[Preoperative diagnosis of nonrecurrent inferior laryngeal nerve--usefulness of CT and ultrasonography].

Background And Object: The right nonrecurrent inferior laryngeal nerve (NRILN), which is usually associated with the right aberrant subclavian artery, is a risk factor of nerve injury during thyroid surgery. Therefore the presence of the NRILN should be diagnosed if possible before surgery. The aim of this study was to investigate the usefulness of computed tomography (CT) and ultrasonography (US) for preoperative diagnosis of the right-sided NRILN.

Subjects And Methods: We reviewed 1,561 patients who underwent thyroid surgery, during which the right inferior laryngeal nerve was exposed, at Yamashita thyroid and parathyroid clinic from April 2006 to April 2012. All medical records, CT findings and ultrasonograms of these patients were reviewed retrospectively.

Results: We recognized 11 patients who had the right-sided NRILN from the total of 1561 patients (0.71%). Ten of 1086 patients who underwent CT, had a right aberrant subclavian artery. CT findings were enabled us to predict the existence of the right NRILN before surgery. The sensitivity and specificity of CT for detection of the right-sided NRILN were 100% and 100%. On the other hand, we could detect the bifurcation of the innominate artery in 116 of 140 patients with cervical US before surgery, and therefore could confirm that the right inferior laryngeal nerve of the 116 patients was normal. The bifurcation of the other patients was not detectable and one of the 24 patients only had the right-sided NRILN during surgery. The sensitivity and specificity of cervical US for detection of the right-sided NRILN were 100% and 83.5% respectively.

Conclusions: Although CT is extremely useful for preoperative diagnosis of the right-sided NRILN because of its accuracy, cervical US is also a good method for making sure that the right inferior laryngeal nerve is normal.