Casal et al. Journal of Medical Case Reports 2010, 4:386 http://www.jmedicalcasereports.com/content/4/1/386 or detected in the imagiological study of the neck with ultrasound and computed tomography (CT) scan. A fine needle aspiration puncture was performed and the result was compatible with thyroid papillary cancer. In the Group Decision Clinic it was decided that the patient should undergo total thyroidectomy. During surgery, a non-recurrent right inferior laryn- geal nerve was noted (Figure 1). This nerve emanated from the right vagus nerve almost at a straight angle, entering the larynx 3 cm after its origin. The nerve did not show a recurrent course. The nerve on the left side had a normal configuration coming upwards in the tracheo-esophageal groove, in a recurrent fashion, pre- sumably from the left vagus nerve. The surgery and post-operative period was uneventful, and our patient had no change in his voice. Discussion The reported incidence of the non-recurrent ILN is widely variable. In some series, the proportion of this variation is [3-7] whereas in others it is as high as 3.9% [8-10]. In the largest series reported, including 6637 observations of the ILN during neck surgery, the frequency of the non-recurrent ILN was 0.54% (17 cases in 3098) on the right and 0.07% on the left (2 cases in 2846), corresponding to a global prevalence of 0.32% [11]. Figure 1 Intra-operative right lateral view of the neck. The right Inferior Laryngeal Nerve (ILN) is seen originating perpendicularly from the Vagus Nerve (VN) and entering the Larynx between the Crycoid Cartilage (CC) and the Thyroid Cartilage (TC), just below the Crico-Thyroid Muscle (CT). The Thyroid Gland (TG) is being retracted medially to increase exposure of ILN and allowing visualization of the Trachea (TR). The right ILN does not have any recurrent path. Page 2 of 3 Despite the discrepancies in the relative proportion of this variant of the ILN, most authors agree that this var- iant is most common on the right side. The embryologi- cal basis for this finding seems to be a vascular disorder known as arteria lusoria in which the fourth right aortic arch is abnormally absorbed [12]. Consequently, this vessel fails to drag the right recurrent laryngeal nerve (ILN) caudally when the heart descends, and the neck elongates during embryonic development [9,13,14]. This anomaly generally leads to a right subclavian artery that originates as a branch of a normal aortic arch and passes upward to the right behind the esophagus. The incidence of this vascular malformation is reportedly as high as 0.5 to 2% of the general population [15]. Even though it is usually asymptomatic, nearly 5% of these patients experience dysphagia (dysphagia lusoria) or symptoms related to artery tortuosity, and premature atherosclerosis. Rarely, it is associated with aneurism formation [15]. On the left side, a non-recurrent ILN has only been observed in cases of dextrocardia [13]. Theoretically, the pre-operative diagnosis of a non- recurrent ILN could be attempted with imaging studies, namely CT scan or magnetic resonance imaging (MRI), to visualize the arteria lusoria [14]. However, although the presence of anatomical variants of the ILN have been associated with a higher risk of iatrogenic injury during surgery in the head and upper thorax region [4], it has not yet been shown that the systematic use of pre-operative imaging studies can minimize this risk. Conclusion Invasive procedures in the head and neck region that may compromise the ILN are part of everyday clinical and surgical practice. A sound knowledge of the normal morphology and most frequent variants of the ILN, including its non-recurrent variant, can help doctors to minimize the risk of iatrogenic lesion to this nerve. Consent Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Authors’ contributions All authors have read and approved the final manuscript. DC played a major role in writing the manuscript and analyzed the patient’s data. AP aided in the editing of the manuscript and analyzed the patient’s data. DS participated in the writing and editing of the manuscript and analyzed the patient’s data. JRS aided in the editing of the manuscript and analyzed the patient’s data. Competing interests The authors declare that they have no competing interests.