The goal of this clinical trial is to learn if speech supplementation can improve speech intelligibility in children ages 7 to 17 years with cerebral palsy. The main questions it aims to answer are:

• To what extent can speech supplementation improve intelligibility in children with CP compared with habitual speech produced without speech supplementation?
• How much intelligibility change is necessary for meaningful improvement when children use speech supplementation strategies?

Participants will:

• complete speech and language assessments
• complete a speech pre-test using habitual speech
• learn a speech supplementation strategy with training from a speech-language pathologist
• complete a speech post-test using the speech supplementation strategy
• complete a speech repetition task where specific words are emphasized (emphatic stress)
• use the previously learned speech supplementation strategy + emphasis on specific words while producing a set of sentences

This study uses a pre-/post- test design to test the effects of a one-session intervention to improve speech intelligibility in 100 children with cerebral palsy and dysarthria. The intervention involves the augmentative and alternative communication (AAC) strategy known as speech supplementation. Specifically, children will learn how to simultaneously speak and point to the first letter of each word on a communication board, or to speak and point to a topical picture on a communication board. The strategy serves to provide listeners with context cues for spoken words, and it also serves to impact temporo-acoustic features of speech by reducing rate of speech and making word boundaries clear.

In this study, children will first participate in a set of baseline assessment measures, which will include the production of a corpus of 60 sentences (referred to as "habitual speech"). Then, children will learn to use the speech supplementation strategy through one-on-one clinician modeling, teaching, and practice. When children have mastered the strategy on a set of practice sentences, they will complete a post-test in which they produce the same set of elicited sentences a second time using speech supplementation.

Pre-test and post-test speech samples will then be played to two groups of listeners. One group will orthographically transcribe the words produced by children in both conditions (habitual and supplemented). Listener transcriptions in each condition will be scored as correct or incorrect based on whether they matched the intended word. Average percent of words identified correctly will be obtained from 2 listener for each child and each speaking condition as measures of speech intelligibility. The difference between habitual speech (pre-test) and supplemented speech (post-test) will be examined to quantify the effects of the speech supplementation on intelligibility.

The second set of listeners will hear the same speech samples as the first set (habitual speech and supplemented speech), but they will make ratings of whether one of the conditions seems more understandable than the other, and if so, they will rate how much better using a 7-point Likert scale.

These two sets of data from listeners will enable us to measure the minimum detectable difference in speech intelligibility and then the minimal clinically important difference based on listener ratings. Together these measures will enable us to determine how much change in intelligibility is necessary in order for clinically meaningful improvement.

The hypotheses are as follows:

1. speech supplementation will result in increased speech intelligibility relative to habitual speech.
2. the minimal clinically important difference in intelligibility scores to consider the speech supplementation strategy "successful" will vary depending on child severity, with more severely speech impaired children requiring a larger improvement to achieve a clinically meaningful change.

Inclusion Criteria:

• Medical diagnosis of cerebral palsy, or a similar, related condition that affects early motor development and presents as a chronic motor disability
• Age between 7 and 17 years
• Clinical dysarthria with speech intelligibility between 10-85 percent
• Able to produce connected speech in English, with a minimum utterance length of 3 words
• Able to use hands to point to items on a communication board
• Cognitive/language skills that enable basic picture identification on a communication board
• Pass pure tone hearing screening

Exclusion Criteria:

• Failure to meet all inclusion criteria.
• Vision impairment that precludes being able to see items on a communication board.
• Not suitable for participation due to other reasons at the discretion of the investigators.

Individual participant data collected during the trial, after deidentification.

Beginning 9 months after publication of primary outcomes, and ending 5 years after that date.

Data will be shared with researchers whose proposed use of the data has been approved by an independent review committee identified for this purpose. Data will be shared for the following types of analyses: Independent verification of study outcomes or to conduct subsequent clinical research.

Proposals should be directed to kchustad@wisc.edu. If approved after review by regulatory counsel, requestors will enter into a formal data sharing agreement. Data will be shared via encrypted single-user file transmission protocol.