Concurrence of iris aneurysms and cerebral hemorrhage in hypertensive rabbits.

The development of miliary aneurysms of the iris is associated with the high risk of cerebral hemorrhage in rabbits with renal hypertension. The high-risk group of hypertensive rabbits in this series was characterized by the formation of iris aneurysms, and this group developed a striking proportion of hemorrhagic strokes (42.5%). In the low-risk group of hypertensive rabbits that did not develop aneurysms of the iris, only a low proportion of cerebral hemorrhages were found (11%). The development of iris aneurysms in rabbits was directly proportional to increments in level of blood pressure, and their rate of formation was very rapid. The formation of miliary aneurysms of the circular artery of the iris in hypertensive rabbits is likely related to the common embryologic origin and the morphologic similarity between perforating arteries of the brain and the principal arterial vessel of the iris.