Anatomical Variations of the Ansa Cervicalis in Thais

Abstract

The aim of this study was to examine the variation of ansa cervicalis in Thais in terms of its origin, formation and relation to the great vessels of the neck. Anatomical dissections were examined bilaterally in 108 cervical plexuses of Thai cadavers ranging in age from 34 to 87 years. There were 57 male and 51 female cervical plexuses. The ansa cervicalis which consists the first to third cervical ventral rami (C1-C3), is formed by the junction of the superior and inferior roots. Its anatomical course and morphology are complicated by the variable lengths, origins, and relations with the great vessels of the neck. Twenty types of ansa cervicalis were classified into 5 different groups according to the length of ansa loop as compared with the level of cricoid cartilage and the relation of the inferior root of the ansa to the internal jugular vein. Depending on the origins of the inferior and superior roots, each group consisted of various types. Group I and II had long ansa loops with the inferior root lying lateral to the internal jugular vein in group I, and nedial to the vein in group II. Similarly, group III and IV had short loops of the ansa with the inferior root lying lateral to the internal jugular vein in group III, and medial to the vein in group IV. However, group V was not related to the criteria. It was suggested that the majority of ansa cervicalis were found to be group IV and group I. The variation of ansa cervicalis patterns occurred in both sides. This was not statistically different with regard to either gender of side. The results of this study provide additional information and new insights into the variation of the ansa cervicalis which may have useful applications in laryngeal reinnervation surgery and anrsthesia.