Presentation
Known nasopharyngeal squamous cell carcinoma.
Patient Data
Incidentally noted is a carotid-basilar anastomotic vessel arising from the left external carotid artery at the level of the 2nd cervical vertebral body (C2). The vessel courses dorsally and joins the left vertebral artery in the suboccipital space, with the artery then entering the foramen magnum.
There is a heterogeneous solid right nasopharyngeal soft tissue mass partially filling the nasopharyngeal and oropharyngeal airway and slightly crossing the midline leftward. This is consistent with the patient's known squamous cell carcinoma.
There is a persistent carotid-vertebrobasilar anastomosis arising from the left external carotid artery consistent with a type 2 proatlantal intersegmental artery.
The aberrant artery arises from the left external carotid artery at the level of C2, with the vessel then coursing dorsally and joining with the left horizontal vertebral artery in the suboccipital space, which then enters the foramen magnum (yellow arrows).
The left intracranial vertebral artery is also depicted (blue arrow).
Case Discussion
65-year-old female with history of right nasopharyngeal squamous cell carcinoma, with an incidental finding of a persistent left proatlantal intersegmental artery.
Two types of proatlantal intersegmental arteries have been described, both arising from the carotid artery and entering the foramen magnum. Type 1 proatlantal artery arises from the internal carotid artery and ascends to the level of the occipitoatlantal space without passing through the transverse foramen of any cervical vertebra. The artery takes a dorsal course cephalad to the transverse process of C1 and then travels rostrally to enter the foramen magnum. Type 2 proatlantal artery arises from the external carotid (as in this case).
The proatlantal intersegmental artery should be differentiated from a more frequently seen persistent hypoglossal artery, another type of persistent carotid-vertebrobasilar anastomoses.
Unable to process the form. Check for errors and try again.