Mini-invasive thyroidectomy and Intraoperative Neuromonitoring (IONM): a single high-volume center experience in 215 consecutive cases.

BACKGROUND Endocrine surgery recent evolution has been characterized by introduction of mini-invasive video-assisted technique. When a new technique is introduced in surgical use the rate of adverse events must be the same of previous standardized technique. In MIVAT procedure complication rate and in particular nerve injury risk is associated surgeon's experience. The new approach is the intraoperative neuro-monitoring (IONM) use in MIVAT in order to reduce the laryngeal nerve injury rate in a more technically difficult surgical procedure. METHODS We analyzed clinical and surgical data regarding 215 patients treated with MIVAT technique and simultaneous IONM utilization from September 2014 to December 2019 in a single high-volume surgical center. We recorded data regarding age, gender, preoperative diagnosis, surgical time, early postoperative hypocalcemia, hematoma and vocal cord palsy. We compared these data to our first 211 cases of MIVAT (July 2005 -June 2009) at the beginning of the learning curve, performed without using IONM. We tried to highlight the impact of MIVAT and IONM simultaneous use on surgical outcome comparing results to our previous studies, also highlighting the lerning curve effect. RESULTS We detected a postoperative transitory clinical hypocalcemia in 14 pts (6,5%). No postoperative hematoma was recorded. Using I-IONM during thyroidectomy, we recorded in 5 cases a loss of signal; in 3 cases (1,4%) we experienced a temporary postoperative vocal cord palsy, only 1 case of definitive palsy. We didn't highlight statistical differences in surgical complications rate between the first 211 cases and these last 215 cases. We haven't identify a statistical significative difference regarding IONM use during MIVAT procedure related to MIVAT performed without IONM. In our previous experience cases series of MIVAT the percentage of transitory nerve palsy reported was 2,4% (p=ns). Surgical indication has changed. CONCLUSIONS In our experience we report that the use of IONM in MIVAT is as helpful to improve the safe of procedure. The risk of nerve palsy in literature associated to MIVAT is the same of the related one to classic technique (CT). We haven't identify a statistical positivity to use IONM in MIVAT related to MIVAT without IONM. In our previous experience cases series of MIVAT the percentage of transitory nerve palsy reported was 2,4% (p=ns). The most important IONM effect, in our opinion is the "safety feeling" experienced by the surgeon using IONM in a more challenging procedure. As a University Hospital, training surgery residents, we also identified the IONM as a very useful teaching support.