The quality of the patient's speech is the best criterion of the success of treatment of cleft palate. To obtain perfect speech in the majority of cases one has to correct not only the escape of air nasally but also defects of articulation. The soft palate is part of a muscular mechanism the function of which is to separate the oral cavity from the nasopharyngeal cavity during swallowing and during speech. This closure must be complete for correct articulation of every sound in the English language except the three nasal consonants M, N and NG. For the articulation of these consonants the air escapes through the nose, and the resonance is essentially nasal. It is apparent, therefore, that the palatopharyngeal sphincter not only must be capable of perfect closure but must also be capable of very rapid movement.
REQUIREMENTS FOR SUCCESS IN TREATMENT OF CLEFT PALATE
SCHARFE EE. VALUE OF SPEECH TRAINING IN CASES OF CLEFT PALATE AND OTHER ORAL CONDITIONS. Arch Otolaryngol. 1935;22(5):585-596. doi:10.1001/archotol.1935.00640030602005