Choosing stimuli is probably one of the most important decisions a therapist makes when beginning treatment for childhood apraxia of speech. Thoughtful rationale for specific stimulus items can make a big difference in the rate and amount of early improvement in speech production, especially for children who exhibit severe deficits. This answer will specifically address the non-verbal or very severely apraxic child.
In order to decide what to work on within a session, one first must consider what we are really trying to do through therapy. For apraxic children, I think we are working to give the child the opportunity to practice planning, programming and executing accurate movement gestures (which is the neural processing that is not working efficiently for these children) for speech. That leads to the conclusion that the stimuli we choose must be speech. The stimulus set is used as a vehicle to practice the neural processing that is inefficient for them. We work to help them improve the accuracy of the movement gestures for the chosen words or phrases, first with maximum support (auditory, gestural, visual, tactile cues) and gradually fading that support as they achieve greater accuracy and more automaticity.
There is some controversy over whether to use nonsense verses real words. I always choose to use real words, which are functional, meaningful and very useful in the child’s environment. Early therapy is difficult, and slow. Helping the child master a few useful utterances gives him or her verbal power and helps them trust us and trust the process.
When choosing initial stimuli, I use the results of the motor speech examination to guide me, looking at the phonemic inventory, syllable shapes, and degree of vowel differentiation and accuracy. I then choose stimuli to build on each. These stimuli are typically chosen taking into account phonetic capabilities, earlier more visible and more easily tactically cued phonemes, as well as targeting specific vowel and syllable shapes. Improving vowel accuracy is extremely important early in therapy. I often target only one or two new vowels (that are not yet produced correctly by the child) along with utterances including vowels they can produce. Sometimes a child can produce a vowel in one co-articulatory context, but not others. That is a good early target, expanding the coarticulatory contexts in the initial stimulus set so that the child get practice in a number of articulatory contexts (e.g. me; knee; beep;).
Because the cognitive motor learning literature points out that mass practice facilitates motor performance (accuracy of the movement in the training session itself), I would suggest starting with a very small stimulus set. However, the motor learning literature also shows that if the set size is too small, it will inhibit motor learning or generalization. Therefore, with non-verbal and severely apraxic children I would recommend focusing on a core functional vocabulary of approximately 5-6 utterances at the beginning. As each individual utterance reaches criteria, that one is moved to generalization and a new one introduced. As the child improves his or her motor planning/programming abilities, mastery of utterances becomes faster, and then 2 utterances may be added as another is discontinued. Eventually, the set size will grow.
A case example may serve to illustrate the clinical thinking that may go into deciding on initial stimuli. AB is a 6 year old who is non-verbal due to severe apraxia of speech. There is no dysarthria or significant receptive language impairment. His only consonant is /m/ and he produces little vowel differentiation. The initial core vocabulary included the bilabial nasal /m/ plus two different vowels (“me” and “my”) that he could approximate with cuing. I also included the lingual alveolar nasal /n/ (“no”) as he did not yet produce that phoneme. This also served to expand the vowel inventory and give him some verbal power. I included “hi” and “bye” in the initial set to give him extra practice with /aI/ and to give him some social language. This also allowed us to begin work on bilabial plosing which he did not yet exhibit. This stimulus set allowed the therapist to improve AB’s ability to perform movement gestures for five different CV contexts, focusing on vowel differentiation, as well as correct movement gestures for /n/ and /b/ in at least one coarticulatory context. We also encouraged his mom to model and elicit “uh oh” frequently at home to facilitate further vowel differentiation.
As AB mastered each stimulus item, new items were introduced. We expanded bilabial plosing to different coarticulatory contexts and varied the voicing feature and added CVC and CVCV contexts as he improved (e.g. Pooh; dad; home; hi mom; me too; etc.). After a couple of months we were able to expand the stimulus set to 7, then after 6 months or so, to 10. Keep in mind that the stimuli are a vehicle to practice the motor planning/programming of movement gestures. Eventually, as severely apraxic children improve, we are frequently able to take a more phonologic approach to continued treatment and choose stimuli accordingly.
[Dr. Strand is a consultant in the Department of Neurology, Division of Speech Pathology, at the Mayo Clinic in Rochester, Minnesota, and Associate Professor in the Mayo Medical School. Her primary research and clinical interests have been in Neurologic Communication Disorders, especially childhood and acquired apraxia of speech, dysarthria, and neurologic voice disorders. She has published articles and chapters regarding the clinical management of motor speech disorders in children, including treatment efficacy. Dr. Strand is co-editor of the book (1999), Clinical Management of Motor Speech Disorders of Children. She lectures frequently throughout the country on childhood apraxia and motor speech disorders in both children and adults. Dr. Strand is a member of the Childhood Apraxia of Speech Association Professional Advisory Board.]