Developmental verbal dyspraxia

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Developmental verbal dyspraxia (DVD), also known as childhood apraxia of speech (CAS) and developmental apraxia of speech (DAS),[1] is an inability to utilize motor planning to perform movements necessary for speech during a child's language learning process. The exact cause of this disorder is unknown.[1] Some observations suggest a genetic cause of DVD, as many with the disorder have a family history of communication disorders.[1][2][3][4] There is no cure for DVD, but with appropriate, intensive intervention, people with this motor speech disorder can improve significantly.[5]

Characteristics[edit]

"Childhood apraxia of speech (CAS) is a neurological childhood (pediatric) speech sound disorder in which the precision and consistency of movements underlying speech are impaired in the absence of neuromuscular deficits (e.g., abnormal reflexes, abnormal tone). CAS may occur as a result of known neurological impairment, in association with complex neurobehavioral disorders of known or unknown origin, or as an idiopathic neurogenic speech sound disorder. The core impairment in planning and/or programming spatiotemporal parameters of movement sequences results in errors in speech sound production and prosody." American Speech-Language-Hearing Association (ASHA) Ad Hoc Committee on Apraxia of Speech in Children (2007)[5]

There are three significant features that differentiate DVD/CAS from other childhood speech sound disorders. These features are:

  • "Inconsistent errors on consonants and vowels in repeated productions of syllables and words
  • Lengthened coarticulatory transitions between sounds and syllables
  • Inappropriate prosody, especially in the realization of lexical or phrasal stress" [5]

Even though DVD/CAS is a developmental disorder, it will not simply disappear when children grow older. Children with this disorder do not follow typical patterns of language acquisition and will need treatment in order to make progress.[5]

Causes[edit]

DVD/CAS is a motor disorder, which means that the problem is located in the brain and its signals, and not in the mouth.[6] In most cases, the cause is unknown. Possible causes include genetic syndromes and disorders[6]

Recent research has focused on the significance of the FOXP2 gene[7][8][9][10][11] in both species and individual development.[12] Research regarding the KE Family, where half the members of the extended family, over 3 generations, exhibited heritable developmental verbal dyspraxia, were found to have a defective copy of the FOXP2 gene.[3][13] and further studies suggest that the FOXP2 gene as well as other genetic issues could explain DVD/CAS.[7][14] including 16p11.2 microdeletion syndrome[15][16]

Birth/prenatal injuries, as well as stroke, can also be causes of DVD/CAS. Furthermore, DVD/CAS can occur as a secondary characteristic to a variety of other conditions. These include Autism,[1] some forms of Epilepsy,[1] Fragile X syndrome, Galactosemia,[1][17] and chromosome translocations[12][18] involving duplications or deletions.[14][19]

Diagnosis[edit]

Developmental Verbal Dyspraxia can be diagnosed by a speech language pathologist (SLP) through specific exams that measure oral mechanisms of speech. The oral mechanisms exam involves tasks such as pursing lips, blowing, licking lips, elevating the tongue, and also involves an examination of the mouth. A complete exam also involves observation of the patient eating and talking. Tests such as the Kaufman Speech Praxis test,[20] a more formal examination, are also used in diagnosis.[20] A differential diagnosis of DVD/CAS is often not possible for children under the age of 2 years old. Even when children are between 2–3 years, a clear diagnosis cannot always occur, because at this age, they may still be unable to focus on, or cooperate with, diagnostic testing.[21]

Management[edit]

There is no cure for DVD/CAS, but with appropriate, intensive intervention, people with the disorder can improve significantly.[5]

DVD/CAS requires various forms of therapy which varies with the individual needs of the patient. Typically, treatment involves one-on-one therapy with a speech language pathologist (SLP).[6] In children with DVD/CAS, consistency is a key element in treatment. Consistency in the form of communication, as well as the development and use of oral communication are extremely important in aiding a child's speech learning process.

Many therapy approaches are not supported by thorough evidence; however, the aspects of treatment that do seem to be agreed upon are the following:

Although these aspects of treatment are supported by much clinical documentation, they lack evidence from systematic research studies. In ASHA's position statement on DVD/CAS,[5] ASHA states there is a critical need for collaborative, interdisciplinary, and programmatic research on the neural substrates, behavioral correlates, and treatment options for DVD/CAS.

Integral stimulation[edit]

One technique that is frequently used to treat DVD/CAS is integral stimulation. Integral stimulation is based on cognitive motor learning, focusing on the cognitive motor planning needed for the complex motor task of speech. It is often referred to as the "watch me, listen, do as I do" approach and is founded on a multi-step hierarchy of strategies for treatment. This hierarchy of strategies allows the clinician to alter treatment depending upon the needs of the child. It uses various modalities of presentation, emphasizing the auditory and visual modes. Experts suggest that extensive practice and experience with the new material is key, so hundreds of target stimuli should be elicited in a single session. Furthermore, distributed (shorter, but more frequent) and random treatment, which mix target and non-target utterances, produces greater overall learning.

The 6 steps of the hierarchy upon which integral stimulation therapy for children is loosely organized are:"

  • The child watches and listens and simultaneously produces the stimulus with the clinician.
  • The clinician models, then the child repeats the stimulus while the clinician simultaneously mouths it.
  • The clinician models and provides cues and the child repeats.
  • The clinician models and the child repeats with no cues provided.
  • The clinician elicits the stimulus without modeling, such as by asking a question, with the child responding spontaneously.
  • The child produces stimuli in less-directed situations with clinician encouragement, such as in role-play or games".

Integrated phonological approach[edit]

Another treatment strategy that has been shown to have positive effects is an integrated phonological approach. This approach "incorporates targeted speech production practice into phonological awareness activities and uses letters and phonological cues to prompt speech production".[23] McNeill, Gillon, & Dodd studied 12 children ages 4–7 with DVD/CAS who were treated with this approach 2x a week for two 6-week blocks of time (separated by a 6 week withdrawal block). They found positive effects for most of the children in the areas of speech production, phonological awareness, word decoding, letter knowledge, and spelling. These results show that it is clinically productive to target speech production, phonological awareness, letter knowledge, spelling, and reading all at once. This is particularly important since children with DVD/CAS often have continuous problems with reading and spelling, even if their production of speech improves.[23]

See also[edit]

References[edit]

  1. ^ a b c d e f Morgan AT, Vogel AP (March 2009). "A Cochrane review of treatment for childhood apraxia of speech". Eur J Phys Rehabil Med 45 (1): 103–10. PMID 19156019. 
  2. ^ Vargha-Khadem, F.; Watkins, K.; Alcock, K.; Fletcher, P.; Passingham, R. (Jan 1995). "Praxic and nonverbal cognitive deficits in a large family with a genetically transmitted speech and language disorder". Proc Natl Acad Sci U S A 92 (3): 930–3. doi:10.1073/pnas.92.3.930. PMC 42734. PMID 7846081. 
  3. ^ a b Watkins, KE.; Gadian, DG.; Vargha-Khadem, F. (Nov 1999). "Functional and structural brain abnormalities associated with a genetic disorder of speech and language". Am J Hum Genet 65 (5): 1215–21. doi:10.1086/302631. PMC 1288272. PMID 10521285. 
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  5. ^ a b c d e f g "Childhood Apraxia of Speech (Technical Report)" (pdf). American Speech-Language-Hearing Association (ASHA) Ad Hoc Committee on Apraxia of Speech in Children (2007). 
  6. ^ a b c "Childhood Apraxia of Speech". American Speech-Language-Hearing Association (ASHA. Retrieved 7 October 2013. 
  7. ^ a b Bacon C, Rappold GA (November 2012). "The distinct and overlapping phenotypic spectra of FOXP1 and FOXP2 in cognitive disorders". Hum. Genet. 131 (11): 1687–98. doi:10.1007/s00439-012-1193-z. PMC 3470686. PMID 22736078. 
  8. ^ Vernes, SC.; MacDermot, KD.; Monaco, AP.; Fisher, SE. (Oct 2009). "Assessing the impact of FOXP1 mutations on developmental verbal dyspraxia". Eur J Hum Genet 17 (10): 1354–8. doi:10.1038/ejhg.2009.43. PMC 2784575. PMID 19352412. 
  9. ^ Kang, C.; Drayna, D. (2011). "Genetics of speech and language disorders". Annu Rev Genomics Hum Genet 12: 145–64. doi:10.1146/annurev-genom-090810-183119. PMID 21663442. 
  10. ^ MacDermot KD, Bonora E, Sykes N, et al. (June 2005). "Identification of FOXP2 truncation as a novel cause of developmental speech and language deficits". Am. J. Hum. Genet. 76 (6): 1074–80. doi:10.1086/430841. PMC 1196445. PMID 15877281. 
  11. ^ Preuss TM (June 2012). "Human brain evolution: from gene discovery to phenotype discovery". Proc. Natl. Acad. Sci. U.S.A. 109 Suppl 1: 10709–16. doi:10.1073/pnas.1201894109. PMC 3386880. PMID 22723367. 
  12. ^ a b White SA, Fisher SE, Geschwind DH, Scharff C, Holy TE (October 2006). "Singing mice, songbirds, and more: models for FOXP2 function and dysfunction in human speech and language". J. Neurosci. 26 (41): 10376–9. doi:10.1523/JNEUROSCI.3379-06.2006. PMC 2683917. PMID 17035521. 
  13. ^ Vargha-Khadem F, Gadian DG, Copp A, Mishkin M (February 2005). "FOXP2 and the neuroanatomy of speech and language". Nat. Rev. Neurosci. 6 (2): 131–8. doi:10.1038/nrn1605. PMID 15685218. 
  14. ^ a b Newbury, DF.; Mari, F.; Sadighi Akha, E.; Macdermot, KD.; Canitano, R.; Monaco, AP.; Taylor, JC.; Renieri, A. et al. (Apr 2013). "Dual copy number variants involving 16p11 and 6q22 in a case of childhood apraxia of speech and pervasive developmental disorder". Eur J Hum Genet 21 (4): 361–5. doi:10.1038/ejhg.2012.166. PMC 3598310. PMID 22909776. 
  15. ^ Raca, Gordana; Baas, Becky S; Kirmani, Salman; Laffin, Jennifer J; Jackson, Craig A; Strand, Edythe A; Jakielski, Kathy J; Shriberg, Lawrence D (2012). "Childhood Apraxia of Speech (CAS) in two patients with 16p11.2 microdeletion syndrome". European Journal of Human Genetics 21 (4): 455–459. doi:10.1038/ejhg.2012.165. PMID 22909774. 
  16. ^ Worthey, EA.; Raca, G.; Laffin, JJ.; Wilk, BM.; Harris, JM.; Jakielski, KJ.; Dimmock, DP.; Strand, EA.; Shriberg, LD. (2013). "Whole-exome sequencing supports genetic heterogeneity in childhood apraxia of speech". J Neurodev Disord 5 (1): 29. doi:10.1186/1866-1955-5-29. PMC 3851280. PMID 24083349. 
  17. ^ Shriberg, LD.; Potter, NL.; Strand, EA. (Apr 2011). "Prevalence and phenotype of childhood apraxia of speech in youth with galactosemia". J Speech Lang Hear Res 54 (2): 487–519. doi:10.1044/1092-4388(2010/10-0068). PMID 20966389. 
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  19. ^ Lennon PA, Cooper ML, Peiffer DA, et al. (April 2007). "Deletion of 7q31.1 supports involvement of FOXP2 in language impairment: clinical report and review". Am. J. Med. Genet. A 143A (8): 791–8. doi:10.1002/ajmg.a.31632. PMID 17330859. 
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  21. ^ Grigos, Maria I.; Kolenda, Nicole (January 2010). "The relationship between articulatory control and improved phonemic accuracy in childhood apraxia of speech: A longitudinal case study". Clinical Linguistics & Phonetics 24 (1): 17–40. doi:10.3109/02699200903329793. PMC 2891028. PMID 20030551. 
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  23. ^ a b McNeill, B. C.; Gillon, G. T.; Dodd, B. (2009). "Effectiveness of an integrated phonological awareness approach for children with childhood apraxia of speech (CAS)". Child Language Teaching and Therapy 25 (3): 341–366. doi:10.1177/0265659009339823. 

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