The velum or soft palate is the soft tissue constituting the back of the roof of the mouth. During non-speech tasks such as swallowing, blowing, sucking and whistling the velum elevates and retracts to separate the nasal cavity from the oral cavity. Improper closure of the velopharyngeal sphincter can lead to difficulty with bottle feeding because proper intra oral pressure is necessary to achieve an adequate suck, swallow, breathing pattern. If the nasal cavity is not properly sealed via velophayrngeal closure choking or coughing can occur due to liquids or solids entering the nasal and pharyngeal cavities causing nasal regurgitation. During speech tasks the velum also elevates and retracts to separate the oral cavity (mouth) from the nasal cavity to produce consonants including /p, b, t, d, k, g, s, z, ch, zh, sh, r, l/ and remains open for nasal sounds /m,n,ng/. If there is improper closure of the velopharyngeal port, air escapes through the nose leading to “nasal” speech sounds. Complete velopharyngeal sufficiency (velopharyngeal competency) occurs when the velum occludes the velopharyngeal port which separates the oral cavity (mouth) and nasal cavity in a proper and timely manner.
There are a variety of disorders of the velum including:
Velopharyngeal Insufficiency (VPI) is caused by anatomical defects such as a cleft palate or submucous cleft (overt or occult), short velum or deep pharynx, irregular adenoids and enlarged tonsils.
Velopharyngeal Incompetence (VPI) is caused by physiological defects such as reduced muscle function secondary to a history of a cleft lip or palate, submucous clefts, pharyngeal hypotonia, velar paralysis or paresis due to brain stem or cranial nerve injury, neuromuscular disorders including Myasthenia Gravis, Dysarthria or Apraxia due to congenital or acquired neurological impairments.
Velopharyngeal Mislearning is abnormal nasal articulation as a result of inadequate velopharyngeal closure on certain sounds that can be phoneme specific and is a learned misarticulation.
Hypernasality occurs when there is too much sound vibrating in the nasal cavity causing speech to have a nasal quality.
Hyponasality occurs due to limited nasal airflow during the production of nasal sounds /m,n,ng/ that often results in a sound with a perceptual quality of having “a cold”. This can be the result of obstruction when there is nasal congestion, enlarged adenoids and a deviated septum.
Therapy is effective and appropriate if the individual demonstrates the following:
- Hypernasality or variable resonance due to apraxia
- Compensatory articulation productions secondary to VPI that cause nasal emission
- Misarticulations that cause nasal air emission that are phoneme-specific
- Hypernasality or nasal emission following surgical correction.