Anatomical bases for surgical approach to the initial segment of the anterior cerebral artery. Microanatomy of Heubner's artery and perforating branches of the anterior cerebral artery.

Both the Heubner's artery and the perforating branches of the anterior cerebral artery (ACA) were present in all thirty-three examined brains. Heubner's arteries varied in number from 1 to 3. They originated from the distal (A2) segment of the ACA in 34% of the cases, from the proximal (A1) segment of the ACA in 17%, at the level of the anterior communicating artery in 21%, from the fenestration of the ACA in 8%, and in all the other cases (20%) from the azygous anterior cerebral artery, accessory middle cerebral artery, frontopolar artery and, finally, by the common stem with the medial orbitofrontal artery. Heubner's artery most commonly terminated dorsal and lateral to the carotid bifurcation, at an average distance of 4.8 mm. The mean diameter of Heubner's artery was 662 microns, that of its extracerebral collateral branches 205 microns, of the terminal branches 462 microns, and of the intracerebral segments 354 microns. Perforating branches varied in number from 1 to 12 with an average of 6.6. The majority of the branches originated from the initial 6.1 mm of the A1 segment. These vessels terminated close to the carotid bifurcation, at an average distance of 3.8 mm. All the perforating branches were divided into small (average 122 microns in diameter) and large (average 325 microns). The mean diameter of intracerebral segments was 276 microns, and that of terminal branches 259 microns. It was concluded that the anatomical characteristics of both the recurrent artery and the perforating branches can be of a great significance in cerebrovascular diseases.