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ABSTRACT:
This tutorial addresses the complex pathophysiology; various structural and neurologic causes; methods of clinical appraisal; and alternative behavioral, prosthetic, and medicosurgical treatments of velopharyngeal dysfunction. To balance the primary focus of this review on hypernasal resonance and articulation disorders, discussions concerning hyponasal speech characteristics and underlying etiologies are also rendered.
KEY WORDS: velopharyngeal, hypernasality, hyponasality, cleft palate, dysarthria
Although children employ numerous techniques to express language, speech production may be considered the predominant form. There are five speech subsystems: (a) respiration, (b) phonation, (c) articulation, (d) resonation, and (e) prosody. This overview examines the pathophysiologic interrelationships between all of these components, with primary focus on the sequelae of various resonation subunit disturbances.
ANATOMY AND PHYSIOLOGY OF NORMAL SPEECH RESONANCE BALANCE
Resonators
Sound waves generated by activity of the vocal folds propagate upstream and are intensified and enriched through supplementary vibrations of three primary head and neck resonating chambers: (a) pharynx, (b) oral cavity, and (c) nasal cavity (see Figure 1). These structures compose the vocal tract. The vocal tract is constrained, both anatomically and physiologically, to function in a coordinated manner with the respiration subsystem, which supplies a fairly constant energy source required for the production of all speech sounds. The soft palate (velum) and pharynx differentially function as a muscular sphincter during sucking, swallowing, and speech. That is, upon contraction, the velum elevates and retracts against the stationary posterior pharyngeal wall, and the lateral pharyngeal walls merge medially to compress the displaced velum to achieve a tight seal. In the English language, only the /m/, /n/, and /ng/ consonants are normally articulated with associated nasal airflow and resonation (nasality) because during their production, the velopharyngeal (VP) valve remains open. The remaining consonants and all of the vowels are
considered oral phonemes because during their production, airflow and sound energy resonate within the oral cavity owing to closure of the VP valve. Figure 2 is a flexible endoscopie superior view of the VP valve at rest and during repetitions of the consonant-vowel /pi/. Note that in this normal speaker, full closure is achieved (quadrant 4), preventing upstream airflow and sound energy leakage into the nasal cavity. When a speaker is perceived to exhibit distracting and persistent hypernasal resonation, this abnormality is the result...