Comparison of Intraoperative Neuromonitoring With Transcartilaginous Needle Electrodes Versus Endotracheal Tube Electrodes in Thyroid and Parathyroid Surgery

Injury to the recurrent laryngeal nerve (RLN) is among the most important complications in thyroid and parathyroid surgery. Intraoperative neuromonitoring (IONM) of the RLN using electrodes placed on the endotracheal tube is now a standard procedure to facilitate nerve detection and visual identification, to maintain its anatomical and functional integrity and to reduce the rate of nerve injuries. The most common neuromonitoring technique involves the use of electrodes located on the surface of the endotracheal tube, which are in contact with the vocal cords and record the electromyographic signals caused by the electrical stimulation of the RLN by a probe manipulated by the surgeon.

However, this technique has certain disadvantages:

(i) Correct placement of the endotracheal tube is technically demanding and requires an experienced anesthesiologist.

(ii) Improper placement of the tube by the anesthesiologist, its displacement during patient hyperextended neck positioning, intraoperative rotation, or saliva interference between the tube electrodes and the vocal cords may all lead to inability to receive adequate signals and limit the sensitivity of the method.

(iii) Intraoperative readjustment of the tube position can be time-consuming and difficult.

The above neuromonitoring method is associated with a high negative predictive value (92-100%) according to the literature. However, its positive predictive value ranges between 10% and 90% which means that in the case of a decrease or loss of the initial neurostimulation signal, the true injury of the RLN is 10-90%.

Neuromonitoring with intraoperative placement of electrodes in the thyroid cartilage is an alternative method, in which the electrodes are placed by the surgeon in the perichondrium of the thyroid cartilage at the beginning of the operation. Their placement is simple, with almost no learning curve and does not require further preparation of the surrounding structures. Similarly to the endotracheal tube electrode, these also record the electromyografic signal from the electrical stimulation of the laryngeal muscles and RLN, however they are more sensitive in detecting the movement of the vocal cords and can potentially record a higher and more stable neurostimulation signal. In this way, the rate of false positive signal loss could be reduced compared to the technique of neuromonitoring with the electrodes on the endotracheal tube.

This PhD thesis aims to evaluate the effectiveness and reliability of neuromonitoring with transcartilaginous needle electrodes versus endotracheal tube electrodes in thyroid and parathyroid surgeries. It is a prospective multicenter study of diagnostic accuracy, with paired design, of the neuromonitoring signals (amplitude - latency), which will be obtained based on the standard algorithm V1, R1, EBSLN1, EBSLN2, R2, V2, before and after the end of the manipulations in each thyroid lobe, using both aforementioned techniques. Their positive and negative predictive value will be compared and evaluated with regard to the injury of the recurrent laryngeal nerve. To achieve the above, at least 300 patients who will undergo thyroid or parathyroid gland surgery will be evaluated and intraoperatively will undergo neuromonitoring with both methods. After the surgery, on the 1st postoperative day, all patients will undergo laryngoscopy to exclude or confirm injury of the RLN.