Continuous Intraoperative Nerve Monitoring in Thyroidectomies: A Systematic Review and Meta-Analysis

Abstract

Objective: Application of intermittent intra-operative nerve monitoring (I-IONM) as an aid in thyroidectomies is common practice worldwide. While I-IONM is significantly beneficial in thyroid surgeries, it is limited by its intermittent nature, thereby allowing the recurrent laryngeal (RLN) nerve to be at risk of injury in-between stimulations. In the last decade, the introduction of continuous intraoperative RLN monitoring (CIONM) has overcome this limitation by enabling the operator to verify the functional integrity of the vagus nerve-recurrent laryngeal nerve (VN-RLN) axis in real-time. We aim to present the current evidence on CIONM utility for thyroid surgery by conducting the first meta-analysis on this technique.Methods: A systematic review of literature was conducted by two independent reviewers via Ovid in the Medline, EM-BASE and Cochrane reviews databases. The search was limited to human subject research in peer-reviewed articles of all languages published between Jan 1946 and April 2019. Medical subject headings (MeSH) terms utilised were thyroid surgery, thyroidectomies, recurrent laryngeal nerve, vagal nerve, monitor and stimulation. Thirty-eight papers were identified from Ovid, another six papers were identified by hand-search. A random effect meta-analysis was performed with assessment of heterogeneity using the I 2 value.Results: A total of 23 papers that utilised continuous vagal nerve monitoring during thyroid surgery were identified. The proportion of temporary and permanent recurrent laryngeal nerve paralysis post-operation was 2.5% (95% CI 1.7-3.2%, I 2 = 37.7). The proportion of patients with permanent recurrent laryngeal nerve palsy post-operation was 0.05% (95% CI 0.08 -0.2%, I 2 = 0). Conclusion:CIONM is a safe and effective means by which RLN paralyses in thyroid surgery can be reduced.