Endocrine Abstracts

Introduction: One of the most serious complications after thyroid surgery is dysfunction of the recurrent laryngeal nerve (RLN). RLN damage leads to disorders of the vocal folds (VFs). The "gold standard" method in VFs assessment is laryngoscopy, which causes significant discomfort to patients, requires consultation with an ENT specialist and additional equipment.

Purpose: The aim of the study was to prospectively evaluate translaryngeal ultrasound (TLUS) in the assessment of VFs function in patients after thyroid, parathyroid and neck lymph node surgeries. An additional goal was to identify preoperative and intraoperative factors that increase the risk of RLN damage.

Methods: The prospective study included a total of 219 patients who underwent 230 surgical operations. Patients’ vocal folds were analyzed independently by both TLUS and laryngoscopy before and after surgery. Additional variables obtained during TLUS were assessed, such as vocal fold displacement velocity (VFDV), arytenoids symmetry and more. In addition, a questionnaire was conducted to assess the discomfort experienced by patients during the examination with both methods. A multivariate analysis of prognostic factors for the occurrence of RLN dysfunction was performed.

Results: Thyroid cancer surgeries constituted 85% of all procedures. The incidence of RLN injury was 10.4% in all patients and 11.7% in the oncological subgroup. There were 1.7% transient and 8.7% permanent RLN injuries. The accuracy of TLUS compared to laryngoscopy was 98.3%, sensitivity 98.1%, specificity 100%. Laryngoscopy caused significantly more discomfort than TLUS. Detection of VFs in the whole group using TLUS was 94%. VFs were visualized in more women (99.0%) than men (76%). VFs visibility was lower among males, smokers, patients with higher BMI, multifocal cancer, higher left thyroid lobe volume. VFDV was lower for the vowels "a" and "e" on the right and "e" on the left side after RLN injury. Among patients with RLN damage TLUS more often showed VFs and arytenoids asymmetry and crescendo-decrescendo Doppler wave pattern. Factors contributing to RLN dysfunction included: lateral nodes metastases and theirs dissection, lymph nodes involvement and RLN entrapment to the tumour.

Conclusions: TLUS in a majority of cases can adequately assess whether the function of the VFs is intact or paresis/paralysis has occurred. It is non-invasive and rapid. It adds no extra cost and can be a part of the preoperative examination of the thyroid gland. TLUS in VFs assessment before and after thyroid surgery is a highly accurate tool and in most patients was not inferior to laryngoscopy.