Single Dose Steroid Injection After Loss of Signal (LOS) During Thyroid Surgery is Effective to Recover Electric Signal Avoiding Vocal Cord Palsy and the Need of Staged Thyroidectomy: Prospective Evaluation on 702 Patients

Abstract

Background: Steroids are often used for the management of vocal cord palsy after thyroid surgery. There are no reports in the current literature of their intraoperative use, immediately after a loss of signal during neuromonitoring (LOS). We evaluate the impact of a single dose of 4 mg of dexamethasone on laryngeal nerve function, administrated at the time of a LOS during a nerve-monitored thyroidectomy. Methods: A prospective not randomized study was performed, dividing patients in two groups, when a LOS was detected. LOS was defined as an electromyographic signal (EMG) inferior to 100 μV when stimulating the inferior laryngeal nerve, according to international guidelines. In group 1 (G1), surgeon waits for signal’s recovery up to 20 min. Absence of a detectable signal after 20 min was predictive of vocal cord palsy; if it affected the first side of surgery the procedure was interrupted to avoid the risk of bilateral nerve palsy. In group 2 (G2), 4 mg of dexamethasone were injected within 10 min from a detected LOS, waiting 10 min for its effects. An EMG value > to 200 μV within 20′ after steroid administration was predictive of full recovery and normal post-operatory vocal cord function. Vocal cords motility was checked at postoperative day 1 in all patients by an experienced ENT. Results: Between January 2017 and December 2018, 702 patients underwent thyroid surgery under intermittent intraoperative nerve monitoring by two expert surgeons. A LOS was found in 22 patients in G1 and 16 in G2. Four patients in G1 spontaneously recovered electric signal (18.2%), while in G2 a signal was recovered in 14/16 patients (87.5%) (p < 0.001). This immediate effect was monitored by EMG, showing the increase in potentials at 10, 15 and 20 min after injection. ENT evaluation found vocal cord palsy, respectively, in 18/22 and 1/16 patients (G1 vs G2, p < 0.001). One of the patients in G2 who recovered electric signal presented transient palsy, fully recovered at 2 months, while the two patients who had a signal < 200 μV did not present postoperative cord palsy. In G1, 10/18 palsy were definitive. No permanent palsies were presents in G2. Conclusion: A single 4 mg iv dexamethasone injection within 10 min form a LOS during thyroid surgery exerts a therapeutic action, measurable by EMG modifications. It avoids vocal nerve palsy and the need of a staged thyroidectomy. It may also protect from permanent cord palsy, but the mechanism is unknown.