HYPO-nasal speech is due to reduced or no nasal airflow and HYPER-nasal speech due to too much nasal airflow.
HYPO-nasal speech is by far the most common cause of nasal-sounding speech. It is similar to how a person would sound if they pinched their nose shut while talking. As such, ANY anatomic nasal obstruction would by definition lead to such hypo-nasal speech. Treatment, obviously, is to remove this anatomic nasal obstruction whatever it may be either with medications or surgery. Examples of hypo-nasal speech causes include:
- Adenoid Hypertrophy (Very Common)
- Turbinate Hypertrophy (Common)
- Significant Deviated Septum (Uncommon)
- Nasal Polyps (Uncommon)
- Allergies (Common)
- Infection (upper respiratory illness and/or bacterial infections) (Common)
- Rarely, genetic conditions like cystic fibrosis and immotile ciliary syndrome
- Rarely, anatomic conditions such as choanal atresia
- Rarely, a sino-nasal tumor
HYPER-nasal speech itself has several different flavors, but the key concept is the presence of an opening between the mouth and nose when it should be sealed shut during speech. Normally, complete closure should occur with certain sounds like /s/, /sh/, /b/, and /p/. Such sounds are called plosives and sibilants. This link provides a cartoon animation of how each sound in the English language is produced from an anatomical standpoint.
Now what are some of the causes of HYPER-nasal speech? Causes can be divided broadly into either anatomic and functional variants.
Anatomic HYPER-nasal speech include:
- Cleft Palate
- Palate Fistula
- Submucus Cleft
Functional HYPER-nasal speech include:
- Velopharyngeal insufficiency without anatomic cause. Velopharyngeal insufficiency or VPI occurs when the soft palate does not seal against the back of the mouth during appropriate speech sounds.
- Poor articulation (person is not correctly pronouncing words)