Abstract
Occipitovertebral anastomosis was examined in 22 cadavers after injection of polyvinyl acetate through the ipsilateral common carotid artery to reveal the precise morphology. There were anastomotic channels in 14 cadavers. The anastomotic forms of the channels were classified into two types. Type 1 had a direct anastomosis (8 cadavers), and type 2 had net-like anastomoses (6 cadavers) . The branching portion from the occipital artery was 7.9 mm (mean) posteromedial from the mastoid process, and the joining portion to the vertebral artery was 7.1 mm (mean) lateral from the posterior atlanto-occipital membrane. The inside diameter of the anastomotic channels, measured with the help of an image analyzer, was 0.36mm (mean) . As the occipitovertebral anastomosis occurs frequently, a careful intravascular operation through the occipital artery should be performed. Neurosurgeons must always keep in mind that direct anastomosis is more frequent than net-like anastomosis in sub-occipital muscles.
