A Ruptured Anterior Communicating Artery Aneurysm with Infra-optic Course of the Anterior Cerebral Artery: A Case Report and a Short Review

Abstract

Infra-optic course of the anterior cerebral artery (IOA) is rare and approximately 55 cases of this anomaly have been described. We present a case of a ruptured anterior communicating artery (ACoA) aneurysm arising at the junction between the left IOA and the bilateral A2 segments, at which the right A1 segment was absent. One of the recurrent arteries of Heubner branched off directly from the aneurysmal dome, and was obstructed at aneurysmal neck clipping via an anterior interhemispheric (AIH) approach. In this report, accompanied anatomical variations and surgical approaches for ACoA aneurysms with IOA are reviewed. An IOA is frequently associated with other vascular anomalies, and the origin of functionally important recurrent arteries of Heubner is also variable. Preoperative accurate evaluation of vessel structures and the maximal exposure at surgery are very important. Pterional approach from the ipsilesional side is reportedly to be safe, but interhemispheric approach is also suggested to be effective as to full exposure to recognize the perianeurysmal anatomical structures including potential vessel anomalies.

Keywords: anterior communicating artery aneurysm; clipping; infra-optic course of anterior cerebral artery.

Fig. 1. Preoperative images. CT angiography in the posterior–anterior view reveals the low and early bifurcation of the anomalous ACA at the level of the ophthalmic artery (single white arrow), which turns upward, and an irregular-shaped aneurysm (double white arrow) arises at the junction between this anomalous ACA and bilateral A2 segment of ACAs (A). The left internal carotid angiography (horizontal inversion) shows two recurrent arteries of Heubner (black arrows) and a cortical artery which branch around the aneurysmal neck (B). Heavily T2-weighted magnetic resonance imaging (horizontal inversion) shows the IOA (single black arrowhead) branching from the left ICA (double black arrowheads) beneath the left optic nerve (C), which turns upward between the bilateral optic nerves (single white arrowhead) (D): an IOA aneurysm abuts on the superior part of the lamina terminalis (double white arrowheads) (E). ACA: anterior cerebral artery, CT: computed tomography, ICA: internal carotid artery, IOA: infra-optic course of ACA, L: left, R: right.

Fig. 2. Intraoperative view of the interhemispheric approach before (illustration; A) and after aneurysmal clipping (photograph; B), and postoperative magnetic resonance imaging (MRI; C). The left IOA (single arrow), left A2 segment with fenestration (double arrows), right A2 segment with fenestration (triple arrows), dura mater of the anterior cranial fossa (single black asterisk), optic chiasm (double black asterisks), the left optic nerve (triple black asterisks), a thrombus at the rupture site of the IOA aneurysm (white asterisk), a cortical artery adhering close to the rupture site (single white arrowhead), one of two RAHs branching from the aneurysm (double white arrowheads), and another RAH branching from the supraoptic portion of the IOA (triple white arrowheads) are illustrated (A). One of two RAHs branching from the aneurysm and the cortical artery adhering close to the rupture site are disconnected and the aneurysm is completely obliterated with multiple clipping (B): the marks in the figure are the same as in A. Postoperative diffusion-weighted MRI reveals acute infarction in the left caudate head and a part of the internal capsule and the putamen (C). IOA: infra-optic course of the anterior cerebral artery, L: left, R: right, RAHs: recurrent arteries of Heubner.