A Ruptured Aneurysm at the Infraoptic Azygous Anterior Cerebral Artery with the Contralateral Internal Carotid Artery Agenesis Treated by Y-stent Assisted Coil Embolization

Abstract

Infraoptic anterior cerebral artery (ACA) is an extremely rare congenital anomaly. This anomalous artery usually arises from the intradural internal carotid artery (ICA) near the level of the ophthalmic artery (OA) or rarely from the extradural ICA. This anomaly frequently harbors a cerebral aneurysm, and may involve other coexisting vascular anomalies. In the case of this anomaly, surgical treatment of the aneurysm at the proximal ACA or anterior communicating artery (ACoA) may sometimes be difficult, because the veiled proximal ACA by the optic nerve would make proximal control inconvenient and the vertical midline segment of the proximal ACA would frequently form a superiorly directing aneurysm with a relatively high position. We report on an extremely rare case of a ruptured aneurysm at the infraoptic azygous ACA, possibly having an extradural origin, accompanied by contralateral ICA agenesis, and also introduce a feasible method for treatment by Y-stent assisted coil embolization.

Keywords: Anterior cerebral artery; Infraoptic; Y-stent.

Fig. 1

Initial brain computed tomography (CT) scan reveals a diffuse and thick subarachnoid hemorrhage in the basal cisterns, the bilateral Sylvian fissures, and the anterior interhemispheric fissure.

Fig. 2

Anterior-posterior view (A) and lateral view (B) of the right internal carotid angiogram shows an aneurysm (black arrows) at the terminal of the infraoptic azygous portion of the anterior cerebral artery (ACA) (white arrows). This anomalous artery originates from the internal cerebral artery proximal to the ophthalmic artery (white arrowheads). The bilateral recurrent arteries of Heubner (black arrowheads) arise from the vertical portion of the azygous ACA in the midline, and course laterally into the anterior perforated substances. Left carotid angiogram (C) shows agenesis of the ICA. The left middle cerebral artery is visualized on the vertebral angiogram (D) via the prominent posterior communicating artery. Working projection view (E) shows a bilobulated aneurysm with a broad neck slightly incorporating the bilateral distal ACA branches.

Fig. 3

Angiogram after coil embolization shows complete occlusion of the aneurysm. Proximal and distal markers (black arrowheads) indicate partially overlapping double stents in Y-configuration protecting the distal ACA branches.

Fig. 4

Vasospasm (black arrowheads) is prominent at the ACA branches distal to the stents on the follow-up angiogram.

Fig. 5

Anatomical locations of the infraoptic azygous ACA (white arrows) with stent, optic nerve (black arrows), optic canal (black arrowheads), anterior clinoid process (black asterisks), and ophthalmic artery (white arrowheads) are shown in axial (brain setting, A) and coronal views (bone setting, B) of follow-up brain CT, and serial coronal reconstructions (C) of MR angiography source images from anterior to posterior. Note that the stents are replaced by metal artifacts (white asterisks) on MR images.