Abstract
BackgroundInjury to the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy results in a lowered fundamental frequency of the voice and deteriorated voice performance in producing high-frequency sounds. It remains unclear if the use of intraoperative nerve monitoring (IONM) can improve the clinical outcome of thyroidectomy in terms of preserved individual voice performance. This study was designed to test that hypothesis.MethodsA total of 210 consenting female patients planned for total thyroidectomy were randomly assigned to two groups equal in size (n = 105): visual inspection of the EBSLN and RLN vs. this plus additional EBSLN and RLN monitoring. The primary outcome was the identification rate of the EBSLN. The secondary outcomes included: anatomical variability of the EBSLN according to the Cernea classification and changes in postoperative voice performance. Voice assessment included pre- and postoperative videostrobolaryngoscopy and an analysis of maximum phonation time (MPT), voice level (VL), fundamental frequency (Fo), and voice quality rating on the GRBAS scale.ResultsThe following differences were found for operations without vs. with IONM: identification rate of the EBSLN was 34.3 % vs. 83.8 % (p < 0.001), whereas a 10 % or higher decrease in phonation parameters was found in 10 % vs. 2 % patients for MPT (p = 0.018), 13 % vs. 2 % for VL (p = 0.003), and 9 % vs. 1 % for Fo (p = 0.03), a change in the GRBAS scale > 4 points in 7 % vs. 1 % (p = 0.03), and temporary RLN injury was found in 2 % vs. 1 % (p = 0.56), respectively.ConclusionsThe use of IONM significantly improved the identification rate of the EBSLN during thyroidectomy, as well as reduced the risk of early phonation changes after thyroidectomy.
Highlights
Phonation changes after thyroidectomy have been reported in many investigations [1,2,3,4,5,6,7]
The following differences were found for operations without vs. with intraoperative nerve monitoring (IONM): identification rate of the external branch of the superior laryngeal nerve (EBSLN) was 34.3 % vs. 83.8 % (p \ 0.001), whereas a 10 % or higher decrease in phonation parameters was found in 10 % vs. 2 % patients for maximum phonation time (MPT) (p = 0.018), 13 % vs. 2 % for voice level (VL) (p = 0.003), and 9 % vs. 1 % for Fo (p = 0.03), a change in the GRBAS scale [ 4 points in 7 % vs. 1 % (p = 0.03), and temporary recurrent laryngeal nerve (RLN) injury was found in 2 % vs. 1 % (p = 0.56), respectively
In group A, the EBSLNs and RLNs were routinely identified by visualization alone, whereas in group B, the standard practice of attempting to visually identify and preserve the EBSLNs and RLNs was continued supported by adjunct of the IONM system
Summary
Phonation changes after thyroidectomy have been reported in many investigations [1,2,3,4,5,6,7]. Intraoperative nerve monitoring (IONM) has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification, and this technique can be used to identify both the recurrent laryngeal nerve (RLN) and the EBSLN [12, 13] It remains unclear whether there is any IONM-added value to the clinical outcome of thyroidectomy in terms of preserved individual voice performance. Injury to the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy results in a lowered fundamental frequency of the voice and deteriorated voice performance in producing high-frequency sounds It remains unclear if the use of intraoperative nerve monitoring (IONM) can improve the clinical outcome of thyroidectomy in terms of preserved individual voice performance.
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