Motor Speech Disorders
In motor speech disorders, the brain's control of speech is affected. Motor speech disorders include childhood dysarthria, childhood apraxia of speech, and motor speech disorder not otherwise specified.
In childhood dysarthria, children have difficulty producing intelligible speech due to neuromuscular difficulties that impact execution of speech movements. These difficulties may be due to increased or decreased muscle tone, reduced drive to muscles, reduced force of muscle contraction, delayed initiation of movement, reduced speed of movement, restricted range of motion, or incoordination between speech systems such as respiration and phonation. These impairments can result in speech differences such as abnormal loudness, pitch, articulatory precision, resonance, voice quality, and breath support. Ultimately, a person's speech sounds distorted and less clear. About 1 in 1000 children have dysarthria (Shriberg et al., 2019).
Childhood Apraxia of Speech
Childhood apraxia of speech (CAS) is a neurological paediatric speech sound disorder. It occurs when a child has difficulty planning/programming speech movements. It is estimated that about 2 in 1000 children have idiopathic CAS (Shriberg et al., 2019) - CAS in which there is no known congenital or neurological disorder (e.g., Down Syndrome). The incidence is a little higher (about 4-5%) in children with neurological or congenital disorders associated with CAS (e.g., Down Syndrome, stroke, infantile spasms).
Children with CAS may demonstrate the following types of speech difficulties (Ozanne, 2005):
inconsistent errors - the same word or sound may be said differently each time they say it, with different errors each time
word examples: 'ambulance' - "ambance, amlulance, amblan", 'dada' - "deedee, dawdaw, dada"
sound example: 'l' at the ends of words - "n, d" or omitted
unusual 'prosody' (stress and intonation patterns)
add pauses between syllables
trouble with 'lexical stress' - stress that conveys meaning (e.g., CONtract vs conTRACT) - putting equal stress on each syllable in a word or putting stress on the wrong syllable
distorted vowels and consonants
more trouble with longer words than short ones
more trouble with volitional speech (i.e., when asked to say something specific on command) than automatic speech (i.e., saying the alphabet) and imitating sounds/words
trouble sequencing sounds and syllables
metathesis - switching sounds or syllables around in words (e.g., 'foliage' becomes "foilage")
non-speech oral apraxia (NSOA) - difficulty with non-speech movements of the mouth
not all children with CAS have NSOA, so although it might support a diagnosis of CAS, it does not indicate CAS
trouble programming the parameters of speech production (i.e., timing, force, spatial parameters)
oral groping (trial and error movements of the mouth)
asymmetrical oral movements
A diagnosis cannot be given for CAS until a child is at least 3 1/2 and has enough connected speech. Signs that may indicate difficulty with motor speech programming in younger or minimally verbal children may include the following (Strand, 2003):
small phonemic inventories (only say a limited number of speech sounds)
"go to" words/sounds (uses the same sound or word approximation for all things such as "nuh" or "dee")
oral groping when trying to speak
In young, minimally verbal children (e.g., <3 years), a child may present in such a way that CAS is sometimes suspected (sCAS), or it's deemed that motor speech development should be monitored. The following behaviours and features that are looked for by SLPs and are considered when making differential diagnoses between sCAS, autism spectrum disorders, language delay, or other speech sound delays/disorders:
atypical early development (birth to 15m)
desire and motivation to speak and interact
play skills (should be typical, although the presence of limb apraxia can effect execution of movements needed for play)
non-verbal communication skills
gap between expressive and receptive language (children with only CAS will generally have good receptive skills)
effort when speaking
"pop-out" words (say word once and not again)
"go-to" sound/word (a word or sound that is used to express many things, e.g., "dee" for everything; and may be strung together to form "sentences", e.g., "dee dee dee")
There are three main causes of CAS:
idiopathic neurogenic speech sound disorder - CAS without any known neurological injury, abnormality, or neurobehavioural disorder
secondary to a neurological injury such as stroke, infection, traumatic brain injury, or tumour
associated with a neurobehavioural or congenital disorder such as epilepsy or Down Syndome
There are a number of approaches to treatment for CAS. It is very important to understand that progress is often slow. Speech is an incredibly complex skill. Treatment for a young child with suspected CAS may take three years or more. Some children will require treatment throughout their preschool and school years. The earlier treatment is started, the better.
There are a number of intervention approaches that may be considered when providing treatment. These may include but are not limited to Dynamic Temporal and Tactile Cueing, Nuffield Dyspraxia Program, Rapid Syllable Transition Treatment, Integrated Phonological Awareness Intervention, PROMPT, and augmentative communication. Ultimately, treatment should always be individualized to the child.
Who Diagnoses CAS?
The answer to this question depends on which province you reside in. In Nova Scotia, CAS, may be identified by a speech-language pathologist, as it is a communication disorder. You may encounter professionals who are not aware of this, particularly those who do not work directly with children with motor speech disorders or who are from other Canadian provinces where the diagnosis must be made by a doctor (although typically their diagnosis is made after consideration of an SLP's findings). However, it is important to understand that when CAS is secondary to a neurological condition (e.g., stroke, Down Syndrome, seizure disorder) that this primary medical diagnosis must be made by an appropriate medical professional such as a neurologist.
To learn more about the scope of practice of speech-language pathologists, you can refer to the following documents:
"Audiologists and Speech-Language Pathologists Act"
Government of Nova Scotia
"Scope of Practice for Speech-Language Pathology in Canada"
Speech-Language and Audiology Canada
"Childhood Apraxia of Speech: Information for Parents" (video)
"Childhood Apraxia of Speech"
American Speech-Language-Hearing Association
"Examples of Different Levels of Severity of CAS" (video)
"Differentiating Childhood Apraxia of Speech (CAS) from other types of speech sound disorders"
Dr. Edythe Strand, Mayo Clinic
Videos of Children with CAS
"Darien's Journey with Childhood Apraxia of Speech"
"Severe Childhood Apraxia of Speech 3yr 9mo"
"Childhood Apraxia of Speech: SO MUCH PROGRESS"
Note: Cooper has both CAS and autism
"My daughter's journey with Childhood Apraxia of Speech"
Videos of Adults with CAS
"Growing up with Verbal Apraxia (CAS) - Q&A"
In this short video, Jordan Christian answers some frequently asked questions about growing up with CAS.
"My Battle with Childhood Apraxia of Speech"
Note: Aaron uses the term 'stutter' to describe some of his difficulties with speech. Although there are certainly individuals who have CAS and who stutter, stuttering is not a feature of CAS. He also describes his experience with physiotherapy. Some children with apraxia of speech can also have dyspraxia - motor programming difficulties that affect other areas of the body such as limb movements. However, not all children who have apraxia of speech will have dyspraxia affecting other types of movements. Parents can talk to their pediatrician or family doctor if they suspect dyspraxia.
References on This Page
Ozanne, A. (2005). Childhood apraxia of speech. In B. Dodd (Ed.), Differential diagnosis and treatment of children with speech disorder (2nd ed., pp. 71-82). Whurr Publishers Ltd.
Shriberg, L. D., Kwiatkowski, J., & Mabie, H. L. (2019). Estimates of the prevalence of motor speech disorders in children with idiopathic speech delay. Clinical Linguistics & Phonetics, 33, 679-706. https://doi.org/10.1080/02699206.2019.1595731
Strand, E. (2003). Clinical and professional ethics in the management of motor speech disorders. Seminars in Speech and Language, 24, 301-11. doi: 10.1055/s-2004-815583