Thyroidea ima — when the inferior thyroid artery arises proximal to its expected thyrocervical trunk origin, whether from the aortic arch or from the subclavian artery, that's what you call it. In this case, the thyroidea ima artery arises from the first part of the right subclavian artery next to the origin of the right common carotid artery (black arrowheads).
The right vertebral artery is also demonstrated (red arrows).
Case Discussion
The thyroidea ima artery arises from the brachiocephalic trunk and ascends in front of the trachea to the lower part of the thyroid gland, which it supplies. It is only present in approximately 3-10% of the population. It varies greatly in size and appears to compensate for deficiency or absence of one of the other thyroid vessels. Occasionally, it arises from the aorta, the right common carotid, the subclavian or the internal thoracic artery.
Due to its location and infrequent presence, it can cause problems for physicians performing a tracheostomy or a thyroidectomy.