Bilateral occipital arteries arising from the thyrocervical trunks (ascending cervical artery-occipital artery anastomosis) diagnosed by magnetic resonance angiography.

We herein report a case of bilateral occipital arteries (OAs) arising from the thyrocervical trunks (TCTs). The patient was a 34-year-old woman with suspected basilar artery aneurysm underwent magnetic resonance (MR) angiography of the head and neck region using a 3-Tesla scanner. Cranial MR angiography revealed no aneurysm. Cervical MR angiography showed bilateral OAs arising from the TCTs. The extremely hyperplastic ascending cervical artery (ACA) arose from the transverse cervical artery, and continued to the OA, bilaterally. The OA usually arises from the proximal external carotid artery and runs posterosuperiorly; rarely, it arises from the internal carotid artery or the vertebral artery. The variation in our patient is regarded as bilateral ACA-OA anastomosis. Only one case of the unilateral type of this variation has been reported, having been diagnosed during dissection. Before cervical arterial intervention or head and neck surgery, identification of OA variation is important. During the interpretation of cervical MR angiography findings, careful observation of the origin and course of the OA is required.