OBJECTIVE: To describe the anatomic relationship of the recurrent laryngeal nerve and the inferior thyroid artery in adult cadavers in the Philippines and to compare the proportions of these anatomic relationships with those reported in the foreign literature.

METHODS:
Design: Descriptive, cross-sectional
Setting: University of the Philippines College of Medicine Anatomy Laboratory
Subjects: Fifty-four (54) preserved cadavers (108 sides) dissected within a period from June 2008 to Aug 2010. The anatomy and position of both the right and the left recurrent laryngeal nerves (RLN) and inferior thyroid arteries (ITA) were noted. The RLN was further classified into two variations: non-branching or branching prior to insertion at the cricothyroid joint under the inferior constrictor muscle. The ITA was also classified into non-branching and branching. The results were compared to two foreign studies using a Z-test for two proportions.

RESULTS: Fifty four (54) cadavers (108 sides) were dissected. Among the cadavers, both the recurrent laryngeal nerves and inferior thyroid arteries had a maximum of two branches although both the RLNs and ITAs for both the right and left sides were mostly non-branching. The right side of one cadaver was noted to have both a branching RLN and a branching ITA. There were no non-recurrent laryngeal nerves seen among the 54 cadavers. For both left and right sides, the RLN was mostly dorsal to the ITA. Branching RLNs was mostly dorsal to a non-branching ITAs. Most of the non-branching RLNs were dorsal to the ITAs. Non-branching RLNs were usually dorsal to the ITA. The local patterns of the course of the RLN in relation to the ITA approximates those of Chinese where there is predominance of the RLN dorsal to the ITA but differs from those of Brazilians where the RLN is usually between ITA branches.

CONCLUSION: There are multiple anatomical variations regarding the relationship of the RLN and the ITA. The anatomic variation among Asians may be different from Brazilians. The surgeon's knowledge of the possible various configurations of the RLN and ITA should be able to help in identification and preservation of the RLN and prevention of complications in thyroid surgery.