Velopharyngeal closure is the sealing of the space between the soft palate (velum) and the pharyngeal walls. This process separates the oral cavity from the nasal cavity. It is important for directing air, sound, food, and liquids appropriately within the upper aerodigestive tract.
How the Velopharynx Works
The velopharyngeal mechanism is a muscular valve extending from the back of the hard palate to the posterior pharyngeal wall. It involves the coordinated movement of the soft palate, the lateral pharyngeal walls (sides of the throat), and the posterior pharyngeal wall (back wall of the throat). Several muscles contribute to this closure, including the levator veli palatini, the primary muscle for elevating the velum, and the musculus uvulae, which helps fill the gap between the velum and the posterior pharyngeal wall. The superior pharyngeal constrictor, palatopharyngeus, and palatoglossus muscles also constrict the pharynx and position the velum.
During speech, the velum elevates and moves backward to meet the pharyngeal walls, creating a tight seal. This closure directs airflow and sound into the oral cavity, which is necessary for producing most speech sounds in English. Only three sounds—/m/, /n/, and /ng/—are produced with an open velopharyngeal port, allowing air to exit through the nose. The timing and coordination of this closure are important for clear and understandable speech.
Beyond speech, velopharyngeal closure is also important during swallowing (deglutition). The velum rises and seals off the nasal cavity to prevent food and liquids from entering the nose. This ensures food and liquids are directed down the throat towards the esophagus and stomach, preventing nasal regurgitation. This reflex helps protect the airway during eating and drinking.
Challenges with Velopharyngeal Closure
When velopharyngeal closure is incomplete or impaired, it can lead to velopharyngeal dysfunction (VPD). This dysfunction can arise from various causes, including structural abnormalities like a cleft palate or submucous cleft palate, where the tissues of the roof of the mouth do not close correctly. Neurological conditions, such as stroke or cerebral palsy, can also cause impaired movement of the velopharyngeal structures. Surgical trauma, like that following an adenoidectomy, can affect closure.
The observable effects of impaired velopharyngeal closure primarily impact speech and swallowing. A common speech characteristic is hypernasality, where too much sound resonates in the nasal cavity, making speech sound nasal. This often occurs on vowels and voiced consonants. Another symptom is nasal emission, the audible release of air through the nose, particularly during the production of pressure consonants like /p/, /t/, /k/, /s/, /sh/, and /ch/. This leakage reduces the air pressure needed in the mouth for these sounds, making them weak or omitted.
Individuals may experience nasal regurgitation, where food or liquid comes out through the nose during swallowing. To compensate for air leakage during speech, individuals can develop compensatory speech behaviors. These involve producing sounds in alternative ways, often by using air pressure in the throat rather than the mouth, such as glottal stops or pharyngeal fricatives. While these behaviors aim to improve speech understanding, they can further affect overall speech clarity and naturalness.
Addressing Velopharyngeal Closure Issues
Identifying velopharyngeal closure problems begins with a perceptual speech evaluation conducted by a speech-language pathologist (SLP). This involves listening for characteristic speech patterns such as hypernasality, nasal emission, and weak consonants. To gain a more objective understanding of velopharyngeal function, instrumental assessments are used. These may include nasometry, which measures sound energy from the oral and nasal cavities, or videofluoroscopy, an X-ray technique that visualizes the movement of the velum and pharyngeal walls during speech and swallowing. Nasopharyngoscopy, which involves inserting a thin, flexible scope through the nose to directly observe the velopharyngeal sphincter, provides a detailed view of its movement.
Management approaches for velopharyngeal closure issues vary depending on the underlying cause and severity. Speech therapy plays a role, particularly in addressing compensatory articulation errors and improving speech clarity. Speech-language pathologists work with individuals to learn correct oral placements for sounds and reduce reliance on nasal airflow. While speech therapy cannot correct structural deficits, it can help individuals learn to use their velopharyngeal mechanism more effectively and reduce abnormal speech patterns.
Prosthetic devices can provide a non-surgical solution. Palatal obturators, also known as speech bulb prostheses, are custom-made dental appliances that extend into the pharynx to help close the gap between the soft palate and pharyngeal walls. These devices create a fixed surface against which the pharyngeal muscles can function, improving closure for speech and swallowing. When structural issues are present, surgical interventions are recommended. Procedures like pharyngoplasty aim to change the shape and function of the soft palate and pharynx to create a better seal. This can involve taking a flap of tissue from the back of the throat and attaching it to the palate (pharyngeal flap) or repositioning tissue from behind the tonsils to narrow the throat opening (sphincter pharyngoplasty).