination for analysis preventing investigation of the effect of specific consonants. Connected speech was spontaneous, again creating variability within the data analysed. The estimated effects of therapy may therefore be partially explained by differences in the spoken language elicited.

Conclusions The Speech Systems Approach helped children generate greater breath supply and a steady rate, leading to increased intensity and duration of consonant sounds in single words, thereby aiding their identification by listeners. Transfer of the motor behaviour to connected speech was inconsistent.

Future work Refining the Speech Systems Approach to focus on connected speech early in the intervention. Personalisation of cues according to perceptual and acoustic speech measures. Creation of a battery of measures that can be repeated across children and multiple recordings.

Study registration This trial is registered as Research Registry 6117.

Funding This project was funded by the National Institute for Health and Care Research (NIHR) Efficacy and Mechanism Evaluation programme (NIHR130967) and will be published in full in Efficacy and Mechanism Evaluation; Vol. 10, No. 4. See the NIHR Journals Library website for further project information.