Lack of inferior thyroid artery

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

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.

Arterial supply to the thyroid gland and the relationship between the recurrent laryngeal nerve and the inferior thyroid artery in human fetal cadavers

The aim of this study was to identify the arterial supply to the thyroid gland and the relationship between the inferior thyroid artery (ITA) and the recurrent laryngeal nerve (RLN) in fetal cadavers using anatomical dissection. The anterior necks of 200 fetuses were dissected. The origins of the superior thyroid artery (STA) and the ITA and location of the ITA in relation to the entrance of the thyroid lobe were examined. The relationship between the ITA and the RLN was determined. The origins of the STA were classified as: external carotid artery, common carotid artery (CCA), and the thyrolingual trunk. The origins of the ITA were the thyrocervical trunk and the CCA. The ITA was absent on the left side in two cases. The relationship of the RLN to the ITA fell into seven different types. Type 1: the RLN lay posterior to the artery; right (42.5%), left (65%). Type 2: the RLN lay anterior to the artery; right (40.5%), left (22.5%). Type 3: the RLN lay parallel to the artery; right (11.5%), left (7%). Type 4: the RLN lay between the two branches of the artery; right (1%), left (3.5%). Type 5: The extralaryngeal branch of the RLN was detected before it crossed the ITA; right (4.5%), left (0%). Type 6: the ITA lay between the two branches of the RLN; right (0%), left (0.5%). Type 7: the branches of the RLN lay among the branches of the ITA; right (0%), left (0.5%). The results from this study would be useful in future thyroid surgeries.