Development of bilateral collateral circulation after fracture of the axis.

The authors present a patient with chronic myelopathy after atlanto-axial fracture and vertebral artery occlusion treated by removal of the arch of the atlas. The natural arterial collaterals and their role are discussed. It is suggested that the knowledge of all the anastomoses is very important to avoid damage of blood flow during surgery. Fenestration of the vertebral artery causing by kinking is to be seen--a rare form of pathological collaterals.