NBME 21 Answers ↦
(36.2 difficulty score)
A 55-year-old woman with a benign nodule in ...
Ooh that is tricky tricky. In the question stem they said they already ligated that one ("a branch of the brachiocephalic trunk") and were wondering what else needs to be ligated in addition to that. Therefore the answer is the superior thyroid artery, which is coming from the external carotid. I don't think I knew any of this when I did the question though, cause I had to google all this just now.
In the stem they said they ligated a branch of the thyrocervical trunk, not the brachiocephalic. According to Wiki, the thyroid ima artery (which does arise from the brachiocephalic trunk) is only present in about 3-10% of the population. Therefore, while technically this answer could be correct, external carotid is "more correct".