The vagus nerve is the longest cranial nerve, innervating key regions including the laryngeal muscles. This study outlines a method for identifying the vagus nerve during thyroid operations to prevent injury and loss of function.
The vagus nerve, or VN, is the longest cranial nerve that innervates significant regions of the body, including the laryngeal muscles. Frequently, thyroid operations cause injury to the vagus nerve in the larynx, leading to loss of function.
To identify the vagus nerve, prepare an anesthetized pig intubated with an electromyography, or EMG, tube. An EMG tube is a device that aids in monitoring the electrical activity of the laryngeal musculature and provides an open airway for ventilation.
Disinfect the neck region and make a long transverse collar incision to expose the larynx. Lift the skin flap from the collarbone to the U-shaped bone in the midline region of the neck. Dissect the underlying muscles to expose the trachea and nerves.
Using a stimulation probe, briefly deliver electrical impulses to the nerves. Upon stimulation, sodium channels in the cell membrane open and sodium ions enter the cell, depolarizing the membrane. The resulting muscle response is recorded via EMG tube. This enables the identification of the nerve location and its functional status.
Once the vagus nerve is identified, incise the connective tissue layer and use forceps to clip the automated periodic stimulation, or APS electrode around it and connect it to the monitoring system. The APS electrode provides continuous low-level stimulation to the vagus nerve and records the subsequent electromyographic response.
Wearing sterile surgical gloves, use a scalpel to make a 10 to 15-centimeter transverse collar incision to expose the neck and the larynx, and raise the subplatysmal flap one centimeter cranially from the clavicle to the hyoid bone.
Remove the strap muscles to visualize the tracheal rings and nerves, and use a hand-held stimulation probe to carefully expose the external branch of the superior laryngeal nerve, the RLN, and the vagus nerve.
Position an automated periodic stimulation electrode on one side of the vagus nerve for stimulation during continuous intraoperative neural monitoring, and connect the electrode to the monitoring system.
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