Learning curve for direct nasofibrolaryngoscopy in an endocrine surgery unit

Injury to the recurrent laryngeal nerve (RLN) is a specific complication of thyroid surgery. Flexible direct nasofibrolaryngoscopy (DNFL) is the gold standard for evaluating vocal cord mobility, although its systematic use and learning curve among endocrine surgeons remain poorly defined. The aim of this study is to identify factors related to the final result and how explorer experience or patient characteristics could influence in the evolution of the learning curve.

Retrospective observational study included 110 consecutive patients who underwent thyroid surgery between June 2022 and February 2024. A total of 123 DNFL procedures were performed by junior and senior endocrine surgeons, all of them without prior experience in the technique. Variables analyzed included demographic and clinical data, exploration time, and procedural success. Comparative statistical analysis, multivariate linear regression, and cumulative sum (CUSUM) analysis were used to evaluate the learning curve.

DFNL was successfully completed in 93.5% of cases, with no complications reported. The mean exploration time was 75.28 ± 58.23 s. Significant differences were observed in relation to study period (p < 0.01) and surgeon experience (p < 0.01); but not with pathology or patient characteristics. The regression model confirmed a gradual reduction in exploration time with increased experience. CUSUM analysis identified three learning phases and showed that performance stabilized after 35-40 procedures, regardless of the surgeon's level of experience.

DNFL was safe with a short and well-defined learning curve. Its integration into endocrine surgery practice may be feasible even for surgeons without prior experience.