Visual and electrophysiological identification of the external branch of superior laryngeal nerve in redo thyroid surgery compared with primary thyroid surgery

Abstract

Purpose Thyroid reoperations are surgically challenging because of significant anatomical variance. Visual and functional identification of the external branch of the superior laryngeal nerve (EBSLN) were studied in 2 groups of patients who underwent primary and redo thyroid surgery. Methods This study was conducted on 200 patients: 100 patients with redo and 100 patients with primary thyroid surgery. In addition to visual identification, nerve branches were functionally identified by intraoperative nerve monitoring (IONM). Visual, functional, and total identification rates of the EBSLN in both primary and redo surgery were determined and compared between the 2 groups. Results We attempted to identify 138 and 170 EBSLNs at risk in redo and primary surgery, respectively. Visual identification rates were 65.3% and 30.4% (P < 0.001) in primary and redo surgery groups, respectively. In total, 164 (96.5%) and 97 EBSLNs (70.3%) were identified in primary and redo surgery, respectively (P < 0.001), including the use of IONM. In primary surgery group, 53 nonvisualized EBSLNs of 164 identified nerves (32.3%) were determined by IONM alone. In redo surgery group, 55 of 97 identified nerves (56.7%) were determined by IONM alone (P < 0.001). Conclusion Both visual and total identification rates of the EBSLN are significantly decreased in reoperative thyroidectomy. IONM increases the total identification rate of the EBSLN in primary and redo thyroid surgery. Electrophysiological monitoring makes a substantial contribution to the identification of the EBSLN both in primary and especially in redo thyroid surgery.

Utility of video-assisted method for identifying and preserving the external branch of the superior laryngeal nerve during thyroidectomy

“…In the present study, we achieved a 91% EBSLN exposure rate (61 in 67 nerves) based on visual exposure and confirmed that nerve function was good through the contraction of the cricothyroid muscle. This rate is satisfactory compared with those reported in previous studies with IONM (33)(34)(35).…”

Investigation of potential neuropharmacological activity of neostigmine‐glycopyrrolate for intraoperative neural monitoring in thyroid surgery

“…We included these results in our study because in most cases, the EBSLN is approached before the VN and RLN, and we believe that IONM to protect the EBSLN is just as important as the RLN. Because IONM helps the visual and functional identification of the EBSLN and decreases the rate of EBSLN injury, the routine use of IONM for EBSLN is encouraged 31,32 …”

Unmapped landmarks around branches of the Superior Laryngeal Nerve: An exploratory cadaveric study

“… 24 Though the latest recommendation is to use an ‘intraoperative nerve monitor’ for locating and preserving these branches, the manoeuvre is of little help without in-depth knowledge of its relationships and known anatomical variations. 24 , 25 , 26 , 27 After arising from the inferior nodosum of the cranial nerve X at the level of the C2 cervical vertebra, the SLN runs down dorsal to the carotid sheath and bifurcates into two branches at around 1.5 cm from its origin and approximately 2.5 cm cranial to the carotid bifurcation. 1 , 5 , 24 The larger IBSLN runs downwards along the internal carotid artery and dorsal to it until it crosses the greater cornua of the hyoid bone.…”