Monitoring of recurrent and superior laryngeal nerve function using an Airwayscope™ during thyroid surgery

Abstract

Abstract. In thyroid surgery, intraoperative identification and preservation of the recurrent laryngeal nerve (RLN) and superior laryngeal nerve external branch (SLNEB) are crucial. Several reports have proposed that electromyography (EMG) monitoring is an acceptable adjunct for identification and preservation of the RLN. However, a limited number of hospitals have access to an EMG monitoring system. Therefore, the development of another viable monitoring method is required. The aim of the present study was to design a new RLN and SLNEB monitoring method combining an Airwayscope™ (AWS) and a facial nerve stimulator. The facial nerve-stimulating electrode stimulates the RLN or SLNEB, so that the movement of the vocal cord may be observed with an AWS. This monitoring method was performed on 10 patients with a thyroid tumor. In all the cases, RLN and SLNEB were identified and vocal cord function was preserved. All the patients exhibited normal vocal cord function following surgery. Thus, the new RLN and SLNEB monitoring method using an AWS and a facial nerve stimulator is useful in thyroid surgery, and this method may be used as a reliable and available alternative to EMG monitoring to ensure the normal function of the vocal cord. IntroductionIn thyroid surgery, damage to the recurrent laryngeal nerve (RLN) and superior laryngeal nerve external branch (SLNEB) is the most serious complication. Therefore, it is necessary to identify and preserve these nerves. The electromyography (EMG) monitoring system represented by Nerve Integrity Monitor (NIM) (Medtronic Xomed, Jacksonville, FL, USA) is useful for RLN and SLNEB preservation in cases in which the tumor is large, or if there is tumor invasion into the adjacent tissue. Recently, RLN monitoring with an EMG has become widely applied (1-9). Intraoperative nerve monitoring is necessary for nerve function preservation. However, not all hospitals are equipped with an EMG monitoring system and, as a result, RLN and SLNEB monitoring is difficult. Therefore, an alternative monitoring method is required, and it was this need that drove us to design a novel RLN and SLNEB monitoring method. When RLN and SLNEB are stimulated with a facial nerve stimulator (FNS), movement of the vocal cord may be observed with an Airwayscope™ (AWS; Ricoh, Tokyo, Japan), more efficiently compared with the laryngeal fiberscope during surgery. The successful combination of these devices was employed as a complete alternative to EMG. In the present study, we were able to not only monitor and preserve the nerves, but also to confirm the absence of RLN injury following resection. Materials and methodsEquipment. AWS is a laryngoscope currently being used for difficult cases of endotracheal intubation under general anesthesia. A fiberscope is attached to the tip of the laryngoscope blade, from which an image is be observed via a 2.5-inch monitor (Fig. 1). An FNS is commonly used in parotid surgery and neurosurgery. The nerve is electrically stimulated by the FNS probe during surgery (Figs. 2 and 3).Metho...

Investigation of Superior Laryngeal Nerve Disorders with Laryngeal Electromyography in Patients with Hoarseness

“…In a study in ten patients, the researchers used a technique called "airway scope" to monitor recurrent laryngeal nerve and SLN intraoperatively. In this study, vocal cord motion, which occurred by stimulation given to recurrent laryngeal nerve and SLN, was visualized by "airway scope" device and it was reported to be an important technique for surgical safety (8). In this study, we observed the polyphasic MUAPs in L-EMG of one patient with vocal cord paralysis.…”