Systematic review and meta-analysis on intra-operative neuro-monitoring in high-risk thyroidectomy

Introduction Use of intra-operative neuro-monitoring (IONM) during high-risk thyroidectomy has been suggested to decrease the rate of recurrent laryngeal nerve (RLN) palsy. However, current evidences were mixed and there was no large-scale study concluding its benefit. We evaluated the role of IONM in reducing RLN palsy during high-risk thyroidectomy and identified which high-risk subgroup would be most benefited. Methods A systemic review was performed to identify studies comparing the use of IONM and visual identification of RLN alone (VA) during high-risk thyroidectomy, namely re-operation, thyroidectomy for malignancy, thyrotoxicosis or retrosternal goitre. Rate of RLN palsy was presented in terms of number of nerve-at-risk (NAR). Meta-analysis on overall high-risk thyroidectomy and subgroups were performed using fixed or random-effects model. Results Ten articles were eligible for final analysis. There were 4460 NARs in VA group and 6155 NARs in IONM group. Comparing to VA, IONM had lower rate of overall [4.5% vs. 2.5%, Odd ratio (OR): 1.40, 95% confidence interval (CI): 1.12–1.79, p = 0.003] and temporary [3.9% vs. 2.4%; OR: 1.47, 95% CI: 1.07–2.00, p = 0.016] RLN palsy in overall high-risk thyroidectomies. On subgroup analysis, although numbers of NARs were less than minimal numbers required for a statistical powered study (2.1%–72.7%), use of IONM decreased the rate of overall RLN palsy during re-operation (7.6% vs. 4.5%, OR: 1.32, p = 0.021) and temporary RLN palsy during thyroidectomy for malignancy (3.1% vs. 1.6%, OR: 1.90, p = 0.026). Use of IONM tended to have a lower rate of overall RLN palsy during thyroidectomy for malignancy than VA alone. (3.5% vs. 2.1%, p = 0.050). Conclusions Selective use of IONM during high-risk thyroidectomy decreased the rate of overall RLN palsy. IONM should be applied during re-operative thyroidectomy and thyroidectomy for malignancy.