A thyroidea ima artery variation providing collateral circulation to the mediastinum

Abstract

The thyroidea ima artery (TIA) is a highly variable arterial deviation of the blood supply to the thyroid gland with critical implications for surgical neck procedures such as tracheostomy. Though relatively common in the population at large (~ 4%), most TIA variations are related to the origin of the artery and whether it emerges from the common sites of the brachiocephalic trunk, aortic arch, and right common carotid artery, or another more unique vessel-as opposed to its dispersion pattern. TIA variants generally supply the thyroid gland, occasionally co-occurring with absent thyroid arteries. Here, we report on a unique case of a four-pronged variation of the TIA discovered during an anatomy laboratory dissection of first-year medical students. This variant originated from the brachiocephalic trunk and had three branches terminating in the thyroid gland and a fourth branch traveling into the thorax to provide accessory circulation in the mediastinum. Specifically, small arterial branches from the inferior TIA branch supplied the anterior pericardium and surrounding adipose tissue, in addition to normal pericardiacophrenic circulation. We discuss the potential embryological and clinical relevance of this unique variation and voice further support for imaging as a requirement before surgical neck procedures to prevent catastrophic bleeding in the event of a TIA variant.

Keywords: Anatomical variation; Dissection case report; Pericardiacophrenic collateral circulation; Pericardium; Thyroidea ima.