Velopharyngeal dysfunction: The need for a team approachAugust 13, 2020
A significant proportion of individuals with cleft lip — varying between 7% and 26% or even higher — present with the condition of velopharyngeal dysfunction (VPD), even after a surgical repair of the palate.
VPD refers to the condition where the velopharyngeal port does not function appropriately during speech, resulting in a coupling of the oral and nasal cavities.
This oronasal coupling contributes to a range of speech difficulties, including hypernasality (increased nasal resonance of oral sounds), nasal air emissions during the production of oral sounds, inadequate intraoral breath pressure for speaking and even errors in articulating speech sounds. The sounds that require complex manipulation of intraoral breath pressure for speaking are the ones most vulnerable to errors of articulation. These are the oral pressure consonants and include speech sounds such as the stop consonants [p,b,t,d,k,g]; fricatives [s,z,sh]; and affricates [ch,j]. The cumulative effect of these errors is that the understandability of speech is compromised and listeners have difficulty in accepting the speech.
The nature of VPD is such that a multidisciplinary team approach is required for its assessment and management. The team essentially should comprise a plastic or maxillofacial surgeon and the speech language pathologist. Team care in cleft lip and palate has been evolving in India over the last decade. Despite having centres with established team care, the numbers are few across the country. The absence of established teams across several centres in India poses a challenge for effective management of VPD.
Perceptual evaluation of speech
The assessment of VPD involves a two-pronged approach consisting of a clinical perceptual evaluation of speech by a trained speech language pathologist, and the visualisation of the movements of the soft palate and pharyngeal walls during speech. The clinical perceptual evaluation includes a visual examination of the oral structures and auditory perceptual analysis of the elicited speech by a trained ear. While the clinical perceptual evaluation guides a speech language pathologist to suspect VPD, the diagnosis can be confirmed only after visualisation of the velopharyngeal ports through procedures such as nasoendoscopy and multiview videofluoroscopy.
During perceptual evaluation, a comprehensive speech stimulus, comprising general conversation, rote speech (counting numbers or telling the names of days in a week or months in a year), repetition of pressure consonant loaded words and sentences, should be elicited in the primary language of the patient or the language he/she is most comfortable with. Guidelines specifying the nature of speech samples are available according to the universal parameters of reporting speech outcomes in individuals with cleft (Henningsson et al., 2008) and can also be modified to comply with the sound structure and rules of different language families. These guidelines are to ensure that the elicited speech sample includes all the effective pressure consonants of the language and extends across varying linguistic complexities such as words, sentences, and longer connected speech. Controlled speech stimulus has been developed based on these guidelines in Indian languages, including Hindi, Tamil, Kannada, Telugu, Malayalam and Marathi. Lack of standardised speech materials across other Indian languages and dialects compromises the quality of perceptual speech assessment and poses a challenge while assessing speech in those languages.
The speech language pathologist performs structured listening by focussing on specific parts of the comprehensive speech stimuli to rate specific components of speech, including resonance (to determine if the speech is hypernasal), nasal air emission and errors of consonant production to suspect the presence of VPD. For instance, resonance is rated based on repetition of sentences, nasal air emission is rated based on repetition of syllables, etc. The process of structured listening is mastered through training and periodic listening to cleft speech samples, almost similar to the process of calibrating one’s own ears to identify and rate cleft speech. This calibration and periodic listening are essential in order to ensure that the ratings provided by the speech language pathologist are reliable. In the past, there were also challenges posed due to different protocols used for perceptual assessment. However, most centres across India and South Asia use the universal parameters for reporting speech outcomes in individuals with cleft (Henningsson et al., 2008), owing to which it is easy to interpret findings of a perceptual speech assessment.
Following perceptual assessment of speech, when there is a suspicion of VPD, it is essential to perform either nasoendoscopy or lateral videofluoroscopy to visualise the movements of the velopharyngeal
port during speech to confirm the diagnosis of VPD. This is usually performed by the team, including the surgeon and the speech language pathologist. Both the procedures allow the team to visualise the movement of the velopharyngeal structures and check for the nature of velopharyngeal closure. It helps the team to assess if there is a velopharyngeal gap/defect and also describe the size and nature of deficit. It is essential to engage the patient in an appropriate speech task while performing these procedures.
While it may be ideal to perform both nasoendoscopy and lateral videofluoroscopy, it is imperative to perform either one of the two procedures to confirm the diagnosis of velopharyngeal dysfunction. The choice between the two procedures is determined based on the availability of equipment and the training and preference of the team.
Nasoendoscopy involves inserting a flexible fibreoptic nasoendoscope transnasally and visualising the functioning of the velopharyngeal port with a bird’s eye-view. This is a minimally invasive procedure and requires more compliance from the patient compared to videofluoroscopy. This also involves use of a local anaesthetic spray to numb the nasal cavity to facilitate insertion of the scope. However, this is very useful to determine even the presence of small velopharyngeal openings.
Videofluoroscopy, on the other hand, is an imaging technique that provides real-time moving images of the velopharyngeal port. This procedure involves the risk of exposure to radiation, owing to which the procedure should be performed quickly with minimal relevant speech stimuli. For a complete assessment of the three-dimensional velopharyngeal port, one has to perform assessments using multiple views. However, the lateral view videofluoroscopy alone is often sufficient to provide relevant information for individuals with cleft. A lateral view videofluoroscopy provides information regarding the movement of velum towards the posterior pharyngeal wall and allows one to visualise the entire length of the posterior pharyngeal wall. One of the major advantages of lateral view videofluoroscopy over nasoendoscopy is that it helps to estimate the point at which the velum makes contact with the posterior pharyngeal wall. It also helps to measure and quantify the size and the extent of the velopharyngeal gap. Figure 1 and 2 represent the image of nasoendoscopy and lateral view videofluoroscopy representing normal velopharyngeal functioning.
Both nasoendoscopy and videofluoroscopy are procedures involving expensive instrumentation. Further the team members require specialised training to administer the procedures appropriately and extract clinically relevant information to facilitate the decision- making process. The use of appropriate speech stimuli is essential for both the procedures to be meaningful. When the visualisation procedures indicate the presence of a velopharyngeal gap, the diagnosis of velopharyngeal dysfunction is confirmed, and this warrants the need for secondary surgical intervention to correct the VPD. Following structural correction of VPD, speech therapy is recommended to correct the residual speech defects and help them utilise the structure for speech.
In short, poor speech may be the consequence of a cleft palate repair and could be a serious impediment in the all-round progress of the child. It is therefore very important to involve the appropriate specialists and skills to diagnose a poorly functioning velopharynx after cleft palate repair so that necessary interventions could be carried out. Assessing the speech as we hear it albeit, by a trained ear and objective instrumental assessment viz nasoendoscopy and or videofluoroscopy will help in clinching the diagnosis of VPD.
The velopharyngeal port is dynamic and comprises the soft palate, and the lateral and posterior pharyngeal walls. The movement of soft palate in the superior posterior direction towards the posterior pharyngeal wall, and the medial movements of the lateral pharyngeal walls are the major contributors of velopharyngeal functioning. Irrespective of the patterns of movement, a complete closure of the velopharyngeal port is required for effective speech.
Factors such as short soft palate and a disparity between the palatal length and depth of pharyngeal cavity in individuals with repaired clefts contribute to velopharyngeal dysfunction. In instances where cleft lip and palate presents itself as a syndromic manifestation, muscle weakness can also contribute to velopharyngeal dysfunction. Sometimes, in the absence of any anatomical or physiological reasons, abnormal speech learning patterns of an individual can contribute to velopharyngeal dysfunction, commonly referred as velopharyngeal mislearning. In the later condition, functioning of velopharyngeal port is found to be inconsistent across speech sounds.
Dr Krishnamurthy Bonanthaya, Maxillofacial Surgeon, Bhagwan Mahaveer Jain Hospital, Bangalore.
Dr Savitha V H, Ph D, Consultant Speech Language Pathologist, Audiologist.Both are members of Medical Advisory Council for Smile Train India