Absence of three regular thyroid arteries replaced by an unusual lowest thyroid artery (A. thyroidea ima): a case report.

During routine dissection of an 89-year-old female donor both inferior thyroid aa. as well as the left superior thyroid a. were found to be absent, whereas the right superior thyroid a. came from the right common carotid. A large lowest thyroid a. rose from the left internal thoracic a. at the level of the first intercostal space. Up to this point the internal thoracic a. was of immense diameter, almost reaching that of the lateral part of the subclavian. The lowest thyroid a. ascended in an oblique and sigmoid course to the thyroid gland. Slightly left of the median line it bifurcated into two branches. Both had a winding course in front of the trachea before entering the base of the thyroid gland. Other arterial variations of minor significance were also observed in this unique case. The clinical impact lies in the localisation, course and size of the lowest thyroid a. reported.