A Comparison of Nasality Measures between Children with Childhood Apraxia of Speech, Children with Repaired Cleft Palate, and Typically Developing Children

Abstract:

Nasalance is the ratio of acoustic energy output from the oral and nasal cavities of a speaker. Previous research noted abnormal resonance in children with childhood apraxia of speech (CAS). Although this characteristic has often been observed, little research has focused specifically on resonance.

The purpose of this study was to examine the velar function of children with CAS, compared to children with repaired cleft palate (RCP) and typically developing children (TD). Children with RCP are at higher risk for hypernasal resonance due to structural differences. Acoustic nasalance measures and perceptual measures were made.

Results indicated children with CAS spoke with slightly more nasality than typically developing peers, and with less nasality than children with RCP. In addition, children in the CAS and RCP groups had much greater ranges in nasalance scores and perceptual scores of nasality than their TD peers.

Rationale/Background:

Previous research noted abnormal resonance in some children with CAS (Ball, Beukelman, & Bernthal, 1999; Hall, Hardy, and La Velle, 1990; Skinder, 2000; Weiss, Gordon, & Lillywhite, 1987). Given that CAS is a disorder where the child has difficulty planning the sequence of movements required for speech (Rosenbek & Wetz, 1972) and difficulty with spatio-temporal coordination (Velleman, 2003), researchers speculated that some children with CAS may have difficulty planning movements of the velum, just as they do with other articulators (Hall, Hardy, and La Velle, 1990; Weiss, Gordon, & Lillywhite, 1987).

In a previous study, Skinder-Meredith found eight of 10 children with CAS were judged to have hypernasal resonance (Skinder, 2000). More specifically, given a rating from one to five, where one represented "hypernasality is never present" and five represented "hypernasality is always present," the eight children judged as hypernasal had an average rating of 3.27 with a standard deviation of 1.1, indicating that hypernasality was sometimes present. In addition, listeners rated how often they heard hyponasality. Two of the three listeners judged only one child as having some hyponasality present. Difficulty in timing and or sequencing the velar movement correctly could result in inconsistent resonance errors and account for the most noted perception of "sometimes hypernasal". Hall and colleagues (1990) stated some children with CAS continue to be perceived as hypernasal, even as their speech skills improve.

On occasion, a child with CAS may have such severe velopharyngeal insufficiency that prosthetic intervention may be warranted. For example, Hall and colleagues (1990) treated one girl with a palatal lift after finding that behavioral therapy alone was not enough to improve intelligibility. Although the girl was able to raise her palate in some situations she was not able to do so in a timely and consistent manner for functional speech. The palatal lift allowed increased success with intelligibility. Weiss and colleagues (1987) noted a child with CAS that had severe intermittent velopharyngeal closure. They gave her the diagnosis of "velar dyspraxia".

To further investigate nasality in children with CAS, this study compared nasalance measures and perceptual measurements of nasality of children with CAS to children with repaired cleft palate (RCP) and typically developing children (TD). Nasalance is the ratio of acoustic energy output from the oral and nasal cavities of a speaker. Instrumental measures of nasality can be helpful because listeners often have difficulty discerning between hyponasality and hypernasality (Boone & McFarlane, 2000).

The Kay Elemetrics' Nasometer II Model 6400 can be used to acoustically and numerically measure nasalance. The Nasometer II is a computer based device that "provides objective measures of nasality by deriving a ratio of acoustic energy output from the oral and nasal cavities of a speaker." (Anderson, 1996, p.333). The Nasometer II includes headgear with a horizontal divider between the nose and mouth, which is attached to a computer.

When comparing perceptual and acoustic nasalance measures between the three populations (CAS, TD and RCP) it was predicted that children with CAS would have greater disordered nasal resonance than TD children, but less disordered nasal resonance than children with repaired cleft palate.