Continuous versus intermittent intraoperative neuromonitoring in complex benign thyroid surgery: A retrospective analysis and prospective follow-up.

Objectives: To compare continuous (C-IONM) vs intermittent intraoperative neuromonitoring (I-IONM) in complex benign thyroid surgery, and to follow up patients with loss of signal (LOS) or unilateral vocal fold paralysis (UVFP).

Design: Retrospective clinical study, prospective case series.

Setting: University hospital and academic teaching hospital of Charité-University Medicine Berlin, Germany.

Participants: C-IONM- and I-IONM-assisted thyroid surgery was conducted in 357 patients diagnosed with recurrent goitre, Graves' disease, complex hyperparathyroidism, cervical preoperation (anterior access) and LOS in primary operation (2-stage thyroidectomy).

Main Outcome Measures: To evaluate the incidence of early postoperative and permanent UVFP, and to report the results of phonosurgical therapy in patients suffering from persisting dysphonia.

Results: In 346 patients enrolled (81.8% female, 18.2% male) with 613 nerves at risk (NAR) being monitored (409 I-IONM vs 204 C-IONM), early postoperative UVFP was observed in 10.5% of I-IONM vs 4.9% of C-IONM group (P < .05), permanent paralysis in 1.5% of I-IONM vs 1.0% of C-IONM group (P = .619). In total, 72 patients (21%) experienced pathological events (19 LOS < 100 μV, 53 transient or permanent UVFP). Three patients with permanent UVFP and persisting dysphonia received phonosurgery with stable improvements of all acoustic-aerodynamic parameters.

Conclusion: Compared to I-IONM, C-IONM-application in complex benign thyroid surgery shows a significant reduction of transient UVFP and a non-significant trend in preventing permanent UVFP. In persistent UVFP with dysphonia, endolaryngeal phonomicrosurgery and transcervical laryngeal framework surgery are long-term effective treatment approaches to improve vocal function.