A non-recurrent laryngeal nerve (NRLN) is a rare (incidence 0.3% to 1.3%) anatomical variant that results in a higher rate of vocal cord palsy following thyroid surgery. This team from China examined the utility of preoperative CT and intraoperative nerve monitoring in identifying these at risk patients. NRLN is associated with abnormalities of the aortic arch and brachiocephalic / subclavian arteries which are detectable by CT. Nine NRLN were detected on imaging out of 1574 patients undergoing thyroid surgery. Seven of these were identified preoperatively and two following a retrospective scan analysis. Intraoperative nerve testing required exposure of the vagus nerve at a proximal and distal level (inferior thyroid pole). A positive electromyography signal at the proximal vagus and negative signal at the distal vagus was diagnostic for NRLN; with positive signals at both levels suggestive of RLN. All nine NRLN were identified using nerve monitoring. This paper suggests that CT and intraoperative nerve monitoring may have a place in patients undergoing thyroid surgery. However the morbidity of the radiation exposure of CT and the additional dissection required when exposing the vagus nerve at two levels to identify a very rare anatomical variant makes it questionable whether this should be routine practice for all patients. There are also health economic factors to consider, as most patients currently will only have an ultrasound scan prior to thyroid surgery.

Increased prediction of right nonrecurrent laryngeal nerve in thyroid surgery using preoperative computed tomography with intraoperative neuromonitoring identification.
Gao E-L, Zou X, Zhou Y-H, et al.
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Jonathan Hughes

Locum Consultant, Oxford University Hospitals Trust, UK.

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