Continuous neuromonitoring during radiofrequency ablation of benign thyroid nodules provides objective evidence of laryngeal nerve safety

• Published in: The American journal of surgery 2021-08, Vol.222 (2), p.354-360
• Main Authors: Sinclair, Catherine F., Téllez, Maria J., Peláez-Cruz, Roberto, Díaz-Baamonde, Alba, Ulkatan, Sedat
• Format: Article
• Language: English
• Subjects: Ablation; Anesthesia; Electrodes; Electromyography; General anesthesia; Integrity; Intubation; Laryngoscopy; Larynx; Medical instruments; Nerves; Neuromonitoring; Nodules; Patients; Questionnaires; Radio frequency; Radiofrequency; Radiofrequency ablation; Recurrent laryngeal nerve; Regrowth; Surgeons; Thyroid; Thyroid gland; Ultrasonic imaging
• ISSN: 0002-9610; 1879-1883
• DOI: 10.1016/j.amjsurg.2020.12.033

The recurrent laryngeal nerves(RLN) run immediately posterior to the thyroid capsule and could be injured during thyroid radiofrequency ablation(RFA). This study assesses whether RLN functional integrity is altered during RFA using continuous intraoperative neuromonitoring(CIONM). Prospective case series of twenty nodules treated with RFA under general anesthesia utilizing the laryngeal adductor reflex(LAR) for CIONM. Thirteen nodules abutted the posterior thyroid capsule and ‘danger triangle’ for RLN injury. The ablative field did not breach the posterior capsule; 40 W was the maximal power used adjacent to the capsule. No patient experienced significant LAR amplitude alterations. Pre and postoperative laryngoscopy and voice assessments were comparable. At 12 months’ median follow-up, no patient displayed posterior nodule regrowth. This prospective case series supports the premise that benign nodule RFA is safe with regards to RLN functional integrity provided the posterior capsule is not breached by the ablation zone and posterior power is ≤ 40 W •Continuous peri-procedural neuromonitoring shows that RLN functional integrity is not compromised by heat transmission during RFA.•Maximal power was 40W adjacent to the posterior thyroid capsule and the ablation zone never touched or breached the posterior thyroid capsule.•Distance between the electrode tip and posterior thyroid capsule was variable (range 3-5mm) depending on the ablation zone proximity to the capsule.•There was no posterior nodule regrowth during a median follow up of 12 months.•For anatomical reasons, during ablation the entire posterior thyroid capsule should be considered a ’danger zone’ for RLN safety.