Treatment of velopharyngeal closure for speech: Discussion and implications for management.

Abstract

Abstract The velopharyngeal closure mechanism acts as a valve to separate the oral and nasal cavities during speech and swallowing. Velopharyngeal closure deficits are generally identified by the speech-language pathologist and corrected through surgery or speech prosthetics. However, there is a small subset of clients who may benefit from treatments using task specific muscle rehabilitation procedures. This review article addresses the following topics: structure/function relationships of velopharyngeal closure, motor programming of velopharyngeal closure, aims and findings of various types of muscle treatment programs, discussion and rationale of successful muscle treatments, and guidelines for utilizing muscle treatment for the management of clients with velopharyngeal closure deficits. Keywords: Velopharyngeal closure, muscle treatment, nasal emission, hypernasality. Introduction Velopharyngeal closure is the neurophysiologic act of partitioning the oral cavity from the nasal cavity during speech and nonspeech activities. Thompson and Hixon (1979) characterize the velopharyngeal closure mechanism as a valve whose actions act to separate the oral and nasal cavities. Moon and Kuehn (1996) describe the mechanism for speech as an articulator that must operate according to rules of neuromotor programming, and whose activity must be synchronized with the actions of other articulators to attain perceptually acceptable speech. McWilliams, Morris, and Shelton (1984, 1990) indicate that velopharyngeal closure for speech consists of velar movement and contact with the lateral and posterior pharyngeal walls. The velum moves in an upward and backward direction to articulate with the pharyngeal walls. Normal speakers exhibit differential patterns of muscle activity of the velum, lateral pharyngeal walls and posterior pharyngeal wall (Iglesias, Kuehn, & Morris, 1980; Shprintzen, Lencione, McCall & Skolnick, 1974; Zwitman, Sonderman, & Ward, 1974). That is, they achieve closure but the articulators contribute in different ways depending on the speaker. Velopharyngeal closure for speech allows a speaker to generate sufficient air pressure and flow for the production of pressure consonants and also permits the production of voiced sounds without hypernasal resonance. Speakers who are unable to achieve velopharyngeal closure or who exhibit faulty timing of closure often demonstrate problems with speech production and such problems manifest in articulation and resonance disorders (Kuehn, 1979; Morris, 1992; Warren, Dalston, & Mayo, 1993). Articulation problems are normally found with the plosive, fricative and affricate sound categories, since they require the generation of high intraoral air pressure (McWilliams et al., 1990; Peterson-Falzone, Hardin-Jones,& Karnell, 2001; Shelton, Hahn, & Morris, 1968; Shelton, Morris, & McWilliams, 1973). These pressure sounds, may be produced with nasal emission, or the client may use compensatory substitutions in place of the pressure sounds. Audible nasal emission is the auditory perception or air passing through the nose during the production of a pressure sound. The speaker may produce the sound at the correct point of articulation, but nasal emission accompanies the production. Compensatory errors are sounds that are used in place of pressure sounds and generally produced at a more posterior point of articulation than the intended sound. For instance, one of the most frequent compensatory errors utilized by speakers with cleft palate is the glottal stop. It is produced by bringing the vocal folds together to create a complete constriction and then releasing the built-up air pressure created by the lungs. Resonance is the product of the transfer function of the laryngeal sound source (Peterson-Falzone et al., 2006). The vocal tract acts as a filter to selectively modify in different ways the complex laryngeal tone that is created by the vibration of the vocal folds. …