Vol. 18 •Issue 21 • Page 6
Apraxia of Speech
Sound Production Treatment
Ahierarchical treatment process that incorporates elements of phonological processing and motor speech targets has evolved to become an effective tool for treating patients with apraxia of speech (AOS).
Sound Production Treatment (SPT) is a five-step approach developed by Julie Wambaugh, PhD, CCC-SLP, and colleagues at the VA Salt Lake City Healthcare System and VA Pittsburgh Healthcare System.1-3It was based on an earlier eight-step continuum developed by John Rosenbek, PhD, CCC-SLP, of the University of Florida in Gainesville and colleagues.4Dr. Wambaugh's interest in phonological processing led her to incorporate minimal pair treatment into the hierarchy she and her colleagues developed in the early 1990s.
"We used integral stimulation, modeling and articulatory placement instructions and combined it with minimal pairs treatment," she told ADVANCE. "At the time we still weren't quite clear as a research discipline whether apraxia of speech was only a motor speech disorder or if there were some phonological aspects to it."
Since that time, research has indicated that AOS is a motoric, phonetic-level disorder.
The therapy model is response-contingent, so not every patient will complete each step of the hierarchy. "You only use the steps as you need them," said Dr. Wambaugh, an associate professor at the University of Utah in Salt Lake City and Research Career Scientist with the VA Salt Lake City Healthcare System. "You don't use every step with every single person with every single attempt."
The first step of the hierarchy incorporates minimal pairs contrast. If the target sound is produced incorrectly after a verbal model, then the clinician also asks the patient to produce a contrasting minimal pair word. Patients who are unable to complete the first step move onto the second step using a visual cue. The therapist uses a depiction of the written letter to facilitate the patient's production of a target sound, again in a repetition-modeling paradigm.
The third step incorporates an integral stimulation approach of "watch me, listen to me, say it with me" that was based on Dr. Rosenbek's research. In the fourth step articulatory placement cueing is used along with modeling. Dr. Wambaugh's early research sought to determine whether work on one sound through the hierarchy would result in the generalization of improved sound production and articulatory skills as a whole.
"We treated just one sound at a time using single subject experimental designs so we could control the behavior, see the variability, understand what we were doing, and see if there was any generalization," she explained. The researchers found little generalization across sounds, unless they were closely related to each other, such as /s/ and /sh/.
They expanded the research to study patients with voicing issues, a common problem for the AOS population. Patients most commonly struggle with the devoicing of voiced sounds but some may produce voiceless sounds as voiced. The patient in Dr. Wambaugh's study struggled with devoicing.
Dr. Wambaugh focused on one sound at a time and noted that the patient was able to generalize to the other stops he was working on as well as an affricate but not to a substantial level of clinical success. "He went from zero or 20 percent accuracy up to 50 or 60 percent but never got to the 80 or 100 percent accuracy that we were achieving with the sound we were working on," she said.
The generalized sounds still required separate treatment. "You don't get across-the-board improvements in articulatory accuracy in this treatment," she said. "We've seen some generalization when sounds are closely related in terms of what's going wrong but not to the extent that it would eliminate the need for treatment for those sounds."
Further research revealed some overgeneralization using the hierarchy, Dr. Wambaugh noted. "When you work on that one sound, or even a few sounds, some patients often start to use that sound excessively."
This type of overgeneralization was demonstrated in a single-subject design study involving a patient working on three sequential sounds.5After mastering the first sound he moved onto the second one but regressed in his progress on the first because of overgeneralized use of the second sound. This happened again with training of a third sound. However, the patient was able to maintain his mastery of all three sounds after receiving a "booster treatment" upon completion of regular therapy.
"The sound we were working on started to become the predominant sound," Dr. Wambaugh stated. "Overgeneralization was one thing we pointed out, and other people have noted since."
She then began to focus on ways to make SPT more efficient without compromising the specificity required to treat AOS. "It's a pretty sound-specific treatment, but it's a pretty sound-specific disorder," she said.
Each patient requires an individualized version of the treatment with target items being selected on the basis of their unique sound errors. Some patients may be able to handle work on up to three sounds at a time, depending on the severity of their apraxia.
Expanding from single-sound treatment has an additional benefit, she noted. "The patient has to discriminate between those sounds when you're training them, and it seems to help prohibit unwanted overgeneralization."
Extensive research over the years has resulted in some changes to the original hierarchy. In particular, there is an increased focus on motor learning principles and their relation to speech learning.
"There's little data in that area right now, but intuitively it makes sense that some of these principles should apply," said Dr. Wambaugh, who has closely followed the motor learning research of Donald Robin, PhD, CCC-SLP, of the Research Imaging Center at the University of Texas Health Science Center at San Antonio.
The revised hierarchy calls for the clinician to begin working on the target sound immediately and to use minimal contrast-which formerly had been the first step-only if needed. "We never work on sounds alone. We always work on sounds in the context of a word or phrase."
She prefers to work with patients on real words and to use non-real words only in cases required to form a minimal contrast word. Working with real words eliminates a step of generalizing from nonreal to real words. In addition, in Dr. Wambaugh's experience "persons with aphasia tend to do better with the semantic context provided by the real word," she said.
The revised hierarchy also has an increased emphasis on repeated practice. When a correct production is achieved at any step of the hierarchy, the patient is asked to do five repeated practices of the target item.
Dr. Wambaugh is expanding her research to include patients who have either milder or more severe AOS. Most of her earlier research focused on patients with mild-to-moderate or moderate-to-severe cases of AOS.
"We're looking forward to submitting a grant so that we can examine the effect of this treatment in terms of the frequency of treatment application and the effects of that on outcomes," she said.
Dr. Wambaugh also is at work on a VA-funded study on the effect of rate and rhythm control treatment for sound errors in AOS. The study will examine the effect of repeated practice treatment as compared to repeated practice treatment with the addition of rate control. "There's never really been a control for just mere practice," she said.
1. Wambaugh, J.L. (2004). Stimulus generalization effects of sound production treatment for apraxia of speech. Journal of Medical Speech Language Pathology, 12(2): 77-97.
2. Wambaugh, J.L., Kalinyak-Fliszar, M.M., West, J.E., et al. (1998). Effects of treatment for sound errors in apraxia of speech. Journal of Speech, Language, and Hearing Research, 41: 725-743.
3. Wambaugh, J.L., & Nessler, C. (2004). Modification of Sound Production Treatment for Aphasia: Generalization effects. Aphasiology, 18(5): 407-427.
4. Rosenbek, J.C., Lemme, M.L., Ahern, M.B., et al. (1973). A treatment for apraxia of speech in adults. Journal of Speech and Hearing Disorders, 16(4): 462-472.
5. Wambaugh, J.L., Martinez, A.L., McNeil, M.R., et al. (1999). Sound production treatment for apraxia of speech: Overgeneralization and maintenance effects. Aphasiology, 13(9): 821-837.
- Wambaugh, J.L. (2006). Treatment guidelines for apraxia of speech: Lessons for future research. Journal of Medical Speech-Language Pathology, 14(4): 317-321.
- Wambaugh, J.L., Duffy, J.R.., McNeil, M.R., et al. (2006). Treatment guidelines for acquired apraxia of speech: A synthesis and evaluation of the evidence. Journal of Medical Speech-Language Pathology, 14(2): xv-xxxiii.
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