Anatomical variations in the origin of the superior thyroid artery

Abstract

Superior thyroid artery (STA) is first and lowest branch of external carotid artery (ECA) and it supplies thyroid, parathyroid, upper larynx and neck region. The STA origins either from ECA, common carotid artery (CCA) or its bifurcation level. Various researchers have reported differences in its origin. The STA commencing from the ECA is comparatively more in Indian and Ethiopian but its derivation from CCA bifurcation point is more in Turkey and Korean. Origin of STA in relative to upper border of thyroid cartilage is used as a landmark. The CCA bifurcates into external and internal carotid arteries at same level and occasionally bifurcates at a higher or lower level than its usual site. Origin of STA from CCA is associated with high bifurcation and its origin from the ECA is related with the low CCA division. Comparatively STA origin from CCA or its bifurcation level is more on right side. The CCA developed from third aortic arch and any alteration in development of aortic arches might also contribute to these variations. The STA is an artery of abundant clinical significance and it is recommended to do detailed study of its origin, course, branches, size, and positional relation with the external laryngeal nerve, hyoid bone and thyroid cartilage. Understanding of these variations is immense importance in academic and clinical arena for planning and performing surgical procedures in neck region.