Continuous laryngeal nerve integrity monitoring during thyroidectomy: does it reduce risk of injury?

To determine if continuous laryngeal nerve integrity monitoring (NIM) during thyroidectomy is associated with a decreased risk of postoperative recurrent laryngeal nerve (RLN) injury.

Retrospective cohort study of 165 patients who underwent thyroidectomy at a resident teaching institution between 1999 and 2002. The control group had 120 nerves at risk (NAR) whereas the NIM group consisted of 116 NAR. Primary outcome measures included postoperative RLN paralysis, paresis, and total injury rates.

RLN paralysis occurred in 2.54% NAR in the control group and 0.86% in the NIM group [relative risk (RR) = 0.34, 95% confidence interval (CI95) = 0.04-3.27, P = 0.62]. Temporary RLN paresis occurred in 4.24% NAR in the control group and 3.45% in the NIM group (RR = 0.9, CI95 = 0.23-3.55, P = 0.89). Total RLN injury occurred in 6.78% NAR in the control group and 4.31% in the NIM group (RR = 0.66, CI95 = 0.21-2.09, P = 0.48). When compared to all other NAR, advanced T-stage malignancy was associated with a significantly increased risk of RLN paresis (T4 RR = 9.0, CI95 = 2.56-31.67, P = 0.0006; T3+T4 RR = 7.5, CI95 = 2.17-25.86, P = 0.0001) but not paralysis. NIM did not significantly reduce the risk of RLN paresis in the advanced T-stage subset (T3+T4 RR = 0.36, CI95 = 0.04-3.0, P = 0.59).

There were no statistically significant differences in RLN paralysis, paresis, or total injury rates between control and NIM groups, even in subsets with advanced T-stage and increased baseline risk. Advanced T-stage is a significant predictor of RLN paresis in this cohort.