http://informahealthcare.com/pdrISSN: 1751-8423 (print), 1751-8431 (electronic)

Dev Neurorehabil, Early Online: 1–8! 2013 Informa UK Ltd. DOI: 10.3109/17518423.2013.832431

ORIGINAL ARTICLE

Motor speech treatment protocol for developmental motorspeech disorders

Aravind Namasivayam1, Margit Pukonen2, Jennifer Hard1, Rene Jahnke2, Elaine Kearney1, Robert Kroll2, &Pascal van Lieshout1,3,4,5,6

1Department of Speech-Language Pathology, University of Toronto, Toronto, Ontario, Canada, 2The Speech & Stuttering Institute, Toronto, Ontario,

Canada, 3The Toronto Rehabilitation Institute, Toronto, Ontario, Canada, 4Department of Psychology, University of Toronto, Toronto, Ontario,

Canada, 5Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada, and 6Graduate Department of

Rehabilitation Science, University of Toronto, Toronto, Ontario, Canada

Abstract

Objective: This study examines the effect of the Motor Speech Treatment Protocol (MSTP), amulti-sensory hybrid treatment approach on five children (mean: 3;3 years; S.D. 0;1) with severeto profound speech sound disorders with motor speech difficulties.Methods: A multiple probe design, replicated over five participants, was used to evaluate theeffects of treatment on improving listeners’ auditory and visual judgements of speech accuracy.Results: All participants demonstrated significant change between baseline and maintenanceconditions, with the exception of KM, who may have had underlying psychosocial, regulationand/or attention difficulties. The training- (practiced in treatment) and test-words (not practicedin treatment) both demonstrated positive change in all participants, indicating generalizationof target features to untrained words.Conclusion: These results provide preliminary evidence that the MSTP, which integrates multi-sensory information and utilizes hierarchical goal selection, may positively impact speechsound production by improving speech motor control in this population.

Keywords

Children, developmental motor speechdisorders, motor speech control, speechsound disorder

History

Received 24 June 2013Revised 2 August 2013Accepted 3 August 2013Published online 1 October 2013

Introduction

Speech Sound Disorders (SSDs) is a broad term that

encompasses a range of children’s speech problems including

linguistic (phonological) and motor-based disorders of sound

production. In a phonological disorder, the child has difficulty

learning the rules that govern the use of sounds in the

language while in a motor-based speech disorder, such as

dysarthria or childhood apraxia of speech (CAS), the child

demonstrates difficulty executing and/or planning the move-

ments required for speech production. Dysarthria and CAS are

both neurologically based motor speech disorders, with

dysarthria being an impairment in the execution of speech

movements (e.g. due to weakness or incoordination) and CAS

being an impairment in the planning of speech movements

[1]. Many children demonstrate both linguistic and motor

difficulties to varying degrees and it is the clinician’s role to

determine the relative contribution of linguistic and motor

factors in order to select the most appropriate intervention

approach. Although there are several treatment approaches in

use for SSDs [2], data on treatment effects and efficacy are

sparse [3]. Recent Cochrane reviews on the treatment of

children with motor speech disorders have indicated a critical

lack of treatment efficacy studies in this area [4, 5].

Two of the popular approaches for the treatment of

children with SSDs with severe-profound motor speech

difficulties are Prompts for Restructuring Oral Muscular

Phonetic Targets (PROMPT) [6] and Dynamic Temporal and

Tactile Cueing (DTTC) [7]. PROMPT is theoretically

grounded in the principles of sensorimotor skill learning [8]

and assumes a hierarchical development of speech subsystems

(also known as the Motor Speech Hierarchy; MSH) [9].

Within this hierarchy, seven motor speech subsystems are

identified (i.e., Stage I: tone, Stage II: phonatory control,

Stage III: mandibular control, Stage IV: labial-facial control,

Stage V: lingual control, Stage VI: sequenced movements and

Stage VII: prosody). Goal setting in PROMPT is based on the

child’s level and quality of speech motor control within each

speech subsystem with treatment progressing from lower to

higher levels of the hierarchy. Tactile cueing is a primary

treatment technique used to support improved speech motor

control and movement accuracy during speech production.

DTTC utilizes a temporal cueing hierarchy to shape speech

movement gestures and improve the accuracy of speech

production. The approach varies rate of production, and the

temporal delay between clinician model and child response

(simultaneous production, imitation, delayed imitation and

Correspondence: Dr. Aravind Namasivayam, Department of Speech-Language Pathology, Oral Dynamics Lab, University of Toronto,160-500 University Avenue, Toronto, Ontario M5G 1V7, Canada.Tel: +1 416 946 8552. Fax: +1 416 978 1596. E-mail: a.namasivayam@utoronto.ca

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spontaneous speech) in addition to multi-sensory cueing [10].

In both approaches, speech goals are realized through a

combination of suitable task complexity, type of cueing,

appropriate and accurate feedback [8].

Currently, there is insufficient published research regard-

ing the effectiveness of such motor speech treatments. Both

PROMPT and DTTC do have some preliminary support for

their effectiveness in children with SSDs with motor speech

involvement. For example, direct tactile-kinesthetic input

using PROMPT treatment was applied to 12 children (4–6

years of age) with SSDs with motor speech difficulties [11].

Children participated in sixteen, 45-min therapy sessions over

an 8-week treatment block. These children demonstrated

significant changes in speech motor control and speech

intelligibility. Strand et al. [7] utilized the DTTC approach

with four children (5.5–6.1 years of age) with severe CAS and

mild coexisting dysarthria. Two of them showed improvement

in articulatory accuracy and number of functional utterances

produced over a six week treatment block, consisting of

38–50 half-hour sessions.

The Speech and Stuttering Institute (S&SI) has worked for

many years with children with severe SSDs who present with

varying degrees of speech motor involvement. The S&SI has

developed an intervention approach which integrates core

concepts found in motor-based interventions such as

PROMPT and DTTC and principles of motor skill learning

[8]. The approach, the Motor Speech Treatment Protocol

(MSTP), integrates several ‘‘key ingredients’’ of intervention

found in motor-based approaches that support speech motor

skill development, speech sound development and improved

speech intelligibility. The ‘‘key ingredients’’ include selection

of speech targets based on a child’s level of speech motor

control, use of temporal and multisensory cueing strategies to

improve the quality of the child’s speech production skills,

and structuring practice opportunities in communication

based activities in a manner that facilitates acquisition and

generalization of speech motor skill learning.

The current study was designed to examine the effects of

the integrated MSTP approach on children with severe to

profound SSDs with motor speech difficulties. It specifically

aims to verify the effects of MSTP at an individual level

(phase 1) before research can progress to treatment efficacy

research with larger sample sizes (phase 2–3).

Materials and methods

Research design

The current study uses a multiple-probe design with varying

baseline lengths [12] relating to changes in labial-facial

control (i.e. individuated lip movement for /f/ and /v/),

replicated over five participants to evaluate the effects of the

MSTP on improving a listener’s auditory and visual judge-

ments of speech accuracy. This design (e.g. Figure 2),

includes data series from five participants with the introduc-

tion of intervention at a different point in time for each series.

In this manner, we can document experimental control by

demonstrating a co-variation between introduction of the

intervention and change in behaviour within five different

series (participants) at five different points in time. This

design permits us to ensure internal validity and attribute

changes to treatment, rather than extraneous variables such as

history and maturation [13]. Further, we also demonstrate

experimental control with a staggered introduction of inter-

vention within a multiple baseline design (mandibular vs.

labial-facial). This method allows for demonstration of

experimental control, both within each data series and also

across data series at staggered times of intervention for one

participant. This approach could not be used for all partici-

pants because they did not share similar treatment goals. For

example, for NN, both jaw and lip data were targeted in

treatment, whereas other participants, such as for DR, the jaw

was not targeted and therefore the treatment began by

targeting the lips. Additionally, group data averaged across

the five participants for speech intelligibility measures is

presented to allow for comparison between the present study

and other similar studies in the literature.

Participants

Five children (KM, DR, BT, NN, OP; 4 males: 1female; mean

age: 3;3 years; S.D.: 0;1; range: 3;2–3;5) with severe to

profound SSDs participated in this study. Children were

included if they met the following criteria: English as the

primary language, age-appropriate play and social skills, and

vision, hearing, receptive language and oro-facial structural

mechanisms within normal limits. Additionally, they had to

present with speech delays (below 16th percentile, see

exception for DR; Goldman-Fristoe Test of Articulation -2;

GFTA-2) [14], severe to profound SSDs (Hodson

Computerized Analysis of Phonological Patterns test;

HCAPP) [15] and signs of motor speech involvement (e.g.

consonant and vowel distortions, lateral jaw sliding, decreased

lip rounding and retraction; for an extensive list see

Namasivayam et al. [11]). In the current study, no participant

met diagnostic criteria for Autism Spectrum Disorders (ASD),

dysarthria or CAS [16]. Information about ASD status was

obtained from the case histories and clinical reports obtained

upon referral. To identify dysarthria and CAS, procedures

similar to those reported in the literature were used [11, 17].

Participants were classified as having dysarthria (and

excluded) if they had evidence of global motor involvement,

feeding difficulties, signs of drooling, or inadequate breath/

phonatory support for speech. The diagnosis of CAS was

based on the S-LP’s clinical judgment of whether or not

features of CAS such as variable productions, difficulty

maintaining sound and syllable integrity with increased length

and complexity of utterance and prosodic abnormalities were

present (see ASHA, 2007 [16] for a detailed list of features;

[17]). The children were recruited from The Speech &

Stuttering Institute in Toronto, Ontario. The study was

approved by the University of Toronto’s Health Sciences

Research Ethics Board (Table I).

Listeners

For the assessment of children’s speech intelligibility, 9 naive

listeners (4 males: 5 females; mean¼ 24.2 years; S.D.¼ 6.1)

were recruited from the University of Toronto. All listeners

were native speakers of English who were blind to the identity

and treatment phase of the children participating in the study.

All listeners passed a pure tone hearing screening at 1, 2, and

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4 kHz at 25 dB HL and reported little or no exposure to the

speech of children with speech disorders.

Independent variable/treatment description

Within the MSTP framework, the child’s control of movement

for various speech subsystems is observed and any movement

disturbances are noted at each level of the MSH. The lowest

level of the MSH at which the child is demonstrating

difficulties is typically the starting point for intervention. The

movement pattern to be developed is identified and target

sounds and syllable/word shapes that are produced with the

specific motor movement(s) are selected as the intervention

targets. The words/phrases are functional and important for

the child and family. Several techniques are used to help the

child to improve the quality of his/her speech production. The

primary cueing strategies are visual and auditory (e.g. ‘‘watch

me’’, ‘‘say ___’’). Reducing the rate of production and

varying the time delay between the model and the child’s

production are strategies that are also frequently employed

[7]. Tactile cues, where the clinician touches the child’s face,

may also be used to help the child improve his/her speech

production. For example, the clinician may support the child’s

jaw to achieve appropriate range of jaw movement or touch

the child’s lips to cue a round mouth, spread lips or move the

lips together [6].

Production practice during the therapy sessions is based on

motor learning principles and is organized to support the

acquisition and generalization of new speech production skills

[8]. A large number of practice trials (opportunities for

multiple repetitions) are provided throughout the session and

the practice of targets is both massed and distributed. The

child is provided with information about the quality and/or

success of his/her productions through knowledge of per-

formance, with specific information about how the movement

was made. Knowledge of results is given to provide the

children with general feedback about the overall success of

the production and/or to motivate and reinforce production

attempts. Within a goal area, the treatment progression is

typically from single relatively easy words, to production of

the target words in longer utterances, to the introduction of

new, motorically more complex target words.

Procedures

The participants attended individual, 45-min speech therapy

sessions, twice a week for 10 weeks for a total of 20 treatment

sessions, plus pre- and post-treatment assessment sessions.

Treatment goals for participants focused hierarchically on

mandibular, labial-facial or lingual control. Data was col-

lected across three phases of intervention – baseline,

treatment and maintenance. A baseline was established for

the target behaviours across a minimum of 3 and maximum of

8 sessions using a probe word list. The number of sessions in

the baseline condition depended on how many other goals

were targeted prior to the labial-facial control goal. The

number of sessions in the treatment phase also varied across

participants, depending on the number of sessions that

targeted individuated lip movement for /f/ and /v/. Each

participant had three maintenance data points, which were

collected during the post-therapy assessment sessions.

The probe word lists contained 25 training words and

25 test words, with 5 training and 5 test words per goal. The

training words were targeted for intervention and practiced

directly in the treatment session. The test words were not

targeted in therapy and were used to measure generalization.

The probe wordlists were administered every other session.

Each session was videotaped and scored visually after-

wards (with sound turned off) for speech movement charac-

teristics (henceforth speech motor performance) and

auditorily (with video-monitor turned off) for perceptual

accuracy (henceforth perceptual performance) by a qualified

Speech-Language Pathologist (S-LP), blinded to the treatment

phases (baseline, treatment and maintenance). The train/test

words were scored on a three point scale (0¼major error;

1¼minor error; 2¼ age appropriate production), with a

maximum possible score of 10 (i.e. 5 train words �2 points

for age appropriate production¼maximum score of 10). The

phonetic characteristics of place (where articulators create the

constriction in the vocal tract), manner (the type of constric-

tion), and voice (whether the vocal folds are vibrating or not)

were used in the scoring process [18]. When scoring visually

for speech movement characteristics, a single change in place

or manner was considered a minor error while more than one

change was a major error. When scoring auditorily for

perceptual performance, a single change in place, manner or

voice was a minor error, while more than one change was a

major error. A second S-LP rated 30% of the data and inter-

rater reliability for these procedures was 88% (listeners’

auditory judgement of speech accuracy) and 92% (visual

judgement of speech movement accuracy) accuracy of speech

movements.

Further, standard speech intelligibility assessments were

carried out pre- and post-treatment as outcome measures at

the word- and the sentence-level. For the word-level task, the

percentage of imitated single words correctly understood by a

listener was evaluated using the Children’s Speech

Intelligibility Measure (CSIM) [19]. The child’s recorded

productions were played to the naive listeners whose task it

was to circle the words they thought they heard from a list of

12 similar sounding words. For the sentence-level task, the

Table I. Participant demographics.

ID Age (years; months) Gender Prior treatment history GFTA-2 percentiles HCAPP - severity

KM 3;4 F Private SLP in 2009 11 Low SevereDR 3;3 M Private SLP in 2009;TPSLS Jan 2009–Aug 2010 18 SevereBT 3;3 M n/a 9 SevereNN 3;2 M Private SLP 1/week for 4 weeks 8 Low ProfoundOP 3;5 M n/a 7 High Severe

DOI: 10.3109/17518423.2013.832431 Motor speech treatment 3

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percentage of words correctly understood in imitated sen-

tences was assessed using the Beginner’s Intelligibility Test

(BIT) [20]. The BIT test involves administration of 1 of 4

standard 10-sentence lists. Each sentence contains 2–6 words

that are familiar to children. The child must repeat the

sentence immediately following the clinician’s model and

unlike CSIM, the BIT is a transcription based procedure

where the naive listeners wrote down what they heard. All the

participant’s speech samples were audio-recorded using the

H4 Zoom digital recorder at a rate of 44.1 kHz with a

resolution of 16 bits per sample and saved as WAV files. From

these audio samples playlists were generated by digitally

removing extraneous sounds (e.g., doorbell, laughing and the

S-LP’s speech). The RMS loudness of the stimuli was

adjusted to approximately 70 dB SPL and was played twice to

the listeners in a sound-treated room. All sound manipulation

and editing were carried out using the PRAAT program

Version 5.3.21 [21].

Statistical analysis

Single-subject data were analyzed using the two standard

deviation band (2SD) analysis method or the celeration line

analysis method [22]. If there was no baseline trend, the 2SD

method was used whereas if the baseline data showed an

overall upward trend, then the celeration line approach was

used. In the 2SD method, results are significant if two or more

points fall above the 2SD line while in the celeration line

method, results are considered significant if greater than 50%

of the treatment and maintenance training data points fall

above the estimated trend.

The outcome measure (speech intelligibility) was ana-

lyzed as group data using paired 2-tailed t-tests. Cohen’s d

statistic corrected for dependence between the means was

used to calculate effect sizes [23]. Effect sizes of 0.2, 0.5

and 0.8, are often referred to as small, medium, and large

effects, respectively. The alpha level for significance was set

at 0.05.

Results and discussion

The baseline, treatment and maintenance phase results for all

participants are shown in Figure 1(a–e). For each participant,

speech motor performance scores (left panel) and perceptual

performance scores (right panel) are displayed on separate

graphs, with both ‘‘train’’ and ‘‘test’’ probe words indicated

with solid and dotted lines, respectively. The dashed line

represents the þ2SD mark or the celeration line. All

participants demonstrated significant differences between

the baseline and the maintenance phase with the exception

of KM. Generally, perceptual performance reflected a similar

pattern of improvement as seen with speech motor perform-

ance (Figure 1(a–e)). Similar to findings reported elsewhere

[11], these results demonstrate that the control of speech

movements has an effect on the speech accuracy judgments

made by independent naı̈ve listeners. The ‘‘train’’ and ‘‘test’’

probe words both demonstrated positive change for all

participants, indicating generalization of target features to

untrained words. The performance of each participant is

described in more detail below.

For KM, the celeration line analysis indicated a signifi-

cant and positive change in the perceptual performance

scores (Figure 1(a), right panel; 4 of 7 data points in

treatment and maintenance phases above trend line). On the

other hand, data related to the speech motor performance

(Figure 1(a), left panel) failed to reach statistical signifi-

cance (only 1 of 7 data points in treatment and maintenance

phases above trend line), although it demonstrated subtle

positive change in the maintenance phase. An explanation

for limited change in KM may be due to underlying

psychosocial, regulation and attention difficulties.

Challenges such as difficulty focusing on the task were

noted by the clinician conducting the therapy as well as the

clinician scoring the videos.

A celeration line analysis was used for DR due to a slight

upward trend in speech motor performance (Figure 1(b), left

panel). Intervention led to a significant change in perform-

ance, with 5 of the 7 ‘‘train’’ data points in the treatment and

maintenance phases located above the predicted trend line.

Gains made in the treatment phase were maintained during

the maintenance phase. On the perceptual accuracy rating, the

downward sloping baseline allowed for the 2SD method of

analysis. As demonstrated in Figure 1(b), right panel,

significant (p50.05) change in performance was evident

only in the maintenance phase of the probes. DR’s perceptual

performance rating demonstrates a slightly unusual pattern.

There is a discrepancy between the speech motor performance

and the perceptual performance scores at T5. Wherein the

former demonstrated an increase, the latter demonstrated a

sudden drop. On careful inspection it was found that DR had

started to ‘‘overproduce’’ or exaggerate his /f/ sound by

blowing too hard through his upper teeth and lower lip

resulting in a loud, strained sounding /f/, while maintaining

appropriate speech motor movements. This resulted in the

speech motor performance being scored higher than the

perceptual performance at T5.

For BT and NN, the baseline data did not show an

upward trend, allowing for the 2SD band method of analysis.

For both participants, the speech motor and perceptual

performance ratings (Figure 1(c and d)), displayed a signifi-

cant (p50.05) change at the maintenance phase.

The baselines for OP did not show a trend, indicating that

the 2SD band method of analysis is appropriate. OP

demonstrated significant (p50.05) change during the treat-

ment and maintenance phases of the study. Interestingly, for

OP there is an initial improvement in speech motor

performance (T1) that is followed by a decrease (T2 and

T3,) and then again an increase (T4 and T5) for ‘‘train’’ data

points (Figure 1e). Such fluctuation in motor performance

curves over the course of treatment (or practice) is not

uncommon as reported in the motor learning literature [21].

Initially, OP’s speech motor performance was supported by

the clinician’s cues/prompts and models. As therapy pro-

gressed, these additional supports were gradually withdrawn,

as per protocol. However, OP’s speech motor system may

not have fully acquired or stabilized the new labio-facial

movement patterns resulting in a decrease in performance.

Additional practice in therapy likely would have allowed

him to re-organize parameters of movement, control degrees

of freedom, increase stability, and successively refine speech

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motor movements resulting in an increase in speech motor

performance scores (e.g. see Vereijken et al. [24]). It is also

noteworthy, that OP’s maintenance scores (M1 and M2) are

significantly lower than the preceding treatment points. The

clinician’s notes from those sessions reported OP to be

resistant to completing the probe words and appeared very

easily discouraged, which could explain these variances in

the data.

Figure 1. (a–e) Represents data from fiveparticipants. Gains in treatment were mea-sured as a function of change in visual andauditory accuracy. Vertical lines indicate theonset of treatment and maintenance phases.A solid line represents words targeted intreatment while a dotted line represents testwords. Diagonal and horizontal dashed linesindicate the celeration line and 2SD linerespectively, depending on whether a trend inbaseline data were present.

0

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B1 B2 B3 B4 T1 T2 T3 T4 M1 M2 M3

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or S

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Speech Motor Performance for KM

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Test

Baseline Treatment Maintenance

Es�mated trend

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B1 B2 B3 B4 T1 T2 T3 T4 M1 M2 M3

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Perceptual Performance for KM

TrainTest

Baseline Treatment Maintenance

Es�matedtrend

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B1 B2 B3 T1 T2 T3 T4 T5 M1 M2 M3

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TrainTest

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B1 B2 B3 B4 B5 T1 T2 T3 T4 T5 M1 M2 M3

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Speech Motor Performance for BT

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B1 B2 B3 B4 B5 B6 B7 B8 T1 T2 T3 T4 T5 T6 M1M2M3

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+2SD

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(b)

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In the current study, internal validity was achieved in two

ways. First, experimental control by demonstrated by the

presence of a co-variation between the introduction of the

intervention and a change in behaviour across five data

series (participants) at five different points in time (Figure

2). Second, experimental control was further demonstrated

with a staggered introduction of intervention within a

multiple baseline design (mandibular vs. labial-facial) for

one participant (Figure 3). Taken together, Figures 2 and 3

demonstrate experimental control, both within each data

series and also across data series at staggered times of

intervention [12].

Analysis of group data on speech intelligibility indicated

that participants increased by approximately 14% and 17% at

the word-level (CSIM) and sentence-level (BIT), respectively

(Table II). Paired t-test results indicated that intelligibility

changes at the word-level were significant, t(4)¼ 2.9,

p¼ 0.04; 95% confidence intervals (CI) �27.9881 to

�0.7679, with very large effect sizes d¼�4.79, while

changes at the sentence-level demonstrated only a statistical

trend, t(4)¼ 2.5, p¼ 0.06; 95% CI �36.0229 to 1.7589, but

with a large effect size of d¼�1.85. For the word-level

speech intelligibility measure, the 90% CI for percentage

scores are available in the CSIM Manual [17]. Post-test scores

outside of this 90% CI indicate an actual change in child’s

performance. In general, post-test scores outside of 90% CI of

pre-test scores were correlated with approximately 8–10%

change in participant’s speech intelligibility. In other words,

an 8% change could be seen as a cut-off for speech

intelligibility test scores outside of measurement error.

Based on this criteria most participants showed positive

change following MSTP intervention.

Figure 2. Speech motor performance acrossall participants.

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Conclusions

These results provide preliminary evidence that the

MSTP, which integrates key ingredients such as hierarchical

motor-based goal selection, multi-sensory cueing and motor

learning principles may positively impact speech intelligibil-

ity and speech sound production by improving speech motor

control (e.g. in the labial-facial system) in children with

severe to profound SSDs. While there were significant

improvements, there was also individual variability in the

amount, nature, and rate of therapeutic gains following the

MSTP intervention. As this study only included five partici-

pants, the results cannot be generalized. Further studies using

group designs and larger sample sizes are required to increase

the validity and generalizability of these preliminary phase 1

results.

Acknowledgements

The study was carried out by the Ministry of Youth Services

(ON, Canada) via The Speech and Stuttering Institute and a

treatment research grant from the Childhood Apraxia of

Speech Association of North America (CASANA) awarded to

first author (AN). Thank you to the families who participated

in the study.

Declaration of interest

The authors report no conflicts of interest. The authors alone

are responsible for the content and writing of this article.

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Table II. Group data analysis.

Participant CSIM_Pre CSIM_Post % Change BIT_Pre BIT_Post % Change

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