Lawrence D. Shriberg
PhD, University of Kansas Medical Center
Professor Emeritus, Communicative Disorders
Approximately 15% of 3-year-old children have speech intelligibility challenges that are not associated with known etiologies. By first grade, approximately 25% of these children (about 3.5% of all children) retain a significant speech disorder of currently unknown origin. The goals of our research are to understand the etiological origins of such disorders and to develop assessment and treatment methods that help parents and professionals make the best clinical decisions for their children. In collaboration with colleagues at several research centers we are collecting epidemiologic, molecular genetic, and speech-language data on each of three putative etiological subtypes.
We suspect that the most prevalent cause of speech delay of currently unknown origin (accounting for perhaps 60% of clinical referrals) is genetic transmission of a linguistic processing deficit expressed as a problem in speech-sound production. Findings from several large family studies to date support this hypothesis. The goal in these ongoing molecular genetic projects is to identify the genotype associated with the genetically transmitted deficit and to understand its mode of transmission within families.
We believe that the second most prevalent cause of speech delay of unknown origin (accounting for perhaps 30% of clinical referrals) is fluctuant hearing loss, which may occur during episodes of middle ear disease (otitis media with effusion). Our recent work using structural equation modeling techniques suggests that speech effects are most closely tied to hearing loss associated with frequent middle ear disease occurring during the 12-18 month period of linguistic development.
Our findings indicate that among other possible subtypes of child speech disorder of currently unknown origin (accounting for the remaining approximate 10% of clinical referrals), the most prevalent subtype involves a genetically transmitted deficit in speech-motor control. Several ongoing collaborative genetic projects in apraxia of speech are developing the phenotype for this disorder, using perceptual and acoustic techniques to quantify affected children's and family members' speech and prosody.
Laffin, J. J. S., Raca, G., Jackson, C. A., Strand, E. A., Jakielski, K. J., & Shriberg, L.D. (in press). Novel candidate genes and regions for Childhood Apraxia of Speech (CAS) identified by array comparative genomic hybridization. Genetics in Medicine.
Raca, G., Baas, B. S., Kirmani, S., Laffin, J. J., Jackson, C. A., Strand, E. A., Jakielski, K. J., & Shriberg, L. D. (in press). Childhood Apraxia of Speech (CAS) in two patients with 16p11.2 microdeletion syndrome. European Journal of Human Genetics.
Rice, G. M., Raca, G., Jakielski, K. J., Laffin, J. J., Iyama-Kurtycz, C., Hartley, S. L. . . Shriberg, L. D. (2012). Phenotype of FOXP2 haploinsufficiency in a mother and son. American Journal of Medical Genetics: Part A, 158A, 174-181.
Shriberg, L. D., Lohmeier, H. L., Strand, E. A., & Jakielski, K. J. (2012). Encoding, memory, and transcoding deficits in Childhood Apraxia of Speech. Clinical Linguistics & Phonetics, 26, 445-482.
Shriberg, L. D., Paul, R., Black, L. M., & van Santen, J. P. (2011). The hypothesis of apraxia of speech in children with Autism Spectrum Disorder. Journal of Autism and Developmental Disorders, 41, 405-426.
Shriberg, L. D., Potter, N. L., & Strand, E. A. (2011). Prevalence and phenotype of childhood apraxia of speech in youth with galactosemia. Journal of Speech, Language, and Hearing Research, 54, 487-519.