NEUROVASCULAR ANATOMY REVIEW IN THYROID AND PARATHYROID SURGERY. SURGICAL PROCEDURE TO MINIMIZE ADVERSE EVENTS
Authors: Torres-Morientes Luis Miguel , Tamayo-Gómez Eduardo , San Millán-González María , Losada-Campa Juan , Muñoz-Moreno María Fe , Santos-Pérez Jaime 
Published: July 2024

Introduction and objective:
Recurrent laryngeal nerve (RLN) injury is the most important complication in thyroid surgery and its side effects vary from dysphonia in unilateral laryngeal paralysis to stridor in bilateral laryngeal paralysis. Therefore, the anatomical identification and functional preservation of the nerve is essential in thyroid surgery. A variety of landmarks have been classically considered for this nerve’s identification, including the inferior thyroid artery (ITA), Zuckerkandl’s tubercule and Berry’s and Gruber’s ligaments. This study’s main objective is to identify the anatomical relationship between the recurrent laryngeal nerve and the inferior thyroid artery in order to determine the surgical procedure that best avoids recurrent injury.

Method:
This study reviews 440 thyroidectomies performed by the same surgeon - including total thyroidectomies, hemithyroidectomies and parathyroidectomies - from September 2011 to December 2020. The relationship between the recurrent nerve’s positions regarding the inferior thyroid artery was divided into prearterial, retroarterial or interarterial (between the bifurcation of branches of the artery). Other secondary variables were studied, including RLN branching, neuromonitoring, and parathyroid gland positions and their influence on post-surgical hypoparathyroidism. In total, 695 recurrent laryngeal nerves were dissected.

Results:
A total of 440 patients underwent surgery. Total thyroidectomy was performed in 253, hemithyroidectomy with or without isthmectomy in 159, isolated isthmectomies in 2 and parathyroidectomies in 26 patients. A total of 695 recurrent laryngeal nerves (RLN) were dissected, 690 (99.2%) nerves were identified, being 6 of them non-recurrent right laryngeal nerves (0.8%). On the right side the predominant nerve position was prearterial (50%) and on the left side the retroarterial crossing was predominant (69%). Other variables studied were the anatomical divisions of RLN before entering the larynx, observing nerve bifurcations in 46.7% of right nerves and 29.6% of left RLN. Superior parathyroid glands were positioned in 83.7% of the cases in a high position, inferior parathyroid glands were positioned in a low position in 70% of cases. Neuromonitoring was performed in 70% of RLN and the rates of unilateral transient and permanent laryngeal paralysis were 1.2% and 0.8% respectively.

Discussion:
Identification and preservation of the recurrent laryngeal nerve (RLN) is paramount in thyroid surgery to prevent injury, given its variable anatomical relationship with the inferior thyroid artery (ITA). A neurovascular anatomy review is carried in a series of 440 thyroidectomies.

Conclusions:
The anatomical relationship between RLN and the inferior thyroid artery (ITA) is the main landmark in recurrent laryngeal nerve’s surgical identification. It helps the anatomic preservation of RLN by decreasing and avoiding the feared potential nerve injuries and their subsequent complications.