C2

	Case #1a Lateral left vertebral angiogram, early The left common carotid artery is occluded in this patient. Blood flow from the left vertebral artery traverses an enlarged C2 muscular branch which anastomoses with the occipital artery. The occipital artery then retrograde fills the external carotid. The internal maxillary branch of the external carotid anastomoses with the ophthalmic artery, which reconstitutes the cavernous internal carotid (Case #1b).
	Case #1b Lateral left vertebral angiogram, late Later image in the same run as above. This better demonstrates the internal maxillary artery to ophthalmic artery connection with retrograde filling of the internal carotid.
	Case #1c AP left vertebral angiogram The C2 muscular branch to occipital collateral is again demonstrated. This can be confused with primitive hypoglossal artery or proatlantal intersegmental artery.