Connect one anterior cerebral artery with the other, within and along the floor of the cerebral vault.
The local anatomy of the anterior communicating artery aneurysms is very complex and there are 13 arteries in them.
ACCEPTED ANATOMIC STUDIES have indicated that the anterior communicating artery has no branches or a single variable branch 1) 2) 3) During microsurgery in this region, Yasargil noted and spared several branches of the anterior communicating artery 4).
The anatomy of the anterior communicating artery complex plays a critical role in surgical treatment of anterior circulation aneurysms. Female subjects have a higher incidence of variations in the anterior communicating artery complex. There is a higher incidence of anterior communicating artery aplasia among women 5).
The microvascular relationships important to surgery of aneurysms in the anterior communicating region were defined in 50 cadaver brains. The recurrent artery of Heubner was frequently exposed before the A-1 segment in defining the neck on anterior cerebral aneurysms because it commonly courses anterior to A-1. It arose from the A-2 segment of the anterior cerebral artery (ACA) in 78% and most commonly terminated in the area of the anterior perforated substance, and lateral to it in the Sylvian fissure. The anterior communicating artery (ACoA) frequently gave rise to perforating arteries which terminated in the superior surface of the optic chiasm and above the chiasm in the anterior hypothalamus. This finding contrasts with previous reports that no perforating branches arise from the communicating artery. The proximal half of the A=1 segment was a richer source of perforating arteries than the distal half. The A-1 branches most commonly terminated in the anterior perforated substance, the optic chiasm, and the region of the optic tract. The ACoA increased in size as the difference in the diameter between the right and left A-1 segments increased. Frequent variants such as double or triple ACoA's, triple A-2 segments, and duplication of the A-1 segments were encountered. The clinical consequences of occlusion of the recurrent artery and of the perforators from the ACoA and medial and lateral segment of A-1 are reviewed 6).
The anterior communicating artery was studied with the operating microscope in 10 autopsy cases. This vessel was present in all cases with reduplication in three. Arterial diameter ranged from 0.8 to 2.3 mm, with lengths of 5 to 10 mm. Branches of the anterior communicating artery were found in every case (range 3-13, average 5.4). Most branches were small (50-250 mu), but at least one large branch (250-1000 mu) was invariably present. Small ventral branches ramified on the optic chiasm. Small and large dorsal branches distributed themselves to lamina terminalis, hypothalamus, parolfactory areas, columns of fornix, and corpus callosum.
The regularity and destinations of these branches suggest an important physiologic function. Subarachnoid bleeding from an aneurysm in this location could produce mechanical disruption or vasospasm of these branches, and thus could account for serious disturbances of function in the territory of supply. Obliteration of the anterior communicating artery, once advocated in the therapy of anterior communicating artery aneurysms, probably leads to adverse psycho-organic syndromes by interruption of these important perforant branches. Careful sparing of these branches is recommended during aneurysm surgery 7).
The anterior communicating artery (ACoA) and its branches were examined in 22 human brains after injecting Indian ink or methylmethacrylate. The ACoA branches were divided into the small and the large. Small branches were from 1 to 5 in number (mean 2), and from 70 to 270 microns in diameter (mean 151 microns). Seventy-six percent of the branches originated directly from the ACoA. They tended to arise closer to the left than to the right anterior cerebral artery. Fourteen percent of them arose from the junctional site of the ACoA with the anterior cerebral arteries, and 10% from the site of origin of the subcallosal artery. Large branches were identified as the median artery of the corpus callosum, and the subcallosal artery, respectively. The former vessel was present in 9% of the patients, and the latter in 91%. The subcallosal artery was from 320 to 640 microns in size (mean 486 microns). It tended to arise from the middle of the ACoA. In spite of the very frequent anastomoses involving the ACoA branches, care must be taken to avoid injury to these important vessels during operations of the ACoA aneurysms 8).
The microsurgical anatomy of these branches was studied on 60 fixed human brains, with special attention to their number, caliber, and vascular territory. The direction of the branches was evaluated, measuring the angle formed by them with the postcommunicating segment of the anterior cerebral artery 9).
In 30 cadaver brains, the ACoA and its branches were examined under magnification using a surgical microscope.
The ACoA was evident in all specimens and had variations consisting of plexiform (33%), dimple (33%), fenestration (21%), duplication (18%), string (18%), fusion (12%), median artery of the corpus callosum (6%), and azygous anterior cerebral artery (3%). The perforating branches were also observed in all cadaver brains. They were classified into subcallosal, hypothalamic, and chiasmatic branches according to their vascular territories. The subcallosal branch, usually single and the largest, supplied the bilateral subcallosal areas, branching off to the hypothalamic area. The hypothalamic branches, multiple and of small caliber, terminated in the hypothalamic area.
The incidence of anomalous ACoA was higher than has been previously reported, and any segment of the anomalous ACoA may have perforating branches regardless of diameter.
Despite the variable anatomy of the anterior communicating artery (AcoA) complex, three main perforating branches can be typically identified the largest of which being the subcallosal artery (ScA).
This artery is very important because it feeds bilateral subcallosal areas branching to the hypothalamic area 10).