Catching the Wave: Investigating Posterior Pharyngeal Wall Movement in Healthy Adults.

Purpose: Serial contraction of the pharyngeal constrictor muscles, seen as a wave of posterior pharyngeal wall (PPW) movement, helps to sweep a bolus downwards through the pharynx. We aimed to characterize the timing of maximum PPW thickness (i.e. anterior excursion) at three anatomical levels during swallowing while considering the effects of sex, age, and bolus consistency. Methods: Data were extracted from videofluoroscopies collected at 30 frames per second using 20% w/v barium in 76 healthy adults (37 males, 39 females), distributed evenly across four age groups: 18–35, 36–53, 54–72, 73–90 years. We analyzed 150 video clips: each participant's first cup sip of thin liquid and first teaspoon of mildly thick liquid. After training and achieving good inter- and intra-rater reliability (ICCs ≥ 0.76), a single rater measured PPW thickness on every frame between the bolus passing mandible [BPM] and swallow rest [SR] frames. PPW measures were taken level with the anterior-inferior corners of the C2, C3, and C4 vertebrae. All ratings were reviewed by a second rater, and discrepancies were resolved by consensus. The timing of maximum PPW excursion at each level (C2max, C3max, C4max) was normalized to the interval from upper esophageal sphincter opening (UESO) to closing (UESC). Descriptive statistics and analyses of variance (ANOVA) were used to evaluate the effects of sex and age on maximum PPW excursion timing at each level. Results: A descending sequence of PPW excursion was observed in all cases, beginning at the C2 level and progressing through C3 to C4. On average, C2max occurred 82-88% of the way into the UESO-UESC interval. C3max followed at the 100% timepoint (i.e., at UESC), with C4max trailing at 127-130% (i.e., after UESC). No significant differences were found across bolus consistency. For C2max, there was a significant interaction between age category and sex, with earlier timing observed in younger women. For C3max and C4max, males showed significantly earlier timing. The C3max sex difference was absent in the oldest age group. Conclusions: Age and sex influence the timing of maximum PPW excursion during swallowing. Future studies should explore other factors, such as bolus size, height, neck length, and UES location, and their impact on PPW timing and amplitude.