Background: Transcutaneous laryngeal ultrasonography (TLUS) was recently developed to assess recurrent nerve palsy after thyroid/parathyroid surgery, with variable rates of efficiency. The aim of the current study was to evaluate this technique using subjective estimation and post-processing quantitative data.
Methods: Fifty subjects presenting with a recurrent nerve palsy and 50 "controls" presenting with voice, swallowing, or breathing disorders following thyroid/parathyroid surgery were prospectively included. All of them underwent a flexible laryngoscopy, considered the gold standard, and a ten-second TLUS clip within the 10 days following surgery. In addition to the subjective interpretation of vocal fold motion, two quantitative criteria taking into account motion symmetry (symmetry index, SI) and amplitude (mobility index) of the two hemi-larynges were defined on TLUS acquisitions in adduction and abduction.
Results: The subjective interpretation provided a sensitivity of 100% and a specificity of 96%, compared to the gold standard. The quantitative criteria provided a sensitivity and specificity of both 82%, when based on SI solely. When combining SI and mobility index, the sensitivity reached 94%, but the specificity fell to 66%.
Conclusions: Visual assessment of recurrent nerve palsy using TLUS after thyroid/parathyroid surgery appeared a high sensitive and specific test compared to flexible laryngoscopy. Quantitative criteria are promising and need to be refined to better describe the whole TLUS video clip.