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

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 4mg of dexamethasone on laryngeal nerve function, administrated at the time of a LOS during a nerve-monitored thyroidectomy. 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 100μV when stimulating the inferior laryngeal nerve, according to international guidelines. In group 1 (G1), surgeon waits for signal's recovery up to 20min. Absence of a detectable signal after 20min 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), 4mg of dexamethasone were injected within 10min from a detected LOS, waiting 10min for its effects. An EMG value > to 200μV 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. 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 20min 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 2months, while the two patients who had a signal < 200μV did not present postoperative cord palsy. In G1, 10/18 palsy were definitive. No permanent palsies were presents in G2. A single 4mg iv dexamethasone injection within 10min 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.