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Neck ultrasonography for detection of non-recurrent laryngeal nerve.

BACKGROUND
Non-recurrent laryngeal nerve (NRLN) is a rare anatomical variant (0.3-6%) that is associated with some arterial abnormalities (absence of the brachiocephalic trunk and presence of a right aberrant subclavian lusorian artery). The availability of a preoperative diagnosis of NRLN may reduce the risk of nerve injuries. Preoperative ultrasonography (US) has been suggested as a reliable diagnostic tool to detect the arterial abnormalities associated with NRLN, but the literature is relatively scarce. This paper was aimed to review the literature, in order to offer an up to-date on this technique and its results.


METHODS
A web search, focusing on humans, was performed by PubMed database, including papers published up to August 2016, using the key words "ultrasonography" AND "non-recurrent laryngeal nerve" or "nonrecurrent laryngeal nerve".


RESULTS
Eight papers, including 3,740 patients who underwent neck US for the detection of NRLN were selected. Only five studies focused on the preoperative use of US. The incidence of NRLN varied between 0.4% and 1.94%. The sensitivity and specificity varied between 99-100% and 41-100%, respectively.


CONCLUSIONS
US is a simple, non-invasive and cost-effective method to detect NRLN, also if its accuracy is not absolute. It may be used preoperatively and to prevent the intraoperative nerve damage, since the risk of NRLN palsies is significantly reduced when a preoperative diagnosis is available.