Damage to the RLN can be either by excessive lateral dissection, thermal injury from cautery, or from retraction injury. It may be difficult to reinsert the tracheostomy tube if it becomes dislodged before healing of the incision and establishment of a mature stoma, especially if the ends of the cartilage ring that was cut in the operation resume their normal position. For stenosis with a prior tracheotomy, the anterior wall of the trachea just superior to the region of maximal adherence is identified. The anterior border of the sternocleidomastoid muscle is dissected from its attachment to the sternum. The aperture by which the mouth communicates with the pharynx is called the isthmus faucium. It also acts as a covering for the second and the third tracheal rings. http://en.wikipedia.org/wiki/Thyroid_isthmus, http://medical-dictionary.thefreedictionary.com/isthmus+of+thyroid, Last updated on February 4th, 2018 at 11:29 am. If possible, the circumferential dissection is carried up along the lesion itself. Circumferential dissection is performed at the level of the lower border of the lesion. 3rd ed. Paratracheal or pretracheal placement of the tracheal tube can be a significant intraoperative complication if manual control of the airway is not maintained until end-tidal CO2 is confirmed. A Penrose drain is passed around the trachea at the lower end of the resection, where the circumferential dissection has been performed. Lower laryngeal lesions and upper tracheal lesions can be accessed through an anterior transcervical approach. IOPTH levels may be used to confirm adequate resection.