Voice Therapy in Patients with Cleft Lip and Palate: A Narrative Review

Cleft lip and palate (CLP), as one of the most common congenital anomalies in children, can result in voice disorders. Incidence of CLP and its consequential impact may lead to laryngeal pathologies of the vocal cords, and symptoms may include hoarseness, harshness, breathiness, decreased loudness, and abnormal pitch. Considering the limited number of findings on the efficacy of voice therapy in patients with CLP, the purpose of this narrative review is to aggregate the results of previous studies, explore their findings and restrictions, and identify gaps to present more appropriate data regarding the efficacy of voice therapy in patients with CLP.

A literature review was conducted independently by both authors across several electronic databases, including PubMed and Google Scholar. Based on the authors' criteria, studies focusing exclusively on surgical procedures, resonance therapy, or articulation therapy, review articles, conference abstracts, articles without full text, and non-English articles were excluded. Studies evaluating the outcomes of voice therapy in patients with CLP were selected for a qualitative synthesis.

Only four studies met the inclusion criteria, investigating diverse therapeutic techniques including eclectic, symptomatic (vocal fry), and physiologic approaches (straw phonation and VentiMask). Generally, regardless of the voice therapy techniques used, there was a significant improvement across different aspects of voice assessment, including reduced hoarseness and hypernasality, improved velopharyngeal closure, reduced jitter and shimmer, and increased Harmonics-to-Noise Ratio (HNR) and Cepstral Peak Prominence (CPP). Moreover, VentiMask yielded clinically meaningful, stable improvements in health-related quality of life (HRQoL).

Voice therapy can be a beneficial and essential component in the multidisciplinary management of CLP by mitigating secondary vocal symptoms, improving acoustic characteristics, and improving quality of life in these patients. However, the effects of methodological diversity, small sample sizes, participants' heterogeneity, and differences in techniques should not be underestimated, as they can affect the interpretation of findings. Therefore, future research should employ rigorous designs, such as randomized controlled trials with larger sample sizes and long-term follow-up, to establish standardized clinical protocols and facilitate better interpretation of results.