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#54  Shriberg's NEW Motor Speech Classification

Have you ever worked with a child with a significant speech sound delay but was unsure if the child’s speech was apraxic or dysarthric but you knew something “motoric” was going on? Yes? You’re not alone. Many of us have experienced the frustration of classifying the complex speech symptoms of a child with a non-organic, idiopathic (unknown) cause.
Drs. Shriberg, Kwiatkowski, and Mabie (2019) provide an answer with a new motor-classification term for speech delayed children with an unknown cause. They—plus several other colleagues over 30 years—have created and finalized the  Speech Disorders Classification System (SDCS).
I envision them putting their collective feet up, toasting a glass or two of wine, and expressing a looong sigh of relief.
The new classification term is:Speech Motor Delay (SMD).
The primary heading is Motor Speech Disorder (MSD). Under MSD is the new addition of 1) Speech Motor Delay (SMD), plus the existing terms, 2) Childhood Dysarthria (CD), 3) Childhood Apraxia of Speech (CAS), and 4) the combination of CD and CAS. The SMD is a good thing and something we all need to be aware of.
This, I believe, was their motivation (Shriberg, et al., 2019, page 3 of 31):
“In addition to CD, CAS, and concurrent CD and CAS, a fourth classification of childhood motor speech disorder has been a topic of speculation, but to date, has not been the focus of epidemiologic research. The hypothesis is that a presently unknown percentage of children with idiopathic speech-language delay have a “motor component” associated with the delay.
Such children may be found within groups of children posited to have general delays in motor development aggregated under such terms such as motor immaturity (Bishop, 2002), developmental coordination disorder (American Psychiatric Association, 2013; Duchow, 2019), and others that posit developmental deficits in sensorimotor domains that underlie the acquisition of articulate speech.
More frequently, a subgroup of children with motor disorder is posited for children with idiopathic SD who perform lower than age-sex norms on one or more gross-, fine-, or oral-motor tasks.
A central question for research and practice is whether a nosological classification is needed for children whose assessment findings are consistent with some type of motor component that does not meet standardized criteria for CD or CAS.”
And they followed through. All of this is detailed in their SDCS article, “Estimates of Prevalence of Motor Speech Disorders in Children with Idiopathic Speech Delay.” They determined and justified the addition of the SMD classification via in-depth analysis of the characteristics (i.e. markers) of hundreds of speech sound delayed children from six US cities over a period of 30 years.
Out of the 415 participants (ages 4 to 8 years of age) with idiopathic speech delay, 82.2% met criteria for a classification of No Motor Speech Disorder. With the remainder, the authors determined four motor-categories:
  • 12% met criteria for Speech Motor Delay (SMD)
  • 3.4% met criteria for Childhood Dysarthria (CD)
  • 2.4% met criteria for Childhood Apraxia of Speech (CAS)
  • 0% met criteria for both CD and CAS
No doubt, due to the importance of the content, everyone has “open access” to the six primary articles (the prevalence/idiopathic article is but one) within the journalClinical Linguistics & Phonetics, Volume 33, Issue 8. These were published online in April and June of 2019. (See Clinical Linguistics & Phonetics; Taylor & Francis).
In the above mentioned article, Dr. Shriberg and colleagues generated a Chart (see page 4, Figure 1) that depicts the four sections of theSpeech Disorders Classification System (SDCS). Although not formally stated, I believe it‘s safe to say that when idiopathic abnormal speech productions occur (or rather, normal speech fails to develop), the cause of the developmental diversion (or interruption, or obstacles) of the normal speech production act occurs somewhere within Sections 1 and 2. The resultant abnormal speech sound productions are classified in Section 3.
Following is an overview of the four sections within the Speech Disorders Classification System (SDCS). The primary categories are inbold, the sub-categories are initalics, and the classifications areunderlined. My interpretation and simplification attempts are in [brackets].
1. Etiological Processes (Distal Causes)
a.Genomic and Environmental Risk and Protective Factors
[hereditary and environmental factors; one or both probably]
b.Neurodevelopmental Substrates
[The CNS is responsible for developmental connections over time]
2. Speech Processes (Proximal Causes)
[This is the communication loop, if you will, of Representation, Transcoding, and Execution of the speech act.]
The following mutually and sometimes simultaneously interactvia feedforward and feedback:
a.Representation: Auditory / Somatosensory
[in this case, I believesomatosensory is the perception of sensations inside and outside the oral region, e.g., intra-oral tactile and proprioceptive sensations]
b. Transcoding: Planning / Programming
c. Execution[of the speech act]
3. Clinical Typology (Behavioral Phenotypes) [observable characteristics; types/classes of idiopathic abnormal speech productions]
a.Speech Delay (SD) [Ages 3 to 8-11; age-inappropriate speech sound deletions and/or substitutions]
  • Genetic (SD-GEN) [hereditary factors]
  • Otitis Media with Effusion (SD-OME) [“effusion” is the collection of non-infected fluid in the middle ear that can potentially impact hearing acuity and/or perception]
  • Developmental Psychosocial Involvement (SD-DPI)
b. Speech Errors (SE);[Age-inappropriate speech distortions that persist past 9 years of age; page 9 of 31]
  • /s/ (SE-/s/)
  • /r/ (SE-/r/)
c.Motor Speech Disorder (MSD)
  • Speech Motor Delay (SMD) [Meets Precision-Stability Index (PSI), page 9 of 31] [This analysis is explained in Shriberg, et al., 2010; in part, it appears to be similar to the terminology of speech stabilization and mobilization that I’ve referred to for 25 years.]
  • Childhood Dysarthria (CD)
  • Childhood Apraxia of Speech (CAS)
  • BothCD and CAS
4.Diagnostic Markers (Criterial Signs of Phenotype)
[Criteria/markers used to identify each speech and motor classification. Sorry, I didn’t get the full gist of these. Please refer to the article.]
A Few Interesting Passages
“The predominance of neurocognitive accounts of Speech Delay (SD) notwithstanding, there is substantial historical and contemporary research on the hypothesis that some children with idiopathic SD also have motor speech deficits that constrain the development of articulate speech” (page 2).
“Lack of consensus on inclusionary and exclusionary criteria for Childhood Dysarthria (CD) and Childhood Apraxia of Speech (CAS) has limited the conduct of epidemiological studies of the prevalence of idiopathic childhood motor speech disorders. Whereas the lack of widely used measures to identify and classify CD in children with idiopathic speech impairment may be associated withunder-diagnosis of CD, [and] prevalence estimates suggestingover-diagnosis of CAS have been widely discussed” [page 2; italics added].
The following is paraphrased from the bottom of page 4: The former provisional classification term was “Motor Speech Disorder – Not Otherwise Specified (MSD-NOS),” (Shriberg, et al., 2010). In 2019 the classification was changed to, “Motor Speech Disorder – Speech Motor Delay (MSD-SMD). [I rather liked the 2010 term “NOS;” I hope I can keep the acronyms straight.]
The Authors Conclusions (pages 22 & 23)
  • “The prevalence of motor speech disorders in children with idiopathic speech delay (SD) is theoretically and clinically substantial.”
  • “Idiopathic Speech Motor Delay (SMD) is a prevalent clinical entity.”
  • “Findings are interpreted to support an idiopathic subtype of Childhood Dysarthria (CD).”
  • “Findings cross-validate a prior prevalence estimate for Childhood Apraxia of Speech (CAS) of 1 child per 1,000.” “It is useful to note that each of the adjectives in a summary description of CAS over a decade ago, in which CAS was characterized asrare,severe, andpersistent disorder (ASHA, 2007), may not be accurate. On the rarity of CAS, although there is no international consensus on the criteria for rare diseases and disorders, a common epidemiological criteria for a rare disorder is a lifetime prevalence of 1 in 2,000 persons.”
  • "Cross-validation is needed of the present findings of 0% of CD and CAS in children with idiopathic SD."
Hope this has been helpful.
'Til next week,
Char Boshart
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
American Speech-Language-Hearing Association. (2007). Childhood apraxia of speech [Technical Report].[Online Link]
Bishop,D.V. (2002). Motor immaturity and specific speech and language impairment: Evidence for a common genetic basis.American Journal of Medical Genetics, 114,56-63.
Duchow, H., Lindsay, A., Roth, K., Schell, S., Allen, D., and Boliek, C.A. (2019). The co-occurrence of possible developmental coordination disorder and suspected childhood apraxia of speech.Canadian Journal of Speech-Language Pathology and Audiology, Vol 43, (2),81-93.
Shriberg, L.D., Fourakis, M., Hall, S.D., Krlsson, H.B., Lohmeier, H.Leeny, J.L., Potter, N.L., Scheer-Cohen, A.R., Strand, E.A., Tilkins, C.M., and Wilson, D.L. (2010). Extensions to the speech disorders classification system (SDCS).Clin Lingist Phon, Vol 24 (10),795-824.
Shriberg, L.D., Kwiatkowski, J., Mabie, H.L. (2019). Estimates of the prevalence of motor speech disorders in children with idiopathic speech delay.Clin Lingist Phon, Vol 33 (8), 1-31.[Online Link]

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