The Artery of Foramen Rotundum is typically a small connection between the external carotid artery (distal internal maxillary artery) and the internal carotid artery (inferolateral trunk). Of course, the branch can become enlarged in cases of ICA or ECA occlusion.

Here is a VERY large Artery of Foramen Rotundum in a patient with a left frontal AVM. The patient was treated for a right paraophthalmic ICA flow-related aneurysm on the right. This is the right external carotid artery angiogram showing an unusually robust Artery of Foramen Rotundum.

Video Below:

Shown below is an enlarged Artery of Foramen Rotundum in a patient with cervical squamous cell carcinoma following prior proximal ECA takedown. In this case, arterial flow is from the ICA to the ECA through the Artery of Foramen Rotundum.

The unlabeled version of the Artery of Foramen Rotundum above and the labeled version below:

In other cases, flow may be prominent from the ECA to the ICA and can be a potentially dangerous anastomosis during embolization of the external carotid artery.