Intraoperative Nerve Monitoring Parameters and Risk of Recurrent Laryngeal Nerve Injury in Thyroidectomy: A Systematic Review and Meta-Analysis.

Background/

Objectives

Recurrent laryngeal nerve injury (RLNI) is a major complication of thyroidectomy, affecting voice, airway protection, and quality of life. Intraoperative nerve monitoring (IONM) has been introduced to complement direct nerve visualization and reduce RLNI risk, but its efficacy remains controversial. This systematic review and meta-analysis aimed to determine RLNI prevalence with IONM, compare rates with historical no-IONM cohorts, perform head-to-head comparisons, and assess the influence of IONM characteristics.

Methods

PubMed, Scopus, Web of Science, Cochrane Library, and Google Scholar were searched for studies reporting RLNI rates in thyroidectomy with and without IONM. Pooled prevalence estimates were calculated for transient and permanent unilateral and bilateral RLNI in IONM studies and historical controls. Direct meta-analysis estimated pooled odds ratios (ORs) for RLNI risk reduction. Subgroup analyses examined IONM type, monitoring model, stimulation amplitude, voltage, and neuromuscular blockade use; meta-regression identified influential parameters.

Results

A total of 103 studies involving 132,212 patients met the criteria. Unilateral transient RLNI was lower with IONM (4%, 95% CI: 4-5%) than in historical controls (5%, 95% CI: 4-6%), while unilateral permanent RLNI was 1% in both groups. Bilateral RLNI was rare. Direct comparison showed a 38% reduction in transient unilateral RLNI (OR: 0.62, 95% CI: 0.42-0.79) and a 51% reduction in permanent unilateral RLNI (OR: 0.49, 95% CI: 0.34-0.70) with IONM. Continuous IONM, lower stimulation amplitudes (≤2 mA), and avoidance of neuromuscular blockade were protective.

Conclusions

IONM significantly reduces RLNI risk, particularly for unilateral injuries, with optimal protection achieved through continuous monitoring, low stimulation amplitudes, and avoidance of neuromuscular blockade.