Background: In thyroid surgery, intra-operative neuromonitoring of the recurrent laryngeal nerve (RLN) and vagal nerve (VN) are performed as an adjunct to the gold standard of optical visualisation of the RLN, to avoid injury of the RLN, and subsequently paralysis of the vocal cords. Intermittent RLN neuromonitoring diminished the temporary RLN palsy rate, but continuous neuromonitoring could have to potential of avoiding any damage. Since no study evaluated continuous vagal stimulation before, the objective of this study was to evaluate continuous neuromonitoring in a clinical setting, to assess its' value in predicting vocal cord injury.
Methods: A single centre prospective study was performed from September 2010 till February 2012, including 100 consecutive thyroidectomies with continuous VN stimulation using an S-shaped electrode.
Results: In this study, 100 thyroidectomies (80 total thyroidectomies and 20 hemi-thyroidectomies) were analysed. On 180 nerves at risk (NAR), there were four RLN palsies (2.2 %), of which only one definitive. In the cases with temporary palsies, an intra-operative diminution of the amplitude occurred, recovering partially with release of traction. Loss of signal was seen in all four cases, with an abrupt loss of signal in the definitive one. The RLN function remained intact in the other 176 NAR.
Conclusion: Continuous neuromonitoring of the VN is accurate and precise in predicting vocal cord palsy. It is of tremendous importance that the vagal electrode is a-traumatic and gives a stable signal. The exact parameters regarding "warning signs" have yet to be determined, but amplitude changes seem to play a major role.