Microvascular anatomy of the anterior surface of the medulla oblongata and olive.

The arterial supply and the microanatomy of the anterior surface of the medulla oblongata and olive were studied in 11 cadaveric specimens, with investigation of the size, course, and length of the arteries. Two distinct anatomical entities divide the vascular supply in this region: 1) the pyramid, which is the anterior surface of the medulla; and 2) the olive, which is adjacent to the lateral aspect of the pyramid. Primary vascularization of the pyramid was via small branches of the anterior spinal artery, a branch of the vertebral artery. Minute perforators from the anterior spinal artery were found in all specimens. Arterial supply to the olive varied by location: its anterior aspect was primarily supplied by the anterior spinal artery; the upper portion of the posterior aspect of the olive was supplied by the vertebral artery, the anterior inferior cerebellar artery, and the basilar artery; and the middle and lower portions of the posterior aspect were fed by the vertebral artery and posterior inferior cerebellar artery. These arteries supplied the medulla through the small branches directed toward the olive. The authors observed a wide anastomotic net connecting the small arteries in this area. These patterns of microvascular supply of the pyramid and olive may deepen the understanding of clinical and pathological conditions resulting from arterial occlusion. The existence of an anastomotic net may account for the rare incidence of medullary infarction in the olive region.