Persistent second cervical intersegmental artery diagnosed by MR angiography

Anastomosis between the external carotid and vertebral (VA) arteries is extremely rare. A well-recognized manifestation of such anastomosis is the Type 2 proatlantal artery, which commonly demonstrates anastomosis of the occipital artery with the VA at the level of the foramen magnum and is considered to represent a persistent first cervical intersegmental artery. Using magnetic resonance angiography, we observed anastomosis of the external carotid and VA at the level of C1 and C2 vertebrae without anastomosis of the occipital artery and diagnosed this vessel as a persistent second cervical intersegmental artery.