Purpose: Direct flexible laryngoscopy (DFL) is the golden standard to evaluate the vocal cord (VC) function in thyroid and parathyroid surgery pre- and postoperatively. Transcutaneous laryngeal ultrasonography (TLUS) could represent an alternative to the DFL and has been evaluated in the present study comparing the results of both methods performed at two referral centers for endocrine pathologies.
Methods: In the setting of a retrospective study, 668 patients (560 female, 118 male; mean age 50.3 ± 14.2) were included from two tertiary referral centers of endocrine surgery. In all patients, TLUS was performed pre- and postoperatively prior to transnasal DFL, which served as a golden standard. TLUS was performed by B-scan (probe 5-13 MHz, aperture 40 mm).
Results: Preoperative visualization of the vocal cords by TLUS was possible in 526 patients (78.7%). Due to the frequent thyroid cartilage calcification (TCC) in male patients, a significant difference in the visualization rate was found between female and male (88.7% vs. 26.8%) [p < 0.0001]. Additionally, the visualization rate was inversely related to the patient's age [p < 0.001]. The sensitivity of preoperative TLUS was found to be 66.7%, the specificity 100%. DFL confirmed a postoperative palsy in 34 out of 40 patients with supposed abnormal vocal cord mobility at TLUS and demonstrated a palsy in four more cases with supposed regular mobility at TLUS. Therefore, the sensitivity of postoperative TLUS was 86%, the specificity of 99.1%, positive predictive value 89.4%, negative predictive value 98.7%.
Conclusions: TLUS could represent an alternative for the evaluation of vocal cords mobility. This method has the potential to replace the DFL in the majority of cases, especially in female patients. Nevertheless, DFL is still necessary in about 20% of the patients with failed visualization at TLUS.
Keywords: Complications; Evaluation; Laryngeal ultrasonography; Laryngoscopy; Thyroidectomy; Vocal cord.