The microsurgical anatomy of the premamillary artery

The 50 premamillary arteries (PremA), arising from 39 posterior communicating arteries (PCoA), were examined in injected human brains. The PremA, which commonly was single (71.8%) and less frequently double (28.2%), more often arose from the PCoA (97.4% ) than from the posterior cerebralartery (PCA) (2.6%). The PremA ranged between 280 and 780 microm in diameter. It gave off side branches to the hypothalamus (23.1%), optic tract (10.2%), mamillary body (17.9%) and the crus cerebri (35.9%). The anastomoses involving the extracerebral segment of the PremA were present in 35.9% of the cases. They varied in caliber from 50 to 230 microm. The intracerebral segment of the PremA ranged from 280 to 490 microm in diameter. Our study gives a precise anatomic basis for safer operations on the aneurysms of the posterior communicating artery and adjacent vessels.