Evaluating Velopharyngeal Dysfunction through Intraoral Pressure in NPC Patients: A Two-Year Follow-Up Study

Introduction: Nasopharyngeal carcinoma (NPC) is a distinct head and neck cancer originating in the nasopharynx, often treated with intensity-modulated radiotherapy (IMRT). While effective, IMRT can cause progressive structural and functional damage, particularly in the velopharyngeal area, leading to complications in speech and swallowing. Intraoral pressure measurement during speech has been used as a diagnostic tool to assess velopharyngeal dysfunction. This study investigates changes in intraoral pressure in NPC patients over a two-year follow-up period after IMRT.

Methods: A total of 41 NPC patients (32 males, 9 females, mean age 44.78 years) treated with IMRT at Kaohsiung Veterans General Hospital were followed. Patients underwent intraoral pressure assessments at six time points: pre-IMRT, and at 1, 3, 6, 12, and 24 months post-IMRT. Measurements included mean peak air pressure (MPP), expiratory airflow rate (MExAir), aerodynamic resistance (Res), and the Nasality Severity Index (NSI). A linear mixed-effects model was used to analyze longitudinal changes in MPP, with additional regression analysis to identify factors associated with intraoral pressure variations.

Results: Significant increases in MPP were observed over time, particularly after the first year post-IMRT (baseline MPP = 5.31 cm H2O, 2-year MPP = 7.32 cm H2O, p < 0.01). NSI scores dropped significantly, indicating a progression toward hypernasality (pre-IMRT NSI = 4.19; 2-year NSI = 0.17). MExAir remained relatively stable, suggesting increased respiratory effort to compensate for velopharyngeal inadequacy. Model analysis revealed significant associations between MPP and NSI, Res, and smoking status (p < 0.05).

Conclusions: Intraoral pressure changes post-IMRT are indicative of progressive velopharyngeal dysfunction, particularly in speech resonance. While respiratory compensatory mechanisms may maintain pressure, they fail to prevent hypernasality. These findings highlight the need for early screening and long-term management of velopharyngeal dysfunction in NPC patients post-IMRT to improve their quality of life.