Childhood Apraxia of Speech (CAS) is a motor speech disorder that first becomes apparent as a young child is learning speech. For reasons not yet fully understood, children with apraxia of speech have great difficulty planning and producing the precise, highly refined and specific series of movements of the tongue, lips, jaw and palate that are necessary for intelligible speech.

Apraxia of speech is sometimes called verbal apraxia, developmental apraxia of speech, or verbal dyspraxia. Following the 2007 ASHA Ad Hoc Committee’s position statement the term childhood apraxia of speech is now most commonly used.  The most important concept is the root word “praxis.” Praxis means planned movement. To some degree or another, a child with the diagnosis of apraxia of speech has difficulty programming and planning speech movements. Apraxia of speech is a specific speech disorder. This difficulty in planning speech movements is the hallmark or “signature” of childhood apraxia of speech.

The challenge and difficulty that children with apraxia have in creating speech can seem very perplexing to parents, especially when they observe the skill of learning to speak developing seemingly without effort in other children.

How Does Speech “Happen”?

The act of speech begins with an intention to communicate. Next, an idea forms, outlining what the speaker wants to say. The words for the desired message are put in the correct order, using the correct grammar. Each word contains a specific sequence of sounds (also called phonemes) and syllables that must be correctly ordered together. All of this information is translated from an idea and information about order of sounds and syllables into a series of highly coordinated motor movements of the lips, tongue, jaw, and soft palate.

The brain must tell the muscles of these “articulators” the exact order and timing of movements so that the words in the message are properly pronounced. Finally, the muscles themselves must work properly with enough strength and muscle tone to perform the movements needed for speech. Amazingly, all of this happens in the blink of an eye.

When speech is developing in a normal way, children make word attempts and get feedback from people around them and from their own internal sensory systems regarding how “well” the words they produced matched the ones that they wanted to produce. Children use this information the next time they attempt the words and essentially are able to “learn from experience.” Usually once syllables and words are spoken repeatedly, the speech motor act becomes automatic and less effortful. The child doesn’t have to think about how to say the word or phrase they want to say. At this point, speech motor plans and programs are stored in the brain and can be quickly accessed and put together effortlessly when they are needed. Children with apraxia of speech have the most difficulty in this aspect of speech. It is believed that children with CAS may not be able to form or reliably access speech motor plans and programs or that these plans and programs are faulty for some reason. Unlike children developing typical speech, speech motor plans and programs for children with CAS fail to become automatic and easily accessed when they wish to speak.

Recent research also suggests that, to some degree or another, the sensory feedback loops needed for learning and acquiring accurate speech may not work well in children with apraxia of speech. There are several forms of feedback children use to learn speech and the complex series of movements underlying it. First, children use auditory information (through their hearing system) to judge whether their word attempt was correct. Researchers believe that the child’s speech processing system “couples” (or ties together) an auditory event – what they hear themselves say – with the movements of the oral structures needed to produce an utterance. Secondly, sensory feedback called proprioception is used so that the child knows where speech structures like lips, jaw, tongue, palate are physically located and how they relate spatially to one another during speech movement. So, for example, during speech attempts the child may not be aware of where their tongue is within the oral cavity or how its position relates to other structures like the lips. Sensory feedback is especially important during the learning of motor plans such as in early speech learning or speech acquisition. If these two feedback mechanisms are not working properly, speech intelligibility is affected.

Over the years, since the first accounts of the disorder, there has been disagreement over the underlying nature of the disorder. Some have proposed that CAS is linguistic in nature; others have proposed that it is motoric and some have put forth the tenet that it is BOTH linguistic and motoric in nature. However, currently nearly all sources describe the key presenting impairment involved with CAS as some degree of disrupted speech motor control. The reason for this difficulty is still under investigation by speech scientists.

Weakness, paresis, or paralysis of the speech musculature does not account for the impaired speech motor skills in CAS. Differences in various theories of speech motor control notwithstanding, it is believed that the level of impairment in the speech processing system occurs somewhere between phonological encoding and the motor execution phase, such as a disruption in motor planning and/or programming. Some believe that children with CAS have difficulty accurately storing or volitionally accessing speech motor plans and programs and the spatial-temporal specifications within them. To some degree or another, these impairments result in difficulty rapidly and accurately moving between sequences of articulatory configurations that are required for continuous and intelligible speech production. Some researchers posit that children with CAS additionally have disordered sensory-motor related features such as reduced or aberrant proprioception and thus an inability to realize the relationship and spatial position of the articulatory structures to one another. For some of the most severely affected children, even initiating speech movement gestures may prove extraordinarily difficult.

While CAS shares some features with adult acquired Apraxia of Speech, there are also key differences. Perhaps the biggest challenge of all is to understand the presumed effects of faulty motor speech control processes on the child’s developing speech processing system. In adult AOS, an assumption exists that the individual has an intact speech processing system. Exactly how CAS affects the developing speech processing system of affected youngsters remains to be seen. Presumably, however, there are reverberations and consequences throughout the system because of the speech motor deficits.

There appears to be some consensus and research evidence that children who display these sorts of speech motor impairments also typically have problems in certain aspects of expressive and/or receptive language, even if subtle. Reportedly, “pure” apraxia of speech in children is rare. There is currently no agreement as to whether these linguistic impairments are central to the disorder or are separate issues that co-occur or are co-morbid. Some individuals have described CAS as a disorder that changes and unfolds over time.

Incidence/Prevalence

Again, research is lacking in providing us with information regarding both incidence and prevalence figures. The estimates of some sources indicate that CAS is low incidence with perhaps 1 in 1000 children affected. In addition, some believe that the incidence of CAS may have increased in recent years.

This report is a comprehensive description and review of the current science and state of practice regarding childhood apraxia of speech. It concludes with recommendations from the ASHA Ad-hoc committee on CAS. This file is posted here with permission.

CAS_TECHNICAL_REPORT

When considering characteristics of the disorder, SLPs need to keep in mind that children with other speech sound disorders share some characteristics from the list. Other characteristics may be more common and contribute more specifically to the differential diagnosis of CAS, distinguishing CAS from the other pediatric speech sound disorders. Additional research is needed to identify a diagnostic marker with an acceptable degree of specificity and sensitivity (i.e.: identifies children with CAS while ruling out those who do not have CAS). Until such research data is available, the list below may be useful for identification of children suspected to have CAS.

Key characteristics:

• Limited repertoire of vowels; less differentiation between vowel productions; and vowel errors, especially distortions
• Variability of errors
• Unusual, idiosyncratic error patterns (sometimes defying transcription!)
• Errors increase with length or complexity of utterances, such as in multi-syllabic or phonetically challenging words.
• Depending on level of severity, child may be able to produce accurately the target utterance in one context but is unable to produce the same target accurately in a different context.
• More difficulty with volitional, self-initiated utterances as compared to over-learned, automatic, or modeled utterances
• Impaired rate/accuracy on diodochokinetic tasks (Alternating movement accuracy or maximum repetition rate of same sequences such as /pa/, /pa/, /pa/ and multiple phoneme sequences such as /pa/ /ta/ /ka/ )
• Disturbances of prosody including overall slow rate; timing deficits in duration of sounds and pauses between and within syllables contributing to the perception of excess and/or equal stress, “choppy” and monotone speech.
• At some point in time, groping or observable physical struggle for articulatory position may be observed (possibly not present on evaluation, but observable at some point in treatment).
• May also demonstrate impaired volitional nonspeech movements (oral apraxia)

Other characteristics that may describe children with CAS, but are less likely to contribute to a differential diagnosis include:

• Poor speech intelligibility
• Delayed onset of speech
• Limited babbling as an infant
• Restricted sound inventory
• Loss of apparently previously spoken words

Note that at the current time, SLPs do not demonstrate consistency in which characteristics they place more weight on than others in the diagnosis of CAS. Nor is it clear which or how many characteristics must be present for the diagnosis. Thus, SLPs must use a great deal of clinical judgment in diagnosis. (For more information see Forrest. K. (2003) Diagnostic criteria of development apraxia of speech used by clinical speech-language pathologists. American Journal of Speech-Language Pathology, 12(3), pp. 376 – 380.)

While there are many reasons that some children fail to develop age-appropriate speech and/or language skills, the following are frequently mentioned characteristics of children with apraxia of speech (not every child will have all characteristics.) This list was compiled from professional literature which is referenced at the end. Professionals and researchers do not all agree on the characteristics that define apraxia and some of those listed below may also be present in children with other severe speech sound disorders. If you are a parent and are worried about your child’s severely unclear or absent speech, we recommend you schedule a comprehensive speech and language evaluation by a qualified speech and language pathologist.

• Limited vocalization and sound play during infancy (parents often describe their child as a “quiet baby”)
• Limited number of consonant sounds
• Vowel errors and distortions
• May have developed elaborate nonverbal or gestural communication
• While repetition of sounds in isolation may be adequate, connected speech is more unintelligible than one would expect on the basis of single-word articulation test results. (Although the child may be able to produce sounds perfectly by themselves, he or she may make errors on these same sounds when combining them in longer units like words or phrases.)
• Initial and final consonant deletion, cluster reduction, syllable omissions, substitutions and distortions (speech errors in children with apraxia of speech are often referred to as inconsistent or unpredictable)
• Increase in errors with increase length of utterance, including problems producing multisyllabic words
• Voicing errors (i.e.: Some sounds are produced very similarly except one may use the vocal cords–“voiced”–and one may not–“voiceless.” For example, “P” and “B” are produced similarly. “P” is a voiceless consonant and “B” is a voiced consonant; “B” uses the vocal cords. Children with apraxia of speech can confuse or substitute these.)
• Errors vary with the complexity of articulatory adjustment. (Articulatory adjustments means the extent to which the articulators–lips, tongue, etc.– must shift between sounds in a word or phrase. A word like “baby” does not require much adjustment. A word like “dog” requires more adjustment.)
• Groping, trial and error behavior, struggling to deliver speech. The child in this struggle may make sound prolongations, repetitions, or silent posturing. (For instance, the mouth appears to “grope” or be searching for positioning. Or the child may use short sounds or words repeatedly, using the time to try and find the motor position for the next sound or word he or she wants to make. An example: “I, well, well, well, can’t do it.” This is not the same as stuttering. Silent posturing means a child’s mouth may move silently while he or she is searching for proper motor position.)
• Slow rate and incorrect sequencing, called diadochokinesis. (For example: ask the child to say “pah, tah, kah” three times, or a word such as “buttercup”. The child may get the sequence right the first time, but on subsequent attempts it will break down and the rate will be slowed.)
• Prosodic disturbances. Prosody is the melody of speech and includes rate, stress, pauses, and intonation. (Children with apraxia of speech may speak too slow or too fast. They may not put stress on the correct syllables. Their voices may sound monotone.)
• Oral apraxia sometimes, but not always, can accompany verbal apraxia. Oral apraxia is the impaired ability to, on command, perform nonspeech tasks like puffing out cheeks, licking lips, protruding tongue, puckering lips, etc.
• Apraxia of speech may occur in isolation or in combination with other speech and language problems. The incidence of “pure” apraxia of speech is reportedly low. Most typically, children will exhibit a number of problems that contribute to their difficulty with speech.
• Receptive ability far exceeds expressive ability (your child understands at a much higher level than he or she is able to express)
• Possible difficulty in feeding during infancy

Other “soft” neurological signs. Sometimes these children are described as awkward, uncoordinated, or clumsy. They may have difficulty organizing and coordinating fine motor skills too. Some parents report that their child may have sensory problems, poor body awareness, dislike toothbrushing, or seem sensitive to touch in their facial area.

References

Hall, Penelope, “The occurrence of developmental apraxia of speech in a mild articulation disorder: a case study,” Journal of Communication Disorders 22 (1989), 265 – 276.

Helfrich-Miller, Kathy, “Diagnosis of children with apraxia of speech,” presentation at Apraxia of Speech in Children: Clinical Challenges, Pittsburgh, PA, Nov. 1996.

Hodge, Megan, “Assessment of developmental apraxia of speech: a rationale. Clinics in Communication Disorders, 4 (2), 1994, 91-101.

Rosenbek, John and Robert Wertz, “A review of fifty cases of developmental apraxia of speech,” Language, Speech and Hearing Service in Schools 3 (1972), 23 – 33.

Strand, Edythe, “Treatment of motor speech disorders in children,” Seminars in Speech and Language, (16) 2, 1995, 126 – 139.

Velleman, Shelley, “Developmental verbal dyspraxia: general information for parents,” https://www.cs.amherst.edu/~djv/DVD.html

Shriberg, L. D., Kwiatkowski, J., & Mabie, H. L., “Estimates of the prevalence of motor speech disorders in children with idiopathic speech delay,” Clinical Linguistics & Phonetics (2019).

Shriberg, L. D., Strand, E. A., Jakielski, K. J., & Mabie, H. L., “Estimates of the prevalence of speech and motor speech disorders in persons with complex neurodevelopmental disorders,” Clinical Linguistics & Phonetics (2019).

Updated November 1, 2019.