Common causes of intraoperative neuromonitoring failure during thyroid surgery and practical solutions: a narrative review

Intraoperative neuromonitoring (IONM) provides real-time electromyographic assessment of recurrent laryngeal nerve and external branch of the superior laryngeal nerve function during thyroid surgery, supporting nerve identification, functional verification, and surgical decision-making. Technical and pharmacological failures remain clinically important sources of unreliable monitoring. These failures are distinct from true loss of signal caused by neural injury, and their principal sources include endotracheal tube electrode malposition, residual neuromuscular blockade, equipment malfunction, and procedure-specific difficulties encountered in robotic thyroidectomy and transoral endoscopic thyroidectomy vestibular approach. This narrative review categorizes the recognized causes of technical IONM failure, summarizes available evidence for each, and discusses practical preventive and corrective strategies.