In assessing speech for a child with suspected velopharyngeal dysfunction, which stimulus would be most helpful?

The most helpful stimulus in assessing speech for a child with suspected velopharyngeal dysfunction is high-pressure oral stops and fricatives. These sounds require the use of elevated oral pressure for articulation, which can reveal difficulties in the velopharyngeal mechanism's ability to properly close off the nasal cavity during speech.

When a normal velopharyngeal function exists, articulation of high-pressure sounds such as /p/, /b/, /t/, /d/, /k/, and fricatives like /s/ or /f/ is achievable without air escaping through the nose, which can result in nasal emission. Difficulty producing these sounds may indicate that the velopharyngeal valve is not functioning effectively, suggesting velopharyngeal dysfunction.

Other phonetic stimuli such as nasal phonemes, sustained vowels, or liquids and glides, while useful in various contexts, do not effectively challenge the velopharyngeal closure mechanism. Nasal phonemes inherently involve airflow through the nasal cavity, and sustained vowels may not provide enough pressure differentials to assess closure adequacy. Likewise, liquids and glides are less likely to provide clear indicators of velopharyngeal function since they do not require the same degree of oral pressure