American Association of Endocrine Surgeons- Annual Meeting Abstract Papers

INTRAOPERTIVE NEUROPHYSIOLOGY TESTING OF THE RECURRENT LARYNGEALNERVE: PLAUDITS AND PITFALLS
Samuel Snyder, MD, John Hendricks, MD
Scott & White Memorial Hospital, Temple, Texas

Background: Identification and preservation of the recurrent laryngeal nerve (RLN) is an essential aspect of thyroid and parathyroid surgery. In experienced hands this can be accomplished in close to 99% of patients undergoing this type of surgery. Electrode imbedded endotracheal tubes allow continuous intraoperative assessment of the muscular action of the vocal cords when connected to an EMG response monitor. Whether this recently developed device enhances or hinders the identification and preservation of the recurrent laryngeal nerve is unclear.
Methods: The utility of continuous intraoperative neurophysiology testing of the recurrent laryngeal nerve was evaluated prospectively in 100 patients undergoing 103 thyroid and/or parathyroid operations. There were 74 bilateral and 20 unilateral thyroidectomies and 8 bilateral and 1 unilateral parathyroidectomies with/or without additional thyroidectomy that involved assessment of 185 recurrent laryngeal nerves. The experience with the first 93 RLNs was compared to the subsequent 92 RLNs.
Results: Overall 97.8% of recurrent laryngeal nerves were identified intraoperatively: 1.6% visually only, 2.2% nerve stimulator only, and 94% both. There was one transected RLN (1.1%) in each study group. The nerve monitor could not alert the surgeon to prevent these injuries. Overall there were 14 instances of non-function of the RLN (7.6%), either initially or subsequently during the operation and 4 resulting in temporary paralysis of the RLN (2.2%). All nerves were visually intact. There were 8 instances of altered function of the RLN (4.3%) with no altered vocal cord function post operatively. The stimulator aided dissection of the RLN in 17 instances (9%). There were 7 episodes (4%) of significant equipment dysfunction that hampered surgical dissection. There were no statistically significant differences between the study groups except the increased use of the nerve stimulator to first identify the location of RLN before visual confirmation: 4 of 93, initial group vs. 25 of 92, latter group, p<0.001.
Conclusions: Intraoperative neurophysiology testing of the recurrent laryngeal nerve can aid the anatomic identification of the RLN only if a positive EMG response is obtained. A negative EMG response can indicate a non-nerve structure, altered function of the RLN, or equipment set-up malfunction. Intraoperative neurophysiology testing can not necessarily prevent recurrent laryngeal nerve transection.