Recurrent laryngeal nerve monitoring during mediastinoscopy: predictors of injury.

BACKGROUND: Recurrent nerve injuries occur during mediastinoscopy despite assiduous technique. We evaluated mediastinoscopy by monitoring laryngeal nerve stimulation during the surgery. These techniques utilize sensing electrodes on laryngeal masks to evaluate stimulus of the larynx, and are used to identify recurrent nerves during redo neck surgery.

METHODS: Fifteen patients were monitored during the entire mediastinoscopy. The laryngeal sensor was placed just before intubation. All patients had a suprasternal incision, digital dissection along the anterior wall of the trachea, and harvest of the nodes in the left paratracheal (4L), right paratracheal (4R), and subcarinal (7) positions. Cautery was used when needed in the subcarinal space and the right paratracheal groove.

RESULTS: Surprisingly, 14 of 15 patients demonstrated intense recurrent nerve stimulation during digital dissection along the anterior wall of the trachea. This dissection activated the right and left recurrent nerves. Though the use of cautery on the left caused significant laryngeal nerve activity, cautery in the subcarinal space and on the right caused very little activity. One patient was found to have a (transient) recurrent nerve injury after surgery. She demonstrated intense activity both during dissection along the anterior wall of the trachea, and during removal of a left paratracheal node.

CONCLUSIONS: Our data demonstrate that traction in the anterior mediastinum causes the greatest stimulation to the nerves, even greater than direct stimulation with current. Thus, these data suggest that injuries could result only from traction. Traction on both recurrent nerves can occur with dissection along the trachea. Laryngeal nerve monitoring can be used to direct biopsies in the left paratracheal groove.