Gurleyik Journal of Medical Case Reports 2011, 5:266 http://www.jmedicalcasereports.com/content/5/1/266 Page 3 of 4 Figure 3 Left RLN with extra-laryngeal terminal division. Each branch enters the larynx separately. Horizontal nerve anastomosis on the posterior branch of the RLN known as SILAB (magnified and edited operative photograph). discovered during thyroid operations [2,3,9,10]. Our patient is a rare example of triple ILN variations; co- existence of bilateral extra-laryngeal bifurcation of ILNs, right non-recurrent nerve and left SILAB. Synchronicity of three variations of the ILN in one patient is an extre- mely rare coincidence. The prevalence of non-recurrent nerve has been reported below 1% [5-7] and increases the risk of ILN injury. The laryngeal entry point for a non-recurrent ILN is the same as for a recurrent nerve. If the RLN is not found in its normal course during surgical explora- tion, the possibility of a non-recurrent nerve must be taken into account. Complete exposure of the RLN is mandatory to avoid nerve injury; especially near the Berry ligament where the nerve is more superficial and vulnerable during total thyroidectomy. The main anato- mical feature of our patient was the extra-laryngeal terminal division of a right non-recurrent nerve. The prevalence of bifurcated non-recurrent ILN is unknown; two variations have occurred in the same nerve. This is a “variation of the variation”. This double variation in the same nerve is extremely unusual. Extra-laryngeal branching of RLN is a common varia- tion reported in up to 65% of surgical and autopsy series [1-3,10]. Macroscopically discovered terminal division of the nerve during thyroid operations has a prevalence of 18-36% [2,3,9,10]. Bilateral bifurcation of both RLNs is relatively rare with a prevalence of 3-9% [9,10]. This bifurcation, in larger anterior and posterior branches, may have significant functions. The anterior branch has motor fibers, whilst the posterior branch is mainly sensi- tive [4,9]. In some cases, the posterior branch also has motor fibers, and may affect laryngeal function. It may innervate posterior cricoarytenoid (abductor function) and interarytenoid muscles [4]. Extra-laryngeal terminal division of the ILN must be identified, exposed and pre- served for motor function. The more superficial anterior branch, the principal motor division of the nerve, is under a greater risk of injury during Berry ligament dissection. The SILAB is an anastomotic branch from the middle or superior cervical sympathetic ganglion to the RLN. The prevalence of SILAB has been reported as 0.74- 1.5%. A large SILAB, with its horizontal course, may be mistaken for a non-recurrent nerve [6,8]. This branch brings sympathetic fibers to the ILN [4,6,8]. A left SILAB, which was localized in last 2-3 cm of the RLN, was discovered as a third variation of the ILN in our patient. Conclusion The co-existence of three variations of the ILN, a right non-recurrent nerve, bilateral extra-laryngeal bifurcation of the ILN and left SILAB, is an extremely unusual coin- cidence in one patient. The coincidence of a right non- recurrent nerve and bilateral bifurcation of both right and left nerves in the same patient is a very interesting feature. SILAB appeared as additional third variation of RLN in our patient. Extra-laryngeal bifurcation of the non-recurrent ILN is an extremely unusual anatomic finding. Association of two anatomic variations has occurred in the same nerve, presenting “the variation of the variation”. Consent Written informed consent was obtained from the patient for publication of this case report and any accompany- ing images. A copy of the written consent is available for review by the Editor-in-Chief of this journal. Abbreviations ILN: Inferior laryngeal nerve; RLN: Recurrent laryngeal nerve; SILAB: Sympathetic inferior laryngeal anastomotic branch.