Innervation of Human Cricopharyngeal Muscle By Recurrent Laryngeal and External Branch of Superior Laryngeal Nerve

This study group consisted of a consecutive patients undergoing thyroid surgery with intraoperative neuromonitoring (NIM 3.0 Nerve Monitoring Systeme (Medtronic Xomed, Jacksonville, FL, USA) ) for various diseases. In all patients, each side of the neck operated was considered as a separate entity in our study.

EMG recordings were accomplished with a pair of needle electrodes inserted into the CP and mid-portion of the CT muscle that is located on the superior side of the RLN, which were plugged into the third and fourth channels of interface-connector box, respectively, at the end of the thyroidectomy or lobectomy. The investigators evaluated the innervation pattern of the CT muscle in an other study. Therefore the EBSLN is the main supplier of the CT muscle, the EMG findings of the CT muscle were used to confirm it, in this study.

EBSLN, pharyngeal plexus (PP), RLN and vagus nerve were stimulated with a monopolar stimulator probe at 1 mA. While stimulating these nerves, the ipsilateral CP muscle was visually observed for possible contractions and electromyographic recordings were obtained with the 4-channel NIM 3.0 Nerve Monitoring System.

Inclusion criteria

• The patients who underwent thyroidectomy.

Exclusion criteria

• Preoperative RLN palsy
• Thyroid cancer with massive extrathyroidal extension
• Intentional nerve transection because of cancer invasion
• The assessment failure of nerve function due to the technical deficiency of the IONM equipment