Taste Function Versus Ultrastructure: Distinct Impacts of Inflammation and Surgery on the Chorda Tympani Nerve

ABSTRACT To investigate the primary factors influencing ultrastructural injuries of the chorda tympani nerve in patients with chronic otitis media, comparing the relative contributions of inflammatory severity and the type of surgical manipulation and to correlate these structural findings with postoperative taste function. Twenty‐one patients undergoing chorda tympani transection for chronic otitis media were enrolled. The transected nerve specimens were stratified by inflammatory severity (Low, Moderate, High) and surgical manipulation type (transection without tension, with tension and tearing subgroups). Ultrastructural alterations, including myelin sheath injury and axonal deformation, were observed via transmission electron microscopy and evaluated using a semi‐quantitative scoring system. These structural findings were further contextualised by data from a separate cohort of 256 patients, in which taste function was quantitatively assessed using gustatory strip tests from preoperative to six months postoperatively, stratified by similar surgical manipulation types and underlying disease pathology. Grouping by inflammatory severity revealed a significant gradient in nerve injury. The high‐severity inflammation group exhibited significantly higher scores for both myelin sheath injury (2.42 ± 0.35) and axonal deformation (2.40 ± 0.36) compared to the low‐severity group (0.91 ± 0.41 and 0.87 ± 0.42, respectively; all p < 0.001), with large effect sizes ( η 2 ≥ 0.75). No statistically significant differences were found in any injury indicators among the different surgical manipulation groups (transection without tension, with tension and tearing subgroups) (all p > 0.05). This inflammatory ‘pre‐damage’ provides a structural basis for the preoperative taste alterations and more rapid functional compensation observed in the inflammatory group in taste function studies. Meanwhile, functional taste assessment revealed that the incidence and duration of taste dysfunction were significantly influenced by the degree of intraoperative nerve manipulation, with severe traction and transection leading to the highest rates and most prolonged symptoms. This suggests that although the immediate pathological changes from surgical manipulation are not prominent against the background of pre‐existing inflammatory damage, they still significantly impact postoperative taste function. Regarding the impact of inflammation, chronic otitis media remodels the neural structure of the chorda tympani nerve, which can lead to preoperative taste alterations and influence the nerve's tolerance to and recovery from surgical trauma. As for surgical manipulation, although the surgical procedure did not cause immediate significant ultrastructural damage, it was the main clinical determinant of postoperative taste dysfunction, especially for tractional procedures. Therefore, clinical strategies should integrally consider both proactive preoperative inflammation control and meticulous intraoperative nerve handling, with special emphasis on minimising severe traction to optimise long‐term taste preservation.