Although resonance disorders may be considered as a specialty area, any speech-language pathologist with a general practice, particularly those who are school-based, are likely to see these students on their caseloads. A basic knowledge of how to evaluate, how to treat, and when to refer to a specialist is important to ensure the best care for these children.
Resonance is the quality of the voice that is determined by the balance of sound vibration in the oral, nasal, and pharyngeal cavities during speech. Abnormal resonance can occur if there is obstruction in one of the cavities, causing hyponasality or cul-de-sac resonance, or if there is velopharyngeal dysfunction (VPD), causing hypernasality and/or nasal emission.
The velopharyngeal valve, consisting of the velum (soft palate) and pharyngeal walls, is critically important for speech because it directs the transmission of air pressure and sound energy into the oral cavity during the production of most sounds. Normal velopharyngeal function results in normal oral resonance, adequate intra-oral air pressure for consonant production, and sufficient breath support for normal utterance length.
VPD can be due to:
- Velopharyngeal insufficiency (VPI) is when there is an anatomical or structural defect, such as a short velum following cleft palate repair, a submucous cleft, or a deep pharynx secondary to cranial base anomalies.
- Velopharyngeal incompetence (VPI) is when there is a poor velopharyngeal movement due to a physiological cause. Velopharyngeal incompetence may be due to poor muscle function, pharyngeal hypotonia, velar paralysis or paresis, dysarthria, or even apraxia.
- Velopharyngeal mislearning is when there is hypernasality or nasal emission due to faulty articulation. This can occur due to pharyngeal or nasal articulation of certain sounds. Abnormal articulation can cause phoneme-specific nasal emission, usually on sibilant sounds.
- Velocardiofacial syndrome (VCFS) is a common cause of hypernasality in children who have no history of cleft palate. These children often have distinctive facial characteristics, including narrow eye slits, a bulbous nose, a long face, a thin upper lip, and a small jaw. They may have a history of minor cardiac anomalies and other medical problems. They often have developmental delay or learning problems. Children with VCFS are often unidentified until the school-based SLP makes a referral for abnormal resonance.
Resonance is best determined by listening to connected speech. Hypernasality is too much nasal resonance, particularly on vowels and voice oral consonants. Hyponasality is too little nasal resonance, primarily on nasal consonants (/m/, /n/, and /ng/). Cul-de-sac resonance is when the sound is trapped in the pharynx (due to large tonsils, for example) or in the nasal cavity (possibly due to a deviated septum or polyp). It is important to determine the type of resonance and whether there is nasal emission on pressure-sensitive sounds (plosives, fricatives, and affricates) in order to determine appropriate recommendations. It is not as important to determine the severity of the resonance disorder because this usually will not affect treatment.
A very simple test can be done to determine resonance using a straw, preferably a bending straw or a piece of tubing. The examiner should place one end of the straw at the entrance to the child's nose and the other end at the examiner's ear. The child is then asked to produce the following types of speech samples:
- Prolongation of single vowels
- Repetition of syllables with pressure-sensitive phonemes, and high and low vowels (papapapa; pipipipi; sasasasa; sisisisi; etc.)
- Prolongation of /s/
- Sentences that are loaded with pressure-sensitive phonemes (Sissy sees the sun in the sky. She went shopping. I eat cherries and cheese.)
- Counting from 60-70
- Repetition of nasal consonants (mamamama; nananana)
- Prolongation of /m/
If sound is heard through the straw on vowels sounds or voiced plosives, this indicates hypernasality. If air is heard loudly through the straw on oral consonants, this indicates nasal emission. If there is not much sound coming through the straw on nasal consonants, this may indicate hyponasality or cul-de-sac resonance.
Articulation should also be tested. When nasal emission is noted, it should be noted whether it occurs only on certain sounds or is consistent on most pressure sounds. If consonants are weak in intensity and pressure, this may be due to a loss of air pressure through the nose. The production of pharyngeal sounds should be noted because this placement may cause nasal emission. If there is a structural defect, or one that was repaired, there could be compensatory articulation productions which are usually pharyngeal or glottal sounds. Finally, utterance length should be tested if there is significant nasal emission. This can be done by having the child count to 20 and noting if he has to take a breath in the middle.
An intra-oral exam can be done to determine if there are large tonsils (which can cause hyponasality or cul-de-sac resonance) or a submucous cleft. Have the child stick out his tongue as far as possible and say "aaah" instead of "ahhh" so the tip of the uvula is visible without using a tongue blade. If there is a bifid or hypoplastic uvula, a bluish color in the velum, or if the velum appears like an inverted "V" during phonation, a submucous cleft should be suspected. Unfortunately, velopharyngeal function cannot be assessed through an oral exam because the velopharyngeal valve is behind the velum and cannot be viewed.
Speech treatment is rarely done for hypernasality or generalized nasal emission because these characteristics suggest a structural defect or physiological disorder which requires surgical management. When these characteristics are noted, a referral should be made to a regional craniofacial or cleft palate team (even if there is no history of cleft) for further assessment and management. On the other hand, hyponasality and cul-de-sac resonance suggest obstruction in the vocal tract. When this is noted, a referral can be made to the local otolaryngologist.
Although intervention does not correct abnormal structure, it does correct abnormal function. Treatment is appropriate for those children who demonstrate phoneme-specific nasality or nasal emission due to faulty articulation, and those children who use compensatory articulation productions due to a history of velopharyngeal dysfunction. In addition, intervention is often necessary after surgical management of velopharyngeal dysfunction to help the child to learn to make the best use of the new structures.
The treatment for these types of cases is done through standard articulation therapy. Blowing and sucking exercises should never be used to improve velopharyngeal function. They are not effective because the physiology of these activities is different than that for speech.
Several simple treatment techniques are usually effective. If there is nasal emission on sibilants only, have the child produce a /t/ sound with the teeth closed. Next, have the child prolong that sound. If the child has a normal velopharyngeal valve, this should result in a normal /s/ without nasal emission. This skill can then be transferred to the other sibilant sounds.
If the child co-articulates /ng/ for /l/ or /r/, or if the child has a high tongue position for vowels, it is often helpful to have the child co-articulate a yawn with the sounds. With a yawn, the back of the tongue goes down and the velum goes up.
If the child continues to demonstrate hypernasality or nasal emission after a few months of treatment, that child should be referred to a specialist for further assessment and consideration of physical management. No child should be kept in treatment and asked to perform a speech task that is physically impossible to do.
In summary, resonance disorders are commonly seen in pediatric settings, including the schools. A basic knowledge of this area is necessary for the SLP to know when to treat, how to treat, and when to refer.