To evaluate phenotypic expressions of speech sound disorder (SSD) in multigenerational families with evidence of familial forms of SSD.
Members of five multigenerational families (N = 36) produced rapid sequences of monosyllables and disyllables and tapped computer keys with repetitive and alternating movements.
Measures of repetitive and alternating motor speed were correlated within and between the two motor systems. Repetitive and alternating motor speeds increased in children and decreased in adults as a function of age. In two families with children who had severe speech deficits consistent with disrupted praxis, slowed alternating, but not repetitive, oral movements characterized most of the affected children and adults with a history of SSD, and slowed alternating hand movements were seen in some of the biologically related participants as well.
Results are consistent with a familial motor-based SSD subtype with incomplete penetrance, motivating new clinical questions about motor-based intervention not only in the oral but also the limb system.
Departments of Speech and Hearing Sciences (Dr Peter), Medicine (Dr Raskind), Psychiatry and Behavioral Sciences (Dr Raskind), University of Washington, Seattle.
Corresponding Author: Beate Peter, PhD, CCC-SLP, Department of Speech and Hearing Sciences, Box 354875, University of Washington, Seattle, WA 98195 (email@example.com).
The authors thank the families whose participation made this study possible. Many thanks to the following undergraduate and graduate students for their assistance with data collection and analysis: Leah Anderson, Lynn Bak, Yayin Chen, Erica Gonzales, Mariya Legesse, Amelie Lehmkühler, Jonathan Mahaffie, David Ramm, and Nancy Yuan. The software for the key tapping task was designed by Elias Peter. The authors are grateful to the following funding sources: NIDCD T32DC00033 (B. Peter), American Speech-Language-Hearing Foundation New Century Scholars Research Grant (B. Peter), and R01HD054562 (W. H. Raskind).