Velopharyngeal relationships of /i/ and /s/ as seen cephalometrically for persons with suspected incompetence

Measurements of velopharyngeal gaps were obtained for 110 subjects with suspected velopharyngeal incompetence. Cephalometric x rays during a high vowel, /i/, and a sustained voiceless sibilant, /s/, were compared. Velopharyngeal gaps for the two phonemes differed in group means and for most individual subjects, with greater gaps being found for /i/ than for /s/. Persons with smaller gaps generally were found to have /i/ gaps in the absence of /s/ gaps, and greater /i-s/ discrepancy. Relationships between velum and pharyngeal wall perceived cephalometrically during /i/ and /s/ were not found to be equivalent. Generally, the /i/ radiograph agreed better with presumed velopharyngeal incompetence.