|Year : 2006 | Volume
| Issue : 3 | Page : 27-29
Infraoptic ACA with ICA bifurcation aneurysm - Anatomic case report
CE Deopujari, RM Shah, AB Kakani, VS Karmarkar, RC Luhana, Rajiv K
Department of Neurosurgery, Bombay Hospital Institute of Medical Science, Mumbai, India
C E Deopujari
126-B, MRC, Bombay Hospital, New Marine Lines, Mumbai-400020
Source of Support: None, Conflict of Interest: None
Variations of the anterior cerebral artery are well known. However, the infraoptic course of the ACA is a rare anomaly. We present a case report of a patient with such an anomaly with an associated ruptured ipsilateral ICA bifurcation aneurysm with its attendant management problems.
Keywords: anterior cerebral artery, optic nerve, internal carotid artery bifurcation, aneurysm, subarachnoid haemorrhage
|How to cite this article:|
Deopujari C E, Shah R M, Kakani A B, Karmarkar V S, Luhana R C, Rajiv. Infraoptic ACA with ICA bifurcation aneurysm - Anatomic case report. J Pediatr Neurosci 2006;1, Suppl S1:27-9
| » Introduction|| |
The literature is replete with reports of anatomic variations of the Anterior Cerebral Artery.,,, These anomalies, initially described in cadaveric studies and on angiography, are now being increasingly recognized owing to improved imaging. However, an infraoptic course of the Anterior Cerebral Artery is rare and has important surgical implications. We report a case with such an anomaly encountered during clipping of an acute ruptured ICA bifurcation aneurysm on the same side.
| » Case Report|| |
A fifteen year old girl presented with a two day history of sudden onset headaches, vomiting and transient loss of consciousness at that time. On examination, she was conscious, alert and did not have a focal neurological deficit. (WFNS Gr. 1)
A Computed Tomography of the brain revealed subarachnoid hemorrhage with blood predominantly in the right sylvian fissure and the basal cisterns. There was no suggestion of hydrocephalus. [Figure - 1] A four vessel Digital Subtraction Angiography showed a low bifurcation of the Internal Carotid Artery on the right side with a wide necked aneurysm at the bifurcation. We also noticed that the origin and course of the right Anterior Cerebral Artery was more horizontal than usual. The left A2 segment was filling from the right side, the left A1 being hypoplastic. The anterior choroidal artery was arising from the M1 segment of Middle Cerebral Artery. [Figure - 2], [Figure - 3]
She immediately underwent a right pterional craniotomy for clipping of the aneurysm. At surgery, it was noted that the Sylvian fissure was not well developed and was seen more posteriorly than usual. The proximal ICA was not visible, as the bifurcation was very low. Only the dome of the aneurysm was visible. The origin of right anterior choroidal artery from the M1 segment was confirmed. The right Anterior Cerebral Artery (A1 segment) was seen to be going under the right optic nerve. [Figure - 4]
After realizing that the bifurcation was right at the entry of the Internal Carotid Artery in the subarachnoid space, and the neck of the aneurysm was not well visualized, it was decided to expose Internal Carotid Artery in the neck. Proximal control of the ICA was obtained in the neck and temporary trapping (ACA & MCA) was used to dissect the neck of the aneurysm. The aneurysm was clipped using two Yasargil type clips, a side angled and a straight clip. The patient had an uneventful postoperative recovery.
| » Discussion|| |
Usually, the Anterior Cerebral Artery arises at the bifurcation of the Internal Carotid Artery at the medial end of the Sylvian fissure, lateral to the optic chiasm and below the anterior perforated substance. The A1 segment (pre communicating segment of the Anterior Cerebral Artery) then turns medially and somewhat anteriorly, passing over the chiasm to meet the Anterior Communicating Artery. Many variations of the anterior cerebral artery complex are described in the literature. Common anomalies are hypoplasia or aplasia of the A1 segment,,  duplication of the Anterior Communicating Artery, presence of three distal Anterior Cerebral Arteries,, an azygous distal Anterior Cerebral Artery. The presence of an infraoptic course of the A1 segment is rare however, and only thirty-two cases with this anomaly have been reported in the literature. This anomaly was first described by Robinson in 1959, during an anatomic dissection.
In all the cases of this anomaly described in the literature, the bifurcation of the Internal Carotid Artery is low, almost at the level of the origin of the Ophthalmic Artery just as the Internal Carotid Artery becomes intradural. The Middle Cerebral Artery appears to be a direct continuation of the Internal Carotid Artery and the A1 segment passes below the ipsilateral optic nerve. The further course of this artery is variable.
There are many theories in the literature regarding the embryogenesis of this anomalous vessel.,, It has been variously described as simply the abnormal course of the A1 or as a persistent inutero communication between the primitive dorsal and ventral ophthalmic arteries. Some postulate it to be an anastomosis between the branches of the primitive Maxillary and olfactory arteries, or as the persistence of the prechiasmal arterial anastomosis. Still others think of it as an anastomosis between the Anterior Cerebral Artery and the Internal Carotid Artery.
This anomaly, like other variations in the circle of Willis, is associated with increase in the incidence of aneurysms. The most common site of such aneurysms is at the Anterior Cerebral Artery-Anterior Communicating Artery complex. Aneurysms at other sites including the Middle Cerebral Artery , the infraoptic part of the A1 segment itself, Internal Cerebral Artery-Ophthalmic aneurysm have all been reported. Apart from aneurysms, other vascular anomalies including a fused pericallosal artery, agenesis of the contra lateral Internal Cerebral Artery, origin of the Middle Cerebral Artery from the Basilar artery, Coarctation of aorta, Moya-Moya disease have been described.
The cases reported in the literature have been identified during anatomic dissections, conventional angiography, Magnetic Resonance Angiography, during surgery and during autopsy. Though rare, preoperative recognition of this anomalous vessel and other anomalies is crucial for proper surgical planning. The characteristic appearances on conventional angiography have been described. There is an apparently low bifurcation of the Internal Carotid Artery and the Anterior Cerebral Artery takes a more horizontal course and turns medially. In the midline, it turns superiorly to join the Anterior Communicating Artery. A MR angiography shows similar findings as the conventional DSA, but reviewing the source images or obtaining high spatial resolution images of the suprasellar region provides additional information regarding the relationship of the Anterior Cerebral Artery to the optic chiasm.
Clinically, it is important to recognize this anomaly because of its association with other vascular anomalies; to ensure proper preoperative planning, for proximal control of the Internal Carotid Artery while clipping the aneurysm. Recognition of this anomaly avoids unnecessary dissection and possible damage to the vessels, perforators or the optic apparatus during the surgery.
| » Conclusion|| |
Although anomalies of the Internal Carotid Artery and its branches are known, an infraoptic course of the Anterior Cerebral Artery associated with an ipsilateral Internal Carotid Artery bifurcation aneurysm is not reported in English literature. We have presented the anatomy and the possible attendant complications with such an anomaly and the importance of recognizing this rare entity.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]