Discussion
CRS may cause abnormal nasality and adverse effects on quality of life.14 However, only a few studies have investigated nasality changes in CRS patients. Hong et al. demonstrated that the nasalance of patients with bilateral nasal polyposis was significantly lower than that of healthy controls before operation and increased to the level of the healthy controls 3 weeks after FESS.7Two studies had investigated the impact of FESS on nasalance change in patients with high disease burden CRS with nasal polyps, and found that the nasalance returned to nearly preoperative level 3 to 6 months following FESS.11,15 To the best of our knowledge, this is the first study to discuss nasality in patients with unilateral CRS. These patients had only one side nasal airway involvement and had relatively less disease burden with favorable surgical outcomes.16 In the subjective evaluation, we found that 33.3% of unilateral CRS patients had abnormal nasality by self-scoring VAS and that 47.6% had noticeable abnormal nasality as evaluated by their partners. In addition, a negative correlation was found between the Lund-Mackay score and nasalance in patients with unilateral CRS.
Hyponasality is present in patients with sinonasal disease with obstruction of nasal airways.7 Sinonasal surgery alters the structure and patency of the nasal cavity, and the acoustic characteristics of the vocal tract change with it. Behrman et al. reported that decreased nasal mucosal surface area and widened nasal passages after sinonasal surgery will result in a decrease in acoustic damping and an increase in acoustic coupling with the paranasal sinuses. Therefore, sinonasal surgery may result in increased nasalance.17 Renata Soneghet et al. reported that the mean nasalance values of [i] increased significantly from 27.2% preoperatively to 39.8% 1 month after FESS.1 Kim et al. reported an initial increase in nasalance following FESS which eventually returned to near pre-operative values 6 months later.18 However, a trend toward increase of nasalance in [a], [i], [u] was still found after surgery, although the increase did not reach clinical significance (all P-valuesbetween 0.05 and 0.1). Otherwise, the postoperative sinonasal condition was not mentioned, and recurrent nasal polyps or edematous mucosa may also cause a decrease in nasalance postoperatively.
In our study, all patients underwent endoscopy, and the sinonasal mucosal status was nearly normal postoperatively. We found a significant increase in nasalance 1 year after FESS, particularly in patients who received wide opening FESS. The nasalance of [i], [m], and [MiMi] were significantly increased. The Lund-Mackay CT score was negatively correlated with preoperative nasalance ([i] and [m]) and positively correlated with postoperative nasalance change ([i] and [m]) with clinical significance. A higher nasalance change in patients who underwent wide opening FESS may be due to a relatively lower nasalance level preoperatively and a wider open sinonasal cavity postoperatively. The significantly increased nasalance following FESS was accompanied by a significant improvement in the subjective nasality assessments (in both patient-reported VAS scores and questionnaires reported by patients’ partners). These results imply that an increase in nasalance corresponded to a nasalance return to a relative normal value.
The nasalance did not correlate with the subjective VAS of abnormal nasality, but a significant negative correlation was found between preoperative nasalance ([a], [i], [u]) and the severity of nasal obstruction. A previous study revealed a correlation between the increase in the volume of the nasal cavity and the increase in the nasalance score in patients who underwent FESS due to CRS.9,19 These results imply that the patency of the nasal airway has a significant impact on nasalance change. The healing and regeneration of the sinonasal mucosa happens usually within 6 months, and mucosal vibration may normalize subsequently.20 Platt et al. found that the bony structure continued to change in average 14.3 months after wide opening ethmoidectomy.21 This alteration in the bony framework of the paranasal sinuses after operation may be another reason for the nasalance change after operation. In our study, a more significant change in nasalance was found in patients who underwent wide opening surgeries.
There are still some limitations in this study, and the first is the limited sample size included in research. Some patients can’t complete the entire post-op follow up and they were excluded from the study. Another limitation of this study is the lack of normal controls for comparison. However, the nasalance value is variable between individuals and may be influenced by age, race, sex, geographic regions, and habitual language.4,22,23 Therefore, a large sample size is needed to establish normative values. In our study, we compared pre- and post-operative nasalance to eliminate the possible bias of individual differences. Furthermore, our post-operative nasalance was close to the value of Mandarin speakers reported in the normal papulation.22