Differences Between Flexible and Rigid Endoscopy in Assessing the Posterior Glottic Chink

Abstract

To determine whether different modalities of laryngeal examination produce differences in the assessment of the posterior glottic chink (PGC), and whether the prevalence of PGC differs by gender. The PGC has been described as a triangular laryngeal space between the posterior laryngeal wall and the vocal processes during glottic closure found commonly in human females, but less often in males. The purpose of this study was not only to identify whether there are gender differences in prevalence of posterior glottic but also to determine whether there is a difference in detection of this configuration dependent on the modality of laryngeal imaging, specifically flexible nasopharyngolaryngoscopy (FNPL) versus rigid laryngoscopy (RL). A review of 104 consecutive initial laryngeal examinations was performed. All patients underwent both flexible laryngoscopy (FL) and RL performed under stroboscopic light. Patients with immobile vocal folds, masses causing glottic gaps, atrophy, or severe muscle tension dysphonia causing an inability to fully visualize the entire length of the vocal fold were excluded. In the remaining patients, the posterior glottic configuration showing a posterior chink in relation to the vocal process was graded on a 0-4 scale (called the Posterior Glottic Closure Score [PGCS]); 0 was used to indicate a closed glottis and 4 the most open configuration without creating a complete glottic gap. PGCSs for males were compared with those of females, and the PGCSs obtained by flexible nasopharyngolaryngoscopy was compared with RL. Fifty-two patients were included in the study. Twenty-four of the patients were male, and 28 were female. The average age of the patients was 48.4 years (SD±17.35), and the range was 15-81 years. On RL, eight males had a PGCS 1-4, that is, evidence of PGC, and 23 females had a PGCS 1-4. On flexible nasopharyngolaryngoscopy, only four males had a PGCS 1-4 and 24 females had PGCS 1-4. Twenty-two females had a PGC detected by both modalities, and the PGCS was significantly higher using RL (2.73±0.70 vs. 2.14±0.834) than FL. For the four males in which PGC was detected by both modalities, there was no statistical significance when comparing the PGCS between RL and FL (1.75±0.96 vs. 1.75±0.5, P<0.05). When comparing only males and females who had a PGC (PGCS 1-4), females had a higher PGCS (2.65±0.78) than males (1.75±0.71, P<0.05) on RL, indicating a more open posterior glottis in females. On flexible examination, there was no difference detected in the average PGCS, 2.08±0.83 for females and males 1.75±0.50. PGCs were more common in younger (age 43 years) than older (age 54-56 years) subjects for both laryngoscopic modalities. From this pilot study, we determined that there is a difference in male and female PGC prevalence and size. PGC is more common in females than males. Prevalence (or the detection rate) is about the same with RL and FL in females, but higher with RL than FL in males. The average score of the glottic opening, when present, was statistically significantly different between RL and FL in females but not in males. Furthermore, females had a larger PGCS on both modalities when compared with males, although this difference was only found to be statistically significant on RL; and complete glottic closure was more common in older than in younger subjects.