Clinical application of usage-based phonology: treatment of cleft palate speech using usage-based electropalotography

Purpose: To investigate whether a novel electropalatography (EPG) therapy, underpinned by usage-based phonology theory, can improve the accuracy of target speech sounds for school-aged children and adults with persistent speech sound disorder (SSD) secondary to cleft palate +/− lip. Method: Six consecutively treated participants (7–27 years) with long-standing speech disorders associated with cleft palate enrolled in a multiple baseline (ABA) within-participant case series. The usage-based EPG therapy technique involved high-volume production of words. Speech was assessed on three baselines prior to therapy, during weekly therapy, at completion of therapy, and 3 months post-therapy. Percent correct of target phonemes in untreated words and continuously connected speech were assessed through acoustic phonetic transcription. Intra- and inter-transcriber agreement was determined. Result: Large to medium treatment effect sizes were shown for all participants following therapy (15–33 sessions). Percentage of targets correct for untreated words improved from near 0% pre-therapy, to near 100% for most target sounds post-therapy. Generalisation of target sounds to spontaneous connected speech occurred for all participants and ranged from 78.95−100% (M = 90.66; SD = 10.14) 3 months post-therapy. Conclusion: Clinically significant speech change occurred for all participants following therapy. Response to the novel therapeutic technique is encouraging and further research is indicated.