What causes it
Unintelligible speech may be due to an undetected hearing loss or disorders of language, articulation, voice and resonance.
Early detection and treatment of these problems is needed for optimal speech outcomes.
A resonance problem, in particular, is easily missed and there is a lack of awareness among the public that this can be helped.
Resonance disorders include hypernasal speech, hyponasal speech or a combination of both.
Hypernasality & Hyponasality can result in unintelligible speech
A glass that is half full when hit with a spoon sounds different from that of a glass three quarters full. The resonance is different.
Resonance problems can cause speech unintelligibility by abnormally decreasing or increasing the space within which sound vibrates during speech.
Hyponasal speech sounds like that when one is having a blocked nose due to a cold. Hypernasal speech sounds like that of a person talking through the nose, where an abnormal air leak accompanies non-nasal sounds.
Causes of hypernasality
Hypernasality is commonly associated with children who have a cleft palate.
However, many children and adults with poor oro-facial muscle tone, craniofacial disproportions and short, scarred or undetected hard palate defects may have velopharyngeal insufficiency or incompetence (VPI) that results in hypernasality and reduced speech intelligibility.
This may be due to an inability of the soft palate to close off the nose for non-nasal sounds such as /s/, /z/, /k/, /g/.
Children, for example, with a global developmental delay or subtle neurological weakness often have difficulty closing the velopharynx area completely due to weak muscles in the soft palate.
VPI is also sometimes due to very large tonsils, or may be revealed after adenoid surgery. VPI needs a formal examination to be diagnosed, and speech therapy alone may not be able to correct it.
About the condition
Do teachers or friends complain that your speech or your child’s speech is difficult to understand?
Unintelligible speech is often mistakenly attributed to low intelligence or lack of environmental stimulation, and the child may be labelled as “slow”.
It is often thought that the longer the tongue, the better the speech clarity; however, only severe tongue-tie causes poor articulation.
Diagnosis and Treatment Options
After a general ENT examination to exclude hearing loss, mouth, tongue and voice problems, a small flexible scope is passed through the nose to visualise the movement of the soft palate during speech. This assessment helps the doctor to determine whether there is a velopharyngeal gap, and accurately identify the level, side and site of any weakness or insufficiency of the soft palate. This assessment is done together with the speech therapist at the ENT clinic. Soft palate movement is observed while the patient says specific sentences, words and sounds.
Specialised voice clinic (videostroboscopy)
Voice rehabilitation for laryngectomy
Velopharyngeal insufficiency speech therapy
A voice assessment will evaluate both structure and function of the voice. It will include a voice history, visual imaging (e.g. laryngeal mirror, nasendoscopy, videostroboscopy), perceptual judgements of voice quality, acoustic measures such as pitch and intensity, and aerodynamic measures e.g. airflow rate and postural evaluations. The ENT surgeon / laryngologist will work together with the speech therapist to gather all this information and formulate a diagnosis.
Specialised voice clinics provide videostroboscopic voice assessments; videostroboscopy provides a slow motion view of the vocal folds. It reveals aspects of anatomy and function that may not be visible with other imaging techniques. For example, mild swelling on the vocal cords may not be seen in a static examination but will manifest as stiffness with loss of the mucosal wave during videostroboscopy
Voice therapy includes advice and counselling for poor vocal habits and voice misuse, vocal warm up exercises, voice techniques and work on voice projection and modulation.
Many patients benefit from speech therapy and may never need surgery. However some may need surgery to correct the problem. The patient usually stays one night in hospital after the minor surgical procedure, and is able to eat and drink post surgery. It is important to continue speech therapy after surgery to maximise speech outcomes.