Infraoptic course of the anterior cerebral artery associated with an anterior communicating artery aneurysm: Anatomic case report and embryological considerations

OBJECTIVE AND IMPORTANCE: An infraoptic course of the proximal anterior cer ebral artery is a rare anomaly that has been reported in 32 cases to date, often in association with cerebral aneurysms. This anomaly represents a mal development in the embryogenesis of the anterior circle of Willis, resultin g from the persistence of the primitive prechiasmal arterial anastomosis or an error in the development of the definitive ophthalmic artery (OphA). Th e case of a patient with a ruptured middle cerebral artery aneurysm and an anterior communicating artery aneurysm associated with this anomaly is desc ribed, and the anatomic features are outlined. CLINICAL PRESENTATION: A 30-year-old male patient with a right temporal hem atoma and subarachnoid hemorrhage was admitted to our department 4 days aft er the hemorrhaging episode, with normal neurological examination results. Angiography revealed a right middle cerebral artery aneurysm and an anterio r communicating artery aneurysm with an anomalous precommunicating tract. INTERVENTION: The patient was surgically treated 14 days after the hemorrha ging episode, through a right frontopterional craniotomy; both aneurysms we re excluded by clipping. The anomalous infraoptic proximal tract of the ant erior cerebral artery was well documented, with its origin adjacent to the OphA. The patient remained neurologically intact after surgery and was disc harged 8 days later. CONCLUSION: The anomalous infraoptic course of the proximal anterior cerebr al artery was associated with a low bifurcation of the ipsilateral internal carotid artery and the absence of the contralateral precommunicating tract in this patient. The strict anatomic relationship with the origin of the O phA suggests an error in the development of the definitive OphA, with persi stence of an anastomotic loop between the primitive dorsal and ventral OphA s. It is concluded that, for aneurysm surgery, careful angiographic evaluat ion and an understanding of the neurovascular relationships in the circle o f Willis are essential for a successful postoperative course, especially wh en very rare vascular anomalies are treated.