The Thyroid Gland: A Revision Study on Its Vascularization and Surgical Implications

Abstract

Background: The "classic" thyroid gland arterial vascularization takes into account two superior thyroid arteries (STA), two inferior thyroid arteries (ITA) and, occasionally, a thyroid ima artery (TIMA). The present review focuses on exploring the available data concerning thyroid gland arterial vascularization and its variations. Methods: Here, we analysed 49 articles from the last century, ranging from case reports to reviews concerning cadaver dissection classes, surgical intervention, and non-invasive techniques as well. Results: The harvested data clearly highlighted that: (i) the STA originates predominantly from the external carotid artery; (ii) the ITA is a branch of the thyrocervical trunk; and (iii) the TIMA is a very uncommon variant predominantly occurring to compensate for ITA absence. Conclusion: A systematic review of a highly vascularized organ is of great relevance during surgical intervention and, thus, the knowledge of normal anatomy and its modification is essential both for fact-finding and in surgery.

Keywords: inferior thyroid artery; superior thyroid artery; thyroid arteries variations; thyroid gland; thyroid ima artery.

Figure 1

STA different origin as reported and modified by Natsis and colleagues. In type I STA origins as separate branch at different levels. In type II STA is a part of thyrolingual trunk or thyrolinguofacial trunk. The image has been modified as previously reported [7]. Superior thyroid artery origin classification. Type I, separate branches, I_EC: STA as separate branch from ECA, I_CB: STA as separate branch from CB, I_CC: STA as separate branch from CCA. Type II_TL branching patterns, II_TL-EC: thyrolingual trunk from ECA, II_TL-CB: thyrolingual trunk from CB, _IITL-CC: thyrolingual trunk from CCA. Type II_LF branching patterns, II_LF-EC: linguofacial trunk and STA from ECA, II_LF-CB: linguofacial trunk from ECA and STA at the level of CB, II_LF-CC: linguofacial trunk from ECA and STA from CCA. Type II_TLF branching pattern, thyrolinguofacial trunk from ECA.

Figure 2

TIMA (highlighted by * asterisk) as reported and modified by Moriggl and colleagues. It is worth noticing the artery calibre [46]. 1, aortic arch; 2, common origin of innominate artery and left common carotid artery; 3, innominate artery; 4, common carotid artery; 5, subclavian artery; 6, internal thoracic artery.