Developmental apraxia of speech (DAS) is a poorly understood speech disorder in children. This paper describes important aspects of the disorder based on historical and current research findings combined with our own clinical observations. It is intended for parents and addresses the following questions:
- What is DAS?
- What are the characteristics of DAS?
- How is DAS diagnosed?
Part One: Basic Concepts
What is it?
DAS is a relatively rare disorder attributed to nervous system deficits in the planning and retrieval of speech sounds, given that the speech musculature is not weak or paralyzed. DAS is a controversial diagnosis. Controversy surrounds its definition, cause, clinical symptoms, treatment, and even existence as a distinct diagnosis.
What it’s called.
A variety of labels have been applied to children with characteristics of DAS, including articulatory apraxia, developmental articulatory dyspraxia, childhood verbal apraxia, developmental apraxia of speech, developmental dyspraxia of speech, and developmental verbal dyspraxia, among others. Currently, those who view the disorder as motor based (problems with movements) use the term DAS, while those who view the disorder as language based (problems with putting the parts of speech and language together for communicating) advocate for the term developmental verbal dyspraxia. Any of the above terms can be used interchangeably, as they all refer to a similar set of speech and language characteristics that define one disorder. Generally, the different terms reflect different ideas about the cause of the disorder, not differences in the defining characteristics of the disorder.
The different theories.
Several theories have been developed in an attempt to explain DAS. A brief overview of some of these theories follows. For individuals desiring more detailed information about these theories, please refer to the reference section at the end of this page.
Some theorists believe that children with DAS have difficulty producing speech because of subtle auditory (ex., hearing, listening) deficits. They believe that these deficits negatively affect the child’s ability to detect and /or encode speech sounds from conversational speech, even given normal results on hearing tests. At this time, these theories are only in preliminary stages of development.
Other researchers suggest that DAS may be caused by a child’s difficulty in building an adult-like language system, to include the speech sound, syllable, and speech melody components of language. The believe that the difficulty children with DAS have in producing speech is because of a more general problem in learning language.
The viewpoint of other researchers suggests that DAS can be attributed to problems in the child’s organization and sequencing of speech components (ex., speech sounds, syllables, speech melody). They believe that children with DAS have mentally stored the sounds, syllables, and melodies to select for speaking, but they do not have the skills to consistently organize and sequence movements into words and sentences.
In summary, no one theory has proven to be sufficient to account for the variety of characteristics present in children exhibiting DAS. Researchers continue to evaluate and develop these theoretical accounts.
Part Two: Characteristics
Speech and nonspeech characteristics have been included in the syndrome of DAS, although none of the characteristics appear to be unique to DAS alone. Children with DAS can exhibit characteristics ranging in severity from mild to severe. Generally, the more severe the DAS, the more characteristics exhibited. Some of the most common characteristics that have been reported in the literature follow.
- Child does not correctly use the sounds in some words that are produced in other words (ex., child says “tut” for “shut” but says “shun” for “sun”).
- Child does not consistently use sounds (ex., sometimes the child will correctly pronounce a simple word, while other times mispronounce it).
- Child frequently leaves sounds out of words (ex., child says “coo-ie” for “cookie”).
- Child mispronounces vowels in words (ex., child says “hut” for “hat”).
- The longer the word, phrase, or sentence, the more speech errors the child makes.
- Child produces words using simple consonant plus vowel patterns (ex. child says “tai tak” for “train track”).
- Child has significant difficulty imitating words and phrases.
- The prosody (melody) of speech is frequently altered.
- Child makes slow progress in speech therapy.
- Child has impaired ability to perform oral movements to command (ex., “puff out your cheeks”, “round your lips and blow out”).
- Child’s understanding of language is better than the child’s expression of ideas.
- Child is unusually slow when required to rapidly repeat syllables (ex., “say bababa until I ask you to stop”).
- Child substitutes gestures for oral communication (ex., pointing to objects wanted as opposed to verbally asking for them).
- On intelligent quotient (IQ) testing, performance IQ (“doing” tasks) is higher than verbal IQ (“talking tasks”).
- Gross motor skills (ex., running, climbing stairs, etc.) may also be slow in developing.
- DAS occurs in boys more often than in girls.
The most prominent characteristics of DAS.
The use of a group of prominent speech-related characteristics appears to be the most effective means of reliably determining a diagnosis of DAS. The following lists our proposed core of the most important features of DAS, compiled from the characteristics previously discussed. Whereas there may be additional characteristics, only those that appear necessary to identify DAS are included below. It is important to note that this list may need to be changed somewhat for older children and/or children who have undergone extensive speech therapy; these changes will be specific to each child, depending on their individual speech and language histories.
- Correct use of consonants and vowels is limited, even though the child may be able to produce a wide variety of sounds. Child can make the sound by cannot use it when needed.
- Correct pronunciation of multisyllabic or “difficult” words is limited (ex., “dinosaurs”, “peanut butter sandwich”, “choo choo train”).
- Consonant errors in conversational speech are highly variable (ex., one time the child correctly says “baby” and the next time incorrectly say “naby”).
- Vowel errors in conversational speech are highly variable ( ex., one time the child correctly says “dog” and the next time incorrectly says “dug”).
- Difficulty with several of the suprasegmental components of speech (pitch, vocal quality, rate, stress, intonation, and loudness). Pitch refers to the high-to-low tones of our speaking voice; vocal quality refers to the “smoothness”, harshness, or hoarseness of our speaking voice; rate refers to the speed at which we speak; stress refers to our ability to emphasize syllables; intonation refers to the “melody” of speech; and loudness refers to the quiet-to-loudness volume of our speaking voice.
Part Three: Diagnosing DAS
If children with DAS are to receive appropriate treatment, accurate diagnosis is crucial. Findings of a long-term study underway at the University of Texas at Austin indicate that DAS is often misdiagnosed. Resulting treatment programs may be inappropriate and ineffective. Below are guidelines for a speech and language evaluation, as well as assessment suggestions that can be used by the examiner to differentiate DAS from other disorders of speech and language.
Who should complete the testing?
DAS is a disorder of speech and language; therefore, it is strongly recommended that a speech-language pathologist who is certified by the American Speech-Language-Hearing Association (ASHA) be consulted to assess a child with suspected DAS. Again, DAS is a relatively rare disorder and not all speech-language pathologists will have had experience with diagnosing DAS. Ask the speech-language pathologist if they feel competent to conduct such testing and make a diagnosis. If they are not confident in their level of knowledge or experience, they should let you know. At any time, feel free to request a referral to another speech-language pathologist with more experience in DAS diagnosis.
Once you have located a speech-language pathologist to conduct the assessment, he/she will schedule the testing session(s). Depending on your child’s particular needs, the assessment could include a variety of tests. We believe that in evaluating a child for DAS, the most important component of the testing will be collecting a sample of your child’s conversational speech. Collecting this sample typically includes the speech-language pathologist audio- and/or videotaping while your child is communicating with you and/or the examiner. Some other tasks that may be completed during the assessment include: completion of a picture-naming speech test, examination of your child’s speech structures (lips, teeth, tongue, etc.), testing fine and gross motor skills (holding a crayon, jumping, etc.), and completion of diadochokinetic (rapid speech imitation) tasks.
After the assessment session has ended, the speech-language pathologist may need some time to analyze your child’s performances. We believe that the speech-language pathologist should begin the analysis process by selecting a portion of your child’s best attempts to communicate from the audio- or videotape. He/she will then write down what your child said and did during that portion of the tape. He/she will also write down exactly how your child said each word; this is known as “transcribing” a speech sample. For example, your child may have said the word “goggie” for “doggie”; this will be noted in the transcription. Once the sample has been completely transcribed, the speech-language pathologist will look for typical and atypical errors in your child’s speech. Determining the diagnosis will depend on the nature of the errors recorded, as well as your child’s performance on any of the other test measures.
Specific analysis suggestions.
We recommend that the speech and language sample be fully analyzed by the speech-language pathologist for the components that follow.
- Phonetic Inventory (consonants, vowels, word shapes)
This is an inventory of all of the consonant (ex., “k”, “b”, “s”, “tr”, etc.) and vowel (ex., “i”, “ee”, “ou”, etc.) sounds that your child can make, even if they are used incorrectly in words sometimes. This inventory will also include the different consonant (C) and vowel (V) combination patterns your child can make in words (ex., “stop” has a pattern of CCVC, “sit” has a pattern of CVC). The purpose of the phonetic inventory is to determine the sounds and sound combinations your child is currently capable of making.
- Relational Analyses (substitutions, omissions, distortions, phonological processes)
These analyses compare your child’s pronunciations to the correctly-produced words (ex., child says “tookie” and the target word is “cookie”). It will be determined if your child has sound substitutions (ex., saying a “t” sound for a “k” sound as in saying “tite” for “kite”), sound omissions (ex., leaving out sounds in words as in saying “ex” for “yes”), sound distortions (ex., saying a sound slightly distortedly as in “shun” for “sun”), and/or “phonological processes” (sound patterns that are either typical or atypical of young children and can include substitution, omission, and/or distortion errors). The purpose of these analyses is to compare your child’s speech with both same-age children and error-free adult speech.
- Suprasegmentals (pitch, vocal quality, rate, stress, intonation, loudness)
“Suprasegmentals” might best be considered to be the components of speech that provide its “melody” and vocal “expressiveness”. Children with DAS are different from children with other speech disorders in that children with DAS frequently have difficulty with several of the suprasegmental components of speech. For example, some children with DAS have difficulty managing loudness and quietness, while others have monotone speech. Since one or more suprasegmental components may be affected by DAS, it is recommended that all components be carefully analyzed.
- Receptive and Expressive Language Skills
The speech and language sample also should be analyzed for evidence of your child’s ability to understand language (receptive skills), as well as your child’s ability to express him/herself by correctly combining nouns, verbs, etc. in sentences (expressive skills). These analyses will include comparing your child’s language development to same-age children.
We realize the time-intensive nature of completing these detailed analyses; however, we believe that a diagnosis of DAS can be determined only after these in-depth spontaneous speech and language sample analyses have been completed.
The follow up conference.
Once the speech-language pathologist has analyzed your child’s assessment performance, he/she will be prepared to discuss the findings with you. This is typically done in person in a parent conference, although occasionally circumstances require that it be conducted over the telephone. Regardless, in this meeting the speech-language pathologist will share your child’s test results, compare your child’s speech development to children the same age, p provide a diagnosis, and possibly recommend a program of speech and language therapy. Often the test results, interpretations, and recommendations also will be provided to you in a written report.
It is important to realize that there may be several decisions facing you after the parent conference. You might wish to have a second opinion for another speech-language pathologist, in which case you would likely repeat the previously described evaluation process. You might need to schedule a second conference with the speech-language pathologist, if once you leave the office you find you have additional questions. And you might also need to decide if and where therapy for your child should begin. In any event, remember that there is likely to be a lot of new and confusing information provided to you. Be prepared to ask as many questions as necessary for you to gain an understanding of your child’s communication abilities. Speech-language pathologists are professionals interested in helping you understand your child’s speech and language systems, as well as helping to improve your child’s speech and language. Therapy for children with DAS can be a time-intensive endeavor, striving toward an open and working relationship with your speech-language pathologist will only add positively to the final results.
Unfortunately, there are no comprehensive books on DAS written for parents. The following two references are books written primarily for professionals; however, parents may find some sections helpful. Your speech-language pathologist should also be able to help direct you toward readings appropriate for your particular child.
Crary, M. (1993). Developmental Motor Speech Disorders. San Diego, CA: Singular Publishing Group, Inc.
Hall, P., Jordan, L., & Robin, D. (1993). Developmental Apraxia of Speech. Austin, TX: Pro-Ed.
In addition to the above references, the American Speech-Language-Hearing Association (ASHA) has a toll-free helpline that the public can access to obtain referrals to a speech-language pathologist in your local area. They can also tell you if a particular speech-language pathologist is ASHA certified, as well as provide some educational information. The ASHA Helpline operates from 8:30 am to 5:00 pm EST Monday-Friday and the telephone number is (800) 638-8255.