Bilateral Investigation of the Anatomical Relationships of the External Branch of the Superior Laryngeal Nerve and Superior Thyroid Artery, and also the Recurrent laryngeal Nerve and Inferior thyroid Artery

The relationships of both the external branch of superior laryngeal nerve with the superior thyroidal artery and the recurrent laryngeal nerve with the inferior thyroidal artery were examined on the fixed cadavers of 4 adult women and 26 adult men. A total of 32 external branches of superior laryngeal nerve, 16 on each side, were dissected. When left and right sides were assessed altogether, 71.9% were medial to the artery while 28.1% were in between the branches. No nerve was found to be lateral to the artery. Thus the type in which the nerve is exposed to surgical trauma was found to be present in 28.1% of the cases. Only 12 of the cadavers could be assessed for symmetry and three fourths were found to have bilaterally symmetric relationship. A total of 52 Recurrent Laryngeal Nerves, 27 on the left and 25 on the right side were dissected. When bilateral symmetry was assessed in 21 cadavers, one third of the Recurrent Laryngeal Nerves were found to be bilaterally symmetrical. Inferior Thyroidal Artery was missing in 4 sides; bilaterally in one cadaver and unilaterally in 2 cadavers. Thus, artery-nerve relationship was assessed on 48 sides, 25 on the left and 23 on the right. On the right, 39.2% were in between the branches while 30.4% were anterior to the artery and 30.4% were posterior. On the left, 52% were in between the branches whereas 44% were posterior and 4% was anterior to the artery. Thus the position of the nerve in between the branches had the highest incidence while the anterior position had the lowest, the differences being statistically insignificant.