The identification and prevention of injury to the inferior laryngeal nerve is one of the main issues in thyroid surgery. Sound knowledge of anatomic variants of the nerve is of major importance. In rare cases the nerve does not run the recurrent way and it is therefore difficult to identify the nerve. Abnormal developments of the aortic arch during embryogenesis include malformation of the great vessels and can be the reason for anatomic abnormalities. A cause for a nonrecurrent nerve on the right side is the so-called lusorian artery, a right retroesophageal subclavian artery. Left-sided nonrecurrent nerves are seldom if ever documented. Only two cases have been published so far of patients with situs inversus viscerum, where left nonrecurrent nerves were associated with inverse, left-sided lusorian arteries.