Bilateral internal carotid to anterior cerebral artery anastomosis with anterior communicating artery aneurysm: technical case report.

OBJECTIVE AND IMPORTANCE: The present case report is the first one to report a bilateral anastomotic artery between the internal carotid artery and the anterior communicating artery in the presence of a bilateral A1 segment, fenestrated anterior communicating artery (AComA), and associated aneurysm of the AComA, which was discovered by magnetic resonance angiography and treated surgically.

CLINICAL PRESENTATION: A 38-year-old man who was previously in good health experienced a sudden onset of nuchal headache, vomiting, and confusion. Computed tomography revealed a subarachnoid hemorrhage. Magnetic resonance angiography and four-vessel angiography documented an aneurysm of the AComA and two anastomotic vessels of common origin with the ophthalmic artery, between the internal carotid artery and AComA.

INTERVENTION: A fenestrated clip, introduced by a left pterional craniotomy, leaving in its loop the left A1 segment, sparing the perforating and hypothalamic arteries, excluded the aneurysm.

CONCLUSION: The postoperative course was uneventful, with complete recovery. Follow-up angiograms documented the successful exclusion of the aneurysm. Defining this particular internal carotid-anterior cerebral artery anastomosis as an infraoptic anterior cerebral artery is not appropriate because there is already an A1 segment in its habitual localization. Therefore, it is also thought that, embryologically, this anomaly is not a misplaced A1 segment but the persistence of an embryological vessel such as the variation of the primitive prechiasmatic arterial anastomosis. The favorable outcome for our patient suggests that surgical treatment may be appropriate for many patients with this anomaly because it provides a complete and definitive occlusion of the aneurysm.