Letter to the Editor Regarding “Thyroid Radiofrequency Ablation‐ Thermal Effects on Recurrent Laryngeal Nerve Using Continuous Intraoperative Neuromonitoring Animal Model”

We commend the authors on their article entitled "Thyroid Radiofrequency Ablation-Thermal Effects on Recurrent Laryngeal Nerve Using Continuous Intraoperative Neuromonitoring Animal Model,"1 which evaluates heat spread parameters for laryngeal nerve injury during radiofrequency ablation (RFA). The most significant finding was the lack of electrophysiologic data supporting the use of cold dextrose irrigation in the setting of periprocedural recurrent laryngeal nerve (RLN)/vagal injury. This finding is of particular importance given the mention of this rescue strategy in major North American guidelines,2, 3 raising questions as to whether this is a valid rescue strategy in the case of periprocedural dysphonia. However, there are significant limitations that limit the study's clinical relevance and applicability to in vivo human ablations. First, the spread of heat (SH) distance was determined by direct apposition of the electrode to connective tissue at varying distances (5, 3, 2, and 1 mm) from the lateral side of an exposed RLN after surgical removal of overlying thyroid/connective tissues. This absence of intervening tissues between the electrode tip and nerve may have artificially lowered or elevated observed SH thresholds, depending on whether those tissues usually attenuate or enhance (compared to air) SH. Second, 5 mm active tips are designed to be used at low power, not at 40 to 50 W as described in this study with potential effects on reported SH distances. As such, it is impossible to draw accurate SH conclusions for more commonly used 7 and 10 mm active tips at higher powers. A referenced study from 20214 utilized continuous nerve monitoring to document laryngeal nerve electrophysiology in humans undergoing thyroid RFA with electrode active-tip sizes 7 to 10 mm, concluding there is minimal thermal conduction to laryngeal nerves provided (a) the electrode tip remained 3 to 5 mm from the posterior thyroid capsule; (b) power was