An animal model of cerebral aneurysms.

Cerebral aneurysms were induced experimentally in rats by ligating the common carotid artery on one side, making the animals hypertensive, and feeding them the lathyrogen beta-aminopropionitrile. On analysis of this experimental model, haemodynamic stress, hypertension and metabolic disorder of the connective tissue proved to be of primary importance as aetiological factors in the development of cerebral aneurysms. The experimentally induced cerebral aneurysms resemble those in man both in location and in microscopic structure; they can thus be regarded as a good model for the study of the pathogenesis of cerebral aneurysms. The initial changes leading to the formation of aneurysms occurred on the distal side of major artery branches adjacent to the apex, but distal to the intimal pad. It is proposed that degenerative changes in the internal elastic lamina and muscle cells of the media, caused by haemodynamic stress at vessel branches and intimal pads, are the basis for aneurysm formation.