Motor-based Intervention for Childhood Apraxia of Speech: DTTC-Connect

A Randomized Control Trial of Motor-based Intervention for Childhood Apraxia of Speech: Dynamic Temporal and Tactile Cueing-Connect (DTTC-Connect)

Childhood apraxia of speech (CAS) is a complex motor speech disorder that significantly limits a child's ability to communicate in daily activities, with difficulties often persisting into adolescence and adulthood. There is solid evidence that motor-based interventions, such as Dynamic Temporal and Tactile Cueing (DTTC), improve word production in children with CAS. Building on this strong foundation, the next critical step is to extend this work to support functional communication in connected speech, where children with CAS often continue to struggle. There is a critical need for a systematic bridge within the context of treatment from word-level practice to connected speech, as robust word-level gains often fail to generalize to other speaking contexts. This work addresses this gap by transitioning children from word- to phrase-level practice using Dynamic Temporal and Tactile Cueing-Connect (DTTC-Connect), a novel, structured adaptation of DTTC that targets connected speech production. Our approach builds on established DTTC principles while incorporating progression to more complex utterances, offering a developmentally appropriate, research-informed pathway to functional communication.

This study is a Phase II randomized controlled trial (RCT) designed to examine the efficacy of DTTC-Connect, a motor-based treatment that includes phrase-level practice to refine connected speech and support communicative participation for children with CAS. The overall objectives of this work are to test the efficacy of DTTC-Connect and document changes in speech motor control at the connected speech level in 68 children with CAS (3;6 - 12;11 years of age) who receive treatment twice a week for 8 weeks (16 sessions). The central hypothesis is that DTTC-Connect will lead to lasting improvements in phrase accuracy, speech intelligibility and speech motor control, ultimately enhancing a child's communicative participation.

The long-term goal of this research is to provide evidence-based treatment guidelines to enhance speech intelligibility and therefore, communicative participation, for children with childhood apraxia of speech (CAS). The overall objectives are to test the efficacy of Dynamic Temporal and Tactile Cueing-Connect (DTTC-Connect) and document changes in speech motor control at the connected speech level, when intervention is provided two times per week for eight weeks. The central hypothesis is that DTTC-Connect will lead to lasting improvements in phrase accuracy, speech intelligibility, and speech motor control, ultimately enhancing a child's communicative participation, as supported by our previous Dynamic Temporal and Tactile Cueing (DTTC) research and pilot data on DTTC-Connect. The following aims are examined:

Aim 1: Quantify the effects of DTTC-Connect on connected speech accuracy and whether previous DTTC modifies response to DTTC-Connect. 68 children with CAS will receive 8 weeks of DTTC-Connect, with a subset of children returning from the prior DTTC randomized controlled trial (RCT). The working hypothesis is that untreated phrase accuracy (primary outcome) and speech intelligibility (secondary outcome) will increase pre-post DTTC-Connect with gains maintained at 8 weeks post-treatment in all children. It is hypothesized that prior DTTC RCT performance (returning participants) will predict untreated phrase accuracy pre-post DTTC-Connect. Linear mixed-effects models will be used to estimate the DTTC-Connect treatment effect and the moderation effect of prior DTTC exposure.

Aim 2: Quantify the effects of DTTC-Connect on speech motor variability and whether previous DTTC modifies response to DTTC-Connect.

Acoustic and kinematic (lip/jaw movement) data will be obtained pre- and post- DTTC-Connect from 68 children with CAS, including a subset of children returning from the prior DTTC RCT. The working hypothesis is that variability (secondary outcome) will be reduced in all children following DTTC-Connect, with changes maintained at 8 weeks post-treatment. Inclusion of returning children will allow the examination of extended treatment on speech motor control. It is hypothesized that the change in variability in the prior DTTC RCT will moderate the treatment effect with DTTC-Connect. Linear mixed-effects models will be used to estimate changes in variability over time as in Aim 1.

Aim 3: Evaluate the effect of DTTC-Connect on communicative participation in children with CAS. Communicative participation (secondary outcome) will be assessed in all children pre- and post- DTTC-Connect. The working hypothesis is that children with CAS who receive DTTC-Connect will show meaningful gains in their attitudes about speaking and in caregiver-reported functional communication. Linear mixed-effects models will be used to estimate changes in communicative participation following DTTC-Connect.

Upon completion of these aims, the expected outcome is to establish the efficacy of DTTC-Connect in a large cohort of children with CAS, while uncovering how previous response to word-level DTTC informs individualized treatment planning. In doing so, it will generate actionable insights to enhance clinical outcomes while also deepening theoretical understanding of speech motor learning in CAS.

Inclusion Criteria:

1. Diagnosis of childhood apraxia of speech (CAS). The diagnosis will be made by two speech language pathologists (SLPs) who have extensive experience in the differential diagnosis of CAS.
2. Age between 3;6 and 12;11 years.
3. Normal structure of the oral-peripheral mechanism as determined by a motor speech examination using established lab protocol.
4. Participants must pass a hearing screening conducted at 20 dB SPL at 500, 1000, 2000 and 4000 Hz.
5. Not receiving speech treatment elsewhere over the course of this study, although language, augmentative and alternative communication (AAC) treatment, or similar non-speech treatment, would be permitted.
6. Language Testing: Receptive Language Index standard score greater than or equal to 70 on the Clinical Evaluation of Language Fundamentals - Preschool 3rd edition (CELF-P3) for children 3;6-5;11 years of age, or the Clinical Evaluation of Language Fundamentals - 5th edition (CELF-5) for children 6;0-12;11 years of age.
7. Nonverbal Cognition Testing: Standard score greater than or equal to 70 on the Developmental Assessment of Young Children-2nd edition (DAYC-2) for children 3;6- 5;11 years of age, or the Reynolds Intellectual Assessment Scales- 2nd edition, Remote (RIAS) for children 6;0-12;11 years old.
8. Evidence of multi-word spontaneous speech up to five syllables in length.
9. English as the primary language.

Exclusion Criteria:

1. Primary dysarthria diagnosis, even if CAS is a secondary diagnosis.
2. Abnormal structure of the oral peripheral mechanism.
3. Fluency disorder, even if the child meets criteria for CAS.
4. Conductive or sensorineural hearing loss, even if the child meets criteria for CAS.
5. English is not the primary language.