Thyroid-cartilage and anterior-laryngeal electrodes provide higher and more frequently adequate electromyographic signals in intraoperative neuromonitoring during thyroid surgery: a systematic review and meta-analysis

Background: Endotracheal tube electrodes are commonly used for intraoperative neuromonitoring (IONM) during thyroid and parathyroid surgery, but tube displacement and inconsistent vocal fold contact may compromise electromyographic signal quality. Thyroid cartilage and anterior laryngeal electrodes offer an alternative recording interface that is less dependent on endotracheal tube position. This systematic review and meta-analysis aimed to compare thyroid cartilage or anterior laryngeal recording electrodes with endotracheal tube electrodes in patients undergoing thyroid or parathyroid surgery, and to determine whether they provide higher and more frequently adequate electromyographic signals without compromising clinical safety.

Methods: PubMed, Web of Science, Scopus, and the Cochrane Library were searched for comparative studies evaluating thyroid cartilage or anterior laryngeal electrodes against endotracheal tube electrodes. Random effects models were used to pool continuous outcomes as mean differences (MD) and dichotomous outcomes as risk ratios (RRs). Risk of bias was assessed with ROBINS-I and certainty of evidence with GRADE.

Results: Nine studies involving 1,206 patients and 2,311 nerve at risk or surgical side observations were included. Thyroid cartilage electrodes produced higher V1, V2, R1, and R2 amplitudes, with MDs of 571.28, 591.86, 604.16, and 847.76 µV, respectively. Adequate initial V1 signals of at least 500 µV were more frequent with thyroid cartilage recording, with an RR of 1.60. S2 amplitude was also higher, while S1 amplitude remained inconclusive. No clear differences were observed in latency, overall loss of signal, transient vocal cord palsy, or permanent vocal cord palsy. False positive loss of signal favored thyroid cartilage electrodes but did not reach statistical significance. No electrode-related complications were reported among 1,096 exposed patients. These small, non-randomised cohorts, however, cannot establish equivalent safety or exclude uncommon complications.

Conclusions: Thyroid cartilage and anterior laryngeal electrodes provide stronger and more frequently adequate electromyographic signals than endotracheal tube electrodes without evidence of increased complications. Their principal advantage appears to be improved recording stability rather than direct prevention of recurrent laryngeal nerve injury. The review was registered in PROSPERO (CRD420261454193) and received no funding.