Successful Prediction of a Left Nonrecurrent Laryngeal Nerve in a Patient With Right-Sided Aorta and Aberrant Left Subclavian Artery

BACKGROUND

Left nonrecurrent laryngeal nerve (LNRLN) is an extremely rare anatomic variant. The development of such anatomic variation requires the regression of both the fourth (aortic arch) and sixth (ductus arteriosus, DA) arches on the left side. Preoperative prediction of this variant is difficult but might reduce risk of nerve injury.

METHODS

A 34-year-old female was indicated for thyroidectomy for a 2.4 cm follicular neoplasm and Graves' disease. Due to a positive medical history of 22q11.2 microdeletion and unexplained left vocal cord paralysis, a preoperative chest computed tomography (CT) scan was obtained and revealed a right-sided aorta (RSA) and aberrant left subclavian artery (ALSA) without Kommerell's diverticulum. A left-sided NRLN was then highly suspected.

RESULTS

Thyroidectomy was performed under general anesthesia with the utilization of intraoperative laryngeal nerve monitoring. A LNRLN was confirmed intraoperatively.

CONCLUSIONS

Right-sided aorta and ALSA indicate embryologic regression of the left fourth primitive aortic arch. The absence of Kommerell's diverticulum at the origin of the ALSA indicates the lack of high-pressure blood flow from the pulmonary artery to the ALSA through the ductus arteriosus during embryogenesis, suggesting the embryologic regression of the left sixth primitive aortic arch. The presence of all 3 radiologic features thus highly suggests the possibility of a LNRLN.

Coexistence of Right Nonrecurrent Nerve and Bifurcated Recurrent Laryngeal Nerve Pointed by Zuckerkandl's Tubercle

The recurrent laryngeal nerve (RLN) has many anatomical variations and various relations with adjacent structures. Identification and total exposure of the cervical part of the RLN was performed during operations on the thyroid gland. An extremely rare anatomical variation of the nerve was encountered during the surgical procedure. Coexistence of both right RLN and non-RLN was observed in one patient surgically treated with total thyroidectomy. We first exposed the right RLN with an extralaryngeal terminal bifurcation at its usual position. Thereafter, we also identified an ipsilateral non-RLN joining the anterior branch of the RLN just before laryngeal entry. A Zuckerkandl's tubercle has pointed out the junction of the two nerves. In this period, the incidence of coexistence of non-RLN and RLN was 0.2% in our series. A non-recurrent course is a rare anatomical variation of the inferior laryngeal nerve. The coexistence of both non-RLN and RLN is an extremely rare anatomical finding which should be taken into account during thyroid surgery.

Neurological complications in thyroid surgery: a surgical point of view on laryngeal nerves

THE CERVICAL BRANCHES OF THE VAGUS NERVE THAT ARE PERTINENT TO ENDOCRINE SURGERY ARE THE SUPERIOR AND THE INFERIOR LARYNGEAL NERVES: their anatomical course in the neck places them at risk during thyroid surgery. The external branch of the superior laryngeal nerve (EB) is at risk during thyroid surgery because of its close anatomical relationship with the superior thyroid vessels and the superior thyroid pole region. The rate of EB injury (which leads to the paralysis of the cricothyroid muscle) varies from 0 to 58%. The identification of the EB during surgery helps avoiding both an accidental transection and an excessive stretching. When the nerve is not identified, the ligation of superior thyroid artery branches close to the thyroid gland is suggested, as well as the abstention from an indiscriminate use of energy-based devices that might damage it. The inferior laryngeal nerve (RLN) runs in the tracheoesophageal groove toward the larynx, close to the posterior aspect of the thyroid. It is the main motor nerve of the intrinsic laryngeal muscles, and also provides sensory innervation to the larynx. Its injury finally causes the paralysis of the omolateral vocal cord and various sensory alterations: the symptoms range from mild to severe hoarseness, to acute airway obstruction, and swallowing impairment. Permanent lesions of the RNL occur from 0.3 to 7% of cases, according to different factors. The surgeon must be aware of the possible anatomical variations of the nerve, which should be actively searched for and identified. Visual control and gentle dissection of RLN are imperative. The use of intraoperative nerve monitoring has been safely applied but, at the moment, its impact in the incidence of RLN injuries has not been clarified. In conclusion, despite a thorough surgical technique and the use of intraoperative neuromonitoring, the incidence of neurological complications after thyroid surgery cannot be suppressed, but should be maintained in a low range.

Non-recurrent laryngeal nerve

Injury to the recurrent laryngeal nerve is a serious complication in thyroid and parathyroid surgery. The anatomy of the recurrent laryngeal nerve is variable. Non-recurrent nerve is a very rare variation of the inferior laryngeal nerve. Because of the anatomical variations of the nerve, preservation of the nerve is the optimal strategy during surgery. In this case report, we present a non-recurrent laryngeal nerve abnormality in a patient who underwent parathyroidectomy, thyroidectomy and functional neck dissection for malignant parathyroid disease. A non-recurrent laryngeal nerve was identified during nerve exploration.

Non-recurrent inferior laryngeal nerve: case report and review of the literature

Total thyroidectomy is nowadays the operation of choice in the majority of endocrine surgery centers, whether the pathology is benign or malignant. To obtain good results, a thorough knowledge of local anatomy and a profound respect for hemostasis are necessary. Routine, at least visual, identification of the inferior laryngeal nerve (ILN) is considered gold standard and is strongly recommended. Surgeons are generally aware of the variations the nerve can have, especially on the right side. Although very rare, one such variation, with possible great impact on outcomes, is the non-recurrent route of the nerve. We present the case of a middle-aged woman with a multinodular goiter scheduled for elective surgery. During total thyroidectomy, on the right side, we were not able to find the inferior laryngeal nerve in its usual position, using the customary anatomical landmarks. Instead, we encountered it emerging directly from the right vagus nerve, at a rather right angle and entering the larynx as a unique non-bifurcating nerve. Thus, it could be spared from any injury and protected, although it could have been easily confounded with a vascular structure, given its transverse course.We think it is never overmuch to repeat that the routine identification and exposure of the inferior laryngeal nerve is a must for the thyroid surgeon in order to safely preserve its integrity.