Occipital artery arising from the cervical internal carotid artery at the level of the C2 vertebral body: three cases detected utilizing magnetic resonance angiography.

We incidentally observed the occipital artery (OA) arising from the cervical internal carotid artery (ICA) at the level of the C2 vertebral body on magnetic resonance (MR) angiography in three patients. In the rare case in which the OA arises from the ICA, it is generally at its origin. The OA arises from the cervical ICA when all but the distal part of the anastomosis of the primitive proatlantal artery between the ICA and vertebral artery persists. Careful review of MR angiographic images is important to detect rare arterial variations, and both partial maximum-intensity-projection images and source images aid their identification on MR angiography.