Ectasia of the basilar artery with special reference to possible pathogenesis.

The pattern of reticular fibers and some other microscopic features of all the major intracranial arteries were examined in two patients with ectatic basilar artery. In order to make a comparison possible the major cerebral arteries of 105 individuals with advanced atherosclerosis were also investigated. This series includes 40 patients with berry aneurysms. Defects in the elastic lamina and reticular fiber deficiency in the muscular layer were common pathologic features in patients with ectatic basilar artery and in those with berry aneurysm. In the ectatic basilar arteries these alterations were much more conspicuous. In the other atherosclerotic arteries sampled from patients having no malformations, the density of reticular fibers in the media was preserved. It is concluded that atherosclerosis may not have a basic role in the pathogenesis of arterial ectasias, but the severe reticular fiber deficiency in the media associated with extensive defects in the elastic lamina forms the morphologic basis of ectasias. Furthermore, the arterial ectasias and berry aneurysms are most probably different manifestations of the same underlying disorder.