Introduction: Objective of study is to provide a quantitative description of the amount of RLN irritation during ACDF and to correlate the amount of irritation with operative parameters.

Methods: In a series of 98 patients undergoing ACDF continuous IEMG monitoring of the vocal cords was performed with a specially designed, commercially available Endotracheal Tube. The amount of irritation was described as irritation score (IS) by use of our proposed formula IS=log( ∑ (AxD)/B ), where A is the amplitude of irritation, D the duration of irritation and B the baseline irritation

Results: The amount of RLN irritation as described by our formula was statistically higher in patients that had undergone previous surgery compared to de novo cases (p= 0.024), and in cases where self retained retractors were used compared to handheld retractors (p= 0.020). Although results were not statistically significant, the irritation score was higher in patients presented with postoperative hoarseness.

Conclusions: The use of our proposed scale may be a useful adjunct in the prevention of RLN injury in patients undergoing ACD with or without fusion.