MEGALODOLICHOBASILARIS - THE EFFECT OF ATHEROSCLEROSIS ON A PREVIOUSLY WEAKENED ARTERIAL-WALL

The morphological findings of 2 basilar artery giant fusiform aneurysm s are presented. In one case (a 63-year-old man) the aneurysm was acci dentally found at autopsy. Its wall was mainly formed by fibrous tissu e without a smooth muscle layer and presented fragmented but still rec ognizable elastic lamina. In the media there were small well-formed bo ny spicules. In the other case (a 59-year-old man) the aneurysm had br oken causing subarachnoid hemorrhage. The wall showed a marked reducti on of smooth muscle cells and thinning and fragmentation of elastic la mina. A second sacciform aneurysm was present at the basilar tip. The review of the literature and the morphological findings of the 2 cases , characterized by abnormality of the portion of the basilar artery no t directly involved in the aneurysm wall, consisting of a diffuse defi cit of the tunica media and lamina elastica, might suggest that the fu siform aspect of the aneurysm may be the result of the degenerative ef fect of atherosclerosis on a congenital, structural or dysmetabolic, o r acquired, inflammatory, weakening of the arterial wall.