The role of intra-operative nerve monitoring in reducing the risk of recurrent laryngeal nerve injury during thyroid surgery: A systematic review and meta-analysis

Background: Recurrent laryngeal nerve (RLN) palsy is an important complication following thyroid and parathyroid surgery. It can have a significant impact on patients' quality of life and is the most common cause of litigation after these procedures. The aim of this study was to assess the role of intra-operative nerve monitoring (IONM) during thyroid and parathyroid surgery in reducing the incidence rate of laryngeal nerve injury. Methods: Comprehensive searches of PubMed, EMBASE, and Cochrane databases were performed and quality of included papers was assessed using the Cochrane risk of bias tool and a modified Newcastle-Ottawa Scale (NOS). The results of included studies were summarised and meta-analyses were performed where appropriate. Results: Five randomised controlled trials (RCTs) and thirteen interventional cohort studies were included. Thirteen studies assessed the role of IONM in primary thyroid surgery, three in re-do procedures and two in minimally-invasive video-assisted thyroidectomy (MIVAT). Meta-analysis demonstrated: marginally significant lower rates of transient RLN palsy associated with the use of IONM in primary thyroid surgery (OR 0.71; 95% CI 0.50 - 1.00; p = 0.05); significant lower rates of transient RLN palsy associated with the use of IONM in revision thyroid surgery (OR 0.59; 95% CI 0.36 - 0.97; p = 0.04); no significant effect on permanent RLN injury in primary thyroid surgery (OR 0.84; 95% CI 0.47 - 1.50; p = 0.55); and no significant effect on transient RLN injury in MIVAT (OR 0.55; 95% CI 0.17 - 1.74; p = 0.31). Conclusion: This systematic review has shown that IONM can aid the surgeon to reduce the rates of transient RLN injury in primary and revision thyroid surgery. The wide variability in study design, definitions of RLN palsy and methods of assessing nerve injury were the main limitations encountered in this study.