Speech changes after maxillary advancement in 40 cleft lip and palate patients

In this study, we retrospectively investigated speech intelligibility changes in 40 patients at the Australian Cranio-Facial Unit who underwent Le Fort I maxillary advancement between 1978 and 1995. Resonance, articulation, and velopharyngeal sphincteric function, which were assessed before and after surgery, were analyzed in conjunction with details of the surgery in an attempt to identify the factors affecting speech intelligibility. Of the 40 patients, 10 experienced improved speech (improved intelligibility group), 18 demonstrated no detectable changes in speech (unchanged intelligibility group), and 12 presented with worsened speech intelligibility (deteriorated intelligibility group). The average amount of advancement was 9.4 mm in the improved and unchanged intelligibility groups and 12.2 mm in the deteriorated intelligibility group. There was a statistically significant difference in the average amount of advancement between the improved and unchanged groups and the deteriorated intelligibility group. In the improved intelligibility group, 9 patients demonstrated improved articulation and 7 had reduced hyponasality. Conversely, in the deteriorated intelligibility group, 10 patients demonstrated increased hypernasality. Intelligibility ratings appeared to depend on the balance between the benefits of amelioration of hyponasality and misarticulations and the debit of increased hypernasality. The amount of maxillary advancement has a direct bearing on speech intelligibility. The amelioration of speech intelligibility improves if the amelioration of distorted articulation and hyponasality overrides any increase in hypernasality.